mm/shmem.c

   1 /*
   2  * Resizable virtual memory filesystem for Linux.
   3  *
   4  * Copyright (C) 2000 Linus Torvalds.
   5  *               2000 Transmeta Corp.
   6  *               2000-2001 Christoph Rohland
   7  *               2000-2001 SAP AG
   8  *               2002 Red Hat Inc.
   9  * Copyright (C) 2002-2005 Hugh Dickins.
  10  * Copyright (C) 2002-2005 VERITAS Software Corporation.
  11  * Copyright (C) 2004 Andi Kleen, SuSE Labs
  12  *
  13  * Extended attribute support for tmpfs:
  14  * Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@lkcl.net>
  15  * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
  16  *
  17  * This file is released under the GPL.
  18  */
  19
  20 /*
  21  * This virtual memory filesystem is heavily based on the ramfs. It
  22  * extends ramfs by the ability to use swap and honor resource limits
  23  * which makes it a completely usable filesystem.
  24  */
  25
  26 #include <linux/module.h>
  27 #include <linux/init.h>
  28 #include <linux/fs.h>
  29 #include <linux/xattr.h>
  30 #include <linux/exportfs.h>
  31 #include <linux/generic_acl.h>
  32 #include <linux/mm.h>
  33 #include <linux/mman.h>
  34 #include <linux/file.h>
  35 #include <linux/swap.h>
  36 #include <linux/pagemap.h>
  37 #include <linux/string.h>
  38 #include <linux/slab.h>
  39 #include <linux/backing-dev.h>
  40 #include <linux/shmem_fs.h>
  41 #include <linux/mount.h>
  42 #include <linux/writeback.h>
  43 #include <linux/vfs.h>
  44 #include <linux/blkdev.h>
  45 #include <linux/security.h>
  46 #include <linux/swapops.h>
  47 #include <linux/mempolicy.h>
  48 #include <linux/namei.h>
  49 #include <linux/ctype.h>
  50 #include <linux/migrate.h>
  51 #include <linux/highmem.h>
  52 #include <linux/seq_file.h>
  53
  54 #include <asm/uaccess.h>
  55 #include <asm/div64.h>
  56 #include <asm/pgtable.h>
  57
  58 /* This magic number is used in glibc for posix shared memory */
  59 #define TMPFS_MAGIC     0x01021994
  60
  61 #define ENTRIES_PER_PAGE (PAGE_CACHE_SIZE/sizeof(unsigned long))
  62 #define ENTRIES_PER_PAGEPAGE (ENTRIES_PER_PAGE*ENTRIES_PER_PAGE)
  63 #define BLOCKS_PER_PAGE  (PAGE_CACHE_SIZE/512)
  64
  65 #define SHMEM_MAX_INDEX  (SHMEM_NR_DIRECT + (ENTRIES_PER_PAGEPAGE/2) * (ENTRIES_PER_PAGE+1))
  66 #define SHMEM_MAX_BYTES  ((unsigned long long)SHMEM_MAX_INDEX << PAGE_CACHE_SHIFT)
  67
  68 #define VM_ACCT(size)    (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
  69
  70 /* info->flags needs VM_flags to handle pagein/truncate races efficiently */
  71 #define SHMEM_PAGEIN     VM_READ
  72 #define SHMEM_TRUNCATE   VM_WRITE
  73
  74 /* Definition to limit shmem_truncate's steps between cond_rescheds */
  75 #define LATENCY_LIMIT    64
  76
  77 /* Pretend that each entry is of this size in directory's i_size */
  78 #define BOGO_DIRENT_SIZE 20
  79
  80 /* Flag allocation requirements to shmem_getpage and shmem_swp_alloc */
  81 enum sgp_type {
  82         SGP_READ,       /* don't exceed i_size, don't allocate page */
  83         SGP_CACHE,      /* don't exceed i_size, may allocate page */
  84         SGP_DIRTY,      /* like SGP_CACHE, but set new page dirty */
  85         SGP_WRITE,      /* may exceed i_size, may allocate page */
  86 };
  87
  88 #ifdef CONFIG_TMPFS
  89 static unsigned long shmem_default_max_blocks(void)
  90 {
  91         return totalram_pages / 2;
  92 }
  93
  94 static unsigned long shmem_default_max_inodes(void)
  95 {
  96         return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
  97 }
  98 #endif
  99
 100 static int shmem_getpage(struct inode *inode, unsigned long idx,
 101                          struct page **pagep, enum sgp_type sgp, int *type);
 102
 103 static inline struct page *shmem_dir_alloc(gfp_t gfp_mask)
 104 {
 105         /*
 106          * The above definition of ENTRIES_PER_PAGE, and the use of
 107          * BLOCKS_PER_PAGE on indirect pages, assume PAGE_CACHE_SIZE:
 108          * might be reconsidered if it ever diverges from PAGE_SIZE.
 109          *
 110          * Mobility flags are masked out as swap vectors cannot move
 111          */
 112         return alloc_pages((gfp_mask & ~GFP_MOVABLE_MASK) | __GFP_ZERO,
 113                                 PAGE_CACHE_SHIFT-PAGE_SHIFT);
 114 }
 115
 116 static inline void shmem_dir_free(struct page *page)
 117 {
 118         __free_pages(page, PAGE_CACHE_SHIFT-PAGE_SHIFT);
 119 }
 120
 121 static struct page **shmem_dir_map(struct page *page)
 122 {
 123         return (struct page **)kmap_atomic(page, KM_USER0);
 124 }
 125
 126 static inline void shmem_dir_unmap(struct page **dir)
 127 {
 128         kunmap_atomic(dir, KM_USER0);
 129 }
 130
 131 static swp_entry_t *shmem_swp_map(struct page *page)
 132 {
 133         return (swp_entry_t *)kmap_atomic(page, KM_USER1);
 134 }
 135
 136 static inline void shmem_swp_balance_unmap(void)
 137 {
 138         /*
 139          * When passing a pointer to an i_direct entry, to code which
 140          * also handles indirect entries and so will shmem_swp_unmap,
 141          * we must arrange for the preempt count to remain in balance.
 142          * What kmap_atomic of a lowmem page does depends on config
 143          * and architecture, so pretend to kmap_atomic some lowmem page.
 144          */
 145         (void) kmap_atomic(ZERO_PAGE(0), KM_USER1);
 146 }
 147
 148 static inline void shmem_swp_unmap(swp_entry_t *entry)
 149 {
 150         kunmap_atomic(entry, KM_USER1);
 151 }
 152
 153 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
 154 {
 155         return sb->s_fs_info;
 156 }
 157
 158 /*
 159  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
 160  * for shared memory and for shared anonymous (/dev/zero) mappings
 161  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
 162  * consistent with the pre-accounting of private mappings ...
 163  */
 164 static inline int shmem_acct_size(unsigned long flags, loff_t size)
 165 {
 166         return (flags & VM_ACCOUNT)?
 167                 security_vm_enough_memory(VM_ACCT(size)): 0;
 168 }
 169
 170 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
 171 {
 172         if (flags & VM_ACCOUNT)
 173                 vm_unacct_memory(VM_ACCT(size));
 174 }
 175
 176 /*
 177  * ... whereas tmpfs objects are accounted incrementally as
 178  * pages are allocated, in order to allow huge sparse files.
 179  * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
 180  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
 181  */
 182 static inline int shmem_acct_block(unsigned long flags)
 183 {
 184         return (flags & VM_ACCOUNT)?
 185                 0: security_vm_enough_memory(VM_ACCT(PAGE_CACHE_SIZE));
 186 }
 187
 188 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
 189 {
 190         if (!(flags & VM_ACCOUNT))
 191                 vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
 192 }
 193
 194 static const struct super_operations shmem_ops;
 195 static const struct address_space_operations shmem_aops;
 196 static const struct file_operations shmem_file_operations;
 197 static const struct inode_operations shmem_inode_operations;
 198 static const struct inode_operations shmem_dir_inode_operations;
 199 static const struct inode_operations shmem_special_inode_operations;
 200 static struct vm_operations_struct shmem_vm_ops;
 201
 202 static struct backing_dev_info shmem_backing_dev_info  __read_mostly = {
 203         .ra_pages       = 0,    /* No readahead */
 204         .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
 205         .unplug_io_fn   = default_unplug_io_fn,
 206 };
 207
 208 static LIST_HEAD(shmem_swaplist);
 209 static DEFINE_MUTEX(shmem_swaplist_mutex);
 210
 211 static void shmem_free_blocks(struct inode *inode, long pages)
 212 {
 213         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 214         if (sbinfo->max_blocks) {
 215                 spin_lock(&sbinfo->stat_lock);
 216                 sbinfo->free_blocks += pages;
 217                 inode->i_blocks -= pages*BLOCKS_PER_PAGE;
 218                 spin_unlock(&sbinfo->stat_lock);
 219         }
 220 }
 221
 222 static int shmem_reserve_inode(struct super_block *sb)
 223 {
 224         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
 225         if (sbinfo->max_inodes) {
 226                 spin_lock(&sbinfo->stat_lock);
 227                 if (!sbinfo->free_inodes) {
 228                         spin_unlock(&sbinfo->stat_lock);
 229                         return -ENOSPC;
 230                 }
 231                 sbinfo->free_inodes--;
 232                 spin_unlock(&sbinfo->stat_lock);
 233         }
 234         return 0;
 235 }
 236
 237 static void shmem_free_inode(struct super_block *sb)
 238 {
 239         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
 240         if (sbinfo->max_inodes) {
 241                 spin_lock(&sbinfo->stat_lock);
 242                 sbinfo->free_inodes++;
 243                 spin_unlock(&sbinfo->stat_lock);
 244         }
 245 }
 246
 247 /**
 248  * shmem_recalc_inode - recalculate the size of an inode
 249  * @inode: inode to recalc
 250  *
 251  * We have to calculate the free blocks since the mm can drop
 252  * undirtied hole pages behind our back.
 253  *
 254  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
 255  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
 256  *
 257  * It has to be called with the spinlock held.
 258  */
 259 static void shmem_recalc_inode(struct inode *inode)
 260 {
 261         struct shmem_inode_info *info = SHMEM_I(inode);
 262         long freed;
 263
 264         freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
 265         if (freed > 0) {
 266                 info->alloced -= freed;
 267                 shmem_unacct_blocks(info->flags, freed);
 268                 shmem_free_blocks(inode, freed);
 269         }
 270 }
 271
 272 /**
 273  * shmem_swp_entry - find the swap vector position in the info structure
 274  * @info:  info structure for the inode
 275  * @index: index of the page to find
 276  * @page:  optional page to add to the structure. Has to be preset to
 277  *         all zeros
 278  *
 279  * If there is no space allocated yet it will return NULL when
 280  * page is NULL, else it will use the page for the needed block,
 281  * setting it to NULL on return to indicate that it has been used.
 282  *
 283  * The swap vector is organized the following way:
 284  *
 285  * There are SHMEM_NR_DIRECT entries directly stored in the
 286  * shmem_inode_info structure. So small files do not need an addional
 287  * allocation.
