mm/shmem.c

   1 /*
   2  * Resizable virtual memory filesystem for Linux.
   3  *
   4  * Copyright (C) 2000 Linus Torvalds.
   5  *               2000 Transmeta Corp.
   6  *               2000-2001 Christoph Rohland
   7  *               2000-2001 SAP AG
   8  *               2002 Red Hat Inc.
   9  * Copyright (C) 2002-2011 Hugh Dickins.
  10  * Copyright (C) 2011 Google Inc.
  11  * Copyright (C) 2002-2005 VERITAS Software Corporation.
  12  * Copyright (C) 2004 Andi Kleen, SuSE Labs
  13  *
  14  * Extended attribute support for tmpfs:
  15  * Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@lkcl.net>
  16  * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
  17  *
  18  * tiny-shmem:
  19  * Copyright (c) 2004, 2008 Matt Mackall <mpm@selenic.com>
  20  *
  21  * This file is released under the GPL.
  22  */
  23
  24 #include <linux/fs.h>
  25 #include <linux/init.h>
  26 #include <linux/vfs.h>
  27 #include <linux/mount.h>
  28 #include <linux/ramfs.h>
  29 #include <linux/pagemap.h>
  30 #include <linux/file.h>
  31 #include <linux/fileattr.h>
  32 #include <linux/mm.h>
  33 #include <linux/random.h>
  34 #include <linux/sched/signal.h>
  35 #include <linux/export.h>
  36 #include <linux/swap.h>
  37 #include <linux/uio.h>
  38 #include <linux/hugetlb.h>
  39 #include <linux/fs_parser.h>
  40 #include <linux/swapfile.h>
  41 #include "swap.h"
  42
  43 static struct vfsmount *shm_mnt;
  44
  45 #ifdef CONFIG_SHMEM
  46 /*
  47  * This virtual memory filesystem is heavily based on the ramfs. It
  48  * extends ramfs by the ability to use swap and honor resource limits
  49  * which makes it a completely usable filesystem.
  50  */
  51
  52 #include <linux/xattr.h>
  53 #include <linux/exportfs.h>
  54 #include <linux/posix_acl.h>
  55 #include <linux/posix_acl_xattr.h>
  56 #include <linux/mman.h>
  57 #include <linux/string.h>
  58 #include <linux/slab.h>
  59 #include <linux/backing-dev.h>
  60 #include <linux/shmem_fs.h>
  61 #include <linux/writeback.h>
  62 #include <linux/pagevec.h>
  63 #include <linux/percpu_counter.h>
  64 #include <linux/falloc.h>
  65 #include <linux/splice.h>
  66 #include <linux/security.h>
  67 #include <linux/swapops.h>
  68 #include <linux/mempolicy.h>
  69 #include <linux/namei.h>
  70 #include <linux/ctype.h>
  71 #include <linux/migrate.h>
  72 #include <linux/highmem.h>
  73 #include <linux/seq_file.h>
  74 #include <linux/magic.h>
  75 #include <linux/syscalls.h>
  76 #include <linux/fcntl.h>
  77 #include <uapi/linux/memfd.h>
  78 #include <linux/userfaultfd_k.h>
  79 #include <linux/rmap.h>
  80 #include <linux/uuid.h>
  81
  82 #include <linux/uaccess.h>
  83
  84 #include "internal.h"
  85
  86 #define BLOCKS_PER_PAGE  (PAGE_SIZE/512)
  87 #define VM_ACCT(size)    (PAGE_ALIGN(size) >> PAGE_SHIFT)
  88
  89 /* Pretend that each entry is of this size in directory's i_size */
  90 #define BOGO_DIRENT_SIZE 20
  91
  92 /* Symlink up to this size is kmalloc'ed instead of using a swappable page */
  93 #define SHORT_SYMLINK_LEN 128
  94
  95 /*
  96  * shmem_fallocate communicates with shmem_fault or shmem_writepage via
  97  * inode->i_private (with i_rwsem making sure that it has only one user at
  98  * a time): we would prefer not to enlarge the shmem inode just for that.
  99  */
 100 struct shmem_falloc {
 101         wait_queue_head_t *waitq; /* faults into hole wait for punch to end */
 102         pgoff_t start;          /* start of range currently being fallocated */
 103         pgoff_t next;           /* the next page offset to be fallocated */
 104         pgoff_t nr_falloced;    /* how many new pages have been fallocated */
 105         pgoff_t nr_unswapped;   /* how often writepage refused to swap out */
 106 };
 107
 108 struct shmem_options {
 109         unsigned long long blocks;
 110         unsigned long long inodes;
 111         struct mempolicy *mpol;
 112         kuid_t uid;
 113         kgid_t gid;
 114         umode_t mode;
 115         bool full_inums;
 116         int huge;
 117         int seen;
 118 #define SHMEM_SEEN_BLOCKS 1
 119 #define SHMEM_SEEN_INODES 2
 120 #define SHMEM_SEEN_HUGE 4
 121 #define SHMEM_SEEN_INUMS 8
 122 };
 123
 124 #ifdef CONFIG_TMPFS
 125 static unsigned long shmem_default_max_blocks(void)
 126 {
 127         return totalram_pages() / 2;
 128 }
 129
 130 static unsigned long shmem_default_max_inodes(void)
 131 {
 132         unsigned long nr_pages = totalram_pages();
 133
 134         return min(nr_pages - totalhigh_pages(), nr_pages / 2);
 135 }
 136 #endif
 137
 138 static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
 139                              struct folio **foliop, enum sgp_type sgp,
 140                              gfp_t gfp, struct vm_area_struct *vma,
 141                              vm_fault_t *fault_type);
 142 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
 143                 struct page **pagep, enum sgp_type sgp,
 144                 gfp_t gfp, struct vm_area_struct *vma,
 145                 struct vm_fault *vmf, vm_fault_t *fault_type);
 146
 147 int shmem_getpage(struct inode *inode, pgoff_t index,
 148                 struct page **pagep, enum sgp_type sgp)
 149 {
 150         return shmem_getpage_gfp(inode, index, pagep, sgp,
 151                 mapping_gfp_mask(inode->i_mapping), NULL, NULL, NULL);
 152 }
 153
 154 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
 155 {
 156         return sb->s_fs_info;
 157 }
 158
 159 /*
 160  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
 161  * for shared memory and for shared anonymous (/dev/zero) mappings
 162  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
 163  * consistent with the pre-accounting of private mappings ...
 164  */
 165 static inline int shmem_acct_size(unsigned long flags, loff_t size)
 166 {
 167         return (flags & VM_NORESERVE) ?
 168                 0 : security_vm_enough_memory_mm(current->mm, VM_ACCT(size));
 169 }
 170
 171 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
 172 {
 173         if (!(flags & VM_NORESERVE))
 174                 vm_unacct_memory(VM_ACCT(size));
 175 }
 176
 177 static inline int shmem_reacct_size(unsigned long flags,
 178                 loff_t oldsize, loff_t newsize)
 179 {
 180         if (!(flags & VM_NORESERVE)) {
 181                 if (VM_ACCT(newsize) > VM_ACCT(oldsize))
 182                         return security_vm_enough_memory_mm(current->mm,
 183                                         VM_ACCT(newsize) - VM_ACCT(oldsize));
 184                 else if (VM_ACCT(newsize) < VM_ACCT(oldsize))
 185                         vm_unacct_memory(VM_ACCT(oldsize) - VM_ACCT(newsize));
 186         }
 187         return 0;
 188 }
 189
 190 /*
 191  * ... whereas tmpfs objects are accounted incrementally as
 192  * pages are allocated, in order to allow large sparse files.
 193  * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
 194  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
 195  */
 196 static inline int shmem_acct_block(unsigned long flags, long pages)
 197 {
 198         if (!(flags & VM_NORESERVE))
 199                 return 0;
 200
 201         return security_vm_enough_memory_mm(current->mm,
 202                         pages * VM_ACCT(PAGE_SIZE));
 203 }
 204
 205 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
 206 {
 207         if (flags & VM_NORESERVE)
 208                 vm_unacct_memory(pages * VM_ACCT(PAGE_SIZE));
 209 }
 210
 211 static inline bool shmem_inode_acct_block(struct inode *inode, long pages)
 212 {
 213         struct shmem_inode_info *info = SHMEM_I(inode);
 214         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 215
 216         if (shmem_acct_block(info->flags, pages))
 217                 return false;
 218
 219         if (sbinfo->max_blocks) {
 220                 if (percpu_counter_compare(&sbinfo->used_blocks,
 221                                            sbinfo->max_blocks - pages) > 0)
 222                         goto unacct;
 223                 percpu_counter_add(&sbinfo->used_blocks, pages);
 224         }
 225
 226         return true;
 227
 228 unacct:
 229         shmem_unacct_blocks(info->flags, pages);
 230         return false;
 231 }
 232
 233 static inline void shmem_inode_unacct_blocks(struct inode *inode, long pages)
 234 {
 235         struct shmem_inode_info *info = SHMEM_I(inode);
 236         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 237
 238         if (sbinfo->max_blocks)
 239                 percpu_counter_sub(&sbinfo->used_blocks, pages);
 240         shmem_unacct_blocks(info->flags, pages);
 241 }
 242
 243 static const struct super_operations shmem_ops;
 244 const struct address_space_operations shmem_aops;
 245 static const struct file_operations shmem_file_operations;
 246 static const struct inode_operations shmem_inode_operations;
 247 static const struct inode_operations shmem_dir_inode_operations;
 248 static const struct inode_operations shmem_special_inode_operations;
 249 static const struct vm_operations_struct shmem_vm_ops;
 250 static struct file_system_type shmem_fs_type;
 251
 252 bool vma_is_shmem(struct vm_area_struct *vma)
 253 {
 254         return vma->vm_ops == &shmem_vm_ops;
 255 }
 256
 257 static LIST_HEAD(shmem_swaplist);
 258 static DEFINE_MUTEX(shmem_swaplist_mutex);
 259
 260 /*
 261  * shmem_reserve_inode() performs bookkeeping to reserve a shmem inode, and
 262  * produces a novel ino for the newly allocated inode.
 263  *
 264  * It may also be called when making a hard link to permit the space needed by
 265  * each dentry. However, in that case, no new inode number is needed since that
 266  * internally draws from another pool of inode numbers (currently global
 267  * get_next_ino()). This case is indicated by passing NULL as inop.
 268  */
 269 #define SHMEM_INO_BATCH 1024
 270 static int shmem_reserve_inode(struct super_block *sb, ino_t *inop)
 271 {
 272         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
 273         ino_t ino;
 274
 275         if (!(sb->s_flags & SB_KERNMOUNT)) {
 276                 raw_spin_lock(&sbinfo->stat_lock);
 277                 if (sbinfo->max_inodes) {
 278                         if (!sbinfo->free_inodes) {
 279                                 raw_spin_unlock(&sbinfo->stat_lock);
 280                                 return -ENOSPC;
 281                         }
 282                         sbinfo->free_inodes--;
 283                 }
 284                 if (inop) {
 285                         ino = sbinfo->next_ino++;
 286                         if (unlikely(is_zero_ino(ino)))
 287                                 ino = sbinfo->next_ino++;
 288                         if (unlikely(!sbinfo->full_inums &&
 289                                      ino > UINT_MAX)) {
 290                                 /*
 291                                  * Emulate get_next_ino uint wraparound for
 292                                  * compatibility
 293                                  */
 294                                 if (IS_ENABLED(CONFIG_64BIT))
 295                                         pr_warn("%s: inode number overflow on device %d, consider using inode64 mount option\n",
 296                                                 __func__, MINOR(sb->s_dev));
 297                                 sbinfo->next_ino = 1;
 298                                 ino = sbinfo->next_ino++;
 299                         }
 300                         *inop = ino;
 301                 }
 302                 raw_spin_unlock(&sbinfo->stat_lock);
 303         } else if (inop) {
 304                 /*
 305                  * __shmem_file_setup, one of our callers, is lock-free: it
 306                  * doesn't hold stat_lock in shmem_reserve_inode since
 307                  * max_inodes is always 0, and is called from potentially
 308                  * unknown contexts. As such, use a per-cpu batched allocator
 309                  * which doesn't require the per-sb stat_lock unless we are at
 310                  * the batch boundary.
 311                  *
 312                  * We don't need to worry about inode{32,64} since SB_KERNMOUNT
 313                  * shmem mounts are not exposed to userspace, so we don't need
 314                  * to worry about things like glibc compatibility.
 315                  */
 316                 ino_t *next_ino;
 317
 318                 next_ino = per_cpu_ptr(sbinfo->ino_batch, get_cpu());
 319                 ino = *next_ino;
 320                 if (unlikely(ino % SHMEM_INO_BATCH == 0)) {
 321                         raw_spin_lock(&sbinfo->stat_lock);
 322                         ino = sbinfo->next_ino;
 323                         sbinfo->next_ino += SHMEM_INO_BATCH;
 324                         raw_spin_unlock(&sbinfo->stat_lock);
 325                         if (unlikely(is_zero_ino(ino)))
 326                                 ino++;
 327                 }
 328                 *inop = ino;
 329                 *next_ino = ++ino;
 330                 put_cpu();
 331         }
 332
 333         return 0;
 334 }
 335
 336 static void shmem_free_inode(struct super_block *sb)
 337 {
 338         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
 339         if (sbinfo->max_inodes) {
 340                 raw_spin_lock(&sbinfo->stat_lock);
 341                 sbinfo->free_inodes++;
 342                 raw_spin_unlock(&sbinfo->stat_lock);
 343         }
 344 }
 345
 346 /**
 347  * shmem_recalc_inode - recalculate the block usage of an inode
 348  * @inode: inode to recalc
 349  *
 350  * We have to calculate the free blocks since the mm can drop
 351  * undirtied hole pages behind our back.
 352  *
 353  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
 354  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
 355  *
 356  * It has to be called with the spinlock held.
 357  */
 358 static void shmem_recalc_inode(struct inode *inode)
 359 {
 360         struct shmem_inode_info *info = SHMEM_I(inode);
 361         long freed;
 362
 363         freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
 364         if (freed > 0) {
 365                 info->alloced -= freed;
 366                 inode->i_blocks -= freed * BLOCKS_PER_PAGE;
 367                 shmem_inode_unacct_blocks(inode, freed);
 368         }
 369 }
 370
 371 bool shmem_charge(struct inode *inode, long pages)
 372 {
 373         struct shmem_inode_info *info = SHMEM_I(inode);
 374         unsigned long flags;
 375
 376         if (!shmem_inode_acct_block(inode, pages))
 377                 return false;
 378
 379         /* nrpages adjustment first, then shmem_recalc_inode() when balanced */
 380         inode->i_mapping->nrpages += pages;
 381
 382         spin_lock_irqsave(&info->lock, flags);
 383         info->alloced += pages;
 384         inode->i_blocks += pages * BLOCKS_PER_PAGE;
 385         shmem_recalc_inode(inode);
 386         spin_unlock_irqrestore(&info->lock, flags);
 387
 388         return true;
 389 }
 390
 391 void shmem_uncharge(struct inode *inode, long pages)
 392 {
 393         struct shmem_inode_info *info = SHMEM_I(inode);
 394         unsigned long flags;
 395
 396         /* nrpages adjustment done by __filemap_remove_folio() or caller */
 397
 398         spin_lock_irqsave(&info->lock, flags);
 399         info->alloced -= pages;
 400         inode->i_blocks -= pages * BLOCKS_PER_PAGE;
 401         shmem_recalc_inode(inode);
 402         spin_unlock_irqrestore(&info->lock, flags);
 403
 404         shmem_inode_unacct_blocks(inode, pages);
 405 }
 406
 407 /*
 408  * Replace item expected in xarray by a new item, while holding xa_lock.
 409  */
 410 static int shmem_replace_entry(struct address_space *mapping,
 411                         pgoff_t index, void *expected, void *replacement)
 412 {
 413         XA_STATE(xas, &mapping->i_pages, index);
 414         void *item;
 415
 416         VM_BUG_ON(!expected);
 417         VM_BUG_ON(!replacement);
 418         item = xas_load(&xas);
 419         if (item != expected)
 420                 return -ENOENT;
 421         xas_store(&xas, replacement);
 422         return 0;
 423 }
 424
 425 /*
 426  * Sometimes, before we decide whether to proceed or to fail, we must check
 427  * that an entry was not already brought back from swap by a racing thread.
 428  *
 429  * Checking page is not enough: by the time a SwapCache page is locked, it
 430  * might be reused, and again be SwapCache, using the same swap as before.
 431  */
 432 static bool shmem_confirm_swap(struct address_space *mapping,
 433                                pgoff_t index, swp_entry_t swap)
 434 {
 435         return xa_load(&mapping->i_pages, index) == swp_to_radix_entry(swap);
 436 }
 437
 438 /*
 439  * Definitions for "huge tmpfs": tmpfs mounted with the huge= option
 440  *
 441  * SHMEM_HUGE_NEVER:
 442  *      disables huge pages for the mount;
 443  * SHMEM_HUGE_ALWAYS:
 444  *      enables huge pages for the mount;
 445  * SHMEM_HUGE_WITHIN_SIZE:
 446  *      only allocate huge pages if the page will be fully within i_size,
 447  *      also respect fadvise()/madvise() hints;
 448  * SHMEM_HUGE_ADVISE:
 449  *      only allocate huge pages if requested with fadvise()/madvise();
 450  */
 451
 452 #define SHMEM_HUGE_NEVER        0
 453 #define SHMEM_HUGE_ALWAYS       1
 454 #define SHMEM_HUGE_WITHIN_SIZE  2
 455 #define SHMEM_HUGE_ADVISE       3
 456
 457 /*
 458  * Special values.
