mm/shmem.c

   1 /*
   2  * Resizable virtual memory filesystem for Linux.
   3  *
   4  * Copyright (C) 2000 Linus Torvalds.
   5  *               2000 Transmeta Corp.
   6  *               2000-2001 Christoph Rohland
   7  *               2000-2001 SAP AG
   8  *               2002 Red Hat Inc.
   9  * Copyright (C) 2002-2005 Hugh Dickins.
  10  * Copyright (C) 2002-2005 VERITAS Software Corporation.
  11  * Copyright (C) 2004 Andi Kleen, SuSE Labs
  12  *
  13  * Extended attribute support for tmpfs:
  14  * Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@lkcl.net>
  15  * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
  16  *
  17  * This file is released under the GPL.
  18  */
  19
  20 /*
  21  * This virtual memory filesystem is heavily based on the ramfs. It
  22  * extends ramfs by the ability to use swap and honor resource limits
  23  * which makes it a completely usable filesystem.
  24  */
  25
  26 #include <linux/module.h>
  27 #include <linux/init.h>
  28 #include <linux/fs.h>
  29 #include <linux/xattr.h>
  30 #include <linux/exportfs.h>
  31 #include <linux/generic_acl.h>
  32 #include <linux/mm.h>
  33 #include <linux/mman.h>
  34 #include <linux/file.h>
  35 #include <linux/swap.h>
  36 #include <linux/pagemap.h>
  37 #include <linux/string.h>
  38 #include <linux/slab.h>
  39 #include <linux/backing-dev.h>
  40 #include <linux/shmem_fs.h>
  41 #include <linux/mount.h>
  42 #include <linux/writeback.h>
  43 #include <linux/vfs.h>
  44 #include <linux/blkdev.h>
  45 #include <linux/security.h>
  46 #include <linux/swapops.h>
  47 #include <linux/mempolicy.h>
  48 #include <linux/namei.h>
  49 #include <linux/ctype.h>
  50 #include <linux/migrate.h>
  51 #include <linux/highmem.h>
  52 #include <linux/backing-dev.h>
  53
  54 #include <asm/uaccess.h>
  55 #include <asm/div64.h>
  56 #include <asm/pgtable.h>
  57
  58 /* This magic number is used in glibc for posix shared memory */
  59 #define TMPFS_MAGIC     0x01021994
  60
  61 #define ENTRIES_PER_PAGE (PAGE_CACHE_SIZE/sizeof(unsigned long))
  62 #define ENTRIES_PER_PAGEPAGE (ENTRIES_PER_PAGE*ENTRIES_PER_PAGE)
  63 #define BLOCKS_PER_PAGE  (PAGE_CACHE_SIZE/512)
  64
  65 #define SHMEM_MAX_INDEX  (SHMEM_NR_DIRECT + (ENTRIES_PER_PAGEPAGE/2) * (ENTRIES_PER_PAGE+1))
  66 #define SHMEM_MAX_BYTES  ((unsigned long long)SHMEM_MAX_INDEX << PAGE_CACHE_SHIFT)
  67
  68 #define VM_ACCT(size)    (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
  69
  70 /* info->flags needs VM_flags to handle pagein/truncate races efficiently */
  71 #define SHMEM_PAGEIN     VM_READ
  72 #define SHMEM_TRUNCATE   VM_WRITE
  73
  74 /* Definition to limit shmem_truncate's steps between cond_rescheds */
  75 #define LATENCY_LIMIT    64
  76
  77 /* Pretend that each entry is of this size in directory's i_size */
  78 #define BOGO_DIRENT_SIZE 20
  79
  80 /* Flag allocation requirements to shmem_getpage and shmem_swp_alloc */
  81 enum sgp_type {
  82         SGP_QUICK,      /* don't try more than file page cache lookup */
  83         SGP_READ,       /* don't exceed i_size, don't allocate page */
  84         SGP_CACHE,      /* don't exceed i_size, may allocate page */
  85         SGP_WRITE,      /* may exceed i_size, may allocate page */
  86 };
  87
  88 static int shmem_getpage(struct inode *inode, unsigned long idx,
  89                          struct page **pagep, enum sgp_type sgp, int *type);
  90
  91 static inline struct page *shmem_dir_alloc(gfp_t gfp_mask)
  92 {
  93         /*
  94          * The above definition of ENTRIES_PER_PAGE, and the use of
  95          * BLOCKS_PER_PAGE on indirect pages, assume PAGE_CACHE_SIZE:
  96          * might be reconsidered if it ever diverges from PAGE_SIZE.
  97          *
  98          * __GFP_MOVABLE is masked out as swap vectors cannot move
  99          */
 100         return alloc_pages((gfp_mask & ~__GFP_MOVABLE) | __GFP_ZERO,
 101                                 PAGE_CACHE_SHIFT-PAGE_SHIFT);
 102 }
 103
 104 static inline void shmem_dir_free(struct page *page)
 105 {
 106         __free_pages(page, PAGE_CACHE_SHIFT-PAGE_SHIFT);
 107 }
 108
 109 static struct page **shmem_dir_map(struct page *page)
 110 {
 111         return (struct page **)kmap_atomic(page, KM_USER0);
 112 }
 113
 114 static inline void shmem_dir_unmap(struct page **dir)
 115 {
 116         kunmap_atomic(dir, KM_USER0);
 117 }
 118
 119 static swp_entry_t *shmem_swp_map(struct page *page)
 120 {
 121         return (swp_entry_t *)kmap_atomic(page, KM_USER1);
 122 }
 123
 124 static inline void shmem_swp_balance_unmap(void)
 125 {
 126         /*
 127          * When passing a pointer to an i_direct entry, to code which
 128          * also handles indirect entries and so will shmem_swp_unmap,
 129          * we must arrange for the preempt count to remain in balance.
 130          * What kmap_atomic of a lowmem page does depends on config
 131          * and architecture, so pretend to kmap_atomic some lowmem page.
 132          */
 133         (void) kmap_atomic(ZERO_PAGE(0), KM_USER1);
 134 }
 135
 136 static inline void shmem_swp_unmap(swp_entry_t *entry)
 137 {
 138         kunmap_atomic(entry, KM_USER1);
 139 }
 140
 141 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
 142 {
 143         return sb->s_fs_info;
 144 }
 145
 146 /*
 147  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
 148  * for shared memory and for shared anonymous (/dev/zero) mappings
 149  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
 150  * consistent with the pre-accounting of private mappings ...
 151  */
 152 static inline int shmem_acct_size(unsigned long flags, loff_t size)
 153 {
 154         return (flags & VM_ACCOUNT)?
 155                 security_vm_enough_memory(VM_ACCT(size)): 0;
 156 }
 157
 158 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
 159 {
 160         if (flags & VM_ACCOUNT)
 161                 vm_unacct_memory(VM_ACCT(size));
 162 }
 163
 164 /*
 165  * ... whereas tmpfs objects are accounted incrementally as
 166  * pages are allocated, in order to allow huge sparse files.
 167  * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
 168  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
 169  */
 170 static inline int shmem_acct_block(unsigned long flags)
 171 {
 172         return (flags & VM_ACCOUNT)?
 173                 0: security_vm_enough_memory(VM_ACCT(PAGE_CACHE_SIZE));
 174 }
 175
 176 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
 177 {
 178         if (!(flags & VM_ACCOUNT))
 179                 vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
 180 }
 181
 182 static const struct super_operations shmem_ops;
 183 static const struct address_space_operations shmem_aops;
 184 static const struct file_operations shmem_file_operations;
 185 static const struct inode_operations shmem_inode_operations;
 186 static const struct inode_operations shmem_dir_inode_operations;
 187 static const struct inode_operations shmem_special_inode_operations;
 188 static struct vm_operations_struct shmem_vm_ops;
 189
 190 static struct backing_dev_info shmem_backing_dev_info  __read_mostly = {
 191         .ra_pages       = 0,    /* No readahead */
 192         .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
 193         .unplug_io_fn   = default_unplug_io_fn,
 194 };
 195
 196 static LIST_HEAD(shmem_swaplist);
 197 static DEFINE_SPINLOCK(shmem_swaplist_lock);
 198
 199 static void shmem_free_blocks(struct inode *inode, long pages)
 200 {
 201         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 202         if (sbinfo->max_blocks) {
 203                 spin_lock(&sbinfo->stat_lock);
 204                 sbinfo->free_blocks += pages;
 205                 inode->i_blocks -= pages*BLOCKS_PER_PAGE;
 206                 spin_unlock(&sbinfo->stat_lock);
 207         }
 208 }
 209
 210 /*
 211  * shmem_recalc_inode - recalculate the size of an inode
 212  *
 213  * @inode: inode to recalc
 214  *
 215  * We have to calculate the free blocks since the mm can drop
 216  * undirtied hole pages behind our back.
 217  *
 218  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
 219  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
 220  *
 221  * It has to be called with the spinlock held.
 222  */
 223 static void shmem_recalc_inode(struct inode *inode)
 224 {
 225         struct shmem_inode_info *info = SHMEM_I(inode);
 226         long freed;
 227
 228         freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
 229         if (freed > 0) {
 230                 info->alloced -= freed;
 231                 shmem_unacct_blocks(info->flags, freed);
 232                 shmem_free_blocks(inode, freed);
 233         }
 234 }
 235
 236 /*
 237  * shmem_swp_entry - find the swap vector position in the info structure
 238  *
 239  * @info:  info structure for the inode
 240  * @index: index of the page to find
 241  * @page:  optional page to add to the structure. Has to be preset to
 242  *         all zeros
 243  *
 244  * If there is no space allocated yet it will return NULL when
 245  * page is NULL, else it will use the page for the needed block,
 246  * setting it to NULL on return to indicate that it has been used.
 247  *
 248  * The swap vector is organized the following way:
 249  *
 250  * There are SHMEM_NR_DIRECT entries directly stored in the
 251  * shmem_inode_info structure. So small files do not need an addional
 252  * allocation.
 253  *
 254  * For pages with index > SHMEM_NR_DIRECT there is the pointer
 255  * i_indirect which points to a page which holds in the first half
 256  * doubly indirect blocks, in the second half triple indirect blocks:
 257  *
 258  * For an artificial ENTRIES_PER_PAGE = 4 this would lead to the
 259  * following layout (for SHMEM_NR_DIRECT == 16):
 260  *
 261  * i_indirect -> dir --> 16-19
 262  *            |      +-> 20-23
 263  *            |
 264  *            +-->dir2 --> 24-27
 265  *            |        +-> 28-31
 266  *            |        +-> 32-35
 267  *            |        +-> 36-39
 268  *            |
 269  *            +-->dir3 --> 40-43
 270  *                     +-> 44-47
 271  *                     +-> 48-51
 272  *                     +-> 52-55
 273  */
 274 static swp_entry_t *shmem_swp_entry(struct shmem_inode_info *info, unsigned long index, struct page **page)
 275 {
 276         unsigned long offset;
 277         struct page **dir;
 278         struct page *subdir;
 279
 280         if (index < SHMEM_NR_DIRECT) {
 281                 shmem_swp_balance_unmap();
 282                 return info->i_direct+index;
 283         }
 284         if (!info->i_indirect) {
 285                 if (page) {
 286                         info->i_indirect = *page;
 287                         *page = NULL;
 288                 }
 289                 return NULL;                    /* need another page */
 290         }
 291
 292         index -= SHMEM_NR_DIRECT;
 293         offset = index % ENTRIES_PER_PAGE;
 294         index /= ENTRIES_PER_PAGE;
 295         dir = shmem_dir_map(info->i_indirect);
 296
 297         if (index >= ENTRIES_PER_PAGE/2) {
 298                 index -= ENTRIES_PER_PAGE/2;
 299                 dir += ENTRIES_PER_PAGE/2 + index/ENTRIES_PER_PAGE;
 300                 index %= ENTRIES_PER_PAGE;
 301                 subdir = *dir;
 302                 if (!subdir) {
 303                         if (page) {
 304                                 *dir = *page;
 305                                 *page = NULL;
 306                         }
 307                         shmem_dir_unmap(dir);
 308                         return NULL;            /* need another page */
 309                 }
 310                 shmem_dir_unmap(dir);
 311                 dir = shmem_dir_map(subdir);
 312         }
 313
 314         dir += index;
 315         subdir = *dir;
 316         if (!subdir) {
 317                 if (!page || !(subdir = *page)) {
 318                         shmem_dir_unmap(dir);
 319                         return NULL;            /* need a page */
 320                 }
 321                 *dir = subdir;
 322                 *page = NULL;
 323         }
 324         shmem_dir_unmap(dir);
 325         return shmem_swp_map(subdir) + offset;
 326 }
 327
 328 static void shmem_swp_set(struct shmem_inode_info *info, swp_entry_t *entry, unsigned long value)
 329 {
 330         long incdec = value? 1: -1;
 331
 332         entry->val = value;
 333         info->swapped += incdec;
 334         if ((unsigned long)(entry - info->i_direct) >= SHMEM_NR_DIRECT) {
 335                 struct page *page = kmap_atomic_to_page(entry);
 336                 set_page_private(page, page_private(page) + incdec);
 337         }
 338 }
 339
 340 /*
 341  * shmem_swp_alloc - get the position of the swap entry for the page.