 288  *
 289  * For pages with index > SHMEM_NR_DIRECT there is the pointer
 290  * i_indirect which points to a page which holds in the first half
 291  * doubly indirect blocks, in the second half triple indirect blocks:
 292  *
 293  * For an artificial ENTRIES_PER_PAGE = 4 this would lead to the
 294  * following layout (for SHMEM_NR_DIRECT == 16):
 295  *
 296  * i_indirect -> dir --> 16-19
 297  *            |      +-> 20-23
 298  *            |
 299  *            +-->dir2 --> 24-27
 300  *            |        +-> 28-31
 301  *            |        +-> 32-35
 302  *            |        +-> 36-39
 303  *            |
 304  *            +-->dir3 --> 40-43
 305  *                     +-> 44-47
 306  *                     +-> 48-51
 307  *                     +-> 52-55
 308  */
 309 static swp_entry_t *shmem_swp_entry(struct shmem_inode_info *info, unsigned long index, struct page **page)
 310 {
 311         unsigned long offset;
 312         struct page **dir;
 313         struct page *subdir;
 314
 315         if (index < SHMEM_NR_DIRECT) {
 316                 shmem_swp_balance_unmap();
 317                 return info->i_direct+index;
 318         }
 319         if (!info->i_indirect) {
 320                 if (page) {
 321                         info->i_indirect = *page;
 322                         *page = NULL;
 323                 }
 324                 return NULL;                    /* need another page */
 325         }
 326
 327         index -= SHMEM_NR_DIRECT;
 328         offset = index % ENTRIES_PER_PAGE;
 329         index /= ENTRIES_PER_PAGE;
 330         dir = shmem_dir_map(info->i_indirect);
 331
 332         if (index >= ENTRIES_PER_PAGE/2) {
 333                 index -= ENTRIES_PER_PAGE/2;
 334                 dir += ENTRIES_PER_PAGE/2 + index/ENTRIES_PER_PAGE;
 335                 index %= ENTRIES_PER_PAGE;
 336                 subdir = *dir;
 337                 if (!subdir) {
 338                         if (page) {
 339                                 *dir = *page;
 340                                 *page = NULL;
 341                         }
 342                         shmem_dir_unmap(dir);
 343                         return NULL;            /* need another page */
 344                 }
 345                 shmem_dir_unmap(dir);
 346                 dir = shmem_dir_map(subdir);
 347         }
 348
 349         dir += index;
 350         subdir = *dir;
 351         if (!subdir) {
 352                 if (!page || !(subdir = *page)) {
 353                         shmem_dir_unmap(dir);
 354                         return NULL;            /* need a page */
 355                 }
 356                 *dir = subdir;
 357                 *page = NULL;
 358         }
 359         shmem_dir_unmap(dir);
 360         return shmem_swp_map(subdir) + offset;
 361 }
 362
 363 static void shmem_swp_set(struct shmem_inode_info *info, swp_entry_t *entry, unsigned long value)
 364 {
 365         long incdec = value? 1: -1;
 366
 367         entry->val = value;
 368         info->swapped += incdec;
 369         if ((unsigned long)(entry - info->i_direct) >= SHMEM_NR_DIRECT) {
 370                 struct page *page = kmap_atomic_to_page(entry);
 371                 set_page_private(page, page_private(page) + incdec);
 372         }
 373 }
 374
 375 /**
 376  * shmem_swp_alloc - get the position of the swap entry for the page.
 377  * @info:       info structure for the inode
 378  * @index:      index of the page to find
 379  * @sgp:        check and recheck i_size? skip allocation?
 380  *
 381  * If the entry does not exist, allocate it.
 382  */
 383 static swp_entry_t *shmem_swp_alloc(struct shmem_inode_info *info, unsigned long index, enum sgp_type sgp)
 384 {
 385         struct inode *inode = &info->vfs_inode;
 386         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 387         struct page *page = NULL;
 388         swp_entry_t *entry;
 389
 390         if (sgp != SGP_WRITE &&
 391             ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode))
 392                 return ERR_PTR(-EINVAL);
 393
 394         while (!(entry = shmem_swp_entry(info, index, &page))) {
 395                 if (sgp == SGP_READ)
 396                         return shmem_swp_map(ZERO_PAGE(0));
 397                 /*
 398                  * Test free_blocks against 1 not 0, since we have 1 data
 399                  * page (and perhaps indirect index pages) yet to allocate:
 400                  * a waste to allocate index if we cannot allocate data.
 401                  */
 402                 if (sbinfo->max_blocks) {
 403                         spin_lock(&sbinfo->stat_lock);
 404                         if (sbinfo->free_blocks <= 1) {
 405                                 spin_unlock(&sbinfo->stat_lock);
 406                                 return ERR_PTR(-ENOSPC);
 407                         }
 408                         sbinfo->free_blocks--;
 409                         inode->i_blocks += BLOCKS_PER_PAGE;
 410                         spin_unlock(&sbinfo->stat_lock);
 411                 }
 412
 413                 spin_unlock(&info->lock);
 414                 page = shmem_dir_alloc(mapping_gfp_mask(inode->i_mapping));
 415                 if (page)
 416                         set_page_private(page, 0);
 417                 spin_lock(&info->lock);
 418
 419                 if (!page) {
 420                         shmem_free_blocks(inode, 1);
 421                         return ERR_PTR(-ENOMEM);
 422                 }
 423                 if (sgp != SGP_WRITE &&
 424                     ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
 425                         entry = ERR_PTR(-EINVAL);
 426                         break;
 427                 }
 428                 if (info->next_index <= index)
 429                         info->next_index = index + 1;
 430         }
 431         if (page) {
 432                 /* another task gave its page, or truncated the file */
 433                 shmem_free_blocks(inode, 1);
 434                 shmem_dir_free(page);
 435         }
 436         if (info->next_index <= index && !IS_ERR(entry))
 437                 info->next_index = index + 1;
 438         return entry;
 439 }
 440
 441 /**
 442  * shmem_free_swp - free some swap entries in a directory
 443  * @dir:        pointer to the directory
 444  * @edir:       pointer after last entry of the directory
 445  * @punch_lock: pointer to spinlock when needed for the holepunch case
 446  */
 447 static int shmem_free_swp(swp_entry_t *dir, swp_entry_t *edir,
 448                                                 spinlock_t *punch_lock)
 449 {
 450         spinlock_t *punch_unlock = NULL;
 451         swp_entry_t *ptr;
 452         int freed = 0;
 453
 454         for (ptr = dir; ptr < edir; ptr++) {
 455                 if (ptr->val) {
 456                         if (unlikely(punch_lock)) {
 457                                 punch_unlock = punch_lock;
 458                                 punch_lock = NULL;
 459                                 spin_lock(punch_unlock);
 460                                 if (!ptr->val)
 461                                         continue;
 462                         }
 463                         free_swap_and_cache(*ptr);
 464                         *ptr = (swp_entry_t){0};
 465                         freed++;
 466                 }
 467         }
 468         if (punch_unlock)
 469                 spin_unlock(punch_unlock);
 470         return freed;
 471 }
 472
 473 static int shmem_map_and_free_swp(struct page *subdir, int offset,
 474                 int limit, struct page ***dir, spinlock_t *punch_lock)
 475 {
 476         swp_entry_t *ptr;
 477         int freed = 0;
 478
 479         ptr = shmem_swp_map(subdir);
 480         for (; offset < limit; offset += LATENCY_LIMIT) {
 481                 int size = limit - offset;
 482                 if (size > LATENCY_LIMIT)
 483                         size = LATENCY_LIMIT;
 484                 freed += shmem_free_swp(ptr+offset, ptr+offset+size,
 485                                                         punch_lock);
 486                 if (need_resched()) {
 487                         shmem_swp_unmap(ptr);
 488                         if (*dir) {
 489                                 shmem_dir_unmap(*dir);
 490                                 *dir = NULL;
 491                         }
 492                         cond_resched();
 493                         ptr = shmem_swp_map(subdir);
 494                 }
 495         }
 496         shmem_swp_unmap(ptr);
 497         return freed;
 498 }
 499
 500 static void shmem_free_pages(struct list_head *next)
 501 {
 502         struct page *page;
 503         int freed = 0;
 504
 505         do {
 506                 page = container_of(next, struct page, lru);
 507                 next = next->next;
 508                 shmem_dir_free(page);
 509                 freed++;
 510                 if (freed >= LATENCY_LIMIT) {
 511                         cond_resched();
 512                         freed = 0;
 513                 }
 514         } while (next);
 515 }
 516
 517 static void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end)
 518 {
 519         struct shmem_inode_info *info = SHMEM_I(inode);
 520         unsigned long idx;
 521         unsigned long size;
 522         unsigned long limit;
 523         unsigned long stage;
 524         unsigned long diroff;
 525         struct page **dir;
 526         struct page *topdir;
 527         struct page *middir;
 528         struct page *subdir;
 529         swp_entry_t *ptr;
 530         LIST_HEAD(pages_to_free);
 531         long nr_pages_to_free = 0;
 532         long nr_swaps_freed = 0;
 533         int offset;
 534         int freed;
 535         int punch_hole;
 536         spinlock_t *needs_lock;
 537         spinlock_t *punch_lock;
 538         unsigned long upper_limit;
 539
 540         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
 541         idx = (start + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 542         if (idx >= info->next_index)
 543                 return;
 544
 545         spin_lock(&info->lock);
 546         info->flags |= SHMEM_TRUNCATE;
 547         if (likely(end == (loff_t) -1)) {
 548                 limit = info->next_index;
 549                 upper_limit = SHMEM_MAX_INDEX;
 550                 info->next_index = idx;
 551                 needs_lock = NULL;
 552                 punch_hole = 0;
 553         } else {
 554                 if (end + 1 >= inode->i_size) { /* we may free a little more */
 555                         limit = (inode->i_size + PAGE_CACHE_SIZE - 1) >>
 556                                                         PAGE_CACHE_SHIFT;
 557                         upper_limit = SHMEM_MAX_INDEX;
 558                 } else {
 559                         limit = (end + 1) >> PAGE_CACHE_SHIFT;
 560                         upper_limit = limit;
 561                 }
 562                 needs_lock = &info->lock;
 563                 punch_hole = 1;
 564         }
 565
 566         topdir = info->i_indirect;
 567         if (topdir && idx <= SHMEM_NR_DIRECT && !punch_hole) {
 568                 info->i_indirect = NULL;
 569                 nr_pages_to_free++;
 570                 list_add(&topdir->lru, &pages_to_free);
 571         }
 572         spin_unlock(&info->lock);
 573
 574         if (info->swapped && idx < SHMEM_NR_DIRECT) {
 575                 ptr = info->i_direct;
 576                 size = limit;
 577                 if (size > SHMEM_NR_DIRECT)
 578                         size = SHMEM_NR_DIRECT;
 579                 nr_swaps_freed = shmem_free_swp(ptr+idx, ptr+size, needs_lock);
 580         }
 581
 582         /*
 583          * If there are no indirect blocks or we are punching a hole
 584          * below indirect blocks, nothing to be done.
 585          */
 586         if (!topdir || limit <= SHMEM_NR_DIRECT)
 587                 goto done2;
 588
 589         /*
 590          * The truncation case has already dropped info->lock, and we're safe
 591          * because i_size and next_index have already been lowered, preventing
 592          * access beyond.  But in the punch_hole case, we still need to take
 593          * the lock when updating the swap directory, because there might be
 594          * racing accesses by shmem_getpage(SGP_CACHE), shmem_unuse_inode or
 595          * shmem_writepage.  However, whenever we find we can remove a whole
 596          * directory page (not at the misaligned start or end of the range),
 597          * we first NULLify its pointer in the level above, and then have no
 598          * need to take the lock when updating its contents: needs_lock and
 599          * punch_lock (either pointing to info->lock or NULL) manage this.
