mm/shmem.c

   1 /*
   2  * Resizable virtual memory filesystem for Linux.
   3  *
   4  * Copyright (C) 2000 Linus Torvalds.
   5  *               2000 Transmeta Corp.
   6  *               2000-2001 Christoph Rohland
   7  *               2000-2001 SAP AG
   8  *               2002 Red Hat Inc.
   9  * Copyright (C) 2002-2005 Hugh Dickins.
  10  * Copyright (C) 2002-2005 VERITAS Software Corporation.
  11  * Copyright (C) 2004 Andi Kleen, SuSE Labs
  12  *
  13  * Extended attribute support for tmpfs:
  14  * Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@lkcl.net>
  15  * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
  16  *
  17  * This file is released under the GPL.
  18  */
  19
  20 /*
  21  * This virtual memory filesystem is heavily based on the ramfs. It
  22  * extends ramfs by the ability to use swap and honor resource limits
  23  * which makes it a completely usable filesystem.
  24  */
  25
  26 #include <linux/module.h>
  27 #include <linux/init.h>
  28 #include <linux/fs.h>
  29 #include <linux/xattr.h>
  30 #include <linux/exportfs.h>
  31 #include <linux/generic_acl.h>
  32 #include <linux/mm.h>
  33 #include <linux/mman.h>
  34 #include <linux/file.h>
  35 #include <linux/swap.h>
  36 #include <linux/pagemap.h>
  37 #include <linux/string.h>
  38 #include <linux/slab.h>
  39 #include <linux/backing-dev.h>
  40 #include <linux/shmem_fs.h>
  41 #include <linux/mount.h>
  42 #include <linux/writeback.h>
  43 #include <linux/vfs.h>
  44 #include <linux/blkdev.h>
  45 #include <linux/security.h>
  46 #include <linux/swapops.h>
  47 #include <linux/mempolicy.h>
  48 #include <linux/namei.h>
  49 #include <linux/ctype.h>
  50 #include <linux/migrate.h>
  51 #include <linux/highmem.h>
  52 #include <linux/seq_file.h>
  53
  54 #include <asm/uaccess.h>
  55 #include <asm/div64.h>
  56 #include <asm/pgtable.h>
  57
  58 /* This magic number is used in glibc for posix shared memory */
  59 #define TMPFS_MAGIC     0x01021994
  60
  61 #define ENTRIES_PER_PAGE (PAGE_CACHE_SIZE/sizeof(unsigned long))
  62 #define ENTRIES_PER_PAGEPAGE (ENTRIES_PER_PAGE*ENTRIES_PER_PAGE)
  63 #define BLOCKS_PER_PAGE  (PAGE_CACHE_SIZE/512)
  64
  65 #define SHMEM_MAX_INDEX  (SHMEM_NR_DIRECT + (ENTRIES_PER_PAGEPAGE/2) * (ENTRIES_PER_PAGE+1))
  66 #define SHMEM_MAX_BYTES  ((unsigned long long)SHMEM_MAX_INDEX << PAGE_CACHE_SHIFT)
  67
  68 #define VM_ACCT(size)    (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
  69
  70 /* info->flags needs VM_flags to handle pagein/truncate races efficiently */
  71 #define SHMEM_PAGEIN     VM_READ
  72 #define SHMEM_TRUNCATE   VM_WRITE
  73
  74 /* Definition to limit shmem_truncate's steps between cond_rescheds */
  75 #define LATENCY_LIMIT    64
  76
  77 /* Pretend that each entry is of this size in directory's i_size */
  78 #define BOGO_DIRENT_SIZE 20
  79
  80 /* Flag allocation requirements to shmem_getpage and shmem_swp_alloc */
  81 enum sgp_type {
  82         SGP_READ,       /* don't exceed i_size, don't allocate page */
  83         SGP_CACHE,      /* don't exceed i_size, may allocate page */
  84         SGP_DIRTY,      /* like SGP_CACHE, but set new page dirty */
  85         SGP_WRITE,      /* may exceed i_size, may allocate page */
  86 };
  87
  88 #ifdef CONFIG_TMPFS
  89 static unsigned long shmem_default_max_blocks(void)
  90 {
  91         return totalram_pages / 2;
  92 }
  93
  94 static unsigned long shmem_default_max_inodes(void)
  95 {
  96         return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
  97 }
  98 #endif
  99
 100 static int shmem_getpage(struct inode *inode, unsigned long idx,
 101                          struct page **pagep, enum sgp_type sgp, int *type);
 102
 103 static inline struct page *shmem_dir_alloc(gfp_t gfp_mask)
 104 {
 105         /*
 106          * The above definition of ENTRIES_PER_PAGE, and the use of
 107          * BLOCKS_PER_PAGE on indirect pages, assume PAGE_CACHE_SIZE:
 108          * might be reconsidered if it ever diverges from PAGE_SIZE.
 109          *
 110          * Mobility flags are masked out as swap vectors cannot move
 111          */
 112         return alloc_pages((gfp_mask & ~GFP_MOVABLE_MASK) | __GFP_ZERO,
 113                                 PAGE_CACHE_SHIFT-PAGE_SHIFT);
 114 }
 115
 116 static inline void shmem_dir_free(struct page *page)
 117 {
 118         __free_pages(page, PAGE_CACHE_SHIFT-PAGE_SHIFT);
 119 }
 120
 121 static struct page **shmem_dir_map(struct page *page)
 122 {
 123         return (struct page **)kmap_atomic(page, KM_USER0);
 124 }
 125
 126 static inline void shmem_dir_unmap(struct page **dir)
 127 {
 128         kunmap_atomic(dir, KM_USER0);
 129 }
 130
 131 static swp_entry_t *shmem_swp_map(struct page *page)
 132 {
 133         return (swp_entry_t *)kmap_atomic(page, KM_USER1);
 134 }
 135
 136 static inline void shmem_swp_balance_unmap(void)
 137 {
 138         /*
 139          * When passing a pointer to an i_direct entry, to code which
 140          * also handles indirect entries and so will shmem_swp_unmap,
 141          * we must arrange for the preempt count to remain in balance.
 142          * What kmap_atomic of a lowmem page does depends on config
 143          * and architecture, so pretend to kmap_atomic some lowmem page.
 144          */
 145         (void) kmap_atomic(ZERO_PAGE(0), KM_USER1);
 146 }
 147
 148 static inline void shmem_swp_unmap(swp_entry_t *entry)
 149 {
 150         kunmap_atomic(entry, KM_USER1);
 151 }
 152
 153 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
 154 {
 155         return sb->s_fs_info;
 156 }
 157
 158 /*
 159  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
 160  * for shared memory and for shared anonymous (/dev/zero) mappings
 161  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
 162  * consistent with the pre-accounting of private mappings ...
 163  */
 164 static inline int shmem_acct_size(unsigned long flags, loff_t size)
 165 {
 166         return (flags & VM_ACCOUNT)?
 167                 security_vm_enough_memory(VM_ACCT(size)): 0;
 168 }
 169
 170 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
 171 {
 172         if (flags & VM_ACCOUNT)
 173                 vm_unacct_memory(VM_ACCT(size));
 174 }
 175
 176 /*
 177  * ... whereas tmpfs objects are accounted incrementally as
 178  * pages are allocated, in order to allow huge sparse files.
 179  * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
 180  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
 181  */
 182 static inline int shmem_acct_block(unsigned long flags)
 183 {
 184         return (flags & VM_ACCOUNT)?
 185                 0: security_vm_enough_memory(VM_ACCT(PAGE_CACHE_SIZE));
 186 }
 187
 188 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
 189 {
 190         if (!(flags & VM_ACCOUNT))
 191                 vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
 192 }
 193
 194 static const struct super_operations shmem_ops;
 195 static const struct address_space_operations shmem_aops;
 196 static const struct file_operations shmem_file_operations;
 197 static const struct inode_operations shmem_inode_operations;
 198 static const struct inode_operations shmem_dir_inode_operations;
 199 static const struct inode_operations shmem_special_inode_operations;
 200 static struct vm_operations_struct shmem_vm_ops;
 201
 202 static struct backing_dev_info shmem_backing_dev_info  __read_mostly = {
 203         .ra_pages       = 0,    /* No readahead */
 204         .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
 205         .unplug_io_fn   = default_unplug_io_fn,
 206 };
 207
 208 static LIST_HEAD(shmem_swaplist);
 209 static DEFINE_MUTEX(shmem_swaplist_mutex);
 210
 211 static void shmem_free_blocks(struct inode *inode, long pages)
 212 {
 213         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 214         if (sbinfo->max_blocks) {
 215                 spin_lock(&sbinfo->stat_lock);
 216                 sbinfo->free_blocks += pages;
 217                 inode->i_blocks -= pages*BLOCKS_PER_PAGE;
 218                 spin_unlock(&sbinfo->stat_lock);
 219         }
 220 }
 221
 222 static int shmem_reserve_inode(struct super_block *sb)
 223 {
 224         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
 225         if (sbinfo->max_inodes) {
 226                 spin_lock(&sbinfo->stat_lock);
 227                 if (!sbinfo->free_inodes) {
 228                         spin_unlock(&sbinfo->stat_lock);
 229                         return -ENOSPC;
 230                 }
 231                 sbinfo->free_inodes--;
 232                 spin_unlock(&sbinfo->stat_lock);
 233         }
 234         return 0;
 235 }
 236
 237 static void shmem_free_inode(struct super_block *sb)
 238 {
 239         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
 240         if (sbinfo->max_inodes) {
 241                 spin_lock(&sbinfo->stat_lock);
 242                 sbinfo->free_inodes++;
 243                 spin_unlock(&sbinfo->stat_lock);
 244         }
 245 }
 246
 247 /*
 248  * shmem_recalc_inode - recalculate the size of an inode
 249  *
 250  * @inode: inode to recalc
 251  *
 252  * We have to calculate the free blocks since the mm can drop
 253  * undirtied hole pages behind our back.
