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/generic_acl.h>
  31 #include <linux/mm.h>
  32 #include <linux/mman.h>
  33 #include <linux/file.h>
  34 #include <linux/swap.h>
  35 #include <linux/pagemap.h>
  36 #include <linux/string.h>
  37 #include <linux/slab.h>
  38 #include <linux/backing-dev.h>
  39 #include <linux/shmem_fs.h>
  40 #include <linux/mount.h>
  41 #include <linux/writeback.h>
  42 #include <linux/vfs.h>
  43 #include <linux/blkdev.h>
  44 #include <linux/security.h>
  45 #include <linux/swapops.h>
  46 #include <linux/mempolicy.h>
  47 #include <linux/namei.h>
  48 #include <linux/ctype.h>
  49 #include <linux/migrate.h>
  50 #include <linux/highmem.h>
  51 #include <linux/backing-dev.h>
  52
  53 #include <asm/uaccess.h>
  54 #include <asm/div64.h>
  55 #include <asm/pgtable.h>
  56
  57 /* This magic number is used in glibc for posix shared memory */
  58 #define TMPFS_MAGIC     0x01021994
  59
  60 #define ENTRIES_PER_PAGE (PAGE_CACHE_SIZE/sizeof(unsigned long))
  61 #define ENTRIES_PER_PAGEPAGE (ENTRIES_PER_PAGE*ENTRIES_PER_PAGE)
  62 #define BLOCKS_PER_PAGE  (PAGE_CACHE_SIZE/512)
  63
  64 #define SHMEM_MAX_INDEX  (SHMEM_NR_DIRECT + (ENTRIES_PER_PAGEPAGE/2) * (ENTRIES_PER_PAGE+1))
  65 #define SHMEM_MAX_BYTES  ((unsigned long long)SHMEM_MAX_INDEX << PAGE_CACHE_SHIFT)
  66
  67 #define VM_ACCT(size)    (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
  68
  69 /* info->flags needs VM_flags to handle pagein/truncate races efficiently */
  70 #define SHMEM_PAGEIN     VM_READ
  71 #define SHMEM_TRUNCATE   VM_WRITE
  72
  73 /* Definition to limit shmem_truncate's steps between cond_rescheds */
  74 #define LATENCY_LIMIT    64
  75
  76 /* Pretend that each entry is of this size in directory's i_size */
  77 #define BOGO_DIRENT_SIZE 20
  78
  79 /* Flag allocation requirements to shmem_getpage and shmem_swp_alloc */
  80 enum sgp_type {
  81         SGP_QUICK,      /* don't try more than file page cache lookup */
  82         SGP_READ,       /* don't exceed i_size, don't allocate page */
  83         SGP_CACHE,      /* don't exceed i_size, may allocate page */
  84         SGP_WRITE,      /* may exceed i_size, may allocate page */
  85 };
  86
  87 static int shmem_getpage(struct inode *inode, unsigned long idx,
  88                          struct page **pagep, enum sgp_type sgp, int *type);
  89
  90 static inline struct page *shmem_dir_alloc(gfp_t gfp_mask)
  91 {
  92         /*
  93          * The above definition of ENTRIES_PER_PAGE, and the use of
  94          * BLOCKS_PER_PAGE on indirect pages, assume PAGE_CACHE_SIZE:
  95          * might be reconsidered if it ever diverges from PAGE_SIZE.
  96          */
  97         return alloc_pages(gfp_mask, PAGE_CACHE_SHIFT-PAGE_SHIFT);
  98 }
  99
 100 static inline void shmem_dir_free(struct page *page)
 101 {
 102         __free_pages(page, PAGE_CACHE_SHIFT-PAGE_SHIFT);
 103 }
 104
 105 static struct page **shmem_dir_map(struct page *page)
 106 {
 107         return (struct page **)kmap_atomic(page, KM_USER0);
 108 }
 109
 110 static inline void shmem_dir_unmap(struct page **dir)
 111 {
 112         kunmap_atomic(dir, KM_USER0);
 113 }
 114
 115 static swp_entry_t *shmem_swp_map(struct page *page)
 116 {
 117         return (swp_entry_t *)kmap_atomic(page, KM_USER1);
 118 }
 119
 120 static inline void shmem_swp_balance_unmap(void)
 121 {
 122         /*
 123          * When passing a pointer to an i_direct entry, to code which
 124          * also handles indirect entries and so will shmem_swp_unmap,
 125          * we must arrange for the preempt count to remain in balance.
 126          * What kmap_atomic of a lowmem page does depends on config
 127          * and architecture, so pretend to kmap_atomic some lowmem page.
 128          */
 129         (void) kmap_atomic(ZERO_PAGE(0), KM_USER1);
 130 }
 131
 132 static inline void shmem_swp_unmap(swp_entry_t *entry)
 133 {
 134         kunmap_atomic(entry, KM_USER1);
 135 }
 136
 137 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
 138 {
 139         return sb->s_fs_info;
 140 }
 141
 142 /*
 143  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
 144  * for shared memory and for shared anonymous (/dev/zero) mappings
 145  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
 146  * consistent with the pre-accounting of private mappings ...
 147  */
 148 static inline int shmem_acct_size(unsigned long flags, loff_t size)
 149 {
 150         return (flags & VM_ACCOUNT)?
 151                 security_vm_enough_memory(VM_ACCT(size)): 0;
 152 }
 153
 154 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
 155 {
 156         if (flags & VM_ACCOUNT)
 157                 vm_unacct_memory(VM_ACCT(size));
 158 }
 159
 160 /*
 161  * ... whereas tmpfs objects are accounted incrementally as
 162  * pages are allocated, in order to allow huge sparse files.
 163  * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
 164  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
 165  */
 166 static inline int shmem_acct_block(unsigned long flags)
 167 {
 168         return (flags & VM_ACCOUNT)?
 169                 0: security_vm_enough_memory(VM_ACCT(PAGE_CACHE_SIZE));
 170 }
 171
 172 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
 173 {
 174         if (!(flags & VM_ACCOUNT))
 175                 vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
 176 }
 177
 178 static const struct super_operations shmem_ops;
 179 static const struct address_space_operations shmem_aops;
 180 static const struct file_operations shmem_file_operations;
 181 static const struct inode_operations shmem_inode_operations;
 182 static const struct inode_operations shmem_dir_inode_operations;
 183 static const struct inode_operations shmem_special_inode_operations;
 184 static struct vm_operations_struct shmem_vm_ops;
 185
 186 static struct backing_dev_info shmem_backing_dev_info  __read_mostly = {
 187         .ra_pages       = 0,    /* No readahead */
 188         .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
 189         .unplug_io_fn   = default_unplug_io_fn,
 190 };
 191
 192 static LIST_HEAD(shmem_swaplist);
 193 static DEFINE_SPINLOCK(shmem_swaplist_lock);
 194
 195 static void shmem_free_blocks(struct inode *inode, long pages)
 196 {
 197         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 198         if (sbinfo->max_blocks) {
 199                 spin_lock(&sbinfo->stat_lock);
 200                 sbinfo->free_blocks += pages;
 201                 inode->i_blocks -= pages*BLOCKS_PER_PAGE;
 202                 spin_unlock(&sbinfo->stat_lock);
 203         }
 204 }
 205
 206 /*
 207  * shmem_recalc_inode - recalculate the size of an inode
 208  *
 209  * @inode: inode to recalc
 210  *
 211  * We have to calculate the free blocks since the mm can drop
 212  * undirtied hole pages behind our back.
 213  *
 214  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
 215  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
 216  *
 217  * It has to be called with the spinlock held.
 218  */
 219 static void shmem_recalc_inode(struct inode *inode)
 220 {
 221         struct shmem_inode_info *info = SHMEM_I(inode);
 222         long freed;
 223
 224         freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
 225         if (freed > 0) {
 226                 info->alloced -= freed;
 227                 shmem_unacct_blocks(info->flags, freed);
 228                 shmem_free_blocks(inode, freed);
 229         }
 230 }
 231
 232 /*
 233  * shmem_swp_entry - find the swap vector position in the info structure
 234  *
 235  * @info:  info structure for the inode
 236  * @index: index of the page to find
 237  * @page:  optional page to add to the structure. Has to be preset to
 238  *         all zeros
 239  *
 240  * If there is no space allocated yet it will return NULL when
 241  * page is NULL, else it will use the page for the needed block,
 242  * setting it to NULL on return to indicate that it has been used.
 243  *
 244  * The swap vector is organized the following way:
 245  *
 246  * There are SHMEM_NR_DIRECT entries directly stored in the
 247  * shmem_inode_info structure. So small files do not need an addional
 248  * allocation.
 249  *
 250  * For pages with index > SHMEM_NR_DIRECT there is the pointer
 251  * i_indirect which points to a page which holds in the first half
 252  * doubly indirect blocks, in the second half triple indirect blocks:
 253  *
 254  * For an artificial ENTRIES_PER_PAGE = 4 this would lead to the
 255  * following layout (for SHMEM_NR_DIRECT == 16):
 256  *
 257  * i_indirect -> dir --> 16-19
 258  *            |      +-> 20-23
 259  *            |
 260  *            +-->dir2 --> 24-27
 261  *            |        +-> 28-31
 262  *            |        +-> 32-35
 263  *            |        +-> 36-39
 264  *            |
 265  *            +-->dir3 --> 40-43
 266  *                     +-> 44-47
 267  *                     +-> 48-51
 268  *                     +-> 52-55
 269  */
 270 static swp_entry_t *shmem_swp_entry(struct shmem_inode_info *info, unsigned long index, struct page **page)
 271 {
 272         unsigned long offset;
 273         struct page **dir;
 274         struct page *subdir;
 275
 276         if (index < SHMEM_NR_DIRECT) {
 277                 shmem_swp_balance_unmap();
 278                 return info->i_direct+index;
 279         }
 280         if (!info->i_indirect) {
 281                 if (page) {
 282                         info->i_indirect = *page;
 283                         *page = NULL;
 284                 }
 285                 return NULL;                    /* need another page */
 286         }
 287
 288         index -= SHMEM_NR_DIRECT;
 289         offset = index % ENTRIES_PER_PAGE;
 290         index /= ENTRIES_PER_PAGE;
 291         dir = shmem_dir_map(info->i_indirect);
 292
 293         if (index >= ENTRIES_PER_PAGE/2) {
 294                 index -= ENTRIES_PER_PAGE/2;
 295                 dir += ENTRIES_PER_PAGE/2 + index/ENTRIES_PER_PAGE;
 296                 index %= ENTRIES_PER_PAGE;
 297                 subdir = *dir;
 298                 if (!subdir) {
 299                         if (page) {
 300                                 *dir = *page;
 301                                 *page = NULL;
 302                         }
 303                         shmem_dir_unmap(dir);
 304                         return NULL;            /* need another page */
 305                 }
 306                 shmem_dir_unmap(dir);
 307                 dir = shmem_dir_map(subdir);
 308         }
 309
 310         dir += index;
 311         subdir = *dir;
 312         if (!subdir) {
 313                 if (!page || !(subdir = *page)) {
 314                         shmem_dir_unmap(dir);
 315                         return NULL;            /* need a page */
 316                 }
 317                 *dir = subdir;
 318                 *page = NULL;
 319         }
 320         shmem_dir_unmap(dir);
 321         return shmem_swp_map(subdir) + offset;
 322 }
 323
 324 static void shmem_swp_set(struct shmem_inode_info *info, swp_entry_t *entry, unsigned long value)
 325 {
 326         long incdec = value? 1: -1;
 327
 328         entry->val = value;
 329         info->swapped += incdec;
 330         if ((unsigned long)(entry - info->i_direct) >= SHMEM_NR_DIRECT) {
 331                 struct page *page = kmap_atomic_to_page(entry);
 332                 set_page_private(page, page_private(page) + incdec);
 333         }
 334 }
 335
 336 /*
 337  * shmem_swp_alloc - get the position of the swap entry for the page.