 600          */
 601
 602         upper_limit -= SHMEM_NR_DIRECT;
 603         limit -= SHMEM_NR_DIRECT;
 604         idx = (idx > SHMEM_NR_DIRECT)? (idx - SHMEM_NR_DIRECT): 0;
 605         offset = idx % ENTRIES_PER_PAGE;
 606         idx -= offset;
 607
 608         dir = shmem_dir_map(topdir);
 609         stage = ENTRIES_PER_PAGEPAGE/2;
 610         if (idx < ENTRIES_PER_PAGEPAGE/2) {
 611                 middir = topdir;
 612                 diroff = idx/ENTRIES_PER_PAGE;
 613         } else {
 614                 dir += ENTRIES_PER_PAGE/2;
 615                 dir += (idx - ENTRIES_PER_PAGEPAGE/2)/ENTRIES_PER_PAGEPAGE;
 616                 while (stage <= idx)
 617                         stage += ENTRIES_PER_PAGEPAGE;
 618                 middir = *dir;
 619                 if (*dir) {
 620                         diroff = ((idx - ENTRIES_PER_PAGEPAGE/2) %
 621                                 ENTRIES_PER_PAGEPAGE) / ENTRIES_PER_PAGE;
 622                         if (!diroff && !offset && upper_limit >= stage) {
 623                                 if (needs_lock) {
 624                                         spin_lock(needs_lock);
 625                                         *dir = NULL;
 626                                         spin_unlock(needs_lock);
 627                                         needs_lock = NULL;
 628                                 } else
 629                                         *dir = NULL;
 630                                 nr_pages_to_free++;
 631                                 list_add(&middir->lru, &pages_to_free);
 632                         }
 633                         shmem_dir_unmap(dir);
 634                         dir = shmem_dir_map(middir);
 635                 } else {
 636                         diroff = 0;
 637                         offset = 0;
 638                         idx = stage;
 639                 }
 640         }
 641
 642         for (; idx < limit; idx += ENTRIES_PER_PAGE, diroff++) {
 643                 if (unlikely(idx == stage)) {
 644                         shmem_dir_unmap(dir);
 645                         dir = shmem_dir_map(topdir) +
 646                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
 647                         while (!*dir) {
 648                                 dir++;
 649                                 idx += ENTRIES_PER_PAGEPAGE;
 650                                 if (idx >= limit)
 651                                         goto done1;
 652                         }
 653                         stage = idx + ENTRIES_PER_PAGEPAGE;
 654                         middir = *dir;
 655                         if (punch_hole)
 656                                 needs_lock = &info->lock;
 657                         if (upper_limit >= stage) {
 658                                 if (needs_lock) {
 659                                         spin_lock(needs_lock);
 660                                         *dir = NULL;
 661                                         spin_unlock(needs_lock);
 662                                         needs_lock = NULL;
 663                                 } else
 664                                         *dir = NULL;
 665                                 nr_pages_to_free++;
 666                                 list_add(&middir->lru, &pages_to_free);
 667                         }
 668                         shmem_dir_unmap(dir);
 669                         cond_resched();
 670                         dir = shmem_dir_map(middir);
 671                         diroff = 0;
 672                 }
 673                 punch_lock = needs_lock;
 674                 subdir = dir[diroff];
 675                 if (subdir && !offset && upper_limit-idx >= ENTRIES_PER_PAGE) {
 676                         if (needs_lock) {
 677                                 spin_lock(needs_lock);
 678                                 dir[diroff] = NULL;
 679                                 spin_unlock(needs_lock);
 680                                 punch_lock = NULL;
 681                         } else
 682                                 dir[diroff] = NULL;
 683                         nr_pages_to_free++;
 684                         list_add(&subdir->lru, &pages_to_free);
 685                 }
 686                 if (subdir && page_private(subdir) /* has swap entries */) {
 687                         size = limit - idx;
 688                         if (size > ENTRIES_PER_PAGE)
 689                                 size = ENTRIES_PER_PAGE;
 690                         freed = shmem_map_and_free_swp(subdir,
 691                                         offset, size, &dir, punch_lock);
 692                         if (!dir)
 693                                 dir = shmem_dir_map(middir);
 694                         nr_swaps_freed += freed;
 695                         if (offset || punch_lock) {
 696                                 spin_lock(&info->lock);
 697                                 set_page_private(subdir,
 698                                         page_private(subdir) - freed);
 699                                 spin_unlock(&info->lock);
 700                         } else
 701                                 BUG_ON(page_private(subdir) != freed);
 702                 }
 703                 offset = 0;
 704         }
 705 done1:
 706         shmem_dir_unmap(dir);
 707 done2:
 708         if (inode->i_mapping->nrpages && (info->flags & SHMEM_PAGEIN)) {
 709                 /*
 710                  * Call truncate_inode_pages again: racing shmem_unuse_inode
 711                  * may have swizzled a page in from swap since vmtruncate or
 712                  * generic_delete_inode did it, before we lowered next_index.
 713                  * Also, though shmem_getpage checks i_size before adding to
 714                  * cache, no recheck after: so fix the narrow window there too.
 715                  *
 716                  * Recalling truncate_inode_pages_range and unmap_mapping_range
 717                  * every time for punch_hole (which never got a chance to clear
 718                  * SHMEM_PAGEIN at the start of vmtruncate_range) is expensive,
 719                  * yet hardly ever necessary: try to optimize them out later.
 720                  */
 721                 truncate_inode_pages_range(inode->i_mapping, start, end);
 722                 if (punch_hole)
 723                         unmap_mapping_range(inode->i_mapping, start,
 724                                                         end - start, 1);
 725         }
 726
 727         spin_lock(&info->lock);
 728         info->flags &= ~SHMEM_TRUNCATE;
 729         info->swapped -= nr_swaps_freed;
 730         if (nr_pages_to_free)
 731                 shmem_free_blocks(inode, nr_pages_to_free);
 732         shmem_recalc_inode(inode);
 733         spin_unlock(&info->lock);
 734
 735         /*
 736          * Empty swap vector directory pages to be freed?
 737          */
 738         if (!list_empty(&pages_to_free)) {
 739                 pages_to_free.prev->next = NULL;
 740                 shmem_free_pages(pages_to_free.next);
 741         }
 742 }
 743
 744 static void shmem_truncate(struct inode *inode)
 745 {
 746         shmem_truncate_range(inode, inode->i_size, (loff_t)-1);
 747 }
 748
 749 static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
 750 {
 751         struct inode *inode = dentry->d_inode;
 752         struct page *page = NULL;
 753         int error;
 754
 755         if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
 756                 if (attr->ia_size < inode->i_size) {
 757                         /*
 758                          * If truncating down to a partial page, then
 759                          * if that page is already allocated, hold it
 760                          * in memory until the truncation is over, so
 761                          * truncate_partial_page cannnot miss it were
 762                          * it assigned to swap.
 763                          */
 764                         if (attr->ia_size & (PAGE_CACHE_SIZE-1)) {
 765                                 (void) shmem_getpage(inode,
 766                                         attr->ia_size>>PAGE_CACHE_SHIFT,
 767                                                 &page, SGP_READ, NULL);
 768                                 if (page)
 769                                         unlock_page(page);
 770                         }
 771                         /*
 772                          * Reset SHMEM_PAGEIN flag so that shmem_truncate can
 773                          * detect if any pages might have been added to cache
 774                          * after truncate_inode_pages.  But we needn't bother
 775                          * if it's being fully truncated to zero-length: the
 776                          * nrpages check is efficient enough in that case.
 777                          */
 778                         if (attr->ia_size) {
 779                                 struct shmem_inode_info *info = SHMEM_I(inode);
 780                                 spin_lock(&info->lock);
 781                                 info->flags &= ~SHMEM_PAGEIN;
 782                                 spin_unlock(&info->lock);
 783                         }
 784                 }
 785         }
 786
 787         error = inode_change_ok(inode, attr);
 788         if (!error)
 789                 error = inode_setattr(inode, attr);
 790 #ifdef CONFIG_TMPFS_POSIX_ACL
 791         if (!error && (attr->ia_valid & ATTR_MODE))
 792                 error = generic_acl_chmod(inode, &shmem_acl_ops);
 793 #endif
 794         if (page)
 795                 page_cache_release(page);
 796         return error;
 797 }
 798
 799 static void shmem_delete_inode(struct inode *inode)
 800 {
 801         struct shmem_inode_info *info = SHMEM_I(inode);
 802
 803         if (inode->i_op->truncate == shmem_truncate) {
 804                 truncate_inode_pages(inode->i_mapping, 0);
 805                 shmem_unacct_size(info->flags, inode->i_size);
 806                 inode->i_size = 0;
 807                 shmem_truncate(inode);
 808                 if (!list_empty(&info->swaplist)) {
 809                         mutex_lock(&shmem_swaplist_mutex);
 810                         list_del_init(&info->swaplist);
 811                         mutex_unlock(&shmem_swaplist_mutex);
 812                 }
 813         }
 814         BUG_ON(inode->i_blocks);
 815         shmem_free_inode(inode->i_sb);
 816         clear_inode(inode);
 817 }
 818
 819 static inline int shmem_find_swp(swp_entry_t entry, swp_entry_t *dir, swp_entry_t *edir)
 820 {
 821         swp_entry_t *ptr;
 822
 823         for (ptr = dir; ptr < edir; ptr++) {
 824                 if (ptr->val == entry.val)
 825                         return ptr - dir;
 826         }
 827         return -1;
 828 }
 829
 830 static int shmem_unuse_inode(struct shmem_inode_info *info, swp_entry_t entry, struct page *page)
 831 {
 832         struct inode *inode;
 833         unsigned long idx;
 834         unsigned long size;
 835         unsigned long limit;
 836         unsigned long stage;
 837         struct page **dir;
 838         struct page *subdir;
 839         swp_entry_t *ptr;
 840         int offset;
 841         int error;
 842
 843         idx = 0;
 844         ptr = info->i_direct;
 845         spin_lock(&info->lock);
 846         if (!info->swapped) {
 847                 list_del_init(&info->swaplist);
 848                 goto lost2;
 849         }
 850         limit = info->next_index;
 851         size = limit;
 852         if (size > SHMEM_NR_DIRECT)
 853                 size = SHMEM_NR_DIRECT;
 854         offset = shmem_find_swp(entry, ptr, ptr+size);
 855         if (offset >= 0)
 856                 goto found;
 857         if (!info->i_indirect)
 858                 goto lost2;
 859
 860         dir = shmem_dir_map(info->i_indirect);
 861         stage = SHMEM_NR_DIRECT + ENTRIES_PER_PAGEPAGE/2;
 862
 863         for (idx = SHMEM_NR_DIRECT; idx < limit; idx += ENTRIES_PER_PAGE, dir++) {
 864                 if (unlikely(idx == stage)) {
 865                         shmem_dir_unmap(dir-1);
 866                         if (cond_resched_lock(&info->lock)) {
 867                                 /* check it has not been truncated */
 868                                 if (limit > info->next_index) {
 869                                         limit = info->next_index;
 870                                         if (idx >= limit)
 871                                                 goto lost2;
 872                                 }
 873                         }
 874                         dir = shmem_dir_map(info->i_indirect) +
 875                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
 876                         while (!*dir) {
 877                                 dir++;
 878                                 idx += ENTRIES_PER_PAGEPAGE;
 879                                 if (idx >= limit)
 880                                         goto lost1;
 881                         }
 882                         stage = idx + ENTRIES_PER_PAGEPAGE;
 883                         subdir = *dir;
 884                         shmem_dir_unmap(dir);
 885                         dir = shmem_dir_map(subdir);
 886                 }
 887                 subdir = *dir;
 888                 if (subdir && page_private(subdir)) {
 889                         ptr = shmem_swp_map(subdir);
 890                         size = limit - idx;
 891                         if (size > ENTRIES_PER_PAGE)
 892                                 size = ENTRIES_PER_PAGE;
 893                         offset = shmem_find_swp(entry, ptr, ptr+size);
 894                         shmem_swp_unmap(ptr);
 895                         if (offset >= 0) {
 896                                 shmem_dir_unmap(dir);
 897                                 goto found;
 898                         }
 899                 }
 900         }
 901 lost1:
 902         shmem_dir_unmap(dir-1);
 903 lost2:
 904         spin_unlock(&info->lock);
 905         return 0;
 906 found:
 907         idx += offset;
 908         inode = igrab(&info->vfs_inode);
 909         spin_unlock(&info->lock);
 910
 911         /*
 912          * Move _head_ to start search for next from here.
 913          * But be careful: shmem_delete_inode checks list_empty without taking
 914          * mutex, and there's an instant in list_move_tail when info->swaplist
 915          * would appear empty, if it were the only one on shmem_swaplist.  We
 916          * could avoid doing it if inode NULL; or use this minor optimization.
 917          */
 918         if (shmem_swaplist.next != &info->swaplist)
 919                 list_move_tail(&shmem_swaplist, &info->swaplist);
 920         mutex_unlock(&shmem_swaplist_mutex);
 921
 922         error = 1;
 923         if (!inode)
 924                 goto out;
 925         /* Precharge page while we can wait, compensate afterwards */
 926         error = mem_cgroup_cache_charge(page, current->mm, GFP_KERNEL);
 927         if (error)
 928                 goto out;
 929         error = radix_tree_preload(GFP_KERNEL);
 930         if (error)
 931                 goto uncharge;
 932         error = 1;
 933
 934         spin_lock(&info->lock);
 935         ptr = shmem_swp_entry(info, idx, NULL);
 936         if (ptr && ptr->val == entry.val)
 937                 error = add_to_page_cache(page, inode->i_mapping,
 938                                                 idx, GFP_NOWAIT);
 939         if (error == -EEXIST) {
 940                 struct page *filepage = find_get_page(inode->i_mapping, idx);
 941                 error = 1;
 942                 if (filepage) {
 943                         /*
 944                          * There might be a more uptodate page coming down
 945                          * from a stacked writepage: forget our swappage if so.
