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                  * Recalling truncate_inode_pages_range and unmap_mapping_range
 679                  * every time for punch_hole (which never got a chance to clear
 680                  * SHMEM_PAGEIN at the start of vmtruncate_range) is expensive,
 681                  * yet hardly ever necessary: try to optimize them out later.
 682                  */
 683                 truncate_inode_pages_range(inode->i_mapping, start, end);
 684                 if (punch_hole)
 685                         unmap_mapping_range(inode->i_mapping, start,
 686                                                         end - start, 1);
 687         }
 688
 689         spin_lock(&info->lock);
 690         info->flags &= ~SHMEM_TRUNCATE;
 691         info->swapped -= nr_swaps_freed;
 692         if (nr_pages_to_free)
 693                 shmem_free_blocks(inode, nr_pages_to_free);
 694         shmem_recalc_inode(inode);
 695         spin_unlock(&info->lock);
 696
 697         /*
 698          * Empty swap vector directory pages to be freed?
 699          */
 700         if (!list_empty(&pages_to_free)) {
 701                 pages_to_free.prev->next = NULL;
 702                 shmem_free_pages(pages_to_free.next);
 703         }
 704 }
 705
 706 static void shmem_truncate(struct inode *inode)
 707 {
 708         shmem_truncate_range(inode, inode->i_size, (loff_t)-1);
 709 }
 710
 711 static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
 712 {
 713         struct inode *inode = dentry->d_inode;
 714         struct page *page = NULL;
 715         int error;
 716
 717         if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
 718                 if (attr->ia_size < inode->i_size) {
 719                         /*
 720                          * If truncating down to a partial page, then
 721                          * if that page is already allocated, hold it
 722                          * in memory until the truncation is over, so
 723                          * truncate_partial_page cannnot miss it were
 724                          * it assigned to swap.
 725                          */
 726                         if (attr->ia_size & (PAGE_CACHE_SIZE-1)) {
 727                                 (void) shmem_getpage(inode,
 728                                         attr->ia_size>>PAGE_CACHE_SHIFT,
 729                                                 &page, SGP_READ, NULL);
 730                         }
 731                         /*
 732                          * Reset SHMEM_PAGEIN flag so that shmem_truncate can
 733                          * detect if any pages might have been added to cache
 734                          * after truncate_inode_pages.  But we needn't bother
 735                          * if it's being fully truncated to zero-length: the
 736                          * nrpages check is efficient enough in that case.
 737                          */
 738                         if (attr->ia_size) {
 739                                 struct shmem_inode_info *info = SHMEM_I(inode);
 740                                 spin_lock(&info->lock);
 741                                 info->flags &= ~SHMEM_PAGEIN;
 742                                 spin_unlock(&info->lock);
 743                         }
 744                 }
 745         }
 746
 747         error = inode_change_ok(inode, attr);
 748         if (!error)
 749                 error = inode_setattr(inode, attr);
 750 #ifdef CONFIG_TMPFS_POSIX_ACL
 751         if (!error && (attr->ia_valid & ATTR_MODE))
 752                 error = generic_acl_chmod(inode, &shmem_acl_ops);
 753 #endif
 754         if (page)
 755                 page_cache_release(page);
 756         return error;
 757 }
 758
 759 static void shmem_delete_inode(struct inode *inode)
 760 {
 761         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 762         struct shmem_inode_info *info = SHMEM_I(inode);
 763
 764         if (inode->i_op->truncate == shmem_truncate) {
 765                 truncate_inode_pages(inode->i_mapping, 0);
 766                 shmem_unacct_size(info->flags, inode->i_size);
 767                 inode->i_size = 0;
 768                 shmem_truncate(inode);
 769                 if (!list_empty(&info->swaplist)) {
 770                         spin_lock(&shmem_swaplist_lock);
 771                         list_del_init(&info->swaplist);
 772                         spin_unlock(&shmem_swaplist_lock);
 773                 }
 774         }
 775         BUG_ON(inode->i_blocks);
 776         if (sbinfo->max_inodes) {
 777                 spin_lock(&sbinfo->stat_lock);
 778                 sbinfo->free_inodes++;
 779                 spin_unlock(&sbinfo->stat_lock);
 780         }
 781         clear_inode(inode);
 782 }
 783
 784 static inline int shmem_find_swp(swp_entry_t entry, swp_entry_t *dir, swp_entry_t *edir)
 785 {
 786         swp_entry_t *ptr;
 787
 788         for (ptr = dir; ptr < edir; ptr++) {
 789                 if (ptr->val == entry.val)
 790                         return ptr - dir;
 791         }
 792         return -1;
 793 }
 794
 795 static int shmem_unuse_inode(struct shmem_inode_info *info, swp_entry_t entry, struct page *page)
 796 {
 797         struct inode *inode;
 798         unsigned long idx;
 799         unsigned long size;
 800         unsigned long limit;
 801         unsigned long stage;
 802         struct page **dir;
 803         struct page *subdir;
 804         swp_entry_t *ptr;
 805         int offset;
 806
 807         idx = 0;
 808         ptr = info->i_direct;
 809         spin_lock(&info->lock);
 810         limit = info->next_index;
 811         size = limit;
 812         if (size > SHMEM_NR_DIRECT)
 813                 size = SHMEM_NR_DIRECT;
 814         offset = shmem_find_swp(entry, ptr, ptr+size);
 815         if (offset >= 0) {
 816                 shmem_swp_balance_unmap();
 817                 goto found;
 818         }
 819         if (!info->i_indirect)
 820                 goto lost2;
 821
 822         dir = shmem_dir_map(info->i_indirect);
 823         stage = SHMEM_NR_DIRECT + ENTRIES_PER_PAGEPAGE/2;
 824
 825         for (idx = SHMEM_NR_DIRECT; idx < limit; idx += ENTRIES_PER_PAGE, dir++) {
 826                 if (unlikely(idx == stage)) {
 827                         shmem_dir_unmap(dir-1);
 828                         dir = shmem_dir_map(info->i_indirect) +
 829                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
 830                         while (!*dir) {
 831                                 dir++;
 832                                 idx += ENTRIES_PER_PAGEPAGE;
 833                                 if (idx >= limit)
 834                                         goto lost1;
 835                         }
 836                         stage = idx + ENTRIES_PER_PAGEPAGE;
 837                         subdir = *dir;
 838                         shmem_dir_unmap(dir);
 839                         dir = shmem_dir_map(subdir);
 840                 }
 841                 subdir = *dir;
 842                 if (subdir && page_private(subdir)) {
 843                         ptr = shmem_swp_map(subdir);
 844                         size = limit - idx;
 845                         if (size > ENTRIES_PER_PAGE)
 846                                 size = ENTRIES_PER_PAGE;
 847                         offset = shmem_find_swp(entry, ptr, ptr+size);
 848                         if (offset >= 0) {
 849                                 shmem_dir_unmap(dir);
 850                                 goto found;
 851                         }
 852                         shmem_swp_unmap(ptr);
 853                 }
 854         }
 855 lost1:
 856         shmem_dir_unmap(dir-1);
 857 lost2:
 858         spin_unlock(&info->lock);
 859         return 0;
 860 found:
 861         idx += offset;
 862         inode = &info->vfs_inode;
 863         if (move_from_swap_cache(page, idx, inode->i_mapping) == 0) {
 864                 info->flags |= SHMEM_PAGEIN;
 865                 shmem_swp_set(info, ptr + offset, 0);
 866         }
 867         shmem_swp_unmap(ptr);
 868         spin_unlock(&info->lock);
 869         /*
 870          * Decrement swap count even when the entry is left behind:
 871          * try_to_unuse will skip over mms, then reincrement count.
 872          */
 873         swap_free(entry);
 874         return 1;
 875 }
 876
 877 /*
 878  * shmem_unuse() search for an eventually swapped out shmem page.
 879  */
 880 int shmem_unuse(swp_entry_t entry, struct page *page)
 881 {
 882         struct list_head *p, *next;
 883         struct shmem_inode_info *info;
 884         int found = 0;
 885
 886         spin_lock(&shmem_swaplist_lock);
 887         list_for_each_safe(p, next, &shmem_swaplist) {
 888                 info = list_entry(p, struct shmem_inode_info, swaplist);
 889                 if (!info->swapped)
 890                         list_del_init(&info->swaplist);
 891                 else if (shmem_unuse_inode(info, entry, page)) {
 892                         /* move head to start search for next from here */
 893                         list_move_tail(&shmem_swaplist, &info->swaplist);
 894                         found = 1;
 895                         break;
 896                 }
 897         }
 898         spin_unlock(&shmem_swaplist_lock);
 899         return found;
 900 }
 901
 902 /*
 903  * Move the page from the page cache to the swap cache.
