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/mm.h>
  32 #include <linux/export.h>
  33 #include <linux/swap.h>
  34 #include <linux/aio.h>
  35
  36 static struct vfsmount *shm_mnt;
  37
  38 #ifdef CONFIG_SHMEM
  39 /*
  40  * This virtual memory filesystem is heavily based on the ramfs. It
  41  * extends ramfs by the ability to use swap and honor resource limits
  42  * which makes it a completely usable filesystem.
  43  */
  44
  45 #include <linux/xattr.h>
  46 #include <linux/exportfs.h>
  47 #include <linux/posix_acl.h>
  48 #include <linux/generic_acl.h>
  49 #include <linux/mman.h>
  50 #include <linux/string.h>
  51 #include <linux/slab.h>
  52 #include <linux/backing-dev.h>
  53 #include <linux/shmem_fs.h>
  54 #include <linux/writeback.h>
  55 #include <linux/blkdev.h>
  56 #include <linux/pagevec.h>
  57 #include <linux/percpu_counter.h>
  58 #include <linux/falloc.h>
  59 #include <linux/splice.h>
  60 #include <linux/security.h>
  61 #include <linux/swapops.h>
  62 #include <linux/mempolicy.h>
  63 #include <linux/namei.h>
  64 #include <linux/ctype.h>
  65 #include <linux/migrate.h>
  66 #include <linux/highmem.h>
  67 #include <linux/seq_file.h>
  68 #include <linux/magic.h>
  69
  70 #include <asm/uaccess.h>
  71 #include <asm/pgtable.h>
  72
  73 #define BLOCKS_PER_PAGE  (PAGE_CACHE_SIZE/512)
  74 #define VM_ACCT(size)    (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
  75
  76 /* Pretend that each entry is of this size in directory's i_size */
  77 #define BOGO_DIRENT_SIZE 20
  78
  79 /* Symlink up to this size is kmalloc'ed instead of using a swappable page */
  80 #define SHORT_SYMLINK_LEN 128
  81
  82 /*
  83  * shmem_fallocate and shmem_writepage communicate via inode->i_private
  84  * (with i_mutex making sure that it has only one user at a time):
  85  * we would prefer not to enlarge the shmem inode just for that.
  86  */
  87 struct shmem_falloc {
  88         pgoff_t start;          /* start of range currently being fallocated */
  89         pgoff_t next;           /* the next page offset to be fallocated */
  90         pgoff_t nr_falloced;    /* how many new pages have been fallocated */
  91         pgoff_t nr_unswapped;   /* how often writepage refused to swap out */
  92 };
  93
  94 /* Flag allocation requirements to shmem_getpage */
  95 enum sgp_type {
  96         SGP_READ,       /* don't exceed i_size, don't allocate page */
  97         SGP_CACHE,      /* don't exceed i_size, may allocate page */
  98         SGP_DIRTY,      /* like SGP_CACHE, but set new page dirty */
  99         SGP_WRITE,      /* may exceed i_size, may allocate !Uptodate page */
 100         SGP_FALLOC,     /* like SGP_WRITE, but make existing page Uptodate */
 101 };
 102
 103 #ifdef CONFIG_TMPFS
 104 static unsigned long shmem_default_max_blocks(void)
 105 {
 106         return totalram_pages / 2;
 107 }
 108
 109 static unsigned long shmem_default_max_inodes(void)
 110 {
 111         return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
 112 }
 113 #endif
 114
 115 static bool shmem_should_replace_page(struct page *page, gfp_t gfp);
 116 static int shmem_replace_page(struct page **pagep, gfp_t gfp,
 117                                 struct shmem_inode_info *info, pgoff_t index);
 118 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
 119         struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type);
 120
 121 static inline int shmem_getpage(struct inode *inode, pgoff_t index,
 122         struct page **pagep, enum sgp_type sgp, int *fault_type)
 123 {
 124         return shmem_getpage_gfp(inode, index, pagep, sgp,
 125                         mapping_gfp_mask(inode->i_mapping), fault_type);
 126 }
 127
 128 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
 129 {
 130         return sb->s_fs_info;
 131 }
 132
 133 /*
 134  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
 135  * for shared memory and for shared anonymous (/dev/zero) mappings
 136  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
 137  * consistent with the pre-accounting of private mappings ...
 138  */
 139 static inline int shmem_acct_size(unsigned long flags, loff_t size)
 140 {
 141         return (flags & VM_NORESERVE) ?
 142                 0 : security_vm_enough_memory_mm(current->mm, VM_ACCT(size));
 143 }
 144
 145 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
 146 {
 147         if (!(flags & VM_NORESERVE))
 148                 vm_unacct_memory(VM_ACCT(size));
 149 }
 150
 151 /*
 152  * ... whereas tmpfs objects are accounted incrementally as
 153  * pages are allocated, in order to allow huge sparse files.
 154  * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
 155  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
 156  */
 157 static inline int shmem_acct_block(unsigned long flags)
 158 {
 159         return (flags & VM_NORESERVE) ?
 160                 security_vm_enough_memory_mm(current->mm, VM_ACCT(PAGE_CACHE_SIZE)) : 0;
 161 }
 162
 163 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
 164 {
 165         if (flags & VM_NORESERVE)
 166                 vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
 167 }
 168
 169 static const struct super_operations shmem_ops;
 170 static const struct address_space_operations shmem_aops;
 171 static const struct file_operations shmem_file_operations;
 172 static const struct inode_operations shmem_inode_operations;
 173 static const struct inode_operations shmem_dir_inode_operations;
 174 static const struct inode_operations shmem_special_inode_operations;
 175 static const struct vm_operations_struct shmem_vm_ops;
 176
 177 static struct backing_dev_info shmem_backing_dev_info  __read_mostly = {
 178         .ra_pages       = 0,    /* No readahead */
 179         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
 180 };
 181
 182 static LIST_HEAD(shmem_swaplist);
 183 static DEFINE_MUTEX(shmem_swaplist_mutex);
 184
 185 static int shmem_reserve_inode(struct super_block *sb)
 186 {
 187         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
 188         if (sbinfo->max_inodes) {
 189                 spin_lock(&sbinfo->stat_lock);
 190                 if (!sbinfo->free_inodes) {
 191                         spin_unlock(&sbinfo->stat_lock);
 192                         return -ENOSPC;
 193                 }
 194                 sbinfo->free_inodes--;
 195                 spin_unlock(&sbinfo->stat_lock);
 196         }
 197         return 0;
 198 }
 199
 200 static void shmem_free_inode(struct super_block *sb)
 201 {
 202         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
 203         if (sbinfo->max_inodes) {
 204                 spin_lock(&sbinfo->stat_lock);
 205                 sbinfo->free_inodes++;
 206                 spin_unlock(&sbinfo->stat_lock);
 207         }
 208 }
 209
 210 /**
 211  * shmem_recalc_inode - recalculate the block usage of an inode
 212  * @inode: inode to recalc
 213  *
 214  * We have to calculate the free blocks since the mm can drop
 215  * undirtied hole pages behind our back.
 216  *
 217  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
 218  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
 219  *
 220  * It has to be called with the spinlock held.
 221  */
 222 static void shmem_recalc_inode(struct inode *inode)
 223 {
 224         struct shmem_inode_info *info = SHMEM_I(inode);
 225         long freed;
 226
 227         freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
 228         if (freed > 0) {
 229                 struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 230                 if (sbinfo->max_blocks)
 231                         percpu_counter_add(&sbinfo->used_blocks, -freed);
 232                 info->alloced -= freed;
 233                 inode->i_blocks -= freed * BLOCKS_PER_PAGE;
 234                 shmem_unacct_blocks(info->flags, freed);
 235         }
 236 }
 237
 238 /*
 239  * Replace item expected in radix tree by a new item, while holding tree lock.
 240  */
 241 static int shmem_radix_tree_replace(struct address_space *mapping,
 242                         pgoff_t index, void *expected, void *replacement)
 243 {
 244         void **pslot;
 245         void *item = NULL;
 246
 247         VM_BUG_ON(!expected);
 248         pslot = radix_tree_lookup_slot(&mapping->page_tree, index);
 249         if (pslot)
 250                 item = radix_tree_deref_slot_protected(pslot,
 251                                                         &mapping->tree_lock);
 252         if (item != expected)
 253                 return -ENOENT;
 254         if (replacement)
 255                 radix_tree_replace_slot(pslot, replacement);
 256         else
 257                 radix_tree_delete(&mapping->page_tree, index);
 258         return 0;
 259 }
 260
 261 /*
 262  * Sometimes, before we decide whether to proceed or to fail, we must check
 263  * that an entry was not already brought back from swap by a racing thread.
 264  *
 265  * Checking page is not enough: by the time a SwapCache page is locked, it
 266  * might be reused, and again be SwapCache, using the same swap as before.
 267  */
 268 static bool shmem_confirm_swap(struct address_space *mapping,
 269                                pgoff_t index, swp_entry_t swap)
 270 {
 271         void *item;
 272
 273         rcu_read_lock();
 274         item = radix_tree_lookup(&mapping->page_tree, index);
 275         rcu_read_unlock();
 276         return item == swp_to_radix_entry(swap);
 277 }
 278
 279 /*
 280  * Like add_to_page_cache_locked, but error if expected item has gone.
 281  */
 282 static int shmem_add_to_page_cache(struct page *page,
 283                                    struct address_space *mapping,
 284                                    pgoff_t index, gfp_t gfp, void *expected)
 285 {
 286         int error;
 287
 288         VM_BUG_ON(!PageLocked(page));
 289         VM_BUG_ON(!PageSwapBacked(page));
 290
 291         page_cache_get(page);
 292         page->mapping = mapping;
 293         page->index = index;
 294
 295         spin_lock_irq(&mapping->tree_lock);
 296         if (!expected)
 297                 error = radix_tree_insert(&mapping->page_tree, index, page);
 298         else
 299                 error = shmem_radix_tree_replace(mapping, index, expected,
 300                                                                  page);
 301         if (!error) {
 302                 mapping->nrpages++;
 303                 __inc_zone_page_state(page, NR_FILE_PAGES);
 304                 __inc_zone_page_state(page, NR_SHMEM);
 305                 spin_unlock_irq(&mapping->tree_lock);
 306         } else {
 307                 page->mapping = NULL;
 308                 spin_unlock_irq(&mapping->tree_lock);
 309                 page_cache_release(page);
 310         }
 311         return error;
 312 }
 313
 314 /*
 315  * Like delete_from_page_cache, but substitutes swap for page.
 316  */
 317 static void shmem_delete_from_page_cache(struct page *page, void *radswap)
 318 {
 319         struct address_space *mapping = page->mapping;
 320         int error;
 321
 322         spin_lock_irq(&mapping->tree_lock);
 323         error = shmem_radix_tree_replace(mapping, page->index, page, radswap);
 324         page->mapping = NULL;
 325         mapping->nrpages--;
 326         __dec_zone_page_state(page, NR_FILE_PAGES);
 327         __dec_zone_page_state(page, NR_SHMEM);
 328         spin_unlock_irq(&mapping->tree_lock);
 329         page_cache_release(page);
 330         BUG_ON(error);
 331 }
 332
 333 /*
 334  * Like find_get_pages, but collecting swap entries as well as pages.
 335  */
 336 static unsigned shmem_find_get_pages_and_swap(struct address_space *mapping,
 337                                         pgoff_t start, unsigned int nr_pages,
 338                                         struct page **pages, pgoff_t *indices)
 339 {
 340         void **slot;
 341         unsigned int ret = 0;
 342         struct radix_tree_iter iter;
 343
 344         if (!nr_pages)
 345                 return 0;
 346
 347         rcu_read_lock();
 348 restart:
 349         radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
 350                 struct page *page;
 351 repeat:
 352                 page = radix_tree_deref_slot(slot);
 353                 if (unlikely(!page))
 354                         continue;
 355                 if (radix_tree_exception(page)) {
 356                         if (radix_tree_deref_retry(page))
 357                                 goto restart;
 358                         /*
 359                          * Otherwise, we must be storing a swap entry
 360                          * here as an exceptional entry: so return it
 361                          * without attempting to raise page count.
 362                          */
 363                         goto export;
 364                 }
 365                 if (!page_cache_get_speculative(page))
 366                         goto repeat;
 367
 368                 /* Has the page moved? */
 369                 if (unlikely(page != *slot)) {
 370                         page_cache_release(page);
 371                         goto repeat;
 372                 }
 373 export:
 374                 indices[ret] = iter.index;
 375                 pages[ret] = page;
 376                 if (++ret == nr_pages)
 377                         break;
 378         }
 379         rcu_read_unlock();
 380         return ret;
 381 }
 382
 383 /*
 384  * Remove swap entry from radix tree, free the swap and its page cache.
 385  */
 386 static int shmem_free_swap(struct address_space *mapping,
 387                            pgoff_t index, void *radswap)
 388 {
 389         int error;
 390
 391         spin_lock_irq(&mapping->tree_lock);
 392         error = shmem_radix_tree_replace(mapping, index, radswap, NULL);
 393         spin_unlock_irq(&mapping->tree_lock);
 394         if (!error)
 395                 free_swap_and_cache(radix_to_swp_entry(radswap));
 396         return error;
 397 }
 398
 399 /*
 400  * Pagevec may contain swap entries, so shuffle up pages before releasing.