 338  *                   If it does not exist allocate the entry.
 339  *
 340  * @info:       info structure for the inode
 341  * @index:      index of the page to find
 342  * @sgp:        check and recheck i_size? skip allocation?
 343  */
 344 static swp_entry_t *shmem_swp_alloc(struct shmem_inode_info *info, unsigned long index, enum sgp_type sgp)
 345 {
 346         struct inode *inode = &info->vfs_inode;
 347         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 348         struct page *page = NULL;
 349         swp_entry_t *entry;
 350
 351         if (sgp != SGP_WRITE &&
 352             ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode))
 353                 return ERR_PTR(-EINVAL);
 354
 355         while (!(entry = shmem_swp_entry(info, index, &page))) {
 356                 if (sgp == SGP_READ)
 357                         return shmem_swp_map(ZERO_PAGE(0));
 358                 /*
 359                  * Test free_blocks against 1 not 0, since we have 1 data
 360                  * page (and perhaps indirect index pages) yet to allocate:
 361                  * a waste to allocate index if we cannot allocate data.
 362                  */
 363                 if (sbinfo->max_blocks) {
 364                         spin_lock(&sbinfo->stat_lock);
 365                         if (sbinfo->free_blocks <= 1) {
 366                                 spin_unlock(&sbinfo->stat_lock);
 367                                 return ERR_PTR(-ENOSPC);
 368                         }
 369                         sbinfo->free_blocks--;
 370                         inode->i_blocks += BLOCKS_PER_PAGE;
 371                         spin_unlock(&sbinfo->stat_lock);
 372                 }
 373
 374                 spin_unlock(&info->lock);
 375                 page = shmem_dir_alloc(mapping_gfp_mask(inode->i_mapping) | __GFP_ZERO);
 376                 if (page)
 377                         set_page_private(page, 0);
 378                 spin_lock(&info->lock);
 379
 380                 if (!page) {
 381                         shmem_free_blocks(inode, 1);
 382                         return ERR_PTR(-ENOMEM);
 383                 }
 384                 if (sgp != SGP_WRITE &&
 385                     ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
 386                         entry = ERR_PTR(-EINVAL);
 387                         break;
 388                 }
 389                 if (info->next_index <= index)
 390                         info->next_index = index + 1;
 391         }
 392         if (page) {
 393                 /* another task gave its page, or truncated the file */
 394                 shmem_free_blocks(inode, 1);
 395                 shmem_dir_free(page);
 396         }
 397         if (info->next_index <= index && !IS_ERR(entry))
 398                 info->next_index = index + 1;
 399         return entry;
 400 }
 401
 402 /*
 403  * shmem_free_swp - free some swap entries in a directory
 404  *
 405  * @dir:        pointer to the directory
 406  * @edir:       pointer after last entry of the directory
 407  * @punch_lock: pointer to spinlock when needed for the holepunch case
 408  */
 409 static int shmem_free_swp(swp_entry_t *dir, swp_entry_t *edir,
 410                                                 spinlock_t *punch_lock)
 411 {
 412         spinlock_t *punch_unlock = NULL;
 413         swp_entry_t *ptr;
 414         int freed = 0;
 415
 416         for (ptr = dir; ptr < edir; ptr++) {
 417                 if (ptr->val) {
 418                         if (unlikely(punch_lock)) {
 419                                 punch_unlock = punch_lock;
 420                                 punch_lock = NULL;
 421                                 spin_lock(punch_unlock);
 422                                 if (!ptr->val)
 423                                         continue;
 424                         }
 425                         free_swap_and_cache(*ptr);
 426                         *ptr = (swp_entry_t){0};
 427                         freed++;
 428                 }
 429         }
 430         if (punch_unlock)
 431                 spin_unlock(punch_unlock);
 432         return freed;
 433 }
 434
 435 static int shmem_map_and_free_swp(struct page *subdir, int offset,
 436                 int limit, struct page ***dir, spinlock_t *punch_lock)
 437 {
 438         swp_entry_t *ptr;
 439         int freed = 0;
 440
 441         ptr = shmem_swp_map(subdir);
 442         for (; offset < limit; offset += LATENCY_LIMIT) {
 443                 int size = limit - offset;
 444                 if (size > LATENCY_LIMIT)
 445                         size = LATENCY_LIMIT;
 446                 freed += shmem_free_swp(ptr+offset, ptr+offset+size,
 447                                                         punch_lock);
 448                 if (need_resched()) {
 449                         shmem_swp_unmap(ptr);
 450                         if (*dir) {
 451                                 shmem_dir_unmap(*dir);
 452                                 *dir = NULL;
 453                         }
 454                         cond_resched();
 455                         ptr = shmem_swp_map(subdir);
 456                 }
 457         }
 458         shmem_swp_unmap(ptr);
 459         return freed;
 460 }
 461
 462 static void shmem_free_pages(struct list_head *next)
 463 {
 464         struct page *page;
 465         int freed = 0;
 466
 467         do {
 468                 page = container_of(next, struct page, lru);
 469                 next = next->next;
 470                 shmem_dir_free(page);
 471                 freed++;
 472                 if (freed >= LATENCY_LIMIT) {
 473                         cond_resched();
 474                         freed = 0;
 475                 }
 476         } while (next);
 477 }
 478
 479 static void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end)
 480 {
 481         struct shmem_inode_info *info = SHMEM_I(inode);
 482         unsigned long idx;
 483         unsigned long size;
 484         unsigned long limit;
 485         unsigned long stage;
 486         unsigned long diroff;
 487         struct page **dir;
 488         struct page *topdir;
 489         struct page *middir;
 490         struct page *subdir;
 491         swp_entry_t *ptr;
 492         LIST_HEAD(pages_to_free);
 493         long nr_pages_to_free = 0;
 494         long nr_swaps_freed = 0;
 495         int offset;
 496         int freed;
 497         int punch_hole;
 498         spinlock_t *needs_lock;
 499         spinlock_t *punch_lock;
 500         unsigned long upper_limit;
 501
 502         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
 503         idx = (start + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 504         if (idx >= info->next_index)
 505                 return;
 506
 507         spin_lock(&info->lock);
 508         info->flags |= SHMEM_TRUNCATE;
 509         if (likely(end == (loff_t) -1)) {
 510                 limit = info->next_index;
 511                 upper_limit = SHMEM_MAX_INDEX;
 512                 info->next_index = idx;
 513                 needs_lock = NULL;
 514                 punch_hole = 0;
 515         } else {
 516                 if (end + 1 >= inode->i_size) { /* we may free a little more */
 517                         limit = (inode->i_size + PAGE_CACHE_SIZE - 1) >>
 518                                                         PAGE_CACHE_SHIFT;
 519                         upper_limit = SHMEM_MAX_INDEX;
 520                 } else {
 521                         limit = (end + 1) >> PAGE_CACHE_SHIFT;
 522                         upper_limit = limit;
 523                 }
 524                 needs_lock = &info->lock;
 525                 punch_hole = 1;
 526         }
 527
 528         topdir = info->i_indirect;
 529         if (topdir && idx <= SHMEM_NR_DIRECT && !punch_hole) {
 530                 info->i_indirect = NULL;
 531                 nr_pages_to_free++;
 532                 list_add(&topdir->lru, &pages_to_free);
 533         }
 534         spin_unlock(&info->lock);
 535
 536         if (info->swapped && idx < SHMEM_NR_DIRECT) {
 537                 ptr = info->i_direct;
 538                 size = limit;
 539                 if (size > SHMEM_NR_DIRECT)
 540                         size = SHMEM_NR_DIRECT;
 541                 nr_swaps_freed = shmem_free_swp(ptr+idx, ptr+size, needs_lock);
 542         }
 543
 544         /*
 545          * If there are no indirect blocks or we are punching a hole
 546          * below indirect blocks, nothing to be done.
 547          */
 548         if (!topdir || limit <= SHMEM_NR_DIRECT)
 549                 goto done2;
 550
 551         /*
 552          * The truncation case has already dropped info->lock, and we're safe
 553          * because i_size and next_index have already been lowered, preventing
 554          * access beyond.  But in the punch_hole case, we still need to take
 555          * the lock when updating the swap directory, because there might be
 556          * racing accesses by shmem_getpage(SGP_CACHE), shmem_unuse_inode or
 557          * shmem_writepage.  However, whenever we find we can remove a whole
 558          * directory page (not at the misaligned start or end of the range),
 559          * we first NULLify its pointer in the level above, and then have no
 560          * need to take the lock when updating its contents: needs_lock and
 561          * punch_lock (either pointing to info->lock or NULL) manage this.
 562          */
 563
 564         upper_limit -= SHMEM_NR_DIRECT;
 565         limit -= SHMEM_NR_DIRECT;
 566         idx = (idx > SHMEM_NR_DIRECT)? (idx - SHMEM_NR_DIRECT): 0;
 567         offset = idx % ENTRIES_PER_PAGE;
 568         idx -= offset;
 569
 570         dir = shmem_dir_map(topdir);
 571         stage = ENTRIES_PER_PAGEPAGE/2;
 572         if (idx < ENTRIES_PER_PAGEPAGE/2) {
 573                 middir = topdir;
 574                 diroff = idx/ENTRIES_PER_PAGE;
 575         } else {
 576                 dir += ENTRIES_PER_PAGE/2;
 577                 dir += (idx - ENTRIES_PER_PAGEPAGE/2)/ENTRIES_PER_PAGEPAGE;
 578                 while (stage <= idx)
 579                         stage += ENTRIES_PER_PAGEPAGE;
 580                 middir = *dir;
 581                 if (*dir) {
 582                         diroff = ((idx - ENTRIES_PER_PAGEPAGE/2) %
 583                                 ENTRIES_PER_PAGEPAGE) / ENTRIES_PER_PAGE;
 584                         if (!diroff && !offset && upper_limit >= stage) {
 585                                 if (needs_lock) {
 586                                         spin_lock(needs_lock);
 587                                         *dir = NULL;
 588                                         spin_unlock(needs_lock);
 589                                         needs_lock = NULL;
 590                                 } else
 591                                         *dir = NULL;
 592                                 nr_pages_to_free++;
 593                                 list_add(&middir->lru, &pages_to_free);
 594                         }
 595                         shmem_dir_unmap(dir);
 596                         dir = shmem_dir_map(middir);
 597                 } else {
 598                         diroff = 0;
 599                         offset = 0;
 600                         idx = stage;
 601                 }
 602         }
 603
 604         for (; idx < limit; idx += ENTRIES_PER_PAGE, diroff++) {
 605                 if (unlikely(idx == stage)) {
 606                         shmem_dir_unmap(dir);
 607                         dir = shmem_dir_map(topdir) +
 608                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
 609                         while (!*dir) {
 610                                 dir++;
 611                                 idx += ENTRIES_PER_PAGEPAGE;
 612                                 if (idx >= limit)
 613                                         goto done1;
 614                         }
 615                         stage = idx + ENTRIES_PER_PAGEPAGE;
 616                         middir = *dir;
 617                         if (punch_hole)
 618                                 needs_lock = &info->lock;
 619                         if (upper_limit >= stage) {
 620                                 if (needs_lock) {
 621                                         spin_lock(needs_lock);
 622                                         *dir = NULL;
 623                                         spin_unlock(needs_lock);
 624                                         needs_lock = NULL;
 625                                 } else
 626                                         *dir = NULL;
 627                                 nr_pages_to_free++;
 628                                 list_add(&middir->lru, &pages_to_free);
 629                         }
 630                         shmem_dir_unmap(dir);
 631                         cond_resched();
 632                         dir = shmem_dir_map(middir);
 633                         diroff = 0;
 634                 }
 635                 punch_lock = needs_lock;
 636                 subdir = dir[diroff];
 637                 if (subdir && !offset && upper_limit-idx >= ENTRIES_PER_PAGE) {
 638                         if (needs_lock) {
 639                                 spin_lock(needs_lock);
 640                                 dir[diroff] = NULL;
 641                                 spin_unlock(needs_lock);
 642                                 punch_lock = NULL;
 643                         } else
 644                                 dir[diroff] = NULL;
 645                         nr_pages_to_free++;
 646                         list_add(&subdir->lru, &pages_to_free);
 647                 }
 648                 if (subdir && page_private(subdir) /* has swap entries */) {
 649                         size = limit - idx;
 650                         if (size > ENTRIES_PER_PAGE)
 651                                 size = ENTRIES_PER_PAGE;
 652                         freed = shmem_map_and_free_swp(subdir,
 653                                         offset, size, &dir, punch_lock);
 654                         if (!dir)
 655                                 dir = shmem_dir_map(middir);
 656                         nr_swaps_freed += freed;
 657                         if (offset || punch_lock) {
 658                                 spin_lock(&info->lock);
 659                                 set_page_private(subdir,
 660                                         page_private(subdir) - freed);
 661                                 spin_unlock(&info->lock);
 662                         } else
 663                                 BUG_ON(page_private(subdir) != freed);
 664                 }
 665                 offset = 0;
 666         }
 667 done1:
 668         shmem_dir_unmap(dir);
 669 done2:
 670         if (inode->i_mapping->nrpages && (info->flags & SHMEM_PAGEIN)) {
 671                 /*
 672                  * Call truncate_inode_pages again: racing shmem_unuse_inode
 673                  * may have swizzled a page in from swap since vmtruncate or
 674                  * generic_delete_inode did it, before we lowered next_index.