 946                          */
 947                         if (PageUptodate(filepage))
 948                                 error = 0;
 949                         page_cache_release(filepage);
 950                 }
 951         }
 952         if (!error) {
 953                 delete_from_swap_cache(page);
 954                 set_page_dirty(page);
 955                 info->flags |= SHMEM_PAGEIN;
 956                 shmem_swp_set(info, ptr, 0);
 957                 swap_free(entry);
 958                 error = 1;      /* not an error, but entry was found */
 959         }
 960         if (ptr)
 961                 shmem_swp_unmap(ptr);
 962         spin_unlock(&info->lock);
 963         radix_tree_preload_end();
 964 uncharge:
 965         mem_cgroup_uncharge_page(page);
 966 out:
 967         unlock_page(page);
 968         page_cache_release(page);
 969         iput(inode);            /* allows for NULL */
 970         return error;
 971 }
 972
 973 /*
 974  * shmem_unuse() search for an eventually swapped out shmem page.
 975  */
 976 int shmem_unuse(swp_entry_t entry, struct page *page)
 977 {
 978         struct list_head *p, *next;
 979         struct shmem_inode_info *info;
 980         int found = 0;
 981
 982         mutex_lock(&shmem_swaplist_mutex);
 983         list_for_each_safe(p, next, &shmem_swaplist) {
 984                 info = list_entry(p, struct shmem_inode_info, swaplist);
 985                 found = shmem_unuse_inode(info, entry, page);
 986                 cond_resched();
 987                 if (found)
 988                         goto out;
 989         }
 990         mutex_unlock(&shmem_swaplist_mutex);
 991 out:    return found;   /* 0 or 1 or -ENOMEM */
 992 }
 993
 994 /*
 995  * Move the page from the page cache to the swap cache.
 996  */
 997 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 998 {
 999         struct shmem_inode_info *info;
1000         swp_entry_t *entry, swap;
1001         struct address_space *mapping;
1002         unsigned long index;
1003         struct inode *inode;
1004
1005         BUG_ON(!PageLocked(page));
1006         mapping = page->mapping;
1007         index = page->index;
1008         inode = mapping->host;
1009         info = SHMEM_I(inode);
1010         if (info->flags & VM_LOCKED)
1011                 goto redirty;
1012         if (!total_swap_pages)
1013                 goto redirty;
1014
1015         /*
1016          * shmem_backing_dev_info's capabilities prevent regular writeback or
1017          * sync from ever calling shmem_writepage; but a stacking filesystem
1018          * may use the ->writepage of its underlying filesystem, in which case
1019          * tmpfs should write out to swap only in response to memory pressure,
1020          * and not for pdflush or sync.  However, in those cases, we do still
1021          * want to check if there's a redundant swappage to be discarded.
1022          */
1023         if (wbc->for_reclaim)
1024                 swap = get_swap_page();
1025         else
1026                 swap.val = 0;
1027
1028         spin_lock(&info->lock);
1029         if (index >= info->next_index) {
1030                 BUG_ON(!(info->flags & SHMEM_TRUNCATE));
1031                 goto unlock;
1032         }
1033         entry = shmem_swp_entry(info, index, NULL);
1034         if (entry->val) {
1035                 /*
1036                  * The more uptodate page coming down from a stacked
1037                  * writepage should replace our old swappage.
1038                  */
1039                 free_swap_and_cache(*entry);
1040                 shmem_swp_set(info, entry, 0);
1041         }
1042         shmem_recalc_inode(inode);
1043
1044         if (swap.val && add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
1045                 remove_from_page_cache(page);
1046                 shmem_swp_set(info, entry, swap.val);
1047                 shmem_swp_unmap(entry);
1048                 if (list_empty(&info->swaplist))
1049                         inode = igrab(inode);
1050                 else
1051                         inode = NULL;
1052                 spin_unlock(&info->lock);
1053                 swap_duplicate(swap);
1054                 BUG_ON(page_mapped(page));
1055                 page_cache_release(page);       /* pagecache ref */
1056                 set_page_dirty(page);
1057                 unlock_page(page);
1058                 if (inode) {
1059                         mutex_lock(&shmem_swaplist_mutex);
1060                         /* move instead of add in case we're racing */
1061                         list_move_tail(&info->swaplist, &shmem_swaplist);
1062                         mutex_unlock(&shmem_swaplist_mutex);
1063                         iput(inode);
1064                 }
1065                 return 0;
1066         }
1067
1068         shmem_swp_unmap(entry);
1069 unlock:
1070         spin_unlock(&info->lock);
1071         swap_free(swap);
1072 redirty:
1073         set_page_dirty(page);
1074         if (wbc->for_reclaim)
1075                 return AOP_WRITEPAGE_ACTIVATE;  /* Return with page locked */
1076         unlock_page(page);
1077         return 0;
1078 }
1079
1080 #ifdef CONFIG_NUMA
1081 #ifdef CONFIG_TMPFS
1082 static int shmem_parse_mpol(char *value, int *policy, nodemask_t *policy_nodes)
1083 {
1084         char *nodelist = strchr(value, ':');
1085         int err = 1;
1086
1087         if (nodelist) {
1088                 /* NUL-terminate policy string */
1089                 *nodelist++ = '\0';
1090                 if (nodelist_parse(nodelist, *policy_nodes))
1091                         goto out;
1092                 if (!nodes_subset(*policy_nodes, node_states[N_HIGH_MEMORY]))
1093                         goto out;
1094         }
1095         if (!strcmp(value, "default")) {
1096                 *policy = MPOL_DEFAULT;
1097                 /* Don't allow a nodelist */
1098                 if (!nodelist)
1099                         err = 0;
1100         } else if (!strcmp(value, "prefer")) {
1101                 *policy = MPOL_PREFERRED;
1102                 /* Insist on a nodelist of one node only */
1103                 if (nodelist) {
1104                         char *rest = nodelist;
1105                         while (isdigit(*rest))
1106                                 rest++;
1107                         if (!*rest)
1108                                 err = 0;
1109                 }
1110         } else if (!strcmp(value, "bind")) {
1111                 *policy = MPOL_BIND;
1112                 /* Insist on a nodelist */
1113                 if (nodelist)
1114                         err = 0;
1115         } else if (!strcmp(value, "interleave")) {
1116                 *policy = MPOL_INTERLEAVE;
1117                 /*
1118                  * Default to online nodes with memory if no nodelist
1119                  */
1120                 if (!nodelist)
1121                         *policy_nodes = node_states[N_HIGH_MEMORY];
1122                 err = 0;
1123         }
1124 out:
1125         /* Restore string for error message */
1126         if (nodelist)
1127                 *--nodelist = ':';
1128         return err;
1129 }
1130
1131 static void shmem_show_mpol(struct seq_file *seq, int policy,
1132                             const nodemask_t policy_nodes)
1133 {
1134         char *policy_string;
1135
1136         switch (policy) {
1137         case MPOL_PREFERRED:
1138                 policy_string = "prefer";
1139                 break;
1140         case MPOL_BIND:
1141                 policy_string = "bind";
1142                 break;
1143         case MPOL_INTERLEAVE:
1144                 policy_string = "interleave";
1145                 break;
1146         default:
1147                 /* MPOL_DEFAULT */
1148                 return;
1149         }
1150
1151         seq_printf(seq, ",mpol=%s", policy_string);
1152
1153         if (policy != MPOL_INTERLEAVE ||
1154             !nodes_equal(policy_nodes, node_states[N_HIGH_MEMORY])) {
1155                 char buffer[64];
1156                 int len;
1157
1158                 len = nodelist_scnprintf(buffer, sizeof(buffer), policy_nodes);
1159                 if (len < sizeof(buffer))
1160                         seq_printf(seq, ":%s", buffer);
1161                 else
1162                         seq_printf(seq, ":?");
1163         }
1164 }
1165 #endif /* CONFIG_TMPFS */
1166
1167 static struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
1168                         struct shmem_inode_info *info, unsigned long idx)
1169 {
1170         struct vm_area_struct pvma;
1171         struct page *page;
1172
1173         /* Create a pseudo vma that just contains the policy */
1174         pvma.vm_start = 0;
1175         pvma.vm_pgoff = idx;
1176         pvma.vm_ops = NULL;
1177         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx);
1178         page = swapin_readahead(entry, gfp, &pvma, 0);
1179         mpol_free(pvma.vm_policy);
1180         return page;
1181 }
1182
1183 static struct page *shmem_alloc_page(gfp_t gfp,
1184                         struct shmem_inode_info *info, unsigned long idx)
1185 {
1186         struct vm_area_struct pvma;
1187         struct page *page;
1188
1189         /* Create a pseudo vma that just contains the policy */
1190         pvma.vm_start = 0;
1191         pvma.vm_pgoff = idx;
1192         pvma.vm_ops = NULL;
1193         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx);
1194         page = alloc_page_vma(gfp, &pvma, 0);
1195         mpol_free(pvma.vm_policy);
1196         return page;
1197 }
1198 #else /* !CONFIG_NUMA */
1199 #ifdef CONFIG_TMPFS
1200 static inline int shmem_parse_mpol(char *value, int *policy,
1201                                                 nodemask_t *policy_nodes)
1202 {
1203         return 1;
1204 }
1205
1206 static inline void shmem_show_mpol(struct seq_file *seq, int policy,
1207                             const nodemask_t policy_nodes)
1208 {
1209 }
1210 #endif /* CONFIG_TMPFS */
1211
1212 static inline struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
1213                         struct shmem_inode_info *info, unsigned long idx)
1214 {
1215         return swapin_readahead(entry, gfp, NULL, 0);
1216 }
1217
1218 static inline struct page *shmem_alloc_page(gfp_t gfp,
1219                         struct shmem_inode_info *info, unsigned long idx)
1220 {
1221         return alloc_page(gfp);
1222 }
1223 #endif /* CONFIG_NUMA */
1224
1225 /*
1226  * shmem_getpage - either get the page from swap or allocate a new one
1227  *
1228  * If we allocate a new one we do not mark it dirty. That's up to the
1229  * vm. If we swap it in we mark it dirty since we also free the swap
1230  * entry since a page cannot live in both the swap and page cache
1231  */
1232 static int shmem_getpage(struct inode *inode, unsigned long idx,
1233                         struct page **pagep, enum sgp_type sgp, int *type)
1234 {
1235         struct address_space *mapping = inode->i_mapping;
1236         struct shmem_inode_info *info = SHMEM_I(inode);
1237         struct shmem_sb_info *sbinfo;
1238         struct page *filepage = *pagep;
1239         struct page *swappage;
1240         swp_entry_t *entry;
1241         swp_entry_t swap;
1242         gfp_t gfp;
1243         int error;
1244
1245         if (idx >= SHMEM_MAX_INDEX)
1246                 return -EFBIG;
1247
1248         if (type)
1249                 *type = 0;
1250
1251         /*
1252          * Normally, filepage is NULL on entry, and either found
1253          * uptodate immediately, or allocated and zeroed, or read
1254          * in under swappage, which is then assigned to filepage.
1255          * But shmem_readpage (required for splice) passes in a locked
1256          * filepage, which may be found not uptodate by other callers
1257          * too, and may need to be copied from the swappage read in.
1258          */
1259 repeat:
1260         if (!filepage)
1261                 filepage = find_lock_page(mapping, idx);
1262         if (filepage && PageUptodate(filepage))
1263                 goto done;
1264         error = 0;
1265         gfp = mapping_gfp_mask(mapping);
1266         if (!filepage) {
1267                 /*
1268                  * Try to preload while we can wait, to not make a habit of
1269                  * draining atomic reserves; but don't latch on to this cpu.
