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  * tiny-shmem:
  18  * Copyright (c) 2004, 2008 Matt Mackall <mpm@selenic.com>
  19  *
  20  * This file is released under the GPL.
  21  */
  22
  23 #include <linux/fs.h>
  24 #include <linux/init.h>
  25 #include <linux/vfs.h>
  26 #include <linux/mount.h>
  27 #include <linux/pagemap.h>
  28 #include <linux/file.h>
  29 #include <linux/mm.h>
  30 #include <linux/module.h>
  31 #include <linux/percpu_counter.h>
  32 #include <linux/swap.h>
  33
  34 static struct vfsmount *shm_mnt;
  35
  36 #ifdef CONFIG_SHMEM
  37 /*
  38  * This virtual memory filesystem is heavily based on the ramfs. It
  39  * extends ramfs by the ability to use swap and honor resource limits
  40  * which makes it a completely usable filesystem.
  41  */
  42
  43 #include <linux/xattr.h>
  44 #include <linux/exportfs.h>
  45 #include <linux/posix_acl.h>
  46 #include <linux/generic_acl.h>
  47 #include <linux/mman.h>
  48 #include <linux/string.h>
  49 #include <linux/slab.h>
  50 #include <linux/backing-dev.h>
  51 #include <linux/shmem_fs.h>
  52 #include <linux/writeback.h>
  53 #include <linux/blkdev.h>
  54 #include <linux/security.h>
  55 #include <linux/swapops.h>
  56 #include <linux/mempolicy.h>
  57 #include <linux/namei.h>
  58 #include <linux/ctype.h>
  59 #include <linux/migrate.h>
  60 #include <linux/highmem.h>
  61 #include <linux/seq_file.h>
  62 #include <linux/magic.h>
  63
  64 #include <asm/uaccess.h>
  65 #include <asm/div64.h>
  66 #include <asm/pgtable.h>
  67
  68 /*
  69  * The maximum size of a shmem/tmpfs file is limited by the maximum size of
  70  * its triple-indirect swap vector - see illustration at shmem_swp_entry().
  71  *
  72  * With 4kB page size, maximum file size is just over 2TB on a 32-bit kernel,
  73  * but one eighth of that on a 64-bit kernel.  With 8kB page size, maximum
  74  * file size is just over 4TB on a 64-bit kernel, but 16TB on a 32-bit kernel,
  75  * MAX_LFS_FILESIZE being then more restrictive than swap vector layout.
  76  *
  77  * We use / and * instead of shifts in the definitions below, so that the swap
  78  * vector can be tested with small even values (e.g. 20) for ENTRIES_PER_PAGE.
  79  */
  80 #define ENTRIES_PER_PAGE (PAGE_CACHE_SIZE/sizeof(unsigned long))
  81 #define ENTRIES_PER_PAGEPAGE ((unsigned long long)ENTRIES_PER_PAGE*ENTRIES_PER_PAGE)
  82
  83 #define SHMSWP_MAX_INDEX (SHMEM_NR_DIRECT + (ENTRIES_PER_PAGEPAGE/2) * (ENTRIES_PER_PAGE+1))
  84 #define SHMSWP_MAX_BYTES (SHMSWP_MAX_INDEX << PAGE_CACHE_SHIFT)
  85
  86 #define SHMEM_MAX_BYTES  min_t(unsigned long long, SHMSWP_MAX_BYTES, MAX_LFS_FILESIZE)
  87 #define SHMEM_MAX_INDEX  ((unsigned long)((SHMEM_MAX_BYTES+1) >> PAGE_CACHE_SHIFT))
  88
  89 #define BLOCKS_PER_PAGE  (PAGE_CACHE_SIZE/512)
  90 #define VM_ACCT(size)    (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
  91
  92 /* info->flags needs VM_flags to handle pagein/truncate races efficiently */
  93 #define SHMEM_PAGEIN     VM_READ
  94 #define SHMEM_TRUNCATE   VM_WRITE
  95
  96 /* Definition to limit shmem_truncate's steps between cond_rescheds */
  97 #define LATENCY_LIMIT    64
  98
  99 /* Pretend that each entry is of this size in directory's i_size */
 100 #define BOGO_DIRENT_SIZE 20
 101
 102 /* Flag allocation requirements to shmem_getpage and shmem_swp_alloc */
 103 enum sgp_type {
 104         SGP_READ,       /* don't exceed i_size, don't allocate page */
 105         SGP_CACHE,      /* don't exceed i_size, may allocate page */
 106         SGP_DIRTY,      /* like SGP_CACHE, but set new page dirty */
 107         SGP_WRITE,      /* may exceed i_size, may allocate page */
 108 };
 109
 110 #ifdef CONFIG_TMPFS
 111 static unsigned long shmem_default_max_blocks(void)
 112 {
 113         return totalram_pages / 2;
 114 }
 115
 116 static unsigned long shmem_default_max_inodes(void)
 117 {
 118         return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
 119 }
 120 #endif
 121
 122 static int shmem_getpage(struct inode *inode, unsigned long idx,
 123                          struct page **pagep, enum sgp_type sgp, int *type);
 124
 125 static inline struct page *shmem_dir_alloc(gfp_t gfp_mask)
 126 {
 127         /*
 128          * The above definition of ENTRIES_PER_PAGE, and the use of
 129          * BLOCKS_PER_PAGE on indirect pages, assume PAGE_CACHE_SIZE:
 130          * might be reconsidered if it ever diverges from PAGE_SIZE.
 131          *
 132          * Mobility flags are masked out as swap vectors cannot move
 133          */
 134         return alloc_pages((gfp_mask & ~GFP_MOVABLE_MASK) | __GFP_ZERO,
 135                                 PAGE_CACHE_SHIFT-PAGE_SHIFT);
 136 }
 137
 138 static inline void shmem_dir_free(struct page *page)
 139 {
 140         __free_pages(page, PAGE_CACHE_SHIFT-PAGE_SHIFT);
 141 }
 142
 143 static struct page **shmem_dir_map(struct page *page)
 144 {
 145         return (struct page **)kmap_atomic(page, KM_USER0);
 146 }
 147
 148 static inline void shmem_dir_unmap(struct page **dir)
 149 {
 150         kunmap_atomic(dir, KM_USER0);
 151 }
 152
 153 static swp_entry_t *shmem_swp_map(struct page *page)
 154 {
 155         return (swp_entry_t *)kmap_atomic(page, KM_USER1);
 156 }
 157
 158 static inline void shmem_swp_balance_unmap(void)
 159 {
 160         /*
 161          * When passing a pointer to an i_direct entry, to code which
 162          * also handles indirect entries and so will shmem_swp_unmap,
 163          * we must arrange for the preempt count to remain in balance.
 164          * What kmap_atomic of a lowmem page does depends on config
 165          * and architecture, so pretend to kmap_atomic some lowmem page.
 166          */
 167         (void) kmap_atomic(ZERO_PAGE(0), KM_USER1);
 168 }
 169
 170 static inline void shmem_swp_unmap(swp_entry_t *entry)
 171 {
 172         kunmap_atomic(entry, KM_USER1);
 173 }
 174
 175 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
 176 {
 177         return sb->s_fs_info;
 178 }
 179
 180 /*
 181  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
 182  * for shared memory and for shared anonymous (/dev/zero) mappings
 183  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
 184  * consistent with the pre-accounting of private mappings ...
 185  */
 186 static inline int shmem_acct_size(unsigned long flags, loff_t size)
 187 {
 188         return (flags & VM_NORESERVE) ?
 189                 0 : security_vm_enough_memory_kern(VM_ACCT(size));
 190 }
 191
 192 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
 193 {
 194         if (!(flags & VM_NORESERVE))
 195                 vm_unacct_memory(VM_ACCT(size));
 196 }
 197
 198 /*
 199  * ... whereas tmpfs objects are accounted incrementally as
 200  * pages are allocated, in order to allow huge sparse files.
 201  * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
 202  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
 203  */
 204 static inline int shmem_acct_block(unsigned long flags)
 205 {
 206         return (flags & VM_NORESERVE) ?
 207                 security_vm_enough_memory_kern(VM_ACCT(PAGE_CACHE_SIZE)) : 0;
 208 }
 209
 210 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
 211 {
 212         if (flags & VM_NORESERVE)
 213                 vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
 214 }
 215
 216 static const struct super_operations shmem_ops;
 217 static const struct address_space_operations shmem_aops;
 218 static const struct file_operations shmem_file_operations;
 219 static const struct inode_operations shmem_inode_operations;
 220 static const struct inode_operations shmem_dir_inode_operations;
 221 static const struct inode_operations shmem_special_inode_operations;
 222 static const struct vm_operations_struct shmem_vm_ops;
 223
 224 static struct backing_dev_info shmem_backing_dev_info  __read_mostly = {
 225         .ra_pages       = 0,    /* No readahead */
 226         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
 227 };
 228
 229 static LIST_HEAD(shmem_swaplist);
 230 static DEFINE_MUTEX(shmem_swaplist_mutex);
 231
 232 static void shmem_free_blocks(struct inode *inode, long pages)
 233 {
 234         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 235         if (sbinfo->max_blocks) {
 236                 percpu_counter_add(&sbinfo->used_blocks, -pages);
 237                 spin_lock(&inode->i_lock);
 238                 inode->i_blocks -= pages*BLOCKS_PER_PAGE;
 239                 spin_unlock(&inode->i_lock);
 240         }
 241 }
 242
 243 static int shmem_reserve_inode(struct super_block *sb)
 244 {
 245         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
 246         if (sbinfo->max_inodes) {
 247                 spin_lock(&sbinfo->stat_lock);
 248                 if (!sbinfo->free_inodes) {
 249                         spin_unlock(&sbinfo->stat_lock);
 250                         return -ENOSPC;
 251                 }
 252                 sbinfo->free_inodes--;
 253                 spin_unlock(&sbinfo->stat_lock);
 254         }
 255         return 0;
 256 }
 257
 258 static void shmem_free_inode(struct super_block *sb)
 259 {
 260         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
 261         if (sbinfo->max_inodes) {
 262                 spin_lock(&sbinfo->stat_lock);
 263                 sbinfo->free_inodes++;
 264                 spin_unlock(&sbinfo->stat_lock);
 265         }
 266 }
 267
 268 /**
 269  * shmem_recalc_inode - recalculate the size of an inode
 270  * @inode: inode to recalc
 271  *
 272  * We have to calculate the free blocks since the mm can drop
 273  * undirtied hole pages behind our back.
 274  *
 275  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
 276  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
 277  *
 278  * It has to be called with the spinlock held.
 279  */
 280 static void shmem_recalc_inode(struct inode *inode)
 281 {
 282         struct shmem_inode_info *info = SHMEM_I(inode);
 283         long freed;
 284
 285         freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
 286         if (freed > 0) {
 287                 info->alloced -= freed;
 288                 shmem_unacct_blocks(info->flags, freed);
 289                 shmem_free_blocks(inode, freed);
 290         }
 291 }
 292
 293 /**
 294  * shmem_swp_entry - find the swap vector position in the info structure
 295  * @info:  info structure for the inode
 296  * @index: index of the page to find
 297  * @page:  optional page to add to the structure. Has to be preset to
 298  *         all zeros
 299  *
 300  * If there is no space allocated yet it will return NULL when
 301  * page is NULL, else it will use the page for the needed block,
 302  * setting it to NULL on return to indicate that it has been used.
 303  *
 304  * The swap vector is organized the following way:
 305  *
 306  * There are SHMEM_NR_DIRECT entries directly stored in the
 307  * shmem_inode_info structure. So small files do not need an addional
 308  * allocation.