 675                  * Also, though shmem_getpage checks i_size before adding to
 676                  * cache, no recheck after: so fix the narrow window there too.
 677                  */
 678                 truncate_inode_pages_range(inode->i_mapping, start, end);
 679         }
 680
 681         spin_lock(&info->lock);
 682         info->flags &= ~SHMEM_TRUNCATE;
 683         info->swapped -= nr_swaps_freed;
 684         if (nr_pages_to_free)
 685                 shmem_free_blocks(inode, nr_pages_to_free);
 686         shmem_recalc_inode(inode);
 687         spin_unlock(&info->lock);
 688
 689         /*
 690          * Empty swap vector directory pages to be freed?
 691          */
 692         if (!list_empty(&pages_to_free)) {
 693                 pages_to_free.prev->next = NULL;
 694                 shmem_free_pages(pages_to_free.next);
 695         }
 696 }
 697
 698 static void shmem_truncate(struct inode *inode)
 699 {
 700         shmem_truncate_range(inode, inode->i_size, (loff_t)-1);
 701 }
 702
 703 static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
 704 {
 705         struct inode *inode = dentry->d_inode;
 706         struct page *page = NULL;
 707         int error;
 708
 709         if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
 710                 if (attr->ia_size < inode->i_size) {
 711                         /*
 712                          * If truncating down to a partial page, then
 713                          * if that page is already allocated, hold it
 714                          * in memory until the truncation is over, so
 715                          * truncate_partial_page cannnot miss it were
 716                          * it assigned to swap.
 717                          */
 718                         if (attr->ia_size & (PAGE_CACHE_SIZE-1)) {
 719                                 (void) shmem_getpage(inode,
 720                                         attr->ia_size>>PAGE_CACHE_SHIFT,
 721                                                 &page, SGP_READ, NULL);
 722                         }
 723                         /*
 724                          * Reset SHMEM_PAGEIN flag so that shmem_truncate can
 725                          * detect if any pages might have been added to cache
 726                          * after truncate_inode_pages.  But we needn't bother
 727                          * if it's being fully truncated to zero-length: the
 728                          * nrpages check is efficient enough in that case.
 729                          */
 730                         if (attr->ia_size) {
 731                                 struct shmem_inode_info *info = SHMEM_I(inode);
 732                                 spin_lock(&info->lock);
 733                                 info->flags &= ~SHMEM_PAGEIN;
 734                                 spin_unlock(&info->lock);
 735                         }
 736                 }
 737         }
 738
 739         error = inode_change_ok(inode, attr);
 740         if (!error)
 741                 error = inode_setattr(inode, attr);
 742 #ifdef CONFIG_TMPFS_POSIX_ACL
 743         if (!error && (attr->ia_valid & ATTR_MODE))
 744                 error = generic_acl_chmod(inode, &shmem_acl_ops);
 745 #endif
 746         if (page)
 747                 page_cache_release(page);
 748         return error;
 749 }
 750
 751 static void shmem_delete_inode(struct inode *inode)
 752 {
 753         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 754         struct shmem_inode_info *info = SHMEM_I(inode);
 755
 756         if (inode->i_op->truncate == shmem_truncate) {
 757                 truncate_inode_pages(inode->i_mapping, 0);
 758                 shmem_unacct_size(info->flags, inode->i_size);
 759                 inode->i_size = 0;
 760                 shmem_truncate(inode);
 761                 if (!list_empty(&info->swaplist)) {
 762                         spin_lock(&shmem_swaplist_lock);
 763                         list_del_init(&info->swaplist);
 764                         spin_unlock(&shmem_swaplist_lock);
 765                 }
 766         }
 767         BUG_ON(inode->i_blocks);
 768         if (sbinfo->max_inodes) {
 769                 spin_lock(&sbinfo->stat_lock);
 770                 sbinfo->free_inodes++;
 771                 spin_unlock(&sbinfo->stat_lock);
 772         }
 773         clear_inode(inode);
 774 }
 775
 776 static inline int shmem_find_swp(swp_entry_t entry, swp_entry_t *dir, swp_entry_t *edir)
 777 {
 778         swp_entry_t *ptr;
 779
 780         for (ptr = dir; ptr < edir; ptr++) {
 781                 if (ptr->val == entry.val)
 782                         return ptr - dir;
 783         }
 784         return -1;
 785 }
 786
 787 static int shmem_unuse_inode(struct shmem_inode_info *info, swp_entry_t entry, struct page *page)
 788 {
 789         struct inode *inode;
 790         unsigned long idx;
 791         unsigned long size;
 792         unsigned long limit;
 793         unsigned long stage;
 794         struct page **dir;
 795         struct page *subdir;
 796         swp_entry_t *ptr;
 797         int offset;
 798
 799         idx = 0;
 800         ptr = info->i_direct;
 801         spin_lock(&info->lock);
 802         limit = info->next_index;
 803         size = limit;
 804         if (size > SHMEM_NR_DIRECT)
 805                 size = SHMEM_NR_DIRECT;
 806         offset = shmem_find_swp(entry, ptr, ptr+size);
 807         if (offset >= 0) {
 808                 shmem_swp_balance_unmap();
 809                 goto found;
 810         }
 811         if (!info->i_indirect)
 812                 goto lost2;
 813
 814         dir = shmem_dir_map(info->i_indirect);
 815         stage = SHMEM_NR_DIRECT + ENTRIES_PER_PAGEPAGE/2;
 816
 817         for (idx = SHMEM_NR_DIRECT; idx < limit; idx += ENTRIES_PER_PAGE, dir++) {
 818                 if (unlikely(idx == stage)) {
 819                         shmem_dir_unmap(dir-1);
 820                         dir = shmem_dir_map(info->i_indirect) +
 821                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
 822                         while (!*dir) {
 823                                 dir++;
 824                                 idx += ENTRIES_PER_PAGEPAGE;
 825                                 if (idx >= limit)
 826                                         goto lost1;
 827                         }
 828                         stage = idx + ENTRIES_PER_PAGEPAGE;
 829                         subdir = *dir;
 830                         shmem_dir_unmap(dir);
 831                         dir = shmem_dir_map(subdir);
 832                 }
 833                 subdir = *dir;
 834                 if (subdir && page_private(subdir)) {
 835                         ptr = shmem_swp_map(subdir);
 836                         size = limit - idx;
 837                         if (size > ENTRIES_PER_PAGE)
 838                                 size = ENTRIES_PER_PAGE;
 839                         offset = shmem_find_swp(entry, ptr, ptr+size);
 840                         if (offset >= 0) {
 841                                 shmem_dir_unmap(dir);
 842                                 goto found;
 843                         }
 844                         shmem_swp_unmap(ptr);
 845                 }
 846         }
 847 lost1:
 848         shmem_dir_unmap(dir-1);
 849 lost2:
 850         spin_unlock(&info->lock);
 851         return 0;
 852 found:
 853         idx += offset;
 854         inode = &info->vfs_inode;
 855         if (move_from_swap_cache(page, idx, inode->i_mapping) == 0) {
 856                 info->flags |= SHMEM_PAGEIN;
 857                 shmem_swp_set(info, ptr + offset, 0);
 858         }
 859         shmem_swp_unmap(ptr);
 860         spin_unlock(&info->lock);
 861         /*
 862          * Decrement swap count even when the entry is left behind:
 863          * try_to_unuse will skip over mms, then reincrement count.
 864          */
 865         swap_free(entry);
 866         return 1;
 867 }
 868
 869 /*
 870  * shmem_unuse() search for an eventually swapped out shmem page.
 871  */
 872 int shmem_unuse(swp_entry_t entry, struct page *page)
 873 {
 874         struct list_head *p, *next;
 875         struct shmem_inode_info *info;
 876         int found = 0;
 877
 878         spin_lock(&shmem_swaplist_lock);
 879         list_for_each_safe(p, next, &shmem_swaplist) {
 880                 info = list_entry(p, struct shmem_inode_info, swaplist);
 881                 if (!info->swapped)
 882                         list_del_init(&info->swaplist);
 883                 else if (shmem_unuse_inode(info, entry, page)) {
 884                         /* move head to start search for next from here */
 885                         list_move_tail(&shmem_swaplist, &info->swaplist);
 886                         found = 1;
 887                         break;
 888                 }
 889         }
 890         spin_unlock(&shmem_swaplist_lock);
 891         return found;
 892 }
 893
 894 /*
 895  * Move the page from the page cache to the swap cache.