1270                  */
1271                 error = radix_tree_preload(gfp & ~__GFP_HIGHMEM);
1272                 if (error)
1273                         goto failed;
1274                 radix_tree_preload_end();
1275         }
1276
1277         spin_lock(&info->lock);
1278         shmem_recalc_inode(inode);
1279         entry = shmem_swp_alloc(info, idx, sgp);
1280         if (IS_ERR(entry)) {
1281                 spin_unlock(&info->lock);
1282                 error = PTR_ERR(entry);
1283                 goto failed;
1284         }
1285         swap = *entry;
1286
1287         if (swap.val) {
1288                 /* Look it up and read it in.. */
1289                 swappage = lookup_swap_cache(swap);
1290                 if (!swappage) {
1291                         shmem_swp_unmap(entry);
1292                         /* here we actually do the io */
1293                         if (type && !(*type & VM_FAULT_MAJOR)) {
1294                                 __count_vm_event(PGMAJFAULT);
1295                                 *type |= VM_FAULT_MAJOR;
1296                         }
1297                         spin_unlock(&info->lock);
1298                         swappage = shmem_swapin(swap, gfp, info, idx);
1299                         if (!swappage) {
1300                                 spin_lock(&info->lock);
1301                                 entry = shmem_swp_alloc(info, idx, sgp);
1302                                 if (IS_ERR(entry))
1303                                         error = PTR_ERR(entry);
1304                                 else {
1305                                         if (entry->val == swap.val)
1306                                                 error = -ENOMEM;
1307                                         shmem_swp_unmap(entry);
1308                                 }
1309                                 spin_unlock(&info->lock);
1310                                 if (error)
1311                                         goto failed;
1312                                 goto repeat;
1313                         }
1314                         wait_on_page_locked(swappage);
1315                         page_cache_release(swappage);
1316                         goto repeat;
1317                 }
1318
1319                 /* We have to do this with page locked to prevent races */
1320                 if (TestSetPageLocked(swappage)) {
1321                         shmem_swp_unmap(entry);
1322                         spin_unlock(&info->lock);
1323                         wait_on_page_locked(swappage);
1324                         page_cache_release(swappage);
1325                         goto repeat;
1326                 }
1327                 if (PageWriteback(swappage)) {
1328                         shmem_swp_unmap(entry);
1329                         spin_unlock(&info->lock);
1330                         wait_on_page_writeback(swappage);
1331                         unlock_page(swappage);
1332                         page_cache_release(swappage);
1333                         goto repeat;
1334                 }
1335                 if (!PageUptodate(swappage)) {
1336                         shmem_swp_unmap(entry);
1337                         spin_unlock(&info->lock);
1338                         unlock_page(swappage);
1339                         page_cache_release(swappage);
1340                         error = -EIO;
1341                         goto failed;
1342                 }
1343
1344                 if (filepage) {
1345                         shmem_swp_set(info, entry, 0);
1346                         shmem_swp_unmap(entry);
1347                         delete_from_swap_cache(swappage);
1348                         spin_unlock(&info->lock);
1349                         copy_highpage(filepage, swappage);
1350                         unlock_page(swappage);
1351                         page_cache_release(swappage);
1352                         flush_dcache_page(filepage);
1353                         SetPageUptodate(filepage);
1354                         set_page_dirty(filepage);
1355                         swap_free(swap);
1356                 } else if (!(error = add_to_page_cache(
1357                                 swappage, mapping, idx, GFP_NOWAIT))) {
1358                         info->flags |= SHMEM_PAGEIN;
1359                         shmem_swp_set(info, entry, 0);
1360                         shmem_swp_unmap(entry);
1361                         delete_from_swap_cache(swappage);
1362                         spin_unlock(&info->lock);
1363                         filepage = swappage;
1364                         set_page_dirty(filepage);
1365                         swap_free(swap);
1366                 } else {
1367                         shmem_swp_unmap(entry);
1368                         spin_unlock(&info->lock);
1369                         unlock_page(swappage);
1370                         if (error == -ENOMEM) {
1371                                 /* allow reclaim from this memory cgroup */
1372                                 error = mem_cgroup_cache_charge(swappage,
1373                                         current->mm, gfp & ~__GFP_HIGHMEM);
1374                                 if (error) {
1375                                         page_cache_release(swappage);
1376                                         goto failed;
1377                                 }
1378                                 mem_cgroup_uncharge_page(swappage);
1379                         }
1380                         page_cache_release(swappage);
1381                         goto repeat;
1382                 }
1383         } else if (sgp == SGP_READ && !filepage) {
1384                 shmem_swp_unmap(entry);
1385                 filepage = find_get_page(mapping, idx);
1386                 if (filepage &&
1387                     (!PageUptodate(filepage) || TestSetPageLocked(filepage))) {
1388                         spin_unlock(&info->lock);
1389                         wait_on_page_locked(filepage);
1390                         page_cache_release(filepage);
1391                         filepage = NULL;
1392                         goto repeat;
1393                 }
1394                 spin_unlock(&info->lock);
1395         } else {
1396                 shmem_swp_unmap(entry);
1397                 sbinfo = SHMEM_SB(inode->i_sb);
1398                 if (sbinfo->max_blocks) {
1399                         spin_lock(&sbinfo->stat_lock);
1400                         if (sbinfo->free_blocks == 0 ||
1401                             shmem_acct_block(info->flags)) {
1402                                 spin_unlock(&sbinfo->stat_lock);
1403                                 spin_unlock(&info->lock);
1404                                 error = -ENOSPC;
1405                                 goto failed;
1406                         }
1407                         sbinfo->free_blocks--;
1408                         inode->i_blocks += BLOCKS_PER_PAGE;
1409                         spin_unlock(&sbinfo->stat_lock);
1410                 } else if (shmem_acct_block(info->flags)) {
1411                         spin_unlock(&info->lock);
1412                         error = -ENOSPC;
1413                         goto failed;
1414                 }
1415
1416                 if (!filepage) {
1417                         spin_unlock(&info->lock);
1418                         filepage = shmem_alloc_page(gfp, info, idx);
1419                         if (!filepage) {
1420                                 shmem_unacct_blocks(info->flags, 1);
1421                                 shmem_free_blocks(inode, 1);
1422                                 error = -ENOMEM;
1423                                 goto failed;
1424                         }
1425
1426                         /* Precharge page while we can wait, compensate after */
1427                         error = mem_cgroup_cache_charge(filepage, current->mm,
1428                                                         gfp & ~__GFP_HIGHMEM);
1429                         if (error) {
1430                                 page_cache_release(filepage);
1431                                 shmem_unacct_blocks(info->flags, 1);
1432                                 shmem_free_blocks(inode, 1);
1433                                 filepage = NULL;
1434                                 goto failed;
1435                         }
1436
1437                         spin_lock(&info->lock);
1438                         entry = shmem_swp_alloc(info, idx, sgp);
1439                         if (IS_ERR(entry))
1440                                 error = PTR_ERR(entry);
1441                         else {
1442                                 swap = *entry;
1443                                 shmem_swp_unmap(entry);
1444                         }
1445                         if (error || swap.val || 0 != add_to_page_cache_lru(
1446                                         filepage, mapping, idx, GFP_NOWAIT)) {
1447                                 spin_unlock(&info->lock);
1448                                 mem_cgroup_uncharge_page(filepage);
1449                                 page_cache_release(filepage);
1450                                 shmem_unacct_blocks(info->flags, 1);
1451                                 shmem_free_blocks(inode, 1);
1452                                 filepage = NULL;
1453                                 if (error)
1454                                         goto failed;
1455                                 goto repeat;
1456                         }
1457                         mem_cgroup_uncharge_page(filepage);
1458                         info->flags |= SHMEM_PAGEIN;
1459                 }
1460
1461                 info->alloced++;
1462                 spin_unlock(&info->lock);
1463                 clear_highpage(filepage);
1464                 flush_dcache_page(filepage);
1465                 SetPageUptodate(filepage);
1466                 if (sgp == SGP_DIRTY)
1467                         set_page_dirty(filepage);
1468         }
1469 done:
1470         *pagep = filepage;
1471         return 0;
1472
1473 failed:
1474         if (*pagep != filepage) {
1475                 unlock_page(filepage);
1476                 page_cache_release(filepage);
1477         }
1478         return error;
1479 }
1480
1481 static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1482 {
1483         struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1484         int error;
1485         int ret;
1486
1487         if (((loff_t)vmf->pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
1488                 return VM_FAULT_SIGBUS;
1489
1490         error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret);
1491         if (error)
1492                 return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1493
1494         mark_page_accessed(vmf->page);
1495         return ret | VM_FAULT_LOCKED;
1496 }
1497
1498 #ifdef CONFIG_NUMA
1499 static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *new)
1500 {
1501         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1502         return mpol_set_shared_policy(&SHMEM_I(i)->policy, vma, new);
1503 }
1504
1505 static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
1506                                           unsigned long addr)
1507 {
1508         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1509         unsigned long idx;
1510
1511         idx = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1512         return mpol_shared_policy_lookup(&SHMEM_I(i)->policy, idx);
1513 }
1514 #endif
1515
1516 int shmem_lock(struct file *file, int lock, struct user_struct *user)
1517 {
1518         struct inode *inode = file->f_path.dentry->d_inode;
1519         struct shmem_inode_info *info = SHMEM_I(inode);
1520         int retval = -ENOMEM;
1521
1522         spin_lock(&info->lock);
1523         if (lock && !(info->flags & VM_LOCKED)) {
1524                 if (!user_shm_lock(inode->i_size, user))
1525                         goto out_nomem;
1526                 info->flags |= VM_LOCKED;
1527         }
1528         if (!lock && (info->flags & VM_LOCKED) && user) {
1529                 user_shm_unlock(inode->i_size, user);
1530                 info->flags &= ~VM_LOCKED;
1531         }
1532         retval = 0;
1533 out_nomem:
1534         spin_unlock(&info->lock);
1535         return retval;
1536 }
1537
1538 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1539 {
1540         file_accessed(file);
1541         vma->vm_ops = &shmem_vm_ops;
1542         vma->vm_flags |= VM_CAN_NONLINEAR;
1543         return 0;
1544 }
1545
1546 static struct inode *
1547 shmem_get_inode(struct super_block *sb, int mode, dev_t dev)
1548 {
1549         struct inode *inode;
1550         struct shmem_inode_info *info;
1551         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1552
1553         if (shmem_reserve_inode(sb))
1554                 return NULL;
1555
1556         inode = new_inode(sb);
1557         if (inode) {
1558                 inode->i_mode = mode;
1559                 inode->i_uid = current->fsuid;
1560                 inode->i_gid = current->fsgid;
1561                 inode->i_blocks = 0;
1562                 inode->i_mapping->a_ops = &shmem_aops;
1563                 inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1564                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1565                 inode->i_generation = get_seconds();
1566                 info = SHMEM_I(inode);
1567                 memset(info, 0, (char *)inode - (char *)info);
1568                 spin_lock_init(&info->lock);
1569                 INIT_LIST_HEAD(&info->swaplist);
1570
1571                 switch (mode & S_IFMT) {
1572                 default:
1573                         inode->i_op = &shmem_special_inode_operations;
1574                         init_special_inode(inode, mode, dev);
1575                         break;
1576                 case S_IFREG:
1577                         inode->i_op = &shmem_inode_operations;
1578                         inode->i_fop = &shmem_file_operations;
1579                         mpol_shared_policy_init(&info->policy, sbinfo->policy,
1580                                                         &sbinfo->policy_nodes);
1581                         break;
1582                 case S_IFDIR:
1583                         inc_nlink(inode);
1584                         /* Some things misbehave if size == 0 on a directory */
1585                         inode->i_size = 2 * BOGO_DIRENT_SIZE;
1586                         inode->i_op = &shmem_dir_inode_operations;
1587                         inode->i_fop = &simple_dir_operations;
1588                         break;
1589                 case S_IFLNK:
1590                         /*
1591                          * Must not load anything in the rbtree,
1592                          * mpol_free_shared_policy will not be called.