 309  *
 310  * For pages with index > SHMEM_NR_DIRECT there is the pointer
 311  * i_indirect which points to a page which holds in the first half
 312  * doubly indirect blocks, in the second half triple indirect blocks:
 313  *
 314  * For an artificial ENTRIES_PER_PAGE = 4 this would lead to the
 315  * following layout (for SHMEM_NR_DIRECT == 16):
 316  *
 317  * i_indirect -> dir --> 16-19
 318  *            |      +-> 20-23
 319  *            |
 320  *            +-->dir2 --> 24-27
 321  *            |        +-> 28-31
 322  *            |        +-> 32-35
 323  *            |        +-> 36-39
 324  *            |
 325  *            +-->dir3 --> 40-43
 326  *                     +-> 44-47
 327  *                     +-> 48-51
 328  *                     +-> 52-55
 329  */
 330 static swp_entry_t *shmem_swp_entry(struct shmem_inode_info *info, unsigned long index, struct page **page)
 331 {
 332         unsigned long offset;
 333         struct page **dir;
 334         struct page *subdir;
 335
 336         if (index < SHMEM_NR_DIRECT) {
 337                 shmem_swp_balance_unmap();
 338                 return info->i_direct+index;
 339         }
 340         if (!info->i_indirect) {
 341                 if (page) {
 342                         info->i_indirect = *page;
 343                         *page = NULL;
 344                 }
 345                 return NULL;                    /* need another page */
 346         }
 347
 348         index -= SHMEM_NR_DIRECT;
 349         offset = index % ENTRIES_PER_PAGE;
 350         index /= ENTRIES_PER_PAGE;
 351         dir = shmem_dir_map(info->i_indirect);
 352
 353         if (index >= ENTRIES_PER_PAGE/2) {
 354                 index -= ENTRIES_PER_PAGE/2;
 355                 dir += ENTRIES_PER_PAGE/2 + index/ENTRIES_PER_PAGE;
 356                 index %= ENTRIES_PER_PAGE;
 357                 subdir = *dir;
 358                 if (!subdir) {
 359                         if (page) {
 360                                 *dir = *page;
 361                                 *page = NULL;
 362                         }
 363                         shmem_dir_unmap(dir);
 364                         return NULL;            /* need another page */
 365                 }
 366                 shmem_dir_unmap(dir);
 367                 dir = shmem_dir_map(subdir);
 368         }
 369
 370         dir += index;
 371         subdir = *dir;
 372         if (!subdir) {
 373                 if (!page || !(subdir = *page)) {
 374                         shmem_dir_unmap(dir);
 375                         return NULL;            /* need a page */
 376                 }
 377                 *dir = subdir;
 378                 *page = NULL;
 379         }
 380         shmem_dir_unmap(dir);
 381         return shmem_swp_map(subdir) + offset;
 382 }
 383
 384 static void shmem_swp_set(struct shmem_inode_info *info, swp_entry_t *entry, unsigned long value)
 385 {
 386         long incdec = value? 1: -1;
 387
 388         entry->val = value;
 389         info->swapped += incdec;
 390         if ((unsigned long)(entry - info->i_direct) >= SHMEM_NR_DIRECT) {
 391                 struct page *page = kmap_atomic_to_page(entry);
 392                 set_page_private(page, page_private(page) + incdec);
 393         }
 394 }
 395
 396 /**
 397  * shmem_swp_alloc - get the position of the swap entry for the page.
 398  * @info:       info structure for the inode
 399  * @index:      index of the page to find
 400  * @sgp:        check and recheck i_size? skip allocation?
 401  *
 402  * If the entry does not exist, allocate it.
 403  */
 404 static swp_entry_t *shmem_swp_alloc(struct shmem_inode_info *info, unsigned long index, enum sgp_type sgp)
 405 {
 406         struct inode *inode = &info->vfs_inode;
 407         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 408         struct page *page = NULL;
 409         swp_entry_t *entry;
 410
 411         if (sgp != SGP_WRITE &&
 412             ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode))
 413                 return ERR_PTR(-EINVAL);
 414
 415         while (!(entry = shmem_swp_entry(info, index, &page))) {
 416                 if (sgp == SGP_READ)
 417                         return shmem_swp_map(ZERO_PAGE(0));
 418                 /*
 419                  * Test used_blocks against 1 less max_blocks, since we have 1 data
 420                  * page (and perhaps indirect index pages) yet to allocate:
 421                  * a waste to allocate index if we cannot allocate data.
 422                  */
 423                 if (sbinfo->max_blocks) {
 424                         if (percpu_counter_compare(&sbinfo->used_blocks,
 425                                                 sbinfo->max_blocks - 1) >= 0)
 426                                 return ERR_PTR(-ENOSPC);
 427                         percpu_counter_inc(&sbinfo->used_blocks);
 428                         spin_lock(&inode->i_lock);
 429                         inode->i_blocks += BLOCKS_PER_PAGE;
 430                         spin_unlock(&inode->i_lock);
 431                 }
 432
 433                 spin_unlock(&info->lock);
 434                 page = shmem_dir_alloc(mapping_gfp_mask(inode->i_mapping));
 435                 spin_lock(&info->lock);
 436
 437                 if (!page) {
 438                         shmem_free_blocks(inode, 1);
 439                         return ERR_PTR(-ENOMEM);
 440                 }
 441                 if (sgp != SGP_WRITE &&
 442                     ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
 443                         entry = ERR_PTR(-EINVAL);
 444                         break;
 445                 }
 446                 if (info->next_index <= index)
 447                         info->next_index = index + 1;
 448         }
 449         if (page) {
 450                 /* another task gave its page, or truncated the file */
 451                 shmem_free_blocks(inode, 1);
 452                 shmem_dir_free(page);
 453         }
 454         if (info->next_index <= index && !IS_ERR(entry))
 455                 info->next_index = index + 1;
 456         return entry;
 457 }
 458
 459 /**
 460  * shmem_free_swp - free some swap entries in a directory
 461  * @dir:        pointer to the directory
 462  * @edir:       pointer after last entry of the directory
 463  * @punch_lock: pointer to spinlock when needed for the holepunch case
 464  */
 465 static int shmem_free_swp(swp_entry_t *dir, swp_entry_t *edir,
 466                                                 spinlock_t *punch_lock)
 467 {
 468         spinlock_t *punch_unlock = NULL;
 469         swp_entry_t *ptr;
 470         int freed = 0;
 471
 472         for (ptr = dir; ptr < edir; ptr++) {
 473                 if (ptr->val) {
 474                         if (unlikely(punch_lock)) {
 475                                 punch_unlock = punch_lock;
 476                                 punch_lock = NULL;
 477                                 spin_lock(punch_unlock);
 478                                 if (!ptr->val)
 479                                         continue;
 480                         }
 481                         free_swap_and_cache(*ptr);
 482                         *ptr = (swp_entry_t){0};
 483                         freed++;
 484                 }
 485         }
 486         if (punch_unlock)
 487                 spin_unlock(punch_unlock);
 488         return freed;
 489 }
 490
 491 static int shmem_map_and_free_swp(struct page *subdir, int offset,
 492                 int limit, struct page ***dir, spinlock_t *punch_lock)
 493 {
 494         swp_entry_t *ptr;
 495         int freed = 0;
 496
 497         ptr = shmem_swp_map(subdir);
 498         for (; offset < limit; offset += LATENCY_LIMIT) {
 499                 int size = limit - offset;
 500                 if (size > LATENCY_LIMIT)
 501                         size = LATENCY_LIMIT;
 502                 freed += shmem_free_swp(ptr+offset, ptr+offset+size,
 503                                                         punch_lock);
 504                 if (need_resched()) {
 505                         shmem_swp_unmap(ptr);
 506                         if (*dir) {
 507                                 shmem_dir_unmap(*dir);
 508                                 *dir = NULL;
 509                         }
 510                         cond_resched();
 511                         ptr = shmem_swp_map(subdir);
 512                 }
 513         }
 514         shmem_swp_unmap(ptr);
 515         return freed;
 516 }
 517
 518 static void shmem_free_pages(struct list_head *next)
 519 {
 520         struct page *page;
 521         int freed = 0;
 522
 523         do {
 524                 page = container_of(next, struct page, lru);
 525                 next = next->next;
 526                 shmem_dir_free(page);
 527                 freed++;
 528                 if (freed >= LATENCY_LIMIT) {
 529                         cond_resched();
 530                         freed = 0;
 531                 }
 532         } while (next);
 533 }
 534
 535 static void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end)
 536 {
 537         struct shmem_inode_info *info = SHMEM_I(inode);
 538         unsigned long idx;
 539         unsigned long size;
 540         unsigned long limit;
 541         unsigned long stage;
 542         unsigned long diroff;
 543         struct page **dir;
 544         struct page *topdir;
 545         struct page *middir;
 546         struct page *subdir;
 547         swp_entry_t *ptr;
 548         LIST_HEAD(pages_to_free);
 549         long nr_pages_to_free = 0;
 550         long nr_swaps_freed = 0;
 551         int offset;
 552         int freed;
 553         int punch_hole;
 554         spinlock_t *needs_lock;
 555         spinlock_t *punch_lock;
 556         unsigned long upper_limit;
 557
 558         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
 559         idx = (start + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 560         if (idx >= info->next_index)
 561                 return;
 562
 563         spin_lock(&info->lock);
 564         info->flags |= SHMEM_TRUNCATE;
 565         if (likely(end == (loff_t) -1)) {
 566                 limit = info->next_index;
 567                 upper_limit = SHMEM_MAX_INDEX;
 568                 info->next_index = idx;
 569                 needs_lock = NULL;
 570                 punch_hole = 0;
 571         } else {
 572                 if (end + 1 >= inode->i_size) { /* we may free a little more */
 573                         limit = (inode->i_size + PAGE_CACHE_SIZE - 1) >>
 574                                                         PAGE_CACHE_SHIFT;
 575                         upper_limit = SHMEM_MAX_INDEX;
 576                 } else {
 577                         limit = (end + 1) >> PAGE_CACHE_SHIFT;
 578                         upper_limit = limit;
 579                 }
 580                 needs_lock = &info->lock;
 581                 punch_hole = 1;
 582         }
 583
 584         topdir = info->i_indirect;
 585         if (topdir && idx <= SHMEM_NR_DIRECT && !punch_hole) {
 586                 info->i_indirect = NULL;
 587                 nr_pages_to_free++;
 588                 list_add(&topdir->lru, &pages_to_free);
 589         }
 590         spin_unlock(&info->lock);
 591
 592         if (info->swapped && idx < SHMEM_NR_DIRECT) {
 593                 ptr = info->i_direct;
 594                 size = limit;
 595                 if (size > SHMEM_NR_DIRECT)
 596                         size = SHMEM_NR_DIRECT;
 597                 nr_swaps_freed = shmem_free_swp(ptr+idx, ptr+size, needs_lock);
 598         }
 599
 600         /*
 601          * If there are no indirect blocks or we are punching a hole
 602          * below indirect blocks, nothing to be done.
 603          */
 604         if (!topdir || limit <= SHMEM_NR_DIRECT)
 605                 goto done2;
 606
 607         /*
 608          * The truncation case has already dropped info->lock, and we're safe
 609          * because i_size and next_index have already been lowered, preventing
 610          * access beyond.  But in the punch_hole case, we still need to take
 611          * the lock when updating the swap directory, because there might be
 612          * racing accesses by shmem_getpage(SGP_CACHE), shmem_unuse_inode or
 613          * shmem_writepage.  However, whenever we find we can remove a whole
 614          * directory page (not at the misaligned start or end of the range),
 615          * we first NULLify its pointer in the level above, and then have no
 616          * need to take the lock when updating its contents: needs_lock and
 617          * punch_lock (either pointing to info->lock or NULL) manage this.