 904  */
 905 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 906 {
 907         struct shmem_inode_info *info;
 908         swp_entry_t *entry, swap;
 909         struct address_space *mapping;
 910         unsigned long index;
 911         struct inode *inode;
 912
 913         BUG_ON(!PageLocked(page));
 914         BUG_ON(page_mapped(page));
 915
 916         mapping = page->mapping;
 917         index = page->index;
 918         inode = mapping->host;
 919         info = SHMEM_I(inode);
 920         if (info->flags & VM_LOCKED)
 921                 goto redirty;
 922         swap = get_swap_page();
 923         if (!swap.val)
 924                 goto redirty;
 925
 926         spin_lock(&info->lock);
 927         shmem_recalc_inode(inode);
 928         if (index >= info->next_index) {
 929                 BUG_ON(!(info->flags & SHMEM_TRUNCATE));
 930                 goto unlock;
 931         }
 932         entry = shmem_swp_entry(info, index, NULL);
 933         BUG_ON(!entry);
 934         BUG_ON(entry->val);
 935
 936         if (move_to_swap_cache(page, swap) == 0) {
 937                 shmem_swp_set(info, entry, swap.val);
 938                 shmem_swp_unmap(entry);
 939                 spin_unlock(&info->lock);
 940                 if (list_empty(&info->swaplist)) {
 941                         spin_lock(&shmem_swaplist_lock);
 942                         /* move instead of add in case we're racing */
 943                         list_move_tail(&info->swaplist, &shmem_swaplist);
 944                         spin_unlock(&shmem_swaplist_lock);
 945                 }
 946                 unlock_page(page);
 947                 return 0;
 948         }
 949
 950         shmem_swp_unmap(entry);
 951 unlock:
 952         spin_unlock(&info->lock);
 953         swap_free(swap);
 954 redirty:
 955         set_page_dirty(page);
 956         return AOP_WRITEPAGE_ACTIVATE;  /* Return with the page locked */
 957 }
 958
 959 #ifdef CONFIG_NUMA
 960 static inline int shmem_parse_mpol(char *value, int *policy, nodemask_t *policy_nodes)
 961 {
 962         char *nodelist = strchr(value, ':');
 963         int err = 1;
 964
 965         if (nodelist) {
 966                 /* NUL-terminate policy string */
 967                 *nodelist++ = '\0';
 968                 if (nodelist_parse(nodelist, *policy_nodes))
 969                         goto out;
 970                 if (!nodes_subset(*policy_nodes, node_online_map))
 971                         goto out;
 972         }
 973         if (!strcmp(value, "default")) {
 974                 *policy = MPOL_DEFAULT;
 975                 /* Don't allow a nodelist */
 976                 if (!nodelist)
 977                         err = 0;
 978         } else if (!strcmp(value, "prefer")) {
 979                 *policy = MPOL_PREFERRED;
 980                 /* Insist on a nodelist of one node only */
 981                 if (nodelist) {
 982                         char *rest = nodelist;
 983                         while (isdigit(*rest))
 984                                 rest++;
 985                         if (!*rest)
 986                                 err = 0;
 987                 }
 988         } else if (!strcmp(value, "bind")) {
 989                 *policy = MPOL_BIND;
 990                 /* Insist on a nodelist */
 991                 if (nodelist)
 992                         err = 0;
 993         } else if (!strcmp(value, "interleave")) {
 994                 *policy = MPOL_INTERLEAVE;
 995                 /* Default to nodes online if no nodelist */
 996                 if (!nodelist)
 997                         *policy_nodes = node_online_map;
 998                 err = 0;
 999         }
1000 out:
1001         /* Restore string for error message */
1002         if (nodelist)
1003                 *--nodelist = ':';
1004         return err;
1005 }
1006
1007 static struct page *shmem_swapin_async(struct shared_policy *p,
1008                                        swp_entry_t entry, unsigned long idx)
1009 {
1010         struct page *page;
1011         struct vm_area_struct pvma;
1012
1013         /* Create a pseudo vma that just contains the policy */
1014         memset(&pvma, 0, sizeof(struct vm_area_struct));
1015         pvma.vm_end = PAGE_SIZE;
1016         pvma.vm_pgoff = idx;
1017         pvma.vm_policy = mpol_shared_policy_lookup(p, idx);
1018         page = read_swap_cache_async(entry, &pvma, 0);
1019         mpol_free(pvma.vm_policy);
1020         return page;
1021 }
1022
1023 struct page *shmem_swapin(struct shmem_inode_info *info, swp_entry_t entry,
1024                           unsigned long idx)
1025 {
1026         struct shared_policy *p = &info->policy;
1027         int i, num;
1028         struct page *page;
1029         unsigned long offset;
1030
1031         num = valid_swaphandles(entry, &offset);
1032         for (i = 0; i < num; offset++, i++) {
1033                 page = shmem_swapin_async(p,
1034                                 swp_entry(swp_type(entry), offset), idx);
1035                 if (!page)
1036                         break;
1037                 page_cache_release(page);
1038         }
1039         lru_add_drain();        /* Push any new pages onto the LRU now */
1040         return shmem_swapin_async(p, entry, idx);
1041 }
1042
1043 static struct page *
1044 shmem_alloc_page(gfp_t gfp, struct shmem_inode_info *info,
1045                  unsigned long idx)
1046 {
1047         struct vm_area_struct pvma;
1048         struct page *page;
1049
1050         memset(&pvma, 0, sizeof(struct vm_area_struct));
1051         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx);
1052         pvma.vm_pgoff = idx;
1053         pvma.vm_end = PAGE_SIZE;
1054         page = alloc_page_vma(gfp | __GFP_ZERO, &pvma, 0);
1055         mpol_free(pvma.vm_policy);
1056         return page;
1057 }
1058 #else
1059 static inline int shmem_parse_mpol(char *value, int *policy, nodemask_t *policy_nodes)
1060 {
1061         return 1;
1062 }
1063
1064 static inline struct page *
1065 shmem_swapin(struct shmem_inode_info *info,swp_entry_t entry,unsigned long idx)
1066 {
1067         swapin_readahead(entry, 0, NULL);
1068         return read_swap_cache_async(entry, NULL, 0);
1069 }
1070
1071 static inline struct page *
1072 shmem_alloc_page(gfp_t gfp,struct shmem_inode_info *info, unsigned long idx)
1073 {
1074         return alloc_page(gfp | __GFP_ZERO);
1075 }
1076 #endif
1077
1078 /*
1079  * shmem_getpage - either get the page from swap or allocate a new one
1080  *
1081  * If we allocate a new one we do not mark it dirty. That's up to the
1082  * vm. If we swap it in we mark it dirty since we also free the swap
1083  * entry since a page cannot live in both the swap and page cache
1084  */
1085 static int shmem_getpage(struct inode *inode, unsigned long idx,
1086                         struct page **pagep, enum sgp_type sgp, int *type)
1087 {
1088         struct address_space *mapping = inode->i_mapping;
1089         struct shmem_inode_info *info = SHMEM_I(inode);
1090         struct shmem_sb_info *sbinfo;
1091         struct page *filepage = *pagep;
1092         struct page *swappage;
1093         swp_entry_t *entry;
1094         swp_entry_t swap;
1095         int error;
1096
1097         if (idx >= SHMEM_MAX_INDEX)
1098                 return -EFBIG;
1099         /*
1100          * Normally, filepage is NULL on entry, and either found
1101          * uptodate immediately, or allocated and zeroed, or read
1102          * in under swappage, which is then assigned to filepage.
1103          * But shmem_prepare_write passes in a locked filepage,
1104          * which may be found not uptodate by other callers too,
1105          * and may need to be copied from the swappage read in.