 254  *
 255  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
 256  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
 257  *
 258  * It has to be called with the spinlock held.
 259  */
 260 static void shmem_recalc_inode(struct inode *inode)
 261 {
 262         struct shmem_inode_info *info = SHMEM_I(inode);
 263         long freed;
 264
 265         freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
 266         if (freed > 0) {
 267                 info->alloced -= freed;
 268                 shmem_unacct_blocks(info->flags, freed);
 269                 shmem_free_blocks(inode, freed);
 270         }
 271 }
 272
 273 /*
 274  * shmem_swp_entry - find the swap vector position in the info structure
 275  *
 276  * @info:  info structure for the inode
 277  * @index: index of the page to find
 278  * @page:  optional page to add to the structure. Has to be preset to
 279  *         all zeros
 280  *
 281  * If there is no space allocated yet it will return NULL when
 282  * page is NULL, else it will use the page for the needed block,
 283  * setting it to NULL on return to indicate that it has been used.
 284  *
 285  * The swap vector is organized the following way:
 286  *
 287  * There are SHMEM_NR_DIRECT entries directly stored in the
 288  * shmem_inode_info structure. So small files do not need an addional
 289  * allocation.
 290  *
 291  * For pages with index > SHMEM_NR_DIRECT there is the pointer
 292  * i_indirect which points to a page which holds in the first half
 293  * doubly indirect blocks, in the second half triple indirect blocks:
 294  *
 295  * For an artificial ENTRIES_PER_PAGE = 4 this would lead to the
 296  * following layout (for SHMEM_NR_DIRECT == 16):
 297  *
 298  * i_indirect -> dir --> 16-19
 299  *            |      +-> 20-23
 300  *            |
 301  *            +-->dir2 --> 24-27
 302  *            |        +-> 28-31
 303  *            |        +-> 32-35
 304  *            |        +-> 36-39
 305  *            |
 306  *            +-->dir3 --> 40-43
 307  *                     +-> 44-47
 308  *                     +-> 48-51
 309  *                     +-> 52-55
 310  */
 311 static swp_entry_t *shmem_swp_entry(struct shmem_inode_info *info, unsigned long index, struct page **page)
 312 {
 313         unsigned long offset;
 314         struct page **dir;
 315         struct page *subdir;
 316
 317         if (index < SHMEM_NR_DIRECT) {
 318                 shmem_swp_balance_unmap();
 319                 return info->i_direct+index;
 320         }
 321         if (!info->i_indirect) {
 322                 if (page) {
 323                         info->i_indirect = *page;
 324                         *page = NULL;
 325                 }
 326                 return NULL;                    /* need another page */
 327         }
 328
 329         index -= SHMEM_NR_DIRECT;
 330         offset = index % ENTRIES_PER_PAGE;
 331         index /= ENTRIES_PER_PAGE;
 332         dir = shmem_dir_map(info->i_indirect);
 333
 334         if (index >= ENTRIES_PER_PAGE/2) {
 335                 index -= ENTRIES_PER_PAGE/2;
 336                 dir += ENTRIES_PER_PAGE/2 + index/ENTRIES_PER_PAGE;
 337                 index %= ENTRIES_PER_PAGE;
 338                 subdir = *dir;
 339                 if (!subdir) {
 340                         if (page) {
 341                                 *dir = *page;
 342                                 *page = NULL;
 343                         }
 344                         shmem_dir_unmap(dir);
 345                         return NULL;            /* need another page */
 346                 }
 347                 shmem_dir_unmap(dir);
 348                 dir = shmem_dir_map(subdir);
 349         }
 350
 351         dir += index;
 352         subdir = *dir;
 353         if (!subdir) {
 354                 if (!page || !(subdir = *page)) {
 355                         shmem_dir_unmap(dir);
 356                         return NULL;            /* need a page */
 357                 }
 358                 *dir = subdir;
 359                 *page = NULL;
 360         }
 361         shmem_dir_unmap(dir);
 362         return shmem_swp_map(subdir) + offset;
 363 }
 364
 365 static void shmem_swp_set(struct shmem_inode_info *info, swp_entry_t *entry, unsigned long value)
 366 {
 367         long incdec = value? 1: -1;
 368
 369         entry->val = value;
 370         info->swapped += incdec;
 371         if ((unsigned long)(entry - info->i_direct) >= SHMEM_NR_DIRECT) {
 372                 struct page *page = kmap_atomic_to_page(entry);
 373                 set_page_private(page, page_private(page) + incdec);
 374         }
 375 }
 376
 377 /*
 378  * shmem_swp_alloc - get the position of the swap entry for the page.
 379  *                   If it does not exist allocate the entry.
 380  *
 381  * @info:       info structure for the inode
 382  * @index:      index of the page to find
 383  * @sgp:        check and recheck i_size? skip allocation?
 384  */
 385 static swp_entry_t *shmem_swp_alloc(struct shmem_inode_info *info, unsigned long index, enum sgp_type sgp)
 386 {
 387         struct inode *inode = &info->vfs_inode;
 388         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 389         struct page *page = NULL;
 390         swp_entry_t *entry;
 391
 392         if (sgp != SGP_WRITE &&
 393             ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode))
 394                 return ERR_PTR(-EINVAL);
 395
 396         while (!(entry = shmem_swp_entry(info, index, &page))) {
 397                 if (sgp == SGP_READ)
 398                         return shmem_swp_map(ZERO_PAGE(0));
 399                 /*
 400                  * Test free_blocks against 1 not 0, since we have 1 data
 401                  * page (and perhaps indirect index pages) yet to allocate:
 402                  * a waste to allocate index if we cannot allocate data.