 618          */
 619
 620         upper_limit -= SHMEM_NR_DIRECT;
 621         limit -= SHMEM_NR_DIRECT;
 622         idx = (idx > SHMEM_NR_DIRECT)? (idx - SHMEM_NR_DIRECT): 0;
 623         offset = idx % ENTRIES_PER_PAGE;
 624         idx -= offset;
 625
 626         dir = shmem_dir_map(topdir);
 627         stage = ENTRIES_PER_PAGEPAGE/2;
 628         if (idx < ENTRIES_PER_PAGEPAGE/2) {
 629                 middir = topdir;
 630                 diroff = idx/ENTRIES_PER_PAGE;
 631         } else {
 632                 dir += ENTRIES_PER_PAGE/2;
 633                 dir += (idx - ENTRIES_PER_PAGEPAGE/2)/ENTRIES_PER_PAGEPAGE;
 634                 while (stage <= idx)
 635                         stage += ENTRIES_PER_PAGEPAGE;
 636                 middir = *dir;
 637                 if (*dir) {
 638                         diroff = ((idx - ENTRIES_PER_PAGEPAGE/2) %
 639                                 ENTRIES_PER_PAGEPAGE) / ENTRIES_PER_PAGE;
 640                         if (!diroff && !offset && upper_limit >= stage) {
 641                                 if (needs_lock) {
 642                                         spin_lock(needs_lock);
 643                                         *dir = NULL;
 644                                         spin_unlock(needs_lock);
 645                                         needs_lock = NULL;
 646                                 } else
 647                                         *dir = NULL;
 648                                 nr_pages_to_free++;
 649                                 list_add(&middir->lru, &pages_to_free);
 650                         }
 651                         shmem_dir_unmap(dir);
 652                         dir = shmem_dir_map(middir);
 653                 } else {
 654                         diroff = 0;
 655                         offset = 0;
 656                         idx = stage;
 657                 }
 658         }
 659
 660         for (; idx < limit; idx += ENTRIES_PER_PAGE, diroff++) {
 661                 if (unlikely(idx == stage)) {
 662                         shmem_dir_unmap(dir);
 663                         dir = shmem_dir_map(topdir) +
 664                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
 665                         while (!*dir) {
 666                                 dir++;
 667                                 idx += ENTRIES_PER_PAGEPAGE;
 668                                 if (idx >= limit)
 669                                         goto done1;
 670                         }
 671                         stage = idx + ENTRIES_PER_PAGEPAGE;
 672                         middir = *dir;
 673                         if (punch_hole)
 674                                 needs_lock = &info->lock;
 675                         if (upper_limit >= stage) {
 676                                 if (needs_lock) {
 677                                         spin_lock(needs_lock);
 678                                         *dir = NULL;
 679                                         spin_unlock(needs_lock);
 680                                         needs_lock = NULL;
 681                                 } else
 682                                         *dir = NULL;
 683                                 nr_pages_to_free++;
 684                                 list_add(&middir->lru, &pages_to_free);
 685                         }
 686                         shmem_dir_unmap(dir);
 687                         cond_resched();
 688                         dir = shmem_dir_map(middir);
 689                         diroff = 0;
 690                 }
 691                 punch_lock = needs_lock;
 692                 subdir = dir[diroff];
 693                 if (subdir && !offset && upper_limit-idx >= ENTRIES_PER_PAGE) {
 694                         if (needs_lock) {
 695                                 spin_lock(needs_lock);
 696                                 dir[diroff] = NULL;
 697                                 spin_unlock(needs_lock);
 698                                 punch_lock = NULL;
 699                         } else
 700                                 dir[diroff] = NULL;
 701                         nr_pages_to_free++;
 702                         list_add(&subdir->lru, &pages_to_free);
 703                 }
 704                 if (subdir && page_private(subdir) /* has swap entries */) {
 705                         size = limit - idx;
 706                         if (size > ENTRIES_PER_PAGE)
 707                                 size = ENTRIES_PER_PAGE;
 708                         freed = shmem_map_and_free_swp(subdir,
 709                                         offset, size, &dir, punch_lock);
 710                         if (!dir)
 711                                 dir = shmem_dir_map(middir);
 712                         nr_swaps_freed += freed;
 713                         if (offset || punch_lock) {
 714                                 spin_lock(&info->lock);
 715                                 set_page_private(subdir,
 716                                         page_private(subdir) - freed);
 717                                 spin_unlock(&info->lock);
 718                         } else
 719                                 BUG_ON(page_private(subdir) != freed);
 720                 }
 721                 offset = 0;
 722         }
 723 done1:
 724         shmem_dir_unmap(dir);
 725 done2:
 726         if (inode->i_mapping->nrpages && (info->flags & SHMEM_PAGEIN)) {
 727                 /*
 728                  * Call truncate_inode_pages again: racing shmem_unuse_inode
 729                  * may have swizzled a page in from swap since
 730                  * truncate_pagecache or generic_delete_inode did it, before we
 731                  * lowered next_index.  Also, though shmem_getpage checks
 732                  * i_size before adding to cache, no recheck after: so fix the
 733                  * narrow window there too.
 734                  *
 735                  * Recalling truncate_inode_pages_range and unmap_mapping_range
 736                  * every time for punch_hole (which never got a chance to clear
 737                  * SHMEM_PAGEIN at the start of vmtruncate_range) is expensive,
 738                  * yet hardly ever necessary: try to optimize them out later.
 739                  */
 740                 truncate_inode_pages_range(inode->i_mapping, start, end);
 741                 if (punch_hole)
 742                         unmap_mapping_range(inode->i_mapping, start,
 743                                                         end - start, 1);
 744         }
 745
 746         spin_lock(&info->lock);
 747         info->flags &= ~SHMEM_TRUNCATE;
 748         info->swapped -= nr_swaps_freed;
 749         if (nr_pages_to_free)
 750                 shmem_free_blocks(inode, nr_pages_to_free);
 751         shmem_recalc_inode(inode);
 752         spin_unlock(&info->lock);
 753
 754         /*
 755          * Empty swap vector directory pages to be freed?
 756          */
 757         if (!list_empty(&pages_to_free)) {
 758                 pages_to_free.prev->next = NULL;
 759                 shmem_free_pages(pages_to_free.next);
 760         }
 761 }
 762
 763 static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
 764 {
 765         struct inode *inode = dentry->d_inode;
 766         loff_t newsize = attr->ia_size;
 767         int error;
 768
 769         error = inode_change_ok(inode, attr);
 770         if (error)
 771                 return error;
 772
 773         if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)
 774                                         && newsize != inode->i_size) {
 775                 struct page *page = NULL;
 776
 777                 if (newsize < inode->i_size) {
 778                         /*
 779                          * If truncating down to a partial page, then
 780                          * if that page is already allocated, hold it
 781                          * in memory until the truncation is over, so
 782                          * truncate_partial_page cannot miss it were
 783                          * it assigned to swap.
 784                          */
 785                         if (newsize & (PAGE_CACHE_SIZE-1)) {
 786                                 (void) shmem_getpage(inode,
 787                                         newsize >> PAGE_CACHE_SHIFT,
 788                                                 &page, SGP_READ, NULL);
 789                                 if (page)
 790                                         unlock_page(page);
 791                         }
 792                         /*
 793                          * Reset SHMEM_PAGEIN flag so that shmem_truncate can
 794                          * detect if any pages might have been added to cache
 795                          * after truncate_inode_pages.  But we needn't bother
 796                          * if it's being fully truncated to zero-length: the
 797                          * nrpages check is efficient enough in that case.
 798                          */
 799                         if (newsize) {
 800                                 struct shmem_inode_info *info = SHMEM_I(inode);
 801                                 spin_lock(&info->lock);
 802                                 info->flags &= ~SHMEM_PAGEIN;
 803                                 spin_unlock(&info->lock);
 804                         }
 805                 }
 806
 807                 /* XXX(truncate): truncate_setsize should be called last */
 808                 truncate_setsize(inode, newsize);
 809                 if (page)
 810                         page_cache_release(page);
 811                 shmem_truncate_range(inode, newsize, (loff_t)-1);
 812         }
 813
 814         setattr_copy(inode, attr);
 815 #ifdef CONFIG_TMPFS_POSIX_ACL
 816         if (attr->ia_valid & ATTR_MODE)
 817                 error = generic_acl_chmod(inode);
 818 #endif
 819         return error;
 820 }
 821
 822 static void shmem_evict_inode(struct inode *inode)
 823 {
 824         struct shmem_inode_info *info = SHMEM_I(inode);
 825
 826         if (inode->i_mapping->a_ops == &shmem_aops) {
 827                 truncate_inode_pages(inode->i_mapping, 0);
 828                 shmem_unacct_size(info->flags, inode->i_size);
 829                 inode->i_size = 0;
 830                 shmem_truncate_range(inode, 0, (loff_t)-1);
 831                 if (!list_empty(&info->swaplist)) {
 832                         mutex_lock(&shmem_swaplist_mutex);
 833                         list_del_init(&info->swaplist);
 834                         mutex_unlock(&shmem_swaplist_mutex);
 835                 }
 836         }
 837         BUG_ON(inode->i_blocks);
 838         shmem_free_inode(inode->i_sb);
 839         end_writeback(inode);
 840 }
 841
 842 static inline int shmem_find_swp(swp_entry_t entry, swp_entry_t *dir, swp_entry_t *edir)
 843 {
 844         swp_entry_t *ptr;
 845
 846         for (ptr = dir; ptr < edir; ptr++) {
 847                 if (ptr->val == entry.val)
 848                         return ptr - dir;
 849         }
 850         return -1;
 851 }
 852
 853 static int shmem_unuse_inode(struct shmem_inode_info *info, swp_entry_t entry, struct page *page)
 854 {
 855         struct address_space *mapping;
 856         unsigned long idx;
 857         unsigned long size;
 858         unsigned long limit;
 859         unsigned long stage;
 860         struct page **dir;
 861         struct page *subdir;
 862         swp_entry_t *ptr;
 863         int offset;
 864         int error;
 865
 866         idx = 0;
 867         ptr = info->i_direct;
 868         spin_lock(&info->lock);
 869         if (!info->swapped) {
 870                 list_del_init(&info->swaplist);
 871                 goto lost2;
 872         }
 873         limit = info->next_index;
 874         size = limit;
 875         if (size > SHMEM_NR_DIRECT)
 876                 size = SHMEM_NR_DIRECT;
 877         offset = shmem_find_swp(entry, ptr, ptr+size);
 878         if (offset >= 0) {
 879                 shmem_swp_balance_unmap();
 880                 goto found;
 881         }
 882         if (!info->i_indirect)
 883                 goto lost2;
 884
 885         dir = shmem_dir_map(info->i_indirect);
 886         stage = SHMEM_NR_DIRECT + ENTRIES_PER_PAGEPAGE/2;
 887
 888         for (idx = SHMEM_NR_DIRECT; idx < limit; idx += ENTRIES_PER_PAGE, dir++) {
 889                 if (unlikely(idx == stage)) {
 890                         shmem_dir_unmap(dir-1);
 891                         if (cond_resched_lock(&info->lock)) {
 892                                 /* check it has not been truncated */
 893                                 if (limit > info->next_index) {
 894                                         limit = info->next_index;
 895                                         if (idx >= limit)
 896                                                 goto lost2;
 897                                 }
 898                         }
 899                         dir = shmem_dir_map(info->i_indirect) +
 900                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
 901                         while (!*dir) {
 902                                 dir++;
 903                                 idx += ENTRIES_PER_PAGEPAGE;
 904                                 if (idx >= limit)
 905                                         goto lost1;
 906                         }
 907                         stage = idx + ENTRIES_PER_PAGEPAGE;
 908                         subdir = *dir;
 909                         shmem_dir_unmap(dir);
 910                         dir = shmem_dir_map(subdir);
 911                 }
 912                 subdir = *dir;
 913                 if (subdir && page_private(subdir)) {
 914                         ptr = shmem_swp_map(subdir);
 915                         size = limit - idx;
 916                         if (size > ENTRIES_PER_PAGE)
 917                                 size = ENTRIES_PER_PAGE;
 918                         offset = shmem_find_swp(entry, ptr, ptr+size);
 919                         shmem_swp_unmap(ptr);
 920                         if (offset >= 0) {
 921                                 shmem_dir_unmap(dir);
 922                                 ptr = shmem_swp_map(subdir);
 923                                 goto found;
 924                         }
 925                 }
 926         }
 927 lost1:
 928         shmem_dir_unmap(dir-1);
 929 lost2:
 930         spin_unlock(&info->lock);
 931         return 0;
 932 found:
 933         idx += offset;
 934         ptr += offset;
 935
 936         /*
 937          * Move _head_ to start search for next from here.
 938          * But be careful: shmem_evict_inode checks list_empty without taking
 939          * mutex, and there's an instant in list_move_tail when info->swaplist
 940          * would appear empty, if it were the only one on shmem_swaplist.  We
 941          * could avoid doing it if inode NULL; or use this minor optimization.
 942          */
 943         if (shmem_swaplist.next != &info->swaplist)
 944                 list_move_tail(&shmem_swaplist, &info->swaplist);
 945
 946         /*
 947          * We rely on shmem_swaplist_mutex, not only to protect the swaplist,
 948          * but also to hold up shmem_evict_inode(): so inode cannot be freed
 949          * beneath us (pagelock doesn't help until the page is in pagecache).
 950          */
 951         mapping = info->vfs_inode.i_mapping;
 952         error = add_to_page_cache_locked(page, mapping, idx, GFP_NOWAIT);
 953         /* which does mem_cgroup_uncharge_cache_page on error */
 954
 955         if (error == -EEXIST) {
 956                 struct page *filepage = find_get_page(mapping, idx);
 957                 error = 1;
 958                 if (filepage) {
 959                         /*
 960                          * There might be a more uptodate page coming down
 961                          * from a stacked writepage: forget our swappage if so.
 962                          */
 963                         if (PageUptodate(filepage))
 964                                 error = 0;
 965                         page_cache_release(filepage);
 966                 }
 967         }
 968         if (!error) {
 969                 delete_from_swap_cache(page);
 970                 set_page_dirty(page);
 971                 info->flags |= SHMEM_PAGEIN;
 972                 shmem_swp_set(info, ptr, 0);
 973                 swap_free(entry);
 974                 error = 1;      /* not an error, but entry was found */
 975         }
 976         shmem_swp_unmap(ptr);
 977         spin_unlock(&info->lock);
 978         return error;
 979 }
 980
 981 /*
 982  * shmem_unuse() search for an eventually swapped out shmem page.
 983  */
 984 int shmem_unuse(swp_entry_t entry, struct page *page)
 985 {
 986         struct list_head *p, *next;
 987         struct shmem_inode_info *info;
 988         int found = 0;
 989         int error;
 990
 991         /*
 992          * Charge page using GFP_KERNEL while we can wait, before taking
 993          * the shmem_swaplist_mutex which might hold up shmem_writepage().
 994          * Charged back to the user (not to caller) when swap account is used.
 995          * add_to_page_cache() will be called with GFP_NOWAIT.