1593                          */
1594                         mpol_shared_policy_init(&info->policy, MPOL_DEFAULT,
1595                                                 NULL);
1596                         break;
1597                 }
1598         } else
1599                 shmem_free_inode(sb);
1600         return inode;
1601 }
1602
1603 #ifdef CONFIG_TMPFS
1604 static const struct inode_operations shmem_symlink_inode_operations;
1605 static const struct inode_operations shmem_symlink_inline_operations;
1606
1607 /*
1608  * Normally tmpfs avoids the use of shmem_readpage and shmem_write_begin;
1609  * but providing them allows a tmpfs file to be used for splice, sendfile, and
1610  * below the loop driver, in the generic fashion that many filesystems support.
1611  */
1612 static int shmem_readpage(struct file *file, struct page *page)
1613 {
1614         struct inode *inode = page->mapping->host;
1615         int error = shmem_getpage(inode, page->index, &page, SGP_CACHE, NULL);
1616         unlock_page(page);
1617         return error;
1618 }
1619
1620 static int
1621 shmem_write_begin(struct file *file, struct address_space *mapping,
1622                         loff_t pos, unsigned len, unsigned flags,
1623                         struct page **pagep, void **fsdata)
1624 {
1625         struct inode *inode = mapping->host;
1626         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1627         *pagep = NULL;
1628         return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
1629 }
1630
1631 static int
1632 shmem_write_end(struct file *file, struct address_space *mapping,
1633                         loff_t pos, unsigned len, unsigned copied,
1634                         struct page *page, void *fsdata)
1635 {
1636         struct inode *inode = mapping->host;
1637
1638         if (pos + copied > inode->i_size)
1639                 i_size_write(inode, pos + copied);
1640
1641         unlock_page(page);
1642         set_page_dirty(page);
1643         page_cache_release(page);
1644
1645         return copied;
1646 }
1647
1648 static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
1649 {
1650         struct inode *inode = filp->f_path.dentry->d_inode;
1651         struct address_space *mapping = inode->i_mapping;
1652         unsigned long index, offset;
1653         enum sgp_type sgp = SGP_READ;
1654
1655         /*
1656          * Might this read be for a stacking filesystem?  Then when reading
1657          * holes of a sparse file, we actually need to allocate those pages,
1658          * and even mark them dirty, so it cannot exceed the max_blocks limit.
1659          */
1660         if (segment_eq(get_fs(), KERNEL_DS))
1661                 sgp = SGP_DIRTY;
1662
1663         index = *ppos >> PAGE_CACHE_SHIFT;
1664         offset = *ppos & ~PAGE_CACHE_MASK;
1665
1666         for (;;) {
1667                 struct page *page = NULL;
1668                 unsigned long end_index, nr, ret;
1669                 loff_t i_size = i_size_read(inode);
1670
1671                 end_index = i_size >> PAGE_CACHE_SHIFT;
1672                 if (index > end_index)
1673                         break;
1674                 if (index == end_index) {
1675                         nr = i_size & ~PAGE_CACHE_MASK;
1676                         if (nr <= offset)
1677                                 break;
1678                 }
1679
1680                 desc->error = shmem_getpage(inode, index, &page, sgp, NULL);
1681                 if (desc->error) {
1682                         if (desc->error == -EINVAL)
1683                                 desc->error = 0;
1684                         break;
1685                 }
1686                 if (page)
1687                         unlock_page(page);
1688
1689                 /*
1690                  * We must evaluate after, since reads (unlike writes)
1691                  * are called without i_mutex protection against truncate
1692                  */
1693                 nr = PAGE_CACHE_SIZE;
1694                 i_size = i_size_read(inode);
1695                 end_index = i_size >> PAGE_CACHE_SHIFT;
1696                 if (index == end_index) {
1697                         nr = i_size & ~PAGE_CACHE_MASK;
1698                         if (nr <= offset) {
1699                                 if (page)
1700                                         page_cache_release(page);
1701                                 break;
1702                         }
1703                 }
1704                 nr -= offset;
1705
1706                 if (page) {
1707                         /*
1708                          * If users can be writing to this page using arbitrary
1709                          * virtual addresses, take care about potential aliasing
1710                          * before reading the page on the kernel side.
1711                          */
1712                         if (mapping_writably_mapped(mapping))
1713                                 flush_dcache_page(page);
1714                         /*
1715                          * Mark the page accessed if we read the beginning.
1716                          */
1717                         if (!offset)
1718                                 mark_page_accessed(page);
1719                 } else {
1720                         page = ZERO_PAGE(0);
1721                         page_cache_get(page);
1722                 }
1723
1724                 /*
1725                  * Ok, we have the page, and it's up-to-date, so
1726                  * now we can copy it to user space...
1727                  *
1728                  * The actor routine returns how many bytes were actually used..
1729                  * NOTE! This may not be the same as how much of a user buffer
1730                  * we filled up (we may be padding etc), so we can only update
1731                  * "pos" here (the actor routine has to update the user buffer
1732                  * pointers and the remaining count).
1733                  */
1734                 ret = actor(desc, page, offset, nr);
1735                 offset += ret;
1736                 index += offset >> PAGE_CACHE_SHIFT;
1737                 offset &= ~PAGE_CACHE_MASK;
1738
1739                 page_cache_release(page);
1740                 if (ret != nr || !desc->count)
1741                         break;
1742
1743                 cond_resched();
1744         }
1745
1746         *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1747         file_accessed(filp);
1748 }
1749
1750 static ssize_t shmem_file_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
1751 {
1752         read_descriptor_t desc;
1753
1754         if ((ssize_t) count < 0)
1755                 return -EINVAL;
1756         if (!access_ok(VERIFY_WRITE, buf, count))
1757                 return -EFAULT;
1758         if (!count)
1759                 return 0;
1760
1761         desc.written = 0;
1762         desc.count = count;
1763         desc.arg.buf = buf;
1764         desc.error = 0;
1765
1766         do_shmem_file_read(filp, ppos, &desc, file_read_actor);
1767         if (desc.written)
1768                 return desc.written;
1769         return desc.error;
1770 }
1771
1772 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
1773 {
1774         struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
1775
1776         buf->f_type = TMPFS_MAGIC;
1777         buf->f_bsize = PAGE_CACHE_SIZE;
1778         buf->f_namelen = NAME_MAX;
1779         spin_lock(&sbinfo->stat_lock);
1780         if (sbinfo->max_blocks) {
1781                 buf->f_blocks = sbinfo->max_blocks;
1782                 buf->f_bavail = buf->f_bfree = sbinfo->free_blocks;
1783         }
1784         if (sbinfo->max_inodes) {
1785                 buf->f_files = sbinfo->max_inodes;
1786                 buf->f_ffree = sbinfo->free_inodes;
1787         }
1788         /* else leave those fields 0 like simple_statfs */
1789         spin_unlock(&sbinfo->stat_lock);
1790         return 0;
1791 }
1792
1793 /*
1794  * File creation. Allocate an inode, and we're done..
1795  */
1796 static int
1797 shmem_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
1798 {
1799         struct inode *inode = shmem_get_inode(dir->i_sb, mode, dev);
1800         int error = -ENOSPC;
1801
1802         if (inode) {
1803                 error = security_inode_init_security(inode, dir, NULL, NULL,
1804                                                      NULL);
1805                 if (error) {
1806                         if (error != -EOPNOTSUPP) {
1807                                 iput(inode);
1808                                 return error;
1809                         }
1810                 }
1811                 error = shmem_acl_init(inode, dir);
1812                 if (error) {
1813                         iput(inode);
1814                         return error;
1815                 }
1816                 if (dir->i_mode & S_ISGID) {
1817                         inode->i_gid = dir->i_gid;
1818                         if (S_ISDIR(mode))
1819                                 inode->i_mode |= S_ISGID;
1820                 }
1821                 dir->i_size += BOGO_DIRENT_SIZE;
1822                 dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1823                 d_instantiate(dentry, inode);
1824                 dget(dentry); /* Extra count - pin the dentry in core */
1825         }
1826         return error;
1827 }
1828
1829 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, int mode)
1830 {
1831         int error;
1832
1833         if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
1834                 return error;
1835         inc_nlink(dir);
1836         return 0;
1837 }
1838
1839 static int shmem_create(struct inode *dir, struct dentry *dentry, int mode,
1840                 struct nameidata *nd)
1841 {
1842         return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
1843 }
1844
1845 /*
1846  * Link a file..
1847  */
1848 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
1849 {
1850         struct inode *inode = old_dentry->d_inode;
1851         int ret;
1852
1853         /*
1854          * No ordinary (disk based) filesystem counts links as inodes;
1855          * but each new link needs a new dentry, pinning lowmem, and
1856          * tmpfs dentries cannot be pruned until they are unlinked.
1857          */
1858         ret = shmem_reserve_inode(inode->i_sb);
1859         if (ret)
1860                 goto out;
1861
1862         dir->i_size += BOGO_DIRENT_SIZE;
1863         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1864         inc_nlink(inode);
1865         atomic_inc(&inode->i_count);    /* New dentry reference */
1866         dget(dentry);           /* Extra pinning count for the created dentry */
1867         d_instantiate(dentry, inode);
1868 out:
1869         return ret;
1870 }
1871
1872 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
1873 {
1874         struct inode *inode = dentry->d_inode;
1875
1876         if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
1877                 shmem_free_inode(inode->i_sb);
1878
1879         dir->i_size -= BOGO_DIRENT_SIZE;
1880         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1881         drop_nlink(inode);
1882         dput(dentry);   /* Undo the count from "create" - this does all the work */
1883         return 0;
1884 }
1885
1886 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
1887 {
1888         if (!simple_empty(dentry))
1889                 return -ENOTEMPTY;
1890
1891         drop_nlink(dentry->d_inode);
1892         drop_nlink(dir);
1893         return shmem_unlink(dir, dentry);
1894 }
1895
1896 /*
1897  * The VFS layer already does all the dentry stuff for rename,
1898  * we just have to decrement the usage count for the target if
1899  * it exists so that the VFS layer correctly free's it when it
1900  * gets overwritten.