 403                  */
 404                 if (sbinfo->max_blocks) {
 405                         spin_lock(&sbinfo->stat_lock);
 406                         if (sbinfo->free_blocks <= 1) {
 407                                 spin_unlock(&sbinfo->stat_lock);
 408                                 return ERR_PTR(-ENOSPC);
 409                         }
 410                         sbinfo->free_blocks--;
 411                         inode->i_blocks += BLOCKS_PER_PAGE;
 412                         spin_unlock(&sbinfo->stat_lock);
 413                 }
 414
 415                 spin_unlock(&info->lock);
 416                 page = shmem_dir_alloc(mapping_gfp_mask(inode->i_mapping));
 417                 if (page)
 418                         set_page_private(page, 0);
 419                 spin_lock(&info->lock);
 420
 421                 if (!page) {
 422                         shmem_free_blocks(inode, 1);
 423                         return ERR_PTR(-ENOMEM);
 424                 }
 425                 if (sgp != SGP_WRITE &&
 426                     ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
 427                         entry = ERR_PTR(-EINVAL);
 428                         break;
 429                 }
 430                 if (info->next_index <= index)
 431                         info->next_index = index + 1;
 432         }
 433         if (page) {
 434                 /* another task gave its page, or truncated the file */
 435                 shmem_free_blocks(inode, 1);
 436                 shmem_dir_free(page);
 437         }
 438         if (info->next_index <= index && !IS_ERR(entry))
 439                 info->next_index = index + 1;
 440         return entry;
 441 }
 442
 443 /*
 444  * shmem_free_swp - free some swap entries in a directory
 445  *
 446  * @dir:        pointer to the directory
 447  * @edir:       pointer after last entry of the directory
 448  * @punch_lock: pointer to spinlock when needed for the holepunch case
 449  */
 450 static int shmem_free_swp(swp_entry_t *dir, swp_entry_t *edir,
 451                                                 spinlock_t *punch_lock)
 452 {
 453         spinlock_t *punch_unlock = NULL;
 454         swp_entry_t *ptr;
 455         int freed = 0;
 456
 457         for (ptr = dir; ptr < edir; ptr++) {
 458                 if (ptr->val) {
 459                         if (unlikely(punch_lock)) {
 460                                 punch_unlock = punch_lock;
 461                                 punch_lock = NULL;
 462                                 spin_lock(punch_unlock);
 463                                 if (!ptr->val)
 464                                         continue;
 465                         }
 466                         free_swap_and_cache(*ptr);
 467                         *ptr = (swp_entry_t){0};
 468                         freed++;
 469                 }
 470         }
 471         if (punch_unlock)
 472                 spin_unlock(punch_unlock);
 473         return freed;
 474 }
 475
 476 static int shmem_map_and_free_swp(struct page *subdir, int offset,
 477                 int limit, struct page ***dir, spinlock_t *punch_lock)
 478 {
 479         swp_entry_t *ptr;
 480         int freed = 0;
 481
 482         ptr = shmem_swp_map(subdir);
 483         for (; offset < limit; offset += LATENCY_LIMIT) {
 484                 int size = limit - offset;
 485                 if (size > LATENCY_LIMIT)
 486                         size = LATENCY_LIMIT;
 487                 freed += shmem_free_swp(ptr+offset, ptr+offset+size,
 488                                                         punch_lock);
 489                 if (need_resched()) {
 490                         shmem_swp_unmap(ptr);
 491                         if (*dir) {
 492                                 shmem_dir_unmap(*dir);
 493                                 *dir = NULL;
 494                         }
 495                         cond_resched();
 496                         ptr = shmem_swp_map(subdir);
 497                 }
 498         }
 499         shmem_swp_unmap(ptr);
 500         return freed;
 501 }
 502
 503 static void shmem_free_pages(struct list_head *next)
 504 {
 505         struct page *page;
 506         int freed = 0;
 507
 508         do {
 509                 page = container_of(next, struct page, lru);
 510                 next = next->next;
 511                 shmem_dir_free(page);
 512                 freed++;
 513                 if (freed >= LATENCY_LIMIT) {
 514                         cond_resched();
 515                         freed = 0;
 516                 }
 517         } while (next);
 518 }
 519
 520 static void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end)
 521 {
 522         struct shmem_inode_info *info = SHMEM_I(inode);
 523         unsigned long idx;
 524         unsigned long size;
 525         unsigned long limit;
 526         unsigned long stage;
 527         unsigned long diroff;
 528         struct page **dir;
 529         struct page *topdir;
 530         struct page *middir;
 531         struct page *subdir;
 532         swp_entry_t *ptr;
 533         LIST_HEAD(pages_to_free);
 534         long nr_pages_to_free = 0;
 535         long nr_swaps_freed = 0;
 536         int offset;
 537         int freed;
 538         int punch_hole;
 539         spinlock_t *needs_lock;
 540         spinlock_t *punch_lock;
 541         unsigned long upper_limit;
 542
 543         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
 544         idx = (start + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 545         if (idx >= info->next_index)
 546                 return;
 547
 548         spin_lock(&info->lock);
 549         info->flags |= SHMEM_TRUNCATE;
 550         if (likely(end == (loff_t) -1)) {
 551                 limit = info->next_index;
 552                 upper_limit = SHMEM_MAX_INDEX;
 553                 info->next_index = idx;
 554                 needs_lock = NULL;
 555                 punch_hole = 0;
 556         } else {
 557                 if (end + 1 >= inode->i_size) { /* we may free a little more */
 558                         limit = (inode->i_size + PAGE_CACHE_SIZE - 1) >>
 559                                                         PAGE_CACHE_SHIFT;
 560                         upper_limit = SHMEM_MAX_INDEX;
 561                 } else {
 562                         limit = (end + 1) >> PAGE_CACHE_SHIFT;
 563                         upper_limit = limit;
 564                 }
 565                 needs_lock = &info->lock;
 566                 punch_hole = 1;
 567         }
 568
 569         topdir = info->i_indirect;
 570         if (topdir && idx <= SHMEM_NR_DIRECT && !punch_hole) {
 571                 info->i_indirect = NULL;
 572                 nr_pages_to_free++;
 573                 list_add(&topdir->lru, &pages_to_free);
 574         }
 575         spin_unlock(&info->lock);
 576
 577         if (info->swapped && idx < SHMEM_NR_DIRECT) {
 578                 ptr = info->i_direct;
 579                 size = limit;
 580                 if (size > SHMEM_NR_DIRECT)
 581                         size = SHMEM_NR_DIRECT;
 582                 nr_swaps_freed = shmem_free_swp(ptr+idx, ptr+size, needs_lock);
 583         }
 584
 585         /*
 586          * If there are no indirect blocks or we are punching a hole
 587          * below indirect blocks, nothing to be done.
 588          */
 589         if (!topdir || limit <= SHMEM_NR_DIRECT)
 590                 goto done2;
 591
 592         /*
 593          * The truncation case has already dropped info->lock, and we're safe
 594          * because i_size and next_index have already been lowered, preventing
 595          * access beyond.  But in the punch_hole case, we still need to take
 596          * the lock when updating the swap directory, because there might be
 597          * racing accesses by shmem_getpage(SGP_CACHE), shmem_unuse_inode or
 598          * shmem_writepage.  However, whenever we find we can remove a whole
 599          * directory page (not at the misaligned start or end of the range),
 600          * we first NULLify its pointer in the level above, and then have no
 601          * need to take the lock when updating its contents: needs_lock and
 602          * punch_lock (either pointing to info->lock or NULL) manage this.
 603          */
 604
 605         upper_limit -= SHMEM_NR_DIRECT;
 606         limit -= SHMEM_NR_DIRECT;
 607         idx = (idx > SHMEM_NR_DIRECT)? (idx - SHMEM_NR_DIRECT): 0;
 608         offset = idx % ENTRIES_PER_PAGE;
 609         idx -= offset;
 610
 611         dir = shmem_dir_map(topdir);
 612         stage = ENTRIES_PER_PAGEPAGE/2;
 613         if (idx < ENTRIES_PER_PAGEPAGE/2) {
 614                 middir = topdir;
 615                 diroff = idx/ENTRIES_PER_PAGE;
 616         } else {
 617                 dir += ENTRIES_PER_PAGE/2;
 618                 dir += (idx - ENTRIES_PER_PAGEPAGE/2)/ENTRIES_PER_PAGEPAGE;
 619                 while (stage <= idx)
 620                         stage += ENTRIES_PER_PAGEPAGE;
 621                 middir = *dir;
 622                 if (*dir) {
 623                         diroff = ((idx - ENTRIES_PER_PAGEPAGE/2) %
 624                                 ENTRIES_PER_PAGEPAGE) / ENTRIES_PER_PAGE;
 625                         if (!diroff && !offset && upper_limit >= stage) {
 626                                 if (needs_lock) {
 627                                         spin_lock(needs_lock);
 628                                         *dir = NULL;
 629                                         spin_unlock(needs_lock);
 630                                         needs_lock = NULL;
 631                                 } else
 632                                         *dir = NULL;
 633                                 nr_pages_to_free++;
 634                                 list_add(&middir->lru, &pages_to_free);
 635                         }
 636                         shmem_dir_unmap(dir);
 637                         dir = shmem_dir_map(middir);
 638                 } else {
 639                         diroff = 0;
 640                         offset = 0;
 641                         idx = stage;
 642                 }
 643         }
 644
 645         for (; idx < limit; idx += ENTRIES_PER_PAGE, diroff++) {
 646                 if (unlikely(idx == stage)) {
 647                         shmem_dir_unmap(dir);
 648                         dir = shmem_dir_map(topdir) +
 649                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
 650                         while (!*dir) {
 651                                 dir++;
 652                                 idx += ENTRIES_PER_PAGEPAGE;
 653                                 if (idx >= limit)
 654                                         goto done1;
 655                         }
 656                         stage = idx + ENTRIES_PER_PAGEPAGE;
 657                         middir = *dir;
 658                         if (punch_hole)
 659                                 needs_lock = &info->lock;
 660                         if (upper_limit >= stage) {
 661                                 if (needs_lock) {
 662                                         spin_lock(needs_lock);
 663                                         *dir = NULL;
 664                                         spin_unlock(needs_lock);
 665                                         needs_lock = NULL;
 666                                 } else
 667                                         *dir = NULL;
 668                                 nr_pages_to_free++;
 669                                 list_add(&middir->lru, &pages_to_free);
 670                         }
 671                         shmem_dir_unmap(dir);
 672                         cond_resched();
 673                         dir = shmem_dir_map(middir);
 674                         diroff = 0;
 675                 }
 676                 punch_lock = needs_lock;
 677                 subdir = dir[diroff];
 678                 if (subdir && !offset && upper_limit-idx >= ENTRIES_PER_PAGE) {
 679                         if (needs_lock) {
 680                                 spin_lock(needs_lock);
 681                                 dir[diroff] = NULL;
 682                                 spin_unlock(needs_lock);
 683                                 punch_lock = NULL;
 684                         } else
 685                                 dir[diroff] = NULL;
 686                         nr_pages_to_free++;
 687                         list_add(&subdir->lru, &pages_to_free);
 688                 }
 689                 if (subdir && page_private(subdir) /* has swap entries */) {
 690                         size = limit - idx;
 691                         if (size > ENTRIES_PER_PAGE)
 692                                 size = ENTRIES_PER_PAGE;
 693                         freed = shmem_map_and_free_swp(subdir,
 694                                         offset, size, &dir, punch_lock);
 695                         if (!dir)
 696                                 dir = shmem_dir_map(middir);
 697                         nr_swaps_freed += freed;
 698                         if (offset || punch_lock) {
 699                                 spin_lock(&info->lock);
 700                                 set_page_private(subdir,
 701                                         page_private(subdir) - freed);
 702                                 spin_unlock(&info->lock);
 703                         } else
 704                                 BUG_ON(page_private(subdir) != freed);
 705                 }
 706                 offset = 0;
 707         }
 708 done1:
 709         shmem_dir_unmap(dir);
 710 done2:
 711         if (inode->i_mapping->nrpages && (info->flags & SHMEM_PAGEIN)) {
 712                 /*
 713                  * Call truncate_inode_pages again: racing shmem_unuse_inode
 714                  * may have swizzled a page in from swap since vmtruncate or
 715                  * generic_delete_inode did it, before we lowered next_index.