 342  *                   If it does not exist allocate the entry.
 343  *
 344  * @info:       info structure for the inode
 345  * @index:      index of the page to find
 346  * @sgp:        check and recheck i_size? skip allocation?
 347  */
 348 static swp_entry_t *shmem_swp_alloc(struct shmem_inode_info *info, unsigned long index, enum sgp_type sgp)
 349 {
 350         struct inode *inode = &info->vfs_inode;
 351         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 352         struct page *page = NULL;
 353         swp_entry_t *entry;
 354
 355         if (sgp != SGP_WRITE &&
 356             ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode))
 357                 return ERR_PTR(-EINVAL);
 358
 359         while (!(entry = shmem_swp_entry(info, index, &page))) {
 360                 if (sgp == SGP_READ)
 361                         return shmem_swp_map(ZERO_PAGE(0));
 362                 /*
 363                  * Test free_blocks against 1 not 0, since we have 1 data
 364                  * page (and perhaps indirect index pages) yet to allocate:
 365                  * a waste to allocate index if we cannot allocate data.
 366                  */
 367                 if (sbinfo->max_blocks) {
 368                         spin_lock(&sbinfo->stat_lock);
 369                         if (sbinfo->free_blocks <= 1) {
 370                                 spin_unlock(&sbinfo->stat_lock);
 371                                 return ERR_PTR(-ENOSPC);
 372                         }
 373                         sbinfo->free_blocks--;
 374                         inode->i_blocks += BLOCKS_PER_PAGE;
 375                         spin_unlock(&sbinfo->stat_lock);
 376                 }
 377
 378                 spin_unlock(&info->lock);
 379                 page = shmem_dir_alloc(mapping_gfp_mask(inode->i_mapping));
 380                 if (page)
 381                         set_page_private(page, 0);
 382                 spin_lock(&info->lock);
 383
 384                 if (!page) {
 385                         shmem_free_blocks(inode, 1);
 386                         return ERR_PTR(-ENOMEM);
 387                 }
 388                 if (sgp != SGP_WRITE &&
 389                     ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
 390                         entry = ERR_PTR(-EINVAL);
 391                         break;
 392                 }
 393                 if (info->next_index <= index)
 394                         info->next_index = index + 1;
 395         }
 396         if (page) {
 397                 /* another task gave its page, or truncated the file */
 398                 shmem_free_blocks(inode, 1);
 399                 shmem_dir_free(page);
 400         }
 401         if (info->next_index <= index && !IS_ERR(entry))
 402                 info->next_index = index + 1;
 403         return entry;
 404 }
 405
 406 /*
 407  * shmem_free_swp - free some swap entries in a directory
 408  *
 409  * @dir:        pointer to the directory
 410  * @edir:       pointer after last entry of the directory
 411  * @punch_lock: pointer to spinlock when needed for the holepunch case
 412  */
 413 static int shmem_free_swp(swp_entry_t *dir, swp_entry_t *edir,
 414                                                 spinlock_t *punch_lock)
 415 {
 416         spinlock_t *punch_unlock = NULL;
 417         swp_entry_t *ptr;
 418         int freed = 0;
 419
 420         for (ptr = dir; ptr < edir; ptr++) {
 421                 if (ptr->val) {
 422                         if (unlikely(punch_lock)) {
 423                                 punch_unlock = punch_lock;
 424                                 punch_lock = NULL;
 425                                 spin_lock(punch_unlock);
 426                                 if (!ptr->val)
 427                                         continue;
 428                         }
 429                         free_swap_and_cache(*ptr);
 430                         *ptr = (swp_entry_t){0};
 431                         freed++;
 432                 }
 433         }
 434         if (punch_unlock)
 435                 spin_unlock(punch_unlock);
 436         return freed;
 437 }
 438
 439 static int shmem_map_and_free_swp(struct page *subdir, int offset,
 440                 int limit, struct page ***dir, spinlock_t *punch_lock)
 441 {
 442         swp_entry_t *ptr;
 443         int freed = 0;
 444
 445         ptr = shmem_swp_map(subdir);
 446         for (; offset < limit; offset += LATENCY_LIMIT) {
 447                 int size = limit - offset;
 448                 if (size > LATENCY_LIMIT)
 449                         size = LATENCY_LIMIT;
 450                 freed += shmem_free_swp(ptr+offset, ptr+offset+size,
 451                                                         punch_lock);
 452                 if (need_resched()) {
 453                         shmem_swp_unmap(ptr);
 454                         if (*dir) {
 455                                 shmem_dir_unmap(*dir);
 456                                 *dir = NULL;
 457                         }
 458                         cond_resched();
 459                         ptr = shmem_swp_map(subdir);
 460                 }
 461         }
 462         shmem_swp_unmap(ptr);
 463         return freed;
 464 }
 465
 466 static void shmem_free_pages(struct list_head *next)
 467 {
 468         struct page *page;
 469         int freed = 0;
 470
 471         do {
 472                 page = container_of(next, struct page, lru);
 473                 next = next->next;
 474                 shmem_dir_free(page);
 475                 freed++;
 476                 if (freed >= LATENCY_LIMIT) {
 477                         cond_resched();
 478                         freed = 0;
 479                 }
 480         } while (next);
 481 }
 482
 483 static void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end)
 484 {
 485         struct shmem_inode_info *info = SHMEM_I(inode);
 486         unsigned long idx;
 487         unsigned long size;
 488         unsigned long limit;
 489         unsigned long stage;
 490         unsigned long diroff;
 491         struct page **dir;
 492         struct page *topdir;
 493         struct page *middir;
 494         struct page *subdir;
 495         swp_entry_t *ptr;
 496         LIST_HEAD(pages_to_free);
 497         long nr_pages_to_free = 0;
 498         long nr_swaps_freed = 0;
 499         int offset;
 500         int freed;
 501         int punch_hole;
 502         spinlock_t *needs_lock;
 503         spinlock_t *punch_lock;
 504         unsigned long upper_limit;
 505
 506         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
 507         idx = (start + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 508         if (idx >= info->next_index)
 509                 return;
 510
 511         spin_lock(&info->lock);
 512         info->flags |= SHMEM_TRUNCATE;
 513         if (likely(end == (loff_t) -1)) {
 514                 limit = info->next_index;
 515                 upper_limit = SHMEM_MAX_INDEX;
 516                 info->next_index = idx;
 517                 needs_lock = NULL;
 518                 punch_hole = 0;
 519         } else {
 520                 if (end + 1 >= inode->i_size) { /* we may free a little more */
 521                         limit = (inode->i_size + PAGE_CACHE_SIZE - 1) >>
 522                                                         PAGE_CACHE_SHIFT;
 523                         upper_limit = SHMEM_MAX_INDEX;
 524                 } else {
 525                         limit = (end + 1) >> PAGE_CACHE_SHIFT;
 526                         upper_limit = limit;
 527                 }
 528                 needs_lock = &info->lock;
 529                 punch_hole = 1;
 530         }
 531
 532         topdir = info->i_indirect;
 533         if (topdir && idx <= SHMEM_NR_DIRECT && !punch_hole) {
 534                 info->i_indirect = NULL;
 535                 nr_pages_to_free++;
 536                 list_add(&topdir->lru, &pages_to_free);
 537         }
 538         spin_unlock(&info->lock);
 539
 540         if (info->swapped && idx < SHMEM_NR_DIRECT) {
 541                 ptr = info->i_direct;
 542                 size = limit;
 543                 if (size > SHMEM_NR_DIRECT)
 544                         size = SHMEM_NR_DIRECT;
 545                 nr_swaps_freed = shmem_free_swp(ptr+idx, ptr+size, needs_lock);
 546         }
 547
 548         /*
 549          * If there are no indirect blocks or we are punching a hole
 550          * below indirect blocks, nothing to be done.
 551          */
 552         if (!topdir || limit <= SHMEM_NR_DIRECT)
 553                 goto done2;
 554
 555         /*
 556          * The truncation case has already dropped info->lock, and we're safe
 557          * because i_size and next_index have already been lowered, preventing
 558          * access beyond.  But in the punch_hole case, we still need to take
 559          * the lock when updating the swap directory, because there might be
 560          * racing accesses by shmem_getpage(SGP_CACHE), shmem_unuse_inode or
 561          * shmem_writepage.  However, whenever we find we can remove a whole
 562          * directory page (not at the misaligned start or end of the range),
 563          * we first NULLify its pointer in the level above, and then have no
 564          * need to take the lock when updating its contents: needs_lock and
 565          * punch_lock (either pointing to info->lock or NULL) manage this.