 996          */
 997         error = mem_cgroup_cache_charge(page, current->mm, GFP_KERNEL);
 998         if (error)
 999                 goto out;
1000         /*
1001          * Try to preload while we can wait, to not make a habit of
1002          * draining atomic reserves; but don't latch on to this cpu,
1003          * it's okay if sometimes we get rescheduled after this.
1004          */
1005         error = radix_tree_preload(GFP_KERNEL);
1006         if (error)
1007                 goto uncharge;
1008         radix_tree_preload_end();
1009
1010         mutex_lock(&shmem_swaplist_mutex);
1011         list_for_each_safe(p, next, &shmem_swaplist) {
1012                 info = list_entry(p, struct shmem_inode_info, swaplist);
1013                 found = shmem_unuse_inode(info, entry, page);
1014                 cond_resched();
1015                 if (found)
1016                         break;
1017         }
1018         mutex_unlock(&shmem_swaplist_mutex);
1019
1020 uncharge:
1021         if (!found)
1022                 mem_cgroup_uncharge_cache_page(page);
1023         if (found < 0)
1024                 error = found;
1025 out:
1026         unlock_page(page);
1027         page_cache_release(page);
1028         return error;
1029 }
1030
1031 /*
1032  * Move the page from the page cache to the swap cache.
1033  */
1034 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
1035 {
1036         struct shmem_inode_info *info;
1037         swp_entry_t *entry, swap;
1038         struct address_space *mapping;
1039         unsigned long index;
1040         struct inode *inode;
1041
1042         BUG_ON(!PageLocked(page));
1043         mapping = page->mapping;
1044         index = page->index;
1045         inode = mapping->host;
1046         info = SHMEM_I(inode);
1047         if (info->flags & VM_LOCKED)
1048                 goto redirty;
1049         if (!total_swap_pages)
1050                 goto redirty;
1051
1052         /*
1053          * shmem_backing_dev_info's capabilities prevent regular writeback or
1054          * sync from ever calling shmem_writepage; but a stacking filesystem
1055          * may use the ->writepage of its underlying filesystem, in which case
1056          * tmpfs should write out to swap only in response to memory pressure,
1057          * and not for the writeback threads or sync.  However, in those cases,
1058          * we do still want to check if there's a redundant swappage to be
1059          * discarded.
1060          */
1061         if (wbc->for_reclaim)
1062                 swap = get_swap_page();
1063         else
1064                 swap.val = 0;
1065
1066         /*
1067          * Add inode to shmem_unuse()'s list of swapped-out inodes,
1068          * if it's not already there.  Do it now because we cannot take
1069          * mutex while holding spinlock, and must do so before the page
1070          * is moved to swap cache, when its pagelock no longer protects
1071          * the inode from eviction.  But don't unlock the mutex until
1072          * we've taken the spinlock, because shmem_unuse_inode() will
1073          * prune a !swapped inode from the swaplist under both locks.
1074          */
1075         if (swap.val) {
1076                 mutex_lock(&shmem_swaplist_mutex);
1077                 if (list_empty(&info->swaplist))
1078                         list_add_tail(&info->swaplist, &shmem_swaplist);
1079         }
1080
1081         spin_lock(&info->lock);
1082         if (swap.val)
1083                 mutex_unlock(&shmem_swaplist_mutex);
1084
1085         if (index >= info->next_index) {
1086                 BUG_ON(!(info->flags & SHMEM_TRUNCATE));
1087                 goto unlock;
1088         }
1089         entry = shmem_swp_entry(info, index, NULL);
1090         if (entry->val) {
1091                 /*
1092                  * The more uptodate page coming down from a stacked
1093                  * writepage should replace our old swappage.
1094                  */
1095                 free_swap_and_cache(*entry);
1096                 shmem_swp_set(info, entry, 0);
1097         }
1098         shmem_recalc_inode(inode);
1099
1100         if (swap.val && add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
1101                 delete_from_page_cache(page);
1102                 shmem_swp_set(info, entry, swap.val);
1103                 shmem_swp_unmap(entry);
1104                 spin_unlock(&info->lock);
1105                 swap_shmem_alloc(swap);
1106                 BUG_ON(page_mapped(page));
1107                 swap_writepage(page, wbc);
1108                 return 0;
1109         }
1110
1111         shmem_swp_unmap(entry);
1112 unlock:
1113         spin_unlock(&info->lock);
1114         /*
1115          * add_to_swap_cache() doesn't return -EEXIST, so we can safely
1116          * clear SWAP_HAS_CACHE flag.
1117          */
1118         swapcache_free(swap, NULL);
1119 redirty:
1120         set_page_dirty(page);
1121         if (wbc->for_reclaim)
1122                 return AOP_WRITEPAGE_ACTIVATE;  /* Return with page locked */
1123         unlock_page(page);
1124         return 0;
1125 }
1126
1127 #ifdef CONFIG_NUMA
1128 #ifdef CONFIG_TMPFS
1129 static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
1130 {
1131         char buffer[64];
1132
1133         if (!mpol || mpol->mode == MPOL_DEFAULT)
1134                 return;         /* show nothing */
1135
1136         mpol_to_str(buffer, sizeof(buffer), mpol, 1);
1137
1138         seq_printf(seq, ",mpol=%s", buffer);
1139 }
1140
1141 static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1142 {
1143         struct mempolicy *mpol = NULL;
1144         if (sbinfo->mpol) {
1145                 spin_lock(&sbinfo->stat_lock);  /* prevent replace/use races */
1146                 mpol = sbinfo->mpol;
1147                 mpol_get(mpol);
1148                 spin_unlock(&sbinfo->stat_lock);
1149         }
1150         return mpol;
1151 }
1152 #endif /* CONFIG_TMPFS */
1153
1154 static struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
1155                         struct shmem_inode_info *info, unsigned long idx)
1156 {
1157         struct mempolicy mpol, *spol;
1158         struct vm_area_struct pvma;
1159         struct page *page;
1160
1161         spol = mpol_cond_copy(&mpol,
1162                                 mpol_shared_policy_lookup(&info->policy, idx));
1163
1164         /* Create a pseudo vma that just contains the policy */
1165         pvma.vm_start = 0;
1166         pvma.vm_pgoff = idx;
1167         pvma.vm_ops = NULL;
1168         pvma.vm_policy = spol;
1169         page = swapin_readahead(entry, gfp, &pvma, 0);
1170         return page;
1171 }
1172
1173 static struct page *shmem_alloc_page(gfp_t gfp,
1174                         struct shmem_inode_info *info, unsigned long idx)
1175 {
1176         struct vm_area_struct pvma;
1177
1178         /* Create a pseudo vma that just contains the policy */
1179         pvma.vm_start = 0;
1180         pvma.vm_pgoff = idx;
1181         pvma.vm_ops = NULL;
1182         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx);
1183
1184         /*
1185          * alloc_page_vma() will drop the shared policy reference
1186          */
1187         return alloc_page_vma(gfp, &pvma, 0);
1188 }
1189 #else /* !CONFIG_NUMA */
1190 #ifdef CONFIG_TMPFS
1191 static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *p)
1192 {
1193 }
1194 #endif /* CONFIG_TMPFS */
1195
1196 static inline struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
1197                         struct shmem_inode_info *info, unsigned long idx)
1198 {
1199         return swapin_readahead(entry, gfp, NULL, 0);
1200 }
1201
1202 static inline struct page *shmem_alloc_page(gfp_t gfp,
1203                         struct shmem_inode_info *info, unsigned long idx)
1204 {
1205         return alloc_page(gfp);
1206 }
1207 #endif /* CONFIG_NUMA */
1208
1209 #if !defined(CONFIG_NUMA) || !defined(CONFIG_TMPFS)
1210 static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1211 {
1212         return NULL;
1213 }
1214 #endif
1215
1216 /*
1217  * shmem_getpage - either get the page from swap or allocate a new one
1218  *
1219  * If we allocate a new one we do not mark it dirty. That's up to the
1220  * vm. If we swap it in we mark it dirty since we also free the swap
1221  * entry since a page cannot live in both the swap and page cache
1222  */
1223 static int shmem_getpage(struct inode *inode, unsigned long idx,
1224                         struct page **pagep, enum sgp_type sgp, int *type)
1225 {
1226         struct address_space *mapping = inode->i_mapping;
1227         struct shmem_inode_info *info = SHMEM_I(inode);
1228         struct shmem_sb_info *sbinfo;
1229         struct page *filepage = *pagep;
1230         struct page *swappage;
1231         struct page *prealloc_page = NULL;
1232         swp_entry_t *entry;
1233         swp_entry_t swap;
1234         gfp_t gfp;
1235         int error;
1236
1237         if (idx >= SHMEM_MAX_INDEX)
1238                 return -EFBIG;
1239
1240         if (type)
1241                 *type = 0;
1242
1243         /*
1244          * Normally, filepage is NULL on entry, and either found
1245          * uptodate immediately, or allocated and zeroed, or read
1246          * in under swappage, which is then assigned to filepage.
1247          * But shmem_readpage (required for splice) passes in a locked
1248          * filepage, which may be found not uptodate by other callers
1249          * too, and may need to be copied from the swappage read in.
1250          */
1251 repeat:
1252         if (!filepage)
1253                 filepage = find_lock_page(mapping, idx);
1254         if (filepage && PageUptodate(filepage))
1255                 goto done;
1256         gfp = mapping_gfp_mask(mapping);
1257         if (!filepage) {
1258                 /*
1259                  * Try to preload while we can wait, to not make a habit of
1260                  * draining atomic reserves; but don't latch on to this cpu.
1261                  */
1262                 error = radix_tree_preload(gfp & ~__GFP_HIGHMEM);
1263                 if (error)
1264                         goto failed;
1265                 radix_tree_preload_end();
1266                 if (sgp != SGP_READ && !prealloc_page) {
1267                         /* We don't care if this fails */
1268                         prealloc_page = shmem_alloc_page(gfp, info, idx);
1269                         if (prealloc_page) {
1270                                 if (mem_cgroup_cache_charge(prealloc_page,
1271                                                 current->mm, GFP_KERNEL)) {
1272                                         page_cache_release(prealloc_page);
1273                                         prealloc_page = NULL;
1274                                 }
1275                         }
1276                 }
1277         }
1278         error = 0;
1279
1280         spin_lock(&info->lock);
1281         shmem_recalc_inode(inode);
1282         entry = shmem_swp_alloc(info, idx, sgp);
1283         if (IS_ERR(entry)) {
1284                 spin_unlock(&info->lock);
1285                 error = PTR_ERR(entry);
1286                 goto failed;
1287         }
1288         swap = *entry;
1289
1290         if (swap.val) {
1291                 /* Look it up and read it in.. */
1292                 swappage = lookup_swap_cache(swap);
1293                 if (!swappage) {
1294                         shmem_swp_unmap(entry);
1295                         /* here we actually do the io */
1296                         if (type && !(*type & VM_FAULT_MAJOR)) {
1297                                 __count_vm_event(PGMAJFAULT);
1298                                 *type |= VM_FAULT_MAJOR;
1299                         }
1300                         spin_unlock(&info->lock);
1301                         swappage = shmem_swapin(swap, gfp, info, idx);
1302                         if (!swappage) {
1303                                 spin_lock(&info->lock);
1304                                 entry = shmem_swp_alloc(info, idx, sgp);
1305                                 if (IS_ERR(entry))
1306                                         error = PTR_ERR(entry);
1307                                 else {
1308                                         if (entry->val == swap.val)
1309                                                 error = -ENOMEM;
1310                                         shmem_swp_unmap(entry);
1311                                 }
1312                                 spin_unlock(&info->lock);
1313                                 if (error)
1314                                         goto failed;
1315                                 goto repeat;
1316                         }
1317                         wait_on_page_locked(swappage);
1318                         page_cache_release(swappage);
1319                         goto repeat;
1320                 }
1321
1322                 /* We have to do this with page locked to prevent races */
1323                 if (!trylock_page(swappage)) {
1324                         shmem_swp_unmap(entry);
1325                         spin_unlock(&info->lock);
1326                         wait_on_page_locked(swappage);
1327                         page_cache_release(swappage);
1328                         goto repeat;
1329                 }
1330                 if (PageWriteback(swappage)) {
1331                         shmem_swp_unmap(entry);
1332                         spin_unlock(&info->lock);
1333                         wait_on_page_writeback(swappage);
1334                         unlock_page(swappage);
1335                         page_cache_release(swappage);
1336                         goto repeat;
1337                 }
1338                 if (!PageUptodate(swappage)) {
1339                         shmem_swp_unmap(entry);
1340                         spin_unlock(&info->lock);
1341                         unlock_page(swappage);
1342                         page_cache_release(swappage);
1343                         error = -EIO;
1344                         goto failed;
1345                 }
1346
1347                 if (filepage) {
1348                         shmem_swp_set(info, entry, 0);
1349                         shmem_swp_unmap(entry);
1350                         delete_from_swap_cache(swappage);
1351                         spin_unlock(&info->lock);
1352                         copy_highpage(filepage, swappage);
1353                         unlock_page(swappage);
1354                         page_cache_release(swappage);
1355                         flush_dcache_page(filepage);
1356                         SetPageUptodate(filepage);
1357                         set_page_dirty(filepage);
1358                         swap_free(swap);
1359                 } else if (!(error = add_to_page_cache_locked(swappage, mapping,
1360                                         idx, GFP_NOWAIT))) {
1361                         info->flags |= SHMEM_PAGEIN;
1362                         shmem_swp_set(info, entry, 0);
1363                         shmem_swp_unmap(entry);
1364                         delete_from_swap_cache(swappage);
1365                         spin_unlock(&info->lock);
1366                         filepage = swappage;
1367                         set_page_dirty(filepage);
1368                         swap_free(swap);
1369                 } else {
1370                         shmem_swp_unmap(entry);
1371                         spin_unlock(&info->lock);
1372                         if (error == -ENOMEM) {
1373                                 /*
1374                                  * reclaim from proper memory cgroup and
1375                                  * call memcg's OOM if needed.