 716                  * Also, though shmem_getpage checks i_size before adding to
 717                  * cache, no recheck after: so fix the narrow window there too.
 718                  *
 719                  * Recalling truncate_inode_pages_range and unmap_mapping_range
 720                  * every time for punch_hole (which never got a chance to clear
 721                  * SHMEM_PAGEIN at the start of vmtruncate_range) is expensive,
 722                  * yet hardly ever necessary: try to optimize them out later.
 723                  */
 724                 truncate_inode_pages_range(inode->i_mapping, start, end);
 725                 if (punch_hole)
 726                         unmap_mapping_range(inode->i_mapping, start,
 727                                                         end - start, 1);
 728         }
 729
 730         spin_lock(&info->lock);
 731         info->flags &= ~SHMEM_TRUNCATE;
 732         info->swapped -= nr_swaps_freed;
 733         if (nr_pages_to_free)
 734                 shmem_free_blocks(inode, nr_pages_to_free);
 735         shmem_recalc_inode(inode);
 736         spin_unlock(&info->lock);
 737
 738         /*
 739          * Empty swap vector directory pages to be freed?
 740          */
 741         if (!list_empty(&pages_to_free)) {
 742                 pages_to_free.prev->next = NULL;
 743                 shmem_free_pages(pages_to_free.next);
 744         }
 745 }
 746
 747 static void shmem_truncate(struct inode *inode)
 748 {
 749         shmem_truncate_range(inode, inode->i_size, (loff_t)-1);
 750 }
 751
 752 static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
 753 {
 754         struct inode *inode = dentry->d_inode;
 755         struct page *page = NULL;
 756         int error;
 757
 758         if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
 759                 if (attr->ia_size < inode->i_size) {
 760                         /*
 761                          * If truncating down to a partial page, then
 762                          * if that page is already allocated, hold it
 763                          * in memory until the truncation is over, so
 764                          * truncate_partial_page cannnot miss it were
 765                          * it assigned to swap.
 766                          */
 767                         if (attr->ia_size & (PAGE_CACHE_SIZE-1)) {
 768                                 (void) shmem_getpage(inode,
 769                                         attr->ia_size>>PAGE_CACHE_SHIFT,
 770                                                 &page, SGP_READ, NULL);
 771                                 if (page)
 772                                         unlock_page(page);
 773                         }
 774                         /*
 775                          * Reset SHMEM_PAGEIN flag so that shmem_truncate can
 776                          * detect if any pages might have been added to cache
 777                          * after truncate_inode_pages.  But we needn't bother
 778                          * if it's being fully truncated to zero-length: the
 779                          * nrpages check is efficient enough in that case.
 780                          */
 781                         if (attr->ia_size) {
 782                                 struct shmem_inode_info *info = SHMEM_I(inode);
 783                                 spin_lock(&info->lock);
 784                                 info->flags &= ~SHMEM_PAGEIN;
 785                                 spin_unlock(&info->lock);
 786                         }
 787                 }
 788         }
 789
 790         error = inode_change_ok(inode, attr);
 791         if (!error)
 792                 error = inode_setattr(inode, attr);
 793 #ifdef CONFIG_TMPFS_POSIX_ACL
 794         if (!error && (attr->ia_valid & ATTR_MODE))
 795                 error = generic_acl_chmod(inode, &shmem_acl_ops);
 796 #endif
 797         if (page)
 798                 page_cache_release(page);
 799         return error;
 800 }
 801
 802 static void shmem_delete_inode(struct inode *inode)
 803 {
 804         struct shmem_inode_info *info = SHMEM_I(inode);
 805
 806         if (inode->i_op->truncate == shmem_truncate) {
 807                 truncate_inode_pages(inode->i_mapping, 0);
 808                 shmem_unacct_size(info->flags, inode->i_size);
 809                 inode->i_size = 0;
 810                 shmem_truncate(inode);
 811                 if (!list_empty(&info->swaplist)) {
 812                         mutex_lock(&shmem_swaplist_mutex);
 813                         list_del_init(&info->swaplist);
 814                         mutex_unlock(&shmem_swaplist_mutex);
 815                 }
 816         }
 817         BUG_ON(inode->i_blocks);
 818         shmem_free_inode(inode->i_sb);
 819         clear_inode(inode);
 820 }
 821
 822 static inline int shmem_find_swp(swp_entry_t entry, swp_entry_t *dir, swp_entry_t *edir)
 823 {
 824         swp_entry_t *ptr;
 825
 826         for (ptr = dir; ptr < edir; ptr++) {
 827                 if (ptr->val == entry.val)
 828                         return ptr - dir;
 829         }
 830         return -1;
 831 }
 832
 833 static int shmem_unuse_inode(struct shmem_inode_info *info, swp_entry_t entry, struct page *page)
 834 {
 835         struct inode *inode;
 836         unsigned long idx;
 837         unsigned long size;
 838         unsigned long limit;
 839         unsigned long stage;
 840         struct page **dir;
 841         struct page *subdir;
 842         swp_entry_t *ptr;
 843         int offset;
 844         int error;
 845
 846         idx = 0;
 847         ptr = info->i_direct;
 848         spin_lock(&info->lock);
 849         if (!info->swapped) {
 850                 list_del_init(&info->swaplist);
 851                 goto lost2;
 852         }
 853         limit = info->next_index;
 854         size = limit;
 855         if (size > SHMEM_NR_DIRECT)
 856                 size = SHMEM_NR_DIRECT;
 857         offset = shmem_find_swp(entry, ptr, ptr+size);
 858         if (offset >= 0)
 859                 goto found;
 860         if (!info->i_indirect)
 861                 goto lost2;
 862
 863         dir = shmem_dir_map(info->i_indirect);
 864         stage = SHMEM_NR_DIRECT + ENTRIES_PER_PAGEPAGE/2;
 865
 866         for (idx = SHMEM_NR_DIRECT; idx < limit; idx += ENTRIES_PER_PAGE, dir++) {
 867                 if (unlikely(idx == stage)) {
 868                         shmem_dir_unmap(dir-1);
 869                         if (cond_resched_lock(&info->lock)) {
 870                                 /* check it has not been truncated */
 871                                 if (limit > info->next_index) {
 872                                         limit = info->next_index;
 873                                         if (idx >= limit)
 874                                                 goto lost2;
 875                                 }
 876                         }
 877                         dir = shmem_dir_map(info->i_indirect) +
 878                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
 879                         while (!*dir) {
 880                                 dir++;
 881                                 idx += ENTRIES_PER_PAGEPAGE;
 882                                 if (idx >= limit)
 883                                         goto lost1;
 884                         }
 885                         stage = idx + ENTRIES_PER_PAGEPAGE;
 886                         subdir = *dir;
 887                         shmem_dir_unmap(dir);
 888                         dir = shmem_dir_map(subdir);
 889                 }
 890                 subdir = *dir;
 891                 if (subdir && page_private(subdir)) {
 892                         ptr = shmem_swp_map(subdir);
 893                         size = limit - idx;
 894                         if (size > ENTRIES_PER_PAGE)
 895                                 size = ENTRIES_PER_PAGE;
 896                         offset = shmem_find_swp(entry, ptr, ptr+size);
 897                         shmem_swp_unmap(ptr);
 898                         if (offset >= 0) {
 899                                 shmem_dir_unmap(dir);
 900                                 goto found;
 901                         }
 902                 }
 903         }
 904 lost1:
 905         shmem_dir_unmap(dir-1);
 906 lost2:
 907         spin_unlock(&info->lock);
 908         return 0;
 909 found:
 910         idx += offset;
 911         inode = igrab(&info->vfs_inode);
 912         spin_unlock(&info->lock);
 913
 914         /*
 915          * Move _head_ to start search for next from here.