 566          */
 567
 568         upper_limit -= SHMEM_NR_DIRECT;
 569         limit -= SHMEM_NR_DIRECT;
 570         idx = (idx > SHMEM_NR_DIRECT)? (idx - SHMEM_NR_DIRECT): 0;
 571         offset = idx % ENTRIES_PER_PAGE;
 572         idx -= offset;
 573
 574         dir = shmem_dir_map(topdir);
 575         stage = ENTRIES_PER_PAGEPAGE/2;
 576         if (idx < ENTRIES_PER_PAGEPAGE/2) {
 577                 middir = topdir;
 578                 diroff = idx/ENTRIES_PER_PAGE;
 579         } else {
 580                 dir += ENTRIES_PER_PAGE/2;
 581                 dir += (idx - ENTRIES_PER_PAGEPAGE/2)/ENTRIES_PER_PAGEPAGE;
 582                 while (stage <= idx)
 583                         stage += ENTRIES_PER_PAGEPAGE;
 584                 middir = *dir;
 585                 if (*dir) {
 586                         diroff = ((idx - ENTRIES_PER_PAGEPAGE/2) %
 587                                 ENTRIES_PER_PAGEPAGE) / ENTRIES_PER_PAGE;
 588                         if (!diroff && !offset && upper_limit >= stage) {
 589                                 if (needs_lock) {
 590                                         spin_lock(needs_lock);
 591                                         *dir = NULL;
 592                                         spin_unlock(needs_lock);
 593                                         needs_lock = NULL;
 594                                 } else
 595                                         *dir = NULL;
 596                                 nr_pages_to_free++;
 597                                 list_add(&middir->lru, &pages_to_free);
 598                         }
 599                         shmem_dir_unmap(dir);
 600                         dir = shmem_dir_map(middir);
 601                 } else {
 602                         diroff = 0;
 603                         offset = 0;
 604                         idx = stage;
 605                 }
 606         }
 607
 608         for (; idx < limit; idx += ENTRIES_PER_PAGE, diroff++) {
 609                 if (unlikely(idx == stage)) {
 610                         shmem_dir_unmap(dir);
 611                         dir = shmem_dir_map(topdir) +
 612                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
 613                         while (!*dir) {
 614                                 dir++;
 615                                 idx += ENTRIES_PER_PAGEPAGE;
 616                                 if (idx >= limit)
 617                                         goto done1;
 618                         }
 619                         stage = idx + ENTRIES_PER_PAGEPAGE;
 620                         middir = *dir;
 621                         if (punch_hole)
 622                                 needs_lock = &info->lock;
 623                         if (upper_limit >= stage) {
 624                                 if (needs_lock) {
 625                                         spin_lock(needs_lock);
 626                                         *dir = NULL;
 627                                         spin_unlock(needs_lock);
 628                                         needs_lock = NULL;
 629                                 } else
 630                                         *dir = NULL;
 631                                 nr_pages_to_free++;
 632                                 list_add(&middir->lru, &pages_to_free);
 633                         }
 634                         shmem_dir_unmap(dir);
 635                         cond_resched();
 636                         dir = shmem_dir_map(middir);
 637                         diroff = 0;
 638                 }
 639                 punch_lock = needs_lock;
 640                 subdir = dir[diroff];
 641                 if (subdir && !offset && upper_limit-idx >= ENTRIES_PER_PAGE) {
 642                         if (needs_lock) {
 643                                 spin_lock(needs_lock);
 644                                 dir[diroff] = NULL;
 645                                 spin_unlock(needs_lock);
 646                                 punch_lock = NULL;
 647                         } else
 648                                 dir[diroff] = NULL;
 649                         nr_pages_to_free++;
 650                         list_add(&subdir->lru, &pages_to_free);
 651                 }
 652                 if (subdir && page_private(subdir) /* has swap entries */) {
 653                         size = limit - idx;
 654                         if (size > ENTRIES_PER_PAGE)
 655                                 size = ENTRIES_PER_PAGE;
 656                         freed = shmem_map_and_free_swp(subdir,
 657                                         offset, size, &dir, punch_lock);
 658                         if (!dir)
 659                                 dir = shmem_dir_map(middir);
 660                         nr_swaps_freed += freed;
 661                         if (offset || punch_lock) {
 662                                 spin_lock(&info->lock);
 663                                 set_page_private(subdir,
 664                                         page_private(subdir) - freed);
 665                                 spin_unlock(&info->lock);
 666                         } else
 667                                 BUG_ON(page_private(subdir) != freed);
 668                 }
 669                 offset = 0;
 670         }
 671 done1:
 672         shmem_dir_unmap(dir);
 673 done2:
 674         if (inode->i_mapping->nrpages && (info->flags & SHMEM_PAGEIN)) {
 675                 /*
 676                  * Call truncate_inode_pages again: racing shmem_unuse_inode
 677                  * may have swizzled a page in from swap since vmtruncate or
 678                  * generic_delete_inode did it, before we lowered next_index.
 679                  * Also, though shmem_getpage checks i_size before adding to
 680                  * cache, no recheck after: so fix the narrow window there too.
 681                  *
 682                  * Recalling truncate_inode_pages_range and unmap_mapping_range
 683                  * every time for punch_hole (which never got a chance to clear
 684                  * SHMEM_PAGEIN at the start of vmtruncate_range) is expensive,
 685                  * yet hardly ever necessary: try to optimize them out later.
 686                  */
 687                 truncate_inode_pages_range(inode->i_mapping, start, end);
 688                 if (punch_hole)
 689                         unmap_mapping_range(inode->i_mapping, start,
 690                                                         end - start, 1);
 691         }
 692
 693         spin_lock(&info->lock);
 694         info->flags &= ~SHMEM_TRUNCATE;
 695         info->swapped -= nr_swaps_freed;
 696         if (nr_pages_to_free)
 697                 shmem_free_blocks(inode, nr_pages_to_free);
 698         shmem_recalc_inode(inode);
 699         spin_unlock(&info->lock);
 700
 701         /*
 702          * Empty swap vector directory pages to be freed?
 703          */
 704         if (!list_empty(&pages_to_free)) {
 705                 pages_to_free.prev->next = NULL;
 706                 shmem_free_pages(pages_to_free.next);
 707         }
 708 }
 709
 710 static void shmem_truncate(struct inode *inode)
 711 {
 712         shmem_truncate_range(inode, inode->i_size, (loff_t)-1);
 713 }
 714
 715 static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
 716 {
 717         struct inode *inode = dentry->d_inode;
 718         struct page *page = NULL;
 719         int error;
 720
 721         if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
 722                 if (attr->ia_size < inode->i_size) {
 723                         /*
 724                          * If truncating down to a partial page, then
 725                          * if that page is already allocated, hold it
 726                          * in memory until the truncation is over, so
 727                          * truncate_partial_page cannnot miss it were
 728                          * it assigned to swap.
 729                          */
 730                         if (attr->ia_size & (PAGE_CACHE_SIZE-1)) {
 731                                 (void) shmem_getpage(inode,
 732                                         attr->ia_size>>PAGE_CACHE_SHIFT,
 733                                                 &page, SGP_READ, NULL);
 734                         }
 735                         /*
 736                          * Reset SHMEM_PAGEIN flag so that shmem_truncate can
 737                          * detect if any pages might have been added to cache
 738                          * after truncate_inode_pages.  But we needn't bother
 739                          * if it's being fully truncated to zero-length: the
 740                          * nrpages check is efficient enough in that case.
 741                          */
 742                         if (attr->ia_size) {
 743                                 struct shmem_inode_info *info = SHMEM_I(inode);
 744                                 spin_lock(&info->lock);
 745                                 info->flags &= ~SHMEM_PAGEIN;
 746                                 spin_unlock(&info->lock);
 747                         }
 748                 }
 749         }
 750
 751         error = inode_change_ok(inode, attr);
 752         if (!error)
 753                 error = inode_setattr(inode, attr);
 754 #ifdef CONFIG_TMPFS_POSIX_ACL
 755         if (!error && (attr->ia_valid & ATTR_MODE))
 756                 error = generic_acl_chmod(inode, &shmem_acl_ops);
 757 #endif
 758         if (page)
 759                 page_cache_release(page);
 760         return error;
 761 }
 762
 763 static void shmem_delete_inode(struct inode *inode)
 764 {
 765         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 766         struct shmem_inode_info *info = SHMEM_I(inode);
 767
 768         if (inode->i_op->truncate == shmem_truncate) {
 769                 truncate_inode_pages(inode->i_mapping, 0);
 770                 shmem_unacct_size(info->flags, inode->i_size);
 771                 inode->i_size = 0;
 772                 shmem_truncate(inode);
 773                 if (!list_empty(&info->swaplist)) {
 774                         spin_lock(&shmem_swaplist_lock);
 775                         list_del_init(&info->swaplist);
 776                         spin_unlock(&shmem_swaplist_lock);
 777                 }
 778         }
 779         BUG_ON(inode->i_blocks);
 780         if (sbinfo->max_inodes) {
 781                 spin_lock(&sbinfo->stat_lock);
 782                 sbinfo->free_inodes++;
 783                 spin_unlock(&sbinfo->stat_lock);
 784         }
 785         clear_inode(inode);
 786 }
 787
 788 static inline int shmem_find_swp(swp_entry_t entry, swp_entry_t *dir, swp_entry_t *edir)
 789 {
 790         swp_entry_t *ptr;
 791
 792         for (ptr = dir; ptr < edir; ptr++) {
 793                 if (ptr->val == entry.val)
 794                         return ptr - dir;
 795         }
 796         return -1;
 797 }
 798
 799 static int shmem_unuse_inode(struct shmem_inode_info *info, swp_entry_t entry, struct page *page)
 800 {
 801         struct inode *inode;
 802         unsigned long idx;
 803         unsigned long size;
 804         unsigned long limit;
 805         unsigned long stage;
 806         struct page **dir;
 807         struct page *subdir;
 808         swp_entry_t *ptr;
 809         int offset;
 810
 811         idx = 0;
 812         ptr = info->i_direct;
 813         spin_lock(&info->lock);
 814         limit = info->next_index;
 815         size = limit;
 816         if (size > SHMEM_NR_DIRECT)
 817                 size = SHMEM_NR_DIRECT;
 818         offset = shmem_find_swp(entry, ptr, ptr+size);
 819         if (offset >= 0) {
 820                 shmem_swp_balance_unmap();
 821                 goto found;
 822         }
 823         if (!info->i_indirect)
 824                 goto lost2;
 825
 826         dir = shmem_dir_map(info->i_indirect);
 827         stage = SHMEM_NR_DIRECT + ENTRIES_PER_PAGEPAGE/2;
 828
 829         for (idx = SHMEM_NR_DIRECT; idx < limit; idx += ENTRIES_PER_PAGE, dir++) {
 830                 if (unlikely(idx == stage)) {
 831                         shmem_dir_unmap(dir-1);
 832                         dir = shmem_dir_map(info->i_indirect) +
 833                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
 834                         while (!*dir) {
 835                                 dir++;
 836                                 idx += ENTRIES_PER_PAGEPAGE;
 837                                 if (idx >= limit)
 838                                         goto lost1;
 839                         }
 840                         stage = idx + ENTRIES_PER_PAGEPAGE;
 841                         subdir = *dir;
 842                         shmem_dir_unmap(dir);
 843                         dir = shmem_dir_map(subdir);
 844                 }
 845                 subdir = *dir;
 846                 if (subdir && page_private(subdir)) {
 847                         ptr = shmem_swp_map(subdir);
 848                         size = limit - idx;
 849                         if (size > ENTRIES_PER_PAGE)
 850                                 size = ENTRIES_PER_PAGE;
 851                         offset = shmem_find_swp(entry, ptr, ptr+size);
 852                         if (offset >= 0) {
 853                                 shmem_dir_unmap(dir);
 854                                 goto found;
 855                         }
 856                         shmem_swp_unmap(ptr);
 857                 }
 858         }
 859 lost1:
 860         shmem_dir_unmap(dir-1);
 861 lost2:
 862         spin_unlock(&info->lock);
 863         return 0;
 864 found:
 865         idx += offset;
 866         inode = &info->vfs_inode;
 867         if (move_from_swap_cache(page, idx, inode->i_mapping) == 0) {
 868                 info->flags |= SHMEM_PAGEIN;
 869                 shmem_swp_set(info, ptr + offset, 0);
 870         }
 871         shmem_swp_unmap(ptr);
 872         spin_unlock(&info->lock);
 873         /*
 874          * Decrement swap count even when the entry is left behind:
 875          * try_to_unuse will skip over mms, then reincrement count.
 876          */
 877         swap_free(entry);
 878         return 1;
 879 }
 880
 881 /*
 882  * shmem_unuse() search for an eventually swapped out shmem page.
 883  */
 884 int shmem_unuse(swp_entry_t entry, struct page *page)
 885 {
 886         struct list_head *p, *next;
 887         struct shmem_inode_info *info;
 888         int found = 0;
 889
 890         spin_lock(&shmem_swaplist_lock);
 891         list_for_each_safe(p, next, &shmem_swaplist) {
 892                 info = list_entry(p, struct shmem_inode_info, swaplist);
 893                 if (!info->swapped)
 894                         list_del_init(&info->swaplist);
 895                 else if (shmem_unuse_inode(info, entry, page)) {
 896                         /* move head to start search for next from here */
 897                         list_move_tail(&shmem_swaplist, &info->swaplist);
 898                         found = 1;
 899                         break;
 900                 }
 901         }
 902         spin_unlock(&shmem_swaplist_lock);
 903         return found;
 904 }
 905
 906 /*
 907  * Move the page from the page cache to the swap cache.