 401  */
 402 static void shmem_deswap_pagevec(struct pagevec *pvec)
 403 {
 404         int i, j;
 405
 406         for (i = 0, j = 0; i < pagevec_count(pvec); i++) {
 407                 struct page *page = pvec->pages[i];
 408                 if (!radix_tree_exceptional_entry(page))
 409                         pvec->pages[j++] = page;
 410         }
 411         pvec->nr = j;
 412 }
 413
 414 /*
 415  * SysV IPC SHM_UNLOCK restore Unevictable pages to their evictable lists.
 416  */
 417 void shmem_unlock_mapping(struct address_space *mapping)
 418 {
 419         struct pagevec pvec;
 420         pgoff_t indices[PAGEVEC_SIZE];
 421         pgoff_t index = 0;
 422
 423         pagevec_init(&pvec, 0);
 424         /*
 425          * Minor point, but we might as well stop if someone else SHM_LOCKs it.
 426          */
 427         while (!mapping_unevictable(mapping)) {
 428                 /*
 429                  * Avoid pagevec_lookup(): find_get_pages() returns 0 as if it
 430                  * has finished, if it hits a row of PAGEVEC_SIZE swap entries.
 431                  */
 432                 pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
 433                                         PAGEVEC_SIZE, pvec.pages, indices);
 434                 if (!pvec.nr)
 435                         break;
 436                 index = indices[pvec.nr - 1] + 1;
 437                 shmem_deswap_pagevec(&pvec);
 438                 check_move_unevictable_pages(pvec.pages, pvec.nr);
 439                 pagevec_release(&pvec);
 440                 cond_resched();
 441         }
 442 }
 443
 444 /*
 445  * Remove range of pages and swap entries from radix tree, and free them.
 446  * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate.
 447  */
 448 static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
 449                                                                  bool unfalloc)
 450 {
 451         struct address_space *mapping = inode->i_mapping;
 452         struct shmem_inode_info *info = SHMEM_I(inode);
 453         pgoff_t start = (lstart + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 454         pgoff_t end = (lend + 1) >> PAGE_CACHE_SHIFT;
 455         unsigned int partial_start = lstart & (PAGE_CACHE_SIZE - 1);
 456         unsigned int partial_end = (lend + 1) & (PAGE_CACHE_SIZE - 1);
 457         struct pagevec pvec;
 458         pgoff_t indices[PAGEVEC_SIZE];
 459         long nr_swaps_freed = 0;
 460         pgoff_t index;
 461         int i;
 462
 463         if (lend == -1)
 464                 end = -1;       /* unsigned, so actually very big */
 465
 466         pagevec_init(&pvec, 0);
 467         index = start;
 468         while (index < end) {
 469                 pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
 470                                 min(end - index, (pgoff_t)PAGEVEC_SIZE),
 471                                                         pvec.pages, indices);
 472                 if (!pvec.nr)
 473                         break;
 474                 mem_cgroup_uncharge_start();
 475                 for (i = 0; i < pagevec_count(&pvec); i++) {
 476                         struct page *page = pvec.pages[i];
 477
 478                         index = indices[i];
 479                         if (index >= end)
 480                                 break;
 481
 482                         if (radix_tree_exceptional_entry(page)) {
 483                                 if (unfalloc)
 484                                         continue;
 485                                 nr_swaps_freed += !shmem_free_swap(mapping,
 486                                                                 index, page);
 487                                 continue;
 488                         }
 489
 490                         if (!trylock_page(page))
 491                                 continue;
 492                         if (!unfalloc || !PageUptodate(page)) {
 493                                 if (page->mapping == mapping) {
 494                                         VM_BUG_ON(PageWriteback(page));
 495                                         truncate_inode_page(mapping, page);
 496                                 }
 497                         }
 498                         unlock_page(page);
 499                 }
 500                 shmem_deswap_pagevec(&pvec);
 501                 pagevec_release(&pvec);
 502                 mem_cgroup_uncharge_end();
 503                 cond_resched();
 504                 index++;
 505         }
 506
 507         if (partial_start) {
 508                 struct page *page = NULL;
 509                 shmem_getpage(inode, start - 1, &page, SGP_READ, NULL);
 510                 if (page) {
 511                         unsigned int top = PAGE_CACHE_SIZE;
 512                         if (start > end) {
 513                                 top = partial_end;
 514                                 partial_end = 0;
 515                         }
 516                         zero_user_segment(page, partial_start, top);
 517                         set_page_dirty(page);
 518                         unlock_page(page);
 519                         page_cache_release(page);
 520                 }
 521         }
 522         if (partial_end) {
 523                 struct page *page = NULL;
 524                 shmem_getpage(inode, end, &page, SGP_READ, NULL);
 525                 if (page) {
 526                         zero_user_segment(page, 0, partial_end);
 527                         set_page_dirty(page);
 528                         unlock_page(page);
 529                         page_cache_release(page);
 530                 }
 531         }
 532         if (start >= end)
 533                 return;
 534
 535         index = start;
 536         for ( ; ; ) {
 537                 cond_resched();
 538                 pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
 539                                 min(end - index, (pgoff_t)PAGEVEC_SIZE),
 540                                                         pvec.pages, indices);
 541                 if (!pvec.nr) {
 542                         if (index == start || unfalloc)
 543                                 break;
 544                         index = start;
 545                         continue;
 546                 }
 547                 if ((index == start || unfalloc) && indices[0] >= end) {
 548                         shmem_deswap_pagevec(&pvec);
 549                         pagevec_release(&pvec);
 550                         break;
 551                 }
 552                 mem_cgroup_uncharge_start();
 553                 for (i = 0; i < pagevec_count(&pvec); i++) {
 554                         struct page *page = pvec.pages[i];
 555
 556                         index = indices[i];
 557                         if (index >= end)
 558                                 break;
 559
 560                         if (radix_tree_exceptional_entry(page)) {
 561                                 if (unfalloc)
 562                                         continue;
 563                                 nr_swaps_freed += !shmem_free_swap(mapping,
 564                                                                 index, page);
 565                                 continue;
 566                         }
 567
 568                         lock_page(page);
 569                         if (!unfalloc || !PageUptodate(page)) {
 570                                 if (page->mapping == mapping) {
 571                                         VM_BUG_ON(PageWriteback(page));
 572                                         truncate_inode_page(mapping, page);
 573                                 }
 574                         }
 575                         unlock_page(page);
 576                 }
 577                 shmem_deswap_pagevec(&pvec);
 578                 pagevec_release(&pvec);
 579                 mem_cgroup_uncharge_end();
 580                 index++;
 581         }
 582
 583         spin_lock(&info->lock);
 584         info->swapped -= nr_swaps_freed;
 585         shmem_recalc_inode(inode);
 586         spin_unlock(&info->lock);
 587 }
 588
 589 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
 590 {
 591         shmem_undo_range(inode, lstart, lend, false);
 592         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
 593 }
 594 EXPORT_SYMBOL_GPL(shmem_truncate_range);
 595
 596 static int shmem_setattr(struct dentry *dentry, struct iattr *attr)
 597 {
 598         struct inode *inode = dentry->d_inode;
 599         int error;
 600
 601         error = inode_change_ok(inode, attr);
 602         if (error)
 603                 return error;
 604
 605         if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
 606                 loff_t oldsize = inode->i_size;
 607                 loff_t newsize = attr->ia_size;
 608
 609                 if (newsize != oldsize) {
 610                         i_size_write(inode, newsize);
 611                         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
 612                 }
 613                 if (newsize < oldsize) {
 614                         loff_t holebegin = round_up(newsize, PAGE_SIZE);
 615                         unmap_mapping_range(inode->i_mapping, holebegin, 0, 1);
 616                         shmem_truncate_range(inode, newsize, (loff_t)-1);
 617                         /* unmap again to remove racily COWed private pages */
 618                         unmap_mapping_range(inode->i_mapping, holebegin, 0, 1);
 619                 }
 620         }
 621
 622         setattr_copy(inode, attr);
 623 #ifdef CONFIG_TMPFS_POSIX_ACL
 624         if (attr->ia_valid & ATTR_MODE)
 625                 error = generic_acl_chmod(inode);
 626 #endif
 627         return error;
 628 }
 629
 630 static void shmem_evict_inode(struct inode *inode)
 631 {
 632         struct shmem_inode_info *info = SHMEM_I(inode);
 633
 634         if (inode->i_mapping->a_ops == &shmem_aops) {
 635                 shmem_unacct_size(info->flags, inode->i_size);
 636                 inode->i_size = 0;
 637                 shmem_truncate_range(inode, 0, (loff_t)-1);
 638                 if (!list_empty(&info->swaplist)) {
 639                         mutex_lock(&shmem_swaplist_mutex);
 640                         list_del_init(&info->swaplist);
 641                         mutex_unlock(&shmem_swaplist_mutex);
 642                 }
 643         } else
 644                 kfree(info->symlink);
 645
 646         simple_xattrs_free(&info->xattrs);
 647         WARN_ON(inode->i_blocks);
 648         shmem_free_inode(inode->i_sb);
 649         clear_inode(inode);
 650 }
 651
 652 /*
 653  * If swap found in inode, free it and move page from swapcache to filecache.
 654  */
 655 static int shmem_unuse_inode(struct shmem_inode_info *info,
 656                              swp_entry_t swap, struct page **pagep)
 657 {
 658         struct address_space *mapping = info->vfs_inode.i_mapping;
 659         void *radswap;
 660         pgoff_t index;
 661         gfp_t gfp;
 662         int error = 0;
 663
 664         radswap = swp_to_radix_entry(swap);
 665         index = radix_tree_locate_item(&mapping->page_tree, radswap);
 666         if (index == -1)
 667                 return 0;
 668
 669         /*
 670          * Move _head_ to start search for next from here.
 671          * But be careful: shmem_evict_inode checks list_empty without taking
 672          * mutex, and there's an instant in list_move_tail when info->swaplist
 673          * would appear empty, if it were the only one on shmem_swaplist.
 674          */
 675         if (shmem_swaplist.next != &info->swaplist)
 676                 list_move_tail(&shmem_swaplist, &info->swaplist);
 677
 678         gfp = mapping_gfp_mask(mapping);
 679         if (shmem_should_replace_page(*pagep, gfp)) {
 680                 mutex_unlock(&shmem_swaplist_mutex);
 681                 error = shmem_replace_page(pagep, gfp, info, index);
 682                 mutex_lock(&shmem_swaplist_mutex);
 683                 /*
 684                  * We needed to drop mutex to make that restrictive page
 685                  * allocation, but the inode might have been freed while we
 686                  * dropped it: although a racing shmem_evict_inode() cannot
 687                  * complete without emptying the radix_tree, our page lock
 688                  * on this swapcache page is not enough to prevent that -
 689                  * free_swap_and_cache() of our swap entry will only
 690                  * trylock_page(), removing swap from radix_tree whatever.
 691                  *
 692                  * We must not proceed to shmem_add_to_page_cache() if the
 693                  * inode has been freed, but of course we cannot rely on
 694                  * inode or mapping or info to check that.  However, we can
 695                  * safely check if our swap entry is still in use (and here
 696                  * it can't have got reused for another page): if it's still
 697                  * in use, then the inode cannot have been freed yet, and we
 698                  * can safely proceed (if it's no longer in use, that tells
 699                  * nothing about the inode, but we don't need to unuse swap).
 700                  */
 701                 if (!page_swapcount(*pagep))
 702                         error = -ENOENT;
 703         }
 704
 705         /*
 706          * We rely on shmem_swaplist_mutex, not only to protect the swaplist,
 707          * but also to hold up shmem_evict_inode(): so inode cannot be freed
 708          * beneath us (pagelock doesn't help until the page is in pagecache).
 709          */
 710         if (!error)
 711                 error = shmem_add_to_page_cache(*pagep, mapping, index,
 712                                                 GFP_NOWAIT, radswap);
 713         if (error != -ENOMEM) {
 714                 /*
 715                  * Truncation and eviction use free_swap_and_cache(), which
 716                  * only does trylock page: if we raced, best clean up here.
 717                  */
 718                 delete_from_swap_cache(*pagep);
 719                 set_page_dirty(*pagep);
 720                 if (!error) {
 721                         spin_lock(&info->lock);
 722                         info->swapped--;
 723                         spin_unlock(&info->lock);
 724                         swap_free(swap);
 725                 }
 726                 error = 1;      /* not an error, but entry was found */
 727         }
 728         return error;
 729 }
 730
 731 /*
 732  * Search through swapped inodes to find and replace swap by page.
 733  */
 734 int shmem_unuse(swp_entry_t swap, struct page *page)
 735 {
 736         struct list_head *this, *next;
 737         struct shmem_inode_info *info;
 738         int found = 0;
 739         int error = 0;
 740
 741         /*
 742          * There's a faint possibility that swap page was replaced before
 743          * caller locked it: caller will come back later with the right page.
 744          */
 745         if (unlikely(!PageSwapCache(page) || page_private(page) != swap.val))
 746                 goto out;
 747
 748         /*
 749          * Charge page using GFP_KERNEL while we can wait, before taking
 750          * the shmem_swaplist_mutex which might hold up shmem_writepage().
 751          * Charged back to the user (not to caller) when swap account is used.
