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) 2002-2005 Hugh Dickins.
  10  * Copyright (C) 2002-2005 VERITAS Software Corporation.
  11  * Copyright (C) 2004 Andi Kleen, SuSE Labs
  12  *
  13  * Extended attribute support for tmpfs:
  14  * Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@lkcl.net>
  15  * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
  16  *
  17  * This file is released under the GPL.
  18  */
  19
  20 /*
  21  * This virtual memory filesystem is heavily based on the ramfs. It
  22  * extends ramfs by the ability to use swap and honor resource limits
  23  * which makes it a completely usable filesystem.
  24  */
  25
  26 #include <linux/module.h>
  27 #include <linux/init.h>
  28 #include <linux/fs.h>
  29 #include <linux/xattr.h>
  30 #include <linux/exportfs.h>
  31 #include <linux/generic_acl.h>
  32 #include <linux/mm.h>
  33 #include <linux/mman.h>
  34 #include <linux/file.h>
  35 #include <linux/swap.h>
  36 #include <linux/pagemap.h>
  37 #include <linux/string.h>
  38 #include <linux/slab.h>
  39 #include <linux/backing-dev.h>
  40 #include <linux/shmem_fs.h>
  41 #include <linux/mount.h>
  42 #include <linux/writeback.h>
  43 #include <linux/vfs.h>
  44 #include <linux/blkdev.h>
  45 #include <linux/security.h>
  46 #include <linux/swapops.h>
  47 #include <linux/mempolicy.h>
  48 #include <linux/namei.h>
  49 #include <linux/ctype.h>
  50 #include <linux/migrate.h>
  51 #include <linux/highmem.h>
  52 #include <linux/seq_file.h>
  53 #include <linux/magic.h>
  54
  55 #include <asm/uaccess.h>
  56 #include <asm/div64.h>
  57 #include <asm/pgtable.h>
  58
  59 #define ENTRIES_PER_PAGE (PAGE_CACHE_SIZE/sizeof(unsigned long))
  60 #define ENTRIES_PER_PAGEPAGE (ENTRIES_PER_PAGE*ENTRIES_PER_PAGE)
  61 #define BLOCKS_PER_PAGE  (PAGE_CACHE_SIZE/512)
  62
  63 #define SHMEM_MAX_INDEX  (SHMEM_NR_DIRECT + (ENTRIES_PER_PAGEPAGE/2) * (ENTRIES_PER_PAGE+1))
  64 #define SHMEM_MAX_BYTES  ((unsigned long long)SHMEM_MAX_INDEX << PAGE_CACHE_SHIFT)
  65
  66 #define VM_ACCT(size)    (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
  67
  68 /* info->flags needs VM_flags to handle pagein/truncate races efficiently */
  69 #define SHMEM_PAGEIN     VM_READ
  70 #define SHMEM_TRUNCATE   VM_WRITE
  71
  72 /* Definition to limit shmem_truncate's steps between cond_rescheds */
  73 #define LATENCY_LIMIT    64
  74
  75 /* Pretend that each entry is of this size in directory's i_size */
  76 #define BOGO_DIRENT_SIZE 20
  77
  78 /* Flag allocation requirements to shmem_getpage and shmem_swp_alloc */
  79 enum sgp_type {
  80         SGP_READ,       /* don't exceed i_size, don't allocate page */
  81         SGP_CACHE,      /* don't exceed i_size, may allocate page */
  82         SGP_DIRTY,      /* like SGP_CACHE, but set new page dirty */
  83         SGP_WRITE,      /* may exceed i_size, may allocate page */
  84 };
  85
  86 #ifdef CONFIG_TMPFS
  87 static unsigned long shmem_default_max_blocks(void)
  88 {
  89         return totalram_pages / 2;
  90 }
  91
  92 static unsigned long shmem_default_max_inodes(void)
  93 {
  94         return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
  95 }
  96 #endif
  97
  98 static int shmem_getpage(struct inode *inode, unsigned long idx,
  99                          struct page **pagep, enum sgp_type sgp, int *type);
 100
 101 static inline struct page *shmem_dir_alloc(gfp_t gfp_mask)
 102 {
 103         /*
 104          * The above definition of ENTRIES_PER_PAGE, and the use of
 105          * BLOCKS_PER_PAGE on indirect pages, assume PAGE_CACHE_SIZE:
 106          * might be reconsidered if it ever diverges from PAGE_SIZE.
 107          *
 108          * Mobility flags are masked out as swap vectors cannot move
 109          */
 110         return alloc_pages((gfp_mask & ~GFP_MOVABLE_MASK) | __GFP_ZERO,
 111                                 PAGE_CACHE_SHIFT-PAGE_SHIFT);
 112 }
 113
 114 static inline void shmem_dir_free(struct page *page)
 115 {
 116         __free_pages(page, PAGE_CACHE_SHIFT-PAGE_SHIFT);
 117 }
 118
 119 static struct page **shmem_dir_map(struct page *page)
 120 {
 121         return (struct page **)kmap_atomic(page, KM_USER0);
 122 }
 123
 124 static inline void shmem_dir_unmap(struct page **dir)
 125 {
 126         kunmap_atomic(dir, KM_USER0);
 127 }
 128
 129 static swp_entry_t *shmem_swp_map(struct page *page)
 130 {
 131         return (swp_entry_t *)kmap_atomic(page, KM_USER1);
 132 }
 133
 134 static inline void shmem_swp_balance_unmap(void)
 135 {
 136         /*
 137          * When passing a pointer to an i_direct entry, to code which
 138          * also handles indirect entries and so will shmem_swp_unmap,
 139          * we must arrange for the preempt count to remain in balance.
 140          * What kmap_atomic of a lowmem page does depends on config
 141          * and architecture, so pretend to kmap_atomic some lowmem page.
 142          */
 143         (void) kmap_atomic(ZERO_PAGE(0), KM_USER1);
 144 }
 145
 146 static inline void shmem_swp_unmap(swp_entry_t *entry)
 147 {
 148         kunmap_atomic(entry, KM_USER1);
 149 }
 150
 151 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
 152 {
 153         return sb->s_fs_info;
 154 }
 155
 156 /*
 157  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
 158  * for shared memory and for shared anonymous (/dev/zero) mappings
 159  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
 160  * consistent with the pre-accounting of private mappings ...
 161  */
 162 static inline int shmem_acct_size(unsigned long flags, loff_t size)
 163 {
 164         return (flags & VM_ACCOUNT)?
 165                 security_vm_enough_memory(VM_ACCT(size)): 0;
 166 }
 167
 168 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
 169 {
 170         if (flags & VM_ACCOUNT)
 171                 vm_unacct_memory(VM_ACCT(size));
 172 }
 173
 174 /*
 175  * ... whereas tmpfs objects are accounted incrementally as
 176  * pages are allocated, in order to allow huge sparse files.
 177  * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
 178  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
 179  */
 180 static inline int shmem_acct_block(unsigned long flags)
 181 {
 182         return (flags & VM_ACCOUNT)?
 183                 0: security_vm_enough_memory(VM_ACCT(PAGE_CACHE_SIZE));
 184 }
 185
 186 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
 187 {
 188         if (!(flags & VM_ACCOUNT))
 189                 vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
 190 }
 191
 192 static const struct super_operations shmem_ops;
 193 static const struct address_space_operations shmem_aops;
 194 static const struct file_operations shmem_file_operations;
 195 static const struct inode_operations shmem_inode_operations;
 196 static const struct inode_operations shmem_dir_inode_operations;
 197 static const struct inode_operations shmem_special_inode_operations;
 198 static struct vm_operations_struct shmem_vm_ops;
 199
 200 static struct backing_dev_info shmem_backing_dev_info  __read_mostly = {
 201         .ra_pages       = 0,    /* No readahead */
 202         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
 203         .unplug_io_fn   = default_unplug_io_fn,
 204 };
 205
 206 static LIST_HEAD(shmem_swaplist);
 207 static DEFINE_MUTEX(shmem_swaplist_mutex);
 208
 209 static void shmem_free_blocks(struct inode *inode, long pages)
 210 {
 211         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 212         if (sbinfo->max_blocks) {
 213                 spin_lock(&sbinfo->stat_lock);
 214                 sbinfo->free_blocks += pages;
 215                 inode->i_blocks -= pages*BLOCKS_PER_PAGE;
 216                 spin_unlock(&sbinfo->stat_lock);
 217         }
 218 }
 219
 220 static int shmem_reserve_inode(struct super_block *sb)
 221 {
 222         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
 223         if (sbinfo->max_inodes) {
 224                 spin_lock(&sbinfo->stat_lock);
 225                 if (!sbinfo->free_inodes) {
 226                         spin_unlock(&sbinfo->stat_lock);
 227                         return -ENOSPC;
 228                 }
 229                 sbinfo->free_inodes--;
 230                 spin_unlock(&sbinfo->stat_lock);
 231         }
 232         return 0;
 233 }
 234
 235 static void shmem_free_inode(struct super_block *sb)
 236 {
 237         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
 238         if (sbinfo->max_inodes) {
 239                 spin_lock(&sbinfo->stat_lock);
 240                 sbinfo->free_inodes++;
 241                 spin_unlock(&sbinfo->stat_lock);
 242         }
 243 }
 244
 245 /**
 246  * shmem_recalc_inode - recalculate the size of an inode
 247  * @inode: inode to recalc
 248  *
 249  * We have to calculate the free blocks since the mm can drop
 250  * undirtied hole pages behind our back.
 251  *
 252  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
 253  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
 254  *
 255  * It has to be called with the spinlock held.
 256  */
 257 static void shmem_recalc_inode(struct inode *inode)
 258 {
 259         struct shmem_inode_info *info = SHMEM_I(inode);
 260         long freed;
 261
 262         freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
 263         if (freed > 0) {
 264                 info->alloced -= freed;
 265                 shmem_unacct_blocks(info->flags, freed);
 266                 shmem_free_blocks(inode, freed);
 267         }
 268 }
 269
 270 /**
 271  * shmem_swp_entry - find the swap vector position in the info structure
 272  * @info:  info structure for the inode
 273  * @index: index of the page to find
 274  * @page:  optional page to add to the structure. Has to be preset to
 275  *         all zeros
 276  *
 277  * If there is no space allocated yet it will return NULL when
 278  * page is NULL, else it will use the page for the needed block,
 279  * setting it to NULL on return to indicate that it has been used.
 280  *
 281  * The swap vector is organized the following way:
 282  *
 283  * There are SHMEM_NR_DIRECT entries directly stored in the
 284  * shmem_inode_info structure. So small files do not need an addional
 285  * allocation.