 459  * Only can be set via /sys/kernel/mm/transparent_hugepage/shmem_enabled:
 460  *
 461  * SHMEM_HUGE_DENY:
 462  *      disables huge on shm_mnt and all mounts, for emergency use;
 463  * SHMEM_HUGE_FORCE:
 464  *      enables huge on shm_mnt and all mounts, w/o needing option, for testing;
 465  *
 466  */
 467 #define SHMEM_HUGE_DENY         (-1)
 468 #define SHMEM_HUGE_FORCE        (-2)
 469
 470 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 471 /* ifdef here to avoid bloating shmem.o when not necessary */
 472
 473 static int shmem_huge __read_mostly = SHMEM_HUGE_NEVER;
 474
 475 bool shmem_is_huge(struct vm_area_struct *vma,
 476                    struct inode *inode, pgoff_t index)
 477 {
 478         loff_t i_size;
 479
 480         if (!S_ISREG(inode->i_mode))
 481                 return false;
 482         if (shmem_huge == SHMEM_HUGE_DENY)
 483                 return false;
 484         if (vma && ((vma->vm_flags & VM_NOHUGEPAGE) ||
 485             test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)))
 486                 return false;
 487         if (shmem_huge == SHMEM_HUGE_FORCE)
 488                 return true;
 489
 490         switch (SHMEM_SB(inode->i_sb)->huge) {
 491         case SHMEM_HUGE_ALWAYS:
 492                 return true;
 493         case SHMEM_HUGE_WITHIN_SIZE:
 494                 index = round_up(index + 1, HPAGE_PMD_NR);
 495                 i_size = round_up(i_size_read(inode), PAGE_SIZE);
 496                 if (i_size >> PAGE_SHIFT >= index)
 497                         return true;
 498                 fallthrough;
 499         case SHMEM_HUGE_ADVISE:
 500                 if (vma && (vma->vm_flags & VM_HUGEPAGE))
 501                         return true;
 502                 fallthrough;
 503         default:
 504                 return false;
 505         }
 506 }
 507
 508 #if defined(CONFIG_SYSFS)
 509 static int shmem_parse_huge(const char *str)
 510 {
 511         if (!strcmp(str, "never"))
 512                 return SHMEM_HUGE_NEVER;
 513         if (!strcmp(str, "always"))
 514                 return SHMEM_HUGE_ALWAYS;
 515         if (!strcmp(str, "within_size"))
 516                 return SHMEM_HUGE_WITHIN_SIZE;
 517         if (!strcmp(str, "advise"))
 518                 return SHMEM_HUGE_ADVISE;
 519         if (!strcmp(str, "deny"))
 520                 return SHMEM_HUGE_DENY;
 521         if (!strcmp(str, "force"))
 522                 return SHMEM_HUGE_FORCE;
 523         return -EINVAL;
 524 }
 525 #endif
 526
 527 #if defined(CONFIG_SYSFS) || defined(CONFIG_TMPFS)
 528 static const char *shmem_format_huge(int huge)
 529 {
 530         switch (huge) {
 531         case SHMEM_HUGE_NEVER:
 532                 return "never";
 533         case SHMEM_HUGE_ALWAYS:
 534                 return "always";
 535         case SHMEM_HUGE_WITHIN_SIZE:
 536                 return "within_size";
 537         case SHMEM_HUGE_ADVISE:
 538                 return "advise";
 539         case SHMEM_HUGE_DENY:
 540                 return "deny";
 541         case SHMEM_HUGE_FORCE:
 542                 return "force";
 543         default:
 544                 VM_BUG_ON(1);
 545                 return "bad_val";
 546         }
 547 }
 548 #endif
 549
 550 static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
 551                 struct shrink_control *sc, unsigned long nr_to_split)
 552 {
 553         LIST_HEAD(list), *pos, *next;
 554         LIST_HEAD(to_remove);
 555         struct inode *inode;
 556         struct shmem_inode_info *info;
 557         struct folio *folio;
 558         unsigned long batch = sc ? sc->nr_to_scan : 128;
 559         int split = 0;
 560
 561         if (list_empty(&sbinfo->shrinklist))
 562                 return SHRINK_STOP;
 563
 564         spin_lock(&sbinfo->shrinklist_lock);
 565         list_for_each_safe(pos, next, &sbinfo->shrinklist) {
 566                 info = list_entry(pos, struct shmem_inode_info, shrinklist);
 567
 568                 /* pin the inode */
 569                 inode = igrab(&info->vfs_inode);
 570
 571                 /* inode is about to be evicted */
 572                 if (!inode) {
 573                         list_del_init(&info->shrinklist);
 574                         goto next;
 575                 }
 576
 577                 /* Check if there's anything to gain */
 578                 if (round_up(inode->i_size, PAGE_SIZE) ==
 579                                 round_up(inode->i_size, HPAGE_PMD_SIZE)) {
 580                         list_move(&info->shrinklist, &to_remove);
 581                         goto next;
 582                 }
 583
 584                 list_move(&info->shrinklist, &list);
 585 next:
 586                 sbinfo->shrinklist_len--;
 587                 if (!--batch)
 588                         break;
 589         }
 590         spin_unlock(&sbinfo->shrinklist_lock);
 591
 592         list_for_each_safe(pos, next, &to_remove) {
 593                 info = list_entry(pos, struct shmem_inode_info, shrinklist);
 594                 inode = &info->vfs_inode;
 595                 list_del_init(&info->shrinklist);
 596                 iput(inode);
 597         }
 598
 599         list_for_each_safe(pos, next, &list) {
 600                 int ret;
 601                 pgoff_t index;
 602
 603                 info = list_entry(pos, struct shmem_inode_info, shrinklist);
 604                 inode = &info->vfs_inode;
 605
 606                 if (nr_to_split && split >= nr_to_split)
 607                         goto move_back;
 608
 609                 index = (inode->i_size & HPAGE_PMD_MASK) >> PAGE_SHIFT;
 610                 folio = filemap_get_folio(inode->i_mapping, index);
 611                 if (!folio)
 612                         goto drop;
 613
 614                 /* No huge page at the end of the file: nothing to split */
 615                 if (!folio_test_large(folio)) {
 616                         folio_put(folio);
 617                         goto drop;
 618                 }
 619
 620                 /*
 621                  * Move the inode on the list back to shrinklist if we failed
 622                  * to lock the page at this time.
 623                  *
 624                  * Waiting for the lock may lead to deadlock in the
 625                  * reclaim path.
 626                  */
 627                 if (!folio_trylock(folio)) {
 628                         folio_put(folio);
 629                         goto move_back;
 630                 }
 631
 632                 ret = split_huge_page(&folio->page);
 633                 folio_unlock(folio);
 634                 folio_put(folio);
 635
 636                 /* If split failed move the inode on the list back to shrinklist */
 637                 if (ret)
 638                         goto move_back;
 639
 640                 split++;
 641 drop:
 642                 list_del_init(&info->shrinklist);
 643                 goto put;
 644 move_back:
 645                 /*
 646                  * Make sure the inode is either on the global list or deleted
 647                  * from any local list before iput() since it could be deleted
 648                  * in another thread once we put the inode (then the local list
 649                  * is corrupted).
 650                  */
 651                 spin_lock(&sbinfo->shrinklist_lock);
 652                 list_move(&info->shrinklist, &sbinfo->shrinklist);
 653                 sbinfo->shrinklist_len++;
 654                 spin_unlock(&sbinfo->shrinklist_lock);
 655 put:
 656                 iput(inode);
 657         }
 658
 659         return split;
 660 }
 661
 662 static long shmem_unused_huge_scan(struct super_block *sb,
 663                 struct shrink_control *sc)
 664 {
 665         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
 666
 667         if (!READ_ONCE(sbinfo->shrinklist_len))
 668                 return SHRINK_STOP;
 669
 670         return shmem_unused_huge_shrink(sbinfo, sc, 0);
 671 }
 672
 673 static long shmem_unused_huge_count(struct super_block *sb,
 674                 struct shrink_control *sc)
 675 {
 676         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
 677         return READ_ONCE(sbinfo->shrinklist_len);
 678 }
 679 #else /* !CONFIG_TRANSPARENT_HUGEPAGE */
 680
 681 #define shmem_huge SHMEM_HUGE_DENY
 682
 683 bool shmem_is_huge(struct vm_area_struct *vma,
 684                    struct inode *inode, pgoff_t index)
 685 {
 686         return false;
 687 }
 688
 689 static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
 690                 struct shrink_control *sc, unsigned long nr_to_split)
 691 {
 692         return 0;
 693 }
 694 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 695
 696 /*
 697  * Like filemap_add_folio, but error if expected item has gone.
 698  */
 699 static int shmem_add_to_page_cache(struct folio *folio,
 700                                    struct address_space *mapping,
 701                                    pgoff_t index, void *expected, gfp_t gfp,
 702                                    struct mm_struct *charge_mm)
 703 {
 704         XA_STATE_ORDER(xas, &mapping->i_pages, index, folio_order(folio));
 705         long nr = folio_nr_pages(folio);
 706         int error;
 707
 708         VM_BUG_ON_FOLIO(index != round_down(index, nr), folio);
 709         VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
 710         VM_BUG_ON_FOLIO(!folio_test_swapbacked(folio), folio);
 711         VM_BUG_ON(expected && folio_test_large(folio));
 712
 713         folio_ref_add(folio, nr);
 714         folio->mapping = mapping;
 715         folio->index = index;
 716
 717         if (!folio_test_swapcache(folio)) {
 718                 error = mem_cgroup_charge(folio, charge_mm, gfp);
 719                 if (error) {
 720                         if (folio_test_pmd_mappable(folio)) {
 721                                 count_vm_event(THP_FILE_FALLBACK);
 722                                 count_vm_event(THP_FILE_FALLBACK_CHARGE);
 723                         }
 724                         goto error;
 725                 }
 726         }
 727         folio_throttle_swaprate(folio, gfp);
 728
 729         do {
 730                 xas_lock_irq(&xas);
 731                 if (expected != xas_find_conflict(&xas)) {
 732                         xas_set_err(&xas, -EEXIST);
 733                         goto unlock;
 734                 }
 735                 if (expected && xas_find_conflict(&xas)) {
 736                         xas_set_err(&xas, -EEXIST);
 737                         goto unlock;
 738                 }
 739                 xas_store(&xas, folio);
 740                 if (xas_error(&xas))
 741                         goto unlock;
 742                 if (folio_test_pmd_mappable(folio)) {
 743                         count_vm_event(THP_FILE_ALLOC);
 744                         __lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, nr);
 745                 }
 746                 mapping->nrpages += nr;
 747                 __lruvec_stat_mod_folio(folio, NR_FILE_PAGES, nr);
 748                 __lruvec_stat_mod_folio(folio, NR_SHMEM, nr);
 749 unlock:
 750                 xas_unlock_irq(&xas);
 751         } while (xas_nomem(&xas, gfp));
 752
 753         if (xas_error(&xas)) {
 754                 error = xas_error(&xas);
 755                 goto error;
 756         }
 757
 758         return 0;
 759 error:
 760         folio->mapping = NULL;
 761         folio_ref_sub(folio, nr);
 762         return error;
 763 }
 764
 765 /*
 766  * Like delete_from_page_cache, but substitutes swap for page.
 767  */
 768 static void shmem_delete_from_page_cache(struct page *page, void *radswap)
 769 {
 770         struct address_space *mapping = page->mapping;
 771         int error;
 772
 773         VM_BUG_ON_PAGE(PageCompound(page), page);
 774
 775         xa_lock_irq(&mapping->i_pages);
 776         error = shmem_replace_entry(mapping, page->index, page, radswap);
 777         page->mapping = NULL;
 778         mapping->nrpages--;
 779         __dec_lruvec_page_state(page, NR_FILE_PAGES);
 780         __dec_lruvec_page_state(page, NR_SHMEM);
 781         xa_unlock_irq(&mapping->i_pages);
 782         put_page(page);
 783         BUG_ON(error);
 784 }
 785
 786 /*
 787  * Remove swap entry from page cache, free the swap and its page cache.
 788  */
 789 static int shmem_free_swap(struct address_space *mapping,
 790                            pgoff_t index, void *radswap)
 791 {
 792         void *old;
 793
 794         old = xa_cmpxchg_irq(&mapping->i_pages, index, radswap, NULL, 0);
 795         if (old != radswap)
 796                 return -ENOENT;
 797         free_swap_and_cache(radix_to_swp_entry(radswap));
 798         return 0;
 799 }
 800
 801 /*
 802  * Determine (in bytes) how many of the shmem object's pages mapped by the
 803  * given offsets are swapped out.
 804  *
 805  * This is safe to call without i_rwsem or the i_pages lock thanks to RCU,
 806  * as long as the inode doesn't go away and racy results are not a problem.
 807  */
 808 unsigned long shmem_partial_swap_usage(struct address_space *mapping,
 809                                                 pgoff_t start, pgoff_t end)
 810 {
 811         XA_STATE(xas, &mapping->i_pages, start);
 812         struct page *page;
 813         unsigned long swapped = 0;
 814
 815         rcu_read_lock();
 816         xas_for_each(&xas, page, end - 1) {
 817                 if (xas_retry(&xas, page))
 818                         continue;
 819                 if (xa_is_value(page))
 820                         swapped++;
 821
 822                 if (need_resched()) {
 823                         xas_pause(&xas);
 824                         cond_resched_rcu();
 825                 }
 826         }
 827
 828         rcu_read_unlock();
 829
 830         return swapped << PAGE_SHIFT;
 831 }
 832
 833 /*
 834  * Determine (in bytes) how many of the shmem object's pages mapped by the
 835  * given vma is swapped out.
 836  *
 837  * This is safe to call without i_rwsem or the i_pages lock thanks to RCU,
 838  * as long as the inode doesn't go away and racy results are not a problem.
 839  */
 840 unsigned long shmem_swap_usage(struct vm_area_struct *vma)
 841 {
 842         struct inode *inode = file_inode(vma->vm_file);
 843         struct shmem_inode_info *info = SHMEM_I(inode);
 844         struct address_space *mapping = inode->i_mapping;
 845         unsigned long swapped;
 846
 847         /* Be careful as we don't hold info->lock */
 848         swapped = READ_ONCE(info->swapped);
 849
 850         /*
 851          * The easier cases are when the shmem object has nothing in swap, or
 852          * the vma maps it whole. Then we can simply use the stats that we
 853          * already track.
 854          */
 855         if (!swapped)
 856                 return 0;
 857
 858         if (!vma->vm_pgoff && vma->vm_end - vma->vm_start >= inode->i_size)
 859                 return swapped << PAGE_SHIFT;
 860
 861         /* Here comes the more involved part */
 862         return shmem_partial_swap_usage(mapping, vma->vm_pgoff,
 863                                         vma->vm_pgoff + vma_pages(vma));
 864 }
 865
 866 /*
 867  * SysV IPC SHM_UNLOCK restore Unevictable pages to their evictable lists.
 868  */
 869 void shmem_unlock_mapping(struct address_space *mapping)
 870 {
 871         struct folio_batch fbatch;
 872         pgoff_t index = 0;
 873
 874         folio_batch_init(&fbatch);
 875         /*
 876          * Minor point, but we might as well stop if someone else SHM_LOCKs it.
 877          */
 878         while (!mapping_unevictable(mapping) &&
 879                filemap_get_folios(mapping, &index, ~0UL, &fbatch)) {
 880                 check_move_unevictable_folios(&fbatch);
 881                 folio_batch_release(&fbatch);
 882                 cond_resched();
 883         }
 884 }
 885
 886 static struct folio *shmem_get_partial_folio(struct inode *inode, pgoff_t index)
 887 {
 888         struct folio *folio;
 889         struct page *page;
 890
 891         /*
 892          * At first avoid shmem_getpage(,,,SGP_READ): that fails
 893          * beyond i_size, and reports fallocated pages as holes.
 894          */
 895         folio = __filemap_get_folio(inode->i_mapping, index,
 896                                         FGP_ENTRY | FGP_LOCK, 0);
 897         if (!xa_is_value(folio))
 898                 return folio;
 899         /*
 900          * But read a page back from swap if any of it is within i_size
 901          * (although in some cases this is just a waste of time).
 902          */
 903         page = NULL;
 904         shmem_getpage(inode, index, &page, SGP_READ);
 905         return page ? page_folio(page) : NULL;
 906 }
 907
 908 /*
 909  * Remove range of pages and swap entries from page cache, and free them.
 910  * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate.
 911  */
 912 static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
 913                                                                  bool unfalloc)
 914 {
 915         struct address_space *mapping = inode->i_mapping;
 916         struct shmem_inode_info *info = SHMEM_I(inode);
 917         pgoff_t start = (lstart + PAGE_SIZE - 1) >> PAGE_SHIFT;
 918         pgoff_t end = (lend + 1) >> PAGE_SHIFT;
 919         struct folio_batch fbatch;
 920         pgoff_t indices[PAGEVEC_SIZE];
 921         struct folio *folio;
 922         bool same_folio;
 923         long nr_swaps_freed = 0;
 924         pgoff_t index;
 925         int i;
 926
 927         if (lend == -1)
 928                 end = -1;       /* unsigned, so actually very big */
 929
 930         if (info->fallocend > start && info->fallocend <= end && !unfalloc)
 931                 info->fallocend = start;
 932
 933         folio_batch_init(&fbatch);
 934         index = start;
 935         while (index < end && find_lock_entries(mapping, index, end - 1,
 936                         &fbatch, indices)) {
 937                 for (i = 0; i < folio_batch_count(&fbatch); i++) {
 938                         folio = fbatch.folios[i];
 939
 940                         index = indices[i];
 941
 942                         if (xa_is_value(folio)) {
 943                                 if (unfalloc)
 944                                         continue;
 945                                 nr_swaps_freed += !shmem_free_swap(mapping,
 946                                                                 index, folio);
 947                                 continue;
 948                         }
 949                         index += folio_nr_pages(folio) - 1;
 950
 951                         if (!unfalloc || !folio_test_uptodate(folio))
 952                                 truncate_inode_folio(mapping, folio);
 953                         folio_unlock(folio);
 954                 }
 955                 folio_batch_remove_exceptionals(&fbatch);
 956                 folio_batch_release(&fbatch);
 957                 cond_resched();
 958                 index++;
 959         }
 960
 961         same_folio = (lstart >> PAGE_SHIFT) == (lend >> PAGE_SHIFT);
 962         folio = shmem_get_partial_folio(inode, lstart >> PAGE_SHIFT);
 963         if (folio) {
 964                 same_folio = lend < folio_pos(folio) + folio_size(folio);
 965                 folio_mark_dirty(folio);
 966                 if (!truncate_inode_partial_folio(folio, lstart, lend)) {
 967                         start = folio->index + folio_nr_pages(folio);
 968                         if (same_folio)
 969                                 end = folio->index;
 970                 }
 971                 folio_unlock(folio);
 972                 folio_put(folio);
 973                 folio = NULL;
 974         }
 975
 976         if (!same_folio)
 977                 folio = shmem_get_partial_folio(inode, lend >> PAGE_SHIFT);
 978         if (folio) {
 979                 folio_mark_dirty(folio);
 980                 if (!truncate_inode_partial_folio(folio, lstart, lend))
 981                         end = folio->index;
 982                 folio_unlock(folio);
 983                 folio_put(folio);
 984         }
 985
 986         index = start;
 987         while (index < end) {
 988                 cond_resched();
 989
 990                 if (!find_get_entries(mapping, index, end - 1, &fbatch,
 991                                 indices)) {
 992                         /* If all gone or hole-punch or unfalloc, we're done */
 993                         if (index == start || end != -1)
 994                                 break;
 995                         /* But if truncating, restart to make sure all gone */
 996                         index = start;
 997                         continue;
 998                 }
 999                 for (i = 0; i < folio_batch_count(&fbatch); i++) {
1000                         folio = fbatch.folios[i];
1001
1002                         index = indices[i];
1003                         if (xa_is_value(folio)) {
1004                                 if (unfalloc)
1005                                         continue;
1006                                 if (shmem_free_swap(mapping, index, folio)) {
1007                                         /* Swap was replaced by page: retry */
1008                                         index--;
1009                                         break;
1010                                 }
1011                                 nr_swaps_freed++;
1012                                 continue;
1013                         }
1014
1015                         folio_lock(folio);
1016
1017                         if (!unfalloc || !folio_test_uptodate(folio)) {
1018                                 if (folio_mapping(folio) != mapping) {
1019                                         /* Page was replaced by swap: retry */
1020                                         folio_unlock(folio);
1021                                         index--;
1022                                         break;
1023                                 }
1024                                 VM_BUG_ON_FOLIO(folio_test_writeback(folio),
1025                                                 folio);
1026                                 truncate_inode_folio(mapping, folio);
1027                         }
1028                         index = folio->index + folio_nr_pages(folio) - 1;
1029                         folio_unlock(folio);
1030                 }
1031                 folio_batch_remove_exceptionals(&fbatch);
1032                 folio_batch_release(&fbatch);
1033                 index++;
1034         }
1035
1036         spin_lock_irq(&info->lock);
1037         info->swapped -= nr_swaps_freed;
1038         shmem_recalc_inode(inode);
1039         spin_unlock_irq(&info->lock);
1040 }
1041
1042 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
1043 {
1044         shmem_undo_range(inode, lstart, lend, false);
1045         inode->i_ctime = inode->i_mtime = current_time(inode);
1046 }
1047 EXPORT_SYMBOL_GPL(shmem_truncate_range);
1048
1049 static int shmem_getattr(struct user_namespace *mnt_userns,
1050                          const struct path *path, struct kstat *stat,
1051                          u32 request_mask, unsigned int query_flags)
1052 {
1053         struct inode *inode = path->dentry->d_inode;
1054         struct shmem_inode_info *info = SHMEM_I(inode);
1055
1056         if (info->alloced - info->swapped != inode->i_mapping->nrpages) {
1057                 spin_lock_irq(&info->lock);
1058                 shmem_recalc_inode(inode);
1059                 spin_unlock_irq(&info->lock);
1060         }
1061         if (info->fsflags & FS_APPEND_FL)
1062                 stat->attributes |= STATX_ATTR_APPEND;
1063         if (info->fsflags & FS_IMMUTABLE_FL)
1064                 stat->attributes |= STATX_ATTR_IMMUTABLE;
1065         if (info->fsflags & FS_NODUMP_FL)
1066                 stat->attributes |= STATX_ATTR_NODUMP;
1067         stat->attributes_mask |= (STATX_ATTR_APPEND |
1068                         STATX_ATTR_IMMUTABLE |
1069                         STATX_ATTR_NODUMP);
1070         generic_fillattr(&init_user_ns, inode, stat);
1071
1072         if (shmem_is_huge(NULL, inode, 0))
1073                 stat->blksize = HPAGE_PMD_SIZE;
1074
1075         if (request_mask & STATX_BTIME) {
1076                 stat->result_mask |= STATX_BTIME;
1077                 stat->btime.tv_sec = info->i_crtime.tv_sec;
1078                 stat->btime.tv_nsec = info->i_crtime.tv_nsec;
1079         }
1080
1081         return 0;
1082 }
1083
1084 static int shmem_setattr(struct user_namespace *mnt_userns,
1085                          struct dentry *dentry, struct iattr *attr)
1086 {
1087         struct inode *inode = d_inode(dentry);
1088         struct shmem_inode_info *info = SHMEM_I(inode);
1089         int error;
1090
1091         error = setattr_prepare(&init_user_ns, dentry, attr);
1092         if (error)
1093                 return error;
1094
1095         if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
1096                 loff_t oldsize = inode->i_size;
1097                 loff_t newsize = attr->ia_size;
1098
1099                 /* protected by i_rwsem */
1100                 if ((newsize < oldsize && (info->seals & F_SEAL_SHRINK)) ||
1101                     (newsize > oldsize && (info->seals & F_SEAL_GROW)))
1102                         return -EPERM;
1103
1104                 if (newsize != oldsize) {
1105                         error = shmem_reacct_size(SHMEM_I(inode)->flags,
1106                                         oldsize, newsize);
1107                         if (error)
1108                                 return error;
1109                         i_size_write(inode, newsize);
1110                         inode->i_ctime = inode->i_mtime = current_time(inode);
1111                 }
1112                 if (newsize <= oldsize) {
1113                         loff_t holebegin = round_up(newsize, PAGE_SIZE);
1114                         if (oldsize > holebegin)
1115                                 unmap_mapping_range(inode->i_mapping,
1116                                                         holebegin, 0, 1);
1117                         if (info->alloced)
1118                                 shmem_truncate_range(inode,
1119                                                         newsize, (loff_t)-1);
1120                         /* unmap again to remove racily COWed private pages */
1121                         if (oldsize > holebegin)
1122                                 unmap_mapping_range(inode->i_mapping,
1123                                                         holebegin, 0, 1);
1124                 }
1125         }
1126
1127         setattr_copy(&init_user_ns, inode, attr);
1128         if (attr->ia_valid & ATTR_MODE)
1129                 error = posix_acl_chmod(&init_user_ns, inode, inode->i_mode);
1130         return error;
1131 }
1132
1133 static void shmem_evict_inode(struct inode *inode)
1134 {
1135         struct shmem_inode_info *info = SHMEM_I(inode);
1136         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1137
1138         if (shmem_mapping(inode->i_mapping)) {
1139                 shmem_unacct_size(info->flags, inode->i_size);
1140                 inode->i_size = 0;
1141                 mapping_set_exiting(inode->i_mapping);
1142                 shmem_truncate_range(inode, 0, (loff_t)-1);
1143                 if (!list_empty(&info->shrinklist)) {
1144                         spin_lock(&sbinfo->shrinklist_lock);
1145                         if (!list_empty(&info->shrinklist)) {
1146                                 list_del_init(&info->shrinklist);
1147                                 sbinfo->shrinklist_len--;
1148                         }
1149                         spin_unlock(&sbinfo->shrinklist_lock);
1150                 }
1151                 while (!list_empty(&info->swaplist)) {
1152                         /* Wait while shmem_unuse() is scanning this inode... */
1153                         wait_var_event(&info->stop_eviction,
1154                                        !atomic_read(&info->stop_eviction));
1155                         mutex_lock(&shmem_swaplist_mutex);
1156                         /* ...but beware of the race if we peeked too early */
1157                         if (!atomic_read(&info->stop_eviction))
1158                                 list_del_init(&info->swaplist);
1159                         mutex_unlock(&shmem_swaplist_mutex);
1160                 }
1161         }
1162
1163         simple_xattrs_free(&info->xattrs);
1164         WARN_ON(inode->i_blocks);
1165         shmem_free_inode(inode->i_sb);
1166         clear_inode(inode);
1167 }
1168
1169 static int shmem_find_swap_entries(struct address_space *mapping,
1170                                    pgoff_t start, struct folio_batch *fbatch,
1171                                    pgoff_t *indices, unsigned int type)
1172 {
1173         XA_STATE(xas, &mapping->i_pages, start);
1174         struct folio *folio;
1175         swp_entry_t entry;
1176
1177         rcu_read_lock();
1178         xas_for_each(&xas, folio, ULONG_MAX) {
1179                 if (xas_retry(&xas, folio))
1180                         continue;
1181
1182                 if (!xa_is_value(folio))
1183                         continue;
1184
1185                 entry = radix_to_swp_entry(folio);
1186                 /*
1187                  * swapin error entries can be found in the mapping. But they're
1188                  * deliberately ignored here as we've done everything we can do.