1106          */
1107 repeat:
1108         if (!filepage)
1109                 filepage = find_lock_page(mapping, idx);
1110         if (filepage && PageUptodate(filepage))
1111                 goto done;
1112         error = 0;
1113         if (sgp == SGP_QUICK)
1114                 goto failed;
1115
1116         spin_lock(&info->lock);
1117         shmem_recalc_inode(inode);
1118         entry = shmem_swp_alloc(info, idx, sgp);
1119         if (IS_ERR(entry)) {
1120                 spin_unlock(&info->lock);
1121                 error = PTR_ERR(entry);
1122                 goto failed;
1123         }
1124         swap = *entry;
1125
1126         if (swap.val) {
1127                 /* Look it up and read it in.. */
1128                 swappage = lookup_swap_cache(swap);
1129                 if (!swappage) {
1130                         shmem_swp_unmap(entry);
1131                         /* here we actually do the io */
1132                         if (type && *type == VM_FAULT_MINOR) {
1133                                 __count_vm_event(PGMAJFAULT);
1134                                 *type = VM_FAULT_MAJOR;
1135                         }
1136                         spin_unlock(&info->lock);
1137                         swappage = shmem_swapin(info, swap, idx);
1138                         if (!swappage) {
1139                                 spin_lock(&info->lock);
1140                                 entry = shmem_swp_alloc(info, idx, sgp);
1141                                 if (IS_ERR(entry))
1142                                         error = PTR_ERR(entry);
1143                                 else {
1144                                         if (entry->val == swap.val)
1145                                                 error = -ENOMEM;
1146                                         shmem_swp_unmap(entry);
1147                                 }
1148                                 spin_unlock(&info->lock);
1149                                 if (error)
1150                                         goto failed;
1151                                 goto repeat;
1152                         }
1153                         wait_on_page_locked(swappage);
1154                         page_cache_release(swappage);
1155                         goto repeat;
1156                 }
1157
1158                 /* We have to do this with page locked to prevent races */
1159                 if (TestSetPageLocked(swappage)) {
1160                         shmem_swp_unmap(entry);
1161                         spin_unlock(&info->lock);
1162                         wait_on_page_locked(swappage);
1163                         page_cache_release(swappage);
1164                         goto repeat;
1165                 }
1166                 if (PageWriteback(swappage)) {
1167                         shmem_swp_unmap(entry);
1168                         spin_unlock(&info->lock);
1169                         wait_on_page_writeback(swappage);
1170                         unlock_page(swappage);
1171                         page_cache_release(swappage);
1172                         goto repeat;
1173                 }
1174                 if (!PageUptodate(swappage)) {
1175                         shmem_swp_unmap(entry);
1176                         spin_unlock(&info->lock);
1177                         unlock_page(swappage);
1178                         page_cache_release(swappage);
1179                         error = -EIO;
1180                         goto failed;
1181                 }
1182
1183                 if (filepage) {
1184                         shmem_swp_set(info, entry, 0);
1185                         shmem_swp_unmap(entry);
1186                         delete_from_swap_cache(swappage);
1187                         spin_unlock(&info->lock);
1188                         copy_highpage(filepage, swappage);
1189                         unlock_page(swappage);
1190                         page_cache_release(swappage);
1191                         flush_dcache_page(filepage);
1192                         SetPageUptodate(filepage);
1193                         set_page_dirty(filepage);
1194                         swap_free(swap);
1195                 } else if (!(error = move_from_swap_cache(
1196                                 swappage, idx, mapping))) {
1197                         info->flags |= SHMEM_PAGEIN;
1198                         shmem_swp_set(info, entry, 0);
1199                         shmem_swp_unmap(entry);
1200                         spin_unlock(&info->lock);
1201                         filepage = swappage;
1202                         swap_free(swap);
1203                 } else {
1204                         shmem_swp_unmap(entry);
1205                         spin_unlock(&info->lock);
1206                         unlock_page(swappage);
1207                         page_cache_release(swappage);
1208                         if (error == -ENOMEM) {
1209                                 /* let kswapd refresh zone for GFP_ATOMICs */
1210                                 congestion_wait(WRITE, HZ/50);
1211                         }
1212                         goto repeat;
1213                 }
1214         } else if (sgp == SGP_READ && !filepage) {
1215                 shmem_swp_unmap(entry);
1216                 filepage = find_get_page(mapping, idx);
1217                 if (filepage &&
1218                     (!PageUptodate(filepage) || TestSetPageLocked(filepage))) {
1219                         spin_unlock(&info->lock);
1220                         wait_on_page_locked(filepage);
1221                         page_cache_release(filepage);
1222                         filepage = NULL;
1223                         goto repeat;
1224                 }
1225                 spin_unlock(&info->lock);
1226         } else {
1227                 shmem_swp_unmap(entry);
1228                 sbinfo = SHMEM_SB(inode->i_sb);
1229                 if (sbinfo->max_blocks) {
1230                         spin_lock(&sbinfo->stat_lock);
1231                         if (sbinfo->free_blocks == 0 ||
1232                             shmem_acct_block(info->flags)) {
1233                                 spin_unlock(&sbinfo->stat_lock);
1234                                 spin_unlock(&info->lock);
1235                                 error = -ENOSPC;
1236                                 goto failed;
1237                         }
1238                         sbinfo->free_blocks--;
1239                         inode->i_blocks += BLOCKS_PER_PAGE;
1240                         spin_unlock(&sbinfo->stat_lock);
1241                 } else if (shmem_acct_block(info->flags)) {
1242                         spin_unlock(&info->lock);
1243                         error = -ENOSPC;
1244                         goto failed;
1245                 }
1246
1247                 if (!filepage) {
1248                         spin_unlock(&info->lock);
1249                         filepage = shmem_alloc_page(mapping_gfp_mask(mapping),
1250                                                     info,
1251                                                     idx);
1252                         if (!filepage) {
1253                                 shmem_unacct_blocks(info->flags, 1);
1254                                 shmem_free_blocks(inode, 1);
1255                                 error = -ENOMEM;
1256                                 goto failed;
1257                         }
1258
1259                         spin_lock(&info->lock);
1260                         entry = shmem_swp_alloc(info, idx, sgp);
1261                         if (IS_ERR(entry))
1262                                 error = PTR_ERR(entry);
1263                         else {
1264                                 swap = *entry;
1265                                 shmem_swp_unmap(entry);
1266                         }
1267                         if (error || swap.val || 0 != add_to_page_cache_lru(
1268                                         filepage, mapping, idx, GFP_ATOMIC)) {
1269                                 spin_unlock(&info->lock);
1270                                 page_cache_release(filepage);
1271                                 shmem_unacct_blocks(info->flags, 1);
1272                                 shmem_free_blocks(inode, 1);
1273                                 filepage = NULL;
1274                                 if (error)
1275                                         goto failed;
1276                                 goto repeat;
1277                         }
1278                         info->flags |= SHMEM_PAGEIN;
1279                 }
1280
1281                 info->alloced++;
1282                 spin_unlock(&info->lock);
1283                 flush_dcache_page(filepage);
1284                 SetPageUptodate(filepage);
1285         }
1286 done:
1287         if (*pagep != filepage) {
1288                 unlock_page(filepage);
1289                 *pagep = filepage;
1290         }
1291         return 0;
1292
1293 failed:
1294         if (*pagep != filepage) {
1295                 unlock_page(filepage);
1296                 page_cache_release(filepage);
1297         }
1298         return error;
1299 }
1300
1301 static struct page *shmem_nopage(struct vm_area_struct *vma,
1302                                  unsigned long address, int *type)
1303 {
1304         struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1305         struct page *page = NULL;
1306         unsigned long idx;
1307         int error;
1308
1309         idx = (address - vma->vm_start) >> PAGE_SHIFT;
1310         idx += vma->vm_pgoff;
1311         idx >>= PAGE_CACHE_SHIFT - PAGE_SHIFT;
1312         if (((loff_t) idx << PAGE_CACHE_SHIFT) >= i_size_read(inode))
1313                 return NOPAGE_SIGBUS;
1314
1315         error = shmem_getpage(inode, idx, &page, SGP_CACHE, type);
1316         if (error)
1317                 return (error == -ENOMEM)? NOPAGE_OOM: NOPAGE_SIGBUS;
1318
1319         mark_page_accessed(page);
1320         return page;
1321 }
1322
1323 static int shmem_populate(struct vm_area_struct *vma,
1324         unsigned long addr, unsigned long len,
1325         pgprot_t prot, unsigned long pgoff, int nonblock)
1326 {
1327         struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1328         struct mm_struct *mm = vma->vm_mm;
1329         enum sgp_type sgp = nonblock? SGP_QUICK: SGP_CACHE;