 752          */
 753         error = mem_cgroup_cache_charge(page, current->mm, GFP_KERNEL);
 754         if (error)
 755                 goto out;
 756         /* No radix_tree_preload: swap entry keeps a place for page in tree */
 757
 758         mutex_lock(&shmem_swaplist_mutex);
 759         list_for_each_safe(this, next, &shmem_swaplist) {
 760                 info = list_entry(this, struct shmem_inode_info, swaplist);
 761                 if (info->swapped)
 762                         found = shmem_unuse_inode(info, swap, &page);
 763                 else
 764                         list_del_init(&info->swaplist);
 765                 cond_resched();
 766                 if (found)
 767                         break;
 768         }
 769         mutex_unlock(&shmem_swaplist_mutex);
 770
 771         if (found < 0)
 772                 error = found;
 773 out:
 774         unlock_page(page);
 775         page_cache_release(page);
 776         return error;
 777 }
 778
 779 /*
 780  * Move the page from the page cache to the swap cache.
 781  */
 782 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 783 {
 784         struct shmem_inode_info *info;
 785         struct address_space *mapping;
 786         struct inode *inode;
 787         swp_entry_t swap;
 788         pgoff_t index;
 789
 790         BUG_ON(!PageLocked(page));
 791         mapping = page->mapping;
 792         index = page->index;
 793         inode = mapping->host;
 794         info = SHMEM_I(inode);
 795         if (info->flags & VM_LOCKED)
 796                 goto redirty;
 797         if (!total_swap_pages)
 798                 goto redirty;
 799
 800         /*
 801          * shmem_backing_dev_info's capabilities prevent regular writeback or
 802          * sync from ever calling shmem_writepage; but a stacking filesystem
 803          * might use ->writepage of its underlying filesystem, in which case
 804          * tmpfs should write out to swap only in response to memory pressure,
 805          * and not for the writeback threads or sync.
 806          */
 807         if (!wbc->for_reclaim) {
 808                 WARN_ON_ONCE(1);        /* Still happens? Tell us about it! */
 809                 goto redirty;
 810         }
 811
 812         /*
 813          * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC
 814          * value into swapfile.c, the only way we can correctly account for a
 815          * fallocated page arriving here is now to initialize it and write it.
 816          *
 817          * That's okay for a page already fallocated earlier, but if we have
 818          * not yet completed the fallocation, then (a) we want to keep track
 819          * of this page in case we have to undo it, and (b) it may not be a
 820          * good idea to continue anyway, once we're pushing into swap.  So
 821          * reactivate the page, and let shmem_fallocate() quit when too many.
 822          */
 823         if (!PageUptodate(page)) {
 824                 if (inode->i_private) {
 825                         struct shmem_falloc *shmem_falloc;
 826                         spin_lock(&inode->i_lock);
 827                         shmem_falloc = inode->i_private;
 828                         if (shmem_falloc &&
 829                             index >= shmem_falloc->start &&
 830                             index < shmem_falloc->next)
 831                                 shmem_falloc->nr_unswapped++;
 832                         else
 833                                 shmem_falloc = NULL;
 834                         spin_unlock(&inode->i_lock);
 835                         if (shmem_falloc)
 836                                 goto redirty;
 837                 }
 838                 clear_highpage(page);
 839                 flush_dcache_page(page);
 840                 SetPageUptodate(page);
 841         }
 842
 843         swap = get_swap_page();
 844         if (!swap.val)
 845                 goto redirty;
 846
 847         /*
 848          * Add inode to shmem_unuse()'s list of swapped-out inodes,
 849          * if it's not already there.  Do it now before the page is
 850          * moved to swap cache, when its pagelock no longer protects
 851          * the inode from eviction.  But don't unlock the mutex until
 852          * we've incremented swapped, because shmem_unuse_inode() will
 853          * prune a !swapped inode from the swaplist under this mutex.
 854          */
 855         mutex_lock(&shmem_swaplist_mutex);
 856         if (list_empty(&info->swaplist))
 857                 list_add_tail(&info->swaplist, &shmem_swaplist);
 858
 859         if (add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
 860                 swap_shmem_alloc(swap);
 861                 shmem_delete_from_page_cache(page, swp_to_radix_entry(swap));
 862
 863                 spin_lock(&info->lock);
 864                 info->swapped++;
 865                 shmem_recalc_inode(inode);
 866                 spin_unlock(&info->lock);
 867
 868                 mutex_unlock(&shmem_swaplist_mutex);
 869                 BUG_ON(page_mapped(page));
 870                 swap_writepage(page, wbc);
 871                 return 0;
 872         }
 873
 874         mutex_unlock(&shmem_swaplist_mutex);
 875         swapcache_free(swap, NULL);
 876 redirty:
 877         set_page_dirty(page);
 878         if (wbc->for_reclaim)
 879                 return AOP_WRITEPAGE_ACTIVATE;  /* Return with page locked */
 880         unlock_page(page);
 881         return 0;
 882 }
 883
 884 #ifdef CONFIG_NUMA
 885 #ifdef CONFIG_TMPFS
 886 static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
 887 {
 888         char buffer[64];
 889
 890         if (!mpol || mpol->mode == MPOL_DEFAULT)
 891                 return;         /* show nothing */
 892
 893         mpol_to_str(buffer, sizeof(buffer), mpol);
 894
 895         seq_printf(seq, ",mpol=%s", buffer);
 896 }
 897
 898 static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
 899 {
 900         struct mempolicy *mpol = NULL;
 901         if (sbinfo->mpol) {
 902                 spin_lock(&sbinfo->stat_lock);  /* prevent replace/use races */
 903                 mpol = sbinfo->mpol;
 904                 mpol_get(mpol);
 905                 spin_unlock(&sbinfo->stat_lock);
 906         }
 907         return mpol;
 908 }
 909 #endif /* CONFIG_TMPFS */
 910
 911 static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
 912                         struct shmem_inode_info *info, pgoff_t index)
 913 {
 914         struct vm_area_struct pvma;
 915         struct page *page;
 916
 917         /* Create a pseudo vma that just contains the policy */
 918         pvma.vm_start = 0;
 919         /* Bias interleave by inode number to distribute better across nodes */
 920         pvma.vm_pgoff = index + info->vfs_inode.i_ino;
 921         pvma.vm_ops = NULL;
 922         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
 923
 924         page = swapin_readahead(swap, gfp, &pvma, 0);
 925
 926         /* Drop reference taken by mpol_shared_policy_lookup() */
 927         mpol_cond_put(pvma.vm_policy);
 928
 929         return page;
 930 }
 931
 932 static struct page *shmem_alloc_page(gfp_t gfp,
 933                         struct shmem_inode_info *info, pgoff_t index)
 934 {
 935         struct vm_area_struct pvma;
 936         struct page *page;
 937
 938         /* Create a pseudo vma that just contains the policy */
 939         pvma.vm_start = 0;
 940         /* Bias interleave by inode number to distribute better across nodes */
 941         pvma.vm_pgoff = index + info->vfs_inode.i_ino;
 942         pvma.vm_ops = NULL;
 943         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
 944
 945         page = alloc_page_vma(gfp, &pvma, 0);
 946
 947         /* Drop reference taken by mpol_shared_policy_lookup() */
 948         mpol_cond_put(pvma.vm_policy);
 949
 950         return page;
 951 }
 952 #else /* !CONFIG_NUMA */
 953 #ifdef CONFIG_TMPFS
 954 static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
 955 {
 956 }
 957 #endif /* CONFIG_TMPFS */
 958
 959 static inline struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
 960                         struct shmem_inode_info *info, pgoff_t index)
 961 {
 962         return swapin_readahead(swap, gfp, NULL, 0);
 963 }
 964
 965 static inline struct page *shmem_alloc_page(gfp_t gfp,
 966                         struct shmem_inode_info *info, pgoff_t index)
 967 {
 968         return alloc_page(gfp);
 969 }
 970 #endif /* CONFIG_NUMA */
 971
 972 #if !defined(CONFIG_NUMA) || !defined(CONFIG_TMPFS)
 973 static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
 974 {
 975         return NULL;
 976 }
 977 #endif
 978
 979 /*
 980  * When a page is moved from swapcache to shmem filecache (either by the
 981  * usual swapin of shmem_getpage_gfp(), or by the less common swapoff of
 982  * shmem_unuse_inode()), it may have been read in earlier from swap, in
 983  * ignorance of the mapping it belongs to.  If that mapping has special
 984  * constraints (like the gma500 GEM driver, which requires RAM below 4GB),
 985  * we may need to copy to a suitable page before moving to filecache.
 986  *
 987  * In a future release, this may well be extended to respect cpuset and
 988  * NUMA mempolicy, and applied also to anonymous pages in do_swap_page();
 989  * but for now it is a simple matter of zone.
 990  */
 991 static bool shmem_should_replace_page(struct page *page, gfp_t gfp)
 992 {
 993         return page_zonenum(page) > gfp_zone(gfp);
 994 }
 995
 996 static int shmem_replace_page(struct page **pagep, gfp_t gfp,
 997                                 struct shmem_inode_info *info, pgoff_t index)
 998 {
 999         struct page *oldpage, *newpage;
1000         struct address_space *swap_mapping;
1001         pgoff_t swap_index;
1002         int error;
1003
1004         oldpage = *pagep;
1005         swap_index = page_private(oldpage);
1006         swap_mapping = page_mapping(oldpage);
1007
1008         /*
1009          * We have arrived here because our zones are constrained, so don't
1010          * limit chance of success by further cpuset and node constraints.
1011          */
1012         gfp &= ~GFP_CONSTRAINT_MASK;
1013         newpage = shmem_alloc_page(gfp, info, index);
1014         if (!newpage)
1015                 return -ENOMEM;
1016
1017         page_cache_get(newpage);
1018         copy_highpage(newpage, oldpage);
1019         flush_dcache_page(newpage);
1020
1021         __set_page_locked(newpage);
1022         SetPageUptodate(newpage);
1023         SetPageSwapBacked(newpage);
1024         set_page_private(newpage, swap_index);
1025         SetPageSwapCache(newpage);
1026
1027         /*
1028          * Our caller will very soon move newpage out of swapcache, but it's
1029          * a nice clean interface for us to replace oldpage by newpage there.
1030          */
1031         spin_lock_irq(&swap_mapping->tree_lock);
1032         error = shmem_radix_tree_replace(swap_mapping, swap_index, oldpage,
1033                                                                    newpage);
1034         if (!error) {
1035                 __inc_zone_page_state(newpage, NR_FILE_PAGES);
1036                 __dec_zone_page_state(oldpage, NR_FILE_PAGES);
1037         }
1038         spin_unlock_irq(&swap_mapping->tree_lock);
1039
1040         if (unlikely(error)) {
1041                 /*
1042                  * Is this possible?  I think not, now that our callers check
1043                  * both PageSwapCache and page_private after getting page lock;
1044                  * but be defensive.  Reverse old to newpage for clear and free.
1045                  */
1046                 oldpage = newpage;
1047         } else {
1048                 mem_cgroup_replace_page_cache(oldpage, newpage);
1049                 lru_cache_add_anon(newpage);
1050                 *pagep = newpage;
1051         }
1052
1053         ClearPageSwapCache(oldpage);
1054         set_page_private(oldpage, 0);
1055
1056         unlock_page(oldpage);
1057         page_cache_release(oldpage);
1058         page_cache_release(oldpage);
1059         return error;
1060 }
1061
1062 /*
1063  * shmem_getpage_gfp - find page in cache, or get from swap, or allocate
1064  *
1065  * If we allocate a new one we do not mark it dirty. That's up to the
1066  * vm. If we swap it in we mark it dirty since we also free the swap
1067  * entry since a page cannot live in both the swap and page cache
1068  */
1069 static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
1070         struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type)
1071 {
1072         struct address_space *mapping = inode->i_mapping;
1073         struct shmem_inode_info *info;
1074         struct shmem_sb_info *sbinfo;
1075         struct page *page;
1076         swp_entry_t swap;
1077         int error;
1078         int once = 0;
1079         int alloced = 0;
1080
1081         if (index > (MAX_LFS_FILESIZE >> PAGE_CACHE_SHIFT))
1082                 return -EFBIG;
1083 repeat:
1084         swap.val = 0;
1085         page = find_lock_page(mapping, index);
1086         if (radix_tree_exceptional_entry(page)) {
1087                 swap = radix_to_swp_entry(page);
1088                 page = NULL;
1089         }
1090
1091         if (sgp != SGP_WRITE && sgp != SGP_FALLOC &&
1092             ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
1093                 error = -EINVAL;
1094                 goto failed;
1095         }
1096
1097         /* fallocated page? */
1098         if (page && !PageUptodate(page)) {
1099                 if (sgp != SGP_READ)
1100                         goto clear;
1101                 unlock_page(page);
1102                 page_cache_release(page);
1103                 page = NULL;
1104         }
1105         if (page || (sgp == SGP_READ && !swap.val)) {
1106                 *pagep = page;
1107                 return 0;
1108         }
1109
1110         /*
1111          * Fast cache lookup did not find it:
1112          * bring it back from swap or allocate.