1189                  */
1190                 if (swp_type(entry) != type)
1191                         continue;
1192
1193                 indices[folio_batch_count(fbatch)] = xas.xa_index;
1194                 if (!folio_batch_add(fbatch, folio))
1195                         break;
1196
1197                 if (need_resched()) {
1198                         xas_pause(&xas);
1199                         cond_resched_rcu();
1200                 }
1201         }
1202         rcu_read_unlock();
1203
1204         return xas.xa_index;
1205 }
1206
1207 /*
1208  * Move the swapped pages for an inode to page cache. Returns the count
1209  * of pages swapped in, or the error in case of failure.
1210  */
1211 static int shmem_unuse_swap_entries(struct inode *inode,
1212                 struct folio_batch *fbatch, pgoff_t *indices)
1213 {
1214         int i = 0;
1215         int ret = 0;
1216         int error = 0;
1217         struct address_space *mapping = inode->i_mapping;
1218
1219         for (i = 0; i < folio_batch_count(fbatch); i++) {
1220                 struct folio *folio = fbatch->folios[i];
1221
1222                 if (!xa_is_value(folio))
1223                         continue;
1224                 error = shmem_swapin_folio(inode, indices[i],
1225                                           &folio, SGP_CACHE,
1226                                           mapping_gfp_mask(mapping),
1227                                           NULL, NULL);
1228                 if (error == 0) {
1229                         folio_unlock(folio);
1230                         folio_put(folio);
1231                         ret++;
1232                 }
1233                 if (error == -ENOMEM)
1234                         break;
1235                 error = 0;
1236         }
1237         return error ? error : ret;
1238 }
1239
1240 /*
1241  * If swap found in inode, free it and move page from swapcache to filecache.
1242  */
1243 static int shmem_unuse_inode(struct inode *inode, unsigned int type)
1244 {
1245         struct address_space *mapping = inode->i_mapping;
1246         pgoff_t start = 0;
1247         struct folio_batch fbatch;
1248         pgoff_t indices[PAGEVEC_SIZE];
1249         int ret = 0;
1250
1251         do {
1252                 folio_batch_init(&fbatch);
1253                 shmem_find_swap_entries(mapping, start, &fbatch, indices, type);
1254                 if (folio_batch_count(&fbatch) == 0) {
1255                         ret = 0;
1256                         break;
1257                 }
1258
1259                 ret = shmem_unuse_swap_entries(inode, &fbatch, indices);
1260                 if (ret < 0)
1261                         break;
1262
1263                 start = indices[folio_batch_count(&fbatch) - 1];
1264         } while (true);
1265
1266         return ret;
1267 }
1268
1269 /*
1270  * Read all the shared memory data that resides in the swap
1271  * device 'type' back into memory, so the swap device can be
1272  * unused.
1273  */
1274 int shmem_unuse(unsigned int type)
1275 {
1276         struct shmem_inode_info *info, *next;
1277         int error = 0;
1278
1279         if (list_empty(&shmem_swaplist))
1280                 return 0;
1281
1282         mutex_lock(&shmem_swaplist_mutex);
1283         list_for_each_entry_safe(info, next, &shmem_swaplist, swaplist) {
1284                 if (!info->swapped) {
1285                         list_del_init(&info->swaplist);
1286                         continue;
1287                 }
1288                 /*
1289                  * Drop the swaplist mutex while searching the inode for swap;
1290                  * but before doing so, make sure shmem_evict_inode() will not
1291                  * remove placeholder inode from swaplist, nor let it be freed
1292                  * (igrab() would protect from unlink, but not from unmount).
1293                  */
1294                 atomic_inc(&info->stop_eviction);
1295                 mutex_unlock(&shmem_swaplist_mutex);
1296
1297                 error = shmem_unuse_inode(&info->vfs_inode, type);
1298                 cond_resched();
1299
1300                 mutex_lock(&shmem_swaplist_mutex);
1301                 next = list_next_entry(info, swaplist);
1302                 if (!info->swapped)
1303                         list_del_init(&info->swaplist);
1304                 if (atomic_dec_and_test(&info->stop_eviction))
1305                         wake_up_var(&info->stop_eviction);
1306                 if (error)
1307                         break;
1308         }
1309         mutex_unlock(&shmem_swaplist_mutex);
1310
1311         return error;
1312 }
1313
1314 /*
1315  * Move the page from the page cache to the swap cache.
1316  */
1317 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
1318 {
1319         struct folio *folio = page_folio(page);
1320         struct shmem_inode_info *info;
1321         struct address_space *mapping;
1322         struct inode *inode;
1323         swp_entry_t swap;
1324         pgoff_t index;
1325
1326         /*
1327          * If /sys/kernel/mm/transparent_hugepage/shmem_enabled is "always" or
1328          * "force", drivers/gpu/drm/i915/gem/i915_gem_shmem.c gets huge pages,
1329          * and its shmem_writeback() needs them to be split when swapping.
1330          */
1331         if (PageTransCompound(page)) {
1332                 /* Ensure the subpages are still dirty */
1333                 SetPageDirty(page);
1334                 if (split_huge_page(page) < 0)
1335                         goto redirty;
1336                 ClearPageDirty(page);
1337         }
1338
1339         BUG_ON(!PageLocked(page));
1340         mapping = page->mapping;
1341         index = page->index;
1342         inode = mapping->host;
1343         info = SHMEM_I(inode);
1344         if (info->flags & VM_LOCKED)
1345                 goto redirty;
1346         if (!total_swap_pages)
1347                 goto redirty;
1348
1349         /*
1350          * Our capabilities prevent regular writeback or sync from ever calling
1351          * shmem_writepage; but a stacking filesystem might use ->writepage of
1352          * its underlying filesystem, in which case tmpfs should write out to
1353          * swap only in response to memory pressure, and not for the writeback
1354          * threads or sync.
1355          */
1356         if (!wbc->for_reclaim) {
1357                 WARN_ON_ONCE(1);        /* Still happens? Tell us about it! */
1358                 goto redirty;
1359         }
1360
1361         /*
1362          * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC
1363          * value into swapfile.c, the only way we can correctly account for a
1364          * fallocated page arriving here is now to initialize it and write it.
1365          *
1366          * That's okay for a page already fallocated earlier, but if we have
1367          * not yet completed the fallocation, then (a) we want to keep track
1368          * of this page in case we have to undo it, and (b) it may not be a
1369          * good idea to continue anyway, once we're pushing into swap.  So
1370          * reactivate the page, and let shmem_fallocate() quit when too many.
1371          */
1372         if (!PageUptodate(page)) {
1373                 if (inode->i_private) {
1374                         struct shmem_falloc *shmem_falloc;
1375                         spin_lock(&inode->i_lock);
1376                         shmem_falloc = inode->i_private;
1377                         if (shmem_falloc &&
1378                             !shmem_falloc->waitq &&
1379                             index >= shmem_falloc->start &&
1380                             index < shmem_falloc->next)
1381                                 shmem_falloc->nr_unswapped++;
1382                         else
1383                                 shmem_falloc = NULL;
1384                         spin_unlock(&inode->i_lock);
1385                         if (shmem_falloc)
1386                                 goto redirty;
1387                 }
1388                 clear_highpage(page);
1389                 flush_dcache_page(page);
1390                 SetPageUptodate(page);
1391         }
1392
1393         swap = folio_alloc_swap(folio);
1394         if (!swap.val)
1395                 goto redirty;
1396
1397         /*
1398          * Add inode to shmem_unuse()'s list of swapped-out inodes,
1399          * if it's not already there.  Do it now before the page is
1400          * moved to swap cache, when its pagelock no longer protects
1401          * the inode from eviction.  But don't unlock the mutex until
1402          * we've incremented swapped, because shmem_unuse_inode() will
1403          * prune a !swapped inode from the swaplist under this mutex.
1404          */
1405         mutex_lock(&shmem_swaplist_mutex);
1406         if (list_empty(&info->swaplist))
1407                 list_add(&info->swaplist, &shmem_swaplist);
1408
1409         if (add_to_swap_cache(page, swap,
1410                         __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN,
1411                         NULL) == 0) {
1412                 spin_lock_irq(&info->lock);
1413                 shmem_recalc_inode(inode);
1414                 info->swapped++;
1415                 spin_unlock_irq(&info->lock);
1416
1417                 swap_shmem_alloc(swap);
1418                 shmem_delete_from_page_cache(page, swp_to_radix_entry(swap));
1419
1420                 mutex_unlock(&shmem_swaplist_mutex);
1421                 BUG_ON(page_mapped(page));
1422                 swap_writepage(page, wbc);
1423                 return 0;
1424         }
1425
1426         mutex_unlock(&shmem_swaplist_mutex);
1427         put_swap_page(page, swap);
1428 redirty:
1429         set_page_dirty(page);
1430         if (wbc->for_reclaim)
1431                 return AOP_WRITEPAGE_ACTIVATE;  /* Return with page locked */
1432         unlock_page(page);
1433         return 0;
1434 }
1435
1436 #if defined(CONFIG_NUMA) && defined(CONFIG_TMPFS)
1437 static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
1438 {
1439         char buffer[64];
1440
1441         if (!mpol || mpol->mode == MPOL_DEFAULT)
1442                 return;         /* show nothing */
1443
1444         mpol_to_str(buffer, sizeof(buffer), mpol);
1445
1446         seq_printf(seq, ",mpol=%s", buffer);
1447 }
1448
1449 static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1450 {
1451         struct mempolicy *mpol = NULL;
1452         if (sbinfo->mpol) {
1453                 raw_spin_lock(&sbinfo->stat_lock);      /* prevent replace/use races */
1454                 mpol = sbinfo->mpol;
1455                 mpol_get(mpol);
1456                 raw_spin_unlock(&sbinfo->stat_lock);
1457         }
1458         return mpol;
1459 }
1460 #else /* !CONFIG_NUMA || !CONFIG_TMPFS */
1461 static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
1462 {
1463 }
1464 static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1465 {
1466         return NULL;
1467 }
1468 #endif /* CONFIG_NUMA && CONFIG_TMPFS */
1469 #ifndef CONFIG_NUMA
1470 #define vm_policy vm_private_data
1471 #endif
1472
1473 static void shmem_pseudo_vma_init(struct vm_area_struct *vma,
1474                 struct shmem_inode_info *info, pgoff_t index)
1475 {
1476         /* Create a pseudo vma that just contains the policy */
1477         vma_init(vma, NULL);
1478         /* Bias interleave by inode number to distribute better across nodes */
1479         vma->vm_pgoff = index + info->vfs_inode.i_ino;
1480         vma->vm_policy = mpol_shared_policy_lookup(&info->policy, index);
1481 }
1482
1483 static void shmem_pseudo_vma_destroy(struct vm_area_struct *vma)
1484 {
1485         /* Drop reference taken by mpol_shared_policy_lookup() */
1486         mpol_cond_put(vma->vm_policy);
1487 }
1488
1489 static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
1490                         struct shmem_inode_info *info, pgoff_t index)
1491 {
1492         struct vm_area_struct pvma;
1493         struct page *page;
1494         struct vm_fault vmf = {
1495                 .vma = &pvma,
1496         };
1497
1498         shmem_pseudo_vma_init(&pvma, info, index);
1499         page = swap_cluster_readahead(swap, gfp, &vmf);
1500         shmem_pseudo_vma_destroy(&pvma);
1501
1502         return page;
1503 }
1504
1505 /*
1506  * Make sure huge_gfp is always more limited than limit_gfp.
1507  * Some of the flags set permissions, while others set limitations.
1508  */
1509 static gfp_t limit_gfp_mask(gfp_t huge_gfp, gfp_t limit_gfp)
1510 {
1511         gfp_t allowflags = __GFP_IO | __GFP_FS | __GFP_RECLAIM;
1512         gfp_t denyflags = __GFP_NOWARN | __GFP_NORETRY;
1513         gfp_t zoneflags = limit_gfp & GFP_ZONEMASK;
1514         gfp_t result = huge_gfp & ~(allowflags | GFP_ZONEMASK);
1515
1516         /* Allow allocations only from the originally specified zones. */
1517         result |= zoneflags;
1518
1519         /*
1520          * Minimize the result gfp by taking the union with the deny flags,
1521          * and the intersection of the allow flags.
1522          */
1523         result |= (limit_gfp & denyflags);
1524         result |= (huge_gfp & limit_gfp) & allowflags;
1525
1526         return result;
1527 }
1528
1529 static struct folio *shmem_alloc_hugefolio(gfp_t gfp,
1530                 struct shmem_inode_info *info, pgoff_t index)
1531 {
1532         struct vm_area_struct pvma;
1533         struct address_space *mapping = info->vfs_inode.i_mapping;
1534         pgoff_t hindex;
1535         struct folio *folio;
1536
1537         hindex = round_down(index, HPAGE_PMD_NR);
1538         if (xa_find(&mapping->i_pages, &hindex, hindex + HPAGE_PMD_NR - 1,
1539                                                                 XA_PRESENT))
1540                 return NULL;
1541
1542         shmem_pseudo_vma_init(&pvma, info, hindex);
1543         folio = vma_alloc_folio(gfp, HPAGE_PMD_ORDER, &pvma, 0, true);
1544         shmem_pseudo_vma_destroy(&pvma);
1545         if (!folio)
1546                 count_vm_event(THP_FILE_FALLBACK);
1547         return folio;
1548 }
1549
1550 static struct folio *shmem_alloc_folio(gfp_t gfp,
1551                         struct shmem_inode_info *info, pgoff_t index)
1552 {
1553         struct vm_area_struct pvma;
1554         struct folio *folio;
1555
1556         shmem_pseudo_vma_init(&pvma, info, index);
1557         folio = vma_alloc_folio(gfp, 0, &pvma, 0, false);
1558         shmem_pseudo_vma_destroy(&pvma);
1559
1560         return folio;
1561 }
1562
1563 static struct page *shmem_alloc_page(gfp_t gfp,
1564                         struct shmem_inode_info *info, pgoff_t index)
1565 {
1566         return &shmem_alloc_folio(gfp, info, index)->page;
1567 }
1568
1569 static struct folio *shmem_alloc_and_acct_folio(gfp_t gfp, struct inode *inode,
1570                 pgoff_t index, bool huge)
1571 {
1572         struct shmem_inode_info *info = SHMEM_I(inode);
1573         struct folio *folio;
1574         int nr;
1575         int err = -ENOSPC;
1576
1577         if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
1578                 huge = false;
1579         nr = huge ? HPAGE_PMD_NR : 1;
1580
1581         if (!shmem_inode_acct_block(inode, nr))
1582                 goto failed;
1583
1584         if (huge)
1585                 folio = shmem_alloc_hugefolio(gfp, info, index);
1586         else
1587                 folio = shmem_alloc_folio(gfp, info, index);
1588         if (folio) {
1589                 __folio_set_locked(folio);
1590                 __folio_set_swapbacked(folio);
1591                 return folio;
1592         }
1593
1594         err = -ENOMEM;
1595         shmem_inode_unacct_blocks(inode, nr);
1596 failed:
1597         return ERR_PTR(err);
1598 }
1599
1600 /*
1601  * When a page is moved from swapcache to shmem filecache (either by the
1602  * usual swapin of shmem_getpage_gfp(), or by the less common swapoff of
1603  * shmem_unuse_inode()), it may have been read in earlier from swap, in
1604  * ignorance of the mapping it belongs to.  If that mapping has special
1605  * constraints (like the gma500 GEM driver, which requires RAM below 4GB),
1606  * we may need to copy to a suitable page before moving to filecache.