1330         unsigned long size;
1331
1332         size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
1333         if (pgoff >= size || pgoff + (len >> PAGE_SHIFT) > size)
1334                 return -EINVAL;
1335
1336         while ((long) len > 0) {
1337                 struct page *page = NULL;
1338                 int err;
1339                 /*
1340                  * Will need changing if PAGE_CACHE_SIZE != PAGE_SIZE
1341                  */
1342                 err = shmem_getpage(inode, pgoff, &page, sgp, NULL);
1343                 if (err)
1344                         return err;
1345                 /* Page may still be null, but only if nonblock was set. */
1346                 if (page) {
1347                         mark_page_accessed(page);
1348                         err = install_page(mm, vma, addr, page, prot);
1349                         if (err) {
1350                                 page_cache_release(page);
1351                                 return err;
1352                         }
1353                 } else if (vma->vm_flags & VM_NONLINEAR) {
1354                         /* No page was found just because we can't read it in
1355                          * now (being here implies nonblock != 0), but the page
1356                          * may exist, so set the PTE to fault it in later. */
1357                         err = install_file_pte(mm, vma, addr, pgoff, prot);
1358                         if (err)
1359                                 return err;
1360                 }
1361
1362                 len -= PAGE_SIZE;
1363                 addr += PAGE_SIZE;
1364                 pgoff++;
1365         }
1366         return 0;
1367 }
1368
1369 #ifdef CONFIG_NUMA
1370 int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *new)
1371 {
1372         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1373         return mpol_set_shared_policy(&SHMEM_I(i)->policy, vma, new);
1374 }
1375
1376 struct mempolicy *
1377 shmem_get_policy(struct vm_area_struct *vma, unsigned long addr)
1378 {
1379         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1380         unsigned long idx;
1381
1382         idx = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1383         return mpol_shared_policy_lookup(&SHMEM_I(i)->policy, idx);
1384 }
1385 #endif
1386
1387 int shmem_lock(struct file *file, int lock, struct user_struct *user)
1388 {
1389         struct inode *inode = file->f_path.dentry->d_inode;
1390         struct shmem_inode_info *info = SHMEM_I(inode);
1391         int retval = -ENOMEM;
1392
1393         spin_lock(&info->lock);
1394         if (lock && !(info->flags & VM_LOCKED)) {
1395                 if (!user_shm_lock(inode->i_size, user))
1396                         goto out_nomem;
1397                 info->flags |= VM_LOCKED;
1398         }
1399         if (!lock && (info->flags & VM_LOCKED) && user) {
1400                 user_shm_unlock(inode->i_size, user);
1401                 info->flags &= ~VM_LOCKED;
1402         }
1403         retval = 0;
1404 out_nomem:
1405         spin_unlock(&info->lock);
1406         return retval;
1407 }
1408
1409 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1410 {
1411         file_accessed(file);
1412         vma->vm_ops = &shmem_vm_ops;
1413         return 0;
1414 }
1415
1416 static struct inode *
1417 shmem_get_inode(struct super_block *sb, int mode, dev_t dev)
1418 {
1419         struct inode *inode;
1420         struct shmem_inode_info *info;
1421         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1422
1423         if (sbinfo->max_inodes) {
1424                 spin_lock(&sbinfo->stat_lock);
1425                 if (!sbinfo->free_inodes) {
1426                         spin_unlock(&sbinfo->stat_lock);
1427                         return NULL;
1428                 }
1429                 sbinfo->free_inodes--;
1430                 spin_unlock(&sbinfo->stat_lock);
1431         }
1432
1433         inode = new_inode(sb);
1434         if (inode) {
1435                 inode->i_mode = mode;
1436                 inode->i_uid = current->fsuid;
1437                 inode->i_gid = current->fsgid;
1438                 inode->i_blocks = 0;
1439                 inode->i_mapping->a_ops = &shmem_aops;
1440                 inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1441                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1442                 inode->i_generation = get_seconds();
1443                 info = SHMEM_I(inode);
1444                 memset(info, 0, (char *)inode - (char *)info);
1445                 spin_lock_init(&info->lock);
1446                 INIT_LIST_HEAD(&info->swaplist);
1447
1448                 switch (mode & S_IFMT) {
1449                 default:
1450                         inode->i_op = &shmem_special_inode_operations;
1451                         init_special_inode(inode, mode, dev);
1452                         break;
1453                 case S_IFREG:
1454                         inode->i_op = &shmem_inode_operations;
1455                         inode->i_fop = &shmem_file_operations;
1456                         mpol_shared_policy_init(&info->policy, sbinfo->policy,
1457                                                         &sbinfo->policy_nodes);
1458                         break;
1459                 case S_IFDIR:
1460                         inc_nlink(inode);
1461                         /* Some things misbehave if size == 0 on a directory */
1462                         inode->i_size = 2 * BOGO_DIRENT_SIZE;
1463                         inode->i_op = &shmem_dir_inode_operations;
1464                         inode->i_fop = &simple_dir_operations;
1465                         break;
1466                 case S_IFLNK:
1467                         /*
1468                          * Must not load anything in the rbtree,
1469                          * mpol_free_shared_policy will not be called.
1470                          */
1471                         mpol_shared_policy_init(&info->policy, MPOL_DEFAULT,
1472                                                 NULL);
1473                         break;
1474                 }
1475         } else if (sbinfo->max_inodes) {
1476                 spin_lock(&sbinfo->stat_lock);
1477                 sbinfo->free_inodes++;
1478                 spin_unlock(&sbinfo->stat_lock);
1479         }
1480         return inode;
1481 }
1482
1483 #ifdef CONFIG_TMPFS
1484 static const struct inode_operations shmem_symlink_inode_operations;
1485 static const struct inode_operations shmem_symlink_inline_operations;
1486
1487 /*
1488  * Normally tmpfs makes no use of shmem_prepare_write, but it
1489  * lets a tmpfs file be used read-write below the loop driver.
1490  */
1491 static int
1492 shmem_prepare_write(struct file *file, struct page *page, unsigned offset, unsigned to)
1493 {
1494         struct inode *inode = page->mapping->host;
1495         return shmem_getpage(inode, page->index, &page, SGP_WRITE, NULL);
1496 }
1497
1498 static ssize_t
1499 shmem_file_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
1500 {
1501         struct inode    *inode = file->f_path.dentry->d_inode;
1502         loff_t          pos;
1503         unsigned long   written;
1504         ssize_t         err;
1505
1506         if ((ssize_t) count < 0)
1507                 return -EINVAL;
1508
1509         if (!access_ok(VERIFY_READ, buf, count))
1510                 return -EFAULT;
1511
1512         mutex_lock(&inode->i_mutex);
1513
1514         pos = *ppos;
1515         written = 0;
1516
1517         err = generic_write_checks(file, &pos, &count, 0);
1518         if (err || !count)
1519                 goto out;
1520
1521         err = remove_suid(file->f_path.dentry);
1522         if (err)
1523                 goto out;
1524
1525         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
1526
1527         do {
1528                 struct page *page = NULL;
1529                 unsigned long bytes, index, offset;
1530                 char *kaddr;
1531                 int left;
1532
1533                 offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
1534                 index = pos >> PAGE_CACHE_SHIFT;
1535                 bytes = PAGE_CACHE_SIZE - offset;
1536                 if (bytes > count)
1537                         bytes = count;
1538
1539                 /*
1540                  * We don't hold page lock across copy from user -
1541                  * what would it guard against? - so no deadlock here.
1542                  * But it still may be a good idea to prefault below.
1543                  */
1544
1545                 err = shmem_getpage(inode, index, &page, SGP_WRITE, NULL);
1546                 if (err)
1547                         break;
1548
1549                 left = bytes;
1550                 if (PageHighMem(page)) {
1551                         volatile unsigned char dummy;
1552                         __get_user(dummy, buf);
1553                         __get_user(dummy, buf + bytes - 1);
1554
1555                         kaddr = kmap_atomic(page, KM_USER0);
1556                         left = __copy_from_user_inatomic(kaddr + offset,
1557                                                         buf, bytes);
1558                         kunmap_atomic(kaddr, KM_USER0);
1559                 }
1560                 if (left) {
1561                         kaddr = kmap(page);
1562                         left = __copy_from_user(kaddr + offset, buf, bytes);
1563                         kunmap(page);
1564                 }
1565
1566                 written += bytes;
1567                 count -= bytes;
1568                 pos += bytes;
1569                 buf += bytes;
1570                 if (pos > inode->i_size)
1571                         i_size_write(inode, pos);
1572
1573                 flush_dcache_page(page);
1574                 set_page_dirty(page);
1575                 mark_page_accessed(page);
1576                 page_cache_release(page);
1577
1578                 if (left) {
1579                         pos -= left;
1580                         written -= left;
1581                         err = -EFAULT;
1582                         break;
1583                 }
1584
1585                 /*
1586                  * Our dirty pages are not counted in nr_dirty,
1587                  * and we do not attempt to balance dirty pages.