 908  */
 909 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 910 {
 911         struct shmem_inode_info *info;
 912         swp_entry_t *entry, swap;
 913         struct address_space *mapping;
 914         unsigned long index;
 915         struct inode *inode;
 916
 917         BUG_ON(!PageLocked(page));
 918         BUG_ON(page_mapped(page));
 919
 920         mapping = page->mapping;
 921         index = page->index;
 922         inode = mapping->host;
 923         info = SHMEM_I(inode);
 924         if (info->flags & VM_LOCKED)
 925                 goto redirty;
 926         swap = get_swap_page();
 927         if (!swap.val)
 928                 goto redirty;
 929
 930         spin_lock(&info->lock);
 931         shmem_recalc_inode(inode);
 932         if (index >= info->next_index) {
 933                 BUG_ON(!(info->flags & SHMEM_TRUNCATE));
 934                 goto unlock;
 935         }
 936         entry = shmem_swp_entry(info, index, NULL);
 937         BUG_ON(!entry);
 938         BUG_ON(entry->val);
 939
 940         if (move_to_swap_cache(page, swap) == 0) {
 941                 shmem_swp_set(info, entry, swap.val);
 942                 shmem_swp_unmap(entry);
 943                 spin_unlock(&info->lock);
 944                 if (list_empty(&info->swaplist)) {
 945                         spin_lock(&shmem_swaplist_lock);
 946                         /* move instead of add in case we're racing */
 947                         list_move_tail(&info->swaplist, &shmem_swaplist);
 948                         spin_unlock(&shmem_swaplist_lock);
 949                 }
 950                 unlock_page(page);
 951                 return 0;
 952         }
 953
 954         shmem_swp_unmap(entry);
 955 unlock:
 956         spin_unlock(&info->lock);
 957         swap_free(swap);
 958 redirty:
 959         set_page_dirty(page);
 960         return AOP_WRITEPAGE_ACTIVATE;  /* Return with the page locked */
 961 }
 962
 963 #ifdef CONFIG_NUMA
 964 static inline int shmem_parse_mpol(char *value, int *policy, nodemask_t *policy_nodes)
 965 {
 966         char *nodelist = strchr(value, ':');
 967         int err = 1;
 968
 969         if (nodelist) {
 970                 /* NUL-terminate policy string */
 971                 *nodelist++ = '\0';
 972                 if (nodelist_parse(nodelist, *policy_nodes))
 973                         goto out;
 974                 if (!nodes_subset(*policy_nodes, node_online_map))
 975                         goto out;
 976         }
 977         if (!strcmp(value, "default")) {
 978                 *policy = MPOL_DEFAULT;
 979                 /* Don't allow a nodelist */
 980                 if (!nodelist)
 981                         err = 0;
 982         } else if (!strcmp(value, "prefer")) {
 983                 *policy = MPOL_PREFERRED;
 984                 /* Insist on a nodelist of one node only */
 985                 if (nodelist) {
 986                         char *rest = nodelist;
 987                         while (isdigit(*rest))
 988                                 rest++;
 989                         if (!*rest)
 990                                 err = 0;
 991                 }
 992         } else if (!strcmp(value, "bind")) {
 993                 *policy = MPOL_BIND;
 994                 /* Insist on a nodelist */
 995                 if (nodelist)
 996                         err = 0;
 997         } else if (!strcmp(value, "interleave")) {
 998                 *policy = MPOL_INTERLEAVE;
 999                 /* Default to nodes online if no nodelist */
1000                 if (!nodelist)
1001                         *policy_nodes = node_online_map;
1002                 err = 0;
1003         }
1004 out:
1005         /* Restore string for error message */
1006         if (nodelist)
1007                 *--nodelist = ':';
1008         return err;
1009 }
1010
1011 static struct page *shmem_swapin_async(struct shared_policy *p,
1012                                        swp_entry_t entry, unsigned long idx)
1013 {
1014         struct page *page;
1015         struct vm_area_struct pvma;
1016
1017         /* Create a pseudo vma that just contains the policy */
1018         memset(&pvma, 0, sizeof(struct vm_area_struct));
1019         pvma.vm_end = PAGE_SIZE;
1020         pvma.vm_pgoff = idx;
1021         pvma.vm_policy = mpol_shared_policy_lookup(p, idx);
1022         page = read_swap_cache_async(entry, &pvma, 0);
1023         mpol_free(pvma.vm_policy);
1024         return page;
1025 }
1026
1027 struct page *shmem_swapin(struct shmem_inode_info *info, swp_entry_t entry,
1028                           unsigned long idx)
1029 {
1030         struct shared_policy *p = &info->policy;
1031         int i, num;
1032         struct page *page;
1033         unsigned long offset;
1034
1035         num = valid_swaphandles(entry, &offset);
1036         for (i = 0; i < num; offset++, i++) {
1037                 page = shmem_swapin_async(p,
1038                                 swp_entry(swp_type(entry), offset), idx);
1039                 if (!page)
1040                         break;
1041                 page_cache_release(page);
1042         }
1043         lru_add_drain();        /* Push any new pages onto the LRU now */
1044         return shmem_swapin_async(p, entry, idx);
1045 }
1046
1047 static struct page *
1048 shmem_alloc_page(gfp_t gfp, struct shmem_inode_info *info,
1049                  unsigned long idx)
1050 {
1051         struct vm_area_struct pvma;
1052         struct page *page;
1053
1054         memset(&pvma, 0, sizeof(struct vm_area_struct));
1055         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx);
1056         pvma.vm_pgoff = idx;
1057         pvma.vm_end = PAGE_SIZE;
1058         page = alloc_page_vma(gfp | __GFP_ZERO, &pvma, 0);
1059         mpol_free(pvma.vm_policy);
1060         return page;
1061 }
1062 #else
1063 static inline int shmem_parse_mpol(char *value, int *policy, nodemask_t *policy_nodes)
1064 {
1065         return 1;
1066 }
1067
1068 static inline struct page *
1069 shmem_swapin(struct shmem_inode_info *info,swp_entry_t entry,unsigned long idx)
1070 {
1071         swapin_readahead(entry, 0, NULL);
1072         return read_swap_cache_async(entry, NULL, 0);
1073 }
1074
1075 static inline struct page *
1076 shmem_alloc_page(gfp_t gfp,struct shmem_inode_info *info, unsigned long idx)
1077 {
1078         return alloc_page(gfp | __GFP_ZERO);
1079 }
1080 #endif
1081
1082 /*
1083  * shmem_getpage - either get the page from swap or allocate a new one
1084  *
1085  * If we allocate a new one we do not mark it dirty. That's up to the
1086  * vm. If we swap it in we mark it dirty since we also free the swap
1087  * entry since a page cannot live in both the swap and page cache
1088  */
1089 static int shmem_getpage(struct inode *inode, unsigned long idx,
1090                         struct page **pagep, enum sgp_type sgp, int *type)
1091 {
1092         struct address_space *mapping = inode->i_mapping;
1093         struct shmem_inode_info *info = SHMEM_I(inode);
1094         struct shmem_sb_info *sbinfo;
1095         struct page *filepage = *pagep;
1096         struct page *swappage;
1097         swp_entry_t *entry;
1098         swp_entry_t swap;
1099         int error;
1100
1101         if (idx >= SHMEM_MAX_INDEX)
1102                 return -EFBIG;
1103         /*
1104          * Normally, filepage is NULL on entry, and either found
1105          * uptodate immediately, or allocated and zeroed, or read
1106          * in under swappage, which is then assigned to filepage.
1107          * But shmem_readpage and shmem_prepare_write pass in a locked
1108          * filepage, which may be found not uptodate by other callers
1109          * too, and may need to be copied from the swappage read in.
1110          */
1111 repeat:
1112         if (!filepage)
1113                 filepage = find_lock_page(mapping, idx);
1114         if (filepage && PageUptodate(filepage))
1115                 goto done;
1116         error = 0;
1117         if (sgp == SGP_QUICK)
1118                 goto failed;
1119
1120         spin_lock(&info->lock);
1121         shmem_recalc_inode(inode);
1122         entry = shmem_swp_alloc(info, idx, sgp);
1123         if (IS_ERR(entry)) {
1124                 spin_unlock(&info->lock);
1125                 error = PTR_ERR(entry);
1126                 goto failed;
1127         }
1128         swap = *entry;
1129
1130         if (swap.val) {
1131                 /* Look it up and read it in.. */
1132                 swappage = lookup_swap_cache(swap);
1133                 if (!swappage) {
1134                         shmem_swp_unmap(entry);
1135                         /* here we actually do the io */
1136                         if (type && *type == VM_FAULT_MINOR) {
1137                                 __count_vm_event(PGMAJFAULT);
1138                                 *type = VM_FAULT_MAJOR;
1139                         }
1140                         spin_unlock(&info->lock);
1141                         swappage = shmem_swapin(info, swap, idx);
1142                         if (!swappage) {
1143                                 spin_lock(&info->lock);
1144                                 entry = shmem_swp_alloc(info, idx, sgp);
1145                                 if (IS_ERR(entry))
1146                                         error = PTR_ERR(entry);
1147                                 else {
1148                                         if (entry->val == swap.val)
1149                                                 error = -ENOMEM;
1150                                         shmem_swp_unmap(entry);
1151                                 }
1152                                 spin_unlock(&info->lock);
1153                                 if (error)
1154                                         goto failed;
1155                                 goto repeat;
1156                         }
1157                         wait_on_page_locked(swappage);
1158                         page_cache_release(swappage);
1159                         goto repeat;
1160                 }
1161
1162                 /* We have to do this with page locked to prevent races */
1163                 if (TestSetPageLocked(swappage)) {
1164                         shmem_swp_unmap(entry);
1165                         spin_unlock(&info->lock);
1166                         wait_on_page_locked(swappage);
1167                         page_cache_release(swappage);
1168                         goto repeat;
1169                 }
1170                 if (PageWriteback(swappage)) {
1171                         shmem_swp_unmap(entry);
1172                         spin_unlock(&info->lock);
1173                         wait_on_page_writeback(swappage);
1174                         unlock_page(swappage);
1175                         page_cache_release(swappage);
1176                         goto repeat;
1177                 }
1178                 if (!PageUptodate(swappage)) {
1179                         shmem_swp_unmap(entry);
1180                         spin_unlock(&info->lock);
1181                         unlock_page(swappage);
1182                         page_cache_release(swappage);
1183                         error = -EIO;
1184                         goto failed;
1185                 }
1186
1187                 if (filepage) {
1188                         shmem_swp_set(info, entry, 0);
1189                         shmem_swp_unmap(entry);
1190                         delete_from_swap_cache(swappage);
1191                         spin_unlock(&info->lock);
1192                         copy_highpage(filepage, swappage);
1193                         unlock_page(swappage);
1194                         page_cache_release(swappage);
1195                         flush_dcache_page(filepage);
1196                         SetPageUptodate(filepage);
1197                         set_page_dirty(filepage);
1198                         swap_free(swap);
1199                 } else if (!(error = move_from_swap_cache(
1200                                 swappage, idx, mapping))) {
1201                         info->flags |= SHMEM_PAGEIN;
1202                         shmem_swp_set(info, entry, 0);
1203                         shmem_swp_unmap(entry);
1204                         spin_unlock(&info->lock);
1205                         filepage = swappage;
1206                         swap_free(swap);
1207                 } else {
1208                         shmem_swp_unmap(entry);
1209                         spin_unlock(&info->lock);
1210                         unlock_page(swappage);
1211                         page_cache_release(swappage);
1212                         if (error == -ENOMEM) {
1213                                 /* let kswapd refresh zone for GFP_ATOMICs */
1214                                 congestion_wait(WRITE, HZ/50);
1215                         }
1216                         goto repeat;
1217                 }
1218         } else if (sgp == SGP_READ && !filepage) {
1219                 shmem_swp_unmap(entry);
1220                 filepage = find_get_page(mapping, idx);
1221                 if (filepage &&
1222                     (!PageUptodate(filepage) || TestSetPageLocked(filepage))) {
1223                         spin_unlock(&info->lock);
1224                         wait_on_page_locked(filepage);
1225                         page_cache_release(filepage);
1226                         filepage = NULL;
1227                         goto repeat;
1228                 }
1229                 spin_unlock(&info->lock);