1607  *
1608  * In a future release, this may well be extended to respect cpuset and
1609  * NUMA mempolicy, and applied also to anonymous pages in do_swap_page();
1610  * but for now it is a simple matter of zone.
1611  */
1612 static bool shmem_should_replace_folio(struct folio *folio, gfp_t gfp)
1613 {
1614         return folio_zonenum(folio) > gfp_zone(gfp);
1615 }
1616
1617 static int shmem_replace_page(struct page **pagep, gfp_t gfp,
1618                                 struct shmem_inode_info *info, pgoff_t index)
1619 {
1620         struct page *oldpage, *newpage;
1621         struct folio *old, *new;
1622         struct address_space *swap_mapping;
1623         swp_entry_t entry;
1624         pgoff_t swap_index;
1625         int error;
1626
1627         oldpage = *pagep;
1628         entry.val = page_private(oldpage);
1629         swap_index = swp_offset(entry);
1630         swap_mapping = page_mapping(oldpage);
1631
1632         /*
1633          * We have arrived here because our zones are constrained, so don't
1634          * limit chance of success by further cpuset and node constraints.
1635          */
1636         gfp &= ~GFP_CONSTRAINT_MASK;
1637         newpage = shmem_alloc_page(gfp, info, index);
1638         if (!newpage)
1639                 return -ENOMEM;
1640
1641         get_page(newpage);
1642         copy_highpage(newpage, oldpage);
1643         flush_dcache_page(newpage);
1644
1645         __SetPageLocked(newpage);
1646         __SetPageSwapBacked(newpage);
1647         SetPageUptodate(newpage);
1648         set_page_private(newpage, entry.val);
1649         SetPageSwapCache(newpage);
1650
1651         /*
1652          * Our caller will very soon move newpage out of swapcache, but it's
1653          * a nice clean interface for us to replace oldpage by newpage there.
1654          */
1655         xa_lock_irq(&swap_mapping->i_pages);
1656         error = shmem_replace_entry(swap_mapping, swap_index, oldpage, newpage);
1657         if (!error) {
1658                 old = page_folio(oldpage);
1659                 new = page_folio(newpage);
1660                 mem_cgroup_migrate(old, new);
1661                 __inc_lruvec_page_state(newpage, NR_FILE_PAGES);
1662                 __inc_lruvec_page_state(newpage, NR_SHMEM);
1663                 __dec_lruvec_page_state(oldpage, NR_FILE_PAGES);
1664                 __dec_lruvec_page_state(oldpage, NR_SHMEM);
1665         }
1666         xa_unlock_irq(&swap_mapping->i_pages);
1667
1668         if (unlikely(error)) {
1669                 /*
1670                  * Is this possible?  I think not, now that our callers check
1671                  * both PageSwapCache and page_private after getting page lock;
1672                  * but be defensive.  Reverse old to newpage for clear and free.
1673                  */
1674                 oldpage = newpage;
1675         } else {
1676                 lru_cache_add(newpage);
1677                 *pagep = newpage;
1678         }
1679
1680         ClearPageSwapCache(oldpage);
1681         set_page_private(oldpage, 0);
1682
1683         unlock_page(oldpage);
1684         put_page(oldpage);
1685         put_page(oldpage);
1686         return error;
1687 }
1688
1689 static void shmem_set_folio_swapin_error(struct inode *inode, pgoff_t index,
1690                                          struct folio *folio, swp_entry_t swap)
1691 {
1692         struct address_space *mapping = inode->i_mapping;
1693         struct shmem_inode_info *info = SHMEM_I(inode);
1694         swp_entry_t swapin_error;
1695         void *old;
1696
1697         swapin_error = make_swapin_error_entry(&folio->page);
1698         old = xa_cmpxchg_irq(&mapping->i_pages, index,
1699                              swp_to_radix_entry(swap),
1700                              swp_to_radix_entry(swapin_error), 0);
1701         if (old != swp_to_radix_entry(swap))
1702                 return;
1703
1704         folio_wait_writeback(folio);
1705         delete_from_swap_cache(folio);
1706         spin_lock_irq(&info->lock);
1707         /*
1708          * Don't treat swapin error folio as alloced. Otherwise inode->i_blocks won't
1709          * be 0 when inode is released and thus trigger WARN_ON(inode->i_blocks) in
1710          * shmem_evict_inode.
1711          */
1712         info->alloced--;
1713         info->swapped--;
1714         shmem_recalc_inode(inode);
1715         spin_unlock_irq(&info->lock);
1716         swap_free(swap);
1717 }
1718
1719 /*
1720  * Swap in the folio pointed to by *foliop.
1721  * Caller has to make sure that *foliop contains a valid swapped folio.
1722  * Returns 0 and the folio in foliop if success. On failure, returns the
1723  * error code and NULL in *foliop.
1724  */
1725 static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
1726                              struct folio **foliop, enum sgp_type sgp,
1727                              gfp_t gfp, struct vm_area_struct *vma,
1728                              vm_fault_t *fault_type)
1729 {
1730         struct address_space *mapping = inode->i_mapping;
1731         struct shmem_inode_info *info = SHMEM_I(inode);
1732         struct mm_struct *charge_mm = vma ? vma->vm_mm : NULL;
1733         struct page *page;
1734         struct folio *folio = NULL;
1735         swp_entry_t swap;
1736         int error;
1737
1738         VM_BUG_ON(!*foliop || !xa_is_value(*foliop));
1739         swap = radix_to_swp_entry(*foliop);
1740         *foliop = NULL;
1741
1742         if (is_swapin_error_entry(swap))
1743                 return -EIO;
1744
1745         /* Look it up and read it in.. */
1746         page = lookup_swap_cache(swap, NULL, 0);
1747         if (!page) {
1748                 /* Or update major stats only when swapin succeeds?? */
1749                 if (fault_type) {
1750                         *fault_type |= VM_FAULT_MAJOR;
1751                         count_vm_event(PGMAJFAULT);
1752                         count_memcg_event_mm(charge_mm, PGMAJFAULT);
1753                 }
1754                 /* Here we actually start the io */
1755                 page = shmem_swapin(swap, gfp, info, index);
1756                 if (!page) {
1757                         error = -ENOMEM;
1758                         goto failed;
1759                 }
1760         }
1761         folio = page_folio(page);
1762
1763         /* We have to do this with folio locked to prevent races */
1764         folio_lock(folio);
1765         if (!folio_test_swapcache(folio) ||
1766             folio_swap_entry(folio).val != swap.val ||
1767             !shmem_confirm_swap(mapping, index, swap)) {
1768                 error = -EEXIST;
1769                 goto unlock;
1770         }
1771         if (!folio_test_uptodate(folio)) {
1772                 error = -EIO;
1773                 goto failed;
1774         }
1775         folio_wait_writeback(folio);
1776
1777         /*
1778          * Some architectures may have to restore extra metadata to the
1779          * folio after reading from swap.
1780          */
1781         arch_swap_restore(swap, folio);
1782
1783         if (shmem_should_replace_folio(folio, gfp)) {
1784                 error = shmem_replace_page(&page, gfp, info, index);
1785                 folio = page_folio(page);
1786                 if (error)
1787                         goto failed;
1788         }
1789
1790         error = shmem_add_to_page_cache(folio, mapping, index,
1791                                         swp_to_radix_entry(swap), gfp,
1792                                         charge_mm);
1793         if (error)
1794                 goto failed;
1795
1796         spin_lock_irq(&info->lock);
1797         info->swapped--;
1798         shmem_recalc_inode(inode);
1799         spin_unlock_irq(&info->lock);
1800
1801         if (sgp == SGP_WRITE)
1802                 folio_mark_accessed(folio);
1803
1804         delete_from_swap_cache(folio);
1805         folio_mark_dirty(folio);
1806         swap_free(swap);
1807
1808         *foliop = folio;
1809         return 0;
1810 failed:
1811         if (!shmem_confirm_swap(mapping, index, swap))
1812                 error = -EEXIST;
1813         if (error == -EIO)
1814                 shmem_set_folio_swapin_error(inode, index, folio, swap);
1815 unlock:
1816         if (folio) {
1817                 folio_unlock(folio);
1818                 folio_put(folio);
1819         }
1820
1821         return error;
1822 }
1823
1824 /*
1825  * shmem_getpage_gfp - find page in cache, or get from swap, or allocate
1826  *
1827  * If we allocate a new one we do not mark it dirty. That's up to the
1828  * vm. If we swap it in we mark it dirty since we also free the swap
1829  * entry since a page cannot live in both the swap and page cache.
1830  *
1831  * vma, vmf, and fault_type are only supplied by shmem_fault:
1832  * otherwise they are NULL.
1833  */
1834 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
1835         struct page **pagep, enum sgp_type sgp, gfp_t gfp,
1836         struct vm_area_struct *vma, struct vm_fault *vmf,
1837                         vm_fault_t *fault_type)
1838 {
1839         struct address_space *mapping = inode->i_mapping;
1840         struct shmem_inode_info *info = SHMEM_I(inode);
1841         struct shmem_sb_info *sbinfo;
1842         struct mm_struct *charge_mm;
1843         struct folio *folio;
1844         pgoff_t hindex = index;
1845         gfp_t huge_gfp;
1846         int error;
1847         int once = 0;
1848         int alloced = 0;
1849
1850         if (index > (MAX_LFS_FILESIZE >> PAGE_SHIFT))
1851                 return -EFBIG;
1852 repeat:
1853         if (sgp <= SGP_CACHE &&
1854             ((loff_t)index << PAGE_SHIFT) >= i_size_read(inode)) {
1855                 return -EINVAL;
1856         }
1857
1858         sbinfo = SHMEM_SB(inode->i_sb);
1859         charge_mm = vma ? vma->vm_mm : NULL;
1860
1861         folio = __filemap_get_folio(mapping, index, FGP_ENTRY | FGP_LOCK, 0);
1862         if (folio && vma && userfaultfd_minor(vma)) {
1863                 if (!xa_is_value(folio)) {
1864                         folio_unlock(folio);
1865                         folio_put(folio);
1866                 }
1867                 *fault_type = handle_userfault(vmf, VM_UFFD_MINOR);
1868                 return 0;
1869         }
1870
1871         if (xa_is_value(folio)) {
1872                 error = shmem_swapin_folio(inode, index, &folio,
1873                                           sgp, gfp, vma, fault_type);
1874                 if (error == -EEXIST)
1875                         goto repeat;
1876
1877                 *pagep = &folio->page;
1878                 return error;
1879         }
1880
1881         if (folio) {
1882                 hindex = folio->index;
1883                 if (sgp == SGP_WRITE)
1884                         folio_mark_accessed(folio);
1885                 if (folio_test_uptodate(folio))
1886                         goto out;
1887                 /* fallocated page */
1888                 if (sgp != SGP_READ)
1889                         goto clear;
1890                 folio_unlock(folio);
1891                 folio_put(folio);
1892         }
1893
1894         /*
1895          * SGP_READ: succeed on hole, with NULL page, letting caller zero.
1896          * SGP_NOALLOC: fail on hole, with NULL page, letting caller fail.
1897          */
1898         *pagep = NULL;
1899         if (sgp == SGP_READ)
1900                 return 0;
1901         if (sgp == SGP_NOALLOC)
1902                 return -ENOENT;
1903
1904         /*
1905          * Fast cache lookup and swap lookup did not find it: allocate.
1906          */
1907
1908         if (vma && userfaultfd_missing(vma)) {
1909                 *fault_type = handle_userfault(vmf, VM_UFFD_MISSING);
1910                 return 0;
1911         }
1912
1913         if (!shmem_is_huge(vma, inode, index))
1914                 goto alloc_nohuge;
1915
1916         huge_gfp = vma_thp_gfp_mask(vma);
1917         huge_gfp = limit_gfp_mask(huge_gfp, gfp);
1918         folio = shmem_alloc_and_acct_folio(huge_gfp, inode, index, true);
1919         if (IS_ERR(folio)) {
1920 alloc_nohuge:
1921                 folio = shmem_alloc_and_acct_folio(gfp, inode, index, false);
1922         }
1923         if (IS_ERR(folio)) {
1924                 int retry = 5;
1925
1926                 error = PTR_ERR(folio);
1927                 folio = NULL;
1928                 if (error != -ENOSPC)
1929                         goto unlock;
1930                 /*
1931                  * Try to reclaim some space by splitting a huge page
1932                  * beyond i_size on the filesystem.
1933                  */
1934                 while (retry--) {
1935                         int ret;
1936
1937                         ret = shmem_unused_huge_shrink(sbinfo, NULL, 1);
1938                         if (ret == SHRINK_STOP)
1939                                 break;
1940                         if (ret)
1941                                 goto alloc_nohuge;
1942                 }
1943                 goto unlock;
1944         }
1945
1946         hindex = round_down(index, folio_nr_pages(folio));
1947
1948         if (sgp == SGP_WRITE)
1949                 __folio_set_referenced(folio);
1950
1951         error = shmem_add_to_page_cache(folio, mapping, hindex,
1952                                         NULL, gfp & GFP_RECLAIM_MASK,
1953                                         charge_mm);
1954         if (error)
1955                 goto unacct;
1956         folio_add_lru(folio);
1957
1958         spin_lock_irq(&info->lock);
1959         info->alloced += folio_nr_pages(folio);
1960         inode->i_blocks += (blkcnt_t)BLOCKS_PER_PAGE << folio_order(folio);
1961         shmem_recalc_inode(inode);
1962         spin_unlock_irq(&info->lock);
1963         alloced = true;
1964
1965         if (folio_test_pmd_mappable(folio) &&
1966             DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE) <
1967                         hindex + HPAGE_PMD_NR - 1) {
1968                 /*
1969                  * Part of the huge page is beyond i_size: subject
1970                  * to shrink under memory pressure.
1971                  */
1972                 spin_lock(&sbinfo->shrinklist_lock);
1973                 /*
1974                  * _careful to defend against unlocked access to
1975                  * ->shrink_list in shmem_unused_huge_shrink()
1976                  */
1977                 if (list_empty_careful(&info->shrinklist)) {
1978                         list_add_tail(&info->shrinklist,
1979                                       &sbinfo->shrinklist);
1980                         sbinfo->shrinklist_len++;
1981                 }
1982                 spin_unlock(&sbinfo->shrinklist_lock);
1983         }
1984
1985         /*
1986          * Let SGP_FALLOC use the SGP_WRITE optimization on a new page.
1987          */
1988         if (sgp == SGP_FALLOC)
1989                 sgp = SGP_WRITE;
1990 clear:
1991         /*
1992          * Let SGP_WRITE caller clear ends if write does not fill page;
1993          * but SGP_FALLOC on a page fallocated earlier must initialize
1994          * it now, lest undo on failure cancel our earlier guarantee.
1995          */
1996         if (sgp != SGP_WRITE && !folio_test_uptodate(folio)) {
1997                 long i, n = folio_nr_pages(folio);
1998
1999                 for (i = 0; i < n; i++)
2000                         clear_highpage(folio_page(folio, i));
2001                 flush_dcache_folio(folio);
2002                 folio_mark_uptodate(folio);
2003         }
2004
2005         /* Perhaps the file has been truncated since we checked */
2006         if (sgp <= SGP_CACHE &&
2007             ((loff_t)index << PAGE_SHIFT) >= i_size_read(inode)) {
2008                 if (alloced) {
2009                         folio_clear_dirty(folio);
2010                         filemap_remove_folio(folio);
2011                         spin_lock_irq(&info->lock);
2012                         shmem_recalc_inode(inode);
2013                         spin_unlock_irq(&info->lock);
2014                 }
2015                 error = -EINVAL;
2016                 goto unlock;
2017         }
2018 out:
2019         *pagep = folio_page(folio, index - hindex);
2020         return 0;
2021
2022         /*
2023          * Error recovery.
2024          */
2025 unacct:
2026         shmem_inode_unacct_blocks(inode, folio_nr_pages(folio));
2027
2028         if (folio_test_large(folio)) {
2029                 folio_unlock(folio);
2030                 folio_put(folio);
2031                 goto alloc_nohuge;
2032         }
2033 unlock:
2034         if (folio) {
2035                 folio_unlock(folio);
2036                 folio_put(folio);
2037         }
2038         if (error == -ENOSPC && !once++) {
2039                 spin_lock_irq(&info->lock);
2040                 shmem_recalc_inode(inode);
2041                 spin_unlock_irq(&info->lock);
2042                 goto repeat;
2043         }
2044         if (error == -EEXIST)
2045                 goto repeat;
2046         return error;
2047 }
2048
2049 /*
2050  * This is like autoremove_wake_function, but it removes the wait queue
2051  * entry unconditionally - even if something else had already woken the
2052  * target.
2053  */
2054 static int synchronous_wake_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
2055 {
2056         int ret = default_wake_function(wait, mode, sync, key);
2057         list_del_init(&wait->entry);
2058         return ret;
2059 }
2060
2061 static vm_fault_t shmem_fault(struct vm_fault *vmf)
2062 {
2063         struct vm_area_struct *vma = vmf->vma;
2064         struct inode *inode = file_inode(vma->vm_file);
2065         gfp_t gfp = mapping_gfp_mask(inode->i_mapping);
2066         int err;
2067         vm_fault_t ret = VM_FAULT_LOCKED;
2068
2069         /*
2070          * Trinity finds that probing a hole which tmpfs is punching can
2071          * prevent the hole-punch from ever completing: which in turn
2072          * locks writers out with its hold on i_rwsem.  So refrain from
2073          * faulting pages into the hole while it's being punched.  Although
2074          * shmem_undo_range() does remove the additions, it may be unable to
2075          * keep up, as each new page needs its own unmap_mapping_range() call,
2076          * and the i_mmap tree grows ever slower to scan if new vmas are added.
2077          *
2078          * It does not matter if we sometimes reach this check just before the
2079          * hole-punch begins, so that one fault then races with the punch:
2080          * we just need to make racing faults a rare case.
2081          *
2082          * The implementation below would be much simpler if we just used a
2083          * standard mutex or completion: but we cannot take i_rwsem in fault,
2084          * and bloating every shmem inode for this unlikely case would be sad.
2085          */
2086         if (unlikely(inode->i_private)) {
2087                 struct shmem_falloc *shmem_falloc;
2088
2089                 spin_lock(&inode->i_lock);
2090                 shmem_falloc = inode->i_private;
2091                 if (shmem_falloc &&
2092                     shmem_falloc->waitq &&
2093                     vmf->pgoff >= shmem_falloc->start &&
2094                     vmf->pgoff < shmem_falloc->next) {
2095                         struct file *fpin;
2096                         wait_queue_head_t *shmem_falloc_waitq;
2097                         DEFINE_WAIT_FUNC(shmem_fault_wait, synchronous_wake_function);
2098
2099                         ret = VM_FAULT_NOPAGE;
2100                         fpin = maybe_unlock_mmap_for_io(vmf, NULL);
2101                         if (fpin)
2102                                 ret = VM_FAULT_RETRY;
2103
2104                         shmem_falloc_waitq = shmem_falloc->waitq;
2105                         prepare_to_wait(shmem_falloc_waitq, &shmem_fault_wait,
2106                                         TASK_UNINTERRUPTIBLE);
2107                         spin_unlock(&inode->i_lock);
2108                         schedule();
2109
2110                         /*
2111                          * shmem_falloc_waitq points into the shmem_fallocate()
2112                          * stack of the hole-punching task: shmem_falloc_waitq
2113                          * is usually invalid by the time we reach here, but
2114                          * finish_wait() does not dereference it in that case;
2115                          * though i_lock needed lest racing with wake_up_all().