1376                                  */
1377                                 error = mem_cgroup_shmem_charge_fallback(
1378                                                                 swappage,
1379                                                                 current->mm,
1380                                                                 gfp);
1381                                 if (error) {
1382                                         unlock_page(swappage);
1383                                         page_cache_release(swappage);
1384                                         goto failed;
1385                                 }
1386                         }
1387                         unlock_page(swappage);
1388                         page_cache_release(swappage);
1389                         goto repeat;
1390                 }
1391         } else if (sgp == SGP_READ && !filepage) {
1392                 shmem_swp_unmap(entry);
1393                 filepage = find_get_page(mapping, idx);
1394                 if (filepage &&
1395                     (!PageUptodate(filepage) || !trylock_page(filepage))) {
1396                         spin_unlock(&info->lock);
1397                         wait_on_page_locked(filepage);
1398                         page_cache_release(filepage);
1399                         filepage = NULL;
1400                         goto repeat;
1401                 }
1402                 spin_unlock(&info->lock);
1403         } else {
1404                 shmem_swp_unmap(entry);
1405                 sbinfo = SHMEM_SB(inode->i_sb);
1406                 if (sbinfo->max_blocks) {
1407                         if (percpu_counter_compare(&sbinfo->used_blocks,
1408                                                 sbinfo->max_blocks) >= 0 ||
1409                             shmem_acct_block(info->flags))
1410                                 goto nospace;
1411                         percpu_counter_inc(&sbinfo->used_blocks);
1412                         spin_lock(&inode->i_lock);
1413                         inode->i_blocks += BLOCKS_PER_PAGE;
1414                         spin_unlock(&inode->i_lock);
1415                 } else if (shmem_acct_block(info->flags))
1416                         goto nospace;
1417
1418                 if (!filepage) {
1419                         int ret;
1420
1421                         if (!prealloc_page) {
1422                                 spin_unlock(&info->lock);
1423                                 filepage = shmem_alloc_page(gfp, info, idx);
1424                                 if (!filepage) {
1425                                         shmem_unacct_blocks(info->flags, 1);
1426                                         shmem_free_blocks(inode, 1);
1427                                         error = -ENOMEM;
1428                                         goto failed;
1429                                 }
1430                                 SetPageSwapBacked(filepage);
1431
1432                                 /*
1433                                  * Precharge page while we can wait, compensate
1434                                  * after
1435                                  */
1436                                 error = mem_cgroup_cache_charge(filepage,
1437                                         current->mm, GFP_KERNEL);
1438                                 if (error) {
1439                                         page_cache_release(filepage);
1440                                         shmem_unacct_blocks(info->flags, 1);
1441                                         shmem_free_blocks(inode, 1);
1442                                         filepage = NULL;
1443                                         goto failed;
1444                                 }
1445
1446                                 spin_lock(&info->lock);
1447                         } else {
1448                                 filepage = prealloc_page;
1449                                 prealloc_page = NULL;
1450                                 SetPageSwapBacked(filepage);
1451                         }
1452
1453                         entry = shmem_swp_alloc(info, idx, sgp);
1454                         if (IS_ERR(entry))
1455                                 error = PTR_ERR(entry);
1456                         else {
1457                                 swap = *entry;
1458                                 shmem_swp_unmap(entry);
1459                         }
1460                         ret = error || swap.val;
1461                         if (ret)
1462                                 mem_cgroup_uncharge_cache_page(filepage);
1463                         else
1464                                 ret = add_to_page_cache_lru(filepage, mapping,
1465                                                 idx, GFP_NOWAIT);
1466                         /*
1467                          * At add_to_page_cache_lru() failure, uncharge will
1468                          * be done automatically.
1469                          */
1470                         if (ret) {
1471                                 spin_unlock(&info->lock);
1472                                 page_cache_release(filepage);
1473                                 shmem_unacct_blocks(info->flags, 1);
1474                                 shmem_free_blocks(inode, 1);
1475                                 filepage = NULL;
1476                                 if (error)
1477                                         goto failed;
1478                                 goto repeat;
1479                         }
1480                         info->flags |= SHMEM_PAGEIN;
1481                 }
1482
1483                 info->alloced++;
1484                 spin_unlock(&info->lock);
1485                 clear_highpage(filepage);
1486                 flush_dcache_page(filepage);
1487                 SetPageUptodate(filepage);
1488                 if (sgp == SGP_DIRTY)
1489                         set_page_dirty(filepage);
1490         }
1491 done:
1492         *pagep = filepage;
1493         error = 0;
1494         goto out;
1495
1496 nospace:
1497         /*
1498          * Perhaps the page was brought in from swap between find_lock_page
1499          * and taking info->lock?  We allow for that at add_to_page_cache_lru,
1500          * but must also avoid reporting a spurious ENOSPC while working on a
1501          * full tmpfs.  (When filepage has been passed in to shmem_getpage, it
1502          * is already in page cache, which prevents this race from occurring.)
1503          */
1504         if (!filepage) {
1505                 struct page *page = find_get_page(mapping, idx);
1506                 if (page) {
1507                         spin_unlock(&info->lock);
1508                         page_cache_release(page);
1509                         goto repeat;
1510                 }
1511         }
1512         spin_unlock(&info->lock);
1513         error = -ENOSPC;
1514 failed:
1515         if (*pagep != filepage) {
1516                 unlock_page(filepage);
1517                 page_cache_release(filepage);
1518         }
1519 out:
1520         if (prealloc_page) {
1521                 mem_cgroup_uncharge_cache_page(prealloc_page);
1522                 page_cache_release(prealloc_page);
1523         }
1524         return error;
1525 }
1526
1527 static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1528 {
1529         struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1530         int error;
1531         int ret;
1532
1533         if (((loff_t)vmf->pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
1534                 return VM_FAULT_SIGBUS;
1535
1536         error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret);
1537         if (error)
1538                 return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1539
1540         return ret | VM_FAULT_LOCKED;
1541 }
1542
1543 #ifdef CONFIG_NUMA
1544 static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *new)
1545 {
1546         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1547         return mpol_set_shared_policy(&SHMEM_I(i)->policy, vma, new);
1548 }
1549
1550 static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
1551                                           unsigned long addr)
1552 {
1553         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1554         unsigned long idx;
1555
1556         idx = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1557         return mpol_shared_policy_lookup(&SHMEM_I(i)->policy, idx);
1558 }
1559 #endif
1560
1561 int shmem_lock(struct file *file, int lock, struct user_struct *user)
1562 {
1563         struct inode *inode = file->f_path.dentry->d_inode;
1564         struct shmem_inode_info *info = SHMEM_I(inode);
1565         int retval = -ENOMEM;
1566
1567         spin_lock(&info->lock);
1568         if (lock && !(info->flags & VM_LOCKED)) {
1569                 if (!user_shm_lock(inode->i_size, user))
1570                         goto out_nomem;
1571                 info->flags |= VM_LOCKED;
1572                 mapping_set_unevictable(file->f_mapping);
1573         }
1574         if (!lock && (info->flags & VM_LOCKED) && user) {
1575                 user_shm_unlock(inode->i_size, user);
1576                 info->flags &= ~VM_LOCKED;
1577                 mapping_clear_unevictable(file->f_mapping);
1578                 scan_mapping_unevictable_pages(file->f_mapping);
1579         }
1580         retval = 0;
1581
1582 out_nomem:
1583         spin_unlock(&info->lock);
1584         return retval;
1585 }
1586
1587 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1588 {
1589         file_accessed(file);
1590         vma->vm_ops = &shmem_vm_ops;
1591         vma->vm_flags |= VM_CAN_NONLINEAR;
1592         return 0;
1593 }
1594
1595 static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir,
1596                                      int mode, dev_t dev, unsigned long flags)
1597 {
1598         struct inode *inode;
1599         struct shmem_inode_info *info;
1600         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1601
1602         if (shmem_reserve_inode(sb))
1603                 return NULL;
1604
1605         inode = new_inode(sb);
1606         if (inode) {
1607                 inode->i_ino = get_next_ino();
1608                 inode_init_owner(inode, dir, mode);
1609                 inode->i_blocks = 0;
1610                 inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1611                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1612                 inode->i_generation = get_seconds();
1613                 info = SHMEM_I(inode);
1614                 memset(info, 0, (char *)inode - (char *)info);
1615                 spin_lock_init(&info->lock);
1616                 info->flags = flags & VM_NORESERVE;
1617                 INIT_LIST_HEAD(&info->swaplist);
1618                 cache_no_acl(inode);
1619
1620                 switch (mode & S_IFMT) {
1621                 default:
1622                         inode->i_op = &shmem_special_inode_operations;
1623                         init_special_inode(inode, mode, dev);
1624                         break;
1625                 case S_IFREG:
1626                         inode->i_mapping->a_ops = &shmem_aops;
1627                         inode->i_op = &shmem_inode_operations;
1628                         inode->i_fop = &shmem_file_operations;
1629                         mpol_shared_policy_init(&info->policy,
1630                                                  shmem_get_sbmpol(sbinfo));
1631                         break;
1632                 case S_IFDIR:
1633                         inc_nlink(inode);
1634                         /* Some things misbehave if size == 0 on a directory */
1635                         inode->i_size = 2 * BOGO_DIRENT_SIZE;
1636                         inode->i_op = &shmem_dir_inode_operations;
1637                         inode->i_fop = &simple_dir_operations;
1638                         break;
1639                 case S_IFLNK:
1640                         /*
1641                          * Must not load anything in the rbtree,
1642                          * mpol_free_shared_policy will not be called.
1643                          */
1644                         mpol_shared_policy_init(&info->policy, NULL);
1645                         break;
1646                 }
1647         } else
1648                 shmem_free_inode(sb);
1649         return inode;
1650 }
1651
1652 #ifdef CONFIG_TMPFS
1653 static const struct inode_operations shmem_symlink_inode_operations;
1654 static const struct inode_operations shmem_symlink_inline_operations;
1655
1656 /*
1657  * Normally tmpfs avoids the use of shmem_readpage and shmem_write_begin;
1658  * but providing them allows a tmpfs file to be used for splice, sendfile, and
1659  * below the loop driver, in the generic fashion that many filesystems support.
1660  */
1661 static int shmem_readpage(struct file *file, struct page *page)
1662 {
1663         struct inode *inode = page->mapping->host;
1664         int error = shmem_getpage(inode, page->index, &page, SGP_CACHE, NULL);
1665         unlock_page(page);
1666         return error;
1667 }
1668
1669 static int
1670 shmem_write_begin(struct file *file, struct address_space *mapping,
1671                         loff_t pos, unsigned len, unsigned flags,
1672                         struct page **pagep, void **fsdata)
1673 {
1674         struct inode *inode = mapping->host;
1675         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1676         *pagep = NULL;
1677         return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
1678 }
1679
1680 static int
1681 shmem_write_end(struct file *file, struct address_space *mapping,
1682                         loff_t pos, unsigned len, unsigned copied,
1683                         struct page *page, void *fsdata)
1684 {
1685         struct inode *inode = mapping->host;
1686
1687         if (pos + copied > inode->i_size)
1688                 i_size_write(inode, pos + copied);
1689
1690         set_page_dirty(page);
1691         unlock_page(page);
1692         page_cache_release(page);
1693
1694         return copied;
1695 }
1696
1697 static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
1698 {
1699         struct inode *inode = filp->f_path.dentry->d_inode;
1700         struct address_space *mapping = inode->i_mapping;
1701         unsigned long index, offset;
1702         enum sgp_type sgp = SGP_READ;
1703
1704         /*
1705          * Might this read be for a stacking filesystem?  Then when reading
1706          * holes of a sparse file, we actually need to allocate those pages,
1707          * and even mark them dirty, so it cannot exceed the max_blocks limit.
