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
  53 #include <asm/uaccess.h>
  54 #include <asm/div64.h>
  55 #include <asm/pgtable.h>
  56
  57 /* This magic number is used in glibc for posix shared memory */
  58 #define TMPFS_MAGIC     0x01021994
  59
  60 #define ENTRIES_PER_PAGE (PAGE_CACHE_SIZE/sizeof(unsigned long))
  61 #define ENTRIES_PER_PAGEPAGE (ENTRIES_PER_PAGE*ENTRIES_PER_PAGE)
  62 #define BLOCKS_PER_PAGE  (PAGE_CACHE_SIZE/512)
  63
  64 #define SHMEM_MAX_INDEX  (SHMEM_NR_DIRECT + (ENTRIES_PER_PAGEPAGE/2) * (ENTRIES_PER_PAGE+1))
  65 #define SHMEM_MAX_BYTES  ((unsigned long long)SHMEM_MAX_INDEX << PAGE_CACHE_SHIFT)
  66
  67 #define VM_ACCT(size)    (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
  68
  69 /* info->flags needs VM_flags to handle pagein/truncate races efficiently */
  70 #define SHMEM_PAGEIN     VM_READ
  71 #define SHMEM_TRUNCATE   VM_WRITE
  72
  73 /* Definition to limit shmem_truncate's steps between cond_rescheds */
  74 #define LATENCY_LIMIT    64
  75
  76 /* Pretend that each entry is of this size in directory's i_size */
  77 #define BOGO_DIRENT_SIZE 20
  78
  79 /* Flag allocation requirements to shmem_getpage and shmem_swp_alloc */
  80 enum sgp_type {
  81         SGP_QUICK,      /* don't try more than file page cache lookup */
  82         SGP_READ,       /* don't exceed i_size, don't allocate page */
  83         SGP_CACHE,      /* don't exceed i_size, may allocate page */
  84         SGP_WRITE,      /* may exceed i_size, may allocate page */
  85         SGP_FAULT,      /* same as SGP_CACHE, return with page locked */
  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          * Mobility flags are masked out as swap vectors cannot move
  99          */
 100         return alloc_pages((gfp_mask & ~GFP_MOVABLE_MASK) | __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_states[N_HIGH_MEMORY]))
 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                 /*
1000                  * Default to online nodes with memory if no nodelist
1001                  */
1002                 if (!nodelist)
1003                         *policy_nodes = node_states[N_HIGH_MEMORY];
1004                 err = 0;
1005         }
1006 out:
1007         /* Restore string for error message */
1008         if (nodelist)
1009                 *--nodelist = ':';
1010         return err;
1011 }
1012
1013 static struct page *shmem_swapin_async(struct shared_policy *p,
1014                                        swp_entry_t entry, unsigned long idx)
1015 {
1016         struct page *page;
1017         struct vm_area_struct pvma;
1018
1019         /* Create a pseudo vma that just contains the policy */
1020         memset(&pvma, 0, sizeof(struct vm_area_struct));
1021         pvma.vm_end = PAGE_SIZE;
1022         pvma.vm_pgoff = idx;
1023         pvma.vm_policy = mpol_shared_policy_lookup(p, idx);
1024         page = read_swap_cache_async(entry, &pvma, 0);
1025         mpol_free(pvma.vm_policy);
1026         return page;
1027 }
1028
1029 struct page *shmem_swapin(struct shmem_inode_info *info, swp_entry_t entry,
1030                           unsigned long idx)
1031 {
1032         struct shared_policy *p = &info->policy;
1033         int i, num;
1034         struct page *page;
1035         unsigned long offset;
1036
1037         num = valid_swaphandles(entry, &offset);
1038         for (i = 0; i < num; offset++, i++) {
1039                 page = shmem_swapin_async(p,
1040                                 swp_entry(swp_type(entry), offset), idx);
1041                 if (!page)
1042                         break;
1043                 page_cache_release(page);
1044         }
1045         lru_add_drain();        /* Push any new pages onto the LRU now */
1046         return shmem_swapin_async(p, entry, idx);
1047 }
1048
1049 static struct page *
1050 shmem_alloc_page(gfp_t gfp, struct shmem_inode_info *info,
1051                  unsigned long idx)
1052 {
1053         struct vm_area_struct pvma;
1054         struct page *page;
1055
1056         memset(&pvma, 0, sizeof(struct vm_area_struct));
1057         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx);
1058         pvma.vm_pgoff = idx;
1059         pvma.vm_end = PAGE_SIZE;
1060         page = alloc_page_vma(gfp | __GFP_ZERO, &pvma, 0);
1061         mpol_free(pvma.vm_policy);
1062         return page;
1063 }
1064 #else
1065 static inline int shmem_parse_mpol(char *value, int *policy,
1066                                                 nodemask_t *policy_nodes)
1067 {
1068         return 1;
1069 }
1070
1071 static inline struct page *
1072 shmem_swapin(struct shmem_inode_info *info,swp_entry_t entry,unsigned long idx)
1073 {
1074         swapin_readahead(entry, 0, NULL);
1075         return read_swap_cache_async(entry, NULL, 0);
1076 }
1077
1078 static inline struct page *
1079 shmem_alloc_page(gfp_t gfp,struct shmem_inode_info *info, unsigned long idx)
1080 {
1081         return alloc_page(gfp | __GFP_ZERO);
1082 }
1083 #endif
1084
1085 /*
1086  * shmem_getpage - either get the page from swap or allocate a new one
1087  *
1088  * If we allocate a new one we do not mark it dirty. That's up to the
1089  * vm. If we swap it in we mark it dirty since we also free the swap
1090  * entry since a page cannot live in both the swap and page cache
1091  */
1092 static int shmem_getpage(struct inode *inode, unsigned long idx,
1093                         struct page **pagep, enum sgp_type sgp, int *type)
1094 {
1095         struct address_space *mapping = inode->i_mapping;
1096         struct shmem_inode_info *info = SHMEM_I(inode);
1097         struct shmem_sb_info *sbinfo;
1098         struct page *filepage = *pagep;
1099         struct page *swappage;
1100         swp_entry_t *entry;
1101         swp_entry_t swap;
1102         int error;
1103
1104         if (idx >= SHMEM_MAX_INDEX)
1105                 return -EFBIG;
1106
1107         if (type)
1108                 *type = 0;
1109
1110         /*
1111          * Normally, filepage is NULL on entry, and either found
1112          * uptodate immediately, or allocated and zeroed, or read
1113          * in under swappage, which is then assigned to filepage.
1114          * But shmem_readpage and shmem_write_begin pass in a locked
1115          * filepage, which may be found not uptodate by other callers
1116          * too, and may need to be copied from the swappage read in.