1113          */
1114         info = SHMEM_I(inode);
1115         sbinfo = SHMEM_SB(inode->i_sb);
1116
1117         if (swap.val) {
1118                 /* Look it up and read it in.. */
1119                 page = lookup_swap_cache(swap);
1120                 if (!page) {
1121                         /* here we actually do the io */
1122                         if (fault_type)
1123                                 *fault_type |= VM_FAULT_MAJOR;
1124                         page = shmem_swapin(swap, gfp, info, index);
1125                         if (!page) {
1126                                 error = -ENOMEM;
1127                                 goto failed;
1128                         }
1129                 }
1130
1131                 /* We have to do this with page locked to prevent races */
1132                 lock_page(page);
1133                 if (!PageSwapCache(page) || page_private(page) != swap.val ||
1134                     !shmem_confirm_swap(mapping, index, swap)) {
1135                         error = -EEXIST;        /* try again */
1136                         goto unlock;
1137                 }
1138                 if (!PageUptodate(page)) {
1139                         error = -EIO;
1140                         goto failed;
1141                 }
1142                 wait_on_page_writeback(page);
1143
1144                 if (shmem_should_replace_page(page, gfp)) {
1145                         error = shmem_replace_page(&page, gfp, info, index);
1146                         if (error)
1147                                 goto failed;
1148                 }
1149
1150                 error = mem_cgroup_cache_charge(page, current->mm,
1151                                                 gfp & GFP_RECLAIM_MASK);
1152                 if (!error) {
1153                         error = shmem_add_to_page_cache(page, mapping, index,
1154                                                 gfp, swp_to_radix_entry(swap));
1155                         /*
1156                          * We already confirmed swap under page lock, and make
1157                          * no memory allocation here, so usually no possibility
1158                          * of error; but free_swap_and_cache() only trylocks a
1159                          * page, so it is just possible that the entry has been
1160                          * truncated or holepunched since swap was confirmed.
1161                          * shmem_undo_range() will have done some of the
1162                          * unaccounting, now delete_from_swap_cache() will do
1163                          * the rest (including mem_cgroup_uncharge_swapcache).
1164                          * Reset swap.val? No, leave it so "failed" goes back to
1165                          * "repeat": reading a hole and writing should succeed.
1166                          */
1167                         if (error)
1168                                 delete_from_swap_cache(page);
1169                 }
1170                 if (error)
1171                         goto failed;
1172
1173                 spin_lock(&info->lock);
1174                 info->swapped--;
1175                 shmem_recalc_inode(inode);
1176                 spin_unlock(&info->lock);
1177
1178                 delete_from_swap_cache(page);
1179                 set_page_dirty(page);
1180                 swap_free(swap);
1181
1182         } else {
1183                 if (shmem_acct_block(info->flags)) {
1184                         error = -ENOSPC;
1185                         goto failed;
1186                 }
1187                 if (sbinfo->max_blocks) {
1188                         if (percpu_counter_compare(&sbinfo->used_blocks,
1189                                                 sbinfo->max_blocks) >= 0) {
1190                                 error = -ENOSPC;
1191                                 goto unacct;
1192                         }
1193                         percpu_counter_inc(&sbinfo->used_blocks);
1194                 }
1195
1196                 page = shmem_alloc_page(gfp, info, index);
1197                 if (!page) {
1198                         error = -ENOMEM;
1199                         goto decused;
1200                 }
1201
1202                 SetPageSwapBacked(page);
1203                 __set_page_locked(page);
1204                 error = mem_cgroup_cache_charge(page, current->mm,
1205                                                 gfp & GFP_RECLAIM_MASK);
1206                 if (error)
1207                         goto decused;
1208                 error = radix_tree_preload(gfp & GFP_RECLAIM_MASK);
1209                 if (!error) {
1210                         error = shmem_add_to_page_cache(page, mapping, index,
1211                                                         gfp, NULL);
1212                         radix_tree_preload_end();
1213                 }
1214                 if (error) {
1215                         mem_cgroup_uncharge_cache_page(page);
1216                         goto decused;
1217                 }
1218                 lru_cache_add_anon(page);
1219
1220                 spin_lock(&info->lock);
1221                 info->alloced++;
1222                 inode->i_blocks += BLOCKS_PER_PAGE;
1223                 shmem_recalc_inode(inode);
1224                 spin_unlock(&info->lock);
1225                 alloced = true;
1226
1227                 /*
1228                  * Let SGP_FALLOC use the SGP_WRITE optimization on a new page.
1229                  */
1230                 if (sgp == SGP_FALLOC)
1231                         sgp = SGP_WRITE;
1232 clear:
1233                 /*
1234                  * Let SGP_WRITE caller clear ends if write does not fill page;
1235                  * but SGP_FALLOC on a page fallocated earlier must initialize
1236                  * it now, lest undo on failure cancel our earlier guarantee.
1237                  */
1238                 if (sgp != SGP_WRITE) {
1239                         clear_highpage(page);
1240                         flush_dcache_page(page);
1241                         SetPageUptodate(page);
1242                 }
1243                 if (sgp == SGP_DIRTY)
1244                         set_page_dirty(page);
1245         }
1246
1247         /* Perhaps the file has been truncated since we checked */
1248         if (sgp != SGP_WRITE && sgp != SGP_FALLOC &&
1249             ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
1250                 error = -EINVAL;
1251                 if (alloced)
1252                         goto trunc;
1253                 else
1254                         goto failed;
1255         }
1256         *pagep = page;
1257         return 0;
1258
1259         /*
1260          * Error recovery.
1261          */
1262 trunc:
1263         info = SHMEM_I(inode);
1264         ClearPageDirty(page);
1265         delete_from_page_cache(page);
1266         spin_lock(&info->lock);
1267         info->alloced--;
1268         inode->i_blocks -= BLOCKS_PER_PAGE;
1269         spin_unlock(&info->lock);
1270 decused:
1271         sbinfo = SHMEM_SB(inode->i_sb);
1272         if (sbinfo->max_blocks)
1273                 percpu_counter_add(&sbinfo->used_blocks, -1);
1274 unacct:
1275         shmem_unacct_blocks(info->flags, 1);
1276 failed:
1277         if (swap.val && error != -EINVAL &&
1278             !shmem_confirm_swap(mapping, index, swap))
1279                 error = -EEXIST;
1280 unlock:
1281         if (page) {
1282                 unlock_page(page);
1283                 page_cache_release(page);
1284         }
1285         if (error == -ENOSPC && !once++) {
1286                 info = SHMEM_I(inode);
1287                 spin_lock(&info->lock);
1288                 shmem_recalc_inode(inode);
1289                 spin_unlock(&info->lock);
1290                 goto repeat;
1291         }
1292         if (error == -EEXIST)   /* from above or from radix_tree_insert */
1293                 goto repeat;
1294         return error;
1295 }
1296
1297 static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1298 {
1299         struct inode *inode = file_inode(vma->vm_file);
1300         int error;
1301         int ret = VM_FAULT_LOCKED;
1302
1303         error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret);
1304         if (error)
1305                 return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1306
1307         if (ret & VM_FAULT_MAJOR) {
1308                 count_vm_event(PGMAJFAULT);
1309                 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1310         }
1311         return ret;
1312 }
1313
1314 #ifdef CONFIG_NUMA
1315 static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *mpol)
1316 {
1317         struct inode *inode = file_inode(vma->vm_file);
1318         return mpol_set_shared_policy(&SHMEM_I(inode)->policy, vma, mpol);
1319 }
1320
1321 static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
1322                                           unsigned long addr)
1323 {
1324         struct inode *inode = file_inode(vma->vm_file);
1325         pgoff_t index;
1326
1327         index = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1328         return mpol_shared_policy_lookup(&SHMEM_I(inode)->policy, index);
1329 }
1330 #endif
1331
1332 int shmem_lock(struct file *file, int lock, struct user_struct *user)
1333 {
1334         struct inode *inode = file_inode(file);
1335         struct shmem_inode_info *info = SHMEM_I(inode);
1336         int retval = -ENOMEM;
1337
1338         spin_lock(&info->lock);
1339         if (lock && !(info->flags & VM_LOCKED)) {
1340                 if (!user_shm_lock(inode->i_size, user))
1341                         goto out_nomem;
1342                 info->flags |= VM_LOCKED;
1343                 mapping_set_unevictable(file->f_mapping);
1344         }
1345         if (!lock && (info->flags & VM_LOCKED) && user) {
1346                 user_shm_unlock(inode->i_size, user);
1347                 info->flags &= ~VM_LOCKED;
1348                 mapping_clear_unevictable(file->f_mapping);
1349         }
1350         retval = 0;
1351
1352 out_nomem:
1353         spin_unlock(&info->lock);
1354         return retval;
1355 }
1356
1357 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1358 {
1359         file_accessed(file);
1360         vma->vm_ops = &shmem_vm_ops;
1361         return 0;
1362 }
1363
1364 static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir,
1365                                      umode_t mode, dev_t dev, unsigned long flags)
1366 {
1367         struct inode *inode;
1368         struct shmem_inode_info *info;
1369         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1370
1371         if (shmem_reserve_inode(sb))
1372                 return NULL;
1373
1374         inode = new_inode(sb);
1375         if (inode) {
1376                 inode->i_ino = get_next_ino();
1377                 inode_init_owner(inode, dir, mode);
1378                 inode->i_blocks = 0;
1379                 inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1380                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1381                 inode->i_generation = get_seconds();
1382                 info = SHMEM_I(inode);
1383                 memset(info, 0, (char *)inode - (char *)info);
1384                 spin_lock_init(&info->lock);
1385                 info->flags = flags & VM_NORESERVE;
1386                 INIT_LIST_HEAD(&info->swaplist);
1387                 simple_xattrs_init(&info->xattrs);
1388                 cache_no_acl(inode);
1389
1390                 switch (mode & S_IFMT) {
1391                 default:
1392                         inode->i_op = &shmem_special_inode_operations;
1393                         init_special_inode(inode, mode, dev);
1394                         break;
1395                 case S_IFREG:
1396                         inode->i_mapping->a_ops = &shmem_aops;
1397                         inode->i_op = &shmem_inode_operations;
1398                         inode->i_fop = &shmem_file_operations;
1399                         mpol_shared_policy_init(&info->policy,
1400                                                  shmem_get_sbmpol(sbinfo));
1401                         break;
1402                 case S_IFDIR:
1403                         inc_nlink(inode);
1404                         /* Some things misbehave if size == 0 on a directory */
1405                         inode->i_size = 2 * BOGO_DIRENT_SIZE;
1406                         inode->i_op = &shmem_dir_inode_operations;
1407                         inode->i_fop = &simple_dir_operations;
1408                         break;
1409                 case S_IFLNK:
1410                         /*
1411                          * Must not load anything in the rbtree,
1412                          * mpol_free_shared_policy will not be called.
1413                          */
1414                         mpol_shared_policy_init(&info->policy, NULL);
1415                         break;
1416                 }
1417         } else
1418                 shmem_free_inode(sb);
1419         return inode;
1420 }
1421
1422 #ifdef CONFIG_TMPFS
1423 static const struct inode_operations shmem_symlink_inode_operations;
1424 static const struct inode_operations shmem_short_symlink_operations;
1425
1426 #ifdef CONFIG_TMPFS_XATTR
1427 static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
1428 #else
1429 #define shmem_initxattrs NULL
1430 #endif
1431
1432 static int
1433 shmem_write_begin(struct file *file, struct address_space *mapping,
1434                         loff_t pos, unsigned len, unsigned flags,
1435                         struct page **pagep, void **fsdata)
1436 {
1437         struct inode *inode = mapping->host;
1438         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1439         return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
1440 }
1441
1442 static int
1443 shmem_write_end(struct file *file, struct address_space *mapping,
1444                         loff_t pos, unsigned len, unsigned copied,
1445                         struct page *page, void *fsdata)
1446 {
1447         struct inode *inode = mapping->host;
1448
1449         if (pos + copied > inode->i_size)
1450                 i_size_write(inode, pos + copied);
1451
1452         if (!PageUptodate(page)) {
1453                 if (copied < PAGE_CACHE_SIZE) {
1454                         unsigned from = pos & (PAGE_CACHE_SIZE - 1);
1455                         zero_user_segments(page, 0, from,
1456                                         from + copied, PAGE_CACHE_SIZE);
1457                 }
1458                 SetPageUptodate(page);
1459         }
1460         set_page_dirty(page);
1461         unlock_page(page);
1462         page_cache_release(page);
1463
1464         return copied;
1465 }
1466
1467 static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
1468 {
1469         struct inode *inode = file_inode(filp);
1470         struct address_space *mapping = inode->i_mapping;
1471         pgoff_t index;
1472         unsigned long offset;
1473         enum sgp_type sgp = SGP_READ;
1474
1475         /*
1476          * Might this read be for a stacking filesystem?  Then when reading
1477          * holes of a sparse file, we actually need to allocate those pages,
1478          * and even mark them dirty, so it cannot exceed the max_blocks limit.