1901  */
1902 static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
1903 {
1904         struct inode *inode = old_dentry->d_inode;
1905         int they_are_dirs = S_ISDIR(inode->i_mode);
1906
1907         if (!simple_empty(new_dentry))
1908                 return -ENOTEMPTY;
1909
1910         if (new_dentry->d_inode) {
1911                 (void) shmem_unlink(new_dir, new_dentry);
1912                 if (they_are_dirs)
1913                         drop_nlink(old_dir);
1914         } else if (they_are_dirs) {
1915                 drop_nlink(old_dir);
1916                 inc_nlink(new_dir);
1917         }
1918
1919         old_dir->i_size -= BOGO_DIRENT_SIZE;
1920         new_dir->i_size += BOGO_DIRENT_SIZE;
1921         old_dir->i_ctime = old_dir->i_mtime =
1922         new_dir->i_ctime = new_dir->i_mtime =
1923         inode->i_ctime = CURRENT_TIME;
1924         return 0;
1925 }
1926
1927 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
1928 {
1929         int error;
1930         int len;
1931         struct inode *inode;
1932         struct page *page = NULL;
1933         char *kaddr;
1934         struct shmem_inode_info *info;
1935
1936         len = strlen(symname) + 1;
1937         if (len > PAGE_CACHE_SIZE)
1938                 return -ENAMETOOLONG;
1939
1940         inode = shmem_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0);
1941         if (!inode)
1942                 return -ENOSPC;
1943
1944         error = security_inode_init_security(inode, dir, NULL, NULL,
1945                                              NULL);
1946         if (error) {
1947                 if (error != -EOPNOTSUPP) {
1948                         iput(inode);
1949                         return error;
1950                 }
1951                 error = 0;
1952         }
1953
1954         info = SHMEM_I(inode);
1955         inode->i_size = len-1;
1956         if (len <= (char *)inode - (char *)info) {
1957                 /* do it inline */
1958                 memcpy(info, symname, len);
1959                 inode->i_op = &shmem_symlink_inline_operations;
1960         } else {
1961                 error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
1962                 if (error) {
1963                         iput(inode);
1964                         return error;
1965                 }
1966                 unlock_page(page);
1967                 inode->i_op = &shmem_symlink_inode_operations;
1968                 kaddr = kmap_atomic(page, KM_USER0);
1969                 memcpy(kaddr, symname, len);
1970                 kunmap_atomic(kaddr, KM_USER0);
1971                 set_page_dirty(page);
1972                 page_cache_release(page);
1973         }
1974         if (dir->i_mode & S_ISGID)
1975                 inode->i_gid = dir->i_gid;
1976         dir->i_size += BOGO_DIRENT_SIZE;
1977         dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1978         d_instantiate(dentry, inode);
1979         dget(dentry);
1980         return 0;
1981 }
1982
1983 static void *shmem_follow_link_inline(struct dentry *dentry, struct nameidata *nd)
1984 {
1985         nd_set_link(nd, (char *)SHMEM_I(dentry->d_inode));
1986         return NULL;
1987 }
1988
1989 static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
1990 {
1991         struct page *page = NULL;
1992         int res = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
1993         nd_set_link(nd, res ? ERR_PTR(res) : kmap(page));
1994         if (page)
1995                 unlock_page(page);
1996         return page;
1997 }
1998
1999 static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
2000 {
2001         if (!IS_ERR(nd_get_link(nd))) {
2002                 struct page *page = cookie;
2003                 kunmap(page);
2004                 mark_page_accessed(page);
2005                 page_cache_release(page);
2006         }
2007 }
2008
2009 static const struct inode_operations shmem_symlink_inline_operations = {
2010         .readlink       = generic_readlink,
2011         .follow_link    = shmem_follow_link_inline,
2012 };
2013
2014 static const struct inode_operations shmem_symlink_inode_operations = {
2015         .truncate       = shmem_truncate,
2016         .readlink       = generic_readlink,
2017         .follow_link    = shmem_follow_link,
2018         .put_link       = shmem_put_link,
2019 };
2020
2021 #ifdef CONFIG_TMPFS_POSIX_ACL
2022 /*
2023  * Superblocks without xattr inode operations will get security.* xattr
2024  * support from the VFS "for free". As soon as we have any other xattrs
2025  * like ACLs, we also need to implement the security.* handlers at
2026  * filesystem level, though.
2027  */
2028
2029 static size_t shmem_xattr_security_list(struct inode *inode, char *list,
2030                                         size_t list_len, const char *name,
2031                                         size_t name_len)
2032 {
2033         return security_inode_listsecurity(inode, list, list_len);
2034 }
2035
2036 static int shmem_xattr_security_get(struct inode *inode, const char *name,
2037                                     void *buffer, size_t size)
2038 {
2039         if (strcmp(name, "") == 0)
2040                 return -EINVAL;
2041         return xattr_getsecurity(inode, name, buffer, size);
2042 }
2043
2044 static int shmem_xattr_security_set(struct inode *inode, const char *name,
2045                                     const void *value, size_t size, int flags)
2046 {
2047         if (strcmp(name, "") == 0)
2048                 return -EINVAL;
2049         return security_inode_setsecurity(inode, name, value, size, flags);
2050 }
2051
2052 static struct xattr_handler shmem_xattr_security_handler = {
2053         .prefix = XATTR_SECURITY_PREFIX,
2054         .list   = shmem_xattr_security_list,
2055         .get    = shmem_xattr_security_get,
2056         .set    = shmem_xattr_security_set,
2057 };
2058
2059 static struct xattr_handler *shmem_xattr_handlers[] = {
2060         &shmem_xattr_acl_access_handler,
2061         &shmem_xattr_acl_default_handler,
2062         &shmem_xattr_security_handler,
2063         NULL
2064 };
2065 #endif
2066
2067 static struct dentry *shmem_get_parent(struct dentry *child)
2068 {
2069         return ERR_PTR(-ESTALE);
2070 }
2071
2072 static int shmem_match(struct inode *ino, void *vfh)
2073 {
2074         __u32 *fh = vfh;
2075         __u64 inum = fh[2];
2076         inum = (inum << 32) | fh[1];
2077         return ino->i_ino == inum && fh[0] == ino->i_generation;
2078 }
2079
2080 static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
2081                 struct fid *fid, int fh_len, int fh_type)
2082 {
2083         struct inode *inode;
2084         struct dentry *dentry = NULL;
2085         u64 inum = fid->raw[2];
2086         inum = (inum << 32) | fid->raw[1];
2087
2088         if (fh_len < 3)
2089                 return NULL;
2090
2091         inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
2092                         shmem_match, fid->raw);
2093         if (inode) {
2094                 dentry = d_find_alias(inode);
2095                 iput(inode);
2096         }
2097
2098         return dentry;
2099 }
2100
2101 static int shmem_encode_fh(struct dentry *dentry, __u32 *fh, int *len,
2102                                 int connectable)
2103 {
2104         struct inode *inode = dentry->d_inode;
2105
2106         if (*len < 3)
2107                 return 255;
2108
2109         if (hlist_unhashed(&inode->i_hash)) {
2110                 /* Unfortunately insert_inode_hash is not idempotent,
2111                  * so as we hash inodes here rather than at creation
2112                  * time, we need a lock to ensure we only try
2113                  * to do it once
2114                  */
2115                 static DEFINE_SPINLOCK(lock);
2116                 spin_lock(&lock);
2117                 if (hlist_unhashed(&inode->i_hash))
2118                         __insert_inode_hash(inode,
2119                                             inode->i_ino + inode->i_generation);
2120                 spin_unlock(&lock);
2121         }
2122
2123         fh[0] = inode->i_generation;
2124         fh[1] = inode->i_ino;
2125         fh[2] = ((__u64)inode->i_ino) >> 32;
2126
2127         *len = 3;
2128         return 1;
2129 }
2130
2131 static const struct export_operations shmem_export_ops = {
2132         .get_parent     = shmem_get_parent,
2133         .encode_fh      = shmem_encode_fh,
2134         .fh_to_dentry   = shmem_fh_to_dentry,
2135 };
2136
2137 static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
2138                                bool remount)
2139 {
2140         char *this_char, *value, *rest;
2141
2142         while (options != NULL) {
2143                 this_char = options;
2144                 for (;;) {
2145                         /*
2146                          * NUL-terminate this option: unfortunately,
2147                          * mount options form a comma-separated list,
2148                          * but mpol's nodelist may also contain commas.
2149                          */
2150                         options = strchr(options, ',');
2151                         if (options == NULL)
2152                                 break;
2153                         options++;
2154                         if (!isdigit(*options)) {
2155                                 options[-1] = '\0';
2156                                 break;
2157                         }
2158                 }
2159                 if (!*this_char)
2160                         continue;
2161                 if ((value = strchr(this_char,'=')) != NULL) {
2162                         *value++ = 0;
2163                 } else {
2164                         printk(KERN_ERR
2165                             "tmpfs: No value for mount option '%s'\n",
2166                             this_char);
2167                         return 1;
2168                 }
2169
2170                 if (!strcmp(this_char,"size")) {
2171                         unsigned long long size;
2172                         size = memparse(value,&rest);
2173                         if (*rest == '%') {
2174                                 size <<= PAGE_SHIFT;
2175                                 size *= totalram_pages;
2176                                 do_div(size, 100);
2177                                 rest++;
2178                         }
2179                         if (*rest)
2180                                 goto bad_val;
2181                         sbinfo->max_blocks =
2182                                 DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
2183                 } else if (!strcmp(this_char,"nr_blocks")) {
2184                         sbinfo->max_blocks = memparse(value, &rest);
2185                         if (*rest)
2186                                 goto bad_val;
2187                 } else if (!strcmp(this_char,"nr_inodes")) {
2188                         sbinfo->max_inodes = memparse(value, &rest);
2189                         if (*rest)
2190                                 goto bad_val;
2191                 } else if (!strcmp(this_char,"mode")) {
2192                         if (remount)
2193                                 continue;
2194                         sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
2195                         if (*rest)
2196                                 goto bad_val;
2197                 } else if (!strcmp(this_char,"uid")) {
2198                         if (remount)
2199                                 continue;
2200                         sbinfo->uid = simple_strtoul(value, &rest, 0);
2201                         if (*rest)
2202                                 goto bad_val;
2203                 } else if (!strcmp(this_char,"gid")) {
2204                         if (remount)
2205                                 continue;
2206                         sbinfo->gid = simple_strtoul(value, &rest, 0);
2207                         if (*rest)
2208                                 goto bad_val;
2209                 } else if (!strcmp(this_char,"mpol")) {
2210                         if (shmem_parse_mpol(value, &sbinfo->policy,
2211                                              &sbinfo->policy_nodes))
2212                                 goto bad_val;
2213                 } else {
2214                         printk(KERN_ERR "tmpfs: Bad mount option %s\n",
2215                                this_char);
2216                         return 1;
2217                 }
2218         }
2219         return 0;
2220
2221 bad_val:
2222         printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
2223                value, this_char);
2224         return 1;
2225
2226 }
2227
2228 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2229 {
2230         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2231         struct shmem_sb_info config = *sbinfo;
2232         unsigned long blocks;
2233         unsigned long inodes;
2234         int error = -EINVAL;
2235
2236         if (shmem_parse_options(data, &config, true))
2237                 return error;
2238
2239         spin_lock(&sbinfo->stat_lock);
2240         blocks = sbinfo->max_blocks - sbinfo->free_blocks;
2241         inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2242         if (config.max_blocks < blocks)
2243                 goto out;
2244         if (config.max_inodes < inodes)
2245                 goto out;
2246         /*
2247          * Those tests also disallow limited->unlimited while any are in
2248          * use, so i_blocks will always be zero when max_blocks is zero;
2249          * but we must separately disallow unlimited->limited, because
2250          * in that case we have no record of how much is already in use.
2251          */
2252         if (config.max_blocks && !sbinfo->max_blocks)
2253                 goto out;
2254         if (config.max_inodes && !sbinfo->max_inodes)
2255                 goto out;
2256
2257         error = 0;
2258         sbinfo->max_blocks  = config.max_blocks;
2259         sbinfo->free_blocks = config.max_blocks - blocks;
2260         sbinfo->max_inodes  = config.max_inodes;
2261         sbinfo->free_inodes = config.max_inodes - inodes;
2262         sbinfo->policy      = config.policy;
2263         sbinfo->policy_nodes = config.policy_nodes;
2264 out:
2265         spin_unlock(&sbinfo->stat_lock);
2266         return error;
2267 }
2268
2269 static int shmem_show_options(struct seq_file *seq, struct vfsmount *vfs)
2270 {
2271         struct shmem_sb_info *sbinfo = SHMEM_SB(vfs->mnt_sb);
2272
2273         if (sbinfo->max_blocks != shmem_default_max_blocks())
2274                 seq_printf(seq, ",size=%luk",
2275                         sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10));
2276         if (sbinfo->max_inodes != shmem_default_max_inodes())
2277                 seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
2278         if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
2279                 seq_printf(seq, ",mode=%03o", sbinfo->mode);
2280         if (sbinfo->uid != 0)
2281                 seq_printf(seq, ",uid=%u", sbinfo->uid);
2282         if (sbinfo->gid != 0)
2283                 seq_printf(seq, ",gid=%u", sbinfo->gid);
2284         shmem_show_mpol(seq, sbinfo->policy, sbinfo->policy_nodes);
2285         return 0;
2286 }
2287 #endif /* CONFIG_TMPFS */
2288
2289 static void shmem_put_super(struct super_block *sb)
2290 {
2291         kfree(sb->s_fs_info);
2292         sb->s_fs_info = NULL;
2293 }
2294
2295 static int shmem_fill_super(struct super_block *sb,
2296                             void *data, int silent)
2297 {
2298         struct inode *inode;
2299         struct dentry *root;
2300         struct shmem_sb_info *sbinfo;
2301         int err = -ENOMEM;
2302
2303         /* Round up to L1_CACHE_BYTES to resist false sharing */
2304         sbinfo = kmalloc(max((int)sizeof(struct shmem_sb_info),
2305                                 L1_CACHE_BYTES), GFP_KERNEL);
2306         if (!sbinfo)
2307                 return -ENOMEM;
2308
2309         sbinfo->max_blocks = 0;
2310         sbinfo->max_inodes = 0;
2311         sbinfo->mode = S_IRWXUGO | S_ISVTX;
2312         sbinfo->uid = current->fsuid;
2313         sbinfo->gid = current->fsgid;
2314         sbinfo->policy = MPOL_DEFAULT;
2315         sbinfo->policy_nodes = node_states[N_HIGH_MEMORY];
2316         sb->s_fs_info = sbinfo;
2317
2318 #ifdef CONFIG_TMPFS
2319         /*
2320          * Per default we only allow half of the physical ram per
2321          * tmpfs instance, limiting inodes to one per page of lowmem;
2322          * but the internal instance is left unlimited.