1117          */
1118 repeat:
1119         if (!filepage)
1120                 filepage = find_lock_page(mapping, idx);
1121         if (filepage && PageUptodate(filepage))
1122                 goto done;
1123         error = 0;
1124         if (sgp == SGP_QUICK)
1125                 goto failed;
1126
1127         spin_lock(&info->lock);
1128         shmem_recalc_inode(inode);
1129         entry = shmem_swp_alloc(info, idx, sgp);
1130         if (IS_ERR(entry)) {
1131                 spin_unlock(&info->lock);
1132                 error = PTR_ERR(entry);
1133                 goto failed;
1134         }
1135         swap = *entry;
1136
1137         if (swap.val) {
1138                 /* Look it up and read it in.. */
1139                 swappage = lookup_swap_cache(swap);
1140                 if (!swappage) {
1141                         shmem_swp_unmap(entry);
1142                         /* here we actually do the io */
1143                         if (type && !(*type & VM_FAULT_MAJOR)) {
1144                                 __count_vm_event(PGMAJFAULT);
1145                                 *type |= VM_FAULT_MAJOR;
1146                         }
1147                         spin_unlock(&info->lock);
1148                         swappage = shmem_swapin(info, swap, idx);
1149                         if (!swappage) {
1150                                 spin_lock(&info->lock);
1151                                 entry = shmem_swp_alloc(info, idx, sgp);
1152                                 if (IS_ERR(entry))
1153                                         error = PTR_ERR(entry);
1154                                 else {
1155                                         if (entry->val == swap.val)
1156                                                 error = -ENOMEM;
1157                                         shmem_swp_unmap(entry);
1158                                 }
1159                                 spin_unlock(&info->lock);
1160                                 if (error)
1161                                         goto failed;
1162                                 goto repeat;
1163                         }
1164                         wait_on_page_locked(swappage);
1165                         page_cache_release(swappage);
1166                         goto repeat;
1167                 }
1168
1169                 /* We have to do this with page locked to prevent races */
1170                 if (TestSetPageLocked(swappage)) {
1171                         shmem_swp_unmap(entry);
1172                         spin_unlock(&info->lock);
1173                         wait_on_page_locked(swappage);
1174                         page_cache_release(swappage);
1175                         goto repeat;
1176                 }
1177                 if (PageWriteback(swappage)) {
1178                         shmem_swp_unmap(entry);
1179                         spin_unlock(&info->lock);
1180                         wait_on_page_writeback(swappage);
1181                         unlock_page(swappage);
1182                         page_cache_release(swappage);
1183                         goto repeat;
1184                 }
1185                 if (!PageUptodate(swappage)) {
1186                         shmem_swp_unmap(entry);
1187                         spin_unlock(&info->lock);
1188                         unlock_page(swappage);
1189                         page_cache_release(swappage);
1190                         error = -EIO;
1191                         goto failed;
1192                 }
1193
1194                 if (filepage) {
1195                         shmem_swp_set(info, entry, 0);
1196                         shmem_swp_unmap(entry);
1197                         delete_from_swap_cache(swappage);
1198                         spin_unlock(&info->lock);
1199                         copy_highpage(filepage, swappage);
1200                         unlock_page(swappage);
1201                         page_cache_release(swappage);
1202                         flush_dcache_page(filepage);
1203                         SetPageUptodate(filepage);
1204                         set_page_dirty(filepage);
1205                         swap_free(swap);
1206                 } else if (!(error = move_from_swap_cache(
1207                                 swappage, idx, mapping))) {
1208                         info->flags |= SHMEM_PAGEIN;
1209                         shmem_swp_set(info, entry, 0);
1210                         shmem_swp_unmap(entry);
1211                         spin_unlock(&info->lock);
1212                         filepage = swappage;
1213                         swap_free(swap);
1214                 } else {
1215                         shmem_swp_unmap(entry);
1216                         spin_unlock(&info->lock);
1217                         unlock_page(swappage);
1218                         page_cache_release(swappage);
1219                         if (error == -ENOMEM) {
1220                                 /* let kswapd refresh zone for GFP_ATOMICs */
1221                                 congestion_wait(WRITE, HZ/50);
1222                         }
1223                         goto repeat;
1224                 }
1225         } else if (sgp == SGP_READ && !filepage) {
1226                 shmem_swp_unmap(entry);
1227                 filepage = find_get_page(mapping, idx);
1228                 if (filepage &&
1229                     (!PageUptodate(filepage) || TestSetPageLocked(filepage))) {
1230                         spin_unlock(&info->lock);
1231                         wait_on_page_locked(filepage);
1232                         page_cache_release(filepage);
1233                         filepage = NULL;
1234                         goto repeat;
1235                 }
1236                 spin_unlock(&info->lock);
1237         } else {
1238                 shmem_swp_unmap(entry);
1239                 sbinfo = SHMEM_SB(inode->i_sb);
1240                 if (sbinfo->max_blocks) {
1241                         spin_lock(&sbinfo->stat_lock);
1242                         if (sbinfo->free_blocks == 0 ||
1243                             shmem_acct_block(info->flags)) {
1244                                 spin_unlock(&sbinfo->stat_lock);
1245                                 spin_unlock(&info->lock);
1246                                 error = -ENOSPC;
1247                                 goto failed;
1248                         }
1249                         sbinfo->free_blocks--;
1250                         inode->i_blocks += BLOCKS_PER_PAGE;
1251                         spin_unlock(&sbinfo->stat_lock);
1252                 } else if (shmem_acct_block(info->flags)) {
1253                         spin_unlock(&info->lock);
1254                         error = -ENOSPC;
1255                         goto failed;
1256                 }
1257
1258                 if (!filepage) {
1259                         spin_unlock(&info->lock);
1260                         filepage = shmem_alloc_page(mapping_gfp_mask(mapping),
1261                                                     info,
1262                                                     idx);
1263                         if (!filepage) {
1264                                 shmem_unacct_blocks(info->flags, 1);
1265                                 shmem_free_blocks(inode, 1);
1266                                 error = -ENOMEM;
1267                                 goto failed;
1268                         }
1269
1270                         spin_lock(&info->lock);
1271                         entry = shmem_swp_alloc(info, idx, sgp);
1272                         if (IS_ERR(entry))
1273                                 error = PTR_ERR(entry);
1274                         else {
1275                                 swap = *entry;
1276                                 shmem_swp_unmap(entry);
1277                         }
1278                         if (error || swap.val || 0 != add_to_page_cache_lru(
1279                                         filepage, mapping, idx, GFP_ATOMIC)) {
1280                                 spin_unlock(&info->lock);
1281                                 page_cache_release(filepage);
1282                                 shmem_unacct_blocks(info->flags, 1);
1283                                 shmem_free_blocks(inode, 1);
1284                                 filepage = NULL;
1285                                 if (error)
1286                                         goto failed;
1287                                 goto repeat;
1288                         }
1289                         info->flags |= SHMEM_PAGEIN;
1290                 }
1291
1292                 info->alloced++;
1293                 spin_unlock(&info->lock);
1294                 flush_dcache_page(filepage);
1295                 SetPageUptodate(filepage);
1296         }
1297 done:
1298         if (*pagep != filepage) {
1299                 *pagep = filepage;
1300                 if (sgp != SGP_FAULT)