1230         } else {
1231                 shmem_swp_unmap(entry);
1232                 sbinfo = SHMEM_SB(inode->i_sb);
1233                 if (sbinfo->max_blocks) {
1234                         spin_lock(&sbinfo->stat_lock);
1235                         if (sbinfo->free_blocks == 0 ||
1236                             shmem_acct_block(info->flags)) {
1237                                 spin_unlock(&sbinfo->stat_lock);
1238                                 spin_unlock(&info->lock);
1239                                 error = -ENOSPC;
1240                                 goto failed;
1241                         }
1242                         sbinfo->free_blocks--;
1243                         inode->i_blocks += BLOCKS_PER_PAGE;
1244                         spin_unlock(&sbinfo->stat_lock);
1245                 } else if (shmem_acct_block(info->flags)) {
1246                         spin_unlock(&info->lock);
1247                         error = -ENOSPC;
1248                         goto failed;
1249                 }
1250
1251                 if (!filepage) {
1252                         spin_unlock(&info->lock);
1253                         filepage = shmem_alloc_page(mapping_gfp_mask(mapping),
1254                                                     info,
1255                                                     idx);
1256                         if (!filepage) {
1257                                 shmem_unacct_blocks(info->flags, 1);
1258                                 shmem_free_blocks(inode, 1);
1259                                 error = -ENOMEM;
1260                                 goto failed;
1261                         }
1262
1263                         spin_lock(&info->lock);
1264                         entry = shmem_swp_alloc(info, idx, sgp);
1265                         if (IS_ERR(entry))
1266                                 error = PTR_ERR(entry);
1267                         else {
1268                                 swap = *entry;
1269                                 shmem_swp_unmap(entry);
1270                         }
1271                         if (error || swap.val || 0 != add_to_page_cache_lru(
1272                                         filepage, mapping, idx, GFP_ATOMIC)) {
1273                                 spin_unlock(&info->lock);
1274                                 page_cache_release(filepage);
1275                                 shmem_unacct_blocks(info->flags, 1);
1276                                 shmem_free_blocks(inode, 1);
1277                                 filepage = NULL;
1278                                 if (error)
1279                                         goto failed;
1280                                 goto repeat;
1281                         }
1282                         info->flags |= SHMEM_PAGEIN;
1283                 }
1284
1285                 info->alloced++;
1286                 spin_unlock(&info->lock);
1287                 flush_dcache_page(filepage);
1288                 SetPageUptodate(filepage);
1289         }
1290 done:
1291         if (*pagep != filepage) {
1292                 unlock_page(filepage);
1293                 *pagep = filepage;
1294         }
1295         return 0;
1296
1297 failed:
1298         if (*pagep != filepage) {
1299                 unlock_page(filepage);
1300                 page_cache_release(filepage);
1301         }
1302         return error;
1303 }
1304
1305 static struct page *shmem_nopage(struct vm_area_struct *vma,
1306                                  unsigned long address, int *type)
1307 {
1308         struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1309         struct page *page = NULL;
1310         unsigned long idx;
1311         int error;
1312
1313         idx = (address - vma->vm_start) >> PAGE_SHIFT;
1314         idx += vma->vm_pgoff;
1315         idx >>= PAGE_CACHE_SHIFT - PAGE_SHIFT;
1316         if (((loff_t) idx << PAGE_CACHE_SHIFT) >= i_size_read(inode))
1317                 return NOPAGE_SIGBUS;
1318
1319         error = shmem_getpage(inode, idx, &page, SGP_CACHE, type);
1320         if (error)
1321                 return (error == -ENOMEM)? NOPAGE_OOM: NOPAGE_SIGBUS;
1322
1323         mark_page_accessed(page);
1324         return page;
1325 }
1326
1327 static int shmem_populate(struct vm_area_struct *vma,
1328         unsigned long addr, unsigned long len,
1329         pgprot_t prot, unsigned long pgoff, int nonblock)
1330 {
1331         struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1332         struct mm_struct *mm = vma->vm_mm;
1333         enum sgp_type sgp = nonblock? SGP_QUICK: SGP_CACHE;
1334         unsigned long size;
1335
1336         size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
1337         if (pgoff >= size || pgoff + (len >> PAGE_SHIFT) > size)
1338                 return -EINVAL;
1339
1340         while ((long) len > 0) {
1341                 struct page *page = NULL;
1342                 int err;
1343                 /*
1344                  * Will need changing if PAGE_CACHE_SIZE != PAGE_SIZE
1345                  */
1346                 err = shmem_getpage(inode, pgoff, &page, sgp, NULL);
1347                 if (err)
1348                         return err;
1349                 /* Page may still be null, but only if nonblock was set. */
1350                 if (page) {
1351                         mark_page_accessed(page);
1352                         err = install_page(mm, vma, addr, page, prot);
1353                         if (err) {
1354                                 page_cache_release(page);
1355                                 return err;
1356                         }
1357                 } else if (vma->vm_flags & VM_NONLINEAR) {
1358                         /* No page was found just because we can't read it in
1359                          * now (being here implies nonblock != 0), but the page
1360                          * may exist, so set the PTE to fault it in later. */
1361                         err = install_file_pte(mm, vma, addr, pgoff, prot);
1362                         if (err)
1363                                 return err;
1364                 }
1365
1366                 len -= PAGE_SIZE;
1367                 addr += PAGE_SIZE;
1368                 pgoff++;
1369         }
1370         return 0;
1371 }
1372
1373 #ifdef CONFIG_NUMA
1374 int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *new)
1375 {
1376         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1377         return mpol_set_shared_policy(&SHMEM_I(i)->policy, vma, new);
1378 }
1379
1380 struct mempolicy *
1381 shmem_get_policy(struct vm_area_struct *vma, unsigned long addr)
1382 {
1383         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1384         unsigned long idx;
1385
1386         idx = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1387         return mpol_shared_policy_lookup(&SHMEM_I(i)->policy, idx);
1388 }
1389 #endif
1390
1391 int shmem_lock(struct file *file, int lock, struct user_struct *user)
1392 {
1393         struct inode *inode = file->f_path.dentry->d_inode;
1394         struct shmem_inode_info *info = SHMEM_I(inode);
1395         int retval = -ENOMEM;
1396
1397         spin_lock(&info->lock);
1398         if (lock && !(info->flags & VM_LOCKED)) {
1399                 if (!user_shm_lock(inode->i_size, user))
1400                         goto out_nomem;
1401                 info->flags |= VM_LOCKED;
1402         }
1403         if (!lock && (info->flags & VM_LOCKED) && user) {
1404                 user_shm_unlock(inode->i_size, user);
1405                 info->flags &= ~VM_LOCKED;
1406         }
1407         retval = 0;
1408 out_nomem:
1409         spin_unlock(&info->lock);
1410         return retval;
1411 }
1412
1413 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1414 {
1415         file_accessed(file);
1416         vma->vm_ops = &shmem_vm_ops;
1417         return 0;
1418 }
1419
1420 static struct inode *
1421 shmem_get_inode(struct super_block *sb, int mode, dev_t dev)
1422 {
1423         struct inode *inode;
1424         struct shmem_inode_info *info;
1425         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1426
1427         if (sbinfo->max_inodes) {
1428                 spin_lock(&sbinfo->stat_lock);
1429                 if (!sbinfo->free_inodes) {
1430                         spin_unlock(&sbinfo->stat_lock);
1431                         return NULL;
1432                 }
1433                 sbinfo->free_inodes--;
1434                 spin_unlock(&sbinfo->stat_lock);
1435         }
1436
1437         inode = new_inode(sb);
1438         if (inode) {
1439                 inode->i_mode = mode;
1440                 inode->i_uid = current->fsuid;
1441                 inode->i_gid = current->fsgid;
1442                 inode->i_blocks = 0;
1443                 inode->i_mapping->a_ops = &shmem_aops;
1444                 inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1445                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1446                 inode->i_generation = get_seconds();
1447                 info = SHMEM_I(inode);
1448                 memset(info, 0, (char *)inode - (char *)info);
1449                 spin_lock_init(&info->lock);
1450                 INIT_LIST_HEAD(&info->swaplist);
1451
1452                 switch (mode & S_IFMT) {
1453                 default:
1454                         inode->i_op = &shmem_special_inode_operations;
1455                         init_special_inode(inode, mode, dev);
1456                         break;
1457                 case S_IFREG:
1458                         inode->i_op = &shmem_inode_operations;
1459                         inode->i_fop = &shmem_file_operations;
1460                         mpol_shared_policy_init(&info->policy, sbinfo->policy,
1461                                                         &sbinfo->policy_nodes);
1462                         break;
1463                 case S_IFDIR:
1464                         inc_nlink(inode);
1465                         /* Some things misbehave if size == 0 on a directory */
1466                         inode->i_size = 2 * BOGO_DIRENT_SIZE;
1467                         inode->i_op = &shmem_dir_inode_operations;
1468                         inode->i_fop = &simple_dir_operations;
1469                         break;
1470                 case S_IFLNK:
1471                         /*
1472                          * Must not load anything in the rbtree,
1473                          * mpol_free_shared_policy will not be called.
1474                          */
1475                         mpol_shared_policy_init(&info->policy, MPOL_DEFAULT,
1476                                                 NULL);
1477                         break;
1478                 }
1479         } else if (sbinfo->max_inodes) {
1480                 spin_lock(&sbinfo->stat_lock);
1481                 sbinfo->free_inodes++;
1482                 spin_unlock(&sbinfo->stat_lock);
1483         }
1484         return inode;
1485 }
1486
1487 #ifdef CONFIG_TMPFS
1488 static const struct inode_operations shmem_symlink_inode_operations;
1489 static const struct inode_operations shmem_symlink_inline_operations;
1490
1491 /*
1492  * Normally tmpfs avoids the use of shmem_readpage and shmem_prepare_write;
1493  * but providing them allows a tmpfs file to be used for splice, sendfile, and
1494  * below the loop driver, in the generic fashion that many filesystems support.
1495  */
1496 static int shmem_readpage(struct file *file, struct page *page)
1497 {
1498         struct inode *inode = page->mapping->host;
1499         int error = shmem_getpage(inode, page->index, &page, SGP_CACHE, NULL);
1500         unlock_page(page);
1501         return error;
1502 }
1503
1504 static int
1505 shmem_prepare_write(struct file *file, struct page *page, unsigned offset, unsigned to)
1506 {
1507         struct inode *inode = page->mapping->host;
1508         return shmem_getpage(inode, page->index, &page, SGP_WRITE, NULL);
1509 }
1510
1511 static ssize_t
1512 shmem_file_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
1513 {
1514         struct inode    *inode = file->f_path.dentry->d_inode;
1515         loff_t          pos;
1516         unsigned long   written;
1517         ssize_t         err;
1518
1519         if ((ssize_t) count < 0)
1520                 return -EINVAL;
1521
1522         if (!access_ok(VERIFY_READ, buf, count))
1523                 return -EFAULT;
1524
1525         mutex_lock(&inode->i_mutex);
1526
1527         pos = *ppos;
1528         written = 0;
1529
1530         err = generic_write_checks(file, &pos, &count, 0);
1531         if (err || !count)
1532                 goto out;
1533
1534         err = remove_suid(file->f_path.dentry);
1535         if (err)
1536                 goto out;
1537
1538         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
1539
1540         do {
1541                 struct page *page = NULL;
1542                 unsigned long bytes, index, offset;
1543                 char *kaddr;
1544                 int left;
1545
1546                 offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
1547                 index = pos >> PAGE_CACHE_SHIFT;
1548                 bytes = PAGE_CACHE_SIZE - offset;
1549                 if (bytes > count)
1550                         bytes = count;
1551
1552                 /*
1553                  * We don't hold page lock across copy from user -
1554                  * what would it guard against? - so no deadlock here.
1555                  * But it still may be a good idea to prefault below.