2116                          */
2117                         spin_lock(&inode->i_lock);
2118                         finish_wait(shmem_falloc_waitq, &shmem_fault_wait);
2119                         spin_unlock(&inode->i_lock);
2120
2121                         if (fpin)
2122                                 fput(fpin);
2123                         return ret;
2124                 }
2125                 spin_unlock(&inode->i_lock);
2126         }
2127
2128         err = shmem_getpage_gfp(inode, vmf->pgoff, &vmf->page, SGP_CACHE,
2129                                   gfp, vma, vmf, &ret);
2130         if (err)
2131                 return vmf_error(err);
2132         return ret;
2133 }
2134
2135 unsigned long shmem_get_unmapped_area(struct file *file,
2136                                       unsigned long uaddr, unsigned long len,
2137                                       unsigned long pgoff, unsigned long flags)
2138 {
2139         unsigned long (*get_area)(struct file *,
2140                 unsigned long, unsigned long, unsigned long, unsigned long);
2141         unsigned long addr;
2142         unsigned long offset;
2143         unsigned long inflated_len;
2144         unsigned long inflated_addr;
2145         unsigned long inflated_offset;
2146
2147         if (len > TASK_SIZE)
2148                 return -ENOMEM;
2149
2150         get_area = current->mm->get_unmapped_area;
2151         addr = get_area(file, uaddr, len, pgoff, flags);
2152
2153         if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
2154                 return addr;
2155         if (IS_ERR_VALUE(addr))
2156                 return addr;
2157         if (addr & ~PAGE_MASK)
2158                 return addr;
2159         if (addr > TASK_SIZE - len)
2160                 return addr;
2161
2162         if (shmem_huge == SHMEM_HUGE_DENY)
2163                 return addr;
2164         if (len < HPAGE_PMD_SIZE)
2165                 return addr;
2166         if (flags & MAP_FIXED)
2167                 return addr;
2168         /*
2169          * Our priority is to support MAP_SHARED mapped hugely;
2170          * and support MAP_PRIVATE mapped hugely too, until it is COWed.
2171          * But if caller specified an address hint and we allocated area there
2172          * successfully, respect that as before.
2173          */
2174         if (uaddr == addr)
2175                 return addr;
2176
2177         if (shmem_huge != SHMEM_HUGE_FORCE) {
2178                 struct super_block *sb;
2179
2180                 if (file) {
2181                         VM_BUG_ON(file->f_op != &shmem_file_operations);
2182                         sb = file_inode(file)->i_sb;
2183                 } else {
2184                         /*
2185                          * Called directly from mm/mmap.c, or drivers/char/mem.c
2186                          * for "/dev/zero", to create a shared anonymous object.
2187                          */
2188                         if (IS_ERR(shm_mnt))
2189                                 return addr;
2190                         sb = shm_mnt->mnt_sb;
2191                 }
2192                 if (SHMEM_SB(sb)->huge == SHMEM_HUGE_NEVER)
2193                         return addr;
2194         }
2195
2196         offset = (pgoff << PAGE_SHIFT) & (HPAGE_PMD_SIZE-1);
2197         if (offset && offset + len < 2 * HPAGE_PMD_SIZE)
2198                 return addr;
2199         if ((addr & (HPAGE_PMD_SIZE-1)) == offset)
2200                 return addr;
2201
2202         inflated_len = len + HPAGE_PMD_SIZE - PAGE_SIZE;
2203         if (inflated_len > TASK_SIZE)
2204                 return addr;
2205         if (inflated_len < len)
2206                 return addr;
2207
2208         inflated_addr = get_area(NULL, uaddr, inflated_len, 0, flags);
2209         if (IS_ERR_VALUE(inflated_addr))
2210                 return addr;
2211         if (inflated_addr & ~PAGE_MASK)
2212                 return addr;
2213
2214         inflated_offset = inflated_addr & (HPAGE_PMD_SIZE-1);
2215         inflated_addr += offset - inflated_offset;
2216         if (inflated_offset > offset)
2217                 inflated_addr += HPAGE_PMD_SIZE;
2218
2219         if (inflated_addr > TASK_SIZE - len)
2220                 return addr;
2221         return inflated_addr;
2222 }
2223
2224 #ifdef CONFIG_NUMA
2225 static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *mpol)
2226 {
2227         struct inode *inode = file_inode(vma->vm_file);
2228         return mpol_set_shared_policy(&SHMEM_I(inode)->policy, vma, mpol);
2229 }
2230
2231 static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
2232                                           unsigned long addr)
2233 {
2234         struct inode *inode = file_inode(vma->vm_file);
2235         pgoff_t index;
2236
2237         index = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
2238         return mpol_shared_policy_lookup(&SHMEM_I(inode)->policy, index);
2239 }
2240 #endif
2241
2242 int shmem_lock(struct file *file, int lock, struct ucounts *ucounts)
2243 {
2244         struct inode *inode = file_inode(file);
2245         struct shmem_inode_info *info = SHMEM_I(inode);
2246         int retval = -ENOMEM;
2247
2248         /*
2249          * What serializes the accesses to info->flags?
2250          * ipc_lock_object() when called from shmctl_do_lock(),
2251          * no serialization needed when called from shm_destroy().
2252          */
2253         if (lock && !(info->flags & VM_LOCKED)) {
2254                 if (!user_shm_lock(inode->i_size, ucounts))
2255                         goto out_nomem;
2256                 info->flags |= VM_LOCKED;
2257                 mapping_set_unevictable(file->f_mapping);
2258         }
2259         if (!lock && (info->flags & VM_LOCKED) && ucounts) {
2260                 user_shm_unlock(inode->i_size, ucounts);
2261                 info->flags &= ~VM_LOCKED;
2262                 mapping_clear_unevictable(file->f_mapping);
2263         }
2264         retval = 0;
2265
2266 out_nomem:
2267         return retval;
2268 }
2269
2270 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
2271 {
2272         struct shmem_inode_info *info = SHMEM_I(file_inode(file));
2273         int ret;
2274
2275         ret = seal_check_future_write(info->seals, vma);
2276         if (ret)
2277                 return ret;
2278
2279         /* arm64 - allow memory tagging on RAM-based files */
2280         vma->vm_flags |= VM_MTE_ALLOWED;
2281
2282         file_accessed(file);
2283         vma->vm_ops = &shmem_vm_ops;
2284         return 0;
2285 }
2286
2287 #ifdef CONFIG_TMPFS_XATTR
2288 static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
2289
2290 /*
2291  * chattr's fsflags are unrelated to extended attributes,
2292  * but tmpfs has chosen to enable them under the same config option.
2293  */
2294 static void shmem_set_inode_flags(struct inode *inode, unsigned int fsflags)
2295 {
2296         unsigned int i_flags = 0;
2297
2298         if (fsflags & FS_NOATIME_FL)
2299                 i_flags |= S_NOATIME;
2300         if (fsflags & FS_APPEND_FL)
2301                 i_flags |= S_APPEND;
2302         if (fsflags & FS_IMMUTABLE_FL)
2303                 i_flags |= S_IMMUTABLE;
2304         /*
2305          * But FS_NODUMP_FL does not require any action in i_flags.
2306          */
2307         inode_set_flags(inode, i_flags, S_NOATIME | S_APPEND | S_IMMUTABLE);
2308 }
2309 #else
2310 static void shmem_set_inode_flags(struct inode *inode, unsigned int fsflags)
2311 {
2312 }
2313 #define shmem_initxattrs NULL
2314 #endif
2315
2316 static struct inode *shmem_get_inode(struct super_block *sb, struct inode *dir,
2317                                      umode_t mode, dev_t dev, unsigned long flags)
2318 {
2319         struct inode *inode;
2320         struct shmem_inode_info *info;
2321         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2322         ino_t ino;
2323
2324         if (shmem_reserve_inode(sb, &ino))
2325                 return NULL;
2326
2327         inode = new_inode(sb);
2328         if (inode) {
2329                 inode->i_ino = ino;
2330                 inode_init_owner(&init_user_ns, inode, dir, mode);
2331                 inode->i_blocks = 0;
2332                 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
2333                 inode->i_generation = prandom_u32();
2334                 info = SHMEM_I(inode);
2335                 memset(info, 0, (char *)inode - (char *)info);
2336                 spin_lock_init(&info->lock);
2337                 atomic_set(&info->stop_eviction, 0);
2338                 info->seals = F_SEAL_SEAL;
2339                 info->flags = flags & VM_NORESERVE;
2340                 info->i_crtime = inode->i_mtime;
2341                 info->fsflags = (dir == NULL) ? 0 :
2342                         SHMEM_I(dir)->fsflags & SHMEM_FL_INHERITED;
2343                 if (info->fsflags)
2344                         shmem_set_inode_flags(inode, info->fsflags);
2345                 INIT_LIST_HEAD(&info->shrinklist);
2346                 INIT_LIST_HEAD(&info->swaplist);
2347                 simple_xattrs_init(&info->xattrs);
2348                 cache_no_acl(inode);
2349                 mapping_set_large_folios(inode->i_mapping);
2350
2351                 switch (mode & S_IFMT) {
2352                 default:
2353                         inode->i_op = &shmem_special_inode_operations;
2354                         init_special_inode(inode, mode, dev);
2355                         break;
2356                 case S_IFREG:
2357                         inode->i_mapping->a_ops = &shmem_aops;
2358                         inode->i_op = &shmem_inode_operations;
2359                         inode->i_fop = &shmem_file_operations;
2360                         mpol_shared_policy_init(&info->policy,
2361                                                  shmem_get_sbmpol(sbinfo));
2362                         break;
2363                 case S_IFDIR:
2364                         inc_nlink(inode);
2365                         /* Some things misbehave if size == 0 on a directory */
2366                         inode->i_size = 2 * BOGO_DIRENT_SIZE;
2367                         inode->i_op = &shmem_dir_inode_operations;
2368                         inode->i_fop = &simple_dir_operations;
2369                         break;
2370                 case S_IFLNK:
2371                         /*
2372                          * Must not load anything in the rbtree,
2373                          * mpol_free_shared_policy will not be called.
2374                          */
2375                         mpol_shared_policy_init(&info->policy, NULL);
2376                         break;
2377                 }
2378
2379                 lockdep_annotate_inode_mutex_key(inode);
2380         } else
2381                 shmem_free_inode(sb);
2382         return inode;
2383 }
2384
2385 #ifdef CONFIG_USERFAULTFD
2386 int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
2387                            pmd_t *dst_pmd,
2388                            struct vm_area_struct *dst_vma,
2389                            unsigned long dst_addr,
2390                            unsigned long src_addr,
2391                            bool zeropage, bool wp_copy,
2392                            struct page **pagep)
2393 {
2394         struct inode *inode = file_inode(dst_vma->vm_file);
2395         struct shmem_inode_info *info = SHMEM_I(inode);
2396         struct address_space *mapping = inode->i_mapping;
2397         gfp_t gfp = mapping_gfp_mask(mapping);
2398         pgoff_t pgoff = linear_page_index(dst_vma, dst_addr);
2399         void *page_kaddr;
2400         struct folio *folio;
2401         struct page *page;
2402         int ret;
2403         pgoff_t max_off;
2404
2405         if (!shmem_inode_acct_block(inode, 1)) {
2406                 /*
2407                  * We may have got a page, returned -ENOENT triggering a retry,
2408                  * and now we find ourselves with -ENOMEM. Release the page, to
2409                  * avoid a BUG_ON in our caller.
2410                  */
2411                 if (unlikely(*pagep)) {
2412                         put_page(*pagep);
2413                         *pagep = NULL;
2414                 }
2415                 return -ENOMEM;
2416         }
2417
2418         if (!*pagep) {
2419                 ret = -ENOMEM;
2420                 page = shmem_alloc_page(gfp, info, pgoff);
2421                 if (!page)
2422                         goto out_unacct_blocks;
2423
2424                 if (!zeropage) {        /* COPY */
2425                         page_kaddr = kmap_atomic(page);
2426                         ret = copy_from_user(page_kaddr,
2427                                              (const void __user *)src_addr,
2428                                              PAGE_SIZE);
2429                         kunmap_atomic(page_kaddr);
2430
2431                         /* fallback to copy_from_user outside mmap_lock */
2432                         if (unlikely(ret)) {
2433                                 *pagep = page;
2434                                 ret = -ENOENT;
2435                                 /* don't free the page */
2436                                 goto out_unacct_blocks;
2437                         }
2438
2439                         flush_dcache_page(page);
2440                 } else {                /* ZEROPAGE */
2441                         clear_user_highpage(page, dst_addr);
2442                 }
2443         } else {
2444                 page = *pagep;
2445                 *pagep = NULL;
2446         }
2447
2448         VM_BUG_ON(PageLocked(page));
2449         VM_BUG_ON(PageSwapBacked(page));
2450         __SetPageLocked(page);
2451         __SetPageSwapBacked(page);
2452         __SetPageUptodate(page);
2453
2454         ret = -EFAULT;
2455         max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
2456         if (unlikely(pgoff >= max_off))
2457                 goto out_release;
2458
2459         folio = page_folio(page);
2460         ret = shmem_add_to_page_cache(folio, mapping, pgoff, NULL,
2461                                       gfp & GFP_RECLAIM_MASK, dst_mm);
2462         if (ret)
2463                 goto out_release;
2464
2465         ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
2466                                        page, true, wp_copy);
2467         if (ret)
2468                 goto out_delete_from_cache;
2469
2470         spin_lock_irq(&info->lock);
2471         info->alloced++;
2472         inode->i_blocks += BLOCKS_PER_PAGE;
2473         shmem_recalc_inode(inode);
2474         spin_unlock_irq(&info->lock);
2475
2476         unlock_page(page);
2477         return 0;
2478 out_delete_from_cache:
2479         delete_from_page_cache(page);
2480 out_release:
2481         unlock_page(page);
2482         put_page(page);
2483 out_unacct_blocks:
2484         shmem_inode_unacct_blocks(inode, 1);
2485         return ret;
2486 }
2487 #endif /* CONFIG_USERFAULTFD */
2488
2489 #ifdef CONFIG_TMPFS
2490 static const struct inode_operations shmem_symlink_inode_operations;
2491 static const struct inode_operations shmem_short_symlink_operations;
2492
2493 static int
2494 shmem_write_begin(struct file *file, struct address_space *mapping,
2495                         loff_t pos, unsigned len,
2496                         struct page **pagep, void **fsdata)
2497 {
2498         struct inode *inode = mapping->host;
2499         struct shmem_inode_info *info = SHMEM_I(inode);
2500         pgoff_t index = pos >> PAGE_SHIFT;
2501         int ret = 0;
2502
2503         /* i_rwsem is held by caller */
2504         if (unlikely(info->seals & (F_SEAL_GROW |
2505                                    F_SEAL_WRITE | F_SEAL_FUTURE_WRITE))) {
2506                 if (info->seals & (F_SEAL_WRITE | F_SEAL_FUTURE_WRITE))
2507                         return -EPERM;
2508                 if ((info->seals & F_SEAL_GROW) && pos + len > inode->i_size)
2509                         return -EPERM;
2510         }
2511
2512         ret = shmem_getpage(inode, index, pagep, SGP_WRITE);
2513
2514         if (ret)
2515                 return ret;
2516
2517         if (PageHWPoison(*pagep)) {
2518                 unlock_page(*pagep);
2519                 put_page(*pagep);
2520                 *pagep = NULL;
2521                 return -EIO;
2522         }
2523
2524         return 0;
2525 }
2526
2527 static int
2528 shmem_write_end(struct file *file, struct address_space *mapping,
2529                         loff_t pos, unsigned len, unsigned copied,
2530                         struct page *page, void *fsdata)
2531 {
2532         struct inode *inode = mapping->host;
2533
2534         if (pos + copied > inode->i_size)
2535                 i_size_write(inode, pos + copied);
2536
2537         if (!PageUptodate(page)) {
2538                 struct page *head = compound_head(page);
2539                 if (PageTransCompound(page)) {
2540                         int i;
2541
2542                         for (i = 0; i < HPAGE_PMD_NR; i++) {
2543                                 if (head + i == page)
2544                                         continue;
2545                                 clear_highpage(head + i);
2546                                 flush_dcache_page(head + i);
2547                         }
2548                 }
2549                 if (copied < PAGE_SIZE) {
2550                         unsigned from = pos & (PAGE_SIZE - 1);
2551                         zero_user_segments(page, 0, from,
2552                                         from + copied, PAGE_SIZE);
2553                 }
2554                 SetPageUptodate(head);
2555         }
2556         set_page_dirty(page);
2557         unlock_page(page);
2558         put_page(page);
2559
2560         return copied;
2561 }
2562
2563 static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
2564 {
2565         struct file *file = iocb->ki_filp;
2566         struct inode *inode = file_inode(file);
2567         struct address_space *mapping = inode->i_mapping;
2568         pgoff_t index;
2569         unsigned long offset;
2570         int error = 0;
2571         ssize_t retval = 0;
2572         loff_t *ppos = &iocb->ki_pos;
2573
2574         index = *ppos >> PAGE_SHIFT;
2575         offset = *ppos & ~PAGE_MASK;
2576
2577         for (;;) {
2578                 struct page *page = NULL;
2579                 pgoff_t end_index;
2580                 unsigned long nr, ret;
2581                 loff_t i_size = i_size_read(inode);
2582
2583                 end_index = i_size >> PAGE_SHIFT;
2584                 if (index > end_index)
2585                         break;
2586                 if (index == end_index) {
2587                         nr = i_size & ~PAGE_MASK;
2588                         if (nr <= offset)
2589                                 break;
2590                 }
2591
2592                 error = shmem_getpage(inode, index, &page, SGP_READ);
2593                 if (error) {
2594                         if (error == -EINVAL)
2595                                 error = 0;
2596                         break;
2597                 }
2598                 if (page) {
2599                         unlock_page(page);
2600
2601                         if (PageHWPoison(page)) {
2602                                 put_page(page);
2603                                 error = -EIO;
2604                                 break;
2605                         }
2606                 }
2607
2608                 /*
2609                  * We must evaluate after, since reads (unlike writes)
2610                  * are called without i_rwsem protection against truncate
2611                  */
2612                 nr = PAGE_SIZE;
2613                 i_size = i_size_read(inode);
2614                 end_index = i_size >> PAGE_SHIFT;
2615                 if (index == end_index) {
2616                         nr = i_size & ~PAGE_MASK;
2617                         if (nr <= offset) {
2618                                 if (page)
2619                                         put_page(page);
2620                                 break;
2621                         }
2622                 }
2623                 nr -= offset;
2624
2625                 if (page) {
2626                         /*
2627                          * If users can be writing to this page using arbitrary
2628                          * virtual addresses, take care about potential aliasing
2629                          * before reading the page on the kernel side.
2630                          */
2631                         if (mapping_writably_mapped(mapping))
2632                                 flush_dcache_page(page);
2633                         /*
2634                          * Mark the page accessed if we read the beginning.
2635                          */
2636                         if (!offset)
2637                                 mark_page_accessed(page);
2638                         /*
2639                          * Ok, we have the page, and it's up-to-date, so
2640                          * now we can copy it to user space...
2641                          */
2642                         ret = copy_page_to_iter(page, offset, nr, to);
2643                         put_page(page);
2644
2645                 } else if (user_backed_iter(to)) {
2646                         /*
2647                          * Copy to user tends to be so well optimized, but
2648                          * clear_user() not so much, that it is noticeably
2649                          * faster to copy the zero page instead of clearing.
2650                          */
2651                         ret = copy_page_to_iter(ZERO_PAGE(0), offset, nr, to);
2652                 } else {
2653                         /*
2654                          * But submitting the same page twice in a row to
2655                          * splice() - or others? - can result in confusion:
2656                          * so don't attempt that optimization on pipes etc.