 286  *
 287  * For pages with index > SHMEM_NR_DIRECT there is the pointer
 288  * i_indirect which points to a page which holds in the first half
 289  * doubly indirect blocks, in the second half triple indirect blocks:
 290  *
 291  * For an artificial ENTRIES_PER_PAGE = 4 this would lead to the
 292  * following layout (for SHMEM_NR_DIRECT == 16):
 293  *
 294  * i_indirect -> dir --> 16-19
 295  *            |      +-> 20-23
 296  *            |
 297  *            +-->dir2 --> 24-27
 298  *            |        +-> 28-31
 299  *            |        +-> 32-35
 300  *            |        +-> 36-39
 301  *            |
 302  *            +-->dir3 --> 40-43
 303  *                     +-> 44-47
 304  *                     +-> 48-51
 305  *                     +-> 52-55
 306  */
 307 static swp_entry_t *shmem_swp_entry(struct shmem_inode_info *info, unsigned long index, struct page **page)
 308 {
 309         unsigned long offset;
 310         struct page **dir;
 311         struct page *subdir;
 312
 313         if (index < SHMEM_NR_DIRECT) {
 314                 shmem_swp_balance_unmap();
 315                 return info->i_direct+index;
 316         }
 317         if (!info->i_indirect) {
 318                 if (page) {
 319                         info->i_indirect = *page;
 320                         *page = NULL;
 321                 }
 322                 return NULL;                    /* need another page */
 323         }
 324
 325         index -= SHMEM_NR_DIRECT;
 326         offset = index % ENTRIES_PER_PAGE;
 327         index /= ENTRIES_PER_PAGE;
 328         dir = shmem_dir_map(info->i_indirect);
 329
 330         if (index >= ENTRIES_PER_PAGE/2) {
 331                 index -= ENTRIES_PER_PAGE/2;
 332                 dir += ENTRIES_PER_PAGE/2 + index/ENTRIES_PER_PAGE;
 333                 index %= ENTRIES_PER_PAGE;
 334                 subdir = *dir;
 335                 if (!subdir) {
 336                         if (page) {
 337                                 *dir = *page;
 338                                 *page = NULL;
 339                         }
 340                         shmem_dir_unmap(dir);
 341                         return NULL;            /* need another page */
 342                 }
 343                 shmem_dir_unmap(dir);
 344                 dir = shmem_dir_map(subdir);
 345         }
 346
 347         dir += index;
 348         subdir = *dir;
 349         if (!subdir) {
 350                 if (!page || !(subdir = *page)) {
 351                         shmem_dir_unmap(dir);
 352                         return NULL;            /* need a page */
 353                 }
 354                 *dir = subdir;
 355                 *page = NULL;
 356         }
 357         shmem_dir_unmap(dir);
 358         return shmem_swp_map(subdir) + offset;
 359 }
 360
 361 static void shmem_swp_set(struct shmem_inode_info *info, swp_entry_t *entry, unsigned long value)
 362 {
 363         long incdec = value? 1: -1;
 364
 365         entry->val = value;
 366         info->swapped += incdec;
 367         if ((unsigned long)(entry - info->i_direct) >= SHMEM_NR_DIRECT) {
 368                 struct page *page = kmap_atomic_to_page(entry);
 369                 set_page_private(page, page_private(page) + incdec);
 370         }
 371 }
 372
 373 /**
 374  * shmem_swp_alloc - get the position of the swap entry for the page.
 375  * @info:       info structure for the inode
 376  * @index:      index of the page to find
 377  * @sgp:        check and recheck i_size? skip allocation?
 378  *
 379  * If the entry does not exist, allocate it.
 380  */
 381 static swp_entry_t *shmem_swp_alloc(struct shmem_inode_info *info, unsigned long index, enum sgp_type sgp)
 382 {
 383         struct inode *inode = &info->vfs_inode;
 384         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 385         struct page *page = NULL;
 386         swp_entry_t *entry;
 387
 388         if (sgp != SGP_WRITE &&
 389             ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode))
 390                 return ERR_PTR(-EINVAL);
 391
 392         while (!(entry = shmem_swp_entry(info, index, &page))) {
 393                 if (sgp == SGP_READ)
 394                         return shmem_swp_map(ZERO_PAGE(0));
 395                 /*
 396                  * Test free_blocks against 1 not 0, since we have 1 data
 397                  * page (and perhaps indirect index pages) yet to allocate:
 398                  * a waste to allocate index if we cannot allocate data.
 399                  */
 400                 if (sbinfo->max_blocks) {
 401                         spin_lock(&sbinfo->stat_lock);
 402                         if (sbinfo->free_blocks <= 1) {
 403                                 spin_unlock(&sbinfo->stat_lock);
 404                                 return ERR_PTR(-ENOSPC);
 405                         }
 406                         sbinfo->free_blocks--;
 407                         inode->i_blocks += BLOCKS_PER_PAGE;
 408                         spin_unlock(&sbinfo->stat_lock);
 409                 }
 410
 411                 spin_unlock(&info->lock);
 412                 page = shmem_dir_alloc(mapping_gfp_mask(inode->i_mapping));
 413                 if (page)
 414                         set_page_private(page, 0);
 415                 spin_lock(&info->lock);
 416
 417                 if (!page) {
 418                         shmem_free_blocks(inode, 1);
 419                         return ERR_PTR(-ENOMEM);
 420                 }
 421                 if (sgp != SGP_WRITE &&
 422                     ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
 423                         entry = ERR_PTR(-EINVAL);
 424                         break;
 425                 }
 426                 if (info->next_index <= index)
 427                         info->next_index = index + 1;
 428         }
 429         if (page) {
 430                 /* another task gave its page, or truncated the file */
 431                 shmem_free_blocks(inode, 1);
 432                 shmem_dir_free(page);
 433         }
 434         if (info->next_index <= index && !IS_ERR(entry))
 435                 info->next_index = index + 1;
 436         return entry;
 437 }
 438
 439 /**
 440  * shmem_free_swp - free some swap entries in a directory
 441  * @dir:        pointer to the directory
 442  * @edir:       pointer after last entry of the directory
 443  * @punch_lock: pointer to spinlock when needed for the holepunch case
 444  */
 445 static int shmem_free_swp(swp_entry_t *dir, swp_entry_t *edir,
 446                                                 spinlock_t *punch_lock)
 447 {
 448         spinlock_t *punch_unlock = NULL;
 449         swp_entry_t *ptr;
 450         int freed = 0;
 451
 452         for (ptr = dir; ptr < edir; ptr++) {
 453                 if (ptr->val) {
 454                         if (unlikely(punch_lock)) {
 455                                 punch_unlock = punch_lock;
 456                                 punch_lock = NULL;
 457                                 spin_lock(punch_unlock);
 458                                 if (!ptr->val)
 459                                         continue;
 460                         }
 461                         free_swap_and_cache(*ptr);
 462                         *ptr = (swp_entry_t){0};
 463                         freed++;
 464                 }
 465         }
 466         if (punch_unlock)
 467                 spin_unlock(punch_unlock);
 468         return freed;
 469 }
 470
 471 static int shmem_map_and_free_swp(struct page *subdir, int offset,
 472                 int limit, struct page ***dir, spinlock_t *punch_lock)
 473 {
 474         swp_entry_t *ptr;
 475         int freed = 0;
 476
 477         ptr = shmem_swp_map(subdir);
 478         for (; offset < limit; offset += LATENCY_LIMIT) {
 479                 int size = limit - offset;
 480                 if (size > LATENCY_LIMIT)
 481                         size = LATENCY_LIMIT;
 482                 freed += shmem_free_swp(ptr+offset, ptr+offset+size,
 483                                                         punch_lock);
 484                 if (need_resched()) {
 485                         shmem_swp_unmap(ptr);
 486                         if (*dir) {
 487                                 shmem_dir_unmap(*dir);
 488                                 *dir = NULL;
 489                         }
 490                         cond_resched();
 491                         ptr = shmem_swp_map(subdir);
 492                 }
 493         }
 494         shmem_swp_unmap(ptr);
 495         return freed;
 496 }
 497
 498 static void shmem_free_pages(struct list_head *next)
 499 {
 500         struct page *page;
 501         int freed = 0;
 502
 503         do {
 504                 page = container_of(next, struct page, lru);
 505                 next = next->next;
 506                 shmem_dir_free(page);
 507                 freed++;
 508                 if (freed >= LATENCY_LIMIT) {
 509                         cond_resched();
 510                         freed = 0;
 511                 }
 512         } while (next);
 513 }
 514
 515 static void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end)
 516 {
 517         struct shmem_inode_info *info = SHMEM_I(inode);
 518         unsigned long idx;
 519         unsigned long size;
 520         unsigned long limit;
 521         unsigned long stage;
 522         unsigned long diroff;
 523         struct page **dir;
 524         struct page *topdir;
 525         struct page *middir;
 526         struct page *subdir;
 527         swp_entry_t *ptr;
 528         LIST_HEAD(pages_to_free);
 529         long nr_pages_to_free = 0;
 530         long nr_swaps_freed = 0;
 531         int offset;
 532         int freed;
 533         int punch_hole;
 534         spinlock_t *needs_lock;
 535         spinlock_t *punch_lock;
 536         unsigned long upper_limit;
 537
 538         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
 539         idx = (start + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 540         if (idx >= info->next_index)
 541                 return;
 542
 543         spin_lock(&info->lock);
 544         info->flags |= SHMEM_TRUNCATE;
 545         if (likely(end == (loff_t) -1)) {
 546                 limit = info->next_index;
 547                 upper_limit = SHMEM_MAX_INDEX;
 548                 info->next_index = idx;
 549                 needs_lock = NULL;
 550                 punch_hole = 0;
 551         } else {
 552                 if (end + 1 >= inode->i_size) { /* we may free a little more */
 553                         limit = (inode->i_size + PAGE_CACHE_SIZE - 1) >>
 554                                                         PAGE_CACHE_SHIFT;
 555                         upper_limit = SHMEM_MAX_INDEX;
 556                 } else {
 557                         limit = (end + 1) >> PAGE_CACHE_SHIFT;
 558                         upper_limit = limit;
 559                 }
 560                 needs_lock = &info->lock;
 561                 punch_hole = 1;
 562         }
 563
 564         topdir = info->i_indirect;
 565         if (topdir && idx <= SHMEM_NR_DIRECT && !punch_hole) {
 566                 info->i_indirect = NULL;
 567                 nr_pages_to_free++;
 568                 list_add(&topdir->lru, &pages_to_free);
 569         }
 570         spin_unlock(&info->lock);
 571
 572         if (info->swapped && idx < SHMEM_NR_DIRECT) {
 573                 ptr = info->i_direct;
 574                 size = limit;
 575                 if (size > SHMEM_NR_DIRECT)
 576                         size = SHMEM_NR_DIRECT;
 577                 nr_swaps_freed = shmem_free_swp(ptr+idx, ptr+size, needs_lock);
 578         }
 579
 580         /*
 581          * If there are no indirect blocks or we are punching a hole
 582          * below indirect blocks, nothing to be done.
 583          */
 584         if (!topdir || limit <= SHMEM_NR_DIRECT)
 585                 goto done2;
 586
 587         /*
 588          * The truncation case has already dropped info->lock, and we're safe
 589          * because i_size and next_index have already been lowered, preventing
 590          * access beyond.  But in the punch_hole case, we still need to take
 591          * the lock when updating the swap directory, because there might be
 592          * racing accesses by shmem_getpage(SGP_CACHE), shmem_unuse_inode or
 593          * shmem_writepage.  However, whenever we find we can remove a whole
 594          * directory page (not at the misaligned start or end of the range),
 595          * we first NULLify its pointer in the level above, and then have no
 596          * need to take the lock when updating its contents: needs_lock and
 597          * punch_lock (either pointing to info->lock or NULL) manage this.