1556                  */
1557
1558                 err = shmem_getpage(inode, index, &page, SGP_WRITE, NULL);
1559                 if (err)
1560                         break;
1561
1562                 left = bytes;
1563                 if (PageHighMem(page)) {
1564                         volatile unsigned char dummy;
1565                         __get_user(dummy, buf);
1566                         __get_user(dummy, buf + bytes - 1);
1567
1568                         kaddr = kmap_atomic(page, KM_USER0);
1569                         left = __copy_from_user_inatomic(kaddr + offset,
1570                                                         buf, bytes);
1571                         kunmap_atomic(kaddr, KM_USER0);
1572                 }
1573                 if (left) {
1574                         kaddr = kmap(page);
1575                         left = __copy_from_user(kaddr + offset, buf, bytes);
1576                         kunmap(page);
1577                 }
1578
1579                 written += bytes;
1580                 count -= bytes;
1581                 pos += bytes;
1582                 buf += bytes;
1583                 if (pos > inode->i_size)
1584                         i_size_write(inode, pos);
1585
1586                 flush_dcache_page(page);
1587                 set_page_dirty(page);
1588                 mark_page_accessed(page);
1589                 page_cache_release(page);
1590
1591                 if (left) {
1592                         pos -= left;
1593                         written -= left;
1594                         err = -EFAULT;
1595                         break;
1596                 }
1597
1598                 /*
1599                  * Our dirty pages are not counted in nr_dirty,
1600                  * and we do not attempt to balance dirty pages.
1601                  */
1602
1603                 cond_resched();
1604         } while (count);
1605
1606         *ppos = pos;
1607         if (written)
1608                 err = written;
1609 out:
1610         mutex_unlock(&inode->i_mutex);
1611         return err;
1612 }
1613
1614 static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
1615 {
1616         struct inode *inode = filp->f_path.dentry->d_inode;
1617         struct address_space *mapping = inode->i_mapping;
1618         unsigned long index, offset;
1619
1620         index = *ppos >> PAGE_CACHE_SHIFT;
1621         offset = *ppos & ~PAGE_CACHE_MASK;
1622
1623         for (;;) {
1624                 struct page *page = NULL;
1625                 unsigned long end_index, nr, ret;
1626                 loff_t i_size = i_size_read(inode);
1627
1628                 end_index = i_size >> PAGE_CACHE_SHIFT;
1629                 if (index > end_index)
1630                         break;
1631                 if (index == end_index) {
1632                         nr = i_size & ~PAGE_CACHE_MASK;
1633                         if (nr <= offset)
1634                                 break;
1635                 }
1636
1637                 desc->error = shmem_getpage(inode, index, &page, SGP_READ, NULL);
1638                 if (desc->error) {
1639                         if (desc->error == -EINVAL)
1640                                 desc->error = 0;
1641                         break;
1642                 }
1643
1644                 /*
1645                  * We must evaluate after, since reads (unlike writes)
1646                  * are called without i_mutex protection against truncate
1647                  */
1648                 nr = PAGE_CACHE_SIZE;
1649                 i_size = i_size_read(inode);
1650                 end_index = i_size >> PAGE_CACHE_SHIFT;
1651                 if (index == end_index) {
1652                         nr = i_size & ~PAGE_CACHE_MASK;
1653                         if (nr <= offset) {
1654                                 if (page)
1655                                         page_cache_release(page);
1656                                 break;
1657                         }
1658                 }
1659                 nr -= offset;
1660
1661                 if (page) {
1662                         /*
1663                          * If users can be writing to this page using arbitrary
1664                          * virtual addresses, take care about potential aliasing
1665                          * before reading the page on the kernel side.
1666                          */
1667                         if (mapping_writably_mapped(mapping))
1668                                 flush_dcache_page(page);
1669                         /*
1670                          * Mark the page accessed if we read the beginning.
1671                          */
1672                         if (!offset)
1673                                 mark_page_accessed(page);
1674                 } else {
1675                         page = ZERO_PAGE(0);
1676                         page_cache_get(page);
1677                 }
1678
1679                 /*
1680                  * Ok, we have the page, and it's up-to-date, so
1681                  * now we can copy it to user space...
1682                  *
1683                  * The actor routine returns how many bytes were actually used..
1684                  * NOTE! This may not be the same as how much of a user buffer
1685                  * we filled up (we may be padding etc), so we can only update
1686                  * "pos" here (the actor routine has to update the user buffer
1687                  * pointers and the remaining count).
1688                  */
1689                 ret = actor(desc, page, offset, nr);
1690                 offset += ret;
1691                 index += offset >> PAGE_CACHE_SHIFT;
1692                 offset &= ~PAGE_CACHE_MASK;
1693
1694                 page_cache_release(page);
1695                 if (ret != nr || !desc->count)
1696                         break;
1697
1698                 cond_resched();
1699         }
1700
1701         *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1702         file_accessed(filp);
1703 }
1704
1705 static ssize_t shmem_file_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
1706 {
1707         read_descriptor_t desc;
1708
1709         if ((ssize_t) count < 0)
1710                 return -EINVAL;
1711         if (!access_ok(VERIFY_WRITE, buf, count))
1712                 return -EFAULT;
1713         if (!count)
1714                 return 0;
1715
1716         desc.written = 0;
1717         desc.count = count;
1718         desc.arg.buf = buf;
1719         desc.error = 0;
1720
1721         do_shmem_file_read(filp, ppos, &desc, file_read_actor);
1722         if (desc.written)
1723                 return desc.written;
1724         return desc.error;
1725 }
1726
1727 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
1728 {
1729         struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
1730
1731         buf->f_type = TMPFS_MAGIC;
1732         buf->f_bsize = PAGE_CACHE_SIZE;
1733         buf->f_namelen = NAME_MAX;
1734         spin_lock(&sbinfo->stat_lock);
1735         if (sbinfo->max_blocks) {
1736                 buf->f_blocks = sbinfo->max_blocks;
1737                 buf->f_bavail = buf->f_bfree = sbinfo->free_blocks;
1738         }
1739         if (sbinfo->max_inodes) {
1740                 buf->f_files = sbinfo->max_inodes;
1741                 buf->f_ffree = sbinfo->free_inodes;
1742         }
1743         /* else leave those fields 0 like simple_statfs */
1744         spin_unlock(&sbinfo->stat_lock);
1745         return 0;
1746 }
1747
1748 /*
1749  * File creation. Allocate an inode, and we're done..
1750  */
1751 static int
1752 shmem_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
1753 {
1754         struct inode *inode = shmem_get_inode(dir->i_sb, mode, dev);
1755         int error = -ENOSPC;
1756
1757         if (inode) {
1758                 error = security_inode_init_security(inode, dir, NULL, NULL,
1759                                                      NULL);
1760                 if (error) {
1761                         if (error != -EOPNOTSUPP) {
1762                                 iput(inode);
1763                                 return error;
1764                         }
1765                 }
1766                 error = shmem_acl_init(inode, dir);
1767                 if (error) {
1768                         iput(inode);
1769                         return error;
1770                 }
1771                 if (dir->i_mode & S_ISGID) {
1772                         inode->i_gid = dir->i_gid;
1773                         if (S_ISDIR(mode))
1774                                 inode->i_mode |= S_ISGID;
1775                 }
1776                 dir->i_size += BOGO_DIRENT_SIZE;
1777                 dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1778                 d_instantiate(dentry, inode);
1779                 dget(dentry); /* Extra count - pin the dentry in core */
1780         }
1781         return error;
1782 }
1783
1784 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, int mode)
1785 {
1786         int error;
1787
1788         if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
1789                 return error;
1790         inc_nlink(dir);
1791         return 0;
1792 }
1793
1794 static int shmem_create(struct inode *dir, struct dentry *dentry, int mode,
1795                 struct nameidata *nd)
1796 {
1797         return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
1798 }
1799
1800 /*
1801  * Link a file..
1802  */
1803 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
1804 {
1805         struct inode *inode = old_dentry->d_inode;
1806         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1807
1808         /*
1809          * No ordinary (disk based) filesystem counts links as inodes;
1810          * but each new link needs a new dentry, pinning lowmem, and
1811          * tmpfs dentries cannot be pruned until they are unlinked.
1812          */
1813         if (sbinfo->max_inodes) {
1814                 spin_lock(&sbinfo->stat_lock);
1815                 if (!sbinfo->free_inodes) {
1816                         spin_unlock(&sbinfo->stat_lock);
1817                         return -ENOSPC;
1818                 }
1819                 sbinfo->free_inodes--;
1820                 spin_unlock(&sbinfo->stat_lock);
1821         }
1822
1823         dir->i_size += BOGO_DIRENT_SIZE;
1824         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1825         inc_nlink(inode);
1826         atomic_inc(&inode->i_count);    /* New dentry reference */
1827         dget(dentry);           /* Extra pinning count for the created dentry */
1828         d_instantiate(dentry, inode);
1829         return 0;
1830 }
1831
1832 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
1833 {
1834         struct inode *inode = dentry->d_inode;
1835
1836         if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode)) {
1837                 struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1838                 if (sbinfo->max_inodes) {
1839                         spin_lock(&sbinfo->stat_lock);
1840                         sbinfo->free_inodes++;
1841                         spin_unlock(&sbinfo->stat_lock);
1842                 }
1843         }
1844
1845         dir->i_size -= BOGO_DIRENT_SIZE;
1846         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1847         drop_nlink(inode);
1848         dput(dentry);   /* Undo the count from "create" - this does all the work */
1849         return 0;
1850 }
1851
1852 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
1853 {
1854         if (!simple_empty(dentry))
1855                 return -ENOTEMPTY;
1856
1857         drop_nlink(dentry->d_inode);
1858         drop_nlink(dir);
1859         return shmem_unlink(dir, dentry);
1860 }
1861
1862 /*
1863  * The VFS layer already does all the dentry stuff for rename,
1864  * we just have to decrement the usage count for the target if
1865  * it exists so that the VFS layer correctly free's it when it
1866  * gets overwritten.
1867  */
1868 static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
1869 {
1870         struct inode *inode = old_dentry->d_inode;
1871         int they_are_dirs = S_ISDIR(inode->i_mode);
1872
1873         if (!simple_empty(new_dentry))
1874                 return -ENOTEMPTY;
1875
1876         if (new_dentry->d_inode) {
1877                 (void) shmem_unlink(new_dir, new_dentry);
1878                 if (they_are_dirs)
1879                         drop_nlink(old_dir);
1880         } else if (they_are_dirs) {
1881                 drop_nlink(old_dir);
1882                 inc_nlink(new_dir);
1883         }
1884
1885         old_dir->i_size -= BOGO_DIRENT_SIZE;
1886         new_dir->i_size += BOGO_DIRENT_SIZE;
1887         old_dir->i_ctime = old_dir->i_mtime =
1888         new_dir->i_ctime = new_dir->i_mtime =
1889         inode->i_ctime = CURRENT_TIME;
1890         return 0;
1891 }
1892
1893 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
1894 {
1895         int error;
1896         int len;
1897         struct inode *inode;
1898         struct page *page = NULL;
1899         char *kaddr;
1900         struct shmem_inode_info *info;
1901
1902         len = strlen(symname) + 1;
1903         if (len > PAGE_CACHE_SIZE)
1904                 return -ENAMETOOLONG;
1905
1906         inode = shmem_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0);
1907         if (!inode)
1908                 return -ENOSPC;
1909
1910         error = security_inode_init_security(inode, dir, NULL, NULL,
1911                                              NULL);
1912         if (error) {
1913                 if (error != -EOPNOTSUPP) {
1914                         iput(inode);
1915                         return error;
1916                 }
1917                 error = 0;
1918         }
1919
1920         info = SHMEM_I(inode);
1921         inode->i_size = len-1;
1922         if (len <= (char *)inode - (char *)info) {
1923                 /* do it inline */
1924                 memcpy(info, symname, len);
1925                 inode->i_op = &shmem_symlink_inline_operations;
1926         } else {
1927                 error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
1928                 if (error) {
1929                         iput(inode);
1930                         return error;
1931                 }
1932                 inode->i_op = &shmem_symlink_inode_operations;
1933                 kaddr = kmap_atomic(page, KM_USER0);
1934                 memcpy(kaddr, symname, len);
1935                 kunmap_atomic(kaddr, KM_USER0);
1936                 set_page_dirty(page);
1937                 page_cache_release(page);
1938         }
1939         if (dir->i_mode & S_ISGID)
1940                 inode->i_gid = dir->i_gid;
1941         dir->i_size += BOGO_DIRENT_SIZE;
1942         dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1943         d_instantiate(dentry, inode);
1944         dget(dentry);
1945         return 0;
1946 }
1947
1948 static void *shmem_follow_link_inline(struct dentry *dentry, struct nameidata *nd)
1949 {
1950         nd_set_link(nd, (char *)SHMEM_I(dentry->d_inode));
1951         return NULL;
1952 }
1953
1954 static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
1955 {
1956         struct page *page = NULL;
1957         int res = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
1958         nd_set_link(nd, res ? ERR_PTR(res) : kmap(page));
1959         return page;
1960 }
1961
1962 static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
1963 {
1964         if (!IS_ERR(nd_get_link(nd))) {
1965                 struct page *page = cookie;
1966                 kunmap(page);
1967                 mark_page_accessed(page);
1968                 page_cache_release(page);
1969         }
1970 }
1971
1972 static const struct inode_operations shmem_symlink_inline_operations = {
1973         .readlink       = generic_readlink,
1974         .follow_link    = shmem_follow_link_inline,
1975 };
1976
1977 static const struct inode_operations shmem_symlink_inode_operations = {
1978         .truncate       = shmem_truncate,
1979         .readlink       = generic_readlink,
1980         .follow_link    = shmem_follow_link,
1981         .put_link       = shmem_put_link,
1982 };
1983
1984 #ifdef CONFIG_TMPFS_POSIX_ACL
1985 /**
1986  * Superblocks without xattr inode operations will get security.* xattr
1987  * support from the VFS "for free". As soon as we have any other xattrs
1988  * like ACLs, we also need to implement the security.* handlers at
1989  * filesystem level, though.