1588                  */
1589
1590                 cond_resched();
1591         } while (count);
1592
1593         *ppos = pos;
1594         if (written)
1595                 err = written;
1596 out:
1597         mutex_unlock(&inode->i_mutex);
1598         return err;
1599 }
1600
1601 static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
1602 {
1603         struct inode *inode = filp->f_path.dentry->d_inode;
1604         struct address_space *mapping = inode->i_mapping;
1605         unsigned long index, offset;
1606
1607         index = *ppos >> PAGE_CACHE_SHIFT;
1608         offset = *ppos & ~PAGE_CACHE_MASK;
1609
1610         for (;;) {
1611                 struct page *page = NULL;
1612                 unsigned long end_index, nr, ret;
1613                 loff_t i_size = i_size_read(inode);
1614
1615                 end_index = i_size >> PAGE_CACHE_SHIFT;
1616                 if (index > end_index)
1617                         break;
1618                 if (index == end_index) {
1619                         nr = i_size & ~PAGE_CACHE_MASK;
1620                         if (nr <= offset)
1621                                 break;
1622                 }
1623
1624                 desc->error = shmem_getpage(inode, index, &page, SGP_READ, NULL);
1625                 if (desc->error) {
1626                         if (desc->error == -EINVAL)
1627                                 desc->error = 0;
1628                         break;
1629                 }
1630
1631                 /*
1632                  * We must evaluate after, since reads (unlike writes)
1633                  * are called without i_mutex protection against truncate
1634                  */
1635                 nr = PAGE_CACHE_SIZE;
1636                 i_size = i_size_read(inode);
1637                 end_index = i_size >> PAGE_CACHE_SHIFT;
1638                 if (index == end_index) {
1639                         nr = i_size & ~PAGE_CACHE_MASK;
1640                         if (nr <= offset) {
1641                                 if (page)
1642                                         page_cache_release(page);
1643                                 break;
1644                         }
1645                 }
1646                 nr -= offset;
1647
1648                 if (page) {
1649                         /*
1650                          * If users can be writing to this page using arbitrary
1651                          * virtual addresses, take care about potential aliasing
1652                          * before reading the page on the kernel side.
1653                          */
1654                         if (mapping_writably_mapped(mapping))
1655                                 flush_dcache_page(page);
1656                         /*
1657                          * Mark the page accessed if we read the beginning.
1658                          */
1659                         if (!offset)
1660                                 mark_page_accessed(page);
1661                 } else {
1662                         page = ZERO_PAGE(0);
1663                         page_cache_get(page);
1664                 }
1665
1666                 /*
1667                  * Ok, we have the page, and it's up-to-date, so
1668                  * now we can copy it to user space...
1669                  *
1670                  * The actor routine returns how many bytes were actually used..
1671                  * NOTE! This may not be the same as how much of a user buffer
1672                  * we filled up (we may be padding etc), so we can only update
1673                  * "pos" here (the actor routine has to update the user buffer
1674                  * pointers and the remaining count).
1675                  */
1676                 ret = actor(desc, page, offset, nr);
1677                 offset += ret;
1678                 index += offset >> PAGE_CACHE_SHIFT;
1679                 offset &= ~PAGE_CACHE_MASK;
1680
1681                 page_cache_release(page);
1682                 if (ret != nr || !desc->count)
1683                         break;
1684
1685                 cond_resched();
1686         }
1687
1688         *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1689         file_accessed(filp);
1690 }
1691
1692 static ssize_t shmem_file_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
1693 {
1694         read_descriptor_t desc;
1695
1696         if ((ssize_t) count < 0)
1697                 return -EINVAL;
1698         if (!access_ok(VERIFY_WRITE, buf, count))
1699                 return -EFAULT;
1700         if (!count)
1701                 return 0;
1702
1703         desc.written = 0;
1704         desc.count = count;
1705         desc.arg.buf = buf;
1706         desc.error = 0;
1707
1708         do_shmem_file_read(filp, ppos, &desc, file_read_actor);
1709         if (desc.written)
1710                 return desc.written;
1711         return desc.error;
1712 }
1713
1714 static ssize_t shmem_file_sendfile(struct file *in_file, loff_t *ppos,
1715                          size_t count, read_actor_t actor, void *target)
1716 {
1717         read_descriptor_t desc;
1718
1719         if (!count)
1720                 return 0;
1721
1722         desc.written = 0;
1723         desc.count = count;
1724         desc.arg.data = target;
1725         desc.error = 0;
1726
1727         do_shmem_file_read(in_file, ppos, &desc, actor);
1728         if (desc.written)
1729                 return desc.written;
1730         return desc.error;
1731 }
1732
1733 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
1734 {
1735         struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
1736
1737         buf->f_type = TMPFS_MAGIC;
1738         buf->f_bsize = PAGE_CACHE_SIZE;
1739         buf->f_namelen = NAME_MAX;
1740         spin_lock(&sbinfo->stat_lock);
1741         if (sbinfo->max_blocks) {
1742                 buf->f_blocks = sbinfo->max_blocks;
1743                 buf->f_bavail = buf->f_bfree = sbinfo->free_blocks;
1744         }
1745         if (sbinfo->max_inodes) {
1746                 buf->f_files = sbinfo->max_inodes;
1747                 buf->f_ffree = sbinfo->free_inodes;
1748         }
1749         /* else leave those fields 0 like simple_statfs */
1750         spin_unlock(&sbinfo->stat_lock);
1751         return 0;
1752 }
1753
1754 /*
1755  * File creation. Allocate an inode, and we're done..
1756  */
1757 static int
1758 shmem_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
1759 {
1760         struct inode *inode = shmem_get_inode(dir->i_sb, mode, dev);
1761         int error = -ENOSPC;
1762
1763         if (inode) {
1764                 error = security_inode_init_security(inode, dir, NULL, NULL,
1765                                                      NULL);
1766                 if (error) {
1767                         if (error != -EOPNOTSUPP) {
1768                                 iput(inode);
1769                                 return error;
1770                         }
1771                 }
1772                 error = shmem_acl_init(inode, dir);
1773                 if (error) {
1774                         iput(inode);
1775                         return error;
1776                 }
1777                 if (dir->i_mode & S_ISGID) {
1778                         inode->i_gid = dir->i_gid;
1779                         if (S_ISDIR(mode))
1780                                 inode->i_mode |= S_ISGID;
1781                 }
1782                 dir->i_size += BOGO_DIRENT_SIZE;
1783                 dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1784                 d_instantiate(dentry, inode);
1785                 dget(dentry); /* Extra count - pin the dentry in core */
1786         }
1787         return error;
1788 }
1789
1790 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, int mode)
1791 {
1792         int error;
1793
1794         if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
1795                 return error;
1796         inc_nlink(dir);
1797         return 0;
1798 }
1799
1800 static int shmem_create(struct inode *dir, struct dentry *dentry, int mode,
1801                 struct nameidata *nd)
1802 {
1803         return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
1804 }
1805
1806 /*
1807  * Link a file..
1808  */
1809 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
1810 {
1811         struct inode *inode = old_dentry->d_inode;
1812         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1813
1814         /*
1815          * No ordinary (disk based) filesystem counts links as inodes;
1816          * but each new link needs a new dentry, pinning lowmem, and
1817          * tmpfs dentries cannot be pruned until they are unlinked.
1818          */
1819         if (sbinfo->max_inodes) {
1820                 spin_lock(&sbinfo->stat_lock);
1821                 if (!sbinfo->free_inodes) {
1822                         spin_unlock(&sbinfo->stat_lock);
1823                         return -ENOSPC;
1824                 }
1825                 sbinfo->free_inodes--;
1826                 spin_unlock(&sbinfo->stat_lock);
1827         }
1828
1829         dir->i_size += BOGO_DIRENT_SIZE;
1830         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1831         inc_nlink(inode);
1832         atomic_inc(&inode->i_count);    /* New dentry reference */
1833         dget(dentry);           /* Extra pinning count for the created dentry */
1834         d_instantiate(dentry, inode);
1835         return 0;
1836 }
1837
1838 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
1839 {
1840         struct inode *inode = dentry->d_inode;
1841
1842         if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode)) {
1843                 struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1844                 if (sbinfo->max_inodes) {
1845                         spin_lock(&sbinfo->stat_lock);
1846                         sbinfo->free_inodes++;
1847                         spin_unlock(&sbinfo->stat_lock);
1848                 }
1849         }
1850
1851         dir->i_size -= BOGO_DIRENT_SIZE;
1852         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1853         drop_nlink(inode);
1854         dput(dentry);   /* Undo the count from "create" - this does all the work */
1855         return 0;
1856 }
1857
1858 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
1859 {
1860         if (!simple_empty(dentry))
1861                 return -ENOTEMPTY;
1862
1863         drop_nlink(dentry->d_inode);
1864         drop_nlink(dir);
1865         return shmem_unlink(dir, dentry);
1866 }
1867
1868 /*
1869  * The VFS layer already does all the dentry stuff for rename,
1870  * we just have to decrement the usage count for the target if
1871  * it exists so that the VFS layer correctly free's it when it
1872  * gets overwritten.