2657                          */
2658                         ret = iov_iter_zero(nr, to);
2659                 }
2660
2661                 retval += ret;
2662                 offset += ret;
2663                 index += offset >> PAGE_SHIFT;
2664                 offset &= ~PAGE_MASK;
2665
2666                 if (!iov_iter_count(to))
2667                         break;
2668                 if (ret < nr) {
2669                         error = -EFAULT;
2670                         break;
2671                 }
2672                 cond_resched();
2673         }
2674
2675         *ppos = ((loff_t) index << PAGE_SHIFT) + offset;
2676         file_accessed(file);
2677         return retval ? retval : error;
2678 }
2679
2680 static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence)
2681 {
2682         struct address_space *mapping = file->f_mapping;
2683         struct inode *inode = mapping->host;
2684
2685         if (whence != SEEK_DATA && whence != SEEK_HOLE)
2686                 return generic_file_llseek_size(file, offset, whence,
2687                                         MAX_LFS_FILESIZE, i_size_read(inode));
2688         if (offset < 0)
2689                 return -ENXIO;
2690
2691         inode_lock(inode);
2692         /* We're holding i_rwsem so we can access i_size directly */
2693         offset = mapping_seek_hole_data(mapping, offset, inode->i_size, whence);
2694         if (offset >= 0)
2695                 offset = vfs_setpos(file, offset, MAX_LFS_FILESIZE);
2696         inode_unlock(inode);
2697         return offset;
2698 }
2699
2700 static long shmem_fallocate(struct file *file, int mode, loff_t offset,
2701                                                          loff_t len)
2702 {
2703         struct inode *inode = file_inode(file);
2704         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
2705         struct shmem_inode_info *info = SHMEM_I(inode);
2706         struct shmem_falloc shmem_falloc;
2707         pgoff_t start, index, end, undo_fallocend;
2708         int error;
2709
2710         if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
2711                 return -EOPNOTSUPP;
2712
2713         inode_lock(inode);
2714
2715         if (mode & FALLOC_FL_PUNCH_HOLE) {
2716                 struct address_space *mapping = file->f_mapping;
2717                 loff_t unmap_start = round_up(offset, PAGE_SIZE);
2718                 loff_t unmap_end = round_down(offset + len, PAGE_SIZE) - 1;
2719                 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(shmem_falloc_waitq);
2720
2721                 /* protected by i_rwsem */
2722                 if (info->seals & (F_SEAL_WRITE | F_SEAL_FUTURE_WRITE)) {
2723                         error = -EPERM;
2724                         goto out;
2725                 }
2726
2727                 shmem_falloc.waitq = &shmem_falloc_waitq;
2728                 shmem_falloc.start = (u64)unmap_start >> PAGE_SHIFT;
2729                 shmem_falloc.next = (unmap_end + 1) >> PAGE_SHIFT;
2730                 spin_lock(&inode->i_lock);
2731                 inode->i_private = &shmem_falloc;
2732                 spin_unlock(&inode->i_lock);
2733
2734                 if ((u64)unmap_end > (u64)unmap_start)
2735                         unmap_mapping_range(mapping, unmap_start,
2736                                             1 + unmap_end - unmap_start, 0);
2737                 shmem_truncate_range(inode, offset, offset + len - 1);
2738                 /* No need to unmap again: hole-punching leaves COWed pages */
2739
2740                 spin_lock(&inode->i_lock);
2741                 inode->i_private = NULL;
2742                 wake_up_all(&shmem_falloc_waitq);
2743                 WARN_ON_ONCE(!list_empty(&shmem_falloc_waitq.head));
2744                 spin_unlock(&inode->i_lock);
2745                 error = 0;
2746                 goto out;
2747         }
2748
2749         /* We need to check rlimit even when FALLOC_FL_KEEP_SIZE */
2750         error = inode_newsize_ok(inode, offset + len);
2751         if (error)
2752                 goto out;
2753
2754         if ((info->seals & F_SEAL_GROW) && offset + len > inode->i_size) {
2755                 error = -EPERM;
2756                 goto out;
2757         }
2758
2759         start = offset >> PAGE_SHIFT;
2760         end = (offset + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
2761         /* Try to avoid a swapstorm if len is impossible to satisfy */
2762         if (sbinfo->max_blocks && end - start > sbinfo->max_blocks) {
2763                 error = -ENOSPC;
2764                 goto out;
2765         }
2766
2767         shmem_falloc.waitq = NULL;
2768         shmem_falloc.start = start;
2769         shmem_falloc.next  = start;
2770         shmem_falloc.nr_falloced = 0;
2771         shmem_falloc.nr_unswapped = 0;
2772         spin_lock(&inode->i_lock);
2773         inode->i_private = &shmem_falloc;
2774         spin_unlock(&inode->i_lock);
2775
2776         /*
2777          * info->fallocend is only relevant when huge pages might be
2778          * involved: to prevent split_huge_page() freeing fallocated
2779          * pages when FALLOC_FL_KEEP_SIZE committed beyond i_size.
2780          */
2781         undo_fallocend = info->fallocend;
2782         if (info->fallocend < end)
2783                 info->fallocend = end;
2784
2785         for (index = start; index < end; ) {
2786                 struct page *page;
2787
2788                 /*
2789                  * Good, the fallocate(2) manpage permits EINTR: we may have
2790                  * been interrupted because we are using up too much memory.
2791                  */
2792                 if (signal_pending(current))
2793                         error = -EINTR;
2794                 else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
2795                         error = -ENOMEM;
2796                 else
2797                         error = shmem_getpage(inode, index, &page, SGP_FALLOC);
2798                 if (error) {
2799                         info->fallocend = undo_fallocend;
2800                         /* Remove the !PageUptodate pages we added */
2801                         if (index > start) {
2802                                 shmem_undo_range(inode,
2803                                     (loff_t)start << PAGE_SHIFT,
2804                                     ((loff_t)index << PAGE_SHIFT) - 1, true);
2805                         }
2806                         goto undone;
2807                 }
2808
2809                 index++;
2810                 /*
2811                  * Here is a more important optimization than it appears:
2812                  * a second SGP_FALLOC on the same huge page will clear it,
2813                  * making it PageUptodate and un-undoable if we fail later.
2814                  */
2815                 if (PageTransCompound(page)) {
2816                         index = round_up(index, HPAGE_PMD_NR);
2817                         /* Beware 32-bit wraparound */
2818                         if (!index)
2819                                 index--;
2820                 }
2821
2822                 /*
2823                  * Inform shmem_writepage() how far we have reached.
2824                  * No need for lock or barrier: we have the page lock.
2825                  */
2826                 if (!PageUptodate(page))
2827                         shmem_falloc.nr_falloced += index - shmem_falloc.next;
2828                 shmem_falloc.next = index;
2829
2830                 /*
2831                  * If !PageUptodate, leave it that way so that freeable pages
2832                  * can be recognized if we need to rollback on error later.
2833                  * But set_page_dirty so that memory pressure will swap rather
2834                  * than free the pages we are allocating (and SGP_CACHE pages
2835                  * might still be clean: we now need to mark those dirty too).
2836                  */
2837                 set_page_dirty(page);
2838                 unlock_page(page);
2839                 put_page(page);
2840                 cond_resched();
2841         }
2842
2843         if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
2844                 i_size_write(inode, offset + len);
2845 undone:
2846         spin_lock(&inode->i_lock);
2847         inode->i_private = NULL;
2848         spin_unlock(&inode->i_lock);
2849 out:
2850         if (!error)
2851                 file_modified(file);
2852         inode_unlock(inode);
2853         return error;
2854 }
2855
2856 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
2857 {
2858         struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
2859
2860         buf->f_type = TMPFS_MAGIC;
2861         buf->f_bsize = PAGE_SIZE;
2862         buf->f_namelen = NAME_MAX;
2863         if (sbinfo->max_blocks) {
2864                 buf->f_blocks = sbinfo->max_blocks;
2865                 buf->f_bavail =
2866                 buf->f_bfree  = sbinfo->max_blocks -
2867                                 percpu_counter_sum(&sbinfo->used_blocks);
2868         }
2869         if (sbinfo->max_inodes) {
2870                 buf->f_files = sbinfo->max_inodes;
2871                 buf->f_ffree = sbinfo->free_inodes;
2872         }
2873         /* else leave those fields 0 like simple_statfs */
2874
2875         buf->f_fsid = uuid_to_fsid(dentry->d_sb->s_uuid.b);
2876
2877         return 0;
2878 }
2879
2880 /*
2881  * File creation. Allocate an inode, and we're done..
2882  */
2883 static int
2884 shmem_mknod(struct user_namespace *mnt_userns, struct inode *dir,
2885             struct dentry *dentry, umode_t mode, dev_t dev)
2886 {
2887         struct inode *inode;
2888         int error = -ENOSPC;
2889
2890         inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
2891         if (inode) {
2892                 error = simple_acl_create(dir, inode);
2893                 if (error)
2894                         goto out_iput;
2895                 error = security_inode_init_security(inode, dir,
2896                                                      &dentry->d_name,
2897                                                      shmem_initxattrs, NULL);
2898                 if (error && error != -EOPNOTSUPP)
2899                         goto out_iput;
2900
2901                 error = 0;
2902                 dir->i_size += BOGO_DIRENT_SIZE;
2903                 dir->i_ctime = dir->i_mtime = current_time(dir);
2904                 d_instantiate(dentry, inode);
2905                 dget(dentry); /* Extra count - pin the dentry in core */
2906         }
2907         return error;
2908 out_iput:
2909         iput(inode);
2910         return error;
2911 }
2912
2913 static int
2914 shmem_tmpfile(struct user_namespace *mnt_userns, struct inode *dir,
2915               struct dentry *dentry, umode_t mode)
2916 {
2917         struct inode *inode;
2918         int error = -ENOSPC;
2919
2920         inode = shmem_get_inode(dir->i_sb, dir, mode, 0, VM_NORESERVE);
2921         if (inode) {
2922                 error = security_inode_init_security(inode, dir,
2923                                                      NULL,
2924                                                      shmem_initxattrs, NULL);
2925                 if (error && error != -EOPNOTSUPP)
2926                         goto out_iput;
2927                 error = simple_acl_create(dir, inode);
2928                 if (error)
2929                         goto out_iput;
2930                 d_tmpfile(dentry, inode);
2931         }
2932         return error;
2933 out_iput:
2934         iput(inode);
2935         return error;
2936 }
2937
2938 static int shmem_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
2939                        struct dentry *dentry, umode_t mode)
2940 {
2941         int error;
2942
2943         if ((error = shmem_mknod(&init_user_ns, dir, dentry,
2944                                  mode | S_IFDIR, 0)))
2945                 return error;
2946         inc_nlink(dir);
2947         return 0;
2948 }
2949
2950 static int shmem_create(struct user_namespace *mnt_userns, struct inode *dir,
2951                         struct dentry *dentry, umode_t mode, bool excl)
2952 {
2953         return shmem_mknod(&init_user_ns, dir, dentry, mode | S_IFREG, 0);
2954 }
2955
2956 /*
2957  * Link a file..
2958  */
2959 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
2960 {
2961         struct inode *inode = d_inode(old_dentry);
2962         int ret = 0;
2963
2964         /*
2965          * No ordinary (disk based) filesystem counts links as inodes;
2966          * but each new link needs a new dentry, pinning lowmem, and
2967          * tmpfs dentries cannot be pruned until they are unlinked.
2968          * But if an O_TMPFILE file is linked into the tmpfs, the
2969          * first link must skip that, to get the accounting right.
2970          */
2971         if (inode->i_nlink) {
2972                 ret = shmem_reserve_inode(inode->i_sb, NULL);
2973                 if (ret)
2974                         goto out;
2975         }
2976
2977         dir->i_size += BOGO_DIRENT_SIZE;
2978         inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
2979         inc_nlink(inode);
2980         ihold(inode);   /* New dentry reference */
2981         dget(dentry);           /* Extra pinning count for the created dentry */
2982         d_instantiate(dentry, inode);
2983 out:
2984         return ret;
2985 }
2986
2987 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
2988 {
2989         struct inode *inode = d_inode(dentry);
2990
2991         if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
2992                 shmem_free_inode(inode->i_sb);
2993
2994         dir->i_size -= BOGO_DIRENT_SIZE;
2995         inode->i_ctime = dir->i_ctime = dir->i_mtime = current_time(inode);
2996         drop_nlink(inode);
2997         dput(dentry);   /* Undo the count from "create" - this does all the work */
2998         return 0;
2999 }
3000
3001 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
3002 {
3003         if (!simple_empty(dentry))
3004                 return -ENOTEMPTY;
3005
3006         drop_nlink(d_inode(dentry));
3007         drop_nlink(dir);
3008         return shmem_unlink(dir, dentry);
3009 }
3010
3011 static int shmem_whiteout(struct user_namespace *mnt_userns,
3012                           struct inode *old_dir, struct dentry *old_dentry)
3013 {
3014         struct dentry *whiteout;
3015         int error;
3016
3017         whiteout = d_alloc(old_dentry->d_parent, &old_dentry->d_name);
3018         if (!whiteout)
3019                 return -ENOMEM;
3020
3021         error = shmem_mknod(&init_user_ns, old_dir, whiteout,
3022                             S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV);
3023         dput(whiteout);
3024         if (error)
3025                 return error;
3026
3027         /*
3028          * Cheat and hash the whiteout while the old dentry is still in
3029          * place, instead of playing games with FS_RENAME_DOES_D_MOVE.
3030          *
3031          * d_lookup() will consistently find one of them at this point,
3032          * not sure which one, but that isn't even important.
3033          */
3034         d_rehash(whiteout);
3035         return 0;
3036 }
3037
3038 /*
3039  * The VFS layer already does all the dentry stuff for rename,
3040  * we just have to decrement the usage count for the target if
3041  * it exists so that the VFS layer correctly free's it when it
3042  * gets overwritten.
3043  */
3044 static int shmem_rename2(struct user_namespace *mnt_userns,
3045                          struct inode *old_dir, struct dentry *old_dentry,
3046                          struct inode *new_dir, struct dentry *new_dentry,
3047                          unsigned int flags)
3048 {
3049         struct inode *inode = d_inode(old_dentry);
3050         int they_are_dirs = S_ISDIR(inode->i_mode);
3051
3052         if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
3053                 return -EINVAL;
3054
3055         if (flags & RENAME_EXCHANGE)
3056                 return simple_rename_exchange(old_dir, old_dentry, new_dir, new_dentry);
3057
3058         if (!simple_empty(new_dentry))
3059                 return -ENOTEMPTY;
3060
3061         if (flags & RENAME_WHITEOUT) {
3062                 int error;
3063
3064                 error = shmem_whiteout(&init_user_ns, old_dir, old_dentry);
3065                 if (error)
3066                         return error;
3067         }
3068
3069         if (d_really_is_positive(new_dentry)) {
3070                 (void) shmem_unlink(new_dir, new_dentry);
3071                 if (they_are_dirs) {
3072                         drop_nlink(d_inode(new_dentry));
3073                         drop_nlink(old_dir);
3074                 }
3075         } else if (they_are_dirs) {
3076                 drop_nlink(old_dir);
3077                 inc_nlink(new_dir);
3078         }
3079
3080         old_dir->i_size -= BOGO_DIRENT_SIZE;
3081         new_dir->i_size += BOGO_DIRENT_SIZE;
3082         old_dir->i_ctime = old_dir->i_mtime =
3083         new_dir->i_ctime = new_dir->i_mtime =
3084         inode->i_ctime = current_time(old_dir);
3085         return 0;
3086 }
3087
3088 static int shmem_symlink(struct user_namespace *mnt_userns, struct inode *dir,
3089                          struct dentry *dentry, const char *symname)
3090 {
3091         int error;
3092         int len;
3093         struct inode *inode;
3094         struct page *page;
3095
3096         len = strlen(symname) + 1;
3097         if (len > PAGE_SIZE)
3098                 return -ENAMETOOLONG;
3099
3100         inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK | 0777, 0,
3101                                 VM_NORESERVE);
3102         if (!inode)
3103                 return -ENOSPC;
3104
3105         error = security_inode_init_security(inode, dir, &dentry->d_name,
3106                                              shmem_initxattrs, NULL);
3107         if (error && error != -EOPNOTSUPP) {
3108                 iput(inode);
3109                 return error;
3110         }
3111
3112         inode->i_size = len-1;
3113         if (len <= SHORT_SYMLINK_LEN) {
3114                 inode->i_link = kmemdup(symname, len, GFP_KERNEL);
3115                 if (!inode->i_link) {
3116                         iput(inode);
3117                         return -ENOMEM;
3118                 }
3119                 inode->i_op = &shmem_short_symlink_operations;
3120         } else {
3121                 inode_nohighmem(inode);
3122                 error = shmem_getpage(inode, 0, &page, SGP_WRITE);
3123                 if (error) {
3124                         iput(inode);
3125                         return error;
3126                 }
3127                 inode->i_mapping->a_ops = &shmem_aops;
3128                 inode->i_op = &shmem_symlink_inode_operations;
3129                 memcpy(page_address(page), symname, len);
3130                 SetPageUptodate(page);
3131                 set_page_dirty(page);
3132                 unlock_page(page);
3133                 put_page(page);
3134         }
3135         dir->i_size += BOGO_DIRENT_SIZE;
3136         dir->i_ctime = dir->i_mtime = current_time(dir);
3137         d_instantiate(dentry, inode);
3138         dget(dentry);
3139         return 0;
3140 }
3141
3142 static void shmem_put_link(void *arg)
3143 {
3144         mark_page_accessed(arg);
3145         put_page(arg);
3146 }
3147
3148 static const char *shmem_get_link(struct dentry *dentry,
3149                                   struct inode *inode,
3150                                   struct delayed_call *done)
3151 {
3152         struct page *page = NULL;
3153         int error;
3154         if (!dentry) {
3155                 page = find_get_page(inode->i_mapping, 0);
3156                 if (!page)
3157                         return ERR_PTR(-ECHILD);
3158                 if (PageHWPoison(page) ||
3159                     !PageUptodate(page)) {
3160                         put_page(page);
3161                         return ERR_PTR(-ECHILD);
3162                 }
3163         } else {
3164                 error = shmem_getpage(inode, 0, &page, SGP_READ);
3165                 if (error)
3166                         return ERR_PTR(error);
3167                 if (!page)
3168                         return ERR_PTR(-ECHILD);
3169                 if (PageHWPoison(page)) {
3170                         unlock_page(page);
3171                         put_page(page);
3172                         return ERR_PTR(-ECHILD);
3173                 }
3174                 unlock_page(page);
3175         }
3176         set_delayed_call(done, shmem_put_link, page);
3177         return page_address(page);
3178 }
3179
3180 #ifdef CONFIG_TMPFS_XATTR
3181
3182 static int shmem_fileattr_get(struct dentry *dentry, struct fileattr *fa)
3183 {
3184         struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
3185
3186         fileattr_fill_flags(fa, info->fsflags & SHMEM_FL_USER_VISIBLE);
3187
3188         return 0;
3189 }
3190
3191 static int shmem_fileattr_set(struct user_namespace *mnt_userns,
3192                               struct dentry *dentry, struct fileattr *fa)
3193 {
3194         struct inode *inode = d_inode(dentry);
3195         struct shmem_inode_info *info = SHMEM_I(inode);
3196
3197         if (fileattr_has_fsx(fa))
3198                 return -EOPNOTSUPP;
3199         if (fa->flags & ~SHMEM_FL_USER_MODIFIABLE)
3200                 return -EOPNOTSUPP;
3201
3202         info->fsflags = (info->fsflags & ~SHMEM_FL_USER_MODIFIABLE) |
3203                 (fa->flags & SHMEM_FL_USER_MODIFIABLE);
3204
3205         shmem_set_inode_flags(inode, info->fsflags);
3206         inode->i_ctime = current_time(inode);
3207         return 0;
3208 }
3209
3210 /*
3211  * Superblocks without xattr inode operations may get some security.* xattr
3212  * support from the LSM "for free". As soon as we have any other xattrs
3213  * like ACLs, we also need to implement the security.* handlers at
3214  * filesystem level, though.
3215  */
3216
3217 /*
3218  * Callback for security_inode_init_security() for acquiring xattrs.