 896  */
 897 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 898 {
 899         struct shmem_inode_info *info;
 900         swp_entry_t *entry, swap;
 901         struct address_space *mapping;
 902         unsigned long index;
 903         struct inode *inode;
 904
 905         BUG_ON(!PageLocked(page));
 906         BUG_ON(page_mapped(page));
 907
 908         mapping = page->mapping;
 909         index = page->index;
 910         inode = mapping->host;
 911         info = SHMEM_I(inode);
 912         if (info->flags & VM_LOCKED)
 913                 goto redirty;
 914         swap = get_swap_page();
 915         if (!swap.val)
 916                 goto redirty;
 917
 918         spin_lock(&info->lock);
 919         shmem_recalc_inode(inode);
 920         if (index >= info->next_index) {
 921                 BUG_ON(!(info->flags & SHMEM_TRUNCATE));
 922                 goto unlock;
 923         }
 924         entry = shmem_swp_entry(info, index, NULL);
 925         BUG_ON(!entry);
 926         BUG_ON(entry->val);
 927
 928         if (move_to_swap_cache(page, swap) == 0) {
 929                 shmem_swp_set(info, entry, swap.val);
 930                 shmem_swp_unmap(entry);
 931                 spin_unlock(&info->lock);
 932                 if (list_empty(&info->swaplist)) {
 933                         spin_lock(&shmem_swaplist_lock);
 934                         /* move instead of add in case we're racing */
 935                         list_move_tail(&info->swaplist, &shmem_swaplist);
 936                         spin_unlock(&shmem_swaplist_lock);
 937                 }
 938                 unlock_page(page);
 939                 return 0;
 940         }
 941
 942         shmem_swp_unmap(entry);
 943 unlock:
 944         spin_unlock(&info->lock);
 945         swap_free(swap);
 946 redirty:
 947         set_page_dirty(page);
 948         return AOP_WRITEPAGE_ACTIVATE;  /* Return with the page locked */
 949 }
 950
 951 #ifdef CONFIG_NUMA
 952 static inline int shmem_parse_mpol(char *value, int *policy, nodemask_t *policy_nodes)
 953 {
 954         char *nodelist = strchr(value, ':');
 955         int err = 1;
 956
 957         if (nodelist) {
 958                 /* NUL-terminate policy string */
 959                 *nodelist++ = '\0';
 960                 if (nodelist_parse(nodelist, *policy_nodes))
 961                         goto out;
 962         }
 963         if (!strcmp(value, "default")) {
 964                 *policy = MPOL_DEFAULT;
 965                 /* Don't allow a nodelist */
 966                 if (!nodelist)
 967                         err = 0;
 968         } else if (!strcmp(value, "prefer")) {
 969                 *policy = MPOL_PREFERRED;
 970                 /* Insist on a nodelist of one node only */
 971                 if (nodelist) {
 972                         char *rest = nodelist;
 973                         while (isdigit(*rest))
 974                                 rest++;
 975                         if (!*rest)
 976                                 err = 0;
 977                 }
 978         } else if (!strcmp(value, "bind")) {
 979                 *policy = MPOL_BIND;
 980                 /* Insist on a nodelist */
 981                 if (nodelist)
 982                         err = 0;
 983         } else if (!strcmp(value, "interleave")) {
 984                 *policy = MPOL_INTERLEAVE;
 985                 /* Default to nodes online if no nodelist */
 986                 if (!nodelist)
 987                         *policy_nodes = node_online_map;
 988                 err = 0;
 989         }
 990 out:
 991         /* Restore string for error message */
 992         if (nodelist)
 993                 *--nodelist = ':';
 994         return err;
 995 }
 996
 997 static struct page *shmem_swapin_async(struct shared_policy *p,
 998                                        swp_entry_t entry, unsigned long idx)
 999 {
1000         struct page *page;
1001         struct vm_area_struct pvma;
1002
1003         /* Create a pseudo vma that just contains the policy */
1004         memset(&pvma, 0, sizeof(struct vm_area_struct));
1005         pvma.vm_end = PAGE_SIZE;
1006         pvma.vm_pgoff = idx;
1007         pvma.vm_policy = mpol_shared_policy_lookup(p, idx);
1008         page = read_swap_cache_async(entry, &pvma, 0);
1009         mpol_free(pvma.vm_policy);
1010         return page;
1011 }
1012
1013 struct page *shmem_swapin(struct shmem_inode_info *info, swp_entry_t entry,
1014                           unsigned long idx)
1015 {
1016         struct shared_policy *p = &info->policy;
1017         int i, num;
1018         struct page *page;
1019         unsigned long offset;
1020
1021         num = valid_swaphandles(entry, &offset);
1022         for (i = 0; i < num; offset++, i++) {
1023                 page = shmem_swapin_async(p,
1024                                 swp_entry(swp_type(entry), offset), idx);
1025                 if (!page)
1026                         break;
1027                 page_cache_release(page);
1028         }
1029         lru_add_drain();        /* Push any new pages onto the LRU now */
1030         return shmem_swapin_async(p, entry, idx);
1031 }
1032
1033 static struct page *
1034 shmem_alloc_page(gfp_t gfp, struct shmem_inode_info *info,
1035                  unsigned long idx)
1036 {
1037         struct vm_area_struct pvma;
1038         struct page *page;
1039
1040         memset(&pvma, 0, sizeof(struct vm_area_struct));
1041         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx);
1042         pvma.vm_pgoff = idx;
1043         pvma.vm_end = PAGE_SIZE;
1044         page = alloc_page_vma(gfp | __GFP_ZERO, &pvma, 0);
1045         mpol_free(pvma.vm_policy);
1046         return page;
1047 }
1048 #else
1049 static inline int shmem_parse_mpol(char *value, int *policy, nodemask_t *policy_nodes)
1050 {
1051         return 1;
1052 }
1053
1054 static inline struct page *
1055 shmem_swapin(struct shmem_inode_info *info,swp_entry_t entry,unsigned long idx)
1056 {
1057         swapin_readahead(entry, 0, NULL);
1058         return read_swap_cache_async(entry, NULL, 0);
1059 }
1060
1061 static inline struct page *
1062 shmem_alloc_page(gfp_t gfp,struct shmem_inode_info *info, unsigned long idx)
1063 {
1064         return alloc_page(gfp | __GFP_ZERO);
1065 }
1066 #endif
1067
1068 /*
1069  * shmem_getpage - either get the page from swap or allocate a new one
1070  *
1071  * If we allocate a new one we do not mark it dirty. That's up to the
1072  * vm. If we swap it in we mark it dirty since we also free the swap
1073  * entry since a page cannot live in both the swap and page cache
1074  */
1075 static int shmem_getpage(struct inode *inode, unsigned long idx,
1076                         struct page **pagep, enum sgp_type sgp, int *type)
1077 {
1078         struct address_space *mapping = inode->i_mapping;
1079         struct shmem_inode_info *info = SHMEM_I(inode);
1080         struct shmem_sb_info *sbinfo;
1081         struct page *filepage = *pagep;
1082         struct page *swappage;
1083         swp_entry_t *entry;
1084         swp_entry_t swap;
1085         int error;
1086
1087         if (idx >= SHMEM_MAX_INDEX)
1088                 return -EFBIG;
1089         /*
1090          * Normally, filepage is NULL on entry, and either found
1091          * uptodate immediately, or allocated and zeroed, or read
1092          * in under swappage, which is then assigned to filepage.
1093          * But shmem_prepare_write passes in a locked filepage,
1094          * which may be found not uptodate by other callers too,
1095          * and may need to be copied from the swappage read in.
1096          */
1097 repeat:
1098         if (!filepage)
1099                 filepage = find_lock_page(mapping, idx);
1100         if (filepage && PageUptodate(filepage))
1101                 goto done;
1102         error = 0;
1103         if (sgp == SGP_QUICK)
1104                 goto failed;
1105
1106         spin_lock(&info->lock);
1107         shmem_recalc_inode(inode);
1108         entry = shmem_swp_alloc(info, idx, sgp);
1109         if (IS_ERR(entry)) {
1110                 spin_unlock(&info->lock);
1111                 error = PTR_ERR(entry);
1112                 goto failed;
1113         }
1114         swap = *entry;
1115
1116         if (swap.val) {
1117                 /* Look it up and read it in.. */
1118                 swappage = lookup_swap_cache(swap);
1119                 if (!swappage) {
1120                         shmem_swp_unmap(entry);
1121                         /* here we actually do the io */
1122                         if (type && *type == VM_FAULT_MINOR) {
1123                                 __count_vm_event(PGMAJFAULT);
1124                                 *type = VM_FAULT_MAJOR;
1125                         }
1126                         spin_unlock(&info->lock);
1127                         swappage = shmem_swapin(info, swap, idx);
1128                         if (!swappage) {
1129                                 spin_lock(&info->lock);
1130                                 entry = shmem_swp_alloc(info, idx, sgp);
1131                                 if (IS_ERR(entry))
1132                                         error = PTR_ERR(entry);
1133                                 else {
1134                                         if (entry->val == swap.val)
1135                                                 error = -ENOMEM;
1136                                         shmem_swp_unmap(entry);
1137                                 }
1138                                 spin_unlock(&info->lock);
1139                                 if (error)
1140                                         goto failed;
1141                                 goto repeat;
1142                         }
1143                         wait_on_page_locked(swappage);
1144                         page_cache_release(swappage);
1145                         goto repeat;
1146                 }
1147
1148                 /* We have to do this with page locked to prevent races */
1149                 if (TestSetPageLocked(swappage)) {
1150                         shmem_swp_unmap(entry);
1151                         spin_unlock(&info->lock);
1152                         wait_on_page_locked(swappage);
1153                         page_cache_release(swappage);
1154                         goto repeat;
1155                 }
1156                 if (PageWriteback(swappage)) {
1157                         shmem_swp_unmap(entry);
1158                         spin_unlock(&info->lock);
1159                         wait_on_page_writeback(swappage);
1160                         unlock_page(swappage);
1161                         page_cache_release(swappage);
1162                         goto repeat;
1163                 }
1164                 if (!PageUptodate(swappage)) {
1165                         shmem_swp_unmap(entry);
1166                         spin_unlock(&info->lock);
1167                         unlock_page(swappage);
1168                         page_cache_release(swappage);
1169                         error = -EIO;
1170                         goto failed;
1171                 }
1172
1173                 if (filepage) {
1174                         shmem_swp_set(info, entry, 0);
1175                         shmem_swp_unmap(entry);
1176                         delete_from_swap_cache(swappage);
1177                         spin_unlock(&info->lock);
1178                         copy_highpage(filepage, swappage);
1179                         unlock_page(swappage);
1180                         page_cache_release(swappage);
1181                         flush_dcache_page(filepage);
1182                         SetPageUptodate(filepage);
1183                         set_page_dirty(filepage);
1184                         swap_free(swap);
1185                 } else if (!(error = move_from_swap_cache(
1186                                 swappage, idx, mapping))) {
1187                         info->flags |= SHMEM_PAGEIN;
1188                         shmem_swp_set(info, entry, 0);
1189                         shmem_swp_unmap(entry);
1190                         spin_unlock(&info->lock);
1191                         filepage = swappage;
1192                         swap_free(swap);
1193                 } else {
1194                         shmem_swp_unmap(entry);
1195                         spin_unlock(&info->lock);
1196                         unlock_page(swappage);
1197                         page_cache_release(swappage);
1198                         if (error == -ENOMEM) {
1199                                 /* let kswapd refresh zone for GFP_ATOMICs */
1200                                 congestion_wait(WRITE, HZ/50);
1201                         }
1202                         goto repeat;
1203                 }
1204         } else if (sgp == SGP_READ && !filepage) {
1205                 shmem_swp_unmap(entry);
1206                 filepage = find_get_page(mapping, idx);
1207                 if (filepage &&
1208                     (!PageUptodate(filepage) || TestSetPageLocked(filepage))) {
1209                         spin_unlock(&info->lock);
1210                         wait_on_page_locked(filepage);
1211                         page_cache_release(filepage);
1212                         filepage = NULL;
1213                         goto repeat;
1214                 }
1215                 spin_unlock(&info->lock);
1216         } else {
1217                 shmem_swp_unmap(entry);
1218                 sbinfo = SHMEM_SB(inode->i_sb);
1219                 if (sbinfo->max_blocks) {
1220                         spin_lock(&sbinfo->stat_lock);
1221                         if (sbinfo->free_blocks == 0 ||
1222                             shmem_acct_block(info->flags)) {
1223                                 spin_unlock(&sbinfo->stat_lock);
1224                                 spin_unlock(&info->lock);
1225                                 error = -ENOSPC;
1226                                 goto failed;
1227                         }
1228                         sbinfo->free_blocks--;
1229                         inode->i_blocks += BLOCKS_PER_PAGE;