1708          */
1709         if (segment_eq(get_fs(), KERNEL_DS))
1710                 sgp = SGP_DIRTY;
1711
1712         index = *ppos >> PAGE_CACHE_SHIFT;
1713         offset = *ppos & ~PAGE_CACHE_MASK;
1714
1715         for (;;) {
1716                 struct page *page = NULL;
1717                 unsigned long end_index, nr, ret;
1718                 loff_t i_size = i_size_read(inode);
1719
1720                 end_index = i_size >> PAGE_CACHE_SHIFT;
1721                 if (index > end_index)
1722                         break;
1723                 if (index == end_index) {
1724                         nr = i_size & ~PAGE_CACHE_MASK;
1725                         if (nr <= offset)
1726                                 break;
1727                 }
1728
1729                 desc->error = shmem_getpage(inode, index, &page, sgp, NULL);
1730                 if (desc->error) {
1731                         if (desc->error == -EINVAL)
1732                                 desc->error = 0;
1733                         break;
1734                 }
1735                 if (page)
1736                         unlock_page(page);
1737
1738                 /*
1739                  * We must evaluate after, since reads (unlike writes)
1740                  * are called without i_mutex protection against truncate
1741                  */
1742                 nr = PAGE_CACHE_SIZE;
1743                 i_size = i_size_read(inode);
1744                 end_index = i_size >> PAGE_CACHE_SHIFT;
1745                 if (index == end_index) {
1746                         nr = i_size & ~PAGE_CACHE_MASK;
1747                         if (nr <= offset) {
1748                                 if (page)
1749                                         page_cache_release(page);
1750                                 break;
1751                         }
1752                 }
1753                 nr -= offset;
1754
1755                 if (page) {
1756                         /*
1757                          * If users can be writing to this page using arbitrary
1758                          * virtual addresses, take care about potential aliasing
1759                          * before reading the page on the kernel side.
1760                          */
1761                         if (mapping_writably_mapped(mapping))
1762                                 flush_dcache_page(page);
1763                         /*
1764                          * Mark the page accessed if we read the beginning.
1765                          */
1766                         if (!offset)
1767                                 mark_page_accessed(page);
1768                 } else {
1769                         page = ZERO_PAGE(0);
1770                         page_cache_get(page);
1771                 }
1772
1773                 /*
1774                  * Ok, we have the page, and it's up-to-date, so
1775                  * now we can copy it to user space...
1776                  *
1777                  * The actor routine returns how many bytes were actually used..
1778                  * NOTE! This may not be the same as how much of a user buffer
1779                  * we filled up (we may be padding etc), so we can only update
1780                  * "pos" here (the actor routine has to update the user buffer
1781                  * pointers and the remaining count).
1782                  */
1783                 ret = actor(desc, page, offset, nr);
1784                 offset += ret;
1785                 index += offset >> PAGE_CACHE_SHIFT;
1786                 offset &= ~PAGE_CACHE_MASK;
1787
1788                 page_cache_release(page);
1789                 if (ret != nr || !desc->count)
1790                         break;
1791
1792                 cond_resched();
1793         }
1794
1795         *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1796         file_accessed(filp);
1797 }
1798
1799 static ssize_t shmem_file_aio_read(struct kiocb *iocb,
1800                 const struct iovec *iov, unsigned long nr_segs, loff_t pos)
1801 {
1802         struct file *filp = iocb->ki_filp;
1803         ssize_t retval;
1804         unsigned long seg;
1805         size_t count;
1806         loff_t *ppos = &iocb->ki_pos;
1807
1808         retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1809         if (retval)
1810                 return retval;
1811
1812         for (seg = 0; seg < nr_segs; seg++) {
1813                 read_descriptor_t desc;
1814
1815                 desc.written = 0;
1816                 desc.arg.buf = iov[seg].iov_base;
1817                 desc.count = iov[seg].iov_len;
1818                 if (desc.count == 0)
1819                         continue;
1820                 desc.error = 0;
1821                 do_shmem_file_read(filp, ppos, &desc, file_read_actor);
1822                 retval += desc.written;
1823                 if (desc.error) {
1824                         retval = retval ?: desc.error;
1825                         break;
1826                 }
1827                 if (desc.count > 0)
1828                         break;
1829         }
1830         return retval;
1831 }
1832
1833 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
1834 {
1835         struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
1836
1837         buf->f_type = TMPFS_MAGIC;
1838         buf->f_bsize = PAGE_CACHE_SIZE;
1839         buf->f_namelen = NAME_MAX;
1840         if (sbinfo->max_blocks) {
1841                 buf->f_blocks = sbinfo->max_blocks;
1842                 buf->f_bavail = buf->f_bfree =
1843                                 sbinfo->max_blocks - percpu_counter_sum(&sbinfo->used_blocks);
1844         }
1845         if (sbinfo->max_inodes) {
1846                 buf->f_files = sbinfo->max_inodes;
1847                 buf->f_ffree = sbinfo->free_inodes;
1848         }
1849         /* else leave those fields 0 like simple_statfs */
1850         return 0;
1851 }
1852
1853 /*
1854  * File creation. Allocate an inode, and we're done..
1855  */
1856 static int
1857 shmem_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
1858 {
1859         struct inode *inode;
1860         int error = -ENOSPC;
1861
1862         inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
1863         if (inode) {
1864                 error = security_inode_init_security(inode, dir,
1865                                                      &dentry->d_name, NULL,
1866                                                      NULL, NULL);
1867                 if (error) {
1868                         if (error != -EOPNOTSUPP) {
1869                                 iput(inode);
1870                                 return error;
1871                         }
1872                 }
1873 #ifdef CONFIG_TMPFS_POSIX_ACL
1874                 error = generic_acl_init(inode, dir);
1875                 if (error) {
1876                         iput(inode);
1877                         return error;
1878                 }
1879 #else
1880                 error = 0;
1881 #endif
1882                 dir->i_size += BOGO_DIRENT_SIZE;
1883                 dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1884                 d_instantiate(dentry, inode);
1885                 dget(dentry); /* Extra count - pin the dentry in core */
1886         }
1887         return error;
1888 }
1889
1890 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, int mode)
1891 {
1892         int error;
1893
1894         if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
1895                 return error;
1896         inc_nlink(dir);
1897         return 0;
1898 }
1899
1900 static int shmem_create(struct inode *dir, struct dentry *dentry, int mode,
1901                 struct nameidata *nd)
1902 {
1903         return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
1904 }
1905
1906 /*
1907  * Link a file..
1908  */
1909 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
1910 {
1911         struct inode *inode = old_dentry->d_inode;
1912         int ret;
1913
1914         /*
1915          * No ordinary (disk based) filesystem counts links as inodes;
1916          * but each new link needs a new dentry, pinning lowmem, and
1917          * tmpfs dentries cannot be pruned until they are unlinked.
1918          */
1919         ret = shmem_reserve_inode(inode->i_sb);
1920         if (ret)
1921                 goto out;
1922
1923         dir->i_size += BOGO_DIRENT_SIZE;
1924         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1925         inc_nlink(inode);
1926         ihold(inode);   /* New dentry reference */
1927         dget(dentry);           /* Extra pinning count for the created dentry */
1928         d_instantiate(dentry, inode);
1929 out:
1930         return ret;
1931 }
1932
1933 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
1934 {
1935         struct inode *inode = dentry->d_inode;
1936
1937         if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
1938                 shmem_free_inode(inode->i_sb);
1939
1940         dir->i_size -= BOGO_DIRENT_SIZE;
1941         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1942         drop_nlink(inode);
1943         dput(dentry);   /* Undo the count from "create" - this does all the work */
1944         return 0;
1945 }
1946
1947 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
1948 {
1949         if (!simple_empty(dentry))
1950                 return -ENOTEMPTY;
1951
1952         drop_nlink(dentry->d_inode);
1953         drop_nlink(dir);
1954         return shmem_unlink(dir, dentry);
1955 }
1956
1957 /*
1958  * The VFS layer already does all the dentry stuff for rename,
1959  * we just have to decrement the usage count for the target if
1960  * it exists so that the VFS layer correctly free's it when it
1961  * gets overwritten.
1962  */
1963 static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
1964 {
1965         struct inode *inode = old_dentry->d_inode;
1966         int they_are_dirs = S_ISDIR(inode->i_mode);
1967
1968         if (!simple_empty(new_dentry))
1969                 return -ENOTEMPTY;
1970
1971         if (new_dentry->d_inode) {
1972                 (void) shmem_unlink(new_dir, new_dentry);
1973                 if (they_are_dirs)
1974                         drop_nlink(old_dir);
1975         } else if (they_are_dirs) {
1976                 drop_nlink(old_dir);
1977                 inc_nlink(new_dir);
1978         }
1979
1980         old_dir->i_size -= BOGO_DIRENT_SIZE;
1981         new_dir->i_size += BOGO_DIRENT_SIZE;
1982         old_dir->i_ctime = old_dir->i_mtime =
1983         new_dir->i_ctime = new_dir->i_mtime =
1984         inode->i_ctime = CURRENT_TIME;
1985         return 0;
1986 }
1987
1988 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
1989 {
1990         int error;
1991         int len;
1992         struct inode *inode;
1993         struct page *page = NULL;
1994         char *kaddr;
1995         struct shmem_inode_info *info;
1996
1997         len = strlen(symname) + 1;
1998         if (len > PAGE_CACHE_SIZE)
1999                 return -ENAMETOOLONG;
2000
2001         inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0, VM_NORESERVE);
2002         if (!inode)
2003                 return -ENOSPC;
2004
2005         error = security_inode_init_security(inode, dir, &dentry->d_name, NULL,
2006                                              NULL, NULL);
2007         if (error) {
2008                 if (error != -EOPNOTSUPP) {
2009                         iput(inode);
2010                         return error;
2011                 }
2012                 error = 0;
2013         }
2014
2015         info = SHMEM_I(inode);
2016         inode->i_size = len-1;
2017         if (len <= (char *)inode - (char *)info) {
2018                 /* do it inline */
2019                 memcpy(info, symname, len);
2020                 inode->i_op = &shmem_symlink_inline_operations;
2021         } else {
2022                 error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
2023                 if (error) {
2024                         iput(inode);
2025                         return error;
2026                 }
2027                 inode->i_mapping->a_ops = &shmem_aops;
2028                 inode->i_op = &shmem_symlink_inode_operations;
2029                 kaddr = kmap_atomic(page, KM_USER0);
2030                 memcpy(kaddr, symname, len);
2031                 kunmap_atomic(kaddr, KM_USER0);
2032                 set_page_dirty(page);
2033                 unlock_page(page);
2034                 page_cache_release(page);
2035         }
2036         dir->i_size += BOGO_DIRENT_SIZE;
2037         dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2038         d_instantiate(dentry, inode);
2039         dget(dentry);
2040         return 0;
2041 }
2042
2043 static void *shmem_follow_link_inline(struct dentry *dentry, struct nameidata *nd)
2044 {
2045         nd_set_link(nd, (char *)SHMEM_I(dentry->d_inode));
2046         return NULL;
2047 }
2048
2049 static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
2050 {
2051         struct page *page = NULL;
2052         int res = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
2053         nd_set_link(nd, res ? ERR_PTR(res) : kmap(page));
2054         if (page)
2055                 unlock_page(page);
2056         return page;
2057 }
2058
2059 static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
2060 {
2061         if (!IS_ERR(nd_get_link(nd))) {
2062                 struct page *page = cookie;
2063                 kunmap(page);
2064                 mark_page_accessed(page);
2065                 page_cache_release(page);
2066         }
2067 }
2068
2069 static const struct inode_operations shmem_symlink_inline_operations = {
2070         .readlink       = generic_readlink,
2071         .follow_link    = shmem_follow_link_inline,
2072 };
2073
2074 static const struct inode_operations shmem_symlink_inode_operations = {
2075         .readlink       = generic_readlink,
2076         .follow_link    = shmem_follow_link,
2077         .put_link       = shmem_put_link,
2078 };
2079
2080 #ifdef CONFIG_TMPFS_POSIX_ACL
2081 /*
2082  * Superblocks without xattr inode operations will get security.* xattr
2083  * support from the VFS "for free". As soon as we have any other xattrs
2084  * like ACLs, we also need to implement the security.* handlers at
2085  * filesystem level, though.