 598          */
 599
 600         upper_limit -= SHMEM_NR_DIRECT;
 601         limit -= SHMEM_NR_DIRECT;
 602         idx = (idx > SHMEM_NR_DIRECT)? (idx - SHMEM_NR_DIRECT): 0;
 603         offset = idx % ENTRIES_PER_PAGE;
 604         idx -= offset;
 605
 606         dir = shmem_dir_map(topdir);
 607         stage = ENTRIES_PER_PAGEPAGE/2;
 608         if (idx < ENTRIES_PER_PAGEPAGE/2) {
 609                 middir = topdir;
 610                 diroff = idx/ENTRIES_PER_PAGE;
 611         } else {
 612                 dir += ENTRIES_PER_PAGE/2;
 613                 dir += (idx - ENTRIES_PER_PAGEPAGE/2)/ENTRIES_PER_PAGEPAGE;
 614                 while (stage <= idx)
 615                         stage += ENTRIES_PER_PAGEPAGE;
 616                 middir = *dir;
 617                 if (*dir) {
 618                         diroff = ((idx - ENTRIES_PER_PAGEPAGE/2) %
 619                                 ENTRIES_PER_PAGEPAGE) / ENTRIES_PER_PAGE;
 620                         if (!diroff && !offset && upper_limit >= stage) {
 621                                 if (needs_lock) {
 622                                         spin_lock(needs_lock);
 623                                         *dir = NULL;
 624                                         spin_unlock(needs_lock);
 625                                         needs_lock = NULL;
 626                                 } else
 627                                         *dir = NULL;
 628                                 nr_pages_to_free++;
 629                                 list_add(&middir->lru, &pages_to_free);
 630                         }
 631                         shmem_dir_unmap(dir);
 632                         dir = shmem_dir_map(middir);
 633                 } else {
 634                         diroff = 0;
 635                         offset = 0;
 636                         idx = stage;
 637                 }
 638         }
 639
 640         for (; idx < limit; idx += ENTRIES_PER_PAGE, diroff++) {
 641                 if (unlikely(idx == stage)) {
 642                         shmem_dir_unmap(dir);
 643                         dir = shmem_dir_map(topdir) +
 644                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
 645                         while (!*dir) {
 646                                 dir++;
 647                                 idx += ENTRIES_PER_PAGEPAGE;
 648                                 if (idx >= limit)
 649                                         goto done1;
 650                         }
 651                         stage = idx + ENTRIES_PER_PAGEPAGE;
 652                         middir = *dir;
 653                         if (punch_hole)
 654                                 needs_lock = &info->lock;
 655                         if (upper_limit >= stage) {
 656                                 if (needs_lock) {
 657                                         spin_lock(needs_lock);
 658                                         *dir = NULL;
 659                                         spin_unlock(needs_lock);
 660                                         needs_lock = NULL;
 661                                 } else
 662                                         *dir = NULL;
 663                                 nr_pages_to_free++;
 664                                 list_add(&middir->lru, &pages_to_free);
 665                         }
 666                         shmem_dir_unmap(dir);
 667                         cond_resched();
 668                         dir = shmem_dir_map(middir);
 669                         diroff = 0;
 670                 }
 671                 punch_lock = needs_lock;
 672                 subdir = dir[diroff];
 673                 if (subdir && !offset && upper_limit-idx >= ENTRIES_PER_PAGE) {
 674                         if (needs_lock) {
 675                                 spin_lock(needs_lock);
 676                                 dir[diroff] = NULL;
 677                                 spin_unlock(needs_lock);
 678                                 punch_lock = NULL;
 679                         } else
 680                                 dir[diroff] = NULL;
 681                         nr_pages_to_free++;
 682                         list_add(&subdir->lru, &pages_to_free);
 683                 }
 684                 if (subdir && page_private(subdir) /* has swap entries */) {
 685                         size = limit - idx;
 686                         if (size > ENTRIES_PER_PAGE)
 687                                 size = ENTRIES_PER_PAGE;
 688                         freed = shmem_map_and_free_swp(subdir,
 689                                         offset, size, &dir, punch_lock);
 690                         if (!dir)
 691                                 dir = shmem_dir_map(middir);
 692                         nr_swaps_freed += freed;
 693                         if (offset || punch_lock) {
 694                                 spin_lock(&info->lock);
 695                                 set_page_private(subdir,
 696                                         page_private(subdir) - freed);
 697                                 spin_unlock(&info->lock);
 698                         } else
 699                                 BUG_ON(page_private(subdir) != freed);
 700                 }
 701                 offset = 0;
 702         }
 703 done1:
 704         shmem_dir_unmap(dir);
 705 done2:
 706         if (inode->i_mapping->nrpages && (info->flags & SHMEM_PAGEIN)) {
 707                 /*
 708                  * Call truncate_inode_pages again: racing shmem_unuse_inode
 709                  * may have swizzled a page in from swap since vmtruncate or
 710                  * generic_delete_inode did it, before we lowered next_index.
 711                  * Also, though shmem_getpage checks i_size before adding to
 712                  * cache, no recheck after: so fix the narrow window there too.
 713                  *
 714                  * Recalling truncate_inode_pages_range and unmap_mapping_range
 715                  * every time for punch_hole (which never got a chance to clear
 716                  * SHMEM_PAGEIN at the start of vmtruncate_range) is expensive,
 717                  * yet hardly ever necessary: try to optimize them out later.
 718                  */
 719                 truncate_inode_pages_range(inode->i_mapping, start, end);
 720                 if (punch_hole)
 721                         unmap_mapping_range(inode->i_mapping, start,
 722                                                         end - start, 1);
 723         }
 724
 725         spin_lock(&info->lock);
 726         info->flags &= ~SHMEM_TRUNCATE;
 727         info->swapped -= nr_swaps_freed;
 728         if (nr_pages_to_free)
 729                 shmem_free_blocks(inode, nr_pages_to_free);
 730         shmem_recalc_inode(inode);
 731         spin_unlock(&info->lock);
 732
 733         /*
 734          * Empty swap vector directory pages to be freed?
 735          */
 736         if (!list_empty(&pages_to_free)) {
 737                 pages_to_free.prev->next = NULL;
 738                 shmem_free_pages(pages_to_free.next);
 739         }
 740 }
 741
 742 static void shmem_truncate(struct inode *inode)
 743 {
 744         shmem_truncate_range(inode, inode->i_size, (loff_t)-1);
 745 }
 746
 747 static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
 748 {
 749         struct inode *inode = dentry->d_inode;
 750         struct page *page = NULL;
 751         int error;
 752
 753         if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
 754                 if (attr->ia_size < inode->i_size) {
 755                         /*
 756                          * If truncating down to a partial page, then
 757                          * if that page is already allocated, hold it
 758                          * in memory until the truncation is over, so
 759                          * truncate_partial_page cannnot miss it were
 760                          * it assigned to swap.
 761                          */
 762                         if (attr->ia_size & (PAGE_CACHE_SIZE-1)) {
 763                                 (void) shmem_getpage(inode,
 764                                         attr->ia_size>>PAGE_CACHE_SHIFT,
 765                                                 &page, SGP_READ, NULL);
 766                                 if (page)
 767                                         unlock_page(page);
 768                         }
 769                         /*
 770                          * Reset SHMEM_PAGEIN flag so that shmem_truncate can
 771                          * detect if any pages might have been added to cache
 772                          * after truncate_inode_pages.  But we needn't bother
 773                          * if it's being fully truncated to zero-length: the
 774                          * nrpages check is efficient enough in that case.
 775                          */
 776                         if (attr->ia_size) {
 777                                 struct shmem_inode_info *info = SHMEM_I(inode);
 778                                 spin_lock(&info->lock);
 779                                 info->flags &= ~SHMEM_PAGEIN;
 780                                 spin_unlock(&info->lock);
 781                         }
 782                 }
 783         }
 784
 785         error = inode_change_ok(inode, attr);
 786         if (!error)
 787                 error = inode_setattr(inode, attr);
 788 #ifdef CONFIG_TMPFS_POSIX_ACL
 789         if (!error && (attr->ia_valid & ATTR_MODE))
 790                 error = generic_acl_chmod(inode, &shmem_acl_ops);
 791 #endif
 792         if (page)
 793                 page_cache_release(page);
 794         return error;
 795 }
 796
 797 static void shmem_delete_inode(struct inode *inode)
 798 {
 799         struct shmem_inode_info *info = SHMEM_I(inode);
 800
 801         if (inode->i_op->truncate == shmem_truncate) {
 802                 truncate_inode_pages(inode->i_mapping, 0);
 803                 shmem_unacct_size(info->flags, inode->i_size);
 804                 inode->i_size = 0;
 805                 shmem_truncate(inode);
 806                 if (!list_empty(&info->swaplist)) {
 807                         mutex_lock(&shmem_swaplist_mutex);
 808                         list_del_init(&info->swaplist);
 809                         mutex_unlock(&shmem_swaplist_mutex);
 810                 }
 811         }
 812         BUG_ON(inode->i_blocks);
 813         shmem_free_inode(inode->i_sb);
 814         clear_inode(inode);
 815 }
 816
 817 static inline int shmem_find_swp(swp_entry_t entry, swp_entry_t *dir, swp_entry_t *edir)
 818 {
 819         swp_entry_t *ptr;
 820
 821         for (ptr = dir; ptr < edir; ptr++) {
 822                 if (ptr->val == entry.val)
 823                         return ptr - dir;
 824         }
 825         return -1;
 826 }
 827
 828 static int shmem_unuse_inode(struct shmem_inode_info *info, swp_entry_t entry, struct page *page)
 829 {
 830         struct inode *inode;
 831         unsigned long idx;
 832         unsigned long size;
 833         unsigned long limit;
 834         unsigned long stage;
 835         struct page **dir;
 836         struct page *subdir;
 837         swp_entry_t *ptr;
 838         int offset;
 839         int error;
 840
 841         idx = 0;
 842         ptr = info->i_direct;
 843         spin_lock(&info->lock);
 844         if (!info->swapped) {
 845                 list_del_init(&info->swaplist);
 846                 goto lost2;
 847         }
 848         limit = info->next_index;
 849         size = limit;
 850         if (size > SHMEM_NR_DIRECT)
 851                 size = SHMEM_NR_DIRECT;
 852         offset = shmem_find_swp(entry, ptr, ptr+size);
 853         if (offset >= 0)
 854                 goto found;
 855         if (!info->i_indirect)
 856                 goto lost2;
 857
 858         dir = shmem_dir_map(info->i_indirect);
 859         stage = SHMEM_NR_DIRECT + ENTRIES_PER_PAGEPAGE/2;
 860
 861         for (idx = SHMEM_NR_DIRECT; idx < limit; idx += ENTRIES_PER_PAGE, dir++) {
 862                 if (unlikely(idx == stage)) {
 863                         shmem_dir_unmap(dir-1);
 864                         if (cond_resched_lock(&info->lock)) {
 865                                 /* check it has not been truncated */
 866                                 if (limit > info->next_index) {
 867                                         limit = info->next_index;
 868                                         if (idx >= limit)
 869                                                 goto lost2;
 870                                 }
 871                         }
 872                         dir = shmem_dir_map(info->i_indirect) +
 873                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
 874                         while (!*dir) {
 875                                 dir++;
 876                                 idx += ENTRIES_PER_PAGEPAGE;
 877                                 if (idx >= limit)
 878                                         goto lost1;
 879                         }
 880                         stage = idx + ENTRIES_PER_PAGEPAGE;
 881                         subdir = *dir;
 882                         shmem_dir_unmap(dir);
 883                         dir = shmem_dir_map(subdir);
 884                 }
 885                 subdir = *dir;
 886                 if (subdir && page_private(subdir)) {
 887                         ptr = shmem_swp_map(subdir);
 888                         size = limit - idx;
 889                         if (size > ENTRIES_PER_PAGE)
 890                                 size = ENTRIES_PER_PAGE;
 891                         offset = shmem_find_swp(entry, ptr, ptr+size);
 892                         shmem_swp_unmap(ptr);
 893                         if (offset >= 0) {
 894                                 shmem_dir_unmap(dir);
 895                                 goto found;
 896                         }
 897                 }
 898         }
 899 lost1:
 900         shmem_dir_unmap(dir-1);
 901 lost2:
 902         spin_unlock(&info->lock);
 903         return 0;
 904 found:
 905         idx += offset;
 906         inode = igrab(&info->vfs_inode);
 907         spin_unlock(&info->lock);
 908
 909         /*
 910          * Move _head_ to start search for next from here.
 911          * But be careful: shmem_delete_inode checks list_empty without taking
 912          * mutex, and there's an instant in list_move_tail when info->swaplist
 913          * would appear empty, if it were the only one on shmem_swaplist.  We
 914          * could avoid doing it if inode NULL; or use this minor optimization.