1230                         spin_unlock(&sbinfo->stat_lock);
1231                 } else if (shmem_acct_block(info->flags)) {
1232                         spin_unlock(&info->lock);
1233                         error = -ENOSPC;
1234                         goto failed;
1235                 }
1236
1237                 if (!filepage) {
1238                         spin_unlock(&info->lock);
1239                         filepage = shmem_alloc_page(mapping_gfp_mask(mapping),
1240                                                     info,
1241                                                     idx);
1242                         if (!filepage) {
1243                                 shmem_unacct_blocks(info->flags, 1);
1244                                 shmem_free_blocks(inode, 1);
1245                                 error = -ENOMEM;
1246                                 goto failed;
1247                         }
1248
1249                         spin_lock(&info->lock);
1250                         entry = shmem_swp_alloc(info, idx, sgp);
1251                         if (IS_ERR(entry))
1252                                 error = PTR_ERR(entry);
1253                         else {
1254                                 swap = *entry;
1255                                 shmem_swp_unmap(entry);
1256                         }
1257                         if (error || swap.val || 0 != add_to_page_cache_lru(
1258                                         filepage, mapping, idx, GFP_ATOMIC)) {
1259                                 spin_unlock(&info->lock);
1260                                 page_cache_release(filepage);
1261                                 shmem_unacct_blocks(info->flags, 1);
1262                                 shmem_free_blocks(inode, 1);
1263                                 filepage = NULL;
1264                                 if (error)
1265                                         goto failed;
1266                                 goto repeat;
1267                         }
1268                         info->flags |= SHMEM_PAGEIN;
1269                 }
1270
1271                 info->alloced++;
1272                 spin_unlock(&info->lock);
1273                 flush_dcache_page(filepage);
1274                 SetPageUptodate(filepage);
1275         }
1276 done:
1277         if (*pagep != filepage) {
1278                 unlock_page(filepage);
1279                 *pagep = filepage;
1280         }
1281         return 0;
1282
1283 failed:
1284         if (*pagep != filepage) {
1285                 unlock_page(filepage);
1286                 page_cache_release(filepage);
1287         }
1288         return error;
1289 }
1290
1291 static struct page *shmem_nopage(struct vm_area_struct *vma,
1292                                  unsigned long address, int *type)
1293 {
1294         struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1295         struct page *page = NULL;
1296         unsigned long idx;
1297         int error;
1298
1299         idx = (address - vma->vm_start) >> PAGE_SHIFT;
1300         idx += vma->vm_pgoff;
1301         idx >>= PAGE_CACHE_SHIFT - PAGE_SHIFT;
1302         if (((loff_t) idx << PAGE_CACHE_SHIFT) >= i_size_read(inode))
1303                 return NOPAGE_SIGBUS;
1304
1305         error = shmem_getpage(inode, idx, &page, SGP_CACHE, type);
1306         if (error)
1307                 return (error == -ENOMEM)? NOPAGE_OOM: NOPAGE_SIGBUS;
1308
1309         mark_page_accessed(page);
1310         return page;
1311 }
1312
1313 static int shmem_populate(struct vm_area_struct *vma,
1314         unsigned long addr, unsigned long len,
1315         pgprot_t prot, unsigned long pgoff, int nonblock)
1316 {
1317         struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1318         struct mm_struct *mm = vma->vm_mm;
1319         enum sgp_type sgp = nonblock? SGP_QUICK: SGP_CACHE;
1320         unsigned long size;
1321
1322         size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
1323         if (pgoff >= size || pgoff + (len >> PAGE_SHIFT) > size)
1324                 return -EINVAL;
1325
1326         while ((long) len > 0) {
1327                 struct page *page = NULL;
1328                 int err;
1329                 /*
1330                  * Will need changing if PAGE_CACHE_SIZE != PAGE_SIZE
1331                  */
1332                 err = shmem_getpage(inode, pgoff, &page, sgp, NULL);
1333                 if (err)
1334                         return err;
1335                 /* Page may still be null, but only if nonblock was set. */
1336                 if (page) {
1337                         mark_page_accessed(page);
1338                         err = install_page(mm, vma, addr, page, prot);
1339                         if (err) {
1340                                 page_cache_release(page);
1341                                 return err;
1342                         }
1343                 } else if (vma->vm_flags & VM_NONLINEAR) {
1344                         /* No page was found just because we can't read it in
1345                          * now (being here implies nonblock != 0), but the page
1346                          * may exist, so set the PTE to fault it in later. */
1347                         err = install_file_pte(mm, vma, addr, pgoff, prot);
1348                         if (err)
1349                                 return err;
1350                 }
1351
1352                 len -= PAGE_SIZE;
1353                 addr += PAGE_SIZE;
1354                 pgoff++;
1355         }
1356         return 0;
1357 }
1358
1359 #ifdef CONFIG_NUMA
1360 int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *new)
1361 {
1362         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1363         return mpol_set_shared_policy(&SHMEM_I(i)->policy, vma, new);
1364 }
1365
1366 struct mempolicy *
1367 shmem_get_policy(struct vm_area_struct *vma, unsigned long addr)
1368 {
1369         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1370         unsigned long idx;
1371
1372         idx = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1373         return mpol_shared_policy_lookup(&SHMEM_I(i)->policy, idx);
1374 }
1375 #endif
1376
1377 int shmem_lock(struct file *file, int lock, struct user_struct *user)
1378 {
1379         struct inode *inode = file->f_path.dentry->d_inode;
1380         struct shmem_inode_info *info = SHMEM_I(inode);
1381         int retval = -ENOMEM;
1382
1383         spin_lock(&info->lock);
1384         if (lock && !(info->flags & VM_LOCKED)) {
1385                 if (!user_shm_lock(inode->i_size, user))
1386                         goto out_nomem;
1387                 info->flags |= VM_LOCKED;
1388         }
1389         if (!lock && (info->flags & VM_LOCKED) && user) {
1390                 user_shm_unlock(inode->i_size, user);
1391                 info->flags &= ~VM_LOCKED;
1392         }
1393         retval = 0;
1394 out_nomem:
1395         spin_unlock(&info->lock);
1396         return retval;
1397 }
1398
1399 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1400 {
1401         file_accessed(file);
1402         vma->vm_ops = &shmem_vm_ops;
1403         return 0;
1404 }
1405
1406 static struct inode *
1407 shmem_get_inode(struct super_block *sb, int mode, dev_t dev)
1408 {
1409         struct inode *inode;
1410         struct shmem_inode_info *info;
1411         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1412
1413         if (sbinfo->max_inodes) {
1414                 spin_lock(&sbinfo->stat_lock);
1415                 if (!sbinfo->free_inodes) {
1416                         spin_unlock(&sbinfo->stat_lock);
1417                         return NULL;
1418                 }
1419                 sbinfo->free_inodes--;
1420                 spin_unlock(&sbinfo->stat_lock);
1421         }
1422
1423         inode = new_inode(sb);
1424         if (inode) {
1425                 inode->i_mode = mode;
1426                 inode->i_uid = current->fsuid;
1427                 inode->i_gid = current->fsgid;
1428                 inode->i_blocks = 0;
1429                 inode->i_mapping->a_ops = &shmem_aops;
1430                 inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1431                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1432                 inode->i_generation = get_seconds();
1433                 info = SHMEM_I(inode);
1434                 memset(info, 0, (char *)inode - (char *)info);
1435                 spin_lock_init(&info->lock);
1436                 INIT_LIST_HEAD(&info->swaplist);
1437
1438                 switch (mode & S_IFMT) {
1439                 default:
1440                         inode->i_op = &shmem_special_inode_operations;
1441                         init_special_inode(inode, mode, dev);
1442                         break;
1443                 case S_IFREG:
1444                         inode->i_op = &shmem_inode_operations;
1445                         inode->i_fop = &shmem_file_operations;
1446                         mpol_shared_policy_init(&info->policy, sbinfo->policy,
1447                                                         &sbinfo->policy_nodes);
1448                         break;
1449                 case S_IFDIR:
1450                         inc_nlink(inode);
1451                         /* Some things misbehave if size == 0 on a directory */
1452                         inode->i_size = 2 * BOGO_DIRENT_SIZE;
1453                         inode->i_op = &shmem_dir_inode_operations;
1454                         inode->i_fop = &simple_dir_operations;
1455                         break;
1456                 case S_IFLNK:
1457                         /*
1458                          * Must not load anything in the rbtree,
1459                          * mpol_free_shared_policy will not be called.
1460                          */
1461                         mpol_shared_policy_init(&info->policy, MPOL_DEFAULT,
1462                                                 NULL);
1463                         break;
1464                 }
1465         } else if (sbinfo->max_inodes) {
1466                 spin_lock(&sbinfo->stat_lock);
1467                 sbinfo->free_inodes++;
1468                 spin_unlock(&sbinfo->stat_lock);
1469         }
1470         return inode;
1471 }
1472
1473 #ifdef CONFIG_TMPFS
1474 static const struct inode_operations shmem_symlink_inode_operations;
1475 static const struct inode_operations shmem_symlink_inline_operations;
1476
1477 /*
1478  * Normally tmpfs makes no use of shmem_prepare_write, but it
1479  * lets a tmpfs file be used read-write below the loop driver.
1480  */
1481 static int
1482 shmem_prepare_write(struct file *file, struct page *page, unsigned offset, unsigned to)
1483 {
1484         struct inode *inode = page->mapping->host;
1485         return shmem_getpage(inode, page->index, &page, SGP_WRITE, NULL);
1486 }
1487
1488 static ssize_t
1489 shmem_file_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
1490 {
1491         struct inode    *inode = file->f_path.dentry->d_inode;
1492         loff_t          pos;
1493         unsigned long   written;
1494         ssize_t         err;
1495
1496         if ((ssize_t) count < 0)
1497                 return -EINVAL;
1498
1499         if (!access_ok(VERIFY_READ, buf, count))
1500                 return -EFAULT;
1501
1502         mutex_lock(&inode->i_mutex);
1503
1504         pos = *ppos;
1505         written = 0;
1506
1507         err = generic_write_checks(file, &pos, &count, 0);
1508         if (err || !count)
1509                 goto out;
1510
1511         err = remove_suid(file->f_path.dentry);
1512         if (err)
1513                 goto out;
1514
1515         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
1516
1517         do {
1518                 struct page *page = NULL;
1519                 unsigned long bytes, index, offset;
1520                 char *kaddr;
1521                 int left;
1522
1523                 offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
1524                 index = pos >> PAGE_CACHE_SHIFT;
1525                 bytes = PAGE_CACHE_SIZE - offset;
1526                 if (bytes > count)
1527                         bytes = count;
1528
1529                 /*
1530                  * We don't hold page lock across copy from user -
1531                  * what would it guard against? - so no deadlock here.
1532                  * But it still may be a good idea to prefault below.
1533                  */
1534
1535                 err = shmem_getpage(inode, index, &page, SGP_WRITE, NULL);
1536                 if (err)
1537                         break;
1538
1539                 left = bytes;
1540                 if (PageHighMem(page)) {
1541                         volatile unsigned char dummy;
1542                         __get_user(dummy, buf);
1543                         __get_user(dummy, buf + bytes - 1);
1544
1545                         kaddr = kmap_atomic(page, KM_USER0);
1546                         left = __copy_from_user_inatomic(kaddr + offset,
1547                                                         buf, bytes);
1548                         kunmap_atomic(kaddr, KM_USER0);
1549                 }
1550                 if (left) {
1551                         kaddr = kmap(page);
1552                         left = __copy_from_user(kaddr + offset, buf, bytes);
1553                         kunmap(page);
1554                 }
1555
1556                 written += bytes;
1557                 count -= bytes;
1558                 pos += bytes;
1559                 buf += bytes;
1560                 if (pos > inode->i_size)
1561                         i_size_write(inode, pos);
1562
1563                 flush_dcache_page(page);
1564                 set_page_dirty(page);
1565                 mark_page_accessed(page);
1566                 page_cache_release(page);
1567
1568                 if (left) {
1569                         pos -= left;
1570                         written -= left;
1571                         err = -EFAULT;
1572                         break;
1573                 }
1574
1575                 /*
1576                  * Our dirty pages are not counted in nr_dirty,
1577                  * and we do not attempt to balance dirty pages.