1301                         unlock_page(filepage);
1302
1303         }
1304         return 0;
1305
1306 failed:
1307         if (*pagep != filepage) {
1308                 unlock_page(filepage);
1309                 page_cache_release(filepage);
1310         }
1311         return error;
1312 }
1313
1314 static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1315 {
1316         struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1317         int error;
1318         int ret;
1319
1320         if (((loff_t)vmf->pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
1321                 return VM_FAULT_SIGBUS;
1322
1323         error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_FAULT, &ret);
1324         if (error)
1325                 return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1326
1327         mark_page_accessed(vmf->page);
1328         return ret | VM_FAULT_LOCKED;
1329 }
1330
1331 #ifdef CONFIG_NUMA
1332 int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *new)
1333 {
1334         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1335         return mpol_set_shared_policy(&SHMEM_I(i)->policy, vma, new);
1336 }
1337
1338 struct mempolicy *
1339 shmem_get_policy(struct vm_area_struct *vma, unsigned long addr)
1340 {
1341         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1342         unsigned long idx;
1343
1344         idx = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1345         return mpol_shared_policy_lookup(&SHMEM_I(i)->policy, idx);
1346 }
1347 #endif
1348
1349 int shmem_lock(struct file *file, int lock, struct user_struct *user)
1350 {
1351         struct inode *inode = file->f_path.dentry->d_inode;
1352         struct shmem_inode_info *info = SHMEM_I(inode);
1353         int retval = -ENOMEM;
1354
1355         spin_lock(&info->lock);
1356         if (lock && !(info->flags & VM_LOCKED)) {
1357                 if (!user_shm_lock(inode->i_size, user))
1358                         goto out_nomem;
1359                 info->flags |= VM_LOCKED;
1360         }
1361         if (!lock && (info->flags & VM_LOCKED) && user) {
1362                 user_shm_unlock(inode->i_size, user);
1363                 info->flags &= ~VM_LOCKED;
1364         }
1365         retval = 0;
1366 out_nomem:
1367         spin_unlock(&info->lock);
1368         return retval;
1369 }
1370
1371 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1372 {
1373         file_accessed(file);
1374         vma->vm_ops = &shmem_vm_ops;
1375         vma->vm_flags |= VM_CAN_NONLINEAR;
1376         return 0;
1377 }
1378
1379 static struct inode *
1380 shmem_get_inode(struct super_block *sb, int mode, dev_t dev)
1381 {
1382         struct inode *inode;
1383         struct shmem_inode_info *info;
1384         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1385
1386         if (sbinfo->max_inodes) {
1387                 spin_lock(&sbinfo->stat_lock);
1388                 if (!sbinfo->free_inodes) {
1389                         spin_unlock(&sbinfo->stat_lock);
1390                         return NULL;
1391                 }
1392                 sbinfo->free_inodes--;
1393                 spin_unlock(&sbinfo->stat_lock);
1394         }
1395
1396         inode = new_inode(sb);
1397         if (inode) {
1398                 inode->i_mode = mode;
1399                 inode->i_uid = current->fsuid;
1400                 inode->i_gid = current->fsgid;
1401                 inode->i_blocks = 0;
1402                 inode->i_mapping->a_ops = &shmem_aops;
1403                 inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1404                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1405                 inode->i_generation = get_seconds();
1406                 info = SHMEM_I(inode);
1407                 memset(info, 0, (char *)inode - (char *)info);
1408                 spin_lock_init(&info->lock);
1409                 INIT_LIST_HEAD(&info->swaplist);
1410
1411                 switch (mode & S_IFMT) {
1412                 default:
1413                         inode->i_op = &shmem_special_inode_operations;
1414                         init_special_inode(inode, mode, dev);
1415                         break;
1416                 case S_IFREG:
1417                         inode->i_op = &shmem_inode_operations;
1418                         inode->i_fop = &shmem_file_operations;
1419                         mpol_shared_policy_init(&info->policy, sbinfo->policy,
1420                                                         &sbinfo->policy_nodes);
1421                         break;
1422                 case S_IFDIR:
1423                         inc_nlink(inode);
1424                         /* Some things misbehave if size == 0 on a directory */
1425                         inode->i_size = 2 * BOGO_DIRENT_SIZE;
1426                         inode->i_op = &shmem_dir_inode_operations;
1427                         inode->i_fop = &simple_dir_operations;
1428                         break;
1429                 case S_IFLNK:
1430                         /*
1431                          * Must not load anything in the rbtree,
1432                          * mpol_free_shared_policy will not be called.
1433                          */
1434                         mpol_shared_policy_init(&info->policy, MPOL_DEFAULT,
1435                                                 NULL);
1436                         break;
1437                 }
1438         } else if (sbinfo->max_inodes) {
1439                 spin_lock(&sbinfo->stat_lock);
1440                 sbinfo->free_inodes++;
1441                 spin_unlock(&sbinfo->stat_lock);
1442         }
1443         return inode;
1444 }
1445
1446 #ifdef CONFIG_TMPFS
1447 static const struct inode_operations shmem_symlink_inode_operations;
1448 static const struct inode_operations shmem_symlink_inline_operations;
1449
1450 /*
1451  * Normally tmpfs avoids the use of shmem_readpage and shmem_write_begin;
1452  * but providing them allows a tmpfs file to be used for splice, sendfile, and
1453  * below the loop driver, in the generic fashion that many filesystems support.
1454  */
1455 static int shmem_readpage(struct file *file, struct page *page)
1456 {
1457         struct inode *inode = page->mapping->host;
1458         int error = shmem_getpage(inode, page->index, &page, SGP_CACHE, NULL);
1459         unlock_page(page);
1460         return error;
1461 }
1462
1463 static int
1464 shmem_write_begin(struct file *file, struct address_space *mapping,
1465                         loff_t pos, unsigned len, unsigned flags,
1466                         struct page **pagep, void **fsdata)
1467 {
1468         struct inode *inode = mapping->host;
1469         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1470         *pagep = NULL;
1471         return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
1472 }
1473
1474 static int
1475 shmem_write_end(struct file *file, struct address_space *mapping,
1476                         loff_t pos, unsigned len, unsigned copied,
1477                         struct page *page, void *fsdata)
1478 {
1479         struct inode *inode = mapping->host;
1480
1481         set_page_dirty(page);
1482         page_cache_release(page);
1483
1484         if (pos+copied > inode->i_size)
1485                 i_size_write(inode, pos+copied);
1486
1487         return copied;
1488 }
1489
1490 static ssize_t
1491 shmem_file_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
1492 {
1493         struct inode    *inode = file->f_path.dentry->d_inode;
1494         loff_t          pos;
1495         unsigned long   written;
1496         ssize_t         err;
1497
1498         if ((ssize_t) count < 0)
1499                 return -EINVAL;
1500
1501         if (!access_ok(VERIFY_READ, buf, count))
1502                 return -EFAULT;
1503
1504         mutex_lock(&inode->i_mutex);
1505
1506         pos = *ppos;
1507         written = 0;
1508
1509         err = generic_write_checks(file, &pos, &count, 0);
1510         if (err || !count)
1511                 goto out;
1512
1513         err = remove_suid(file->f_path.dentry);
1514         if (err)
1515                 goto out;
1516
1517         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
1518
1519         do {
1520                 struct page *page = NULL;
1521                 unsigned long bytes, index, offset;
1522                 char *kaddr;
1523                 int left;
1524
1525                 offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
1526                 index = pos >> PAGE_CACHE_SHIFT;
1527                 bytes = PAGE_CACHE_SIZE - offset;
1528                 if (bytes > count)
1529                         bytes = count;
1530
1531                 /*
1532                  * We don't hold page lock across copy from user -
1533                  * what would it guard against? - so no deadlock here.
1534                  * But it still may be a good idea to prefault below.