 916          * But be careful: shmem_delete_inode checks list_empty without taking
 917          * mutex, and there's an instant in list_move_tail when info->swaplist
 918          * would appear empty, if it were the only one on shmem_swaplist.  We
 919          * could avoid doing it if inode NULL; or use this minor optimization.
 920          */
 921         if (shmem_swaplist.next != &info->swaplist)
 922                 list_move_tail(&shmem_swaplist, &info->swaplist);
 923         mutex_unlock(&shmem_swaplist_mutex);
 924
 925         error = 1;
 926         if (!inode)
 927                 goto out;
 928         /* Precharge page while we can wait, compensate afterwards */
 929         error = mem_cgroup_cache_charge(page, current->mm, GFP_KERNEL);
 930         if (error)
 931                 goto out;
 932         error = radix_tree_preload(GFP_KERNEL);
 933         if (error)
 934                 goto uncharge;
 935         error = 1;
 936
 937         spin_lock(&info->lock);
 938         ptr = shmem_swp_entry(info, idx, NULL);
 939         if (ptr && ptr->val == entry.val)
 940                 error = add_to_page_cache(page, inode->i_mapping,
 941                                                 idx, GFP_NOWAIT);
 942         if (error == -EEXIST) {
 943                 struct page *filepage = find_get_page(inode->i_mapping, idx);
 944                 error = 1;
 945                 if (filepage) {
 946                         /*
 947                          * There might be a more uptodate page coming down
 948                          * from a stacked writepage: forget our swappage if so.
 949                          */
 950                         if (PageUptodate(filepage))
 951                                 error = 0;
 952                         page_cache_release(filepage);
 953                 }
 954         }
 955         if (!error) {
 956                 delete_from_swap_cache(page);
 957                 set_page_dirty(page);
 958                 info->flags |= SHMEM_PAGEIN;
 959                 shmem_swp_set(info, ptr, 0);
 960                 swap_free(entry);
 961                 error = 1;      /* not an error, but entry was found */
 962         }
 963         if (ptr)
 964                 shmem_swp_unmap(ptr);
 965         spin_unlock(&info->lock);
 966         radix_tree_preload_end();
 967 uncharge:
 968         mem_cgroup_uncharge_page(page);
 969 out:
 970         unlock_page(page);
 971         page_cache_release(page);
 972         iput(inode);            /* allows for NULL */
 973         return error;
 974 }
 975
 976 /*
 977  * shmem_unuse() search for an eventually swapped out shmem page.
 978  */
 979 int shmem_unuse(swp_entry_t entry, struct page *page)
 980 {
 981         struct list_head *p, *next;
 982         struct shmem_inode_info *info;
 983         int found = 0;
 984
 985         mutex_lock(&shmem_swaplist_mutex);
 986         list_for_each_safe(p, next, &shmem_swaplist) {
 987                 info = list_entry(p, struct shmem_inode_info, swaplist);
 988                 found = shmem_unuse_inode(info, entry, page);
 989                 cond_resched();
 990                 if (found)
 991                         goto out;
 992         }
 993         mutex_unlock(&shmem_swaplist_mutex);
 994 out:    return found;   /* 0 or 1 or -ENOMEM */
 995 }
 996
 997 /*
 998  * Move the page from the page cache to the swap cache.
 999  */
1000 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
1001 {
1002         struct shmem_inode_info *info;
1003         swp_entry_t *entry, swap;
1004         struct address_space *mapping;
1005         unsigned long index;
1006         struct inode *inode;
1007
1008         BUG_ON(!PageLocked(page));
1009         mapping = page->mapping;
1010         index = page->index;
1011         inode = mapping->host;
1012         info = SHMEM_I(inode);
1013         if (info->flags & VM_LOCKED)
1014                 goto redirty;
1015         if (!total_swap_pages)
1016                 goto redirty;
1017
1018         /*
1019          * shmem_backing_dev_info's capabilities prevent regular writeback or
1020          * sync from ever calling shmem_writepage; but a stacking filesystem
1021          * may use the ->writepage of its underlying filesystem, in which case
1022          * tmpfs should write out to swap only in response to memory pressure,
1023          * and not for pdflush or sync.  However, in those cases, we do still
1024          * want to check if there's a redundant swappage to be discarded.
1025          */
1026         if (wbc->for_reclaim)
1027                 swap = get_swap_page();
1028         else
1029                 swap.val = 0;
1030
1031         spin_lock(&info->lock);
1032         if (index >= info->next_index) {
1033                 BUG_ON(!(info->flags & SHMEM_TRUNCATE));
1034                 goto unlock;
1035         }
1036         entry = shmem_swp_entry(info, index, NULL);
1037         if (entry->val) {
1038                 /*
1039                  * The more uptodate page coming down from a stacked
1040                  * writepage should replace our old swappage.
1041                  */
1042                 free_swap_and_cache(*entry);
1043                 shmem_swp_set(info, entry, 0);
1044         }
1045         shmem_recalc_inode(inode);
1046
1047         if (swap.val && add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
1048                 remove_from_page_cache(page);
1049                 shmem_swp_set(info, entry, swap.val);
1050                 shmem_swp_unmap(entry);
1051                 if (list_empty(&info->swaplist))
1052                         inode = igrab(inode);
1053                 else
1054                         inode = NULL;
1055                 spin_unlock(&info->lock);
1056                 swap_duplicate(swap);
1057                 BUG_ON(page_mapped(page));
1058                 page_cache_release(page);       /* pagecache ref */
1059                 set_page_dirty(page);
1060                 unlock_page(page);
1061                 if (inode) {
1062                         mutex_lock(&shmem_swaplist_mutex);
1063                         /* move instead of add in case we're racing */
1064                         list_move_tail(&info->swaplist, &shmem_swaplist);
1065                         mutex_unlock(&shmem_swaplist_mutex);
1066                         iput(inode);
1067                 }
1068                 return 0;
1069         }
1070
1071         shmem_swp_unmap(entry);
1072 unlock:
1073         spin_unlock(&info->lock);
1074         swap_free(swap);
1075 redirty:
1076         set_page_dirty(page);
1077         if (wbc->for_reclaim)
1078                 return AOP_WRITEPAGE_ACTIVATE;  /* Return with page locked */
1079         unlock_page(page);
1080         return 0;
1081 }
1082
1083 #ifdef CONFIG_NUMA
1084 #ifdef CONFIG_TMPFS
1085 static int shmem_parse_mpol(char *value, int *policy, nodemask_t *policy_nodes)
1086 {
1087         char *nodelist = strchr(value, ':');
1088         int err = 1;
1089
1090         if (nodelist) {
1091                 /* NUL-terminate policy string */
1092                 *nodelist++ = '\0';
1093                 if (nodelist_parse(nodelist, *policy_nodes))
1094                         goto out;
1095                 if (!nodes_subset(*policy_nodes, node_states[N_HIGH_MEMORY]))
1096                         goto out;
1097         }
1098         if (!strcmp(value, "default")) {
1099                 *policy = MPOL_DEFAULT;
1100                 /* Don't allow a nodelist */
1101                 if (!nodelist)
1102                         err = 0;
1103         } else if (!strcmp(value, "prefer")) {
1104                 *policy = MPOL_PREFERRED;
1105                 /* Insist on a nodelist of one node only */
1106                 if (nodelist) {
1107                         char *rest = nodelist;
1108                         while (isdigit(*rest))
1109                                 rest++;
1110                         if (!*rest)
1111                                 err = 0;
1112                 }
1113         } else if (!strcmp(value, "bind")) {
1114                 *policy = MPOL_BIND;
1115                 /* Insist on a nodelist */
1116                 if (nodelist)
1117                         err = 0;
1118         } else if (!strcmp(value, "interleave")) {
1119                 *policy = MPOL_INTERLEAVE;
1120                 /*
1121                  * Default to online nodes with memory if no nodelist
1122                  */
1123                 if (!nodelist)
1124                         *policy_nodes = node_states[N_HIGH_MEMORY];
1125                 err = 0;
1126         }
1127 out:
1128         /* Restore string for error message */
1129         if (nodelist)
1130                 *--nodelist = ':';
1131         return err;
1132 }
1133
1134 static void shmem_show_mpol(struct seq_file *seq, int policy,
1135                             const nodemask_t policy_nodes)
1136 {
1137         char *policy_string;
1138
1139         switch (policy) {
1140         case MPOL_PREFERRED:
1141                 policy_string = "prefer";
1142                 break;
1143         case MPOL_BIND:
1144                 policy_string = "bind";
1145                 break;
1146         case MPOL_INTERLEAVE:
1147                 policy_string = "interleave";
1148                 break;
1149         default:
1150                 /* MPOL_DEFAULT */
1151                 return;
1152         }
1153
1154         seq_printf(seq, ",mpol=%s", policy_string);
1155
1156         if (policy != MPOL_INTERLEAVE ||
1157             !nodes_equal(policy_nodes, node_states[N_HIGH_MEMORY])) {
1158                 char buffer[64];
1159                 int len;
1160
1161                 len = nodelist_scnprintf(buffer, sizeof(buffer), policy_nodes);
1162                 if (len < sizeof(buffer))
1163                         seq_printf(seq, ":%s", buffer);
1164                 else
1165                         seq_printf(seq, ":?");
1166         }
1167 }
1168 #endif /* CONFIG_TMPFS */
1169
1170 static struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
1171                         struct shmem_inode_info *info, unsigned long idx)