1479          */
1480         if (segment_eq(get_fs(), KERNEL_DS))
1481                 sgp = SGP_DIRTY;
1482
1483         index = *ppos >> PAGE_CACHE_SHIFT;
1484         offset = *ppos & ~PAGE_CACHE_MASK;
1485
1486         for (;;) {
1487                 struct page *page = NULL;
1488                 pgoff_t end_index;
1489                 unsigned long nr, ret;
1490                 loff_t i_size = i_size_read(inode);
1491
1492                 end_index = i_size >> PAGE_CACHE_SHIFT;
1493                 if (index > end_index)
1494                         break;
1495                 if (index == end_index) {
1496                         nr = i_size & ~PAGE_CACHE_MASK;
1497                         if (nr <= offset)
1498                                 break;
1499                 }
1500
1501                 desc->error = shmem_getpage(inode, index, &page, sgp, NULL);
1502                 if (desc->error) {
1503                         if (desc->error == -EINVAL)
1504                                 desc->error = 0;
1505                         break;
1506                 }
1507                 if (page)
1508                         unlock_page(page);
1509
1510                 /*
1511                  * We must evaluate after, since reads (unlike writes)
1512                  * are called without i_mutex protection against truncate
1513                  */
1514                 nr = PAGE_CACHE_SIZE;
1515                 i_size = i_size_read(inode);
1516                 end_index = i_size >> PAGE_CACHE_SHIFT;
1517                 if (index == end_index) {
1518                         nr = i_size & ~PAGE_CACHE_MASK;
1519                         if (nr <= offset) {
1520                                 if (page)
1521                                         page_cache_release(page);
1522                                 break;
1523                         }
1524                 }
1525                 nr -= offset;
1526
1527                 if (page) {
1528                         /*
1529                          * If users can be writing to this page using arbitrary
1530                          * virtual addresses, take care about potential aliasing
1531                          * before reading the page on the kernel side.
1532                          */
1533                         if (mapping_writably_mapped(mapping))
1534                                 flush_dcache_page(page);
1535                         /*
1536                          * Mark the page accessed if we read the beginning.
1537                          */
1538                         if (!offset)
1539                                 mark_page_accessed(page);
1540                 } else {
1541                         page = ZERO_PAGE(0);
1542                         page_cache_get(page);
1543                 }
1544
1545                 /*
1546                  * Ok, we have the page, and it's up-to-date, so
1547                  * now we can copy it to user space...
1548                  *
1549                  * The actor routine returns how many bytes were actually used..
1550                  * NOTE! This may not be the same as how much of a user buffer
1551                  * we filled up (we may be padding etc), so we can only update
1552                  * "pos" here (the actor routine has to update the user buffer
1553                  * pointers and the remaining count).
1554                  */
1555                 ret = actor(desc, page, offset, nr);
1556                 offset += ret;
1557                 index += offset >> PAGE_CACHE_SHIFT;
1558                 offset &= ~PAGE_CACHE_MASK;
1559
1560                 page_cache_release(page);
1561                 if (ret != nr || !desc->count)
1562                         break;
1563
1564                 cond_resched();
1565         }
1566
1567         *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1568         file_accessed(filp);
1569 }
1570
1571 static ssize_t shmem_file_aio_read(struct kiocb *iocb,
1572                 const struct iovec *iov, unsigned long nr_segs, loff_t pos)
1573 {
1574         struct file *filp = iocb->ki_filp;
1575         ssize_t retval;
1576         unsigned long seg;
1577         size_t count;
1578         loff_t *ppos = &iocb->ki_pos;
1579
1580         retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1581         if (retval)
1582                 return retval;
1583
1584         for (seg = 0; seg < nr_segs; seg++) {
1585                 read_descriptor_t desc;
1586
1587                 desc.written = 0;
1588                 desc.arg.buf = iov[seg].iov_base;
1589                 desc.count = iov[seg].iov_len;
1590                 if (desc.count == 0)
1591                         continue;
1592                 desc.error = 0;
1593                 do_shmem_file_read(filp, ppos, &desc, file_read_actor);
1594                 retval += desc.written;
1595                 if (desc.error) {
1596                         retval = retval ?: desc.error;
1597                         break;
1598                 }
1599                 if (desc.count > 0)
1600                         break;
1601         }
1602         return retval;
1603 }
1604
1605 static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
1606                                 struct pipe_inode_info *pipe, size_t len,
1607                                 unsigned int flags)
1608 {
1609         struct address_space *mapping = in->f_mapping;
1610         struct inode *inode = mapping->host;
1611         unsigned int loff, nr_pages, req_pages;
1612         struct page *pages[PIPE_DEF_BUFFERS];
1613         struct partial_page partial[PIPE_DEF_BUFFERS];
1614         struct page *page;
1615         pgoff_t index, end_index;
1616         loff_t isize, left;
1617         int error, page_nr;
1618         struct splice_pipe_desc spd = {
1619                 .pages = pages,
1620                 .partial = partial,
1621                 .nr_pages_max = PIPE_DEF_BUFFERS,
1622                 .flags = flags,
1623                 .ops = &page_cache_pipe_buf_ops,
1624                 .spd_release = spd_release_page,
1625         };
1626
1627         isize = i_size_read(inode);
1628         if (unlikely(*ppos >= isize))
1629                 return 0;
1630
1631         left = isize - *ppos;
1632         if (unlikely(left < len))
1633                 len = left;
1634
1635         if (splice_grow_spd(pipe, &spd))
1636                 return -ENOMEM;
1637
1638         index = *ppos >> PAGE_CACHE_SHIFT;
1639         loff = *ppos & ~PAGE_CACHE_MASK;
1640         req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1641         nr_pages = min(req_pages, pipe->buffers);
1642
1643         spd.nr_pages = find_get_pages_contig(mapping, index,
1644                                                 nr_pages, spd.pages);
1645         index += spd.nr_pages;
1646         error = 0;
1647
1648         while (spd.nr_pages < nr_pages) {
1649                 error = shmem_getpage(inode, index, &page, SGP_CACHE, NULL);
1650                 if (error)
1651                         break;
1652                 unlock_page(page);
1653                 spd.pages[spd.nr_pages++] = page;
1654                 index++;
1655         }
1656
1657         index = *ppos >> PAGE_CACHE_SHIFT;
1658         nr_pages = spd.nr_pages;
1659         spd.nr_pages = 0;
1660
1661         for (page_nr = 0; page_nr < nr_pages; page_nr++) {
1662                 unsigned int this_len;
1663
1664                 if (!len)
1665                         break;
1666
1667                 this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
1668                 page = spd.pages[page_nr];
1669
1670                 if (!PageUptodate(page) || page->mapping != mapping) {
1671                         error = shmem_getpage(inode, index, &page,
1672                                                         SGP_CACHE, NULL);
1673                         if (error)
1674                                 break;
1675                         unlock_page(page);
1676                         page_cache_release(spd.pages[page_nr]);
1677                         spd.pages[page_nr] = page;
1678                 }
1679
1680                 isize = i_size_read(inode);
1681                 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1682                 if (unlikely(!isize || index > end_index))
1683                         break;
1684
1685                 if (end_index == index) {
1686                         unsigned int plen;
1687
1688                         plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1689                         if (plen <= loff)
1690                                 break;
1691
1692                         this_len = min(this_len, plen - loff);
1693                         len = this_len;
1694                 }
1695
1696                 spd.partial[page_nr].offset = loff;
1697                 spd.partial[page_nr].len = this_len;
1698                 len -= this_len;
1699                 loff = 0;
1700                 spd.nr_pages++;
1701                 index++;
1702         }
1703
1704         while (page_nr < nr_pages)
1705                 page_cache_release(spd.pages[page_nr++]);
1706
1707         if (spd.nr_pages)
1708                 error = splice_to_pipe(pipe, &spd);
1709
1710         splice_shrink_spd(&spd);
1711
1712         if (error > 0) {
1713                 *ppos += error;
1714                 file_accessed(in);
1715         }
1716         return error;
1717 }
1718
1719 /*
1720  * llseek SEEK_DATA or SEEK_HOLE through the radix_tree.
1721  */
1722 static pgoff_t shmem_seek_hole_data(struct address_space *mapping,
1723                                     pgoff_t index, pgoff_t end, int whence)
1724 {
1725         struct page *page;
1726         struct pagevec pvec;
1727         pgoff_t indices[PAGEVEC_SIZE];
1728         bool done = false;
1729         int i;
1730
1731         pagevec_init(&pvec, 0);
1732         pvec.nr = 1;            /* start small: we may be there already */
1733         while (!done) {
1734                 pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
1735                                         pvec.nr, pvec.pages, indices);
1736                 if (!pvec.nr) {
1737                         if (whence == SEEK_DATA)
1738                                 index = end;
1739                         break;
1740                 }
1741                 for (i = 0; i < pvec.nr; i++, index++) {
1742                         if (index < indices[i]) {
1743                                 if (whence == SEEK_HOLE) {
1744                                         done = true;
1745                                         break;
1746                                 }
1747                                 index = indices[i];
1748                         }
1749                         page = pvec.pages[i];
1750                         if (page && !radix_tree_exceptional_entry(page)) {
1751                                 if (!PageUptodate(page))
1752                                         page = NULL;
1753                         }
1754                         if (index >= end ||
1755                             (page && whence == SEEK_DATA) ||
1756                             (!page && whence == SEEK_HOLE)) {
1757                                 done = true;
1758                                 break;
1759                         }
1760                 }
1761                 shmem_deswap_pagevec(&pvec);
1762                 pagevec_release(&pvec);
1763                 pvec.nr = PAGEVEC_SIZE;
1764                 cond_resched();
1765         }
1766         return index;
1767 }
1768
1769 static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence)
1770 {
1771         struct address_space *mapping = file->f_mapping;
1772         struct inode *inode = mapping->host;
1773         pgoff_t start, end;
1774         loff_t new_offset;
1775
1776         if (whence != SEEK_DATA && whence != SEEK_HOLE)
1777                 return generic_file_llseek_size(file, offset, whence,
1778                                         MAX_LFS_FILESIZE, i_size_read(inode));
1779         mutex_lock(&inode->i_mutex);
1780         /* We're holding i_mutex so we can access i_size directly */
1781
1782         if (offset < 0)
1783                 offset = -EINVAL;
1784         else if (offset >= inode->i_size)
1785                 offset = -ENXIO;
1786         else {
1787                 start = offset >> PAGE_CACHE_SHIFT;
1788                 end = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1789                 new_offset = shmem_seek_hole_data(mapping, start, end, whence);
1790                 new_offset <<= PAGE_CACHE_SHIFT;
1791                 if (new_offset > offset) {
1792                         if (new_offset < inode->i_size)
1793                                 offset = new_offset;
1794                         else if (whence == SEEK_DATA)
1795                                 offset = -ENXIO;
1796                         else
1797                                 offset = inode->i_size;
1798                 }
1799         }
1800
1801         offset = vfs_setpos(file, offset, MAX_LFS_FILESIZE);
1802         mutex_unlock(&inode->i_mutex);
1803         return offset;
1804 }
1805
1806 static long shmem_fallocate(struct file *file, int mode, loff_t offset,
1807                                                          loff_t len)
1808 {
1809         struct inode *inode = file_inode(file);
1810         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1811         struct shmem_falloc shmem_falloc;
1812         pgoff_t start, index, end;
1813         int error;
1814
1815         mutex_lock(&inode->i_mutex);
1816
1817         if (mode & FALLOC_FL_PUNCH_HOLE) {
1818                 struct address_space *mapping = file->f_mapping;
1819                 loff_t unmap_start = round_up(offset, PAGE_SIZE);
1820                 loff_t unmap_end = round_down(offset + len, PAGE_SIZE) - 1;
1821
1822                 if ((u64)unmap_end > (u64)unmap_start)
1823                         unmap_mapping_range(mapping, unmap_start,
1824                                             1 + unmap_end - unmap_start, 0);
1825                 shmem_truncate_range(inode, offset, offset + len - 1);
1826                 /* No need to unmap again: hole-punching leaves COWed pages */
1827                 error = 0;
1828                 goto out;
1829         }
1830
1831         /* We need to check rlimit even when FALLOC_FL_KEEP_SIZE */
1832         error = inode_newsize_ok(inode, offset + len);
1833         if (error)
1834                 goto out;
1835
1836         start = offset >> PAGE_CACHE_SHIFT;
1837         end = (offset + len + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1838         /* Try to avoid a swapstorm if len is impossible to satisfy */
1839         if (sbinfo->max_blocks && end - start > sbinfo->max_blocks) {
1840                 error = -ENOSPC;
1841                 goto out;
1842         }
1843
1844         shmem_falloc.start = start;
1845         shmem_falloc.next  = start;
1846         shmem_falloc.nr_falloced = 0;
1847         shmem_falloc.nr_unswapped = 0;
1848         spin_lock(&inode->i_lock);
1849         inode->i_private = &shmem_falloc;
1850         spin_unlock(&inode->i_lock);
1851
1852         for (index = start; index < end; index++) {
1853                 struct page *page;
1854
1855                 /*
1856                  * Good, the fallocate(2) manpage permits EINTR: we may have
1857                  * been interrupted because we are using up too much memory.
1858                  */
1859                 if (signal_pending(current))
1860                         error = -EINTR;
1861                 else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
1862                         error = -ENOMEM;
1863                 else
1864                         error = shmem_getpage(inode, index, &page, SGP_FALLOC,
1865                                                                         NULL);
1866                 if (error) {
1867                         /* Remove the !PageUptodate pages we added */
1868                         shmem_undo_range(inode,
1869                                 (loff_t)start << PAGE_CACHE_SHIFT,
1870                                 (loff_t)index << PAGE_CACHE_SHIFT, true);
1871                         goto undone;
1872                 }
1873
1874                 /*
1875                  * Inform shmem_writepage() how far we have reached.