1535                  */
1536
1537                 err = shmem_getpage(inode, index, &page, SGP_WRITE, NULL);
1538                 if (err)
1539                         break;
1540
1541                 left = bytes;
1542                 if (PageHighMem(page)) {
1543                         volatile unsigned char dummy;
1544                         __get_user(dummy, buf);
1545                         __get_user(dummy, buf + bytes - 1);
1546
1547                         kaddr = kmap_atomic(page, KM_USER0);
1548                         left = __copy_from_user_inatomic(kaddr + offset,
1549                                                         buf, bytes);
1550                         kunmap_atomic(kaddr, KM_USER0);
1551                 }
1552                 if (left) {
1553                         kaddr = kmap(page);
1554                         left = __copy_from_user(kaddr + offset, buf, bytes);
1555                         kunmap(page);
1556                 }
1557
1558                 written += bytes;
1559                 count -= bytes;
1560                 pos += bytes;
1561                 buf += bytes;
1562                 if (pos > inode->i_size)
1563                         i_size_write(inode, pos);
1564
1565                 flush_dcache_page(page);
1566                 set_page_dirty(page);
1567                 mark_page_accessed(page);
1568                 page_cache_release(page);
1569
1570                 if (left) {
1571                         pos -= left;
1572                         written -= left;
1573                         err = -EFAULT;
1574                         break;
1575                 }
1576
1577                 /*
1578                  * Our dirty pages are not counted in nr_dirty,
1579                  * and we do not attempt to balance dirty pages.
1580                  */
1581
1582                 cond_resched();
1583         } while (count);
1584
1585         *ppos = pos;
1586         if (written)
1587                 err = written;
1588 out:
1589         mutex_unlock(&inode->i_mutex);
1590         return err;
1591 }
1592
1593 static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
1594 {
1595         struct inode *inode = filp->f_path.dentry->d_inode;
1596         struct address_space *mapping = inode->i_mapping;
1597         unsigned long index, offset;
1598
1599         index = *ppos >> PAGE_CACHE_SHIFT;
1600         offset = *ppos & ~PAGE_CACHE_MASK;
1601
1602         for (;;) {
1603                 struct page *page = NULL;
1604                 unsigned long end_index, nr, ret;
1605                 loff_t i_size = i_size_read(inode);
1606
1607                 end_index = i_size >> PAGE_CACHE_SHIFT;
1608                 if (index > end_index)
1609                         break;
1610                 if (index == end_index) {
1611                         nr = i_size & ~PAGE_CACHE_MASK;
1612                         if (nr <= offset)
1613                                 break;
1614                 }
1615
1616                 desc->error = shmem_getpage(inode, index, &page, SGP_READ, NULL);
1617                 if (desc->error) {
1618                         if (desc->error == -EINVAL)
1619                                 desc->error = 0;
1620                         break;
1621                 }
1622
1623                 /*
1624                  * We must evaluate after, since reads (unlike writes)
1625                  * are called without i_mutex protection against truncate
1626                  */
1627                 nr = PAGE_CACHE_SIZE;
1628                 i_size = i_size_read(inode);
1629                 end_index = i_size >> PAGE_CACHE_SHIFT;
1630                 if (index == end_index) {
1631                         nr = i_size & ~PAGE_CACHE_MASK;
1632                         if (nr <= offset) {
1633                                 if (page)
1634                                         page_cache_release(page);
1635                                 break;
1636                         }
1637                 }
1638                 nr -= offset;
1639
1640                 if (page) {
1641                         /*
1642                          * If users can be writing to this page using arbitrary
1643                          * virtual addresses, take care about potential aliasing
1644                          * before reading the page on the kernel side.
1645                          */
1646                         if (mapping_writably_mapped(mapping))
1647                                 flush_dcache_page(page);
1648                         /*
1649                          * Mark the page accessed if we read the beginning.
1650                          */
1651                         if (!offset)
1652                                 mark_page_accessed(page);
1653                 } else {
1654                         page = ZERO_PAGE(0);
1655                         page_cache_get(page);
1656                 }
1657
1658                 /*
1659                  * Ok, we have the page, and it's up-to-date, so
1660                  * now we can copy it to user space...
1661                  *
1662                  * The actor routine returns how many bytes were actually used..
1663                  * NOTE! This may not be the same as how much of a user buffer
1664                  * we filled up (we may be padding etc), so we can only update
1665                  * "pos" here (the actor routine has to update the user buffer
1666                  * pointers and the remaining count).
1667                  */
1668                 ret = actor(desc, page, offset, nr);
1669                 offset += ret;
1670                 index += offset >> PAGE_CACHE_SHIFT;
1671                 offset &= ~PAGE_CACHE_MASK;
1672
1673                 page_cache_release(page);
1674                 if (ret != nr || !desc->count)
1675                         break;
1676
1677                 cond_resched();
1678         }
1679
1680         *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1681         file_accessed(filp);
1682 }
1683
1684 static ssize_t shmem_file_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
1685 {
1686         read_descriptor_t desc;
1687
1688         if ((ssize_t) count < 0)
1689                 return -EINVAL;
1690         if (!access_ok(VERIFY_WRITE, buf, count))
1691                 return -EFAULT;
1692         if (!count)
1693                 return 0;
1694
1695         desc.written = 0;
1696         desc.count = count;
1697         desc.arg.buf = buf;
1698         desc.error = 0;
1699
1700         do_shmem_file_read(filp, ppos, &desc, file_read_actor);
1701         if (desc.written)
1702                 return desc.written;
1703         return desc.error;
1704 }
1705
1706 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
1707 {
1708         struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
1709
1710         buf->f_type = TMPFS_MAGIC;
1711         buf->f_bsize = PAGE_CACHE_SIZE;
1712         buf->f_namelen = NAME_MAX;
1713         spin_lock(&sbinfo->stat_lock);
1714         if (sbinfo->max_blocks) {
1715                 buf->f_blocks = sbinfo->max_blocks;
1716                 buf->f_bavail = buf->f_bfree = sbinfo->free_blocks;
1717         }
1718         if (sbinfo->max_inodes) {
1719                 buf->f_files = sbinfo->max_inodes;
1720                 buf->f_ffree = sbinfo->free_inodes;
1721         }
1722         /* else leave those fields 0 like simple_statfs */
1723         spin_unlock(&sbinfo->stat_lock);
1724         return 0;
1725 }
1726
1727 /*
1728  * File creation. Allocate an inode, and we're done..
1729  */
1730 static int
1731 shmem_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
1732 {
1733         struct inode *inode = shmem_get_inode(dir->i_sb, mode, dev);
1734         int error = -ENOSPC;
1735
1736         if (inode) {
1737                 error = security_inode_init_security(inode, dir, NULL, NULL,
1738                                                      NULL);
1739                 if (error) {
1740                         if (error != -EOPNOTSUPP) {
1741                                 iput(inode);
1742                                 return error;
1743                         }
1744                 }
1745                 error = shmem_acl_init(inode, dir);
1746                 if (error) {
1747                         iput(inode);
1748                         return error;
1749                 }
1750                 if (dir->i_mode & S_ISGID) {
1751                         inode->i_gid = dir->i_gid;
1752                         if (S_ISDIR(mode))
1753                                 inode->i_mode |= S_ISGID;
1754                 }
1755                 dir->i_size += BOGO_DIRENT_SIZE;
1756                 dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1757                 d_instantiate(dentry, inode);
1758                 dget(dentry); /* Extra count - pin the dentry in core */
1759         }
1760         return error;
1761 }
1762
1763 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, int mode)
1764 {
1765         int error;
1766
1767         if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
1768                 return error;
1769         inc_nlink(dir);
1770         return 0;
1771 }
1772
1773 static int shmem_create(struct inode *dir, struct dentry *dentry, int mode,
1774                 struct nameidata *nd)
1775 {
1776         return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
1777 }
1778
1779 /*
1780  * Link a file..