 915          */
 916         if (shmem_swaplist.next != &info->swaplist)
 917                 list_move_tail(&shmem_swaplist, &info->swaplist);
 918         mutex_unlock(&shmem_swaplist_mutex);
 919
 920         error = 1;
 921         if (!inode)
 922                 goto out;
 923         /* Precharge page using GFP_KERNEL while we can wait */
 924         error = mem_cgroup_cache_charge(page, current->mm, GFP_KERNEL);
 925         if (error)
 926                 goto out;
 927         error = radix_tree_preload(GFP_KERNEL);
 928         if (error) {
 929                 mem_cgroup_uncharge_cache_page(page);
 930                 goto out;
 931         }
 932         error = 1;
 933
 934         spin_lock(&info->lock);
 935         ptr = shmem_swp_entry(info, idx, NULL);
 936         if (ptr && ptr->val == entry.val) {
 937                 error = add_to_page_cache_locked(page, inode->i_mapping,
 938                                                 idx, GFP_NOWAIT);
 939                 /* does mem_cgroup_uncharge_cache_page on error */
 940         } else  /* we must compensate for our precharge above */
 941                 mem_cgroup_uncharge_cache_page(page);
 942
 943         if (error == -EEXIST) {
 944                 struct page *filepage = find_get_page(inode->i_mapping, idx);
 945                 error = 1;
 946                 if (filepage) {
 947                         /*
 948                          * There might be a more uptodate page coming down
 949                          * from a stacked writepage: forget our swappage if so.
 950                          */
 951                         if (PageUptodate(filepage))
 952                                 error = 0;
 953                         page_cache_release(filepage);
 954                 }
 955         }
 956         if (!error) {
 957                 delete_from_swap_cache(page);
 958                 set_page_dirty(page);
 959                 info->flags |= SHMEM_PAGEIN;
 960                 shmem_swp_set(info, ptr, 0);
 961                 swap_free(entry);
 962                 error = 1;      /* not an error, but entry was found */
 963         }
 964         if (ptr)
 965                 shmem_swp_unmap(ptr);
 966         spin_unlock(&info->lock);
 967         radix_tree_preload_end();
 968 out:
 969         unlock_page(page);
 970         page_cache_release(page);
 971         iput(inode);            /* allows for NULL */
 972         return error;
 973 }
 974
 975 /*
 976  * shmem_unuse() search for an eventually swapped out shmem page.
 977  */
 978 int shmem_unuse(swp_entry_t entry, struct page *page)
 979 {
 980         struct list_head *p, *next;
 981         struct shmem_inode_info *info;
 982         int found = 0;
 983
 984         mutex_lock(&shmem_swaplist_mutex);
 985         list_for_each_safe(p, next, &shmem_swaplist) {
 986                 info = list_entry(p, struct shmem_inode_info, swaplist);
 987                 found = shmem_unuse_inode(info, entry, page);
 988                 cond_resched();
 989                 if (found)
 990                         goto out;
 991         }
 992         mutex_unlock(&shmem_swaplist_mutex);
 993 out:    return found;   /* 0 or 1 or -ENOMEM */
 994 }
 995
 996 /*
 997  * Move the page from the page cache to the swap cache.
 998  */
 999 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
1000 {
1001         struct shmem_inode_info *info;
1002         swp_entry_t *entry, swap;
1003         struct address_space *mapping;
1004         unsigned long index;
1005         struct inode *inode;
1006
1007         BUG_ON(!PageLocked(page));
1008         mapping = page->mapping;
1009         index = page->index;
1010         inode = mapping->host;
1011         info = SHMEM_I(inode);
1012         if (info->flags & VM_LOCKED)
1013                 goto redirty;
1014         if (!total_swap_pages)
1015                 goto redirty;
1016
1017         /*
1018          * shmem_backing_dev_info's capabilities prevent regular writeback or
1019          * sync from ever calling shmem_writepage; but a stacking filesystem
1020          * may use the ->writepage of its underlying filesystem, in which case
1021          * tmpfs should write out to swap only in response to memory pressure,
1022          * and not for pdflush or sync.  However, in those cases, we do still
1023          * want to check if there's a redundant swappage to be discarded.
1024          */
1025         if (wbc->for_reclaim)
1026                 swap = get_swap_page();
1027         else
1028                 swap.val = 0;
1029
1030         spin_lock(&info->lock);
1031         if (index >= info->next_index) {
1032                 BUG_ON(!(info->flags & SHMEM_TRUNCATE));
1033                 goto unlock;
1034         }
1035         entry = shmem_swp_entry(info, index, NULL);
1036         if (entry->val) {
1037                 /*
1038                  * The more uptodate page coming down from a stacked
1039                  * writepage should replace our old swappage.
1040                  */
1041                 free_swap_and_cache(*entry);
1042                 shmem_swp_set(info, entry, 0);
1043         }
1044         shmem_recalc_inode(inode);
1045
1046         if (swap.val && add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
1047                 remove_from_page_cache(page);
1048                 shmem_swp_set(info, entry, swap.val);
1049                 shmem_swp_unmap(entry);
1050                 if (list_empty(&info->swaplist))
1051                         inode = igrab(inode);
1052                 else
1053                         inode = NULL;
1054                 spin_unlock(&info->lock);
1055                 swap_duplicate(swap);
1056                 BUG_ON(page_mapped(page));
1057                 page_cache_release(page);       /* pagecache ref */
1058                 set_page_dirty(page);
1059                 unlock_page(page);
1060                 if (inode) {
1061                         mutex_lock(&shmem_swaplist_mutex);
1062                         /* move instead of add in case we're racing */
1063                         list_move_tail(&info->swaplist, &shmem_swaplist);
1064                         mutex_unlock(&shmem_swaplist_mutex);
1065                         iput(inode);
1066                 }
1067                 return 0;
1068         }
1069
1070         shmem_swp_unmap(entry);
1071 unlock:
1072         spin_unlock(&info->lock);
1073         swap_free(swap);
1074 redirty:
1075         set_page_dirty(page);
1076         if (wbc->for_reclaim)
1077                 return AOP_WRITEPAGE_ACTIVATE;  /* Return with page locked */
1078         unlock_page(page);
1079         return 0;
1080 }
1081
1082 #ifdef CONFIG_NUMA
1083 #ifdef CONFIG_TMPFS
1084 static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
1085 {
1086         char buffer[64];
1087
1088         if (!mpol || mpol->mode == MPOL_DEFAULT)
1089                 return;         /* show nothing */
1090
1091         mpol_to_str(buffer, sizeof(buffer), mpol, 1);
1092
1093         seq_printf(seq, ",mpol=%s", buffer);
1094 }
1095
1096 static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1097 {
1098         struct mempolicy *mpol = NULL;
1099         if (sbinfo->mpol) {
1100                 spin_lock(&sbinfo->stat_lock);  /* prevent replace/use races */
1101                 mpol = sbinfo->mpol;
1102                 mpol_get(mpol);
1103                 spin_unlock(&sbinfo->stat_lock);
1104         }
1105         return mpol;
1106 }
1107 #endif /* CONFIG_TMPFS */
1108
1109 static struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
1110                         struct shmem_inode_info *info, unsigned long idx)
1111 {
1112         struct mempolicy mpol, *spol;
1113         struct vm_area_struct pvma;
1114         struct page *page;
1115
1116         spol = mpol_cond_copy(&mpol,
1117                                 mpol_shared_policy_lookup(&info->policy, idx));
1118
1119         /* Create a pseudo vma that just contains the policy */
1120         pvma.vm_start = 0;
1121         pvma.vm_pgoff = idx;
1122         pvma.vm_ops = NULL;
1123         pvma.vm_policy = spol;
1124         page = swapin_readahead(entry, gfp, &pvma, 0);
1125         return page;
1126 }
1127
1128 static struct page *shmem_alloc_page(gfp_t gfp,
1129                         struct shmem_inode_info *info, unsigned long idx)
1130 {
1131         struct vm_area_struct pvma;
1132
1133         /* Create a pseudo vma that just contains the policy */
1134         pvma.vm_start = 0;
1135         pvma.vm_pgoff = idx;
1136         pvma.vm_ops = NULL;
1137         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx);
1138
1139         /*
1140          * alloc_page_vma() will drop the shared policy reference
1141          */
1142         return alloc_page_vma(gfp, &pvma, 0);
1143 }
1144 #else /* !CONFIG_NUMA */
1145 #ifdef CONFIG_TMPFS
1146 static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *p)
1147 {
1148 }
1149 #endif /* CONFIG_TMPFS */
1150
1151 static inline struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
1152                         struct shmem_inode_info *info, unsigned long idx)
1153 {
1154         return swapin_readahead(entry, gfp, NULL, 0);
1155 }
1156
1157 static inline struct page *shmem_alloc_page(gfp_t gfp,
1158                         struct shmem_inode_info *info, unsigned long idx)
1159 {
1160         return alloc_page(gfp);
1161 }
1162 #endif /* CONFIG_NUMA */
1163
1164 #if !defined(CONFIG_NUMA) || !defined(CONFIG_TMPFS)
1165 static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1166 {
1167         return NULL;
1168 }
1169 #endif
1170
1171 /*
1172  * shmem_getpage - either get the page from swap or allocate a new one
1173  *
1174  * If we allocate a new one we do not mark it dirty. That's up to the
1175  * vm. If we swap it in we mark it dirty since we also free the swap
1176  * entry since a page cannot live in both the swap and page cache
1177  */
1178 static int shmem_getpage(struct inode *inode, unsigned long idx,
1179                         struct page **pagep, enum sgp_type sgp, int *type)
1180 {
1181         struct address_space *mapping = inode->i_mapping;
1182         struct shmem_inode_info *info = SHMEM_I(inode);
1183         struct shmem_sb_info *sbinfo;
1184         struct page *filepage = *pagep;
1185         struct page *swappage;
1186         swp_entry_t *entry;
1187         swp_entry_t swap;
1188         gfp_t gfp;
1189         int error;
1190
1191         if (idx >= SHMEM_MAX_INDEX)
1192                 return -EFBIG;
1193
1194         if (type)
1195                 *type = 0;
1196
1197         /*
1198          * Normally, filepage is NULL on entry, and either found
1199          * uptodate immediately, or allocated and zeroed, or read
1200          * in under swappage, which is then assigned to filepage.
1201          * But shmem_readpage (required for splice) passes in a locked
1202          * filepage, which may be found not uptodate by other callers
1203          * too, and may need to be copied from the swappage read in.
1204          */
1205 repeat:
1206         if (!filepage)
1207                 filepage = find_lock_page(mapping, idx);
1208         if (filepage && PageUptodate(filepage))
1209                 goto done;
1210         error = 0;
1211         gfp = mapping_gfp_mask(mapping);
1212         if (!filepage) {
1213                 /*
1214                  * Try to preload while we can wait, to not make a habit of
1215                  * draining atomic reserves; but don't latch on to this cpu.