1990  */
1991
1992 static size_t shmem_xattr_security_list(struct inode *inode, char *list,
1993                                         size_t list_len, const char *name,
1994                                         size_t name_len)
1995 {
1996         return security_inode_listsecurity(inode, list, list_len);
1997 }
1998
1999 static int shmem_xattr_security_get(struct inode *inode, const char *name,
2000                                     void *buffer, size_t size)
2001 {
2002         if (strcmp(name, "") == 0)
2003                 return -EINVAL;
2004         return security_inode_getsecurity(inode, name, buffer, size,
2005                                           -EOPNOTSUPP);
2006 }
2007
2008 static int shmem_xattr_security_set(struct inode *inode, const char *name,
2009                                     const void *value, size_t size, int flags)
2010 {
2011         if (strcmp(name, "") == 0)
2012                 return -EINVAL;
2013         return security_inode_setsecurity(inode, name, value, size, flags);
2014 }
2015
2016 static struct xattr_handler shmem_xattr_security_handler = {
2017         .prefix = XATTR_SECURITY_PREFIX,
2018         .list   = shmem_xattr_security_list,
2019         .get    = shmem_xattr_security_get,
2020         .set    = shmem_xattr_security_set,
2021 };
2022
2023 static struct xattr_handler *shmem_xattr_handlers[] = {
2024         &shmem_xattr_acl_access_handler,
2025         &shmem_xattr_acl_default_handler,
2026         &shmem_xattr_security_handler,
2027         NULL
2028 };
2029 #endif
2030
2031 static struct dentry *shmem_get_parent(struct dentry *child)
2032 {
2033         return ERR_PTR(-ESTALE);
2034 }
2035
2036 static int shmem_match(struct inode *ino, void *vfh)
2037 {
2038         __u32 *fh = vfh;
2039         __u64 inum = fh[2];
2040         inum = (inum << 32) | fh[1];
2041         return ino->i_ino == inum && fh[0] == ino->i_generation;
2042 }
2043
2044 static struct dentry *shmem_get_dentry(struct super_block *sb, void *vfh)
2045 {
2046         struct dentry *de = NULL;
2047         struct inode *inode;
2048         __u32 *fh = vfh;
2049         __u64 inum = fh[2];
2050         inum = (inum << 32) | fh[1];
2051
2052         inode = ilookup5(sb, (unsigned long)(inum+fh[0]), shmem_match, vfh);
2053         if (inode) {
2054                 de = d_find_alias(inode);
2055                 iput(inode);
2056         }
2057
2058         return de? de: ERR_PTR(-ESTALE);
2059 }
2060
2061 static struct dentry *shmem_decode_fh(struct super_block *sb, __u32 *fh,
2062                 int len, int type,
2063                 int (*acceptable)(void *context, struct dentry *de),
2064                 void *context)
2065 {
2066         if (len < 3)
2067                 return ERR_PTR(-ESTALE);
2068
2069         return sb->s_export_op->find_exported_dentry(sb, fh, NULL, acceptable,
2070                                                         context);
2071 }
2072
2073 static int shmem_encode_fh(struct dentry *dentry, __u32 *fh, int *len,
2074                                 int connectable)
2075 {
2076         struct inode *inode = dentry->d_inode;
2077
2078         if (*len < 3)
2079                 return 255;
2080
2081         if (hlist_unhashed(&inode->i_hash)) {
2082                 /* Unfortunately insert_inode_hash is not idempotent,
2083                  * so as we hash inodes here rather than at creation
2084                  * time, we need a lock to ensure we only try
2085                  * to do it once
2086                  */
2087                 static DEFINE_SPINLOCK(lock);
2088                 spin_lock(&lock);
2089                 if (hlist_unhashed(&inode->i_hash))
2090                         __insert_inode_hash(inode,
2091                                             inode->i_ino + inode->i_generation);
2092                 spin_unlock(&lock);
2093         }
2094
2095         fh[0] = inode->i_generation;
2096         fh[1] = inode->i_ino;
2097         fh[2] = ((__u64)inode->i_ino) >> 32;
2098
2099         *len = 3;
2100         return 1;
2101 }
2102
2103 static struct export_operations shmem_export_ops = {
2104         .get_parent     = shmem_get_parent,
2105         .get_dentry     = shmem_get_dentry,
2106         .encode_fh      = shmem_encode_fh,
2107         .decode_fh      = shmem_decode_fh,
2108 };
2109
2110 static int shmem_parse_options(char *options, int *mode, uid_t *uid,
2111         gid_t *gid, unsigned long *blocks, unsigned long *inodes,
2112         int *policy, nodemask_t *policy_nodes)
2113 {
2114         char *this_char, *value, *rest;
2115
2116         while (options != NULL) {
2117                 this_char = options;
2118                 for (;;) {
2119                         /*
2120                          * NUL-terminate this option: unfortunately,
2121                          * mount options form a comma-separated list,
2122                          * but mpol's nodelist may also contain commas.
2123                          */
2124                         options = strchr(options, ',');
2125                         if (options == NULL)
2126                                 break;
2127                         options++;
2128                         if (!isdigit(*options)) {
2129                                 options[-1] = '\0';
2130                                 break;
2131                         }
2132                 }
2133                 if (!*this_char)
2134                         continue;
2135                 if ((value = strchr(this_char,'=')) != NULL) {
2136                         *value++ = 0;
2137                 } else {
2138                         printk(KERN_ERR
2139                             "tmpfs: No value for mount option '%s'\n",
2140                             this_char);
2141                         return 1;
2142                 }
2143
2144                 if (!strcmp(this_char,"size")) {
2145                         unsigned long long size;
2146                         size = memparse(value,&rest);
2147                         if (*rest == '%') {
2148                                 size <<= PAGE_SHIFT;
2149                                 size *= totalram_pages;
2150                                 do_div(size, 100);
2151                                 rest++;
2152                         }
2153                         if (*rest)
2154                                 goto bad_val;
2155                         *blocks = size >> PAGE_CACHE_SHIFT;
2156                 } else if (!strcmp(this_char,"nr_blocks")) {
2157                         *blocks = memparse(value,&rest);
2158                         if (*rest)
2159                                 goto bad_val;
2160                 } else if (!strcmp(this_char,"nr_inodes")) {
2161                         *inodes = memparse(value,&rest);
2162                         if (*rest)
2163                                 goto bad_val;
2164                 } else if (!strcmp(this_char,"mode")) {
2165                         if (!mode)
2166                                 continue;
2167                         *mode = simple_strtoul(value,&rest,8);
2168                         if (*rest)
2169                                 goto bad_val;
2170                 } else if (!strcmp(this_char,"uid")) {
2171                         if (!uid)
2172                                 continue;
2173                         *uid = simple_strtoul(value,&rest,0);
2174                         if (*rest)
2175                                 goto bad_val;
2176                 } else if (!strcmp(this_char,"gid")) {
2177                         if (!gid)
2178                                 continue;
2179                         *gid = simple_strtoul(value,&rest,0);
2180                         if (*rest)
2181                                 goto bad_val;
2182                 } else if (!strcmp(this_char,"mpol")) {
2183                         if (shmem_parse_mpol(value,policy,policy_nodes))
2184                                 goto bad_val;
2185                 } else {
2186                         printk(KERN_ERR "tmpfs: Bad mount option %s\n",
2187                                this_char);
2188                         return 1;
2189                 }
2190         }
2191         return 0;
2192
2193 bad_val:
2194         printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
2195                value, this_char);
2196         return 1;
2197
2198 }
2199
2200 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2201 {
2202         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2203         unsigned long max_blocks = sbinfo->max_blocks;
2204         unsigned long max_inodes = sbinfo->max_inodes;
2205         int policy = sbinfo->policy;
2206         nodemask_t policy_nodes = sbinfo->policy_nodes;
2207         unsigned long blocks;
2208         unsigned long inodes;
2209         int error = -EINVAL;
2210
2211         if (shmem_parse_options(data, NULL, NULL, NULL, &max_blocks,
2212                                 &max_inodes, &policy, &policy_nodes))
2213                 return error;
2214
2215         spin_lock(&sbinfo->stat_lock);
2216         blocks = sbinfo->max_blocks - sbinfo->free_blocks;
2217         inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2218         if (max_blocks < blocks)
2219                 goto out;
2220         if (max_inodes < inodes)
2221                 goto out;
2222         /*
2223          * Those tests also disallow limited->unlimited while any are in
2224          * use, so i_blocks will always be zero when max_blocks is zero;
2225          * but we must separately disallow unlimited->limited, because
2226          * in that case we have no record of how much is already in use.
2227          */
2228         if (max_blocks && !sbinfo->max_blocks)
2229                 goto out;
2230         if (max_inodes && !sbinfo->max_inodes)
2231                 goto out;
2232
2233         error = 0;
2234         sbinfo->max_blocks  = max_blocks;
2235         sbinfo->free_blocks = max_blocks - blocks;
2236         sbinfo->max_inodes  = max_inodes;
2237         sbinfo->free_inodes = max_inodes - inodes;
2238         sbinfo->policy = policy;
2239         sbinfo->policy_nodes = policy_nodes;
2240 out:
2241         spin_unlock(&sbinfo->stat_lock);
2242         return error;
2243 }
2244 #endif
2245
2246 static void shmem_put_super(struct super_block *sb)
2247 {
2248         kfree(sb->s_fs_info);
2249         sb->s_fs_info = NULL;
2250 }
2251
2252 static int shmem_fill_super(struct super_block *sb,
2253                             void *data, int silent)
2254 {
2255         struct inode *inode;
2256         struct dentry *root;
2257         int mode   = S_IRWXUGO | S_ISVTX;
2258         uid_t uid = current->fsuid;
2259         gid_t gid = current->fsgid;
2260         int err = -ENOMEM;
2261         struct shmem_sb_info *sbinfo;
2262         unsigned long blocks = 0;
2263         unsigned long inodes = 0;
2264         int policy = MPOL_DEFAULT;
2265         nodemask_t policy_nodes = node_online_map;
2266
2267 #ifdef CONFIG_TMPFS
2268         /*
2269          * Per default we only allow half of the physical ram per
2270          * tmpfs instance, limiting inodes to one per page of lowmem;
2271          * but the internal instance is left unlimited.