1781  */
1782 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
1783 {
1784         struct inode *inode = old_dentry->d_inode;
1785         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1786
1787         /*
1788          * No ordinary (disk based) filesystem counts links as inodes;
1789          * but each new link needs a new dentry, pinning lowmem, and
1790          * tmpfs dentries cannot be pruned until they are unlinked.
1791          */
1792         if (sbinfo->max_inodes) {
1793                 spin_lock(&sbinfo->stat_lock);
1794                 if (!sbinfo->free_inodes) {
1795                         spin_unlock(&sbinfo->stat_lock);
1796                         return -ENOSPC;
1797                 }
1798                 sbinfo->free_inodes--;
1799                 spin_unlock(&sbinfo->stat_lock);
1800         }
1801
1802         dir->i_size += BOGO_DIRENT_SIZE;
1803         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1804         inc_nlink(inode);
1805         atomic_inc(&inode->i_count);    /* New dentry reference */
1806         dget(dentry);           /* Extra pinning count for the created dentry */
1807         d_instantiate(dentry, inode);
1808         return 0;
1809 }
1810
1811 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
1812 {
1813         struct inode *inode = dentry->d_inode;
1814
1815         if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode)) {
1816                 struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1817                 if (sbinfo->max_inodes) {
1818                         spin_lock(&sbinfo->stat_lock);
1819                         sbinfo->free_inodes++;
1820                         spin_unlock(&sbinfo->stat_lock);
1821                 }
1822         }
1823
1824         dir->i_size -= BOGO_DIRENT_SIZE;
1825         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1826         drop_nlink(inode);
1827         dput(dentry);   /* Undo the count from "create" - this does all the work */
1828         return 0;
1829 }
1830
1831 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
1832 {
1833         if (!simple_empty(dentry))
1834                 return -ENOTEMPTY;
1835
1836         drop_nlink(dentry->d_inode);
1837         drop_nlink(dir);
1838         return shmem_unlink(dir, dentry);
1839 }
1840
1841 /*
1842  * The VFS layer already does all the dentry stuff for rename,
1843  * we just have to decrement the usage count for the target if
1844  * it exists so that the VFS layer correctly free's it when it
1845  * gets overwritten.
1846  */
1847 static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
1848 {
1849         struct inode *inode = old_dentry->d_inode;
1850         int they_are_dirs = S_ISDIR(inode->i_mode);
1851
1852         if (!simple_empty(new_dentry))
1853                 return -ENOTEMPTY;
1854
1855         if (new_dentry->d_inode) {
1856                 (void) shmem_unlink(new_dir, new_dentry);
1857                 if (they_are_dirs)
1858                         drop_nlink(old_dir);
1859         } else if (they_are_dirs) {
1860                 drop_nlink(old_dir);
1861                 inc_nlink(new_dir);
1862         }
1863
1864         old_dir->i_size -= BOGO_DIRENT_SIZE;
1865         new_dir->i_size += BOGO_DIRENT_SIZE;
1866         old_dir->i_ctime = old_dir->i_mtime =
1867         new_dir->i_ctime = new_dir->i_mtime =
1868         inode->i_ctime = CURRENT_TIME;
1869         return 0;
1870 }
1871
1872 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
1873 {
1874         int error;
1875         int len;
1876         struct inode *inode;
1877         struct page *page = NULL;
1878         char *kaddr;
1879         struct shmem_inode_info *info;
1880
1881         len = strlen(symname) + 1;
1882         if (len > PAGE_CACHE_SIZE)
1883                 return -ENAMETOOLONG;
1884
1885         inode = shmem_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0);
1886         if (!inode)
1887                 return -ENOSPC;
1888
1889         error = security_inode_init_security(inode, dir, NULL, NULL,
1890                                              NULL);
1891         if (error) {
1892                 if (error != -EOPNOTSUPP) {
1893                         iput(inode);
1894                         return error;
1895                 }
1896                 error = 0;
1897         }
1898
1899         info = SHMEM_I(inode);
1900         inode->i_size = len-1;
1901         if (len <= (char *)inode - (char *)info) {
1902                 /* do it inline */
1903                 memcpy(info, symname, len);
1904                 inode->i_op = &shmem_symlink_inline_operations;
1905         } else {
1906                 error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
1907                 if (error) {
1908                         iput(inode);
1909                         return error;
1910                 }
1911                 inode->i_op = &shmem_symlink_inode_operations;
1912                 kaddr = kmap_atomic(page, KM_USER0);
1913                 memcpy(kaddr, symname, len);
1914                 kunmap_atomic(kaddr, KM_USER0);
1915                 set_page_dirty(page);
1916                 page_cache_release(page);
1917         }
1918         if (dir->i_mode & S_ISGID)
1919                 inode->i_gid = dir->i_gid;
1920         dir->i_size += BOGO_DIRENT_SIZE;
1921         dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1922         d_instantiate(dentry, inode);
1923         dget(dentry);
1924         return 0;
1925 }
1926
1927 static void *shmem_follow_link_inline(struct dentry *dentry, struct nameidata *nd)
1928 {
1929         nd_set_link(nd, (char *)SHMEM_I(dentry->d_inode));
1930         return NULL;
1931 }
1932
1933 static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
1934 {
1935         struct page *page = NULL;
1936         int res = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
1937         nd_set_link(nd, res ? ERR_PTR(res) : kmap(page));
1938         return page;
1939 }
1940
1941 static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
1942 {
1943         if (!IS_ERR(nd_get_link(nd))) {
1944                 struct page *page = cookie;
1945                 kunmap(page);
1946                 mark_page_accessed(page);
1947                 page_cache_release(page);
1948         }
1949 }
1950
1951 static const struct inode_operations shmem_symlink_inline_operations = {
1952         .readlink       = generic_readlink,
1953         .follow_link    = shmem_follow_link_inline,
1954 };
1955
1956 static const struct inode_operations shmem_symlink_inode_operations = {
1957         .truncate       = shmem_truncate,
1958         .readlink       = generic_readlink,
1959         .follow_link    = shmem_follow_link,
1960         .put_link       = shmem_put_link,
1961 };
1962
1963 #ifdef CONFIG_TMPFS_POSIX_ACL
1964 /**
1965  * Superblocks without xattr inode operations will get security.* xattr
1966  * support from the VFS "for free". As soon as we have any other xattrs
1967  * like ACLs, we also need to implement the security.* handlers at
1968  * filesystem level, though.