1578                  */
1579
1580                 cond_resched();
1581         } while (count);
1582
1583         *ppos = pos;
1584         if (written)
1585                 err = written;
1586 out:
1587         mutex_unlock(&inode->i_mutex);
1588         return err;
1589 }
1590
1591 static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
1592 {
1593         struct inode *inode = filp->f_path.dentry->d_inode;
1594         struct address_space *mapping = inode->i_mapping;
1595         unsigned long index, offset;
1596
1597         index = *ppos >> PAGE_CACHE_SHIFT;
1598         offset = *ppos & ~PAGE_CACHE_MASK;
1599
1600         for (;;) {
1601                 struct page *page = NULL;
1602                 unsigned long end_index, nr, ret;
1603                 loff_t i_size = i_size_read(inode);
1604
1605                 end_index = i_size >> PAGE_CACHE_SHIFT;
1606                 if (index > end_index)
1607                         break;
1608                 if (index == end_index) {
1609                         nr = i_size & ~PAGE_CACHE_MASK;
1610                         if (nr <= offset)
1611                                 break;
1612                 }
1613
1614                 desc->error = shmem_getpage(inode, index, &page, SGP_READ, NULL);
1615                 if (desc->error) {
1616                         if (desc->error == -EINVAL)
1617                                 desc->error = 0;
1618                         break;
1619                 }
1620
1621                 /*
1622                  * We must evaluate after, since reads (unlike writes)
1623                  * are called without i_mutex protection against truncate
1624                  */
1625                 nr = PAGE_CACHE_SIZE;
1626                 i_size = i_size_read(inode);
1627                 end_index = i_size >> PAGE_CACHE_SHIFT;
1628                 if (index == end_index) {
1629                         nr = i_size & ~PAGE_CACHE_MASK;
1630                         if (nr <= offset) {
1631                                 if (page)
1632                                         page_cache_release(page);
1633                                 break;
1634                         }
1635                 }
1636                 nr -= offset;
1637
1638                 if (page) {
1639                         /*
1640                          * If users can be writing to this page using arbitrary
1641                          * virtual addresses, take care about potential aliasing
1642                          * before reading the page on the kernel side.
1643                          */
1644                         if (mapping_writably_mapped(mapping))
1645                                 flush_dcache_page(page);
1646                         /*
1647                          * Mark the page accessed if we read the beginning.
1648                          */
1649                         if (!offset)
1650                                 mark_page_accessed(page);
1651                 } else {
1652                         page = ZERO_PAGE(0);
1653                         page_cache_get(page);
1654                 }
1655
1656                 /*
1657                  * Ok, we have the page, and it's up-to-date, so
1658                  * now we can copy it to user space...
1659                  *
1660                  * The actor routine returns how many bytes were actually used..
1661                  * NOTE! This may not be the same as how much of a user buffer
1662                  * we filled up (we may be padding etc), so we can only update
1663                  * "pos" here (the actor routine has to update the user buffer
1664                  * pointers and the remaining count).
1665                  */
1666                 ret = actor(desc, page, offset, nr);
1667                 offset += ret;
1668                 index += offset >> PAGE_CACHE_SHIFT;
1669                 offset &= ~PAGE_CACHE_MASK;
1670
1671                 page_cache_release(page);
1672                 if (ret != nr || !desc->count)
1673                         break;
1674
1675                 cond_resched();
1676         }
1677
1678         *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1679         file_accessed(filp);
1680 }
1681
1682 static ssize_t shmem_file_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
1683 {
1684         read_descriptor_t desc;
1685
1686         if ((ssize_t) count < 0)
1687                 return -EINVAL;
1688         if (!access_ok(VERIFY_WRITE, buf, count))
1689                 return -EFAULT;
1690         if (!count)
1691                 return 0;
1692
1693         desc.written = 0;
1694         desc.count = count;
1695         desc.arg.buf = buf;
1696         desc.error = 0;
1697
1698         do_shmem_file_read(filp, ppos, &desc, file_read_actor);
1699         if (desc.written)
1700                 return desc.written;
1701         return desc.error;
1702 }
1703
1704 static ssize_t shmem_file_sendfile(struct file *in_file, loff_t *ppos,
1705                          size_t count, read_actor_t actor, void *target)
1706 {
1707         read_descriptor_t desc;
1708
1709         if (!count)
1710                 return 0;
1711
1712         desc.written = 0;
1713         desc.count = count;
1714         desc.arg.data = target;
1715         desc.error = 0;
1716
1717         do_shmem_file_read(in_file, ppos, &desc, actor);
1718         if (desc.written)
1719                 return desc.written;
1720         return desc.error;
1721 }
1722
1723 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
1724 {
1725         struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
1726
1727         buf->f_type = TMPFS_MAGIC;
1728         buf->f_bsize = PAGE_CACHE_SIZE;
1729         buf->f_namelen = NAME_MAX;
1730         spin_lock(&sbinfo->stat_lock);
1731         if (sbinfo->max_blocks) {
1732                 buf->f_blocks = sbinfo->max_blocks;
1733                 buf->f_bavail = buf->f_bfree = sbinfo->free_blocks;
1734         }
1735         if (sbinfo->max_inodes) {
1736                 buf->f_files = sbinfo->max_inodes;
1737                 buf->f_ffree = sbinfo->free_inodes;
1738         }
1739         /* else leave those fields 0 like simple_statfs */
1740         spin_unlock(&sbinfo->stat_lock);
1741         return 0;
1742 }
1743
1744 /*
1745  * File creation. Allocate an inode, and we're done..
1746  */
1747 static int
1748 shmem_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
1749 {
1750         struct inode *inode = shmem_get_inode(dir->i_sb, mode, dev);
1751         int error = -ENOSPC;
1752
1753         if (inode) {
1754                 error = security_inode_init_security(inode, dir, NULL, NULL,
1755                                                      NULL);
1756                 if (error) {
1757                         if (error != -EOPNOTSUPP) {
1758                                 iput(inode);
1759                                 return error;
1760                         }
1761                 }
1762                 error = shmem_acl_init(inode, dir);
1763                 if (error) {
1764                         iput(inode);
1765                         return error;
1766                 }
1767                 if (dir->i_mode & S_ISGID) {
1768                         inode->i_gid = dir->i_gid;
1769                         if (S_ISDIR(mode))
1770                                 inode->i_mode |= S_ISGID;
1771                 }
1772                 dir->i_size += BOGO_DIRENT_SIZE;
1773                 dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1774                 d_instantiate(dentry, inode);
1775                 dget(dentry); /* Extra count - pin the dentry in core */
1776         }
1777         return error;
1778 }
1779
1780 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, int mode)
1781 {
1782         int error;
1783
1784         if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
1785                 return error;
1786         inc_nlink(dir);
1787         return 0;
1788 }
1789
1790 static int shmem_create(struct inode *dir, struct dentry *dentry, int mode,
1791                 struct nameidata *nd)
1792 {
1793         return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
1794 }
1795
1796 /*
1797  * Link a file..
1798  */
1799 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
1800 {
1801         struct inode *inode = old_dentry->d_inode;
1802         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1803
1804         /*
1805          * No ordinary (disk based) filesystem counts links as inodes;
1806          * but each new link needs a new dentry, pinning lowmem, and
1807          * tmpfs dentries cannot be pruned until they are unlinked.
1808          */
1809         if (sbinfo->max_inodes) {
1810                 spin_lock(&sbinfo->stat_lock);
1811                 if (!sbinfo->free_inodes) {
1812                         spin_unlock(&sbinfo->stat_lock);
1813                         return -ENOSPC;
1814                 }
1815                 sbinfo->free_inodes--;
1816                 spin_unlock(&sbinfo->stat_lock);
1817         }
1818
1819         dir->i_size += BOGO_DIRENT_SIZE;
1820         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1821         inc_nlink(inode);
1822         atomic_inc(&inode->i_count);    /* New dentry reference */
1823         dget(dentry);           /* Extra pinning count for the created dentry */
1824         d_instantiate(dentry, inode);
1825         return 0;
1826 }
1827
1828 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
1829 {
1830         struct inode *inode = dentry->d_inode;
1831
1832         if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode)) {
1833                 struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1834                 if (sbinfo->max_inodes) {
1835                         spin_lock(&sbinfo->stat_lock);
1836                         sbinfo->free_inodes++;
1837                         spin_unlock(&sbinfo->stat_lock);
1838                 }
1839         }
1840
1841         dir->i_size -= BOGO_DIRENT_SIZE;
1842         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1843         drop_nlink(inode);
1844         dput(dentry);   /* Undo the count from "create" - this does all the work */
1845         return 0;
1846 }
1847
1848 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
1849 {
1850         if (!simple_empty(dentry))
1851                 return -ENOTEMPTY;
1852
1853         drop_nlink(dentry->d_inode);
1854         drop_nlink(dir);
1855         return shmem_unlink(dir, dentry);
1856 }
1857
1858 /*
1859  * The VFS layer already does all the dentry stuff for rename,
1860  * we just have to decrement the usage count for the target if
1861  * it exists so that the VFS layer correctly free's it when it
1862  * gets overwritten.
1863  */
1864 static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
1865 {
1866         struct inode *inode = old_dentry->d_inode;
1867         int they_are_dirs = S_ISDIR(inode->i_mode);
1868
1869         if (!simple_empty(new_dentry))
1870                 return -ENOTEMPTY;
1871
1872         if (new_dentry->d_inode) {
1873                 (void) shmem_unlink(new_dir, new_dentry);
1874                 if (they_are_dirs)
1875                         drop_nlink(old_dir);
1876         } else if (they_are_dirs) {
1877                 drop_nlink(old_dir);
1878                 inc_nlink(new_dir);
1879         }
1880
1881         old_dir->i_size -= BOGO_DIRENT_SIZE;
1882         new_dir->i_size += BOGO_DIRENT_SIZE;
1883         old_dir->i_ctime = old_dir->i_mtime =
1884         new_dir->i_ctime = new_dir->i_mtime =
1885         inode->i_ctime = CURRENT_TIME;
1886         return 0;
1887 }
1888
1889 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
1890 {
1891         int error;
1892         int len;
1893         struct inode *inode;
1894         struct page *page = NULL;
1895         char *kaddr;
1896         struct shmem_inode_info *info;
1897
1898         len = strlen(symname) + 1;
1899         if (len > PAGE_CACHE_SIZE)
1900                 return -ENAMETOOLONG;
1901
1902         inode = shmem_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0);
1903         if (!inode)
1904                 return -ENOSPC;
1905
1906         error = security_inode_init_security(inode, dir, NULL, NULL,
1907                                              NULL);
1908         if (error) {
1909                 if (error != -EOPNOTSUPP) {
1910                         iput(inode);
1911                         return error;
1912                 }
1913                 error = 0;
1914         }
1915
1916         info = SHMEM_I(inode);
1917         inode->i_size = len-1;
1918         if (len <= (char *)inode - (char *)info) {
1919                 /* do it inline */
1920                 memcpy(info, symname, len);
1921                 inode->i_op = &shmem_symlink_inline_operations;
1922         } else {
1923                 error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
1924                 if (error) {
1925                         iput(inode);
1926                         return error;
1927                 }
1928                 inode->i_op = &shmem_symlink_inode_operations;
1929                 kaddr = kmap_atomic(page, KM_USER0);
1930                 memcpy(kaddr, symname, len);
1931                 kunmap_atomic(kaddr, KM_USER0);
1932                 set_page_dirty(page);
1933                 page_cache_release(page);
1934         }
1935         if (dir->i_mode & S_ISGID)
1936                 inode->i_gid = dir->i_gid;
1937         dir->i_size += BOGO_DIRENT_SIZE;
1938         dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1939         d_instantiate(dentry, inode);
1940         dget(dentry);
1941         return 0;
1942 }
1943
1944 static void *shmem_follow_link_inline(struct dentry *dentry, struct nameidata *nd)
1945 {
1946         nd_set_link(nd, (char *)SHMEM_I(dentry->d_inode));
1947         return NULL;
1948 }
1949
1950 static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
1951 {
1952         struct page *page = NULL;
1953         int res = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
1954         nd_set_link(nd, res ? ERR_PTR(res) : kmap(page));
1955         return page;
1956 }
1957
1958 static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
1959 {
1960         if (!IS_ERR(nd_get_link(nd))) {
1961                 struct page *page = cookie;
1962                 kunmap(page);
1963                 mark_page_accessed(page);
1964                 page_cache_release(page);
1965         }
1966 }
1967
1968 static const struct inode_operations shmem_symlink_inline_operations = {
1969         .readlink       = generic_readlink,
1970         .follow_link    = shmem_follow_link_inline,
1971 };
1972
1973 static const struct inode_operations shmem_symlink_inode_operations = {
1974         .truncate       = shmem_truncate,
1975         .readlink       = generic_readlink,
1976         .follow_link    = shmem_follow_link,
1977         .put_link       = shmem_put_link,
1978 };
1979
1980 #ifdef CONFIG_TMPFS_POSIX_ACL
1981 /**
1982  * Superblocks without xattr inode operations will get security.* xattr
1983  * support from the VFS "for free". As soon as we have any other xattrs
1984  * like ACLs, we also need to implement the security.* handlers at
1985  * filesystem level, though.