1216                  */
1217                 error = radix_tree_preload(gfp & ~__GFP_HIGHMEM);
1218                 if (error)
1219                         goto failed;
1220                 radix_tree_preload_end();
1221         }
1222
1223         spin_lock(&info->lock);
1224         shmem_recalc_inode(inode);
1225         entry = shmem_swp_alloc(info, idx, sgp);
1226         if (IS_ERR(entry)) {
1227                 spin_unlock(&info->lock);
1228                 error = PTR_ERR(entry);
1229                 goto failed;
1230         }
1231         swap = *entry;
1232
1233         if (swap.val) {
1234                 /* Look it up and read it in.. */
1235                 swappage = lookup_swap_cache(swap);
1236                 if (!swappage) {
1237                         shmem_swp_unmap(entry);
1238                         /* here we actually do the io */
1239                         if (type && !(*type & VM_FAULT_MAJOR)) {
1240                                 __count_vm_event(PGMAJFAULT);
1241                                 *type |= VM_FAULT_MAJOR;
1242                         }
1243                         spin_unlock(&info->lock);
1244                         swappage = shmem_swapin(swap, gfp, info, idx);
1245                         if (!swappage) {
1246                                 spin_lock(&info->lock);
1247                                 entry = shmem_swp_alloc(info, idx, sgp);
1248                                 if (IS_ERR(entry))
1249                                         error = PTR_ERR(entry);
1250                                 else {
1251                                         if (entry->val == swap.val)
1252                                                 error = -ENOMEM;
1253                                         shmem_swp_unmap(entry);
1254                                 }
1255                                 spin_unlock(&info->lock);
1256                                 if (error)
1257                                         goto failed;
1258                                 goto repeat;
1259                         }
1260                         wait_on_page_locked(swappage);
1261                         page_cache_release(swappage);
1262                         goto repeat;
1263                 }
1264
1265                 /* We have to do this with page locked to prevent races */
1266                 if (!trylock_page(swappage)) {
1267                         shmem_swp_unmap(entry);
1268                         spin_unlock(&info->lock);
1269                         wait_on_page_locked(swappage);
1270                         page_cache_release(swappage);
1271                         goto repeat;
1272                 }
1273                 if (PageWriteback(swappage)) {
1274                         shmem_swp_unmap(entry);
1275                         spin_unlock(&info->lock);
1276                         wait_on_page_writeback(swappage);
1277                         unlock_page(swappage);
1278                         page_cache_release(swappage);
1279                         goto repeat;
1280                 }
1281                 if (!PageUptodate(swappage)) {
1282                         shmem_swp_unmap(entry);
1283                         spin_unlock(&info->lock);
1284                         unlock_page(swappage);
1285                         page_cache_release(swappage);
1286                         error = -EIO;
1287                         goto failed;
1288                 }
1289
1290                 if (filepage) {
1291                         shmem_swp_set(info, entry, 0);
1292                         shmem_swp_unmap(entry);
1293                         delete_from_swap_cache(swappage);
1294                         spin_unlock(&info->lock);
1295                         copy_highpage(filepage, swappage);
1296                         unlock_page(swappage);
1297                         page_cache_release(swappage);
1298                         flush_dcache_page(filepage);
1299                         SetPageUptodate(filepage);
1300                         set_page_dirty(filepage);
1301                         swap_free(swap);
1302                 } else if (!(error = add_to_page_cache_locked(swappage, mapping,
1303                                         idx, GFP_NOWAIT))) {
1304                         info->flags |= SHMEM_PAGEIN;
1305                         shmem_swp_set(info, entry, 0);
1306                         shmem_swp_unmap(entry);
1307                         delete_from_swap_cache(swappage);
1308                         spin_unlock(&info->lock);
1309                         filepage = swappage;
1310                         set_page_dirty(filepage);
1311                         swap_free(swap);
1312                 } else {
1313                         shmem_swp_unmap(entry);
1314                         spin_unlock(&info->lock);
1315                         unlock_page(swappage);
1316                         page_cache_release(swappage);
1317                         if (error == -ENOMEM) {
1318                                 /* allow reclaim from this memory cgroup */
1319                                 error = mem_cgroup_shrink_usage(current->mm,
1320                                                                 gfp);
1321                                 if (error)
1322                                         goto failed;
1323                         }
1324                         goto repeat;
1325                 }
1326         } else if (sgp == SGP_READ && !filepage) {
1327                 shmem_swp_unmap(entry);
1328                 filepage = find_get_page(mapping, idx);
1329                 if (filepage &&
1330                     (!PageUptodate(filepage) || !trylock_page(filepage))) {
1331                         spin_unlock(&info->lock);
1332                         wait_on_page_locked(filepage);
1333                         page_cache_release(filepage);
1334                         filepage = NULL;
1335                         goto repeat;
1336                 }
1337                 spin_unlock(&info->lock);
1338         } else {
1339                 shmem_swp_unmap(entry);
1340                 sbinfo = SHMEM_SB(inode->i_sb);
1341                 if (sbinfo->max_blocks) {
1342                         spin_lock(&sbinfo->stat_lock);
1343                         if (sbinfo->free_blocks == 0 ||
1344                             shmem_acct_block(info->flags)) {
1345                                 spin_unlock(&sbinfo->stat_lock);
1346                                 spin_unlock(&info->lock);
1347                                 error = -ENOSPC;
1348                                 goto failed;
1349                         }
1350                         sbinfo->free_blocks--;
1351                         inode->i_blocks += BLOCKS_PER_PAGE;
1352                         spin_unlock(&sbinfo->stat_lock);
1353                 } else if (shmem_acct_block(info->flags)) {
1354                         spin_unlock(&info->lock);
1355                         error = -ENOSPC;
1356                         goto failed;
1357                 }
1358
1359                 if (!filepage) {
1360                         int ret;
1361
1362                         spin_unlock(&info->lock);
1363                         filepage = shmem_alloc_page(gfp, info, idx);
1364                         if (!filepage) {
1365                                 shmem_unacct_blocks(info->flags, 1);
1366                                 shmem_free_blocks(inode, 1);
1367                                 error = -ENOMEM;
1368                                 goto failed;
1369                         }
1370                         SetPageSwapBacked(filepage);
1371
1372                         /* Precharge page while we can wait, compensate after */
1373                         error = mem_cgroup_cache_charge(filepage, current->mm,
1374                                                         gfp & ~__GFP_HIGHMEM);
1375                         if (error) {
1376                                 page_cache_release(filepage);
1377                                 shmem_unacct_blocks(info->flags, 1);
1378                                 shmem_free_blocks(inode, 1);
1379                                 filepage = NULL;
1380                                 goto failed;
1381                         }
1382
1383                         spin_lock(&info->lock);
1384                         entry = shmem_swp_alloc(info, idx, sgp);
1385                         if (IS_ERR(entry))
1386                                 error = PTR_ERR(entry);
1387                         else {
1388                                 swap = *entry;
1389                                 shmem_swp_unmap(entry);
1390                         }
1391                         ret = error || swap.val;
1392                         if (ret)
1393                                 mem_cgroup_uncharge_cache_page(filepage);
1394                         else
1395                                 ret = add_to_page_cache_lru(filepage, mapping,
1396                                                 idx, GFP_NOWAIT);
1397                         /*
1398                          * At add_to_page_cache_lru() failure, uncharge will
1399                          * be done automatically.
1400                          */
1401                         if (ret) {
1402                                 spin_unlock(&info->lock);
1403                                 page_cache_release(filepage);
1404                                 shmem_unacct_blocks(info->flags, 1);
1405                                 shmem_free_blocks(inode, 1);
1406                                 filepage = NULL;
1407                                 if (error)
1408                                         goto failed;
1409                                 goto repeat;
1410                         }
1411                         info->flags |= SHMEM_PAGEIN;
1412                 }
1413
1414                 info->alloced++;
1415                 spin_unlock(&info->lock);
1416                 clear_highpage(filepage);
1417                 flush_dcache_page(filepage);
1418                 SetPageUptodate(filepage);
1419                 if (sgp == SGP_DIRTY)
1420                         set_page_dirty(filepage);
1421         }
1422 done:
1423         *pagep = filepage;
1424         return 0;
1425
1426 failed:
1427         if (*pagep != filepage) {
1428                 unlock_page(filepage);
1429                 page_cache_release(filepage);
1430         }
1431         return error;
1432 }
1433
1434 static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1435 {
1436         struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1437         int error;
1438         int ret;
1439
1440         if (((loff_t)vmf->pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
1441                 return VM_FAULT_SIGBUS;
1442
1443         error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret);
1444         if (error)
1445                 return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1446
1447         mark_page_accessed(vmf->page);
1448         return ret | VM_FAULT_LOCKED;
1449 }
1450
1451 #ifdef CONFIG_NUMA
1452 static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *new)
1453 {
1454         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1455         return mpol_set_shared_policy(&SHMEM_I(i)->policy, vma, new);
1456 }
1457
1458 static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
1459                                           unsigned long addr)
1460 {
1461         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1462         unsigned long idx;
1463
1464         idx = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1465         return mpol_shared_policy_lookup(&SHMEM_I(i)->policy, idx);
1466 }
1467 #endif
1468
1469 int shmem_lock(struct file *file, int lock, struct user_struct *user)
1470 {
1471         struct inode *inode = file->f_path.dentry->d_inode;
1472         struct shmem_inode_info *info = SHMEM_I(inode);
1473         int retval = -ENOMEM;
1474
1475         spin_lock(&info->lock);
1476         if (lock && !(info->flags & VM_LOCKED)) {
1477                 if (!user_shm_lock(inode->i_size, user))
1478                         goto out_nomem;
1479                 info->flags |= VM_LOCKED;
1480         }
1481         if (!lock && (info->flags & VM_LOCKED) && user) {
1482                 user_shm_unlock(inode->i_size, user);
1483                 info->flags &= ~VM_LOCKED;
1484         }
1485         retval = 0;
1486 out_nomem:
1487         spin_unlock(&info->lock);
1488         return retval;
1489 }
1490
1491 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1492 {
1493         file_accessed(file);
1494         vma->vm_ops = &shmem_vm_ops;
1495         vma->vm_flags |= VM_CAN_NONLINEAR;
1496         return 0;
1497 }
1498
1499 static struct inode *
1500 shmem_get_inode(struct super_block *sb, int mode, dev_t dev)
1501 {
1502         struct inode *inode;
1503         struct shmem_inode_info *info;
1504         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1505
1506         if (shmem_reserve_inode(sb))
1507                 return NULL;
1508
1509         inode = new_inode(sb);
1510         if (inode) {
1511                 inode->i_mode = mode;
1512                 inode->i_uid = current->fsuid;
1513                 inode->i_gid = current->fsgid;
1514                 inode->i_blocks = 0;
1515                 inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1516                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1517                 inode->i_generation = get_seconds();
1518                 info = SHMEM_I(inode);
1519                 memset(info, 0, (char *)inode - (char *)info);
1520                 spin_lock_init(&info->lock);
1521                 INIT_LIST_HEAD(&info->swaplist);
1522
1523                 switch (mode & S_IFMT) {
1524                 default:
1525                         inode->i_op = &shmem_special_inode_operations;
1526                         init_special_inode(inode, mode, dev);
1527                         break;
1528                 case S_IFREG:
1529                         inode->i_mapping->a_ops = &shmem_aops;
1530                         inode->i_op = &shmem_inode_operations;
1531                         inode->i_fop = &shmem_file_operations;
1532                         mpol_shared_policy_init(&info->policy,
1533                                                  shmem_get_sbmpol(sbinfo));
1534                         break;
1535                 case S_IFDIR:
1536                         inc_nlink(inode);
1537                         /* Some things misbehave if size == 0 on a directory */
1538                         inode->i_size = 2 * BOGO_DIRENT_SIZE;
1539                         inode->i_op = &shmem_dir_inode_operations;
1540                         inode->i_fop = &simple_dir_operations;
1541                         break;
1542                 case S_IFLNK:
1543                         /*
1544                          * Must not load anything in the rbtree,
1545                          * mpol_free_shared_policy will not be called.
1546                          */
1547                         mpol_shared_policy_init(&info->policy, NULL);
1548                         break;
1549                 }
1550         } else
1551                 shmem_free_inode(sb);
1552         return inode;
1553 }
1554
1555 #ifdef CONFIG_TMPFS
1556 static const struct inode_operations shmem_symlink_inode_operations;
1557 static const struct inode_operations shmem_symlink_inline_operations;
1558
1559 /*
1560  * Normally tmpfs avoids the use of shmem_readpage and shmem_write_begin;
1561  * but providing them allows a tmpfs file to be used for splice, sendfile, and
1562  * below the loop driver, in the generic fashion that many filesystems support.