3219  */
3220 static int shmem_initxattrs(struct inode *inode,
3221                             const struct xattr *xattr_array,
3222                             void *fs_info)
3223 {
3224         struct shmem_inode_info *info = SHMEM_I(inode);
3225         const struct xattr *xattr;
3226         struct simple_xattr *new_xattr;
3227         size_t len;
3228
3229         for (xattr = xattr_array; xattr->name != NULL; xattr++) {
3230                 new_xattr = simple_xattr_alloc(xattr->value, xattr->value_len);
3231                 if (!new_xattr)
3232                         return -ENOMEM;
3233
3234                 len = strlen(xattr->name) + 1;
3235                 new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
3236                                           GFP_KERNEL);
3237                 if (!new_xattr->name) {
3238                         kvfree(new_xattr);
3239                         return -ENOMEM;
3240                 }
3241
3242                 memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
3243                        XATTR_SECURITY_PREFIX_LEN);
3244                 memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
3245                        xattr->name, len);
3246
3247                 simple_xattr_list_add(&info->xattrs, new_xattr);
3248         }
3249
3250         return 0;
3251 }
3252
3253 static int shmem_xattr_handler_get(const struct xattr_handler *handler,
3254                                    struct dentry *unused, struct inode *inode,
3255                                    const char *name, void *buffer, size_t size)
3256 {
3257         struct shmem_inode_info *info = SHMEM_I(inode);
3258
3259         name = xattr_full_name(handler, name);
3260         return simple_xattr_get(&info->xattrs, name, buffer, size);
3261 }
3262
3263 static int shmem_xattr_handler_set(const struct xattr_handler *handler,
3264                                    struct user_namespace *mnt_userns,
3265                                    struct dentry *unused, struct inode *inode,
3266                                    const char *name, const void *value,
3267                                    size_t size, int flags)
3268 {
3269         struct shmem_inode_info *info = SHMEM_I(inode);
3270
3271         name = xattr_full_name(handler, name);
3272         return simple_xattr_set(&info->xattrs, name, value, size, flags, NULL);
3273 }
3274
3275 static const struct xattr_handler shmem_security_xattr_handler = {
3276         .prefix = XATTR_SECURITY_PREFIX,
3277         .get = shmem_xattr_handler_get,
3278         .set = shmem_xattr_handler_set,
3279 };
3280
3281 static const struct xattr_handler shmem_trusted_xattr_handler = {
3282         .prefix = XATTR_TRUSTED_PREFIX,
3283         .get = shmem_xattr_handler_get,
3284         .set = shmem_xattr_handler_set,
3285 };
3286
3287 static const struct xattr_handler *shmem_xattr_handlers[] = {
3288 #ifdef CONFIG_TMPFS_POSIX_ACL
3289         &posix_acl_access_xattr_handler,
3290         &posix_acl_default_xattr_handler,
3291 #endif
3292         &shmem_security_xattr_handler,
3293         &shmem_trusted_xattr_handler,
3294         NULL
3295 };
3296
3297 static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
3298 {
3299         struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
3300         return simple_xattr_list(d_inode(dentry), &info->xattrs, buffer, size);
3301 }
3302 #endif /* CONFIG_TMPFS_XATTR */
3303
3304 static const struct inode_operations shmem_short_symlink_operations = {
3305         .getattr        = shmem_getattr,
3306         .get_link       = simple_get_link,
3307 #ifdef CONFIG_TMPFS_XATTR
3308         .listxattr      = shmem_listxattr,
3309 #endif
3310 };
3311
3312 static const struct inode_operations shmem_symlink_inode_operations = {
3313         .getattr        = shmem_getattr,
3314         .get_link       = shmem_get_link,
3315 #ifdef CONFIG_TMPFS_XATTR
3316         .listxattr      = shmem_listxattr,
3317 #endif
3318 };
3319
3320 static struct dentry *shmem_get_parent(struct dentry *child)
3321 {
3322         return ERR_PTR(-ESTALE);
3323 }
3324
3325 static int shmem_match(struct inode *ino, void *vfh)
3326 {
3327         __u32 *fh = vfh;
3328         __u64 inum = fh[2];
3329         inum = (inum << 32) | fh[1];
3330         return ino->i_ino == inum && fh[0] == ino->i_generation;
3331 }
3332
3333 /* Find any alias of inode, but prefer a hashed alias */
3334 static struct dentry *shmem_find_alias(struct inode *inode)
3335 {
3336         struct dentry *alias = d_find_alias(inode);
3337
3338         return alias ?: d_find_any_alias(inode);
3339 }
3340
3341
3342 static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
3343                 struct fid *fid, int fh_len, int fh_type)
3344 {
3345         struct inode *inode;
3346         struct dentry *dentry = NULL;
3347         u64 inum;
3348
3349         if (fh_len < 3)
3350                 return NULL;
3351
3352         inum = fid->raw[2];
3353         inum = (inum << 32) | fid->raw[1];
3354
3355         inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
3356                         shmem_match, fid->raw);
3357         if (inode) {
3358                 dentry = shmem_find_alias(inode);
3359                 iput(inode);
3360         }
3361
3362         return dentry;
3363 }
3364
3365 static int shmem_encode_fh(struct inode *inode, __u32 *fh, int *len,
3366                                 struct inode *parent)
3367 {
3368         if (*len < 3) {
3369                 *len = 3;
3370                 return FILEID_INVALID;
3371         }
3372
3373         if (inode_unhashed(inode)) {
3374                 /* Unfortunately insert_inode_hash is not idempotent,
3375                  * so as we hash inodes here rather than at creation
3376                  * time, we need a lock to ensure we only try
3377                  * to do it once
3378                  */
3379                 static DEFINE_SPINLOCK(lock);
3380                 spin_lock(&lock);
3381                 if (inode_unhashed(inode))
3382                         __insert_inode_hash(inode,
3383                                             inode->i_ino + inode->i_generation);
3384                 spin_unlock(&lock);
3385         }
3386
3387         fh[0] = inode->i_generation;
3388         fh[1] = inode->i_ino;
3389         fh[2] = ((__u64)inode->i_ino) >> 32;
3390
3391         *len = 3;
3392         return 1;
3393 }
3394
3395 static const struct export_operations shmem_export_ops = {
3396         .get_parent     = shmem_get_parent,
3397         .encode_fh      = shmem_encode_fh,
3398         .fh_to_dentry   = shmem_fh_to_dentry,
3399 };
3400
3401 enum shmem_param {
3402         Opt_gid,
3403         Opt_huge,
3404         Opt_mode,
3405         Opt_mpol,
3406         Opt_nr_blocks,
3407         Opt_nr_inodes,
3408         Opt_size,
3409         Opt_uid,
3410         Opt_inode32,
3411         Opt_inode64,
3412 };
3413
3414 static const struct constant_table shmem_param_enums_huge[] = {
3415         {"never",       SHMEM_HUGE_NEVER },
3416         {"always",      SHMEM_HUGE_ALWAYS },
3417         {"within_size", SHMEM_HUGE_WITHIN_SIZE },
3418         {"advise",      SHMEM_HUGE_ADVISE },
3419         {}
3420 };
3421
3422 const struct fs_parameter_spec shmem_fs_parameters[] = {
3423         fsparam_u32   ("gid",           Opt_gid),
3424         fsparam_enum  ("huge",          Opt_huge,  shmem_param_enums_huge),
3425         fsparam_u32oct("mode",          Opt_mode),
3426         fsparam_string("mpol",          Opt_mpol),
3427         fsparam_string("nr_blocks",     Opt_nr_blocks),
3428         fsparam_string("nr_inodes",     Opt_nr_inodes),
3429         fsparam_string("size",          Opt_size),
3430         fsparam_u32   ("uid",           Opt_uid),
3431         fsparam_flag  ("inode32",       Opt_inode32),
3432         fsparam_flag  ("inode64",       Opt_inode64),
3433         {}
3434 };
3435
3436 static int shmem_parse_one(struct fs_context *fc, struct fs_parameter *param)
3437 {
3438         struct shmem_options *ctx = fc->fs_private;
3439         struct fs_parse_result result;
3440         unsigned long long size;
3441         char *rest;
3442         int opt;
3443
3444         opt = fs_parse(fc, shmem_fs_parameters, param, &result);
3445         if (opt < 0)
3446                 return opt;
3447
3448         switch (opt) {
3449         case Opt_size:
3450                 size = memparse(param->string, &rest);
3451                 if (*rest == '%') {
3452                         size <<= PAGE_SHIFT;
3453                         size *= totalram_pages();
3454                         do_div(size, 100);
3455                         rest++;
3456                 }
3457                 if (*rest)
3458                         goto bad_value;
3459                 ctx->blocks = DIV_ROUND_UP(size, PAGE_SIZE);
3460                 ctx->seen |= SHMEM_SEEN_BLOCKS;
3461                 break;
3462         case Opt_nr_blocks:
3463                 ctx->blocks = memparse(param->string, &rest);
3464                 if (*rest || ctx->blocks > S64_MAX)
3465                         goto bad_value;
3466                 ctx->seen |= SHMEM_SEEN_BLOCKS;
3467                 break;
3468         case Opt_nr_inodes:
3469                 ctx->inodes = memparse(param->string, &rest);
3470                 if (*rest)
3471                         goto bad_value;
3472                 ctx->seen |= SHMEM_SEEN_INODES;
3473                 break;
3474         case Opt_mode:
3475                 ctx->mode = result.uint_32 & 07777;
3476                 break;
3477         case Opt_uid:
3478                 ctx->uid = make_kuid(current_user_ns(), result.uint_32);
3479                 if (!uid_valid(ctx->uid))
3480                         goto bad_value;
3481                 break;
3482         case Opt_gid:
3483                 ctx->gid = make_kgid(current_user_ns(), result.uint_32);
3484                 if (!gid_valid(ctx->gid))
3485                         goto bad_value;
3486                 break;
3487         case Opt_huge:
3488                 ctx->huge = result.uint_32;
3489                 if (ctx->huge != SHMEM_HUGE_NEVER &&
3490                     !(IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
3491                       has_transparent_hugepage()))
3492                         goto unsupported_parameter;
3493                 ctx->seen |= SHMEM_SEEN_HUGE;
3494                 break;
3495         case Opt_mpol:
3496                 if (IS_ENABLED(CONFIG_NUMA)) {
3497                         mpol_put(ctx->mpol);
3498                         ctx->mpol = NULL;
3499                         if (mpol_parse_str(param->string, &ctx->mpol))
3500                                 goto bad_value;
3501                         break;
3502                 }
3503                 goto unsupported_parameter;
3504         case Opt_inode32:
3505                 ctx->full_inums = false;
3506                 ctx->seen |= SHMEM_SEEN_INUMS;
3507                 break;
3508         case Opt_inode64:
3509                 if (sizeof(ino_t) < 8) {
3510                         return invalfc(fc,
3511                                        "Cannot use inode64 with <64bit inums in kernel\n");
3512                 }
3513                 ctx->full_inums = true;
3514                 ctx->seen |= SHMEM_SEEN_INUMS;
3515                 break;
3516         }
3517         return 0;
3518
3519 unsupported_parameter:
3520         return invalfc(fc, "Unsupported parameter '%s'", param->key);
3521 bad_value:
3522         return invalfc(fc, "Bad value for '%s'", param->key);
3523 }
3524
3525 static int shmem_parse_options(struct fs_context *fc, void *data)
3526 {
3527         char *options = data;
3528
3529         if (options) {
3530                 int err = security_sb_eat_lsm_opts(options, &fc->security);
3531                 if (err)
3532                         return err;
3533         }
3534
3535         while (options != NULL) {
3536                 char *this_char = options;
3537                 for (;;) {
3538                         /*
3539                          * NUL-terminate this option: unfortunately,
3540                          * mount options form a comma-separated list,
3541                          * but mpol's nodelist may also contain commas.
3542                          */
3543                         options = strchr(options, ',');
3544                         if (options == NULL)
3545                                 break;
3546                         options++;
3547                         if (!isdigit(*options)) {
3548                                 options[-1] = '\0';
3549                                 break;
3550                         }
3551                 }
3552                 if (*this_char) {
3553                         char *value = strchr(this_char, '=');
3554                         size_t len = 0;
3555                         int err;
3556
3557                         if (value) {
3558                                 *value++ = '\0';
3559                                 len = strlen(value);
3560                         }
3561                         err = vfs_parse_fs_string(fc, this_char, value, len);
3562                         if (err < 0)
3563                                 return err;
3564                 }
3565         }
3566         return 0;
3567 }
3568
3569 /*
3570  * Reconfigure a shmem filesystem.
3571  *
3572  * Note that we disallow change from limited->unlimited blocks/inodes while any
3573  * are in use; but we must separately disallow unlimited->limited, because in
3574  * that case we have no record of how much is already in use.
3575  */
3576 static int shmem_reconfigure(struct fs_context *fc)
3577 {
3578         struct shmem_options *ctx = fc->fs_private;
3579         struct shmem_sb_info *sbinfo = SHMEM_SB(fc->root->d_sb);
3580         unsigned long inodes;
3581         struct mempolicy *mpol = NULL;
3582         const char *err;
3583
3584         raw_spin_lock(&sbinfo->stat_lock);
3585         inodes = sbinfo->max_inodes - sbinfo->free_inodes;
3586
3587         if ((ctx->seen & SHMEM_SEEN_BLOCKS) && ctx->blocks) {
3588                 if (!sbinfo->max_blocks) {
3589                         err = "Cannot retroactively limit size";
3590                         goto out;
3591                 }
3592                 if (percpu_counter_compare(&sbinfo->used_blocks,
3593                                            ctx->blocks) > 0) {
3594                         err = "Too small a size for current use";
3595                         goto out;
3596                 }
3597         }
3598         if ((ctx->seen & SHMEM_SEEN_INODES) && ctx->inodes) {
3599                 if (!sbinfo->max_inodes) {
3600                         err = "Cannot retroactively limit inodes";
3601                         goto out;
3602                 }
3603                 if (ctx->inodes < inodes) {
3604                         err = "Too few inodes for current use";
3605                         goto out;
3606                 }
3607         }
3608
3609         if ((ctx->seen & SHMEM_SEEN_INUMS) && !ctx->full_inums &&
3610             sbinfo->next_ino > UINT_MAX) {
3611                 err = "Current inum too high to switch to 32-bit inums";
3612                 goto out;
3613         }
3614
3615         if (ctx->seen & SHMEM_SEEN_HUGE)
3616                 sbinfo->huge = ctx->huge;
3617         if (ctx->seen & SHMEM_SEEN_INUMS)
3618                 sbinfo->full_inums = ctx->full_inums;
3619         if (ctx->seen & SHMEM_SEEN_BLOCKS)
3620                 sbinfo->max_blocks  = ctx->blocks;
3621         if (ctx->seen & SHMEM_SEEN_INODES) {
3622                 sbinfo->max_inodes  = ctx->inodes;
3623                 sbinfo->free_inodes = ctx->inodes - inodes;
3624         }
3625
3626         /*
3627          * Preserve previous mempolicy unless mpol remount option was specified.
3628          */
3629         if (ctx->mpol) {
3630                 mpol = sbinfo->mpol;
3631                 sbinfo->mpol = ctx->mpol;       /* transfers initial ref */
3632                 ctx->mpol = NULL;
3633         }
3634         raw_spin_unlock(&sbinfo->stat_lock);
3635         mpol_put(mpol);
3636         return 0;
3637 out:
3638         raw_spin_unlock(&sbinfo->stat_lock);
3639         return invalfc(fc, "%s", err);
3640 }
3641
3642 static int shmem_show_options(struct seq_file *seq, struct dentry *root)
3643 {
3644         struct shmem_sb_info *sbinfo = SHMEM_SB(root->d_sb);
3645
3646         if (sbinfo->max_blocks != shmem_default_max_blocks())
3647                 seq_printf(seq, ",size=%luk",
3648                         sbinfo->max_blocks << (PAGE_SHIFT - 10));
3649         if (sbinfo->max_inodes != shmem_default_max_inodes())
3650                 seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
3651         if (sbinfo->mode != (0777 | S_ISVTX))
3652                 seq_printf(seq, ",mode=%03ho", sbinfo->mode);
3653         if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID))
3654                 seq_printf(seq, ",uid=%u",
3655                                 from_kuid_munged(&init_user_ns, sbinfo->uid));
3656         if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
3657                 seq_printf(seq, ",gid=%u",
3658                                 from_kgid_munged(&init_user_ns, sbinfo->gid));
3659
3660         /*
3661          * Showing inode{64,32} might be useful even if it's the system default,
3662          * since then people don't have to resort to checking both here and
3663          * /proc/config.gz to confirm 64-bit inums were successfully applied
3664          * (which may not even exist if IKCONFIG_PROC isn't enabled).
3665          *
3666          * We hide it when inode64 isn't the default and we are using 32-bit
3667          * inodes, since that probably just means the feature isn't even under
3668          * consideration.
3669          *
3670          * As such:
3671          *
3672          *                     +-----------------+-----------------+
3673          *                     | TMPFS_INODE64=y | TMPFS_INODE64=n |
3674          *  +------------------+-----------------+-----------------+
3675          *  | full_inums=true  | show            | show            |
3676          *  | full_inums=false | show            | hide            |
3677          *  +------------------+-----------------+-----------------+
3678          *
3679          */
3680         if (IS_ENABLED(CONFIG_TMPFS_INODE64) || sbinfo->full_inums)
3681                 seq_printf(seq, ",inode%d", (sbinfo->full_inums ? 64 : 32));
3682 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
3683         /* Rightly or wrongly, show huge mount option unmasked by shmem_huge */
3684         if (sbinfo->huge)
3685                 seq_printf(seq, ",huge=%s", shmem_format_huge(sbinfo->huge));
3686 #endif
3687         shmem_show_mpol(seq, sbinfo->mpol);
3688         return 0;
3689 }
3690
3691 #endif /* CONFIG_TMPFS */
3692
3693 static void shmem_put_super(struct super_block *sb)
3694 {
3695         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
3696
3697         free_percpu(sbinfo->ino_batch);
3698         percpu_counter_destroy(&sbinfo->used_blocks);
3699         mpol_put(sbinfo->mpol);
3700         kfree(sbinfo);
3701         sb->s_fs_info = NULL;
3702 }
3703
3704 static int shmem_fill_super(struct super_block *sb, struct fs_context *fc)
3705 {
3706         struct shmem_options *ctx = fc->fs_private;
3707         struct inode *inode;
3708         struct shmem_sb_info *sbinfo;
3709
3710         /* Round up to L1_CACHE_BYTES to resist false sharing */
3711         sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
3712                                 L1_CACHE_BYTES), GFP_KERNEL);
3713         if (!sbinfo)
3714                 return -ENOMEM;
3715
3716         sb->s_fs_info = sbinfo;
3717
3718 #ifdef CONFIG_TMPFS
3719         /*
3720          * Per default we only allow half of the physical ram per
3721          * tmpfs instance, limiting inodes to one per page of lowmem;
3722          * but the internal instance is left unlimited.