1172 {
1173         struct vm_area_struct pvma;
1174         struct page *page;
1175
1176         /* Create a pseudo vma that just contains the policy */
1177         pvma.vm_start = 0;
1178         pvma.vm_pgoff = idx;
1179         pvma.vm_ops = NULL;
1180         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx);
1181         page = swapin_readahead(entry, gfp, &pvma, 0);
1182         mpol_free(pvma.vm_policy);
1183         return page;
1184 }
1185
1186 static struct page *shmem_alloc_page(gfp_t gfp,
1187                         struct shmem_inode_info *info, unsigned long idx)
1188 {
1189         struct vm_area_struct pvma;
1190         struct page *page;
1191
1192         /* Create a pseudo vma that just contains the policy */
1193         pvma.vm_start = 0;
1194         pvma.vm_pgoff = idx;
1195         pvma.vm_ops = NULL;
1196         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx);
1197         page = alloc_page_vma(gfp, &pvma, 0);
1198         mpol_free(pvma.vm_policy);
1199         return page;
1200 }
1201 #else /* !CONFIG_NUMA */
1202 #ifdef CONFIG_TMPFS
1203 static inline int shmem_parse_mpol(char *value, int *policy,
1204                                                 nodemask_t *policy_nodes)
1205 {
1206         return 1;
1207 }
1208
1209 static inline void shmem_show_mpol(struct seq_file *seq, int policy,
1210                             const nodemask_t policy_nodes)
1211 {
1212 }
1213 #endif /* CONFIG_TMPFS */
1214
1215 static inline struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
1216                         struct shmem_inode_info *info, unsigned long idx)
1217 {
1218         return swapin_readahead(entry, gfp, NULL, 0);
1219 }
1220
1221 static inline struct page *shmem_alloc_page(gfp_t gfp,
1222                         struct shmem_inode_info *info, unsigned long idx)
1223 {
1224         return alloc_page(gfp);
1225 }
1226 #endif /* CONFIG_NUMA */
1227
1228 /*
1229  * shmem_getpage - either get the page from swap or allocate a new one
1230  *
1231  * If we allocate a new one we do not mark it dirty. That's up to the
1232  * vm. If we swap it in we mark it dirty since we also free the swap
1233  * entry since a page cannot live in both the swap and page cache
1234  */
1235 static int shmem_getpage(struct inode *inode, unsigned long idx,
1236                         struct page **pagep, enum sgp_type sgp, int *type)
1237 {
1238         struct address_space *mapping = inode->i_mapping;
1239         struct shmem_inode_info *info = SHMEM_I(inode);
1240         struct shmem_sb_info *sbinfo;
1241         struct page *filepage = *pagep;
1242         struct page *swappage;
1243         swp_entry_t *entry;
1244         swp_entry_t swap;
1245         gfp_t gfp;
1246         int error;
1247
1248         if (idx >= SHMEM_MAX_INDEX)
1249                 return -EFBIG;
1250
1251         if (type)
1252                 *type = 0;
1253
1254         /*
1255          * Normally, filepage is NULL on entry, and either found
1256          * uptodate immediately, or allocated and zeroed, or read
1257          * in under swappage, which is then assigned to filepage.
1258          * But shmem_readpage (required for splice) passes in a locked
1259          * filepage, which may be found not uptodate by other callers
1260          * too, and may need to be copied from the swappage read in.
1261          */
1262 repeat:
1263         if (!filepage)
1264                 filepage = find_lock_page(mapping, idx);
1265         if (filepage && PageUptodate(filepage))
1266                 goto done;
1267         error = 0;
1268         gfp = mapping_gfp_mask(mapping);
1269         if (!filepage) {
1270                 /*
1271                  * Try to preload while we can wait, to not make a habit of
1272                  * draining atomic reserves; but don't latch on to this cpu.
1273                  */
1274                 error = radix_tree_preload(gfp & ~__GFP_HIGHMEM);
1275                 if (error)
1276                         goto failed;
1277                 radix_tree_preload_end();
1278         }
1279
1280         spin_lock(&info->lock);
1281         shmem_recalc_inode(inode);
1282         entry = shmem_swp_alloc(info, idx, sgp);
1283         if (IS_ERR(entry)) {
1284                 spin_unlock(&info->lock);
1285                 error = PTR_ERR(entry);
1286                 goto failed;
1287         }
1288         swap = *entry;
1289
1290         if (swap.val) {
1291                 /* Look it up and read it in.. */
1292                 swappage = lookup_swap_cache(swap);
1293                 if (!swappage) {
1294                         shmem_swp_unmap(entry);
1295                         /* here we actually do the io */
1296                         if (type && !(*type & VM_FAULT_MAJOR)) {
1297                                 __count_vm_event(PGMAJFAULT);
1298                                 *type |= VM_FAULT_MAJOR;
1299                         }
1300                         spin_unlock(&info->lock);
1301                         swappage = shmem_swapin(swap, gfp, info, idx);
1302                         if (!swappage) {
1303                                 spin_lock(&info->lock);
1304                                 entry = shmem_swp_alloc(info, idx, sgp);
1305                                 if (IS_ERR(entry))
1306                                         error = PTR_ERR(entry);
1307                                 else {
1308                                         if (entry->val == swap.val)
1309                                                 error = -ENOMEM;
1310                                         shmem_swp_unmap(entry);
1311                                 }
1312                                 spin_unlock(&info->lock);
1313                                 if (error)
1314                                         goto failed;
1315                                 goto repeat;
1316                         }
1317                         wait_on_page_locked(swappage);
1318                         page_cache_release(swappage);
1319                         goto repeat;
1320                 }
1321
1322                 /* We have to do this with page locked to prevent races */
1323                 if (TestSetPageLocked(swappage)) {
1324                         shmem_swp_unmap(entry);
1325                         spin_unlock(&info->lock);
1326                         wait_on_page_locked(swappage);
1327                         page_cache_release(swappage);
1328                         goto repeat;
1329                 }
1330                 if (PageWriteback(swappage)) {
1331                         shmem_swp_unmap(entry);
1332                         spin_unlock(&info->lock);
1333                         wait_on_page_writeback(swappage);
1334                         unlock_page(swappage);
1335                         page_cache_release(swappage);
1336                         goto repeat;
1337                 }
1338                 if (!PageUptodate(swappage)) {
1339                         shmem_swp_unmap(entry);
1340                         spin_unlock(&info->lock);
1341                         unlock_page(swappage);
1342                         page_cache_release(swappage);
1343                         error = -EIO;
1344                         goto failed;
1345                 }
1346
1347                 if (filepage) {
1348                         shmem_swp_set(info, entry, 0);
1349                         shmem_swp_unmap(entry);
1350                         delete_from_swap_cache(swappage);
1351                         spin_unlock(&info->lock);
1352                         copy_highpage(filepage, swappage);
1353                         unlock_page(swappage);
1354                         page_cache_release(swappage);
1355                         flush_dcache_page(filepage);
1356                         SetPageUptodate(filepage);
1357                         set_page_dirty(filepage);
1358                         swap_free(swap);
1359                 } else if (!(error = add_to_page_cache(
1360                                 swappage, mapping, idx, GFP_NOWAIT))) {
1361                         info->flags |= SHMEM_PAGEIN;
1362                         shmem_swp_set(info, entry, 0);
1363                         shmem_swp_unmap(entry);
1364                         delete_from_swap_cache(swappage);
1365                         spin_unlock(&info->lock);
1366                         filepage = swappage;
1367                         set_page_dirty(filepage);
1368                         swap_free(swap);
1369                 } else {
1370                         shmem_swp_unmap(entry);
1371                         spin_unlock(&info->lock);
1372                         unlock_page(swappage);
1373                         if (error == -ENOMEM) {
1374                                 /* allow reclaim from this memory cgroup */
1375                                 error = mem_cgroup_cache_charge(swappage,
1376                                         current->mm, gfp & ~__GFP_HIGHMEM);
1377                                 if (error) {
1378                                         page_cache_release(swappage);
1379                                         goto failed;
1380                                 }
1381                                 mem_cgroup_uncharge_page(swappage);
1382                         }
1383                         page_cache_release(swappage);
1384                         goto repeat;
1385                 }
1386         } else if (sgp == SGP_READ && !filepage) {
1387                 shmem_swp_unmap(entry);
1388                 filepage = find_get_page(mapping, idx);
1389                 if (filepage &&
1390                     (!PageUptodate(filepage) || TestSetPageLocked(filepage))) {
1391                         spin_unlock(&info->lock);
1392                         wait_on_page_locked(filepage);
1393                         page_cache_release(filepage);
1394                         filepage = NULL;
1395                         goto repeat;
1396                 }
1397                 spin_unlock(&info->lock);
1398         } else {
1399                 shmem_swp_unmap(entry);