1873  */
1874 static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
1875 {
1876         struct inode *inode = old_dentry->d_inode;
1877         int they_are_dirs = S_ISDIR(inode->i_mode);
1878
1879         if (!simple_empty(new_dentry))
1880                 return -ENOTEMPTY;
1881
1882         if (new_dentry->d_inode) {
1883                 (void) shmem_unlink(new_dir, new_dentry);
1884                 if (they_are_dirs)
1885                         drop_nlink(old_dir);
1886         } else if (they_are_dirs) {
1887                 drop_nlink(old_dir);
1888                 inc_nlink(new_dir);
1889         }
1890
1891         old_dir->i_size -= BOGO_DIRENT_SIZE;
1892         new_dir->i_size += BOGO_DIRENT_SIZE;
1893         old_dir->i_ctime = old_dir->i_mtime =
1894         new_dir->i_ctime = new_dir->i_mtime =
1895         inode->i_ctime = CURRENT_TIME;
1896         return 0;
1897 }
1898
1899 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
1900 {
1901         int error;
1902         int len;
1903         struct inode *inode;
1904         struct page *page = NULL;
1905         char *kaddr;
1906         struct shmem_inode_info *info;
1907
1908         len = strlen(symname) + 1;
1909         if (len > PAGE_CACHE_SIZE)
1910                 return -ENAMETOOLONG;
1911
1912         inode = shmem_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0);
1913         if (!inode)
1914                 return -ENOSPC;
1915
1916         error = security_inode_init_security(inode, dir, NULL, NULL,
1917                                              NULL);
1918         if (error) {
1919                 if (error != -EOPNOTSUPP) {
1920                         iput(inode);
1921                         return error;
1922                 }
1923                 error = 0;
1924         }
1925
1926         info = SHMEM_I(inode);
1927         inode->i_size = len-1;
1928         if (len <= (char *)inode - (char *)info) {
1929                 /* do it inline */
1930                 memcpy(info, symname, len);
1931                 inode->i_op = &shmem_symlink_inline_operations;
1932         } else {
1933                 error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
1934                 if (error) {
1935                         iput(inode);
1936                         return error;
1937                 }
1938                 inode->i_op = &shmem_symlink_inode_operations;
1939                 kaddr = kmap_atomic(page, KM_USER0);
1940                 memcpy(kaddr, symname, len);
1941                 kunmap_atomic(kaddr, KM_USER0);
1942                 set_page_dirty(page);
1943                 page_cache_release(page);
1944         }
1945         if (dir->i_mode & S_ISGID)
1946                 inode->i_gid = dir->i_gid;
1947         dir->i_size += BOGO_DIRENT_SIZE;
1948         dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1949         d_instantiate(dentry, inode);
1950         dget(dentry);
1951         return 0;
1952 }
1953
1954 static void *shmem_follow_link_inline(struct dentry *dentry, struct nameidata *nd)
1955 {
1956         nd_set_link(nd, (char *)SHMEM_I(dentry->d_inode));
1957         return NULL;
1958 }
1959
1960 static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
1961 {
1962         struct page *page = NULL;
1963         int res = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
1964         nd_set_link(nd, res ? ERR_PTR(res) : kmap(page));
1965         return page;
1966 }
1967
1968 static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
1969 {
1970         if (!IS_ERR(nd_get_link(nd))) {
1971                 struct page *page = cookie;
1972                 kunmap(page);
1973                 mark_page_accessed(page);
1974                 page_cache_release(page);
1975         }
1976 }
1977
1978 static const struct inode_operations shmem_symlink_inline_operations = {
1979         .readlink       = generic_readlink,
1980         .follow_link    = shmem_follow_link_inline,
1981 };
1982
1983 static const struct inode_operations shmem_symlink_inode_operations = {
1984         .truncate       = shmem_truncate,
1985         .readlink       = generic_readlink,
1986         .follow_link    = shmem_follow_link,
1987         .put_link       = shmem_put_link,
1988 };
1989
1990 #ifdef CONFIG_TMPFS_POSIX_ACL
1991 /**
1992  * Superblocks without xattr inode operations will get security.* xattr
1993  * support from the VFS "for free". As soon as we have any other xattrs
1994  * like ACLs, we also need to implement the security.* handlers at
1995  * filesystem level, though.
1996  */
1997
1998 static size_t shmem_xattr_security_list(struct inode *inode, char *list,
1999                                         size_t list_len, const char *name,
2000                                         size_t name_len)
2001 {
2002         return security_inode_listsecurity(inode, list, list_len);
2003 }
2004
2005 static int shmem_xattr_security_get(struct inode *inode, const char *name,
2006                                     void *buffer, size_t size)
2007 {
2008         if (strcmp(name, "") == 0)
2009                 return -EINVAL;
2010         return security_inode_getsecurity(inode, name, buffer, size,
2011                                           -EOPNOTSUPP);
2012 }
2013
2014 static int shmem_xattr_security_set(struct inode *inode, const char *name,
2015                                     const void *value, size_t size, int flags)
2016 {
2017         if (strcmp(name, "") == 0)
2018                 return -EINVAL;
2019         return security_inode_setsecurity(inode, name, value, size, flags);
2020 }
2021
2022 static struct xattr_handler shmem_xattr_security_handler = {
2023         .prefix = XATTR_SECURITY_PREFIX,
2024         .list   = shmem_xattr_security_list,
2025         .get    = shmem_xattr_security_get,
2026         .set    = shmem_xattr_security_set,
2027 };
2028
2029 static struct xattr_handler *shmem_xattr_handlers[] = {
2030         &shmem_xattr_acl_access_handler,
2031         &shmem_xattr_acl_default_handler,
2032         &shmem_xattr_security_handler,
2033         NULL
2034 };
2035 #endif
2036
2037 static struct dentry *shmem_get_parent(struct dentry *child)
2038 {
2039         return ERR_PTR(-ESTALE);
2040 }
2041
2042 static int shmem_match(struct inode *ino, void *vfh)
2043 {
2044         __u32 *fh = vfh;
2045         __u64 inum = fh[2];
2046         inum = (inum << 32) | fh[1];
2047         return ino->i_ino == inum && fh[0] == ino->i_generation;
2048 }
2049
2050 static struct dentry *shmem_get_dentry(struct super_block *sb, void *vfh)
2051 {
2052         struct dentry *de = NULL;
2053         struct inode *inode;
2054         __u32 *fh = vfh;
2055         __u64 inum = fh[2];
2056         inum = (inum << 32) | fh[1];
2057
2058         inode = ilookup5(sb, (unsigned long)(inum+fh[0]), shmem_match, vfh);
2059         if (inode) {
2060                 de = d_find_alias(inode);
2061                 iput(inode);
2062         }
2063
2064         return de? de: ERR_PTR(-ESTALE);
2065 }
2066
2067 static struct dentry *shmem_decode_fh(struct super_block *sb, __u32 *fh,
2068                 int len, int type,
2069                 int (*acceptable)(void *context, struct dentry *de),
2070                 void *context)
2071 {
2072         if (len < 3)
2073                 return ERR_PTR(-ESTALE);
2074
2075         return sb->s_export_op->find_exported_dentry(sb, fh, NULL, acceptable,
2076                                                         context);
2077 }
2078
2079 static int shmem_encode_fh(struct dentry *dentry, __u32 *fh, int *len,
2080                                 int connectable)
2081 {
2082         struct inode *inode = dentry->d_inode;
2083
2084         if (*len < 3)
2085                 return 255;
2086
2087         if (hlist_unhashed(&inode->i_hash)) {
2088                 /* Unfortunately insert_inode_hash is not idempotent,
2089                  * so as we hash inodes here rather than at creation
2090                  * time, we need a lock to ensure we only try
2091                  * to do it once
2092                  */
2093                 static DEFINE_SPINLOCK(lock);
2094                 spin_lock(&lock);
2095                 if (hlist_unhashed(&inode->i_hash))
2096                         __insert_inode_hash(inode,
2097                                             inode->i_ino + inode->i_generation);
2098                 spin_unlock(&lock);
2099         }
2100
2101         fh[0] = inode->i_generation;
2102         fh[1] = inode->i_ino;
2103         fh[2] = ((__u64)inode->i_ino) >> 32;
2104
2105         *len = 3;
2106         return 1;
2107 }
2108
2109 static struct export_operations shmem_export_ops = {
2110         .get_parent     = shmem_get_parent,
2111         .get_dentry     = shmem_get_dentry,
2112         .encode_fh      = shmem_encode_fh,
2113         .decode_fh      = shmem_decode_fh,
2114 };
2115
2116 static int shmem_parse_options(char *options, int *mode, uid_t *uid,
2117         gid_t *gid, unsigned long *blocks, unsigned long *inodes,
2118         int *policy, nodemask_t *policy_nodes)
2119 {
2120         char *this_char, *value, *rest;
2121
2122         while (options != NULL) {
2123                 this_char = options;
2124                 for (;;) {
2125                         /*
2126                          * NUL-terminate this option: unfortunately,
2127                          * mount options form a comma-separated list,
2128                          * but mpol's nodelist may also contain commas.