1876                  * No need for lock or barrier: we have the page lock.
1877                  */
1878                 shmem_falloc.next++;
1879                 if (!PageUptodate(page))
1880                         shmem_falloc.nr_falloced++;
1881
1882                 /*
1883                  * If !PageUptodate, leave it that way so that freeable pages
1884                  * can be recognized if we need to rollback on error later.
1885                  * But set_page_dirty so that memory pressure will swap rather
1886                  * than free the pages we are allocating (and SGP_CACHE pages
1887                  * might still be clean: we now need to mark those dirty too).
1888                  */
1889                 set_page_dirty(page);
1890                 unlock_page(page);
1891                 page_cache_release(page);
1892                 cond_resched();
1893         }
1894
1895         if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
1896                 i_size_write(inode, offset + len);
1897         inode->i_ctime = CURRENT_TIME;
1898 undone:
1899         spin_lock(&inode->i_lock);
1900         inode->i_private = NULL;
1901         spin_unlock(&inode->i_lock);
1902 out:
1903         mutex_unlock(&inode->i_mutex);
1904         return error;
1905 }
1906
1907 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
1908 {
1909         struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
1910
1911         buf->f_type = TMPFS_MAGIC;
1912         buf->f_bsize = PAGE_CACHE_SIZE;
1913         buf->f_namelen = NAME_MAX;
1914         if (sbinfo->max_blocks) {
1915                 buf->f_blocks = sbinfo->max_blocks;
1916                 buf->f_bavail =
1917                 buf->f_bfree  = sbinfo->max_blocks -
1918                                 percpu_counter_sum(&sbinfo->used_blocks);
1919         }
1920         if (sbinfo->max_inodes) {
1921                 buf->f_files = sbinfo->max_inodes;
1922                 buf->f_ffree = sbinfo->free_inodes;
1923         }
1924         /* else leave those fields 0 like simple_statfs */
1925         return 0;
1926 }
1927
1928 /*
1929  * File creation. Allocate an inode, and we're done..
1930  */
1931 static int
1932 shmem_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
1933 {
1934         struct inode *inode;
1935         int error = -ENOSPC;
1936
1937         inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
1938         if (inode) {
1939 #ifdef CONFIG_TMPFS_POSIX_ACL
1940                 error = generic_acl_init(inode, dir);
1941                 if (error) {
1942                         iput(inode);
1943                         return error;
1944                 }
1945 #endif
1946                 error = security_inode_init_security(inode, dir,
1947                                                      &dentry->d_name,
1948                                                      shmem_initxattrs, NULL);
1949                 if (error) {
1950                         if (error != -EOPNOTSUPP) {
1951                                 iput(inode);
1952                                 return error;
1953                         }
1954                 }
1955
1956                 error = 0;
1957                 dir->i_size += BOGO_DIRENT_SIZE;
1958                 dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1959                 d_instantiate(dentry, inode);
1960                 dget(dentry); /* Extra count - pin the dentry in core */
1961         }
1962         return error;
1963 }
1964
1965 static int
1966 shmem_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode)
1967 {
1968         struct inode *inode;
1969         int error = -ENOSPC;
1970
1971         inode = shmem_get_inode(dir->i_sb, dir, mode, 0, VM_NORESERVE);
1972         if (inode) {
1973                 error = security_inode_init_security(inode, dir,
1974                                                      NULL,
1975                                                      shmem_initxattrs, NULL);
1976                 if (error) {
1977                         if (error != -EOPNOTSUPP) {
1978                                 iput(inode);
1979                                 return error;
1980                         }
1981                 }
1982 #ifdef CONFIG_TMPFS_POSIX_ACL
1983                 error = generic_acl_init(inode, dir);
1984                 if (error) {
1985                         iput(inode);
1986                         return error;
1987                 }
1988 #else
1989                 error = 0;
1990 #endif
1991                 d_tmpfile(dentry, inode);
1992         }
1993         return error;
1994 }
1995
1996 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
1997 {
1998         int error;
1999
2000         if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
2001                 return error;
2002         inc_nlink(dir);
2003         return 0;
2004 }
2005
2006 static int shmem_create(struct inode *dir, struct dentry *dentry, umode_t mode,
2007                 bool excl)
2008 {
2009         return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
2010 }
2011
2012 /*
2013  * Link a file..
2014  */
2015 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
2016 {
2017         struct inode *inode = old_dentry->d_inode;
2018         int ret;
2019
2020         /*
2021          * No ordinary (disk based) filesystem counts links as inodes;
2022          * but each new link needs a new dentry, pinning lowmem, and
2023          * tmpfs dentries cannot be pruned until they are unlinked.
2024          */
2025         ret = shmem_reserve_inode(inode->i_sb);
2026         if (ret)
2027                 goto out;
2028
2029         dir->i_size += BOGO_DIRENT_SIZE;
2030         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2031         inc_nlink(inode);
2032         ihold(inode);   /* New dentry reference */
2033         dget(dentry);           /* Extra pinning count for the created dentry */
2034         d_instantiate(dentry, inode);
2035 out:
2036         return ret;
2037 }
2038
2039 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
2040 {
2041         struct inode *inode = dentry->d_inode;
2042
2043         if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
2044                 shmem_free_inode(inode->i_sb);
2045
2046         dir->i_size -= BOGO_DIRENT_SIZE;
2047         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2048         drop_nlink(inode);
2049         dput(dentry);   /* Undo the count from "create" - this does all the work */
2050         return 0;
2051 }
2052
2053 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
2054 {
2055         if (!simple_empty(dentry))
2056                 return -ENOTEMPTY;
2057
2058         drop_nlink(dentry->d_inode);
2059         drop_nlink(dir);
2060         return shmem_unlink(dir, dentry);
2061 }
2062
2063 /*
2064  * The VFS layer already does all the dentry stuff for rename,
2065  * we just have to decrement the usage count for the target if
2066  * it exists so that the VFS layer correctly free's it when it
2067  * gets overwritten.
2068  */
2069 static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
2070 {
2071         struct inode *inode = old_dentry->d_inode;
2072         int they_are_dirs = S_ISDIR(inode->i_mode);
2073
2074         if (!simple_empty(new_dentry))
2075                 return -ENOTEMPTY;
2076
2077         if (new_dentry->d_inode) {
2078                 (void) shmem_unlink(new_dir, new_dentry);
2079                 if (they_are_dirs)
2080                         drop_nlink(old_dir);
2081         } else if (they_are_dirs) {
2082                 drop_nlink(old_dir);
2083                 inc_nlink(new_dir);
2084         }
2085
2086         old_dir->i_size -= BOGO_DIRENT_SIZE;
2087         new_dir->i_size += BOGO_DIRENT_SIZE;
2088         old_dir->i_ctime = old_dir->i_mtime =
2089         new_dir->i_ctime = new_dir->i_mtime =
2090         inode->i_ctime = CURRENT_TIME;
2091         return 0;
2092 }
2093
2094 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
2095 {
2096         int error;
2097         int len;
2098         struct inode *inode;
2099         struct page *page;
2100         char *kaddr;
2101         struct shmem_inode_info *info;
2102
2103         len = strlen(symname) + 1;
2104         if (len > PAGE_CACHE_SIZE)
2105                 return -ENAMETOOLONG;
2106
2107         inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0, VM_NORESERVE);
2108         if (!inode)
2109                 return -ENOSPC;
2110
2111         error = security_inode_init_security(inode, dir, &dentry->d_name,
2112                                              shmem_initxattrs, NULL);
2113         if (error) {
2114                 if (error != -EOPNOTSUPP) {
2115                         iput(inode);
2116                         return error;
2117                 }
2118                 error = 0;
2119         }
2120
2121         info = SHMEM_I(inode);
2122         inode->i_size = len-1;
2123         if (len <= SHORT_SYMLINK_LEN) {
2124                 info->symlink = kmemdup(symname, len, GFP_KERNEL);
2125                 if (!info->symlink) {
2126                         iput(inode);
2127                         return -ENOMEM;
2128                 }
2129                 inode->i_op = &shmem_short_symlink_operations;
2130         } else {
2131                 error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
2132                 if (error) {
2133                         iput(inode);
2134                         return error;
2135                 }
2136                 inode->i_mapping->a_ops = &shmem_aops;
2137                 inode->i_op = &shmem_symlink_inode_operations;
2138                 kaddr = kmap_atomic(page);
2139                 memcpy(kaddr, symname, len);
2140                 kunmap_atomic(kaddr);
2141                 SetPageUptodate(page);
2142                 set_page_dirty(page);
2143                 unlock_page(page);
2144                 page_cache_release(page);
2145         }
2146         dir->i_size += BOGO_DIRENT_SIZE;
2147         dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2148         d_instantiate(dentry, inode);
2149         dget(dentry);
2150         return 0;
2151 }
2152
2153 static void *shmem_follow_short_symlink(struct dentry *dentry, struct nameidata *nd)
2154 {
2155         nd_set_link(nd, SHMEM_I(dentry->d_inode)->symlink);
2156         return NULL;
2157 }
2158
2159 static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
2160 {
2161         struct page *page = NULL;
2162         int error = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
2163         nd_set_link(nd, error ? ERR_PTR(error) : kmap(page));
2164         if (page)
2165                 unlock_page(page);
2166         return page;
2167 }
2168
2169 static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
2170 {
2171         if (!IS_ERR(nd_get_link(nd))) {
2172                 struct page *page = cookie;
2173                 kunmap(page);
2174                 mark_page_accessed(page);
2175                 page_cache_release(page);
2176         }
2177 }
2178
2179 #ifdef CONFIG_TMPFS_XATTR
2180 /*
2181  * Superblocks without xattr inode operations may get some security.* xattr
2182  * support from the LSM "for free". As soon as we have any other xattrs
2183  * like ACLs, we also need to implement the security.* handlers at
2184  * filesystem level, though.
2185  */
2186
2187 /*
2188  * Callback for security_inode_init_security() for acquiring xattrs.
2189  */
2190 static int shmem_initxattrs(struct inode *inode,
2191                             const struct xattr *xattr_array,
2192                             void *fs_info)
2193 {
2194         struct shmem_inode_info *info = SHMEM_I(inode);
2195         const struct xattr *xattr;
2196         struct simple_xattr *new_xattr;
2197         size_t len;
2198
2199         for (xattr = xattr_array; xattr->name != NULL; xattr++) {
2200                 new_xattr = simple_xattr_alloc(xattr->value, xattr->value_len);
2201                 if (!new_xattr)
2202                         return -ENOMEM;
2203
2204                 len = strlen(xattr->name) + 1;
2205                 new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
2206                                           GFP_KERNEL);
2207                 if (!new_xattr->name) {
2208                         kfree(new_xattr);
2209                         return -ENOMEM;
2210                 }
2211
2212                 memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
2213                        XATTR_SECURITY_PREFIX_LEN);
2214                 memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
2215                        xattr->name, len);
2216
2217                 simple_xattr_list_add(&info->xattrs, new_xattr);
2218         }
2219
2220         return 0;
2221 }
2222
2223 static const struct xattr_handler *shmem_xattr_handlers[] = {
2224 #ifdef CONFIG_TMPFS_POSIX_ACL
2225         &generic_acl_access_handler,
2226         &generic_acl_default_handler,
2227 #endif
2228         NULL
2229 };
2230
2231 static int shmem_xattr_validate(const char *name)
2232 {
2233         struct { const char *prefix; size_t len; } arr[] = {
2234                 { XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN },
2235                 { XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN }
2236         };
2237         int i;
2238
2239         for (i = 0; i < ARRAY_SIZE(arr); i++) {
2240                 size_t preflen = arr[i].len;
2241                 if (strncmp(name, arr[i].prefix, preflen) == 0) {
2242                         if (!name[preflen])
2243                                 return -EINVAL;
2244                         return 0;
2245                 }
2246         }
2247         return -EOPNOTSUPP;
2248 }
2249
2250 static ssize_t shmem_getxattr(struct dentry *dentry, const char *name,
2251                               void *buffer, size_t size)
2252 {
2253         struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2254         int err;
2255
2256         /*
2257          * If this is a request for a synthetic attribute in the system.*
2258          * namespace use the generic infrastructure to resolve a handler
2259          * for it via sb->s_xattr.
2260          */
2261         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2262                 return generic_getxattr(dentry, name, buffer, size);
2263
2264         err = shmem_xattr_validate(name);
2265         if (err)
2266                 return err;
2267
2268         return simple_xattr_get(&info->xattrs, name, buffer, size);
2269 }
2270
2271 static int shmem_setxattr(struct dentry *dentry, const char *name,
2272                           const void *value, size_t size, int flags)
2273 {
2274         struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2275         int err;
2276
2277         /*
2278          * If this is a request for a synthetic attribute in the system.*
2279          * namespace use the generic infrastructure to resolve a handler
2280          * for it via sb->s_xattr.
2281          */
2282         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2283                 return generic_setxattr(dentry, name, value, size, flags);
2284
2285         err = shmem_xattr_validate(name);
2286         if (err)
2287                 return err;
2288
2289         return simple_xattr_set(&info->xattrs, name, value, size, flags);
2290 }
2291
2292 static int shmem_removexattr(struct dentry *dentry, const char *name)
2293 {
2294         struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2295         int err;
2296
2297         /*
2298          * If this is a request for a synthetic attribute in the system.*
2299          * namespace use the generic infrastructure to resolve a handler
2300          * for it via sb->s_xattr.