1400                 sbinfo = SHMEM_SB(inode->i_sb);
1401                 if (sbinfo->max_blocks) {
1402                         spin_lock(&sbinfo->stat_lock);
1403                         if (sbinfo->free_blocks == 0 ||
1404                             shmem_acct_block(info->flags)) {
1405                                 spin_unlock(&sbinfo->stat_lock);
1406                                 spin_unlock(&info->lock);
1407                                 error = -ENOSPC;
1408                                 goto failed;
1409                         }
1410                         sbinfo->free_blocks--;
1411                         inode->i_blocks += BLOCKS_PER_PAGE;
1412                         spin_unlock(&sbinfo->stat_lock);
1413                 } else if (shmem_acct_block(info->flags)) {
1414                         spin_unlock(&info->lock);
1415                         error = -ENOSPC;
1416                         goto failed;
1417                 }
1418
1419                 if (!filepage) {
1420                         spin_unlock(&info->lock);
1421                         filepage = shmem_alloc_page(gfp, info, idx);
1422                         if (!filepage) {
1423                                 shmem_unacct_blocks(info->flags, 1);
1424                                 shmem_free_blocks(inode, 1);
1425                                 error = -ENOMEM;
1426                                 goto failed;
1427                         }
1428
1429                         /* Precharge page while we can wait, compensate after */
1430                         error = mem_cgroup_cache_charge(filepage, current->mm,
1431                                                         gfp & ~__GFP_HIGHMEM);
1432                         if (error) {
1433                                 page_cache_release(filepage);
1434                                 shmem_unacct_blocks(info->flags, 1);
1435                                 shmem_free_blocks(inode, 1);
1436                                 filepage = NULL;
1437                                 goto failed;
1438                         }
1439
1440                         spin_lock(&info->lock);
1441                         entry = shmem_swp_alloc(info, idx, sgp);
1442                         if (IS_ERR(entry))
1443                                 error = PTR_ERR(entry);
1444                         else {
1445                                 swap = *entry;
1446                                 shmem_swp_unmap(entry);
1447                         }
1448                         if (error || swap.val || 0 != add_to_page_cache_lru(
1449                                         filepage, mapping, idx, GFP_NOWAIT)) {
1450                                 spin_unlock(&info->lock);
1451                                 mem_cgroup_uncharge_page(filepage);
1452                                 page_cache_release(filepage);
1453                                 shmem_unacct_blocks(info->flags, 1);
1454                                 shmem_free_blocks(inode, 1);
1455                                 filepage = NULL;
1456                                 if (error)
1457                                         goto failed;
1458                                 goto repeat;
1459                         }
1460                         mem_cgroup_uncharge_page(filepage);
1461                         info->flags |= SHMEM_PAGEIN;
1462                 }
1463
1464                 info->alloced++;
1465                 spin_unlock(&info->lock);
1466                 clear_highpage(filepage);
1467                 flush_dcache_page(filepage);
1468                 SetPageUptodate(filepage);
1469                 if (sgp == SGP_DIRTY)
1470                         set_page_dirty(filepage);
1471         }
1472 done:
1473         *pagep = filepage;
1474         return 0;
1475
1476 failed:
1477         if (*pagep != filepage) {
1478                 unlock_page(filepage);
1479                 page_cache_release(filepage);
1480         }
1481         return error;
1482 }
1483
1484 static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1485 {
1486         struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1487         int error;
1488         int ret;
1489
1490         if (((loff_t)vmf->pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
1491                 return VM_FAULT_SIGBUS;
1492
1493         error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret);
1494         if (error)
1495                 return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1496
1497         mark_page_accessed(vmf->page);
1498         return ret | VM_FAULT_LOCKED;
1499 }
1500
1501 #ifdef CONFIG_NUMA
1502 static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *new)
1503 {
1504         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1505         return mpol_set_shared_policy(&SHMEM_I(i)->policy, vma, new);
1506 }
1507
1508 static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
1509                                           unsigned long addr)
1510 {
1511         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1512         unsigned long idx;
1513
1514         idx = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1515         return mpol_shared_policy_lookup(&SHMEM_I(i)->policy, idx);
1516 }
1517 #endif
1518
1519 int shmem_lock(struct file *file, int lock, struct user_struct *user)
1520 {
1521         struct inode *inode = file->f_path.dentry->d_inode;
1522         struct shmem_inode_info *info = SHMEM_I(inode);
1523         int retval = -ENOMEM;
1524
1525         spin_lock(&info->lock);
1526         if (lock && !(info->flags & VM_LOCKED)) {
1527                 if (!user_shm_lock(inode->i_size, user))
1528                         goto out_nomem;
1529                 info->flags |= VM_LOCKED;
1530         }
1531         if (!lock && (info->flags & VM_LOCKED) && user) {
1532                 user_shm_unlock(inode->i_size, user);
1533                 info->flags &= ~VM_LOCKED;
1534         }
1535         retval = 0;
1536 out_nomem:
1537         spin_unlock(&info->lock);
1538         return retval;
1539 }
1540
1541 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1542 {
1543         file_accessed(file);
1544         vma->vm_ops = &shmem_vm_ops;
1545         vma->vm_flags |= VM_CAN_NONLINEAR;
1546         return 0;
1547 }
1548
1549 static struct inode *
1550 shmem_get_inode(struct super_block *sb, int mode, dev_t dev)
1551 {
1552         struct inode *inode;
1553         struct shmem_inode_info *info;
1554         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1555
1556         if (shmem_reserve_inode(sb))
1557                 return NULL;
1558
1559         inode = new_inode(sb);
1560         if (inode) {
1561                 inode->i_mode = mode;
1562                 inode->i_uid = current->fsuid;
1563                 inode->i_gid = current->fsgid;
1564                 inode->i_blocks = 0;
1565                 inode->i_mapping->a_ops = &shmem_aops;
1566                 inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1567                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1568                 inode->i_generation = get_seconds();
1569                 info = SHMEM_I(inode);
1570                 memset(info, 0, (char *)inode - (char *)info);
1571                 spin_lock_init(&info->lock);
1572                 INIT_LIST_HEAD(&info->swaplist);
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_op = &shmem_inode_operations;
1581                         inode->i_fop = &shmem_file_operations;
1582                         mpol_shared_policy_init(&info->policy, sbinfo->policy,
1583                                                         &sbinfo->policy_nodes);
1584                         break;
1585                 case S_IFDIR:
1586                         inc_nlink(inode);
1587                         /* Some things misbehave if size == 0 on a directory */
1588                         inode->i_size = 2 * BOGO_DIRENT_SIZE;
1589                         inode->i_op = &shmem_dir_inode_operations;
1590                         inode->i_fop = &simple_dir_operations;
1591                         break;
1592                 case S_IFLNK:
1593                         /*
1594                          * Must not load anything in the rbtree,
1595                          * mpol_free_shared_policy will not be called.
1596                          */
1597                         mpol_shared_policy_init(&info->policy, MPOL_DEFAULT,
1598                                                 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         unlock_page(page);
1645         set_page_dirty(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_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
1754 {
1755         read_descriptor_t desc;
1756
1757         if ((ssize_t) count < 0)
1758                 return -EINVAL;
1759         if (!access_ok(VERIFY_WRITE, buf, count))
1760                 return -EFAULT;
1761         if (!count)
1762                 return 0;
1763
1764         desc.written = 0;
1765         desc.count = count;
1766         desc.arg.buf = buf;
1767         desc.error = 0;
1768
1769         do_shmem_file_read(filp, ppos, &desc, file_read_actor);
1770         if (desc.written)
1771                 return desc.written;
1772         return desc.error;
1773 }
1774
1775 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
1776 {
1777         struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
1778
1779         buf->f_type = TMPFS_MAGIC;
1780         buf->f_bsize = PAGE_CACHE_SIZE;
1781         buf->f_namelen = NAME_MAX;
1782         spin_lock(&sbinfo->stat_lock);
1783         if (sbinfo->max_blocks) {
1784                 buf->f_blocks = sbinfo->max_blocks;
1785                 buf->f_bavail = buf->f_bfree = sbinfo->free_blocks;
1786         }
1787         if (sbinfo->max_inodes) {
1788                 buf->f_files = sbinfo->max_inodes;
1789                 buf->f_ffree = sbinfo->free_inodes;
1790         }
1791         /* else leave those fields 0 like simple_statfs */
1792         spin_unlock(&sbinfo->stat_lock);
1793         return 0;
1794 }
1795
1796 /*
1797  * File creation. Allocate an inode, and we're done..