2129                          */
2130                         options = strchr(options, ',');
2131                         if (options == NULL)
2132                                 break;
2133                         options++;
2134                         if (!isdigit(*options)) {
2135                                 options[-1] = '\0';
2136                                 break;
2137                         }
2138                 }
2139                 if (!*this_char)
2140                         continue;
2141                 if ((value = strchr(this_char,'=')) != NULL) {
2142                         *value++ = 0;
2143                 } else {
2144                         printk(KERN_ERR
2145                             "tmpfs: No value for mount option '%s'\n",
2146                             this_char);
2147                         return 1;
2148                 }
2149
2150                 if (!strcmp(this_char,"size")) {
2151                         unsigned long long size;
2152                         size = memparse(value,&rest);
2153                         if (*rest == '%') {
2154                                 size <<= PAGE_SHIFT;
2155                                 size *= totalram_pages;
2156                                 do_div(size, 100);
2157                                 rest++;
2158                         }
2159                         if (*rest)
2160                                 goto bad_val;
2161                         *blocks = size >> PAGE_CACHE_SHIFT;
2162                 } else if (!strcmp(this_char,"nr_blocks")) {
2163                         *blocks = memparse(value,&rest);
2164                         if (*rest)
2165                                 goto bad_val;
2166                 } else if (!strcmp(this_char,"nr_inodes")) {
2167                         *inodes = memparse(value,&rest);
2168                         if (*rest)
2169                                 goto bad_val;
2170                 } else if (!strcmp(this_char,"mode")) {
2171                         if (!mode)
2172                                 continue;
2173                         *mode = simple_strtoul(value,&rest,8);
2174                         if (*rest)
2175                                 goto bad_val;
2176                 } else if (!strcmp(this_char,"uid")) {
2177                         if (!uid)
2178                                 continue;
2179                         *uid = simple_strtoul(value,&rest,0);
2180                         if (*rest)
2181                                 goto bad_val;
2182                 } else if (!strcmp(this_char,"gid")) {
2183                         if (!gid)
2184                                 continue;
2185                         *gid = simple_strtoul(value,&rest,0);
2186                         if (*rest)
2187                                 goto bad_val;
2188                 } else if (!strcmp(this_char,"mpol")) {
2189                         if (shmem_parse_mpol(value,policy,policy_nodes))
2190                                 goto bad_val;
2191                 } else {
2192                         printk(KERN_ERR "tmpfs: Bad mount option %s\n",
2193                                this_char);
2194                         return 1;
2195                 }
2196         }
2197         return 0;
2198
2199 bad_val:
2200         printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
2201                value, this_char);
2202         return 1;
2203
2204 }
2205
2206 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2207 {
2208         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2209         unsigned long max_blocks = sbinfo->max_blocks;
2210         unsigned long max_inodes = sbinfo->max_inodes;
2211         int policy = sbinfo->policy;
2212         nodemask_t policy_nodes = sbinfo->policy_nodes;
2213         unsigned long blocks;
2214         unsigned long inodes;
2215         int error = -EINVAL;
2216
2217         if (shmem_parse_options(data, NULL, NULL, NULL, &max_blocks,
2218                                 &max_inodes, &policy, &policy_nodes))
2219                 return error;
2220
2221         spin_lock(&sbinfo->stat_lock);
2222         blocks = sbinfo->max_blocks - sbinfo->free_blocks;
2223         inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2224         if (max_blocks < blocks)
2225                 goto out;
2226         if (max_inodes < inodes)
2227                 goto out;
2228         /*
2229          * Those tests also disallow limited->unlimited while any are in
2230          * use, so i_blocks will always be zero when max_blocks is zero;
2231          * but we must separately disallow unlimited->limited, because
2232          * in that case we have no record of how much is already in use.
2233          */
2234         if (max_blocks && !sbinfo->max_blocks)
2235                 goto out;
2236         if (max_inodes && !sbinfo->max_inodes)
2237                 goto out;
2238
2239         error = 0;
2240         sbinfo->max_blocks  = max_blocks;
2241         sbinfo->free_blocks = max_blocks - blocks;
2242         sbinfo->max_inodes  = max_inodes;
2243         sbinfo->free_inodes = max_inodes - inodes;
2244         sbinfo->policy = policy;
2245         sbinfo->policy_nodes = policy_nodes;
2246 out:
2247         spin_unlock(&sbinfo->stat_lock);
2248         return error;
2249 }
2250 #endif
2251
2252 static void shmem_put_super(struct super_block *sb)
2253 {
2254         kfree(sb->s_fs_info);
2255         sb->s_fs_info = NULL;
2256 }
2257
2258 static int shmem_fill_super(struct super_block *sb,
2259                             void *data, int silent)
2260 {
2261         struct inode *inode;
2262         struct dentry *root;
2263         int mode   = S_IRWXUGO | S_ISVTX;
2264         uid_t uid = current->fsuid;
2265         gid_t gid = current->fsgid;
2266         int err = -ENOMEM;
2267         struct shmem_sb_info *sbinfo;
2268         unsigned long blocks = 0;
2269         unsigned long inodes = 0;
2270         int policy = MPOL_DEFAULT;
2271         nodemask_t policy_nodes = node_online_map;
2272
2273 #ifdef CONFIG_TMPFS
2274         /*
2275          * Per default we only allow half of the physical ram per
2276          * tmpfs instance, limiting inodes to one per page of lowmem;
2277          * but the internal instance is left unlimited.
2278          */
2279         if (!(sb->s_flags & MS_NOUSER)) {
2280                 blocks = totalram_pages / 2;
2281                 inodes = totalram_pages - totalhigh_pages;
2282                 if (inodes > blocks)
2283                         inodes = blocks;
2284                 if (shmem_parse_options(data, &mode, &uid, &gid, &blocks,
2285                                         &inodes, &policy, &policy_nodes))
2286                         return -EINVAL;
2287         }
2288         sb->s_export_op = &shmem_export_ops;
2289 #else
2290         sb->s_flags |= MS_NOUSER;
2291 #endif
2292
2293         /* Round up to L1_CACHE_BYTES to resist false sharing */
2294         sbinfo = kmalloc(max((int)sizeof(struct shmem_sb_info),
2295                                 L1_CACHE_BYTES), GFP_KERNEL);
2296         if (!sbinfo)
2297                 return -ENOMEM;
2298
2299         spin_lock_init(&sbinfo->stat_lock);
2300         sbinfo->max_blocks = blocks;
2301         sbinfo->free_blocks = blocks;
2302         sbinfo->max_inodes = inodes;
2303         sbinfo->free_inodes = inodes;
2304         sbinfo->policy = policy;
2305         sbinfo->policy_nodes = policy_nodes;
2306
2307         sb->s_fs_info = sbinfo;
2308         sb->s_maxbytes = SHMEM_MAX_BYTES;
2309         sb->s_blocksize = PAGE_CACHE_SIZE;
2310         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
2311         sb->s_magic = TMPFS_MAGIC;
2312         sb->s_op = &shmem_ops;
2313         sb->s_time_gran = 1;
2314 #ifdef CONFIG_TMPFS_POSIX_ACL
2315         sb->s_xattr = shmem_xattr_handlers;
2316         sb->s_flags |= MS_POSIXACL;
2317 #endif
2318
2319         inode = shmem_get_inode(sb, S_IFDIR | mode, 0);
2320         if (!inode)
2321                 goto failed;
2322         inode->i_uid = uid;
2323         inode->i_gid = gid;
2324         root = d_alloc_root(inode);
2325         if (!root)
2326                 goto failed_iput;
2327         sb->s_root = root;
2328         return 0;
2329
2330 failed_iput:
2331         iput(inode);
2332 failed:
2333         shmem_put_super(sb);
2334         return err;
2335 }
2336
2337 static struct kmem_cache *shmem_inode_cachep;
2338
2339 static struct inode *shmem_alloc_inode(struct super_block *sb)
2340 {
2341         struct shmem_inode_info *p;
2342         p = (struct shmem_inode_info *)kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
2343         if (!p)
2344                 return NULL;