2086  */
2087
2088 static size_t shmem_xattr_security_list(struct dentry *dentry, char *list,
2089                                         size_t list_len, const char *name,
2090                                         size_t name_len, int handler_flags)
2091 {
2092         return security_inode_listsecurity(dentry->d_inode, list, list_len);
2093 }
2094
2095 static int shmem_xattr_security_get(struct dentry *dentry, const char *name,
2096                 void *buffer, size_t size, int handler_flags)
2097 {
2098         if (strcmp(name, "") == 0)
2099                 return -EINVAL;
2100         return xattr_getsecurity(dentry->d_inode, name, buffer, size);
2101 }
2102
2103 static int shmem_xattr_security_set(struct dentry *dentry, const char *name,
2104                 const void *value, size_t size, int flags, int handler_flags)
2105 {
2106         if (strcmp(name, "") == 0)
2107                 return -EINVAL;
2108         return security_inode_setsecurity(dentry->d_inode, name, value,
2109                                           size, flags);
2110 }
2111
2112 static const struct xattr_handler shmem_xattr_security_handler = {
2113         .prefix = XATTR_SECURITY_PREFIX,
2114         .list   = shmem_xattr_security_list,
2115         .get    = shmem_xattr_security_get,
2116         .set    = shmem_xattr_security_set,
2117 };
2118
2119 static const struct xattr_handler *shmem_xattr_handlers[] = {
2120         &generic_acl_access_handler,
2121         &generic_acl_default_handler,
2122         &shmem_xattr_security_handler,
2123         NULL
2124 };
2125 #endif
2126
2127 static struct dentry *shmem_get_parent(struct dentry *child)
2128 {
2129         return ERR_PTR(-ESTALE);
2130 }
2131
2132 static int shmem_match(struct inode *ino, void *vfh)
2133 {
2134         __u32 *fh = vfh;
2135         __u64 inum = fh[2];
2136         inum = (inum << 32) | fh[1];
2137         return ino->i_ino == inum && fh[0] == ino->i_generation;
2138 }
2139
2140 static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
2141                 struct fid *fid, int fh_len, int fh_type)
2142 {
2143         struct inode *inode;
2144         struct dentry *dentry = NULL;
2145         u64 inum = fid->raw[2];
2146         inum = (inum << 32) | fid->raw[1];
2147
2148         if (fh_len < 3)
2149                 return NULL;
2150
2151         inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
2152                         shmem_match, fid->raw);
2153         if (inode) {
2154                 dentry = d_find_alias(inode);
2155                 iput(inode);
2156         }
2157
2158         return dentry;
2159 }
2160
2161 static int shmem_encode_fh(struct dentry *dentry, __u32 *fh, int *len,
2162                                 int connectable)
2163 {
2164         struct inode *inode = dentry->d_inode;
2165
2166         if (*len < 3) {
2167                 *len = 3;
2168                 return 255;
2169         }
2170
2171         if (inode_unhashed(inode)) {
2172                 /* Unfortunately insert_inode_hash is not idempotent,
2173                  * so as we hash inodes here rather than at creation
2174                  * time, we need a lock to ensure we only try
2175                  * to do it once
2176                  */
2177                 static DEFINE_SPINLOCK(lock);
2178                 spin_lock(&lock);
2179                 if (inode_unhashed(inode))
2180                         __insert_inode_hash(inode,
2181                                             inode->i_ino + inode->i_generation);
2182                 spin_unlock(&lock);
2183         }
2184
2185         fh[0] = inode->i_generation;
2186         fh[1] = inode->i_ino;
2187         fh[2] = ((__u64)inode->i_ino) >> 32;
2188
2189         *len = 3;
2190         return 1;
2191 }
2192
2193 static const struct export_operations shmem_export_ops = {
2194         .get_parent     = shmem_get_parent,
2195         .encode_fh      = shmem_encode_fh,
2196         .fh_to_dentry   = shmem_fh_to_dentry,
2197 };
2198
2199 static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
2200                                bool remount)
2201 {
2202         char *this_char, *value, *rest;
2203
2204         while (options != NULL) {
2205                 this_char = options;
2206                 for (;;) {
2207                         /*
2208                          * NUL-terminate this option: unfortunately,
2209                          * mount options form a comma-separated list,
2210                          * but mpol's nodelist may also contain commas.
2211                          */
2212                         options = strchr(options, ',');
2213                         if (options == NULL)
2214                                 break;
2215                         options++;
2216                         if (!isdigit(*options)) {
2217                                 options[-1] = '\0';
2218                                 break;
2219                         }
2220                 }
2221                 if (!*this_char)
2222                         continue;
2223                 if ((value = strchr(this_char,'=')) != NULL) {
2224                         *value++ = 0;
2225                 } else {
2226                         printk(KERN_ERR
2227                             "tmpfs: No value for mount option '%s'\n",
2228                             this_char);
2229                         return 1;
2230                 }
2231
2232                 if (!strcmp(this_char,"size")) {
2233                         unsigned long long size;
2234                         size = memparse(value,&rest);
2235                         if (*rest == '%') {
2236                                 size <<= PAGE_SHIFT;
2237                                 size *= totalram_pages;
2238                                 do_div(size, 100);
2239                                 rest++;
2240                         }
2241                         if (*rest)
2242                                 goto bad_val;
2243                         sbinfo->max_blocks =
2244                                 DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
2245                 } else if (!strcmp(this_char,"nr_blocks")) {
2246                         sbinfo->max_blocks = memparse(value, &rest);
2247                         if (*rest)
2248                                 goto bad_val;
2249                 } else if (!strcmp(this_char,"nr_inodes")) {
2250                         sbinfo->max_inodes = memparse(value, &rest);
2251                         if (*rest)
2252                                 goto bad_val;
2253                 } else if (!strcmp(this_char,"mode")) {
2254                         if (remount)
2255                                 continue;
2256                         sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
2257                         if (*rest)
2258                                 goto bad_val;
2259                 } else if (!strcmp(this_char,"uid")) {
2260                         if (remount)
2261                                 continue;
2262                         sbinfo->uid = simple_strtoul(value, &rest, 0);
2263                         if (*rest)
2264                                 goto bad_val;
2265                 } else if (!strcmp(this_char,"gid")) {
2266                         if (remount)
2267                                 continue;
2268                         sbinfo->gid = simple_strtoul(value, &rest, 0);
2269                         if (*rest)
2270                                 goto bad_val;
2271                 } else if (!strcmp(this_char,"mpol")) {
2272                         if (mpol_parse_str(value, &sbinfo->mpol, 1))
2273                                 goto bad_val;
2274                 } else {
2275                         printk(KERN_ERR "tmpfs: Bad mount option %s\n",
2276                                this_char);
2277                         return 1;
2278                 }
2279         }
2280         return 0;
2281
2282 bad_val:
2283         printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
2284                value, this_char);
2285         return 1;
2286
2287 }
2288
2289 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2290 {
2291         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2292         struct shmem_sb_info config = *sbinfo;
2293         unsigned long inodes;
2294         int error = -EINVAL;
2295
2296         if (shmem_parse_options(data, &config, true))
2297                 return error;
2298
2299         spin_lock(&sbinfo->stat_lock);
2300         inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2301         if (percpu_counter_compare(&sbinfo->used_blocks, config.max_blocks) > 0)
2302                 goto out;
2303         if (config.max_inodes < inodes)
2304                 goto out;
2305         /*
2306          * Those tests also disallow limited->unlimited while any are in
2307          * use, so i_blocks will always be zero when max_blocks is zero;
2308          * but we must separately disallow unlimited->limited, because
2309          * in that case we have no record of how much is already in use.
2310          */
2311         if (config.max_blocks && !sbinfo->max_blocks)
2312                 goto out;
2313         if (config.max_inodes && !sbinfo->max_inodes)
2314                 goto out;
2315
2316         error = 0;
2317         sbinfo->max_blocks  = config.max_blocks;
2318         sbinfo->max_inodes  = config.max_inodes;
2319         sbinfo->free_inodes = config.max_inodes - inodes;
2320
2321         mpol_put(sbinfo->mpol);
2322         sbinfo->mpol        = config.mpol;      /* transfers initial ref */
2323 out:
2324         spin_unlock(&sbinfo->stat_lock);
2325         return error;
2326 }
2327
2328 static int shmem_show_options(struct seq_file *seq, struct vfsmount *vfs)
2329 {
2330         struct shmem_sb_info *sbinfo = SHMEM_SB(vfs->mnt_sb);
2331
2332         if (sbinfo->max_blocks != shmem_default_max_blocks())
2333                 seq_printf(seq, ",size=%luk",
2334                         sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10));
2335         if (sbinfo->max_inodes != shmem_default_max_inodes())
2336                 seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
2337         if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
2338                 seq_printf(seq, ",mode=%03o", sbinfo->mode);
2339         if (sbinfo->uid != 0)
2340                 seq_printf(seq, ",uid=%u", sbinfo->uid);
2341         if (sbinfo->gid != 0)
2342                 seq_printf(seq, ",gid=%u", sbinfo->gid);
2343         shmem_show_mpol(seq, sbinfo->mpol);
2344         return 0;
2345 }
2346 #endif /* CONFIG_TMPFS */
2347
2348 static void shmem_put_super(struct super_block *sb)
2349 {
2350         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2351
2352         percpu_counter_destroy(&sbinfo->used_blocks);
2353         kfree(sbinfo);
2354         sb->s_fs_info = NULL;
2355 }
2356
2357 int shmem_fill_super(struct super_block *sb, void *data, int silent)
2358 {
2359         struct inode *inode;
2360         struct dentry *root;
2361         struct shmem_sb_info *sbinfo;
2362         int err = -ENOMEM;
2363
2364         /* Round up to L1_CACHE_BYTES to resist false sharing */
2365         sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
2366                                 L1_CACHE_BYTES), GFP_KERNEL);
2367         if (!sbinfo)
2368                 return -ENOMEM;
2369
2370         sbinfo->mode = S_IRWXUGO | S_ISVTX;
2371         sbinfo->uid = current_fsuid();
2372         sbinfo->gid = current_fsgid();
2373         sb->s_fs_info = sbinfo;
2374
2375 #ifdef CONFIG_TMPFS
2376         /*
2377          * Per default we only allow half of the physical ram per
2378          * tmpfs instance, limiting inodes to one per page of lowmem;
2379          * but the internal instance is left unlimited.