2301          */
2302         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2303                 return generic_removexattr(dentry, name);
2304
2305         err = shmem_xattr_validate(name);
2306         if (err)
2307                 return err;
2308
2309         return simple_xattr_remove(&info->xattrs, name);
2310 }
2311
2312 static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
2313 {
2314         struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2315         return simple_xattr_list(&info->xattrs, buffer, size);
2316 }
2317 #endif /* CONFIG_TMPFS_XATTR */
2318
2319 static const struct inode_operations shmem_short_symlink_operations = {
2320         .readlink       = generic_readlink,
2321         .follow_link    = shmem_follow_short_symlink,
2322 #ifdef CONFIG_TMPFS_XATTR
2323         .setxattr       = shmem_setxattr,
2324         .getxattr       = shmem_getxattr,
2325         .listxattr      = shmem_listxattr,
2326         .removexattr    = shmem_removexattr,
2327 #endif
2328 };
2329
2330 static const struct inode_operations shmem_symlink_inode_operations = {
2331         .readlink       = generic_readlink,
2332         .follow_link    = shmem_follow_link,
2333         .put_link       = shmem_put_link,
2334 #ifdef CONFIG_TMPFS_XATTR
2335         .setxattr       = shmem_setxattr,
2336         .getxattr       = shmem_getxattr,
2337         .listxattr      = shmem_listxattr,
2338         .removexattr    = shmem_removexattr,
2339 #endif
2340 };
2341
2342 static struct dentry *shmem_get_parent(struct dentry *child)
2343 {
2344         return ERR_PTR(-ESTALE);
2345 }
2346
2347 static int shmem_match(struct inode *ino, void *vfh)
2348 {
2349         __u32 *fh = vfh;
2350         __u64 inum = fh[2];
2351         inum = (inum << 32) | fh[1];
2352         return ino->i_ino == inum && fh[0] == ino->i_generation;
2353 }
2354
2355 static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
2356                 struct fid *fid, int fh_len, int fh_type)
2357 {
2358         struct inode *inode;
2359         struct dentry *dentry = NULL;
2360         u64 inum;
2361
2362         if (fh_len < 3)
2363                 return NULL;
2364
2365         inum = fid->raw[2];
2366         inum = (inum << 32) | fid->raw[1];
2367
2368         inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
2369                         shmem_match, fid->raw);
2370         if (inode) {
2371                 dentry = d_find_alias(inode);
2372                 iput(inode);
2373         }
2374
2375         return dentry;
2376 }
2377
2378 static int shmem_encode_fh(struct inode *inode, __u32 *fh, int *len,
2379                                 struct inode *parent)
2380 {
2381         if (*len < 3) {
2382                 *len = 3;
2383                 return FILEID_INVALID;
2384         }
2385
2386         if (inode_unhashed(inode)) {
2387                 /* Unfortunately insert_inode_hash is not idempotent,
2388                  * so as we hash inodes here rather than at creation
2389                  * time, we need a lock to ensure we only try
2390                  * to do it once
2391                  */
2392                 static DEFINE_SPINLOCK(lock);
2393                 spin_lock(&lock);
2394                 if (inode_unhashed(inode))
2395                         __insert_inode_hash(inode,
2396                                             inode->i_ino + inode->i_generation);
2397                 spin_unlock(&lock);
2398         }
2399
2400         fh[0] = inode->i_generation;
2401         fh[1] = inode->i_ino;
2402         fh[2] = ((__u64)inode->i_ino) >> 32;
2403
2404         *len = 3;
2405         return 1;
2406 }
2407
2408 static const struct export_operations shmem_export_ops = {
2409         .get_parent     = shmem_get_parent,
2410         .encode_fh      = shmem_encode_fh,
2411         .fh_to_dentry   = shmem_fh_to_dentry,
2412 };
2413
2414 static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
2415                                bool remount)
2416 {
2417         char *this_char, *value, *rest;
2418         struct mempolicy *mpol = NULL;
2419         uid_t uid;
2420         gid_t gid;
2421
2422         while (options != NULL) {
2423                 this_char = options;
2424                 for (;;) {
2425                         /*
2426                          * NUL-terminate this option: unfortunately,
2427                          * mount options form a comma-separated list,
2428                          * but mpol's nodelist may also contain commas.
2429                          */
2430                         options = strchr(options, ',');
2431                         if (options == NULL)
2432                                 break;
2433                         options++;
2434                         if (!isdigit(*options)) {
2435                                 options[-1] = '\0';
2436                                 break;
2437                         }
2438                 }
2439                 if (!*this_char)
2440                         continue;
2441                 if ((value = strchr(this_char,'=')) != NULL) {
2442                         *value++ = 0;
2443                 } else {
2444                         printk(KERN_ERR
2445                             "tmpfs: No value for mount option '%s'\n",
2446                             this_char);
2447                         goto error;
2448                 }
2449
2450                 if (!strcmp(this_char,"size")) {
2451                         unsigned long long size;
2452                         size = memparse(value,&rest);
2453                         if (*rest == '%') {
2454                                 size <<= PAGE_SHIFT;
2455                                 size *= totalram_pages;
2456                                 do_div(size, 100);
2457                                 rest++;
2458                         }
2459                         if (*rest)
2460                                 goto bad_val;
2461                         sbinfo->max_blocks =
2462                                 DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
2463                 } else if (!strcmp(this_char,"nr_blocks")) {
2464                         sbinfo->max_blocks = memparse(value, &rest);
2465                         if (*rest)
2466                                 goto bad_val;
2467                 } else if (!strcmp(this_char,"nr_inodes")) {
2468                         sbinfo->max_inodes = memparse(value, &rest);
2469                         if (*rest)
2470                                 goto bad_val;
2471                 } else if (!strcmp(this_char,"mode")) {
2472                         if (remount)
2473                                 continue;
2474                         sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
2475                         if (*rest)
2476                                 goto bad_val;
2477                 } else if (!strcmp(this_char,"uid")) {
2478                         if (remount)
2479                                 continue;
2480                         uid = simple_strtoul(value, &rest, 0);
2481                         if (*rest)
2482                                 goto bad_val;
2483                         sbinfo->uid = make_kuid(current_user_ns(), uid);
2484                         if (!uid_valid(sbinfo->uid))
2485                                 goto bad_val;
2486                 } else if (!strcmp(this_char,"gid")) {
2487                         if (remount)
2488                                 continue;
2489                         gid = simple_strtoul(value, &rest, 0);
2490                         if (*rest)
2491                                 goto bad_val;
2492                         sbinfo->gid = make_kgid(current_user_ns(), gid);
2493                         if (!gid_valid(sbinfo->gid))
2494                                 goto bad_val;
2495                 } else if (!strcmp(this_char,"mpol")) {
2496                         mpol_put(mpol);
2497                         mpol = NULL;
2498                         if (mpol_parse_str(value, &mpol))
2499                                 goto bad_val;
2500                 } else {
2501                         printk(KERN_ERR "tmpfs: Bad mount option %s\n",
2502                                this_char);
2503                         goto error;
2504                 }
2505         }
2506         sbinfo->mpol = mpol;
2507         return 0;
2508
2509 bad_val:
2510         printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
2511                value, this_char);
2512 error:
2513         mpol_put(mpol);
2514         return 1;
2515
2516 }
2517
2518 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2519 {
2520         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2521         struct shmem_sb_info config = *sbinfo;
2522         unsigned long inodes;
2523         int error = -EINVAL;
2524
2525         config.mpol = NULL;
2526         if (shmem_parse_options(data, &config, true))
2527                 return error;
2528
2529         spin_lock(&sbinfo->stat_lock);
2530         inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2531         if (percpu_counter_compare(&sbinfo->used_blocks, config.max_blocks) > 0)
2532                 goto out;
2533         if (config.max_inodes < inodes)
2534                 goto out;
2535         /*
2536          * Those tests disallow limited->unlimited while any are in use;
2537          * but we must separately disallow unlimited->limited, because
2538          * in that case we have no record of how much is already in use.
2539          */
2540         if (config.max_blocks && !sbinfo->max_blocks)
2541                 goto out;
2542         if (config.max_inodes && !sbinfo->max_inodes)
2543                 goto out;
2544
2545         error = 0;
2546         sbinfo->max_blocks  = config.max_blocks;
2547         sbinfo->max_inodes  = config.max_inodes;
2548         sbinfo->free_inodes = config.max_inodes - inodes;
2549
2550         /*
2551          * Preserve previous mempolicy unless mpol remount option was specified.
2552          */
2553         if (config.mpol) {
2554                 mpol_put(sbinfo->mpol);
2555                 sbinfo->mpol = config.mpol;     /* transfers initial ref */
2556         }
2557 out:
2558         spin_unlock(&sbinfo->stat_lock);
2559         return error;
2560 }
2561
2562 static int shmem_show_options(struct seq_file *seq, struct dentry *root)
2563 {
2564         struct shmem_sb_info *sbinfo = SHMEM_SB(root->d_sb);
2565
2566         if (sbinfo->max_blocks != shmem_default_max_blocks())
2567                 seq_printf(seq, ",size=%luk",
2568                         sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10));
2569         if (sbinfo->max_inodes != shmem_default_max_inodes())
2570                 seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
2571         if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
2572                 seq_printf(seq, ",mode=%03ho", sbinfo->mode);
2573         if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID))
2574                 seq_printf(seq, ",uid=%u",
2575                                 from_kuid_munged(&init_user_ns, sbinfo->uid));
2576         if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
2577                 seq_printf(seq, ",gid=%u",
2578                                 from_kgid_munged(&init_user_ns, sbinfo->gid));
2579         shmem_show_mpol(seq, sbinfo->mpol);
2580         return 0;
2581 }
2582 #endif /* CONFIG_TMPFS */
2583
2584 static void shmem_put_super(struct super_block *sb)
2585 {
2586         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2587
2588         percpu_counter_destroy(&sbinfo->used_blocks);
2589         mpol_put(sbinfo->mpol);
2590         kfree(sbinfo);
2591         sb->s_fs_info = NULL;
2592 }
2593
2594 int shmem_fill_super(struct super_block *sb, void *data, int silent)
2595 {
2596         struct inode *inode;
2597         struct shmem_sb_info *sbinfo;
2598         int err = -ENOMEM;
2599
2600         /* Round up to L1_CACHE_BYTES to resist false sharing */
2601         sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
2602                                 L1_CACHE_BYTES), GFP_KERNEL);
2603         if (!sbinfo)
2604                 return -ENOMEM;
2605
2606         sbinfo->mode = S_IRWXUGO | S_ISVTX;
2607         sbinfo->uid = current_fsuid();
2608         sbinfo->gid = current_fsgid();
2609         sb->s_fs_info = sbinfo;
2610
2611 #ifdef CONFIG_TMPFS
2612         /*
2613          * Per default we only allow half of the physical ram per
2614          * tmpfs instance, limiting inodes to one per page of lowmem;
2615          * but the internal instance is left unlimited.