1563  */
1564 static int shmem_readpage(struct file *file, struct page *page)
1565 {
1566         struct inode *inode = page->mapping->host;
1567         int error = shmem_getpage(inode, page->index, &page, SGP_CACHE, NULL);
1568         unlock_page(page);
1569         return error;
1570 }
1571
1572 static int
1573 shmem_write_begin(struct file *file, struct address_space *mapping,
1574                         loff_t pos, unsigned len, unsigned flags,
1575                         struct page **pagep, void **fsdata)
1576 {
1577         struct inode *inode = mapping->host;
1578         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1579         *pagep = NULL;
1580         return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
1581 }
1582
1583 static int
1584 shmem_write_end(struct file *file, struct address_space *mapping,
1585                         loff_t pos, unsigned len, unsigned copied,
1586                         struct page *page, void *fsdata)
1587 {
1588         struct inode *inode = mapping->host;
1589
1590         if (pos + copied > inode->i_size)
1591                 i_size_write(inode, pos + copied);
1592
1593         unlock_page(page);
1594         set_page_dirty(page);
1595         page_cache_release(page);
1596
1597         return copied;
1598 }
1599
1600 static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
1601 {
1602         struct inode *inode = filp->f_path.dentry->d_inode;
1603         struct address_space *mapping = inode->i_mapping;
1604         unsigned long index, offset;
1605         enum sgp_type sgp = SGP_READ;
1606
1607         /*
1608          * Might this read be for a stacking filesystem?  Then when reading
1609          * holes of a sparse file, we actually need to allocate those pages,
1610          * and even mark them dirty, so it cannot exceed the max_blocks limit.
1611          */
1612         if (segment_eq(get_fs(), KERNEL_DS))
1613                 sgp = SGP_DIRTY;
1614
1615         index = *ppos >> PAGE_CACHE_SHIFT;
1616         offset = *ppos & ~PAGE_CACHE_MASK;
1617
1618         for (;;) {
1619                 struct page *page = NULL;
1620                 unsigned long end_index, nr, ret;
1621                 loff_t i_size = i_size_read(inode);
1622
1623                 end_index = i_size >> PAGE_CACHE_SHIFT;
1624                 if (index > end_index)
1625                         break;
1626                 if (index == end_index) {
1627                         nr = i_size & ~PAGE_CACHE_MASK;
1628                         if (nr <= offset)
1629                                 break;
1630                 }
1631
1632                 desc->error = shmem_getpage(inode, index, &page, sgp, NULL);
1633                 if (desc->error) {
1634                         if (desc->error == -EINVAL)
1635                                 desc->error = 0;
1636                         break;
1637                 }
1638                 if (page)
1639                         unlock_page(page);
1640
1641                 /*
1642                  * We must evaluate after, since reads (unlike writes)
1643                  * are called without i_mutex protection against truncate
1644                  */
1645                 nr = PAGE_CACHE_SIZE;
1646                 i_size = i_size_read(inode);
1647                 end_index = i_size >> PAGE_CACHE_SHIFT;
1648                 if (index == end_index) {
1649                         nr = i_size & ~PAGE_CACHE_MASK;
1650                         if (nr <= offset) {
1651                                 if (page)
1652                                         page_cache_release(page);
1653                                 break;
1654                         }
1655                 }
1656                 nr -= offset;
1657
1658                 if (page) {
1659                         /*
1660                          * If users can be writing to this page using arbitrary
1661                          * virtual addresses, take care about potential aliasing
1662                          * before reading the page on the kernel side.
1663                          */
1664                         if (mapping_writably_mapped(mapping))
1665                                 flush_dcache_page(page);
1666                         /*
1667                          * Mark the page accessed if we read the beginning.
1668                          */
1669                         if (!offset)
1670                                 mark_page_accessed(page);
1671                 } else {
1672                         page = ZERO_PAGE(0);
1673                         page_cache_get(page);
1674                 }
1675
1676                 /*
1677                  * Ok, we have the page, and it's up-to-date, so
1678                  * now we can copy it to user space...
1679                  *
1680                  * The actor routine returns how many bytes were actually used..
1681                  * NOTE! This may not be the same as how much of a user buffer
1682                  * we filled up (we may be padding etc), so we can only update
1683                  * "pos" here (the actor routine has to update the user buffer
1684                  * pointers and the remaining count).
1685                  */
1686                 ret = actor(desc, page, offset, nr);
1687                 offset += ret;
1688                 index += offset >> PAGE_CACHE_SHIFT;
1689                 offset &= ~PAGE_CACHE_MASK;
1690
1691                 page_cache_release(page);
1692                 if (ret != nr || !desc->count)
1693                         break;
1694
1695                 cond_resched();
1696         }
1697
1698         *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1699         file_accessed(filp);
1700 }
1701
1702 static ssize_t shmem_file_aio_read(struct kiocb *iocb,
1703                 const struct iovec *iov, unsigned long nr_segs, loff_t pos)
1704 {
1705         struct file *filp = iocb->ki_filp;
1706         ssize_t retval;
1707         unsigned long seg;
1708         size_t count;
1709         loff_t *ppos = &iocb->ki_pos;
1710
1711         retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1712         if (retval)
1713                 return retval;
1714
1715         for (seg = 0; seg < nr_segs; seg++) {
1716                 read_descriptor_t desc;
1717
1718                 desc.written = 0;
1719                 desc.arg.buf = iov[seg].iov_base;
1720                 desc.count = iov[seg].iov_len;
1721                 if (desc.count == 0)
1722                         continue;
1723                 desc.error = 0;
1724                 do_shmem_file_read(filp, ppos, &desc, file_read_actor);
1725                 retval += desc.written;
1726                 if (desc.error) {
1727                         retval = retval ?: desc.error;
1728                         break;
1729                 }
1730                 if (desc.count > 0)
1731                         break;
1732         }
1733         return retval;
1734 }
1735
1736 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
1737 {
1738         struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
1739
1740         buf->f_type = TMPFS_MAGIC;
1741         buf->f_bsize = PAGE_CACHE_SIZE;
1742         buf->f_namelen = NAME_MAX;
1743         spin_lock(&sbinfo->stat_lock);
1744         if (sbinfo->max_blocks) {
1745                 buf->f_blocks = sbinfo->max_blocks;
1746                 buf->f_bavail = buf->f_bfree = sbinfo->free_blocks;
1747         }
1748         if (sbinfo->max_inodes) {
1749                 buf->f_files = sbinfo->max_inodes;
1750                 buf->f_ffree = sbinfo->free_inodes;
1751         }
1752         /* else leave those fields 0 like simple_statfs */
1753         spin_unlock(&sbinfo->stat_lock);
1754         return 0;
1755 }
1756
1757 /*
1758  * File creation. Allocate an inode, and we're done..
1759  */
1760 static int
1761 shmem_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
1762 {
1763         struct inode *inode = shmem_get_inode(dir->i_sb, mode, dev);
1764         int error = -ENOSPC;
1765
1766         if (inode) {
1767                 error = security_inode_init_security(inode, dir, NULL, NULL,
1768                                                      NULL);
1769                 if (error) {
1770                         if (error != -EOPNOTSUPP) {
1771                                 iput(inode);
1772                                 return error;
1773                         }
1774                 }
1775                 error = shmem_acl_init(inode, dir);
1776                 if (error) {
1777                         iput(inode);
1778                         return error;
1779                 }
1780                 if (dir->i_mode & S_ISGID) {
1781                         inode->i_gid = dir->i_gid;
1782                         if (S_ISDIR(mode))
1783                                 inode->i_mode |= S_ISGID;
1784                 }
1785                 dir->i_size += BOGO_DIRENT_SIZE;
1786                 dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1787                 d_instantiate(dentry, inode);
1788                 dget(dentry); /* Extra count - pin the dentry in core */
1789         }
1790         return error;
1791 }
1792
1793 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, int mode)
1794 {
1795         int error;
1796
1797         if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
1798                 return error;
1799         inc_nlink(dir);
1800         return 0;
1801 }
1802
1803 static int shmem_create(struct inode *dir, struct dentry *dentry, int mode,
1804                 struct nameidata *nd)
1805 {
1806         return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
1807 }
1808
1809 /*
1810  * Link a file..
1811  */
1812 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
1813 {
1814         struct inode *inode = old_dentry->d_inode;
1815         int ret;
1816
1817         /*
1818          * No ordinary (disk based) filesystem counts links as inodes;
1819          * but each new link needs a new dentry, pinning lowmem, and
1820          * tmpfs dentries cannot be pruned until they are unlinked.
1821          */
1822         ret = shmem_reserve_inode(inode->i_sb);
1823         if (ret)
1824                 goto out;
1825
1826         dir->i_size += BOGO_DIRENT_SIZE;
1827         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1828         inc_nlink(inode);
1829         atomic_inc(&inode->i_count);    /* New dentry reference */
1830         dget(dentry);           /* Extra pinning count for the created dentry */
1831         d_instantiate(dentry, inode);
1832 out:
1833         return ret;
1834 }
1835
1836 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
1837 {
1838         struct inode *inode = dentry->d_inode;
1839
1840         if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
1841                 shmem_free_inode(inode->i_sb);
1842
1843         dir->i_size -= BOGO_DIRENT_SIZE;
1844         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1845         drop_nlink(inode);
1846         dput(dentry);   /* Undo the count from "create" - this does all the work */
1847         return 0;
1848 }
1849
1850 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
1851 {
1852         if (!simple_empty(dentry))
1853                 return -ENOTEMPTY;
1854
1855         drop_nlink(dentry->d_inode);
1856         drop_nlink(dir);
1857         return shmem_unlink(dir, dentry);
1858 }
1859
1860 /*
1861  * The VFS layer already does all the dentry stuff for rename,
1862  * we just have to decrement the usage count for the target if
1863  * it exists so that the VFS layer correctly free's it when it
1864  * gets overwritten.
1865  */
1866 static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
1867 {
1868         struct inode *inode = old_dentry->d_inode;
1869         int they_are_dirs = S_ISDIR(inode->i_mode);
1870
1871         if (!simple_empty(new_dentry))
1872                 return -ENOTEMPTY;
1873
1874         if (new_dentry->d_inode) {
1875                 (void) shmem_unlink(new_dir, new_dentry);
1876                 if (they_are_dirs)
1877                         drop_nlink(old_dir);
1878         } else if (they_are_dirs) {
1879                 drop_nlink(old_dir);
1880                 inc_nlink(new_dir);
1881         }
1882
1883         old_dir->i_size -= BOGO_DIRENT_SIZE;
1884         new_dir->i_size += BOGO_DIRENT_SIZE;
1885         old_dir->i_ctime = old_dir->i_mtime =
1886         new_dir->i_ctime = new_dir->i_mtime =
1887         inode->i_ctime = CURRENT_TIME;
1888         return 0;
1889 }
1890
1891 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
1892 {
1893         int error;
1894         int len;
1895         struct inode *inode;
1896         struct page *page = NULL;
1897         char *kaddr;
1898         struct shmem_inode_info *info;
1899
1900         len = strlen(symname) + 1;
1901         if (len > PAGE_CACHE_SIZE)
1902                 return -ENAMETOOLONG;
1903
1904         inode = shmem_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0);
1905         if (!inode)
1906                 return -ENOSPC;
1907
1908         error = security_inode_init_security(inode, dir, NULL, NULL,
1909                                              NULL);
1910         if (error) {
1911                 if (error != -EOPNOTSUPP) {
1912                         iput(inode);
1913                         return error;
1914                 }
1915                 error = 0;
1916         }
1917
1918         info = SHMEM_I(inode);
1919         inode->i_size = len-1;
1920         if (len <= (char *)inode - (char *)info) {
1921                 /* do it inline */
1922                 memcpy(info, symname, len);
1923                 inode->i_op = &shmem_symlink_inline_operations;
1924         } else {
1925                 error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
1926                 if (error) {
1927                         iput(inode);
1928                         return error;
1929                 }
1930                 unlock_page(page);
1931                 inode->i_mapping->a_ops = &shmem_aops;
1932                 inode->i_op = &shmem_symlink_inode_operations;
1933                 kaddr = kmap_atomic(page, KM_USER0);
1934                 memcpy(kaddr, symname, len);
1935                 kunmap_atomic(kaddr, KM_USER0);
1936                 set_page_dirty(page);
1937                 page_cache_release(page);
1938         }
1939         if (dir->i_mode & S_ISGID)
1940                 inode->i_gid = dir->i_gid;
1941         dir->i_size += BOGO_DIRENT_SIZE;
1942         dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1943         d_instantiate(dentry, inode);
1944         dget(dentry);
1945         return 0;
1946 }
1947
1948 static void *shmem_follow_link_inline(struct dentry *dentry, struct nameidata *nd)
1949 {
1950         nd_set_link(nd, (char *)SHMEM_I(dentry->d_inode));
1951         return NULL;
1952 }
1953
1954 static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
1955 {
1956         struct page *page = NULL;
1957         int res = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
1958         nd_set_link(nd, res ? ERR_PTR(res) : kmap(page));
1959         if (page)
1960                 unlock_page(page);
1961         return page;
1962 }
1963
1964 static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
1965 {
1966         if (!IS_ERR(nd_get_link(nd))) {
1967                 struct page *page = cookie;
1968                 kunmap(page);
1969                 mark_page_accessed(page);
1970                 page_cache_release(page);
1971         }
1972 }
1973
1974 static const struct inode_operations shmem_symlink_inline_operations = {
1975         .readlink       = generic_readlink,
1976         .follow_link    = shmem_follow_link_inline,
1977 };
1978
1979 static const struct inode_operations shmem_symlink_inode_operations = {
1980         .truncate       = shmem_truncate,
1981         .readlink       = generic_readlink,
1982         .follow_link    = shmem_follow_link,
1983         .put_link       = shmem_put_link,
1984 };
1985
1986 #ifdef CONFIG_TMPFS_POSIX_ACL
1987 /*
1988  * Superblocks without xattr inode operations will get security.* xattr
1989  * support from the VFS "for free". As soon as we have any other xattrs
1990  * like ACLs, we also need to implement the security.* handlers at
1991  * filesystem level, though.