2323          */
2324         if (!(sb->s_flags & MS_NOUSER)) {
2325                 sbinfo->max_blocks = shmem_default_max_blocks();
2326                 sbinfo->max_inodes = shmem_default_max_inodes();
2327                 if (shmem_parse_options(data, sbinfo, false)) {
2328                         err = -EINVAL;
2329                         goto failed;
2330                 }
2331         }
2332         sb->s_export_op = &shmem_export_ops;
2333 #else
2334         sb->s_flags |= MS_NOUSER;
2335 #endif
2336
2337         spin_lock_init(&sbinfo->stat_lock);
2338         sbinfo->free_blocks = sbinfo->max_blocks;
2339         sbinfo->free_inodes = sbinfo->max_inodes;
2340
2341         sb->s_maxbytes = SHMEM_MAX_BYTES;
2342         sb->s_blocksize = PAGE_CACHE_SIZE;
2343         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
2344         sb->s_magic = TMPFS_MAGIC;
2345         sb->s_op = &shmem_ops;
2346         sb->s_time_gran = 1;
2347 #ifdef CONFIG_TMPFS_POSIX_ACL
2348         sb->s_xattr = shmem_xattr_handlers;
2349         sb->s_flags |= MS_POSIXACL;
2350 #endif
2351
2352         inode = shmem_get_inode(sb, S_IFDIR | sbinfo->mode, 0);
2353         if (!inode)
2354                 goto failed;
2355         inode->i_uid = sbinfo->uid;
2356         inode->i_gid = sbinfo->gid;
2357         root = d_alloc_root(inode);
2358         if (!root)
2359                 goto failed_iput;
2360         sb->s_root = root;
2361         return 0;
2362
2363 failed_iput:
2364         iput(inode);
2365 failed:
2366         shmem_put_super(sb);
2367         return err;
2368 }
2369
2370 static struct kmem_cache *shmem_inode_cachep;
2371
2372 static struct inode *shmem_alloc_inode(struct super_block *sb)
2373 {
2374         struct shmem_inode_info *p;
2375         p = (struct shmem_inode_info *)kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
2376         if (!p)
2377                 return NULL;
2378         return &p->vfs_inode;
2379 }
2380
2381 static void shmem_destroy_inode(struct inode *inode)
2382 {
2383         if ((inode->i_mode & S_IFMT) == S_IFREG) {
2384                 /* only struct inode is valid if it's an inline symlink */
2385                 mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2386         }
2387         shmem_acl_destroy_inode(inode);
2388         kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2389 }
2390
2391 static void init_once(struct kmem_cache *cachep, void *foo)
2392 {
2393         struct shmem_inode_info *p = (struct shmem_inode_info *) foo;
2394
2395         inode_init_once(&p->vfs_inode);
2396 #ifdef CONFIG_TMPFS_POSIX_ACL
2397         p->i_acl = NULL;
2398         p->i_default_acl = NULL;
2399 #endif
2400 }
2401
2402 static int init_inodecache(void)
2403 {
2404         shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
2405                                 sizeof(struct shmem_inode_info),
2406                                 0, SLAB_PANIC, init_once);
2407         return 0;
2408 }
2409
2410 static void destroy_inodecache(void)
2411 {
2412         kmem_cache_destroy(shmem_inode_cachep);
2413 }
2414
2415 static const struct address_space_operations shmem_aops = {
2416         .writepage      = shmem_writepage,
2417         .set_page_dirty = __set_page_dirty_no_writeback,
2418 #ifdef CONFIG_TMPFS
2419         .readpage       = shmem_readpage,
2420         .write_begin    = shmem_write_begin,
2421         .write_end      = shmem_write_end,
2422 #endif
2423         .migratepage    = migrate_page,
2424 };
2425
2426 static const struct file_operations shmem_file_operations = {
2427         .mmap           = shmem_mmap,
2428 #ifdef CONFIG_TMPFS
2429         .llseek         = generic_file_llseek,
2430         .read           = shmem_file_read,
2431         .write          = do_sync_write,
2432         .aio_write      = generic_file_aio_write,
2433         .fsync          = simple_sync_file,
2434         .splice_read    = generic_file_splice_read,
2435         .splice_write   = generic_file_splice_write,
2436 #endif
2437 };
2438
2439 static const struct inode_operations shmem_inode_operations = {
2440         .truncate       = shmem_truncate,
2441         .setattr        = shmem_notify_change,
2442         .truncate_range = shmem_truncate_range,
2443 #ifdef CONFIG_TMPFS_POSIX_ACL
2444         .setxattr       = generic_setxattr,
2445         .getxattr       = generic_getxattr,
2446         .listxattr      = generic_listxattr,
2447         .removexattr    = generic_removexattr,
2448         .permission     = shmem_permission,
2449 #endif
2450
2451 };
2452
2453 static const struct inode_operations shmem_dir_inode_operations = {
2454 #ifdef CONFIG_TMPFS
2455         .create         = shmem_create,
2456         .lookup         = simple_lookup,
2457         .link           = shmem_link,
2458         .unlink         = shmem_unlink,
2459         .symlink        = shmem_symlink,
2460         .mkdir          = shmem_mkdir,
2461         .rmdir          = shmem_rmdir,
2462         .mknod          = shmem_mknod,
2463         .rename         = shmem_rename,
2464 #endif
2465 #ifdef CONFIG_TMPFS_POSIX_ACL
2466         .setattr        = shmem_notify_change,
2467         .setxattr       = generic_setxattr,
2468         .getxattr       = generic_getxattr,
2469         .listxattr      = generic_listxattr,
2470         .removexattr    = generic_removexattr,
2471         .permission     = shmem_permission,
2472 #endif
2473 };
2474
2475 static const struct inode_operations shmem_special_inode_operations = {
2476 #ifdef CONFIG_TMPFS_POSIX_ACL
2477         .setattr        = shmem_notify_change,
2478         .setxattr       = generic_setxattr,
2479         .getxattr       = generic_getxattr,
2480         .listxattr      = generic_listxattr,
2481         .removexattr    = generic_removexattr,
2482         .permission     = shmem_permission,
2483 #endif
2484 };
2485
2486 static const struct super_operations shmem_ops = {
2487         .alloc_inode    = shmem_alloc_inode,
2488         .destroy_inode  = shmem_destroy_inode,
2489 #ifdef CONFIG_TMPFS
2490         .statfs         = shmem_statfs,
2491         .remount_fs     = shmem_remount_fs,
2492         .show_options   = shmem_show_options,
2493 #endif
2494         .delete_inode   = shmem_delete_inode,
2495         .drop_inode     = generic_delete_inode,
2496         .put_super      = shmem_put_super,
2497 };
2498
2499 static struct vm_operations_struct shmem_vm_ops = {
2500         .fault          = shmem_fault,
2501 #ifdef CONFIG_NUMA
2502         .set_policy     = shmem_set_policy,
2503         .get_policy     = shmem_get_policy,
2504 #endif
2505 };
2506
2507
2508 static int shmem_get_sb(struct file_system_type *fs_type,
2509         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
2510 {
2511         return get_sb_nodev(fs_type, flags, data, shmem_fill_super, mnt);
2512 }
2513
2514 static struct file_system_type tmpfs_fs_type = {
2515         .owner          = THIS_MODULE,
2516         .name           = "tmpfs",
2517         .get_sb         = shmem_get_sb,
2518         .kill_sb        = kill_litter_super,
2519 };
2520 static struct vfsmount *shm_mnt;
2521
2522 static int __init init_tmpfs(void)
2523 {
2524         int error;
2525
2526         error = bdi_init(&shmem_backing_dev_info);
2527         if (error)
2528                 goto out4;
2529
2530         error = init_inodecache();
2531         if (error)
2532                 goto out3;
2533
2534         error = register_filesystem(&tmpfs_fs_type);
2535         if (error) {
2536                 printk(KERN_ERR "Could not register tmpfs\n");
2537                 goto out2;
2538         }
2539
2540         shm_mnt = vfs_kern_mount(&tmpfs_fs_type, MS_NOUSER,
2541                                 tmpfs_fs_type.name, NULL);
2542         if (IS_ERR(shm_mnt)) {
2543                 error = PTR_ERR(shm_mnt);
2544                 printk(KERN_ERR "Could not kern_mount tmpfs\n");
2545                 goto out1;
2546         }
2547         return 0;
2548
2549 out1:
2550         unregister_filesystem(&tmpfs_fs_type);
2551 out2:
2552         destroy_inodecache();
2553 out3:
2554         bdi_destroy(&shmem_backing_dev_info);
2555 out4:
2556         shm_mnt = ERR_PTR(error);
2557         return error;
2558 }
2559 module_init(init_tmpfs)
2560
2561 /**
2562  * shmem_file_setup - get an unlinked file living in tmpfs
2563  * @name: name for dentry (to be seen in /proc/<pid>/maps
2564  * @size: size to be set for the file
2565  * @flags: vm_flags
2566  */
2567 struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags)
2568 {
2569         int error;
2570         struct file *file;
2571         struct inode *inode;
2572         struct dentry *dentry, *root;
2573         struct qstr this;
2574
2575         if (IS_ERR(shm_mnt))
2576                 return (void *)shm_mnt;
2577
2578         if (size < 0 || size > SHMEM_MAX_BYTES)
2579                 return ERR_PTR(-EINVAL);
2580
2581         if (shmem_acct_size(flags, size))
2582                 return ERR_PTR(-ENOMEM);
2583
2584         error = -ENOMEM;
2585         this.name = name;
2586         this.len = strlen(name);
2587         this.hash = 0; /* will go */
2588         root = shm_mnt->mnt_root;
2589         dentry = d_alloc(root, &this);
2590         if (!dentry)
2591                 goto put_memory;
2592
2593         error = -ENFILE;
2594         file = get_empty_filp();
2595         if (!file)
2596                 goto put_dentry;
2597
2598         error = -ENOSPC;
2599         inode = shmem_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0);
2600         if (!inode)
2601                 goto close_file;
2602
2603         SHMEM_I(inode)->flags = flags & VM_ACCOUNT;
2604         d_instantiate(dentry, inode);
2605         inode->i_size = size;
2606         inode->i_nlink = 0;     /* It is unlinked */
2607         init_file(file, shm_mnt, dentry, FMODE_WRITE | FMODE_READ,
2608                         &shmem_file_operations);
2609         return file;
2610
2611 close_file:
2612         put_filp(file);
2613 put_dentry:
2614         dput(dentry);
2615 put_memory:
2616         shmem_unacct_size(flags, size);
2617         return ERR_PTR(error);
2618 }
2619
2620 /**
2621  * shmem_zero_setup - setup a shared anonymous mapping
2622  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
2623  */
2624 int shmem_zero_setup(struct vm_area_struct *vma)
2625 {
2626         struct file *file;
2627         loff_t size = vma->vm_end - vma->vm_start;
2628
2629         file = shmem_file_setup("dev/zero", size, vma->vm_flags);
2630         if (IS_ERR(file))
2631                 return PTR_ERR(file);
2632
2633         if (vma->vm_file)
2634                 fput(vma->vm_file);
2635         vma->vm_file = file;
2636         vma->vm_ops = &shmem_vm_ops;
2637         return 0;
2638 }