1969  */
1970
1971 static size_t shmem_xattr_security_list(struct inode *inode, char *list,
1972                                         size_t list_len, const char *name,
1973                                         size_t name_len)
1974 {
1975         return security_inode_listsecurity(inode, list, list_len);
1976 }
1977
1978 static int shmem_xattr_security_get(struct inode *inode, const char *name,
1979                                     void *buffer, size_t size)
1980 {
1981         if (strcmp(name, "") == 0)
1982                 return -EINVAL;
1983         return security_inode_getsecurity(inode, name, buffer, size,
1984                                           -EOPNOTSUPP);
1985 }
1986
1987 static int shmem_xattr_security_set(struct inode *inode, const char *name,
1988                                     const void *value, size_t size, int flags)
1989 {
1990         if (strcmp(name, "") == 0)
1991                 return -EINVAL;
1992         return security_inode_setsecurity(inode, name, value, size, flags);
1993 }
1994
1995 static struct xattr_handler shmem_xattr_security_handler = {
1996         .prefix = XATTR_SECURITY_PREFIX,
1997         .list   = shmem_xattr_security_list,
1998         .get    = shmem_xattr_security_get,
1999         .set    = shmem_xattr_security_set,
2000 };
2001
2002 static struct xattr_handler *shmem_xattr_handlers[] = {
2003         &shmem_xattr_acl_access_handler,
2004         &shmem_xattr_acl_default_handler,
2005         &shmem_xattr_security_handler,
2006         NULL
2007 };
2008 #endif
2009
2010 static struct dentry *shmem_get_parent(struct dentry *child)
2011 {
2012         return ERR_PTR(-ESTALE);
2013 }
2014
2015 static int shmem_match(struct inode *ino, void *vfh)
2016 {
2017         __u32 *fh = vfh;
2018         __u64 inum = fh[2];
2019         inum = (inum << 32) | fh[1];
2020         return ino->i_ino == inum && fh[0] == ino->i_generation;
2021 }
2022
2023 static struct dentry *shmem_get_dentry(struct super_block *sb, void *vfh)
2024 {
2025         struct dentry *de = NULL;
2026         struct inode *inode;
2027         __u32 *fh = vfh;
2028         __u64 inum = fh[2];
2029         inum = (inum << 32) | fh[1];
2030
2031         inode = ilookup5(sb, (unsigned long)(inum+fh[0]), shmem_match, vfh);
2032         if (inode) {
2033                 de = d_find_alias(inode);
2034                 iput(inode);
2035         }
2036
2037         return de? de: ERR_PTR(-ESTALE);
2038 }
2039
2040 static struct dentry *shmem_decode_fh(struct super_block *sb, __u32 *fh,
2041                 int len, int type,
2042                 int (*acceptable)(void *context, struct dentry *de),
2043                 void *context)
2044 {
2045         if (len < 3)
2046                 return ERR_PTR(-ESTALE);
2047
2048         return sb->s_export_op->find_exported_dentry(sb, fh, NULL, acceptable,
2049                                                         context);
2050 }
2051
2052 static int shmem_encode_fh(struct dentry *dentry, __u32 *fh, int *len,
2053                                 int connectable)
2054 {
2055         struct inode *inode = dentry->d_inode;
2056
2057         if (*len < 3)
2058                 return 255;
2059
2060         if (hlist_unhashed(&inode->i_hash)) {
2061                 /* Unfortunately insert_inode_hash is not idempotent,
2062                  * so as we hash inodes here rather than at creation
2063                  * time, we need a lock to ensure we only try
2064                  * to do it once
2065                  */
2066                 static DEFINE_SPINLOCK(lock);
2067                 spin_lock(&lock);
2068                 if (hlist_unhashed(&inode->i_hash))
2069                         __insert_inode_hash(inode,
2070                                             inode->i_ino + inode->i_generation);
2071                 spin_unlock(&lock);
2072         }
2073
2074         fh[0] = inode->i_generation;
2075         fh[1] = inode->i_ino;
2076         fh[2] = ((__u64)inode->i_ino) >> 32;
2077
2078         *len = 3;
2079         return 1;
2080 }
2081
2082 static struct export_operations shmem_export_ops = {
2083         .get_parent     = shmem_get_parent,
2084         .get_dentry     = shmem_get_dentry,
2085         .encode_fh      = shmem_encode_fh,
2086         .decode_fh      = shmem_decode_fh,
2087 };
2088
2089 static int shmem_parse_options(char *options, int *mode, uid_t *uid,
2090         gid_t *gid, unsigned long *blocks, unsigned long *inodes,
2091         int *policy, nodemask_t *policy_nodes)
2092 {
2093         char *this_char, *value, *rest;
2094
2095         while (options != NULL) {
2096                 this_char = options;
2097                 for (;;) {
2098                         /*
2099                          * NUL-terminate this option: unfortunately,
2100                          * mount options form a comma-separated list,
2101                          * but mpol's nodelist may also contain commas.
2102                          */
2103                         options = strchr(options, ',');
2104                         if (options == NULL)
2105                                 break;
2106                         options++;
2107                         if (!isdigit(*options)) {
2108                                 options[-1] = '\0';
2109                                 break;
2110                         }
2111                 }
2112                 if (!*this_char)
2113                         continue;
2114                 if ((value = strchr(this_char,'=')) != NULL) {
2115                         *value++ = 0;
2116                 } else {
2117                         printk(KERN_ERR
2118                             "tmpfs: No value for mount option '%s'\n",
2119                             this_char);
2120                         return 1;
2121                 }
2122
2123                 if (!strcmp(this_char,"size")) {
2124                         unsigned long long size;
2125                         size = memparse(value,&rest);
2126                         if (*rest == '%') {
2127                                 size <<= PAGE_SHIFT;
2128                                 size *= totalram_pages;
2129                                 do_div(size, 100);
2130                                 rest++;
2131                         }
2132                         if (*rest)
2133                                 goto bad_val;
2134                         *blocks = size >> PAGE_CACHE_SHIFT;
2135                 } else if (!strcmp(this_char,"nr_blocks")) {
2136                         *blocks = memparse(value,&rest);
2137                         if (*rest)
2138                                 goto bad_val;
2139                 } else if (!strcmp(this_char,"nr_inodes")) {
2140                         *inodes = memparse(value,&rest);
2141                         if (*rest)
2142                                 goto bad_val;
2143                 } else if (!strcmp(this_char,"mode")) {
2144                         if (!mode)
2145                                 continue;
2146                         *mode = simple_strtoul(value,&rest,8);
2147                         if (*rest)
2148                                 goto bad_val;
2149                 } else if (!strcmp(this_char,"uid")) {
2150                         if (!uid)
2151                                 continue;
2152                         *uid = simple_strtoul(value,&rest,0);
2153                         if (*rest)
2154                                 goto bad_val;
2155                 } else if (!strcmp(this_char,"gid")) {
2156                         if (!gid)
2157                                 continue;
2158                         *gid = simple_strtoul(value,&rest,0);
2159                         if (*rest)
2160                                 goto bad_val;
2161                 } else if (!strcmp(this_char,"mpol")) {
2162                         if (shmem_parse_mpol(value,policy,policy_nodes))
2163                                 goto bad_val;
2164                 } else {
2165                         printk(KERN_ERR "tmpfs: Bad mount option %s\n",
2166                                this_char);
2167                         return 1;
2168                 }
2169         }
2170         return 0;
2171
2172 bad_val:
2173         printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
2174                value, this_char);
2175         return 1;
2176
2177 }
2178
2179 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2180 {
2181         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2182         unsigned long max_blocks = sbinfo->max_blocks;
2183         unsigned long max_inodes = sbinfo->max_inodes;
2184         int policy = sbinfo->policy;
2185         nodemask_t policy_nodes = sbinfo->policy_nodes;
2186         unsigned long blocks;
2187         unsigned long inodes;
2188         int error = -EINVAL;
2189
2190         if (shmem_parse_options(data, NULL, NULL, NULL, &max_blocks,
2191                                 &max_inodes, &policy, &policy_nodes))
2192                 return error;
2193
2194         spin_lock(&sbinfo->stat_lock);
2195         blocks = sbinfo->max_blocks - sbinfo->free_blocks;
2196         inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2197         if (max_blocks < blocks)
2198                 goto out;
2199         if (max_inodes < inodes)
2200                 goto out;
2201         /*
2202          * Those tests also disallow limited->unlimited while any are in
2203          * use, so i_blocks will always be zero when max_blocks is zero;
2204          * but we must separately disallow unlimited->limited, because
2205          * in that case we have no record of how much is already in use.
