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