1992  */
1993
1994 static size_t shmem_xattr_security_list(struct inode *inode, char *list,
1995                                         size_t list_len, const char *name,
1996                                         size_t name_len)
1997 {
1998         return security_inode_listsecurity(inode, list, list_len);
1999 }
2000
2001 static int shmem_xattr_security_get(struct inode *inode, const char *name,
2002                                     void *buffer, size_t size)
2003 {
2004         if (strcmp(name, "") == 0)
2005                 return -EINVAL;
2006         return xattr_getsecurity(inode, name, buffer, size);
2007 }
2008
2009 static int shmem_xattr_security_set(struct inode *inode, const char *name,
2010                                     const void *value, size_t size, int flags)
2011 {
2012         if (strcmp(name, "") == 0)
2013                 return -EINVAL;
2014         return security_inode_setsecurity(inode, name, value, size, flags);
2015 }
2016
2017 static struct xattr_handler shmem_xattr_security_handler = {
2018         .prefix = XATTR_SECURITY_PREFIX,
2019         .list   = shmem_xattr_security_list,
2020         .get    = shmem_xattr_security_get,
2021         .set    = shmem_xattr_security_set,
2022 };
2023
2024 static struct xattr_handler *shmem_xattr_handlers[] = {
2025         &shmem_xattr_acl_access_handler,
2026         &shmem_xattr_acl_default_handler,
2027         &shmem_xattr_security_handler,
2028         NULL
2029 };
2030 #endif
2031
2032 static struct dentry *shmem_get_parent(struct dentry *child)
2033 {
2034         return ERR_PTR(-ESTALE);
2035 }
2036
2037 static int shmem_match(struct inode *ino, void *vfh)
2038 {
2039         __u32 *fh = vfh;
2040         __u64 inum = fh[2];
2041         inum = (inum << 32) | fh[1];
2042         return ino->i_ino == inum && fh[0] == ino->i_generation;
2043 }
2044
2045 static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
2046                 struct fid *fid, int fh_len, int fh_type)
2047 {
2048         struct inode *inode;
2049         struct dentry *dentry = NULL;
2050         u64 inum = fid->raw[2];
2051         inum = (inum << 32) | fid->raw[1];
2052
2053         if (fh_len < 3)
2054                 return NULL;
2055
2056         inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
2057                         shmem_match, fid->raw);
2058         if (inode) {
2059                 dentry = d_find_alias(inode);
2060                 iput(inode);
2061         }
2062
2063         return dentry;
2064 }
2065
2066 static int shmem_encode_fh(struct dentry *dentry, __u32 *fh, int *len,
2067                                 int connectable)
2068 {
2069         struct inode *inode = dentry->d_inode;
2070
2071         if (*len < 3)
2072                 return 255;
2073
2074         if (hlist_unhashed(&inode->i_hash)) {
2075                 /* Unfortunately insert_inode_hash is not idempotent,
2076                  * so as we hash inodes here rather than at creation
2077                  * time, we need a lock to ensure we only try
2078                  * to do it once
2079                  */
2080                 static DEFINE_SPINLOCK(lock);
2081                 spin_lock(&lock);
2082                 if (hlist_unhashed(&inode->i_hash))
2083                         __insert_inode_hash(inode,
2084                                             inode->i_ino + inode->i_generation);
2085                 spin_unlock(&lock);
2086         }
2087
2088         fh[0] = inode->i_generation;
2089         fh[1] = inode->i_ino;
2090         fh[2] = ((__u64)inode->i_ino) >> 32;
2091
2092         *len = 3;
2093         return 1;
2094 }
2095
2096 static const struct export_operations shmem_export_ops = {
2097         .get_parent     = shmem_get_parent,
2098         .encode_fh      = shmem_encode_fh,
2099         .fh_to_dentry   = shmem_fh_to_dentry,
2100 };
2101
2102 static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
2103                                bool remount)
2104 {
2105         char *this_char, *value, *rest;
2106
2107         while (options != NULL) {
2108                 this_char = options;
2109                 for (;;) {
2110                         /*
2111                          * NUL-terminate this option: unfortunately,
2112                          * mount options form a comma-separated list,
2113                          * but mpol's nodelist may also contain commas.
2114                          */
2115                         options = strchr(options, ',');
2116                         if (options == NULL)
2117                                 break;
2118                         options++;
2119                         if (!isdigit(*options)) {
2120                                 options[-1] = '\0';
2121                                 break;
2122                         }
2123                 }
2124                 if (!*this_char)
2125                         continue;
2126                 if ((value = strchr(this_char,'=')) != NULL) {
2127                         *value++ = 0;
2128                 } else {
2129                         printk(KERN_ERR
2130                             "tmpfs: No value for mount option '%s'\n",
2131                             this_char);
2132                         return 1;
2133                 }
2134
2135                 if (!strcmp(this_char,"size")) {
2136                         unsigned long long size;
2137                         size = memparse(value,&rest);
2138                         if (*rest == '%') {
2139                                 size <<= PAGE_SHIFT;
2140                                 size *= totalram_pages;
2141                                 do_div(size, 100);
2142                                 rest++;
2143                         }
2144                         if (*rest)
2145                                 goto bad_val;
2146                         sbinfo->max_blocks =
2147                                 DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
2148                 } else if (!strcmp(this_char,"nr_blocks")) {
2149                         sbinfo->max_blocks = memparse(value, &rest);
2150                         if (*rest)
2151                                 goto bad_val;
2152                 } else if (!strcmp(this_char,"nr_inodes")) {
2153                         sbinfo->max_inodes = memparse(value, &rest);
2154                         if (*rest)
2155                                 goto bad_val;
2156                 } else if (!strcmp(this_char,"mode")) {
2157                         if (remount)
2158                                 continue;
2159                         sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
2160                         if (*rest)
2161                                 goto bad_val;
2162                 } else if (!strcmp(this_char,"uid")) {
2163                         if (remount)
2164                                 continue;
2165                         sbinfo->uid = simple_strtoul(value, &rest, 0);
2166                         if (*rest)
2167                                 goto bad_val;
2168                 } else if (!strcmp(this_char,"gid")) {
2169                         if (remount)
2170                                 continue;
2171                         sbinfo->gid = simple_strtoul(value, &rest, 0);
2172                         if (*rest)
2173                                 goto bad_val;
2174                 } else if (!strcmp(this_char,"mpol")) {
2175                         if (mpol_parse_str(value, &sbinfo->mpol, 1))
2176                                 goto bad_val;
2177                 } else {
2178                         printk(KERN_ERR "tmpfs: Bad mount option %s\n",
2179                                this_char);
2180                         return 1;
2181                 }
2182         }
2183         return 0;
2184
2185 bad_val:
2186         printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
2187                value, this_char);
2188         return 1;
2189
2190 }
2191
2192 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2193 {
2194         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2195         struct shmem_sb_info config = *sbinfo;
2196         unsigned long blocks;
2197         unsigned long inodes;
2198         int error = -EINVAL;
2199
2200         if (shmem_parse_options(data, &config, true))
2201                 return error;
2202
2203         spin_lock(&sbinfo->stat_lock);
2204         blocks = sbinfo->max_blocks - sbinfo->free_blocks;
2205         inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2206         if (config.max_blocks < blocks)
2207                 goto out;
2208         if (config.max_inodes < inodes)
2209                 goto out;
2210         /*
2211          * Those tests also disallow limited->unlimited while any are in
2212          * use, so i_blocks will always be zero when max_blocks is zero;
2213          * but we must separately disallow unlimited->limited, because
2214          * in that case we have no record of how much is already in use.
2215          */
2216         if (config.max_blocks && !sbinfo->max_blocks)
2217                 goto out;
2218         if (config.max_inodes && !sbinfo->max_inodes)
2219                 goto out;
2220
2221         error = 0;
2222         sbinfo->max_blocks  = config.max_blocks;
2223         sbinfo->free_blocks = config.max_blocks - blocks;
2224         sbinfo->max_inodes  = config.max_inodes;
2225         sbinfo->free_inodes = config.max_inodes - inodes;
2226
2227         mpol_put(sbinfo->mpol);
2228         sbinfo->mpol        = config.mpol;      /* transfers initial ref */
2229 out:
2230         spin_unlock(&sbinfo->stat_lock);
2231         return error;
2232 }
2233
2234 static int shmem_show_options(struct seq_file *seq, struct vfsmount *vfs)
2235 {
2236         struct shmem_sb_info *sbinfo = SHMEM_SB(vfs->mnt_sb);
2237
2238         if (sbinfo->max_blocks != shmem_default_max_blocks())
2239                 seq_printf(seq, ",size=%luk",
2240                         sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10));
2241         if (sbinfo->max_inodes != shmem_default_max_inodes())
2242                 seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
2243         if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
2244                 seq_printf(seq, ",mode=%03o", sbinfo->mode);
2245         if (sbinfo->uid != 0)
2246                 seq_printf(seq, ",uid=%u", sbinfo->uid);
2247         if (sbinfo->gid != 0)
2248                 seq_printf(seq, ",gid=%u", sbinfo->gid);
2249         shmem_show_mpol(seq, sbinfo->mpol);
2250         return 0;
2251 }
2252 #endif /* CONFIG_TMPFS */
2253
2254 static void shmem_put_super(struct super_block *sb)
2255 {
2256         kfree(sb->s_fs_info);
2257         sb->s_fs_info = NULL;
2258 }
2259
2260 static int shmem_fill_super(struct super_block *sb,
2261                             void *data, int silent)
2262 {
2263         struct inode *inode;
2264         struct dentry *root;
2265         struct shmem_sb_info *sbinfo;
2266         int err = -ENOMEM;
2267
2268         /* Round up to L1_CACHE_BYTES to resist false sharing */
2269         sbinfo = kmalloc(max((int)sizeof(struct shmem_sb_info),
2270                                 L1_CACHE_BYTES), GFP_KERNEL);
2271         if (!sbinfo)
2272                 return -ENOMEM;
2273
2274         sbinfo->max_blocks = 0;
2275         sbinfo->max_inodes = 0;
2276         sbinfo->mode = S_IRWXUGO | S_ISVTX;
2277         sbinfo->uid = current->fsuid;
2278         sbinfo->gid = current->fsgid;
2279         sbinfo->mpol = NULL;
2280         sb->s_fs_info = sbinfo;
2281
2282 #ifdef CONFIG_TMPFS
2283         /*
2284          * Per default we only allow half of the physical ram per
2285          * tmpfs instance, limiting inodes to one per page of lowmem;
2286          * but the internal instance is left unlimited.