1986  */
1987
1988 static size_t shmem_xattr_security_list(struct inode *inode, char *list,
1989                                         size_t list_len, const char *name,
1990                                         size_t name_len)
1991 {
1992         return security_inode_listsecurity(inode, list, list_len);
1993 }
1994
1995 static int shmem_xattr_security_get(struct inode *inode, const char *name,
1996                                     void *buffer, size_t size)
1997 {
1998         if (strcmp(name, "") == 0)
1999                 return -EINVAL;
2000         return security_inode_getsecurity(inode, name, buffer, size,
2001                                           -EOPNOTSUPP);
2002 }
2003
2004 static int shmem_xattr_security_set(struct inode *inode, const char *name,
2005                                     const void *value, size_t size, int flags)
2006 {
2007         if (strcmp(name, "") == 0)
2008                 return -EINVAL;
2009         return security_inode_setsecurity(inode, name, value, size, flags);
2010 }
2011
2012 static struct xattr_handler shmem_xattr_security_handler = {
2013         .prefix = XATTR_SECURITY_PREFIX,
2014         .list   = shmem_xattr_security_list,
2015         .get    = shmem_xattr_security_get,
2016         .set    = shmem_xattr_security_set,
2017 };
2018
2019 static struct xattr_handler *shmem_xattr_handlers[] = {
2020         &shmem_xattr_acl_access_handler,
2021         &shmem_xattr_acl_default_handler,
2022         &shmem_xattr_security_handler,
2023         NULL
2024 };
2025 #endif
2026
2027 static struct dentry *shmem_get_parent(struct dentry *child)
2028 {
2029         return ERR_PTR(-ESTALE);
2030 }
2031
2032 static int shmem_match(struct inode *ino, void *vfh)
2033 {
2034         __u32 *fh = vfh;
2035         __u64 inum = fh[2];
2036         inum = (inum << 32) | fh[1];
2037         return ino->i_ino == inum && fh[0] == ino->i_generation;
2038 }
2039
2040 static struct dentry *shmem_get_dentry(struct super_block *sb, void *vfh)
2041 {
2042         struct dentry *de = NULL;
2043         struct inode *inode;
2044         __u32 *fh = vfh;
2045         __u64 inum = fh[2];
2046         inum = (inum << 32) | fh[1];
2047
2048         inode = ilookup5(sb, (unsigned long)(inum+fh[0]), shmem_match, vfh);
2049         if (inode) {
2050                 de = d_find_alias(inode);
2051                 iput(inode);
2052         }
2053
2054         return de? de: ERR_PTR(-ESTALE);
2055 }
2056
2057 static struct dentry *shmem_decode_fh(struct super_block *sb, __u32 *fh,
2058                 int len, int type,
2059                 int (*acceptable)(void *context, struct dentry *de),
2060                 void *context)
2061 {
2062         if (len < 3)
2063                 return ERR_PTR(-ESTALE);
2064
2065         return sb->s_export_op->find_exported_dentry(sb, fh, NULL, acceptable,
2066                                                         context);
2067 }
2068
2069 static int shmem_encode_fh(struct dentry *dentry, __u32 *fh, int *len,
2070                                 int connectable)
2071 {
2072         struct inode *inode = dentry->d_inode;
2073
2074         if (*len < 3)
2075                 return 255;
2076
2077         if (hlist_unhashed(&inode->i_hash)) {
2078                 /* Unfortunately insert_inode_hash is not idempotent,
2079                  * so as we hash inodes here rather than at creation
2080                  * time, we need a lock to ensure we only try
2081                  * to do it once
2082                  */
2083                 static DEFINE_SPINLOCK(lock);
2084                 spin_lock(&lock);
2085                 if (hlist_unhashed(&inode->i_hash))
2086                         __insert_inode_hash(inode,
2087                                             inode->i_ino + inode->i_generation);
2088                 spin_unlock(&lock);
2089         }
2090
2091         fh[0] = inode->i_generation;
2092         fh[1] = inode->i_ino;
2093         fh[2] = ((__u64)inode->i_ino) >> 32;
2094
2095         *len = 3;
2096         return 1;
2097 }
2098
2099 static struct export_operations shmem_export_ops = {
2100         .get_parent     = shmem_get_parent,
2101         .get_dentry     = shmem_get_dentry,
2102         .encode_fh      = shmem_encode_fh,
2103         .decode_fh      = shmem_decode_fh,
2104 };
2105
2106 static int shmem_parse_options(char *options, int *mode, uid_t *uid,
2107         gid_t *gid, unsigned long *blocks, unsigned long *inodes,
2108         int *policy, nodemask_t *policy_nodes)
2109 {
2110         char *this_char, *value, *rest;
2111
2112         while (options != NULL) {
2113                 this_char = options;
2114                 for (;;) {
2115                         /*
2116                          * NUL-terminate this option: unfortunately,
2117                          * mount options form a comma-separated list,
2118                          * but mpol's nodelist may also contain commas.
2119                          */
2120                         options = strchr(options, ',');
2121                         if (options == NULL)
2122                                 break;
2123                         options++;
2124                         if (!isdigit(*options)) {
2125                                 options[-1] = '\0';
2126                                 break;
2127                         }
2128                 }
2129                 if (!*this_char)
2130                         continue;
2131                 if ((value = strchr(this_char,'=')) != NULL) {
2132                         *value++ = 0;
2133                 } else {
2134                         printk(KERN_ERR
2135                             "tmpfs: No value for mount option '%s'\n",
2136                             this_char);
2137                         return 1;
2138                 }
2139
2140                 if (!strcmp(this_char,"size")) {
2141                         unsigned long long size;
2142                         size = memparse(value,&rest);
2143                         if (*rest == '%') {
2144                                 size <<= PAGE_SHIFT;
2145                                 size *= totalram_pages;
2146                                 do_div(size, 100);
2147                                 rest++;
2148                         }
2149                         if (*rest)
2150                                 goto bad_val;
2151                         *blocks = size >> PAGE_CACHE_SHIFT;
2152                 } else if (!strcmp(this_char,"nr_blocks")) {
2153                         *blocks = memparse(value,&rest);
2154                         if (*rest)
2155                                 goto bad_val;
2156                 } else if (!strcmp(this_char,"nr_inodes")) {
2157                         *inodes = memparse(value,&rest);
2158                         if (*rest)
2159                                 goto bad_val;
2160                 } else if (!strcmp(this_char,"mode")) {
2161                         if (!mode)
2162                                 continue;
2163                         *mode = simple_strtoul(value,&rest,8);
2164                         if (*rest)
2165                                 goto bad_val;
2166                 } else if (!strcmp(this_char,"uid")) {
2167                         if (!uid)
2168                                 continue;
2169                         *uid = simple_strtoul(value,&rest,0);
2170                         if (*rest)
2171                                 goto bad_val;
2172                 } else if (!strcmp(this_char,"gid")) {
2173                         if (!gid)
2174                                 continue;
2175                         *gid = simple_strtoul(value,&rest,0);
2176                         if (*rest)
2177                                 goto bad_val;
2178                 } else if (!strcmp(this_char,"mpol")) {
2179                         if (shmem_parse_mpol(value,policy,policy_nodes))
2180                                 goto bad_val;
2181                 } else {
2182                         printk(KERN_ERR "tmpfs: Bad mount option %s\n",
2183                                this_char);
2184                         return 1;
2185                 }
2186         }
2187         return 0;
2188
2189 bad_val:
2190         printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
2191                value, this_char);
2192         return 1;
2193
2194 }
2195
2196 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2197 {
2198         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2199         unsigned long max_blocks = sbinfo->max_blocks;
2200         unsigned long max_inodes = sbinfo->max_inodes;
2201         int policy = sbinfo->policy;
2202         nodemask_t policy_nodes = sbinfo->policy_nodes;
2203         unsigned long blocks;
2204         unsigned long inodes;
2205         int error = -EINVAL;
2206
2207         if (shmem_parse_options(data, NULL, NULL, NULL, &max_blocks,
2208                                 &max_inodes, &policy, &policy_nodes))
2209                 return error;
2210
2211         spin_lock(&sbinfo->stat_lock);
2212         blocks = sbinfo->max_blocks - sbinfo->free_blocks;
2213         inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2214         if (max_blocks < blocks)
2215                 goto out;
2216         if (max_inodes < inodes)
2217                 goto out;
2218         /*
2219          * Those tests also disallow limited->unlimited while any are in
2220          * use, so i_blocks will always be zero when max_blocks is zero;
2221          * but we must separately disallow unlimited->limited, because
2222          * in that case we have no record of how much is already in use.
2223          */
2224         if (max_blocks && !sbinfo->max_blocks)
2225                 goto out;
2226         if (max_inodes && !sbinfo->max_inodes)
2227                 goto out;
2228
2229         error = 0;
2230         sbinfo->max_blocks  = max_blocks;
2231         sbinfo->free_blocks = max_blocks - blocks;
2232         sbinfo->max_inodes  = max_inodes;
2233         sbinfo->free_inodes = max_inodes - inodes;
2234         sbinfo->policy = policy;
2235         sbinfo->policy_nodes = policy_nodes;
2236 out:
2237         spin_unlock(&sbinfo->stat_lock);
2238         return error;
2239 }
2240 #endif
2241
2242 static void shmem_put_super(struct super_block *sb)
2243 {
2244         kfree(sb->s_fs_info);
2245         sb->s_fs_info = NULL;
2246 }
2247
2248 static int shmem_fill_super(struct super_block *sb,
2249                             void *data, int silent)
2250 {
2251         struct inode *inode;
2252         struct dentry *root;
2253         int mode   = S_IRWXUGO | S_ISVTX;
2254         uid_t uid = current->fsuid;
2255         gid_t gid = current->fsgid;
2256         int err = -ENOMEM;
2257         struct shmem_sb_info *sbinfo;
2258         unsigned long blocks = 0;
2259         unsigned long inodes = 0;
2260         int policy = MPOL_DEFAULT;
2261         nodemask_t policy_nodes = node_online_map;
2262
2263 #ifdef CONFIG_TMPFS
2264         /*
2265          * Per default we only allow half of the physical ram per
2266          * tmpfs instance, limiting inodes to one per page of lowmem;
2267          * but the internal instance is left unlimited.