2206          */
2207         if (max_blocks && !sbinfo->max_blocks)
2208                 goto out;
2209         if (max_inodes && !sbinfo->max_inodes)
2210                 goto out;
2211
2212         error = 0;
2213         sbinfo->max_blocks  = max_blocks;
2214         sbinfo->free_blocks = max_blocks - blocks;
2215         sbinfo->max_inodes  = max_inodes;
2216         sbinfo->free_inodes = max_inodes - inodes;
2217         sbinfo->policy = policy;
2218         sbinfo->policy_nodes = policy_nodes;
2219 out:
2220         spin_unlock(&sbinfo->stat_lock);
2221         return error;
2222 }
2223 #endif
2224
2225 static void shmem_put_super(struct super_block *sb)
2226 {
2227         kfree(sb->s_fs_info);
2228         sb->s_fs_info = NULL;
2229 }
2230
2231 static int shmem_fill_super(struct super_block *sb,
2232                             void *data, int silent)
2233 {
2234         struct inode *inode;
2235         struct dentry *root;
2236         int mode   = S_IRWXUGO | S_ISVTX;
2237         uid_t uid = current->fsuid;
2238         gid_t gid = current->fsgid;
2239         int err = -ENOMEM;
2240         struct shmem_sb_info *sbinfo;
2241         unsigned long blocks = 0;
2242         unsigned long inodes = 0;
2243         int policy = MPOL_DEFAULT;
2244         nodemask_t policy_nodes = node_states[N_HIGH_MEMORY];
2245
2246 #ifdef CONFIG_TMPFS
2247         /*
2248          * Per default we only allow half of the physical ram per
2249          * tmpfs instance, limiting inodes to one per page of lowmem;
2250          * but the internal instance is left unlimited.
2251          */
2252         if (!(sb->s_flags & MS_NOUSER)) {
2253                 blocks = totalram_pages / 2;
2254                 inodes = totalram_pages - totalhigh_pages;
2255                 if (inodes > blocks)
2256                         inodes = blocks;
2257                 if (shmem_parse_options(data, &mode, &uid, &gid, &blocks,
2258                                         &inodes, &policy, &policy_nodes))
2259                         return -EINVAL;
2260         }
2261         sb->s_export_op = &shmem_export_ops;
2262 #else
2263         sb->s_flags |= MS_NOUSER;
2264 #endif
2265
2266         /* Round up to L1_CACHE_BYTES to resist false sharing */
2267         sbinfo = kmalloc(max((int)sizeof(struct shmem_sb_info),
2268                                 L1_CACHE_BYTES), GFP_KERNEL);
2269         if (!sbinfo)
2270                 return -ENOMEM;
2271
2272         spin_lock_init(&sbinfo->stat_lock);
2273         sbinfo->max_blocks = blocks;
2274         sbinfo->free_blocks = blocks;
2275         sbinfo->max_inodes = inodes;
2276         sbinfo->free_inodes = inodes;
2277         sbinfo->policy = policy;
2278         sbinfo->policy_nodes = policy_nodes;
2279
2280         sb->s_fs_info = sbinfo;
2281         sb->s_maxbytes = SHMEM_MAX_BYTES;
2282         sb->s_blocksize = PAGE_CACHE_SIZE;
2283         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
2284         sb->s_magic = TMPFS_MAGIC;
2285         sb->s_op = &shmem_ops;
2286         sb->s_time_gran = 1;
2287 #ifdef CONFIG_TMPFS_POSIX_ACL
2288         sb->s_xattr = shmem_xattr_handlers;
2289         sb->s_flags |= MS_POSIXACL;
2290 #endif
2291
2292         inode = shmem_get_inode(sb, S_IFDIR | mode, 0);
2293         if (!inode)
2294                 goto failed;
2295         inode->i_uid = uid;
2296         inode->i_gid = gid;
2297         root = d_alloc_root(inode);
2298         if (!root)
2299                 goto failed_iput;
2300         sb->s_root = root;
2301         return 0;
2302
2303 failed_iput:
2304         iput(inode);
2305 failed:
2306         shmem_put_super(sb);
2307         return err;
2308 }
2309
2310 static struct kmem_cache *shmem_inode_cachep;
2311
2312 static struct inode *shmem_alloc_inode(struct super_block *sb)
2313 {
2314         struct shmem_inode_info *p;
2315         p = (struct shmem_inode_info *)kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
2316         if (!p)
2317                 return NULL;
2318         return &p->vfs_inode;
2319 }
2320
2321 static void shmem_destroy_inode(struct inode *inode)
2322 {
2323         if ((inode->i_mode & S_IFMT) == S_IFREG) {
2324                 /* only struct inode is valid if it's an inline symlink */
2325                 mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2326         }
2327         shmem_acl_destroy_inode(inode);
2328         kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2329 }
2330
2331 static void init_once(void *foo, struct kmem_cache *cachep,
2332                       unsigned long flags)
2333 {
2334         struct shmem_inode_info *p = (struct shmem_inode_info *) foo;
2335
2336         inode_init_once(&p->vfs_inode);
2337 #ifdef CONFIG_TMPFS_POSIX_ACL
2338         p->i_acl = NULL;
2339         p->i_default_acl = NULL;
2340 #endif
2341 }
2342
2343 static int init_inodecache(void)
2344 {
2345         shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
2346                                 sizeof(struct shmem_inode_info),
2347                                 0, 0, init_once);
2348         if (shmem_inode_cachep == NULL)
2349                 return -ENOMEM;
2350         return 0;
2351 }
2352
2353 static void destroy_inodecache(void)
2354 {
2355         kmem_cache_destroy(shmem_inode_cachep);
2356 }
2357
2358 static const struct address_space_operations shmem_aops = {
2359         .writepage      = shmem_writepage,
2360         .set_page_dirty = __set_page_dirty_no_writeback,
2361 #ifdef CONFIG_TMPFS
2362         .readpage       = shmem_readpage,
2363         .write_begin    = shmem_write_begin,
2364         .write_end      = shmem_write_end,
2365 #endif
2366         .migratepage    = migrate_page,
2367 };
2368
2369 static const struct file_operations shmem_file_operations = {
2370         .mmap           = shmem_mmap,
2371 #ifdef CONFIG_TMPFS
2372         .llseek         = generic_file_llseek,
2373         .read           = shmem_file_read,
2374         .write          = shmem_file_write,
2375         .fsync          = simple_sync_file,
2376         .splice_read    = generic_file_splice_read,
2377         .splice_write   = generic_file_splice_write,
2378 #endif
2379 };
2380
2381 static const struct inode_operations shmem_inode_operations = {
2382         .truncate       = shmem_truncate,
2383         .setattr        = shmem_notify_change,
2384         .truncate_range = shmem_truncate_range,