3723          */
3724         if (!(sb->s_flags & SB_KERNMOUNT)) {
3725                 if (!(ctx->seen & SHMEM_SEEN_BLOCKS))
3726                         ctx->blocks = shmem_default_max_blocks();
3727                 if (!(ctx->seen & SHMEM_SEEN_INODES))
3728                         ctx->inodes = shmem_default_max_inodes();
3729                 if (!(ctx->seen & SHMEM_SEEN_INUMS))
3730                         ctx->full_inums = IS_ENABLED(CONFIG_TMPFS_INODE64);
3731         } else {
3732                 sb->s_flags |= SB_NOUSER;
3733         }
3734         sb->s_export_op = &shmem_export_ops;
3735         sb->s_flags |= SB_NOSEC;
3736 #else
3737         sb->s_flags |= SB_NOUSER;
3738 #endif
3739         sbinfo->max_blocks = ctx->blocks;
3740         sbinfo->free_inodes = sbinfo->max_inodes = ctx->inodes;
3741         if (sb->s_flags & SB_KERNMOUNT) {
3742                 sbinfo->ino_batch = alloc_percpu(ino_t);
3743                 if (!sbinfo->ino_batch)
3744                         goto failed;
3745         }
3746         sbinfo->uid = ctx->uid;
3747         sbinfo->gid = ctx->gid;
3748         sbinfo->full_inums = ctx->full_inums;
3749         sbinfo->mode = ctx->mode;
3750         sbinfo->huge = ctx->huge;
3751         sbinfo->mpol = ctx->mpol;
3752         ctx->mpol = NULL;
3753
3754         raw_spin_lock_init(&sbinfo->stat_lock);
3755         if (percpu_counter_init(&sbinfo->used_blocks, 0, GFP_KERNEL))
3756                 goto failed;
3757         spin_lock_init(&sbinfo->shrinklist_lock);
3758         INIT_LIST_HEAD(&sbinfo->shrinklist);
3759
3760         sb->s_maxbytes = MAX_LFS_FILESIZE;
3761         sb->s_blocksize = PAGE_SIZE;
3762         sb->s_blocksize_bits = PAGE_SHIFT;
3763         sb->s_magic = TMPFS_MAGIC;
3764         sb->s_op = &shmem_ops;
3765         sb->s_time_gran = 1;
3766 #ifdef CONFIG_TMPFS_XATTR
3767         sb->s_xattr = shmem_xattr_handlers;
3768 #endif
3769 #ifdef CONFIG_TMPFS_POSIX_ACL
3770         sb->s_flags |= SB_POSIXACL;
3771 #endif
3772         uuid_gen(&sb->s_uuid);
3773
3774         inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
3775         if (!inode)
3776                 goto failed;
3777         inode->i_uid = sbinfo->uid;
3778         inode->i_gid = sbinfo->gid;
3779         sb->s_root = d_make_root(inode);
3780         if (!sb->s_root)
3781                 goto failed;
3782         return 0;
3783
3784 failed:
3785         shmem_put_super(sb);
3786         return -ENOMEM;
3787 }
3788
3789 static int shmem_get_tree(struct fs_context *fc)
3790 {
3791         return get_tree_nodev(fc, shmem_fill_super);
3792 }
3793
3794 static void shmem_free_fc(struct fs_context *fc)
3795 {
3796         struct shmem_options *ctx = fc->fs_private;
3797
3798         if (ctx) {
3799                 mpol_put(ctx->mpol);
3800                 kfree(ctx);
3801         }
3802 }
3803
3804 static const struct fs_context_operations shmem_fs_context_ops = {
3805         .free                   = shmem_free_fc,
3806         .get_tree               = shmem_get_tree,
3807 #ifdef CONFIG_TMPFS
3808         .parse_monolithic       = shmem_parse_options,
3809         .parse_param            = shmem_parse_one,
3810         .reconfigure            = shmem_reconfigure,
3811 #endif
3812 };
3813
3814 static struct kmem_cache *shmem_inode_cachep;
3815
3816 static struct inode *shmem_alloc_inode(struct super_block *sb)
3817 {
3818         struct shmem_inode_info *info;
3819         info = alloc_inode_sb(sb, shmem_inode_cachep, GFP_KERNEL);
3820         if (!info)
3821                 return NULL;
3822         return &info->vfs_inode;
3823 }
3824
3825 static void shmem_free_in_core_inode(struct inode *inode)
3826 {
3827         if (S_ISLNK(inode->i_mode))
3828                 kfree(inode->i_link);
3829         kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
3830 }
3831
3832 static void shmem_destroy_inode(struct inode *inode)
3833 {
3834         if (S_ISREG(inode->i_mode))
3835                 mpol_free_shared_policy(&SHMEM_I(inode)->policy);
3836 }
3837
3838 static void shmem_init_inode(void *foo)
3839 {
3840         struct shmem_inode_info *info = foo;
3841         inode_init_once(&info->vfs_inode);
3842 }
3843
3844 static void shmem_init_inodecache(void)
3845 {
3846         shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
3847                                 sizeof(struct shmem_inode_info),
3848                                 0, SLAB_PANIC|SLAB_ACCOUNT, shmem_init_inode);
3849 }
3850
3851 static void shmem_destroy_inodecache(void)
3852 {
3853         kmem_cache_destroy(shmem_inode_cachep);
3854 }
3855
3856 /* Keep the page in page cache instead of truncating it */
3857 static int shmem_error_remove_page(struct address_space *mapping,
3858                                    struct page *page)
3859 {
3860         return 0;
3861 }
3862
3863 const struct address_space_operations shmem_aops = {
3864         .writepage      = shmem_writepage,
3865         .dirty_folio    = noop_dirty_folio,
3866 #ifdef CONFIG_TMPFS
3867         .write_begin    = shmem_write_begin,
3868         .write_end      = shmem_write_end,
3869 #endif
3870 #ifdef CONFIG_MIGRATION
3871         .migrate_folio  = migrate_folio,
3872 #endif
3873         .error_remove_page = shmem_error_remove_page,
3874 };
3875 EXPORT_SYMBOL(shmem_aops);
3876
3877 static const struct file_operations shmem_file_operations = {
3878         .mmap           = shmem_mmap,
3879         .get_unmapped_area = shmem_get_unmapped_area,
3880 #ifdef CONFIG_TMPFS
3881         .llseek         = shmem_file_llseek,
3882         .read_iter      = shmem_file_read_iter,
3883         .write_iter     = generic_file_write_iter,
3884         .fsync          = noop_fsync,
3885         .splice_read    = generic_file_splice_read,
3886         .splice_write   = iter_file_splice_write,
3887         .fallocate      = shmem_fallocate,
3888 #endif
3889 };
3890
3891 static const struct inode_operations shmem_inode_operations = {
3892         .getattr        = shmem_getattr,
3893         .setattr        = shmem_setattr,
3894 #ifdef CONFIG_TMPFS_XATTR
3895         .listxattr      = shmem_listxattr,
3896         .set_acl        = simple_set_acl,
3897         .fileattr_get   = shmem_fileattr_get,
3898         .fileattr_set   = shmem_fileattr_set,
3899 #endif
3900 };
3901
3902 static const struct inode_operations shmem_dir_inode_operations = {
3903 #ifdef CONFIG_TMPFS
3904         .getattr        = shmem_getattr,
3905         .create         = shmem_create,
3906         .lookup         = simple_lookup,
3907         .link           = shmem_link,
3908         .unlink         = shmem_unlink,
3909         .symlink        = shmem_symlink,
3910         .mkdir          = shmem_mkdir,
3911         .rmdir          = shmem_rmdir,
3912         .mknod          = shmem_mknod,
3913         .rename         = shmem_rename2,
3914         .tmpfile        = shmem_tmpfile,
3915 #endif
3916 #ifdef CONFIG_TMPFS_XATTR
3917         .listxattr      = shmem_listxattr,
3918         .fileattr_get   = shmem_fileattr_get,
3919         .fileattr_set   = shmem_fileattr_set,
3920 #endif
3921 #ifdef CONFIG_TMPFS_POSIX_ACL
3922         .setattr        = shmem_setattr,
3923         .set_acl        = simple_set_acl,
3924 #endif
3925 };
3926
3927 static const struct inode_operations shmem_special_inode_operations = {
3928         .getattr        = shmem_getattr,
3929 #ifdef CONFIG_TMPFS_XATTR
3930         .listxattr      = shmem_listxattr,
3931 #endif
3932 #ifdef CONFIG_TMPFS_POSIX_ACL
3933         .setattr        = shmem_setattr,
3934         .set_acl        = simple_set_acl,
3935 #endif
3936 };
3937
3938 static const struct super_operations shmem_ops = {
3939         .alloc_inode    = shmem_alloc_inode,
3940         .free_inode     = shmem_free_in_core_inode,
3941         .destroy_inode  = shmem_destroy_inode,
3942 #ifdef CONFIG_TMPFS
3943         .statfs         = shmem_statfs,
3944         .show_options   = shmem_show_options,
3945 #endif
3946         .evict_inode    = shmem_evict_inode,
3947         .drop_inode     = generic_delete_inode,
3948         .put_super      = shmem_put_super,
3949 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
3950         .nr_cached_objects      = shmem_unused_huge_count,
3951         .free_cached_objects    = shmem_unused_huge_scan,
3952 #endif
3953 };
3954
3955 static const struct vm_operations_struct shmem_vm_ops = {
3956         .fault          = shmem_fault,
3957         .map_pages      = filemap_map_pages,
3958 #ifdef CONFIG_NUMA
3959         .set_policy     = shmem_set_policy,
3960         .get_policy     = shmem_get_policy,
3961 #endif
3962 };
3963
3964 int shmem_init_fs_context(struct fs_context *fc)
3965 {
3966         struct shmem_options *ctx;
3967
3968         ctx = kzalloc(sizeof(struct shmem_options), GFP_KERNEL);
3969         if (!ctx)
3970                 return -ENOMEM;
3971
3972         ctx->mode = 0777 | S_ISVTX;
3973         ctx->uid = current_fsuid();
3974         ctx->gid = current_fsgid();
3975
3976         fc->fs_private = ctx;
3977         fc->ops = &shmem_fs_context_ops;
3978         return 0;
3979 }
3980
3981 static struct file_system_type shmem_fs_type = {
3982         .owner          = THIS_MODULE,
3983         .name           = "tmpfs",
3984         .init_fs_context = shmem_init_fs_context,
3985 #ifdef CONFIG_TMPFS
3986         .parameters     = shmem_fs_parameters,
3987 #endif
3988         .kill_sb        = kill_litter_super,
3989         .fs_flags       = FS_USERNS_MOUNT,
3990 };
3991
3992 void __init shmem_init(void)
3993 {
3994         int error;
3995
3996         shmem_init_inodecache();
3997
3998         error = register_filesystem(&shmem_fs_type);
3999         if (error) {
4000                 pr_err("Could not register tmpfs\n");
4001                 goto out2;
4002         }
4003
4004         shm_mnt = kern_mount(&shmem_fs_type);
4005         if (IS_ERR(shm_mnt)) {
4006                 error = PTR_ERR(shm_mnt);
4007                 pr_err("Could not kern_mount tmpfs\n");
4008                 goto out1;
4009         }
4010
4011 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
4012         if (has_transparent_hugepage() && shmem_huge > SHMEM_HUGE_DENY)
4013                 SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
4014         else
4015                 shmem_huge = SHMEM_HUGE_NEVER; /* just in case it was patched */
4016 #endif
4017         return;
4018
4019 out1:
4020         unregister_filesystem(&shmem_fs_type);
4021 out2:
4022         shmem_destroy_inodecache();
4023         shm_mnt = ERR_PTR(error);
4024 }
4025
4026 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && defined(CONFIG_SYSFS)
4027 static ssize_t shmem_enabled_show(struct kobject *kobj,
4028                                   struct kobj_attribute *attr, char *buf)
4029 {
4030         static const int values[] = {
4031                 SHMEM_HUGE_ALWAYS,
4032                 SHMEM_HUGE_WITHIN_SIZE,
4033                 SHMEM_HUGE_ADVISE,
4034                 SHMEM_HUGE_NEVER,
4035                 SHMEM_HUGE_DENY,
4036                 SHMEM_HUGE_FORCE,
4037         };
4038         int len = 0;
4039         int i;
4040
4041         for (i = 0; i < ARRAY_SIZE(values); i++) {
4042                 len += sysfs_emit_at(buf, len,
4043                                      shmem_huge == values[i] ? "%s[%s]" : "%s%s",
4044                                      i ? " " : "",
4045                                      shmem_format_huge(values[i]));
4046         }
4047
4048         len += sysfs_emit_at(buf, len, "\n");
4049
4050         return len;
4051 }
4052
4053 static ssize_t shmem_enabled_store(struct kobject *kobj,
4054                 struct kobj_attribute *attr, const char *buf, size_t count)
4055 {
4056         char tmp[16];
4057         int huge;
4058
4059         if (count + 1 > sizeof(tmp))
4060                 return -EINVAL;
4061         memcpy(tmp, buf, count);
4062         tmp[count] = '\0';
4063         if (count && tmp[count - 1] == '\n')
4064                 tmp[count - 1] = '\0';
4065
4066         huge = shmem_parse_huge(tmp);
4067         if (huge == -EINVAL)
4068                 return -EINVAL;
4069         if (!has_transparent_hugepage() &&
4070                         huge != SHMEM_HUGE_NEVER && huge != SHMEM_HUGE_DENY)
4071                 return -EINVAL;
4072
4073         shmem_huge = huge;
4074         if (shmem_huge > SHMEM_HUGE_DENY)
4075                 SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
4076         return count;
4077 }
4078
4079 struct kobj_attribute shmem_enabled_attr = __ATTR_RW(shmem_enabled);
4080 #endif /* CONFIG_TRANSPARENT_HUGEPAGE && CONFIG_SYSFS */
4081
4082 #else /* !CONFIG_SHMEM */
4083
4084 /*
4085  * tiny-shmem: simple shmemfs and tmpfs using ramfs code
4086  *
4087  * This is intended for small system where the benefits of the full
4088  * shmem code (swap-backed and resource-limited) are outweighed by
4089  * their complexity. On systems without swap this code should be
4090  * effectively equivalent, but much lighter weight.
4091  */
4092
4093 static struct file_system_type shmem_fs_type = {
4094         .name           = "tmpfs",
4095         .init_fs_context = ramfs_init_fs_context,
4096         .parameters     = ramfs_fs_parameters,
4097         .kill_sb        = kill_litter_super,
4098         .fs_flags       = FS_USERNS_MOUNT,
4099 };
4100
4101 void __init shmem_init(void)
4102 {
4103         BUG_ON(register_filesystem(&shmem_fs_type) != 0);
4104
4105         shm_mnt = kern_mount(&shmem_fs_type);
4106         BUG_ON(IS_ERR(shm_mnt));
4107 }
4108
4109 int shmem_unuse(unsigned int type)
4110 {
4111         return 0;
4112 }
4113
4114 int shmem_lock(struct file *file, int lock, struct ucounts *ucounts)
4115 {
4116         return 0;
4117 }
4118
4119 void shmem_unlock_mapping(struct address_space *mapping)
4120 {
4121 }
4122
4123 #ifdef CONFIG_MMU
4124 unsigned long shmem_get_unmapped_area(struct file *file,
4125                                       unsigned long addr, unsigned long len,
4126                                       unsigned long pgoff, unsigned long flags)
4127 {
4128         return current->mm->get_unmapped_area(file, addr, len, pgoff, flags);
4129 }
4130 #endif
4131
4132 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
4133 {
4134         truncate_inode_pages_range(inode->i_mapping, lstart, lend);
4135 }
4136 EXPORT_SYMBOL_GPL(shmem_truncate_range);
4137
4138 #define shmem_vm_ops                            generic_file_vm_ops
4139 #define shmem_file_operations                   ramfs_file_operations
4140 #define shmem_get_inode(sb, dir, mode, dev, flags)      ramfs_get_inode(sb, dir, mode, dev)
4141 #define shmem_acct_size(flags, size)            0
4142 #define shmem_unacct_size(flags, size)          do {} while (0)
4143
4144 #endif /* CONFIG_SHMEM */
4145
4146 /* common code */
4147
4148 static struct file *__shmem_file_setup(struct vfsmount *mnt, const char *name, loff_t size,
4149                                        unsigned long flags, unsigned int i_flags)
4150 {
4151         struct inode *inode;
4152         struct file *res;
4153
4154         if (IS_ERR(mnt))
4155                 return ERR_CAST(mnt);
4156
4157         if (size < 0 || size > MAX_LFS_FILESIZE)
4158                 return ERR_PTR(-EINVAL);
4159
4160         if (shmem_acct_size(flags, size))
4161                 return ERR_PTR(-ENOMEM);
4162
4163         inode = shmem_get_inode(mnt->mnt_sb, NULL, S_IFREG | S_IRWXUGO, 0,
4164                                 flags);
4165         if (unlikely(!inode)) {
4166                 shmem_unacct_size(flags, size);
4167                 return ERR_PTR(-ENOSPC);
4168         }
4169         inode->i_flags |= i_flags;
4170         inode->i_size = size;
4171         clear_nlink(inode);     /* It is unlinked */
4172         res = ERR_PTR(ramfs_nommu_expand_for_mapping(inode, size));
4173         if (!IS_ERR(res))
4174                 res = alloc_file_pseudo(inode, mnt, name, O_RDWR,
4175                                 &shmem_file_operations);
4176         if (IS_ERR(res))
4177                 iput(inode);
4178         return res;
4179 }
4180
4181 /**
4182  * shmem_kernel_file_setup - get an unlinked file living in tmpfs which must be
4183  *      kernel internal.  There will be NO LSM permission checks against the
4184  *      underlying inode.  So users of this interface must do LSM checks at a
4185  *      higher layer.  The users are the big_key and shm implementations.  LSM
4186  *      checks are provided at the key or shm level rather than the inode.
4187  * @name: name for dentry (to be seen in /proc/<pid>/maps
4188  * @size: size to be set for the file
4189  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
4190  */
4191 struct file *shmem_kernel_file_setup(const char *name, loff_t size, unsigned long flags)
4192 {
4193         return __shmem_file_setup(shm_mnt, name, size, flags, S_PRIVATE);
4194 }
4195
4196 /**
4197  * shmem_file_setup - get an unlinked file living in tmpfs
4198  * @name: name for dentry (to be seen in /proc/<pid>/maps
4199  * @size: size to be set for the file
4200  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
4201  */
4202 struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
4203 {
4204         return __shmem_file_setup(shm_mnt, name, size, flags, 0);
4205 }
4206 EXPORT_SYMBOL_GPL(shmem_file_setup);
4207
4208 /**
4209  * shmem_file_setup_with_mnt - get an unlinked file living in tmpfs
4210  * @mnt: the tmpfs mount where the file will be created
4211  * @name: name for dentry (to be seen in /proc/<pid>/maps
4212  * @size: size to be set for the file
4213  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
4214  */
4215 struct file *shmem_file_setup_with_mnt(struct vfsmount *mnt, const char *name,
4216                                        loff_t size, unsigned long flags)
4217 {
4218         return __shmem_file_setup(mnt, name, size, flags, 0);
4219 }
4220 EXPORT_SYMBOL_GPL(shmem_file_setup_with_mnt);
4221
4222 /**
4223  * shmem_zero_setup - setup a shared anonymous mapping
4224  * @vma: the vma to be mmapped is prepared by do_mmap
4225  */
4226 int shmem_zero_setup(struct vm_area_struct *vma)
4227 {
4228         struct file *file;
4229         loff_t size = vma->vm_end - vma->vm_start;
4230
4231         /*
4232          * Cloning a new file under mmap_lock leads to a lock ordering conflict
4233          * between XFS directory reading and selinux: since this file is only
4234          * accessible to the user through its mapping, use S_PRIVATE flag to
4235          * bypass file security, in the same way as shmem_kernel_file_setup().
4236          */
4237         file = shmem_kernel_file_setup("dev/zero", size, vma->vm_flags);
4238         if (IS_ERR(file))
4239                 return PTR_ERR(file);
4240
4241         if (vma->vm_file)
4242                 fput(vma->vm_file);
4243         vma->vm_file = file;
4244         vma->vm_ops = &shmem_vm_ops;
4245
4246         return 0;
4247 }
4248
4249 /**
4250  * shmem_read_mapping_page_gfp - read into page cache, using specified page allocation flags.
4251  * @mapping:    the page's address_space
4252  * @index:      the page index
4253  * @gfp:        the page allocator flags to use if allocating
4254  *
4255  * This behaves as a tmpfs "read_cache_page_gfp(mapping, index, gfp)",
4256  * with any new page allocations done using the specified allocation flags.
4257  * But read_cache_page_gfp() uses the ->read_folio() method: which does not
4258  * suit tmpfs, since it may have pages in swapcache, and needs to find those
4259  * for itself; although drivers/gpu/drm i915 and ttm rely upon this support.
4260  *
4261  * i915_gem_object_get_pages_gtt() mixes __GFP_NORETRY | __GFP_NOWARN in
4262  * with the mapping_gfp_mask(), to avoid OOMing the machine unnecessarily.
4263  */
4264 struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
4265                                          pgoff_t index, gfp_t gfp)
4266 {
4267 #ifdef CONFIG_SHMEM
4268         struct inode *inode = mapping->host;
4269         struct page *page;
4270         int error;
4271
4272         BUG_ON(!shmem_mapping(mapping));
4273         error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE,
4274                                   gfp, NULL, NULL, NULL);
4275         if (error)
4276                 return ERR_PTR(error);
4277
4278         unlock_page(page);
4279         if (PageHWPoison(page)) {
4280                 put_page(page);
4281                 return ERR_PTR(-EIO);
4282         }
4283
4284         return page;
4285 #else
4286         /*
4287          * The tiny !SHMEM case uses ramfs without swap
4288          */
4289         return read_cache_page_gfp(mapping, index, gfp);
4290 #endif
4291 }
4292 EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);