2380          */
2381         if (!(sb->s_flags & MS_NOUSER)) {
2382                 sbinfo->max_blocks = shmem_default_max_blocks();
2383                 sbinfo->max_inodes = shmem_default_max_inodes();
2384                 if (shmem_parse_options(data, sbinfo, false)) {
2385                         err = -EINVAL;
2386                         goto failed;
2387                 }
2388         }
2389         sb->s_export_op = &shmem_export_ops;
2390 #else
2391         sb->s_flags |= MS_NOUSER;
2392 #endif
2393
2394         spin_lock_init(&sbinfo->stat_lock);
2395         if (percpu_counter_init(&sbinfo->used_blocks, 0))
2396                 goto failed;
2397         sbinfo->free_inodes = sbinfo->max_inodes;
2398
2399         sb->s_maxbytes = SHMEM_MAX_BYTES;
2400         sb->s_blocksize = PAGE_CACHE_SIZE;
2401         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
2402         sb->s_magic = TMPFS_MAGIC;
2403         sb->s_op = &shmem_ops;
2404         sb->s_time_gran = 1;
2405 #ifdef CONFIG_TMPFS_POSIX_ACL
2406         sb->s_xattr = shmem_xattr_handlers;
2407         sb->s_flags |= MS_POSIXACL;
2408 #endif
2409
2410         inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
2411         if (!inode)
2412                 goto failed;
2413         inode->i_uid = sbinfo->uid;
2414         inode->i_gid = sbinfo->gid;
2415         root = d_alloc_root(inode);
2416         if (!root)
2417                 goto failed_iput;
2418         sb->s_root = root;
2419         return 0;
2420
2421 failed_iput:
2422         iput(inode);
2423 failed:
2424         shmem_put_super(sb);
2425         return err;
2426 }
2427
2428 static struct kmem_cache *shmem_inode_cachep;
2429
2430 static struct inode *shmem_alloc_inode(struct super_block *sb)
2431 {
2432         struct shmem_inode_info *p;
2433         p = (struct shmem_inode_info *)kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
2434         if (!p)
2435                 return NULL;
2436         return &p->vfs_inode;
2437 }
2438
2439 static void shmem_i_callback(struct rcu_head *head)
2440 {
2441         struct inode *inode = container_of(head, struct inode, i_rcu);
2442         INIT_LIST_HEAD(&inode->i_dentry);
2443         kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2444 }
2445
2446 static void shmem_destroy_inode(struct inode *inode)
2447 {
2448         if ((inode->i_mode & S_IFMT) == S_IFREG) {
2449                 /* only struct inode is valid if it's an inline symlink */
2450                 mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2451         }
2452         call_rcu(&inode->i_rcu, shmem_i_callback);
2453 }
2454
2455 static void init_once(void *foo)
2456 {
2457         struct shmem_inode_info *p = (struct shmem_inode_info *) foo;
2458
2459         inode_init_once(&p->vfs_inode);
2460 }
2461
2462 static int init_inodecache(void)
2463 {
2464         shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
2465                                 sizeof(struct shmem_inode_info),
2466                                 0, SLAB_PANIC, init_once);
2467         return 0;
2468 }
2469
2470 static void destroy_inodecache(void)
2471 {
2472         kmem_cache_destroy(shmem_inode_cachep);
2473 }
2474
2475 static const struct address_space_operations shmem_aops = {
2476         .writepage      = shmem_writepage,
2477         .set_page_dirty = __set_page_dirty_no_writeback,
2478 #ifdef CONFIG_TMPFS
2479         .readpage       = shmem_readpage,
2480         .write_begin    = shmem_write_begin,
2481         .write_end      = shmem_write_end,
2482 #endif
2483         .migratepage    = migrate_page,
2484         .error_remove_page = generic_error_remove_page,
2485 };
2486
2487 static const struct file_operations shmem_file_operations = {
2488         .mmap           = shmem_mmap,
2489 #ifdef CONFIG_TMPFS
2490         .llseek         = generic_file_llseek,
2491         .read           = do_sync_read,
2492         .write          = do_sync_write,
2493         .aio_read       = shmem_file_aio_read,
2494         .aio_write      = generic_file_aio_write,
2495         .fsync          = noop_fsync,
2496         .splice_read    = generic_file_splice_read,
2497         .splice_write   = generic_file_splice_write,
2498 #endif
2499 };
2500
2501 static const struct inode_operations shmem_inode_operations = {
2502         .setattr        = shmem_notify_change,
2503         .truncate_range = shmem_truncate_range,
2504 #ifdef CONFIG_TMPFS_POSIX_ACL
2505         .setxattr       = generic_setxattr,
2506         .getxattr       = generic_getxattr,
2507         .listxattr      = generic_listxattr,
2508         .removexattr    = generic_removexattr,
2509         .check_acl      = generic_check_acl,
2510 #endif
2511
2512 };
2513
2514 static const struct inode_operations shmem_dir_inode_operations = {
2515 #ifdef CONFIG_TMPFS
2516         .create         = shmem_create,
2517         .lookup         = simple_lookup,
2518         .link           = shmem_link,
2519         .unlink         = shmem_unlink,
2520         .symlink        = shmem_symlink,
2521         .mkdir          = shmem_mkdir,
2522         .rmdir          = shmem_rmdir,
2523         .mknod          = shmem_mknod,
2524         .rename         = shmem_rename,
2525 #endif
2526 #ifdef CONFIG_TMPFS_POSIX_ACL
2527         .setattr        = shmem_notify_change,
2528         .setxattr       = generic_setxattr,
2529         .getxattr       = generic_getxattr,
2530         .listxattr      = generic_listxattr,
2531         .removexattr    = generic_removexattr,
2532         .check_acl      = generic_check_acl,
2533 #endif
2534 };
2535
2536 static const struct inode_operations shmem_special_inode_operations = {
2537 #ifdef CONFIG_TMPFS_POSIX_ACL
2538         .setattr        = shmem_notify_change,
2539         .setxattr       = generic_setxattr,
2540         .getxattr       = generic_getxattr,
2541         .listxattr      = generic_listxattr,
2542         .removexattr    = generic_removexattr,
2543         .check_acl      = generic_check_acl,
2544 #endif
2545 };
2546
2547 static const struct super_operations shmem_ops = {
2548         .alloc_inode    = shmem_alloc_inode,
2549         .destroy_inode  = shmem_destroy_inode,
2550 #ifdef CONFIG_TMPFS
2551         .statfs         = shmem_statfs,
2552         .remount_fs     = shmem_remount_fs,
2553         .show_options   = shmem_show_options,
2554 #endif
2555         .evict_inode    = shmem_evict_inode,
2556         .drop_inode     = generic_delete_inode,
2557         .put_super      = shmem_put_super,
2558 };
2559
2560 static const struct vm_operations_struct shmem_vm_ops = {
2561         .fault          = shmem_fault,
2562 #ifdef CONFIG_NUMA
2563         .set_policy     = shmem_set_policy,
2564         .get_policy     = shmem_get_policy,
2565 #endif
2566 };
2567
2568
2569 static struct dentry *shmem_mount(struct file_system_type *fs_type,
2570         int flags, const char *dev_name, void *data)
2571 {
2572         return mount_nodev(fs_type, flags, data, shmem_fill_super);
2573 }
2574
2575 static struct file_system_type tmpfs_fs_type = {
2576         .owner          = THIS_MODULE,
2577         .name           = "tmpfs",
2578         .mount          = shmem_mount,
2579         .kill_sb        = kill_litter_super,
2580 };
2581
2582 int __init init_tmpfs(void)
2583 {
2584         int error;
2585
2586         error = bdi_init(&shmem_backing_dev_info);
2587         if (error)
2588                 goto out4;
2589
2590         error = init_inodecache();
2591         if (error)
2592                 goto out3;
2593
2594         error = register_filesystem(&tmpfs_fs_type);
2595         if (error) {
2596                 printk(KERN_ERR "Could not register tmpfs\n");
2597                 goto out2;
2598         }
2599
2600         shm_mnt = vfs_kern_mount(&tmpfs_fs_type, MS_NOUSER,
2601                                 tmpfs_fs_type.name, NULL);
2602         if (IS_ERR(shm_mnt)) {
2603                 error = PTR_ERR(shm_mnt);
2604                 printk(KERN_ERR "Could not kern_mount tmpfs\n");
2605                 goto out1;
2606         }
2607         return 0;
2608
2609 out1:
2610         unregister_filesystem(&tmpfs_fs_type);
2611 out2:
2612         destroy_inodecache();
2613 out3:
2614         bdi_destroy(&shmem_backing_dev_info);
2615 out4:
2616         shm_mnt = ERR_PTR(error);
2617         return error;
2618 }
2619
2620 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2621 /**
2622  * mem_cgroup_get_shmem_target - find a page or entry assigned to the shmem file
2623  * @inode: the inode to be searched
2624  * @pgoff: the offset to be searched
2625  * @pagep: the pointer for the found page to be stored
2626  * @ent: the pointer for the found swap entry to be stored
2627  *
2628  * If a page is found, refcount of it is incremented. Callers should handle
2629  * these refcount.
2630  */
2631 void mem_cgroup_get_shmem_target(struct inode *inode, pgoff_t pgoff,
2632                                         struct page **pagep, swp_entry_t *ent)
2633 {
2634         swp_entry_t entry = { .val = 0 }, *ptr;
2635         struct page *page = NULL;
2636         struct shmem_inode_info *info = SHMEM_I(inode);
2637
2638         if ((pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
2639                 goto out;
2640
2641         spin_lock(&info->lock);
2642         ptr = shmem_swp_entry(info, pgoff, NULL);
2643 #ifdef CONFIG_SWAP
2644         if (ptr && ptr->val) {
2645                 entry.val = ptr->val;
2646                 page = find_get_page(&swapper_space, entry.val);
2647         } else
2648 #endif
2649                 page = find_get_page(inode->i_mapping, pgoff);
2650         if (ptr)
2651                 shmem_swp_unmap(ptr);
2652         spin_unlock(&info->lock);
2653 out:
2654         *pagep = page;
2655         *ent = entry;
2656 }
2657 #endif
2658
2659 #else /* !CONFIG_SHMEM */
2660
2661 /*
2662  * tiny-shmem: simple shmemfs and tmpfs using ramfs code
2663  *
2664  * This is intended for small system where the benefits of the full
2665  * shmem code (swap-backed and resource-limited) are outweighed by
2666  * their complexity. On systems without swap this code should be
2667  * effectively equivalent, but much lighter weight.
2668  */
2669
2670 #include <linux/ramfs.h>
2671
2672 static struct file_system_type tmpfs_fs_type = {
2673         .name           = "tmpfs",
2674         .mount          = ramfs_mount,
2675         .kill_sb        = kill_litter_super,
2676 };
2677
2678 int __init init_tmpfs(void)
2679 {
2680         BUG_ON(register_filesystem(&tmpfs_fs_type) != 0);
2681
2682         shm_mnt = kern_mount(&tmpfs_fs_type);
2683         BUG_ON(IS_ERR(shm_mnt));
2684
2685         return 0;
2686 }
2687
2688 int shmem_unuse(swp_entry_t entry, struct page *page)
2689 {
2690         return 0;
2691 }
2692
2693 int shmem_lock(struct file *file, int lock, struct user_struct *user)
2694 {
2695         return 0;
2696 }
2697
2698 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2699 /**
2700  * mem_cgroup_get_shmem_target - find a page or entry assigned to the shmem file
2701  * @inode: the inode to be searched
2702  * @pgoff: the offset to be searched
2703  * @pagep: the pointer for the found page to be stored
2704  * @ent: the pointer for the found swap entry to be stored
2705  *
2706  * If a page is found, refcount of it is incremented. Callers should handle
2707  * these refcount.
2708  */
2709 void mem_cgroup_get_shmem_target(struct inode *inode, pgoff_t pgoff,
2710                                         struct page **pagep, swp_entry_t *ent)
2711 {
2712         struct page *page = NULL;
2713
2714         if ((pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
2715                 goto out;
2716         page = find_get_page(inode->i_mapping, pgoff);
2717 out:
2718         *pagep = page;
2719         *ent = (swp_entry_t){ .val = 0 };
2720 }
2721 #endif
2722
2723 #define shmem_vm_ops                            generic_file_vm_ops
2724 #define shmem_file_operations                   ramfs_file_operations
2725 #define shmem_get_inode(sb, dir, mode, dev, flags)      ramfs_get_inode(sb, dir, mode, dev)
2726 #define shmem_acct_size(flags, size)            0
2727 #define shmem_unacct_size(flags, size)          do {} while (0)
2728 #define SHMEM_MAX_BYTES                         MAX_LFS_FILESIZE
2729
2730 #endif /* CONFIG_SHMEM */
2731
2732 /* common code */
2733
2734 /**
2735  * shmem_file_setup - get an unlinked file living in tmpfs
2736  * @name: name for dentry (to be seen in /proc/<pid>/maps
2737  * @size: size to be set for the file
2738  * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
2739  */
2740 struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
2741 {
2742         int error;
2743         struct file *file;
2744         struct inode *inode;
2745         struct path path;
2746         struct dentry *root;
2747         struct qstr this;
2748
2749         if (IS_ERR(shm_mnt))
2750                 return (void *)shm_mnt;
2751
2752         if (size < 0 || size > SHMEM_MAX_BYTES)
2753                 return ERR_PTR(-EINVAL);
2754
2755         if (shmem_acct_size(flags, size))
2756                 return ERR_PTR(-ENOMEM);
2757
2758         error = -ENOMEM;
2759         this.name = name;
2760         this.len = strlen(name);
2761         this.hash = 0; /* will go */
2762         root = shm_mnt->mnt_root;
2763         path.dentry = d_alloc(root, &this);
2764         if (!path.dentry)
2765                 goto put_memory;
2766         path.mnt = mntget(shm_mnt);
2767
2768         error = -ENOSPC;
2769         inode = shmem_get_inode(root->d_sb, NULL, S_IFREG | S_IRWXUGO, 0, flags);
2770         if (!inode)
2771                 goto put_dentry;
2772
2773         d_instantiate(path.dentry, inode);
2774         inode->i_size = size;
2775         inode->i_nlink = 0;     /* It is unlinked */
2776 #ifndef CONFIG_MMU
2777         error = ramfs_nommu_expand_for_mapping(inode, size);
2778         if (error)
2779                 goto put_dentry;
2780 #endif
2781
2782         error = -ENFILE;
2783         file = alloc_file(&path, FMODE_WRITE | FMODE_READ,
2784                   &shmem_file_operations);
2785         if (!file)
2786                 goto put_dentry;
2787
2788         return file;
2789
2790 put_dentry:
2791         path_put(&path);
2792 put_memory:
2793         shmem_unacct_size(flags, size);
2794         return ERR_PTR(error);
2795 }
2796 EXPORT_SYMBOL_GPL(shmem_file_setup);
2797
2798 /**
2799  * shmem_zero_setup - setup a shared anonymous mapping
2800  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
2801  */
2802 int shmem_zero_setup(struct vm_area_struct *vma)
2803 {
2804         struct file *file;
2805         loff_t size = vma->vm_end - vma->vm_start;
2806
2807         file = shmem_file_setup("dev/zero", size, vma->vm_flags);
2808         if (IS_ERR(file))
2809                 return PTR_ERR(file);
2810
2811         if (vma->vm_file)
2812                 fput(vma->vm_file);
2813         vma->vm_file = file;
2814         vma->vm_ops = &shmem_vm_ops;
2815         vma->vm_flags |= VM_CAN_NONLINEAR;
2816         return 0;
2817 }