2272          */
2273         if (!(sb->s_flags & MS_NOUSER)) {
2274                 blocks = totalram_pages / 2;
2275                 inodes = totalram_pages - totalhigh_pages;
2276                 if (inodes > blocks)
2277                         inodes = blocks;
2278                 if (shmem_parse_options(data, &mode, &uid, &gid, &blocks,
2279                                         &inodes, &policy, &policy_nodes))
2280                         return -EINVAL;
2281         }
2282         sb->s_export_op = &shmem_export_ops;
2283 #else
2284         sb->s_flags |= MS_NOUSER;
2285 #endif
2286
2287         /* Round up to L1_CACHE_BYTES to resist false sharing */
2288         sbinfo = kmalloc(max((int)sizeof(struct shmem_sb_info),
2289                                 L1_CACHE_BYTES), GFP_KERNEL);
2290         if (!sbinfo)
2291                 return -ENOMEM;
2292
2293         spin_lock_init(&sbinfo->stat_lock);
2294         sbinfo->max_blocks = blocks;
2295         sbinfo->free_blocks = blocks;
2296         sbinfo->max_inodes = inodes;
2297         sbinfo->free_inodes = inodes;
2298         sbinfo->policy = policy;
2299         sbinfo->policy_nodes = policy_nodes;
2300
2301         sb->s_fs_info = sbinfo;
2302         sb->s_maxbytes = SHMEM_MAX_BYTES;
2303         sb->s_blocksize = PAGE_CACHE_SIZE;
2304         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
2305         sb->s_magic = TMPFS_MAGIC;
2306         sb->s_op = &shmem_ops;
2307         sb->s_time_gran = 1;
2308 #ifdef CONFIG_TMPFS_POSIX_ACL
2309         sb->s_xattr = shmem_xattr_handlers;
2310         sb->s_flags |= MS_POSIXACL;
2311 #endif
2312
2313         inode = shmem_get_inode(sb, S_IFDIR | mode, 0);
2314         if (!inode)
2315                 goto failed;
2316         inode->i_uid = uid;
2317         inode->i_gid = gid;
2318         root = d_alloc_root(inode);
2319         if (!root)
2320                 goto failed_iput;
2321         sb->s_root = root;
2322         return 0;
2323
2324 failed_iput:
2325         iput(inode);
2326 failed:
2327         shmem_put_super(sb);
2328         return err;
2329 }
2330
2331 static struct kmem_cache *shmem_inode_cachep;
2332
2333 static struct inode *shmem_alloc_inode(struct super_block *sb)
2334 {
2335         struct shmem_inode_info *p;
2336         p = (struct shmem_inode_info *)kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
2337         if (!p)
2338                 return NULL;
2339         return &p->vfs_inode;
2340 }
2341
2342 static void shmem_destroy_inode(struct inode *inode)
2343 {
2344         if ((inode->i_mode & S_IFMT) == S_IFREG) {
2345                 /* only struct inode is valid if it's an inline symlink */
2346                 mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2347         }
2348         shmem_acl_destroy_inode(inode);
2349         kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2350 }
2351
2352 static void init_once(void *foo, struct kmem_cache *cachep,
2353                       unsigned long flags)
2354 {
2355         struct shmem_inode_info *p = (struct shmem_inode_info *) foo;
2356
2357         inode_init_once(&p->vfs_inode);
2358 #ifdef CONFIG_TMPFS_POSIX_ACL
2359         p->i_acl = NULL;
2360         p->i_default_acl = NULL;
2361 #endif
2362 }
2363
2364 static int init_inodecache(void)
2365 {
2366         shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
2367                                 sizeof(struct shmem_inode_info),
2368                                 0, 0, init_once, NULL);
2369         if (shmem_inode_cachep == NULL)
2370                 return -ENOMEM;
2371         return 0;
2372 }
2373
2374 static void destroy_inodecache(void)
2375 {
2376         kmem_cache_destroy(shmem_inode_cachep);
2377 }
2378
2379 static const struct address_space_operations shmem_aops = {
2380         .writepage      = shmem_writepage,
2381         .set_page_dirty = __set_page_dirty_no_writeback,
2382 #ifdef CONFIG_TMPFS
2383         .readpage       = shmem_readpage,
2384         .prepare_write  = shmem_prepare_write,
2385         .commit_write   = simple_commit_write,
2386 #endif
2387         .migratepage    = migrate_page,
2388 };
2389
2390 static const struct file_operations shmem_file_operations = {
2391         .mmap           = shmem_mmap,
2392 #ifdef CONFIG_TMPFS
2393         .llseek         = generic_file_llseek,
2394         .read           = shmem_file_read,
2395         .write          = shmem_file_write,
2396         .fsync          = simple_sync_file,
2397         .splice_read    = generic_file_splice_read,
2398         .splice_write   = generic_file_splice_write,
2399 #endif
2400 };
2401
2402 static const struct inode_operations shmem_inode_operations = {
2403         .truncate       = shmem_truncate,
2404         .setattr        = shmem_notify_change,
2405         .truncate_range = shmem_truncate_range,
2406 #ifdef CONFIG_TMPFS_POSIX_ACL
2407         .setxattr       = generic_setxattr,
2408         .getxattr       = generic_getxattr,
2409         .listxattr      = generic_listxattr,
2410         .removexattr    = generic_removexattr,
2411         .permission     = shmem_permission,
2412 #endif
2413
2414 };
2415
2416 static const struct inode_operations shmem_dir_inode_operations = {
2417 #ifdef CONFIG_TMPFS
2418         .create         = shmem_create,
2419         .lookup         = simple_lookup,
2420         .link           = shmem_link,
2421         .unlink         = shmem_unlink,
2422         .symlink        = shmem_symlink,
2423         .mkdir          = shmem_mkdir,
2424         .rmdir          = shmem_rmdir,
2425         .mknod          = shmem_mknod,
2426         .rename         = shmem_rename,
2427 #endif
2428 #ifdef CONFIG_TMPFS_POSIX_ACL
2429         .setattr        = shmem_notify_change,
2430         .setxattr       = generic_setxattr,
2431         .getxattr       = generic_getxattr,
2432         .listxattr      = generic_listxattr,
2433         .removexattr    = generic_removexattr,
2434         .permission     = shmem_permission,
2435 #endif
2436 };
2437
2438 static const struct inode_operations shmem_special_inode_operations = {
2439 #ifdef CONFIG_TMPFS_POSIX_ACL
2440         .setattr        = shmem_notify_change,
2441         .setxattr       = generic_setxattr,
2442         .getxattr       = generic_getxattr,
2443         .listxattr      = generic_listxattr,
2444         .removexattr    = generic_removexattr,
2445         .permission     = shmem_permission,
2446 #endif
2447 };
2448
2449 static const struct super_operations shmem_ops = {
2450         .alloc_inode    = shmem_alloc_inode,
2451         .destroy_inode  = shmem_destroy_inode,
2452 #ifdef CONFIG_TMPFS
2453         .statfs         = shmem_statfs,
2454         .remount_fs     = shmem_remount_fs,
2455 #endif
2456         .delete_inode   = shmem_delete_inode,
2457         .drop_inode     = generic_delete_inode,
2458         .put_super      = shmem_put_super,
2459 };
2460
2461 static struct vm_operations_struct shmem_vm_ops = {
2462         .nopage         = shmem_nopage,
2463         .populate       = shmem_populate,
2464 #ifdef CONFIG_NUMA
2465         .set_policy     = shmem_set_policy,
2466         .get_policy     = shmem_get_policy,
2467 #endif
2468 };
2469
2470
2471 static int shmem_get_sb(struct file_system_type *fs_type,
2472         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
2473 {
2474         return get_sb_nodev(fs_type, flags, data, shmem_fill_super, mnt);
2475 }
2476
2477 static struct file_system_type tmpfs_fs_type = {
2478         .owner          = THIS_MODULE,
2479         .name           = "tmpfs",
2480         .get_sb         = shmem_get_sb,
2481         .kill_sb        = kill_litter_super,
2482 };
2483 static struct vfsmount *shm_mnt;
2484
2485 static int __init init_tmpfs(void)
2486 {
2487         int error;
2488
2489         error = init_inodecache();
2490         if (error)
2491                 goto out3;
2492
2493         error = register_filesystem(&tmpfs_fs_type);
2494         if (error) {
2495                 printk(KERN_ERR "Could not register tmpfs\n");
2496                 goto out2;
2497         }
2498
2499         shm_mnt = vfs_kern_mount(&tmpfs_fs_type, MS_NOUSER,
2500                                 tmpfs_fs_type.name, NULL);
2501         if (IS_ERR(shm_mnt)) {
2502                 error = PTR_ERR(shm_mnt);
2503                 printk(KERN_ERR "Could not kern_mount tmpfs\n");
2504                 goto out1;
2505         }
2506         return 0;
2507
2508 out1:
2509         unregister_filesystem(&tmpfs_fs_type);
2510 out2:
2511         destroy_inodecache();
2512 out3:
2513         shm_mnt = ERR_PTR(error);
2514         return error;
2515 }
2516 module_init(init_tmpfs)
2517
2518 /*
2519  * shmem_file_setup - get an unlinked file living in tmpfs
2520  *
2521  * @name: name for dentry (to be seen in /proc/<pid>/maps
2522  * @size: size to be set for the file
2523  *
2524  */
2525 struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags)
2526 {
2527         int error;
2528         struct file *file;
2529         struct inode *inode;
2530         struct dentry *dentry, *root;
2531         struct qstr this;
2532
2533         if (IS_ERR(shm_mnt))
2534                 return (void *)shm_mnt;
2535
2536         if (size < 0 || size > SHMEM_MAX_BYTES)
2537                 return ERR_PTR(-EINVAL);
2538
2539         if (shmem_acct_size(flags, size))
2540                 return ERR_PTR(-ENOMEM);
2541
2542         error = -ENOMEM;
2543         this.name = name;
2544         this.len = strlen(name);
2545         this.hash = 0; /* will go */
2546         root = shm_mnt->mnt_root;
2547         dentry = d_alloc(root, &this);
2548         if (!dentry)
2549                 goto put_memory;
2550
2551         error = -ENFILE;
2552         file = get_empty_filp();
2553         if (!file)
2554                 goto put_dentry;
2555
2556         error = -ENOSPC;
2557         inode = shmem_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0);
2558         if (!inode)
2559                 goto close_file;
2560
2561         SHMEM_I(inode)->flags = flags & VM_ACCOUNT;
2562         d_instantiate(dentry, inode);
2563         inode->i_size = size;
2564         inode->i_nlink = 0;     /* It is unlinked */
2565         file->f_path.mnt = mntget(shm_mnt);
2566         file->f_path.dentry = dentry;
2567         file->f_mapping = inode->i_mapping;
2568         file->f_op = &shmem_file_operations;
2569         file->f_mode = FMODE_WRITE | FMODE_READ;
2570         return file;
2571
2572 close_file:
2573         put_filp(file);
2574 put_dentry:
2575         dput(dentry);
2576 put_memory:
2577         shmem_unacct_size(flags, size);
2578         return ERR_PTR(error);
2579 }
2580
2581 /*
2582  * shmem_zero_setup - setup a shared anonymous mapping
2583  *
2584  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
2585  */
2586 int shmem_zero_setup(struct vm_area_struct *vma)
2587 {
2588         struct file *file;
2589         loff_t size = vma->vm_end - vma->vm_start;
2590
2591         file = shmem_file_setup("dev/zero", size, vma->vm_flags);
2592         if (IS_ERR(file))
2593                 return PTR_ERR(file);
2594
2595         if (vma->vm_file)
2596                 fput(vma->vm_file);
2597         vma->vm_file = file;
2598         vma->vm_ops = &shmem_vm_ops;
2599         return 0;
2600 }