2616          */
2617         if (!(sb->s_flags & MS_NOUSER)) {
2618                 sbinfo->max_blocks = shmem_default_max_blocks();
2619                 sbinfo->max_inodes = shmem_default_max_inodes();
2620                 if (shmem_parse_options(data, sbinfo, false)) {
2621                         err = -EINVAL;
2622                         goto failed;
2623                 }
2624         }
2625         sb->s_export_op = &shmem_export_ops;
2626         sb->s_flags |= MS_NOSEC;
2627 #else
2628         sb->s_flags |= MS_NOUSER;
2629 #endif
2630
2631         spin_lock_init(&sbinfo->stat_lock);
2632         if (percpu_counter_init(&sbinfo->used_blocks, 0))
2633                 goto failed;
2634         sbinfo->free_inodes = sbinfo->max_inodes;
2635
2636         sb->s_maxbytes = MAX_LFS_FILESIZE;
2637         sb->s_blocksize = PAGE_CACHE_SIZE;
2638         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
2639         sb->s_magic = TMPFS_MAGIC;
2640         sb->s_op = &shmem_ops;
2641         sb->s_time_gran = 1;
2642 #ifdef CONFIG_TMPFS_XATTR
2643         sb->s_xattr = shmem_xattr_handlers;
2644 #endif
2645 #ifdef CONFIG_TMPFS_POSIX_ACL
2646         sb->s_flags |= MS_POSIXACL;
2647 #endif
2648
2649         inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
2650         if (!inode)
2651                 goto failed;
2652         inode->i_uid = sbinfo->uid;
2653         inode->i_gid = sbinfo->gid;
2654         sb->s_root = d_make_root(inode);
2655         if (!sb->s_root)
2656                 goto failed;
2657         return 0;
2658
2659 failed:
2660         shmem_put_super(sb);
2661         return err;
2662 }
2663
2664 static struct kmem_cache *shmem_inode_cachep;
2665
2666 static struct inode *shmem_alloc_inode(struct super_block *sb)
2667 {
2668         struct shmem_inode_info *info;
2669         info = kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
2670         if (!info)
2671                 return NULL;
2672         return &info->vfs_inode;
2673 }
2674
2675 static void shmem_destroy_callback(struct rcu_head *head)
2676 {
2677         struct inode *inode = container_of(head, struct inode, i_rcu);
2678         kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2679 }
2680
2681 static void shmem_destroy_inode(struct inode *inode)
2682 {
2683         if (S_ISREG(inode->i_mode))
2684                 mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2685         call_rcu(&inode->i_rcu, shmem_destroy_callback);
2686 }
2687
2688 static void shmem_init_inode(void *foo)
2689 {
2690         struct shmem_inode_info *info = foo;
2691         inode_init_once(&info->vfs_inode);
2692 }
2693
2694 static int shmem_init_inodecache(void)
2695 {
2696         shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
2697                                 sizeof(struct shmem_inode_info),
2698                                 0, SLAB_PANIC, shmem_init_inode);
2699         return 0;
2700 }
2701
2702 static void shmem_destroy_inodecache(void)
2703 {
2704         kmem_cache_destroy(shmem_inode_cachep);
2705 }
2706
2707 static const struct address_space_operations shmem_aops = {
2708         .writepage      = shmem_writepage,
2709         .set_page_dirty = __set_page_dirty_no_writeback,
2710 #ifdef CONFIG_TMPFS
2711         .write_begin    = shmem_write_begin,
2712         .write_end      = shmem_write_end,
2713 #endif
2714         .migratepage    = migrate_page,
2715         .error_remove_page = generic_error_remove_page,
2716 };
2717
2718 static const struct file_operations shmem_file_operations = {
2719         .mmap           = shmem_mmap,
2720 #ifdef CONFIG_TMPFS
2721         .llseek         = shmem_file_llseek,
2722         .read           = do_sync_read,
2723         .write          = do_sync_write,
2724         .aio_read       = shmem_file_aio_read,
2725         .aio_write      = generic_file_aio_write,
2726         .fsync          = noop_fsync,
2727         .splice_read    = shmem_file_splice_read,
2728         .splice_write   = generic_file_splice_write,
2729         .fallocate      = shmem_fallocate,
2730 #endif
2731 };
2732
2733 static const struct inode_operations shmem_inode_operations = {
2734         .setattr        = shmem_setattr,
2735 #ifdef CONFIG_TMPFS_XATTR
2736         .setxattr       = shmem_setxattr,
2737         .getxattr       = shmem_getxattr,
2738         .listxattr      = shmem_listxattr,
2739         .removexattr    = shmem_removexattr,
2740 #endif
2741 };
2742
2743 static const struct inode_operations shmem_dir_inode_operations = {
2744 #ifdef CONFIG_TMPFS
2745         .create         = shmem_create,
2746         .lookup         = simple_lookup,
2747         .link           = shmem_link,
2748         .unlink         = shmem_unlink,
2749         .symlink        = shmem_symlink,
2750         .mkdir          = shmem_mkdir,
2751         .rmdir          = shmem_rmdir,
2752         .mknod          = shmem_mknod,
2753         .rename         = shmem_rename,
2754         .tmpfile        = shmem_tmpfile,
2755 #endif
2756 #ifdef CONFIG_TMPFS_XATTR
2757         .setxattr       = shmem_setxattr,
2758         .getxattr       = shmem_getxattr,
2759         .listxattr      = shmem_listxattr,
2760         .removexattr    = shmem_removexattr,
2761 #endif
2762 #ifdef CONFIG_TMPFS_POSIX_ACL
2763         .setattr        = shmem_setattr,
2764 #endif
2765 };
2766
2767 static const struct inode_operations shmem_special_inode_operations = {
2768 #ifdef CONFIG_TMPFS_XATTR
2769         .setxattr       = shmem_setxattr,
2770         .getxattr       = shmem_getxattr,
2771         .listxattr      = shmem_listxattr,
2772         .removexattr    = shmem_removexattr,
2773 #endif
2774 #ifdef CONFIG_TMPFS_POSIX_ACL
2775         .setattr        = shmem_setattr,
2776 #endif
2777 };
2778
2779 static const struct super_operations shmem_ops = {
2780         .alloc_inode    = shmem_alloc_inode,
2781         .destroy_inode  = shmem_destroy_inode,
2782 #ifdef CONFIG_TMPFS
2783         .statfs         = shmem_statfs,
2784         .remount_fs     = shmem_remount_fs,
2785         .show_options   = shmem_show_options,
2786 #endif
2787         .evict_inode    = shmem_evict_inode,
2788         .drop_inode     = generic_delete_inode,
2789         .put_super      = shmem_put_super,
2790 };
2791
2792 static const struct vm_operations_struct shmem_vm_ops = {
2793         .fault          = shmem_fault,
2794 #ifdef CONFIG_NUMA
2795         .set_policy     = shmem_set_policy,
2796         .get_policy     = shmem_get_policy,
2797 #endif
2798         .remap_pages    = generic_file_remap_pages,
2799 };
2800
2801 static struct dentry *shmem_mount(struct file_system_type *fs_type,
2802         int flags, const char *dev_name, void *data)
2803 {
2804         return mount_nodev(fs_type, flags, data, shmem_fill_super);
2805 }
2806
2807 static struct file_system_type shmem_fs_type = {
2808         .owner          = THIS_MODULE,
2809         .name           = "tmpfs",
2810         .mount          = shmem_mount,
2811         .kill_sb        = kill_litter_super,
2812         .fs_flags       = FS_USERNS_MOUNT,
2813 };
2814
2815 int __init shmem_init(void)
2816 {
2817         int error;
2818
2819         error = bdi_init(&shmem_backing_dev_info);
2820         if (error)
2821                 goto out4;
2822
2823         error = shmem_init_inodecache();
2824         if (error)
2825                 goto out3;
2826
2827         error = register_filesystem(&shmem_fs_type);
2828         if (error) {
2829                 printk(KERN_ERR "Could not register tmpfs\n");
2830                 goto out2;
2831         }
2832
2833         shm_mnt = vfs_kern_mount(&shmem_fs_type, MS_NOUSER,
2834                                  shmem_fs_type.name, NULL);
2835         if (IS_ERR(shm_mnt)) {
2836                 error = PTR_ERR(shm_mnt);
2837                 printk(KERN_ERR "Could not kern_mount tmpfs\n");
2838                 goto out1;
2839         }
2840         return 0;
2841
2842 out1:
2843         unregister_filesystem(&shmem_fs_type);
2844 out2:
2845         shmem_destroy_inodecache();
2846 out3:
2847         bdi_destroy(&shmem_backing_dev_info);
2848 out4:
2849         shm_mnt = ERR_PTR(error);
2850         return error;
2851 }
2852
2853 #else /* !CONFIG_SHMEM */
2854
2855 /*
2856  * tiny-shmem: simple shmemfs and tmpfs using ramfs code
2857  *
2858  * This is intended for small system where the benefits of the full
2859  * shmem code (swap-backed and resource-limited) are outweighed by
2860  * their complexity. On systems without swap this code should be
2861  * effectively equivalent, but much lighter weight.
2862  */
2863
2864 static struct file_system_type shmem_fs_type = {
2865         .name           = "tmpfs",
2866         .mount          = ramfs_mount,
2867         .kill_sb        = kill_litter_super,
2868         .fs_flags       = FS_USERNS_MOUNT,
2869 };
2870
2871 int __init shmem_init(void)
2872 {
2873         BUG_ON(register_filesystem(&shmem_fs_type) != 0);
2874
2875         shm_mnt = kern_mount(&shmem_fs_type);
2876         BUG_ON(IS_ERR(shm_mnt));
2877
2878         return 0;
2879 }
2880
2881 int shmem_unuse(swp_entry_t swap, struct page *page)
2882 {
2883         return 0;
2884 }
2885
2886 int shmem_lock(struct file *file, int lock, struct user_struct *user)
2887 {
2888         return 0;
2889 }
2890
2891 void shmem_unlock_mapping(struct address_space *mapping)
2892 {
2893 }
2894
2895 void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
2896 {
2897         truncate_inode_pages_range(inode->i_mapping, lstart, lend);
2898 }
2899 EXPORT_SYMBOL_GPL(shmem_truncate_range);
2900
2901 #define shmem_vm_ops                            generic_file_vm_ops
2902 #define shmem_file_operations                   ramfs_file_operations
2903 #define shmem_get_inode(sb, dir, mode, dev, flags)      ramfs_get_inode(sb, dir, mode, dev)
2904 #define shmem_acct_size(flags, size)            0
2905 #define shmem_unacct_size(flags, size)          do {} while (0)
2906
2907 #endif /* CONFIG_SHMEM */
2908
2909 /* common code */
2910
2911 static char *shmem_dname(struct dentry *dentry, char *buffer, int buflen)
2912 {
2913         return dynamic_dname(dentry, buffer, buflen, "/%s (deleted)",
2914                                 dentry->d_name.name);
2915 }
2916
2917 static struct dentry_operations anon_ops = {
2918         .d_dname = shmem_dname
2919 };
2920
2921 /**
2922  * shmem_file_setup - get an unlinked file living in tmpfs
2923  * @name: name for dentry (to be seen in /proc/<pid>/maps
2924  * @size: size to be set for the file
2925  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
2926  */
2927 struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
2928 {
2929         struct file *res;
2930         struct inode *inode;
2931         struct path path;
2932         struct super_block *sb;
2933         struct qstr this;
2934
2935         if (IS_ERR(shm_mnt))
2936                 return ERR_CAST(shm_mnt);
2937
2938         if (size < 0 || size > MAX_LFS_FILESIZE)
2939                 return ERR_PTR(-EINVAL);
2940
2941         if (shmem_acct_size(flags, size))
2942                 return ERR_PTR(-ENOMEM);
2943
2944         res = ERR_PTR(-ENOMEM);
2945         this.name = name;
2946         this.len = strlen(name);
2947         this.hash = 0; /* will go */
2948         sb = shm_mnt->mnt_sb;
2949         path.dentry = d_alloc_pseudo(sb, &this);
2950         if (!path.dentry)
2951                 goto put_memory;
2952         d_set_d_op(path.dentry, &anon_ops);
2953         path.mnt = mntget(shm_mnt);
2954
2955         res = ERR_PTR(-ENOSPC);
2956         inode = shmem_get_inode(sb, NULL, S_IFREG | S_IRWXUGO, 0, flags);
2957         if (!inode)
2958                 goto put_dentry;
2959
2960         d_instantiate(path.dentry, inode);
2961         inode->i_size = size;
2962         clear_nlink(inode);     /* It is unlinked */
2963         res = ERR_PTR(ramfs_nommu_expand_for_mapping(inode, size));
2964         if (IS_ERR(res))
2965                 goto put_dentry;
2966
2967         res = alloc_file(&path, FMODE_WRITE | FMODE_READ,
2968                   &shmem_file_operations);
2969         if (IS_ERR(res))
2970                 goto put_dentry;
2971
2972         return res;
2973
2974 put_dentry:
2975         path_put(&path);
2976 put_memory:
2977         shmem_unacct_size(flags, size);
2978         return res;
2979 }
2980 EXPORT_SYMBOL_GPL(shmem_file_setup);
2981
2982 /**
2983  * shmem_zero_setup - setup a shared anonymous mapping
2984  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
2985  */
2986 int shmem_zero_setup(struct vm_area_struct *vma)
2987 {
2988         struct file *file;
2989         loff_t size = vma->vm_end - vma->vm_start;
2990
2991         file = shmem_file_setup("dev/zero", size, vma->vm_flags);
2992         if (IS_ERR(file))
2993                 return PTR_ERR(file);
2994
2995         if (vma->vm_file)
2996                 fput(vma->vm_file);
2997         vma->vm_file = file;
2998         vma->vm_ops = &shmem_vm_ops;
2999         return 0;
3000 }
3001
3002 /**
3003  * shmem_read_mapping_page_gfp - read into page cache, using specified page allocation flags.
3004  * @mapping:    the page's address_space
3005  * @index:      the page index
3006  * @gfp:        the page allocator flags to use if allocating
3007  *
3008  * This behaves as a tmpfs "read_cache_page_gfp(mapping, index, gfp)",
3009  * with any new page allocations done using the specified allocation flags.
3010  * But read_cache_page_gfp() uses the ->readpage() method: which does not
3011  * suit tmpfs, since it may have pages in swapcache, and needs to find those
3012  * for itself; although drivers/gpu/drm i915 and ttm rely upon this support.
3013  *
3014  * i915_gem_object_get_pages_gtt() mixes __GFP_NORETRY | __GFP_NOWARN in
3015  * with the mapping_gfp_mask(), to avoid OOMing the machine unnecessarily.
3016  */
3017 struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
3018                                          pgoff_t index, gfp_t gfp)
3019 {
3020 #ifdef CONFIG_SHMEM
3021         struct inode *inode = mapping->host;
3022         struct page *page;
3023         int error;
3024
3025         BUG_ON(mapping->a_ops != &shmem_aops);
3026         error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE, gfp, NULL);
3027         if (error)
3028                 page = ERR_PTR(error);
3029         else
3030                 unlock_page(page);
3031         return page;
3032 #else
3033         /*
3034          * The tiny !SHMEM case uses ramfs without swap
3035          */
3036         return read_cache_page_gfp(mapping, index, gfp);
3037 #endif
3038 }
3039 EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);