2385 #ifdef CONFIG_TMPFS_POSIX_ACL
2386         .setxattr       = generic_setxattr,
2387         .getxattr       = generic_getxattr,
2388         .listxattr      = generic_listxattr,
2389         .removexattr    = generic_removexattr,
2390         .permission     = shmem_permission,
2391 #endif
2392
2393 };
2394
2395 static const struct inode_operations shmem_dir_inode_operations = {
2396 #ifdef CONFIG_TMPFS
2397         .create         = shmem_create,
2398         .lookup         = simple_lookup,
2399         .link           = shmem_link,
2400         .unlink         = shmem_unlink,
2401         .symlink        = shmem_symlink,
2402         .mkdir          = shmem_mkdir,
2403         .rmdir          = shmem_rmdir,
2404         .mknod          = shmem_mknod,
2405         .rename         = shmem_rename,
2406 #endif
2407 #ifdef CONFIG_TMPFS_POSIX_ACL
2408         .setattr        = shmem_notify_change,
2409         .setxattr       = generic_setxattr,
2410         .getxattr       = generic_getxattr,
2411         .listxattr      = generic_listxattr,
2412         .removexattr    = generic_removexattr,
2413         .permission     = shmem_permission,
2414 #endif
2415 };
2416
2417 static const struct inode_operations shmem_special_inode_operations = {
2418 #ifdef CONFIG_TMPFS_POSIX_ACL
2419         .setattr        = shmem_notify_change,
2420         .setxattr       = generic_setxattr,
2421         .getxattr       = generic_getxattr,
2422         .listxattr      = generic_listxattr,
2423         .removexattr    = generic_removexattr,
2424         .permission     = shmem_permission,
2425 #endif
2426 };
2427
2428 static const struct super_operations shmem_ops = {
2429         .alloc_inode    = shmem_alloc_inode,
2430         .destroy_inode  = shmem_destroy_inode,
2431 #ifdef CONFIG_TMPFS
2432         .statfs         = shmem_statfs,
2433         .remount_fs     = shmem_remount_fs,
2434 #endif
2435         .delete_inode   = shmem_delete_inode,
2436         .drop_inode     = generic_delete_inode,
2437         .put_super      = shmem_put_super,
2438 };
2439
2440 static struct vm_operations_struct shmem_vm_ops = {
2441         .fault          = shmem_fault,
2442 #ifdef CONFIG_NUMA
2443         .set_policy     = shmem_set_policy,
2444         .get_policy     = shmem_get_policy,
2445 #endif
2446 };
2447
2448
2449 static int shmem_get_sb(struct file_system_type *fs_type,
2450         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
2451 {
2452         return get_sb_nodev(fs_type, flags, data, shmem_fill_super, mnt);
2453 }
2454
2455 static struct file_system_type tmpfs_fs_type = {
2456         .owner          = THIS_MODULE,
2457         .name           = "tmpfs",
2458         .get_sb         = shmem_get_sb,
2459         .kill_sb        = kill_litter_super,
2460 };
2461 static struct vfsmount *shm_mnt;
2462
2463 static int __init init_tmpfs(void)
2464 {
2465         int error;
2466
2467         error = init_inodecache();
2468         if (error)
2469                 goto out3;
2470
2471         error = register_filesystem(&tmpfs_fs_type);
2472         if (error) {
2473                 printk(KERN_ERR "Could not register tmpfs\n");
2474                 goto out2;
2475         }
2476
2477         shm_mnt = vfs_kern_mount(&tmpfs_fs_type, MS_NOUSER,
2478                                 tmpfs_fs_type.name, NULL);
2479         if (IS_ERR(shm_mnt)) {
2480                 error = PTR_ERR(shm_mnt);
2481                 printk(KERN_ERR "Could not kern_mount tmpfs\n");
2482                 goto out1;
2483         }
2484         return 0;
2485
2486 out1:
2487         unregister_filesystem(&tmpfs_fs_type);
2488 out2:
2489         destroy_inodecache();
2490 out3:
2491         shm_mnt = ERR_PTR(error);
2492         return error;
2493 }
2494 module_init(init_tmpfs)
2495
2496 /*
2497  * shmem_file_setup - get an unlinked file living in tmpfs
2498  *
2499  * @name: name for dentry (to be seen in /proc/<pid>/maps
2500  * @size: size to be set for the file
2501  *
2502  */
2503 struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags)
2504 {
2505         int error;
2506         struct file *file;
2507         struct inode *inode;
2508         struct dentry *dentry, *root;
2509         struct qstr this;
2510
2511         if (IS_ERR(shm_mnt))
2512                 return (void *)shm_mnt;
2513
2514         if (size < 0 || size > SHMEM_MAX_BYTES)
2515                 return ERR_PTR(-EINVAL);
2516
2517         if (shmem_acct_size(flags, size))
2518                 return ERR_PTR(-ENOMEM);
2519
2520         error = -ENOMEM;
2521         this.name = name;
2522         this.len = strlen(name);
2523         this.hash = 0; /* will go */
2524         root = shm_mnt->mnt_root;
2525         dentry = d_alloc(root, &this);
2526         if (!dentry)
2527                 goto put_memory;
2528
2529         error = -ENFILE;
2530         file = get_empty_filp();
2531         if (!file)
2532                 goto put_dentry;
2533
2534         error = -ENOSPC;
2535         inode = shmem_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0);
2536         if (!inode)
2537                 goto close_file;
2538
2539         SHMEM_I(inode)->flags = flags & VM_ACCOUNT;
2540         d_instantiate(dentry, inode);
2541         inode->i_size = size;
2542         inode->i_nlink = 0;     /* It is unlinked */
2543         file->f_path.mnt = mntget(shm_mnt);
2544         file->f_path.dentry = dentry;
2545         file->f_mapping = inode->i_mapping;
2546         file->f_op = &shmem_file_operations;
2547         file->f_mode = FMODE_WRITE | FMODE_READ;
2548         return file;
2549
2550 close_file:
2551         put_filp(file);
2552 put_dentry:
2553         dput(dentry);
2554 put_memory:
2555         shmem_unacct_size(flags, size);
2556         return ERR_PTR(error);
2557 }
2558
2559 /*
2560  * shmem_zero_setup - setup a shared anonymous mapping
2561  *
2562  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
2563  */
2564 int shmem_zero_setup(struct vm_area_struct *vma)
2565 {
2566         struct file *file;
2567         loff_t size = vma->vm_end - vma->vm_start;
2568
2569         file = shmem_file_setup("dev/zero", size, vma->vm_flags);
2570         if (IS_ERR(file))
2571                 return PTR_ERR(file);
2572
2573         if (vma->vm_file)
2574                 fput(vma->vm_file);
2575         vma->vm_file = file;
2576         vma->vm_ops = &shmem_vm_ops;
2577         return 0;
2578 }