2345         return &p->vfs_inode;
2346 }
2347
2348 static void shmem_destroy_inode(struct inode *inode)
2349 {
2350         if ((inode->i_mode & S_IFMT) == S_IFREG) {
2351                 /* only struct inode is valid if it's an inline symlink */
2352                 mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2353         }
2354         shmem_acl_destroy_inode(inode);
2355         kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2356 }
2357
2358 static void init_once(void *foo, struct kmem_cache *cachep,
2359                       unsigned long flags)
2360 {
2361         struct shmem_inode_info *p = (struct shmem_inode_info *) foo;
2362
2363         inode_init_once(&p->vfs_inode);
2364 #ifdef CONFIG_TMPFS_POSIX_ACL
2365         p->i_acl = NULL;
2366         p->i_default_acl = NULL;
2367 #endif
2368 }
2369
2370 static int init_inodecache(void)
2371 {
2372         shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
2373                                 sizeof(struct shmem_inode_info),
2374                                 0, 0, init_once, NULL);
2375         if (shmem_inode_cachep == NULL)
2376                 return -ENOMEM;
2377         return 0;
2378 }
2379
2380 static void destroy_inodecache(void)
2381 {
2382         kmem_cache_destroy(shmem_inode_cachep);
2383 }
2384
2385 static const struct address_space_operations shmem_aops = {
2386         .writepage      = shmem_writepage,
2387         .set_page_dirty = __set_page_dirty_no_writeback,
2388 #ifdef CONFIG_TMPFS
2389         .prepare_write  = shmem_prepare_write,
2390         .commit_write   = simple_commit_write,
2391 #endif
2392         .migratepage    = migrate_page,
2393 };
2394
2395 static const struct file_operations shmem_file_operations = {
2396         .mmap           = shmem_mmap,
2397 #ifdef CONFIG_TMPFS
2398         .llseek         = generic_file_llseek,
2399         .read           = shmem_file_read,
2400         .write          = shmem_file_write,
2401         .fsync          = simple_sync_file,
2402         .sendfile       = shmem_file_sendfile,
2403 #endif
2404 };
2405
2406 static const struct inode_operations shmem_inode_operations = {
2407         .truncate       = shmem_truncate,
2408         .setattr        = shmem_notify_change,
2409         .truncate_range = shmem_truncate_range,
2410 #ifdef CONFIG_TMPFS_POSIX_ACL
2411         .setxattr       = generic_setxattr,
2412         .getxattr       = generic_getxattr,
2413         .listxattr      = generic_listxattr,
2414         .removexattr    = generic_removexattr,
2415         .permission     = shmem_permission,
2416 #endif
2417
2418 };
2419
2420 static const struct inode_operations shmem_dir_inode_operations = {
2421 #ifdef CONFIG_TMPFS
2422         .create         = shmem_create,
2423         .lookup         = simple_lookup,
2424         .link           = shmem_link,
2425         .unlink         = shmem_unlink,
2426         .symlink        = shmem_symlink,
2427         .mkdir          = shmem_mkdir,
2428         .rmdir          = shmem_rmdir,
2429         .mknod          = shmem_mknod,
2430         .rename         = shmem_rename,
2431 #endif
2432 #ifdef CONFIG_TMPFS_POSIX_ACL
2433         .setattr        = shmem_notify_change,
2434         .setxattr       = generic_setxattr,
2435         .getxattr       = generic_getxattr,
2436         .listxattr      = generic_listxattr,
2437         .removexattr    = generic_removexattr,
2438         .permission     = shmem_permission,
2439 #endif
2440 };
2441
2442 static const struct inode_operations shmem_special_inode_operations = {
2443 #ifdef CONFIG_TMPFS_POSIX_ACL
2444         .setattr        = shmem_notify_change,
2445         .setxattr       = generic_setxattr,
2446         .getxattr       = generic_getxattr,
2447         .listxattr      = generic_listxattr,
2448         .removexattr    = generic_removexattr,
2449         .permission     = shmem_permission,
2450 #endif
2451 };
2452
2453 static const struct super_operations shmem_ops = {
2454         .alloc_inode    = shmem_alloc_inode,
2455         .destroy_inode  = shmem_destroy_inode,
2456 #ifdef CONFIG_TMPFS
2457         .statfs         = shmem_statfs,
2458         .remount_fs     = shmem_remount_fs,
2459 #endif
2460         .delete_inode   = shmem_delete_inode,
2461         .drop_inode     = generic_delete_inode,
2462         .put_super      = shmem_put_super,
2463 };
2464
2465 static struct vm_operations_struct shmem_vm_ops = {
2466         .nopage         = shmem_nopage,
2467         .populate       = shmem_populate,
2468 #ifdef CONFIG_NUMA
2469         .set_policy     = shmem_set_policy,
2470         .get_policy     = shmem_get_policy,
2471 #endif
2472 };
2473
2474
2475 static int shmem_get_sb(struct file_system_type *fs_type,
2476         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
2477 {
2478         return get_sb_nodev(fs_type, flags, data, shmem_fill_super, mnt);
2479 }
2480
2481 static struct file_system_type tmpfs_fs_type = {
2482         .owner          = THIS_MODULE,
2483         .name           = "tmpfs",
2484         .get_sb         = shmem_get_sb,
2485         .kill_sb        = kill_litter_super,
2486 };
2487 static struct vfsmount *shm_mnt;
2488
2489 static int __init init_tmpfs(void)
2490 {
2491         int error;
2492
2493         error = init_inodecache();
2494         if (error)
2495                 goto out3;
2496
2497         error = register_filesystem(&tmpfs_fs_type);
2498         if (error) {
2499                 printk(KERN_ERR "Could not register tmpfs\n");
2500                 goto out2;
2501         }
2502
2503         shm_mnt = vfs_kern_mount(&tmpfs_fs_type, MS_NOUSER,
2504                                 tmpfs_fs_type.name, NULL);
2505         if (IS_ERR(shm_mnt)) {
2506                 error = PTR_ERR(shm_mnt);
2507                 printk(KERN_ERR "Could not kern_mount tmpfs\n");
2508                 goto out1;
2509         }
2510         return 0;
2511
2512 out1:
2513         unregister_filesystem(&tmpfs_fs_type);
2514 out2:
2515         destroy_inodecache();
2516 out3:
2517         shm_mnt = ERR_PTR(error);
2518         return error;
2519 }
2520 module_init(init_tmpfs)
2521
2522 /*
2523  * shmem_file_setup - get an unlinked file living in tmpfs
2524  *
2525  * @name: name for dentry (to be seen in /proc/<pid>/maps
2526  * @size: size to be set for the file
2527  *
2528  */
2529 struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags)
2530 {
2531         int error;
2532         struct file *file;
2533         struct inode *inode;
2534         struct dentry *dentry, *root;
2535         struct qstr this;
2536
2537         if (IS_ERR(shm_mnt))
2538                 return (void *)shm_mnt;
2539
2540         if (size < 0 || size > SHMEM_MAX_BYTES)
2541                 return ERR_PTR(-EINVAL);
2542
2543         if (shmem_acct_size(flags, size))
2544                 return ERR_PTR(-ENOMEM);
2545
2546         error = -ENOMEM;
2547         this.name = name;
2548         this.len = strlen(name);
2549         this.hash = 0; /* will go */
2550         root = shm_mnt->mnt_root;
2551         dentry = d_alloc(root, &this);
2552         if (!dentry)
2553                 goto put_memory;
2554
2555         error = -ENFILE;
2556         file = get_empty_filp();
2557         if (!file)
2558                 goto put_dentry;
2559
2560         error = -ENOSPC;
2561         inode = shmem_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0);
2562         if (!inode)
2563                 goto close_file;
2564
2565         SHMEM_I(inode)->flags = flags & VM_ACCOUNT;
2566         d_instantiate(dentry, inode);
2567         inode->i_size = size;
2568         inode->i_nlink = 0;     /* It is unlinked */
2569         file->f_path.mnt = mntget(shm_mnt);
2570         file->f_path.dentry = dentry;
2571         file->f_mapping = inode->i_mapping;
2572         file->f_op = &shmem_file_operations;
2573         file->f_mode = FMODE_WRITE | FMODE_READ;
2574         return file;
2575
2576 close_file:
2577         put_filp(file);
2578 put_dentry:
2579         dput(dentry);
2580 put_memory:
2581         shmem_unacct_size(flags, size);
2582         return ERR_PTR(error);
2583 }
2584
2585 /*
2586  * shmem_zero_setup - setup a shared anonymous mapping
2587  *
2588  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
2589  */
2590 int shmem_zero_setup(struct vm_area_struct *vma)
2591 {
2592         struct file *file;
2593         loff_t size = vma->vm_end - vma->vm_start;
2594
2595         file = shmem_file_setup("dev/zero", size, vma->vm_flags);
2596         if (IS_ERR(file))
2597                 return PTR_ERR(file);
2598
2599         if (vma->vm_file)
2600                 fput(vma->vm_file);
2601         vma->vm_file = file;
2602         vma->vm_ops = &shmem_vm_ops;
2603         return 0;
2604 }