2287          */
2288         if (!(sb->s_flags & MS_NOUSER)) {
2289                 sbinfo->max_blocks = shmem_default_max_blocks();
2290                 sbinfo->max_inodes = shmem_default_max_inodes();
2291                 if (shmem_parse_options(data, sbinfo, false)) {
2292                         err = -EINVAL;
2293                         goto failed;
2294                 }
2295         }
2296         sb->s_export_op = &shmem_export_ops;
2297 #else
2298         sb->s_flags |= MS_NOUSER;
2299 #endif
2300
2301         spin_lock_init(&sbinfo->stat_lock);
2302         sbinfo->free_blocks = sbinfo->max_blocks;
2303         sbinfo->free_inodes = sbinfo->max_inodes;
2304
2305         sb->s_maxbytes = SHMEM_MAX_BYTES;
2306         sb->s_blocksize = PAGE_CACHE_SIZE;
2307         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
2308         sb->s_magic = TMPFS_MAGIC;
2309         sb->s_op = &shmem_ops;
2310         sb->s_time_gran = 1;
2311 #ifdef CONFIG_TMPFS_POSIX_ACL
2312         sb->s_xattr = shmem_xattr_handlers;
2313         sb->s_flags |= MS_POSIXACL;
2314 #endif
2315
2316         inode = shmem_get_inode(sb, S_IFDIR | sbinfo->mode, 0);
2317         if (!inode)
2318                 goto failed;
2319         inode->i_uid = sbinfo->uid;
2320         inode->i_gid = sbinfo->gid;
2321         root = d_alloc_root(inode);
2322         if (!root)
2323                 goto failed_iput;
2324         sb->s_root = root;
2325         return 0;
2326
2327 failed_iput:
2328         iput(inode);
2329 failed:
2330         shmem_put_super(sb);
2331         return err;
2332 }
2333
2334 static struct kmem_cache *shmem_inode_cachep;
2335
2336 static struct inode *shmem_alloc_inode(struct super_block *sb)
2337 {
2338         struct shmem_inode_info *p;
2339         p = (struct shmem_inode_info *)kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
2340         if (!p)
2341                 return NULL;
2342         return &p->vfs_inode;
2343 }
2344
2345 static void shmem_destroy_inode(struct inode *inode)
2346 {
2347         if ((inode->i_mode & S_IFMT) == S_IFREG) {
2348                 /* only struct inode is valid if it's an inline symlink */
2349                 mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2350         }
2351         shmem_acl_destroy_inode(inode);
2352         kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2353 }
2354
2355 static void init_once(void *foo)
2356 {
2357         struct shmem_inode_info *p = (struct shmem_inode_info *) foo;
2358
2359         inode_init_once(&p->vfs_inode);
2360 #ifdef CONFIG_TMPFS_POSIX_ACL
2361         p->i_acl = NULL;
2362         p->i_default_acl = NULL;
2363 #endif
2364 }
2365
2366 static int init_inodecache(void)
2367 {
2368         shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
2369                                 sizeof(struct shmem_inode_info),
2370                                 0, SLAB_PANIC, init_once);
2371         return 0;
2372 }
2373
2374 static void destroy_inodecache(void)
2375 {
2376         kmem_cache_destroy(shmem_inode_cachep);
2377 }
2378
2379 static const struct address_space_operations shmem_aops = {
2380         .writepage      = shmem_writepage,
2381         .set_page_dirty = __set_page_dirty_no_writeback,
2382 #ifdef CONFIG_TMPFS
2383         .readpage       = shmem_readpage,
2384         .write_begin    = shmem_write_begin,
2385         .write_end      = shmem_write_end,
2386 #endif
2387         .migratepage    = migrate_page,
2388 };
2389
2390 static const struct file_operations shmem_file_operations = {
2391         .mmap           = shmem_mmap,
2392 #ifdef CONFIG_TMPFS
2393         .llseek         = generic_file_llseek,
2394         .read           = do_sync_read,
2395         .write          = do_sync_write,
2396         .aio_read       = shmem_file_aio_read,
2397         .aio_write      = generic_file_aio_write,
2398         .fsync          = simple_sync_file,
2399         .splice_read    = generic_file_splice_read,
2400         .splice_write   = generic_file_splice_write,
2401 #endif
2402 };
2403
2404 static const struct inode_operations shmem_inode_operations = {
2405         .truncate       = shmem_truncate,
2406         .setattr        = shmem_notify_change,
2407         .truncate_range = shmem_truncate_range,
2408 #ifdef CONFIG_TMPFS_POSIX_ACL
2409         .setxattr       = generic_setxattr,
2410         .getxattr       = generic_getxattr,
2411         .listxattr      = generic_listxattr,
2412         .removexattr    = generic_removexattr,
2413         .permission     = shmem_permission,
2414 #endif
2415
2416 };
2417
2418 static const struct inode_operations shmem_dir_inode_operations = {
2419 #ifdef CONFIG_TMPFS
2420         .create         = shmem_create,
2421         .lookup         = simple_lookup,
2422         .link           = shmem_link,
2423         .unlink         = shmem_unlink,
2424         .symlink        = shmem_symlink,
2425         .mkdir          = shmem_mkdir,
2426         .rmdir          = shmem_rmdir,
2427         .mknod          = shmem_mknod,
2428         .rename         = shmem_rename,
2429 #endif
2430 #ifdef CONFIG_TMPFS_POSIX_ACL
2431         .setattr        = shmem_notify_change,
2432         .setxattr       = generic_setxattr,
2433         .getxattr       = generic_getxattr,
2434         .listxattr      = generic_listxattr,
2435         .removexattr    = generic_removexattr,
2436         .permission     = shmem_permission,
2437 #endif
2438 };
2439
2440 static const struct inode_operations shmem_special_inode_operations = {
2441 #ifdef CONFIG_TMPFS_POSIX_ACL
2442         .setattr        = shmem_notify_change,
2443         .setxattr       = generic_setxattr,
2444         .getxattr       = generic_getxattr,
2445         .listxattr      = generic_listxattr,
2446         .removexattr    = generic_removexattr,
2447         .permission     = shmem_permission,
2448 #endif
2449 };
2450
2451 static const struct super_operations shmem_ops = {
2452         .alloc_inode    = shmem_alloc_inode,
2453         .destroy_inode  = shmem_destroy_inode,
2454 #ifdef CONFIG_TMPFS
2455         .statfs         = shmem_statfs,
2456         .remount_fs     = shmem_remount_fs,
2457         .show_options   = shmem_show_options,
2458 #endif
2459         .delete_inode   = shmem_delete_inode,
2460         .drop_inode     = generic_delete_inode,
2461         .put_super      = shmem_put_super,
2462 };
2463
2464 static struct vm_operations_struct shmem_vm_ops = {
2465         .fault          = shmem_fault,
2466 #ifdef CONFIG_NUMA
2467         .set_policy     = shmem_set_policy,
2468         .get_policy     = shmem_get_policy,
2469 #endif
2470 };
2471
2472
2473 static int shmem_get_sb(struct file_system_type *fs_type,
2474         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
2475 {
2476         return get_sb_nodev(fs_type, flags, data, shmem_fill_super, mnt);
2477 }
2478
2479 static struct file_system_type tmpfs_fs_type = {
2480         .owner          = THIS_MODULE,
2481         .name           = "tmpfs",
2482         .get_sb         = shmem_get_sb,
2483         .kill_sb        = kill_litter_super,
2484 };
2485 static struct vfsmount *shm_mnt;
2486
2487 static int __init init_tmpfs(void)
2488 {
2489         int error;
2490
2491         error = bdi_init(&shmem_backing_dev_info);
2492         if (error)
2493                 goto out4;
2494
2495         error = init_inodecache();
2496         if (error)
2497                 goto out3;
2498
2499         error = register_filesystem(&tmpfs_fs_type);
2500         if (error) {
2501                 printk(KERN_ERR "Could not register tmpfs\n");
2502                 goto out2;
2503         }
2504
2505         shm_mnt = vfs_kern_mount(&tmpfs_fs_type, MS_NOUSER,
2506                                 tmpfs_fs_type.name, NULL);
2507         if (IS_ERR(shm_mnt)) {
2508                 error = PTR_ERR(shm_mnt);
2509                 printk(KERN_ERR "Could not kern_mount tmpfs\n");
2510                 goto out1;
2511         }
2512         return 0;
2513
2514 out1:
2515         unregister_filesystem(&tmpfs_fs_type);
2516 out2:
2517         destroy_inodecache();
2518 out3:
2519         bdi_destroy(&shmem_backing_dev_info);
2520 out4:
2521         shm_mnt = ERR_PTR(error);
2522         return error;
2523 }
2524 module_init(init_tmpfs)
2525
2526 /**
2527  * shmem_file_setup - get an unlinked file living in tmpfs
2528  * @name: name for dentry (to be seen in /proc/<pid>/maps
2529  * @size: size to be set for the file
2530  * @flags: vm_flags
2531  */
2532 struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags)
2533 {
2534         int error;
2535         struct file *file;
2536         struct inode *inode;
2537         struct dentry *dentry, *root;
2538         struct qstr this;
2539
2540         if (IS_ERR(shm_mnt))
2541                 return (void *)shm_mnt;
2542
2543         if (size < 0 || size > SHMEM_MAX_BYTES)
2544                 return ERR_PTR(-EINVAL);
2545
2546         if (shmem_acct_size(flags, size))
2547                 return ERR_PTR(-ENOMEM);
2548
2549         error = -ENOMEM;
2550         this.name = name;
2551         this.len = strlen(name);
2552         this.hash = 0; /* will go */
2553         root = shm_mnt->mnt_root;
2554         dentry = d_alloc(root, &this);
2555         if (!dentry)
2556                 goto put_memory;
2557
2558         error = -ENFILE;
2559         file = get_empty_filp();
2560         if (!file)
2561                 goto put_dentry;
2562
2563         error = -ENOSPC;
2564         inode = shmem_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0);
2565         if (!inode)
2566                 goto close_file;
2567
2568         SHMEM_I(inode)->flags = flags & VM_ACCOUNT;
2569         d_instantiate(dentry, inode);
2570         inode->i_size = size;
2571         inode->i_nlink = 0;     /* It is unlinked */
2572         init_file(file, shm_mnt, dentry, FMODE_WRITE | FMODE_READ,
2573                         &shmem_file_operations);
2574         return file;
2575
2576 close_file:
2577         put_filp(file);
2578 put_dentry:
2579         dput(dentry);
2580 put_memory:
2581         shmem_unacct_size(flags, size);
2582         return ERR_PTR(error);
2583 }
2584 EXPORT_SYMBOL_GPL(shmem_file_setup);
2585
2586 /**
2587  * shmem_zero_setup - setup a shared anonymous mapping
2588  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
2589  */
2590 int shmem_zero_setup(struct vm_area_struct *vma)
2591 {
2592         struct file *file;
2593         loff_t size = vma->vm_end - vma->vm_start;
2594
2595         file = shmem_file_setup("dev/zero", size, vma->vm_flags);
2596         if (IS_ERR(file))
2597                 return PTR_ERR(file);
2598
2599         if (vma->vm_file)
2600                 fput(vma->vm_file);
2601         vma->vm_file = file;
2602         vma->vm_ops = &shmem_vm_ops;
2603         return 0;
2604 }