2268          */
2269         if (!(sb->s_flags & MS_NOUSER)) {
2270                 blocks = totalram_pages / 2;
2271                 inodes = totalram_pages - totalhigh_pages;
2272                 if (inodes > blocks)
2273                         inodes = blocks;
2274                 if (shmem_parse_options(data, &mode, &uid, &gid, &blocks,
2275                                         &inodes, &policy, &policy_nodes))
2276                         return -EINVAL;
2277         }
2278         sb->s_export_op = &shmem_export_ops;
2279 #else
2280         sb->s_flags |= MS_NOUSER;
2281 #endif
2282
2283         /* Round up to L1_CACHE_BYTES to resist false sharing */
2284         sbinfo = kmalloc(max((int)sizeof(struct shmem_sb_info),
2285                                 L1_CACHE_BYTES), GFP_KERNEL);
2286         if (!sbinfo)
2287                 return -ENOMEM;
2288
2289         spin_lock_init(&sbinfo->stat_lock);
2290         sbinfo->max_blocks = blocks;
2291         sbinfo->free_blocks = blocks;
2292         sbinfo->max_inodes = inodes;
2293         sbinfo->free_inodes = inodes;
2294         sbinfo->policy = policy;
2295         sbinfo->policy_nodes = policy_nodes;
2296
2297         sb->s_fs_info = sbinfo;
2298         sb->s_maxbytes = SHMEM_MAX_BYTES;
2299         sb->s_blocksize = PAGE_CACHE_SIZE;
2300         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
2301         sb->s_magic = TMPFS_MAGIC;
2302         sb->s_op = &shmem_ops;
2303         sb->s_time_gran = 1;
2304 #ifdef CONFIG_TMPFS_POSIX_ACL
2305         sb->s_xattr = shmem_xattr_handlers;
2306         sb->s_flags |= MS_POSIXACL;
2307 #endif
2308
2309         inode = shmem_get_inode(sb, S_IFDIR | mode, 0);
2310         if (!inode)
2311                 goto failed;
2312         inode->i_uid = uid;
2313         inode->i_gid = gid;
2314         root = d_alloc_root(inode);
2315         if (!root)
2316                 goto failed_iput;
2317         sb->s_root = root;
2318         return 0;
2319
2320 failed_iput:
2321         iput(inode);
2322 failed:
2323         shmem_put_super(sb);
2324         return err;
2325 }
2326
2327 static struct kmem_cache *shmem_inode_cachep;
2328
2329 static struct inode *shmem_alloc_inode(struct super_block *sb)
2330 {
2331         struct shmem_inode_info *p;
2332         p = (struct shmem_inode_info *)kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
2333         if (!p)
2334                 return NULL;
2335         return &p->vfs_inode;
2336 }
2337
2338 static void shmem_destroy_inode(struct inode *inode)
2339 {
2340         if ((inode->i_mode & S_IFMT) == S_IFREG) {
2341                 /* only struct inode is valid if it's an inline symlink */
2342                 mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2343         }
2344         shmem_acl_destroy_inode(inode);
2345         kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2346 }
2347
2348 static void init_once(void *foo, struct kmem_cache *cachep,
2349                       unsigned long flags)
2350 {
2351         struct shmem_inode_info *p = (struct shmem_inode_info *) foo;
2352
2353         if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
2354             SLAB_CTOR_CONSTRUCTOR) {
2355                 inode_init_once(&p->vfs_inode);
2356 #ifdef CONFIG_TMPFS_POSIX_ACL
2357                 p->i_acl = NULL;
2358                 p->i_default_acl = NULL;
2359 #endif
2360         }
2361 }
2362
2363 static int init_inodecache(void)
2364 {
2365         shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
2366                                 sizeof(struct shmem_inode_info),
2367                                 0, 0, init_once, NULL);
2368         if (shmem_inode_cachep == NULL)
2369                 return -ENOMEM;
2370         return 0;
2371 }
2372
2373 static void destroy_inodecache(void)
2374 {
2375         kmem_cache_destroy(shmem_inode_cachep);
2376 }
2377
2378 static const struct address_space_operations shmem_aops = {
2379         .writepage      = shmem_writepage,
2380         .set_page_dirty = __set_page_dirty_no_writeback,
2381 #ifdef CONFIG_TMPFS
2382         .prepare_write  = shmem_prepare_write,
2383         .commit_write   = simple_commit_write,
2384 #endif
2385         .migratepage    = migrate_page,
2386 };
2387
2388 static const struct file_operations shmem_file_operations = {
2389         .mmap           = shmem_mmap,
2390 #ifdef CONFIG_TMPFS
2391         .llseek         = generic_file_llseek,
2392         .read           = shmem_file_read,
2393         .write          = shmem_file_write,
2394         .fsync          = simple_sync_file,
2395         .sendfile       = shmem_file_sendfile,
2396 #endif
2397 };
2398
2399 static const struct inode_operations shmem_inode_operations = {
2400         .truncate       = shmem_truncate,
2401         .setattr        = shmem_notify_change,
2402         .truncate_range = shmem_truncate_range,
2403 #ifdef CONFIG_TMPFS_POSIX_ACL
2404         .setxattr       = generic_setxattr,
2405         .getxattr       = generic_getxattr,
2406         .listxattr      = generic_listxattr,
2407         .removexattr    = generic_removexattr,
2408         .permission     = shmem_permission,
2409 #endif
2410
2411 };
2412
2413 static const struct inode_operations shmem_dir_inode_operations = {
2414 #ifdef CONFIG_TMPFS
2415         .create         = shmem_create,
2416         .lookup         = simple_lookup,
2417         .link           = shmem_link,
2418         .unlink         = shmem_unlink,
2419         .symlink        = shmem_symlink,
2420         .mkdir          = shmem_mkdir,
2421         .rmdir          = shmem_rmdir,
2422         .mknod          = shmem_mknod,
2423         .rename         = shmem_rename,
2424 #endif
2425 #ifdef CONFIG_TMPFS_POSIX_ACL
2426         .setattr        = shmem_notify_change,
2427         .setxattr       = generic_setxattr,
2428         .getxattr       = generic_getxattr,
2429         .listxattr      = generic_listxattr,
2430         .removexattr    = generic_removexattr,
2431         .permission     = shmem_permission,
2432 #endif
2433 };
2434
2435 static const struct inode_operations shmem_special_inode_operations = {
2436 #ifdef CONFIG_TMPFS_POSIX_ACL
2437         .setattr        = shmem_notify_change,
2438         .setxattr       = generic_setxattr,
2439         .getxattr       = generic_getxattr,
2440         .listxattr      = generic_listxattr,
2441         .removexattr    = generic_removexattr,
2442         .permission     = shmem_permission,
2443 #endif
2444 };
2445
2446 static const struct super_operations shmem_ops = {
2447         .alloc_inode    = shmem_alloc_inode,
2448         .destroy_inode  = shmem_destroy_inode,
2449 #ifdef CONFIG_TMPFS
2450         .statfs         = shmem_statfs,
2451         .remount_fs     = shmem_remount_fs,
2452 #endif
2453         .delete_inode   = shmem_delete_inode,
2454         .drop_inode     = generic_delete_inode,
2455         .put_super      = shmem_put_super,
2456 };
2457
2458 static struct vm_operations_struct shmem_vm_ops = {
2459         .nopage         = shmem_nopage,
2460         .populate       = shmem_populate,
2461 #ifdef CONFIG_NUMA
2462         .set_policy     = shmem_set_policy,
2463         .get_policy     = shmem_get_policy,
2464 #endif
2465 };
2466
2467
2468 static int shmem_get_sb(struct file_system_type *fs_type,
2469         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
2470 {
2471         return get_sb_nodev(fs_type, flags, data, shmem_fill_super, mnt);
2472 }
2473
2474 static struct file_system_type tmpfs_fs_type = {
2475         .owner          = THIS_MODULE,
2476         .name           = "tmpfs",
2477         .get_sb         = shmem_get_sb,
2478         .kill_sb        = kill_litter_super,
2479 };
2480 static struct vfsmount *shm_mnt;
2481
2482 static int __init init_tmpfs(void)
2483 {
2484         int error;
2485
2486         error = init_inodecache();
2487         if (error)
2488                 goto out3;
2489
2490         error = register_filesystem(&tmpfs_fs_type);
2491         if (error) {
2492                 printk(KERN_ERR "Could not register tmpfs\n");
2493                 goto out2;
2494         }
2495
2496         shm_mnt = vfs_kern_mount(&tmpfs_fs_type, MS_NOUSER,
2497                                 tmpfs_fs_type.name, NULL);
2498         if (IS_ERR(shm_mnt)) {
2499                 error = PTR_ERR(shm_mnt);
2500                 printk(KERN_ERR "Could not kern_mount tmpfs\n");
2501                 goto out1;
2502         }
2503         return 0;
2504
2505 out1:
2506         unregister_filesystem(&tmpfs_fs_type);
2507 out2:
2508         destroy_inodecache();
2509 out3:
2510         shm_mnt = ERR_PTR(error);
2511         return error;
2512 }
2513 module_init(init_tmpfs)
2514
2515 /*
2516  * shmem_file_setup - get an unlinked file living in tmpfs
2517  *
2518  * @name: name for dentry (to be seen in /proc/<pid>/maps
2519  * @size: size to be set for the file
2520  *
2521  */
2522 struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags)
2523 {
2524         int error;
2525         struct file *file;
2526         struct inode *inode;
2527         struct dentry *dentry, *root;
2528         struct qstr this;
2529
2530         if (IS_ERR(shm_mnt))
2531                 return (void *)shm_mnt;
2532
2533         if (size < 0 || size > SHMEM_MAX_BYTES)
2534                 return ERR_PTR(-EINVAL);
2535
2536         if (shmem_acct_size(flags, size))
2537                 return ERR_PTR(-ENOMEM);
2538
2539         error = -ENOMEM;
2540         this.name = name;
2541         this.len = strlen(name);
2542         this.hash = 0; /* will go */
2543         root = shm_mnt->mnt_root;
2544         dentry = d_alloc(root, &this);
2545         if (!dentry)
2546                 goto put_memory;
2547
2548         error = -ENFILE;
2549         file = get_empty_filp();
2550         if (!file)
2551                 goto put_dentry;
2552
2553         error = -ENOSPC;
2554         inode = shmem_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0);
2555         if (!inode)
2556                 goto close_file;
2557
2558         SHMEM_I(inode)->flags = flags & VM_ACCOUNT;
2559         d_instantiate(dentry, inode);
2560         inode->i_size = size;
2561         inode->i_nlink = 0;     /* It is unlinked */
2562         file->f_path.mnt = mntget(shm_mnt);
2563         file->f_path.dentry = dentry;
2564         file->f_mapping = inode->i_mapping;
2565         file->f_op = &shmem_file_operations;
2566         file->f_mode = FMODE_WRITE | FMODE_READ;
2567         return file;
2568
2569 close_file:
2570         put_filp(file);
2571 put_dentry:
2572         dput(dentry);
2573 put_memory:
2574         shmem_unacct_size(flags, size);
2575         return ERR_PTR(error);
2576 }
2577
2578 /*
2579  * shmem_zero_setup - setup a shared anonymous mapping
2580  *
2581  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
2582  */
2583 int shmem_zero_setup(struct vm_area_struct *vma)
2584 {
2585         struct file *file;
2586         loff_t size = vma->vm_end - vma->vm_start;
2587
2588         file = shmem_file_setup("dev/zero", size, vma->vm_flags);
2589         if (IS_ERR(file))
2590                 return PTR_ERR(file);
2591
2592         if (vma->vm_file)
2593                 fput(vma->vm_file);
2594         vma->vm_file = file;
2595         vma->vm_ops = &shmem_vm_ops;
2596         return 0;
2597 }