1798  */
1799 static int
1800 shmem_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
1801 {
1802         struct inode *inode = shmem_get_inode(dir->i_sb, mode, dev);
1803         int error = -ENOSPC;
1804
1805         if (inode) {
1806                 error = security_inode_init_security(inode, dir, NULL, NULL,
1807                                                      NULL);
1808                 if (error) {
1809                         if (error != -EOPNOTSUPP) {
1810                                 iput(inode);
1811                                 return error;
1812                         }
1813                 }
1814                 error = shmem_acl_init(inode, dir);
1815                 if (error) {
1816                         iput(inode);
1817                         return error;
1818                 }
1819                 if (dir->i_mode & S_ISGID) {
1820                         inode->i_gid = dir->i_gid;
1821                         if (S_ISDIR(mode))
1822                                 inode->i_mode |= S_ISGID;
1823                 }
1824                 dir->i_size += BOGO_DIRENT_SIZE;
1825                 dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1826                 d_instantiate(dentry, inode);
1827                 dget(dentry); /* Extra count - pin the dentry in core */
1828         }
1829         return error;
1830 }
1831
1832 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, int mode)
1833 {
1834         int error;
1835
1836         if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
1837                 return error;
1838         inc_nlink(dir);
1839         return 0;
1840 }
1841
1842 static int shmem_create(struct inode *dir, struct dentry *dentry, int mode,
1843                 struct nameidata *nd)
1844 {
1845         return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
1846 }
1847
1848 /*
1849  * Link a file..
1850  */
1851 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
1852 {
1853         struct inode *inode = old_dentry->d_inode;
1854         int ret;
1855
1856         /*
1857          * No ordinary (disk based) filesystem counts links as inodes;
1858          * but each new link needs a new dentry, pinning lowmem, and
1859          * tmpfs dentries cannot be pruned until they are unlinked.
1860          */
1861         ret = shmem_reserve_inode(inode->i_sb);
1862         if (ret)
1863                 goto out;
1864
1865         dir->i_size += BOGO_DIRENT_SIZE;
1866         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1867         inc_nlink(inode);
1868         atomic_inc(&inode->i_count);    /* New dentry reference */
1869         dget(dentry);           /* Extra pinning count for the created dentry */
1870         d_instantiate(dentry, inode);
1871 out:
1872         return ret;
1873 }
1874
1875 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
1876 {
1877         struct inode *inode = dentry->d_inode;
1878
1879         if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
1880                 shmem_free_inode(inode->i_sb);
1881
1882         dir->i_size -= BOGO_DIRENT_SIZE;
1883         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1884         drop_nlink(inode);
1885         dput(dentry);   /* Undo the count from "create" - this does all the work */
1886         return 0;
1887 }
1888
1889 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
1890 {
1891         if (!simple_empty(dentry))
1892                 return -ENOTEMPTY;
1893
1894         drop_nlink(dentry->d_inode);
1895         drop_nlink(dir);
1896         return shmem_unlink(dir, dentry);
1897 }
1898
1899 /*
1900  * The VFS layer already does all the dentry stuff for rename,
1901  * we just have to decrement the usage count for the target if
1902  * it exists so that the VFS layer correctly free's it when it
1903  * gets overwritten.
1904  */
1905 static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
1906 {
1907         struct inode *inode = old_dentry->d_inode;
1908         int they_are_dirs = S_ISDIR(inode->i_mode);
1909
1910         if (!simple_empty(new_dentry))
1911                 return -ENOTEMPTY;
1912
1913         if (new_dentry->d_inode) {
1914                 (void) shmem_unlink(new_dir, new_dentry);
1915                 if (they_are_dirs)
1916                         drop_nlink(old_dir);
1917         } else if (they_are_dirs) {
1918                 drop_nlink(old_dir);
1919                 inc_nlink(new_dir);
1920         }
1921
1922         old_dir->i_size -= BOGO_DIRENT_SIZE;
1923         new_dir->i_size += BOGO_DIRENT_SIZE;
1924         old_dir->i_ctime = old_dir->i_mtime =
1925         new_dir->i_ctime = new_dir->i_mtime =
1926         inode->i_ctime = CURRENT_TIME;
1927         return 0;
1928 }
1929
1930 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
1931 {
1932         int error;
1933         int len;
1934         struct inode *inode;
1935         struct page *page = NULL;
1936         char *kaddr;
1937         struct shmem_inode_info *info;
1938
1939         len = strlen(symname) + 1;
1940         if (len > PAGE_CACHE_SIZE)
1941                 return -ENAMETOOLONG;
1942
1943         inode = shmem_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0);
1944         if (!inode)
1945                 return -ENOSPC;
1946
1947         error = security_inode_init_security(inode, dir, NULL, NULL,
1948                                              NULL);
1949         if (error) {
1950                 if (error != -EOPNOTSUPP) {
1951                         iput(inode);
1952                         return error;
1953                 }
1954                 error = 0;
1955         }
1956
1957         info = SHMEM_I(inode);
1958         inode->i_size = len-1;
1959         if (len <= (char *)inode - (char *)info) {
1960                 /* do it inline */
1961                 memcpy(info, symname, len);
1962                 inode->i_op = &shmem_symlink_inline_operations;
1963         } else {
1964                 error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
1965                 if (error) {
1966                         iput(inode);
1967                         return error;
1968                 }
1969                 unlock_page(page);
1970                 inode->i_op = &shmem_symlink_inode_operations;
1971                 kaddr = kmap_atomic(page, KM_USER0);
1972                 memcpy(kaddr, symname, len);
1973                 kunmap_atomic(kaddr, KM_USER0);
1974                 set_page_dirty(page);
1975                 page_cache_release(page);
1976         }
1977         if (dir->i_mode & S_ISGID)
1978                 inode->i_gid = dir->i_gid;
1979         dir->i_size += BOGO_DIRENT_SIZE;
1980         dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1981         d_instantiate(dentry, inode);
1982         dget(dentry);
1983         return 0;
1984 }
1985
1986 static void *shmem_follow_link_inline(struct dentry *dentry, struct nameidata *nd)
1987 {
1988         nd_set_link(nd, (char *)SHMEM_I(dentry->d_inode));
1989         return NULL;
1990 }
1991
1992 static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
1993 {
1994         struct page *page = NULL;
1995         int res = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
1996         nd_set_link(nd, res ? ERR_PTR(res) : kmap(page));
1997         if (page)
1998                 unlock_page(page);
1999         return page;
2000 }
2001
2002 static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
2003 {
2004         if (!IS_ERR(nd_get_link(nd))) {
2005                 struct page *page = cookie;
2006                 kunmap(page);
2007                 mark_page_accessed(page);
2008                 page_cache_release(page);
2009         }
2010 }
2011
2012 static const struct inode_operations shmem_symlink_inline_operations = {
2013         .readlink       = generic_readlink,
2014         .follow_link    = shmem_follow_link_inline,
2015 };
2016
2017 static const struct inode_operations shmem_symlink_inode_operations = {
2018         .truncate       = shmem_truncate,
2019         .readlink       = generic_readlink,
2020         .follow_link    = shmem_follow_link,
2021         .put_link       = shmem_put_link,
2022 };
2023
2024 #ifdef CONFIG_TMPFS_POSIX_ACL
2025 /**
2026  * Superblocks without xattr inode operations will get security.* xattr
2027  * support from the VFS "for free". As soon as we have any other xattrs
2028  * like ACLs, we also need to implement the security.* handlers at
2029  * filesystem level, though.
2030  */
2031
2032 static size_t shmem_xattr_security_list(struct inode *inode, char *list,
2033                                         size_t list_len, const char *name,
2034                                         size_t name_len)
2035 {
2036         return security_inode_listsecurity(inode, list, list_len);
2037 }
2038
2039 static int shmem_xattr_security_get(struct inode *inode, const char *name,
2040                                     void *buffer, size_t size)
2041 {
2042         if (strcmp(name, "") == 0)
2043                 return -EINVAL;
2044         return xattr_getsecurity(inode, name, buffer, size);
2045 }
2046
2047 static int shmem_xattr_security_set(struct inode *inode, const char *name,
2048                                     const void *value, size_t size, int flags)
2049 {
2050         if (strcmp(name, "") == 0)
2051                 return -EINVAL;
2052         return security_inode_setsecurity(inode, name, value, size, flags);
2053 }
2054
2055 static struct xattr_handler shmem_xattr_security_handler = {
2056         .prefix = XATTR_SECURITY_PREFIX,
2057         .list   = shmem_xattr_security_list,
2058         .get    = shmem_xattr_security_get,
2059         .set    = shmem_xattr_security_set,
2060 };
2061
2062 static struct xattr_handler *shmem_xattr_handlers[] = {
2063         &shmem_xattr_acl_access_handler,
2064         &shmem_xattr_acl_default_handler,
2065         &shmem_xattr_security_handler,
2066         NULL
2067 };
2068 #endif
2069
2070 static struct dentry *shmem_get_parent(struct dentry *child)
2071 {
2072         return ERR_PTR(-ESTALE);
2073 }
2074
2075 static int shmem_match(struct inode *ino, void *vfh)
2076 {
2077         __u32 *fh = vfh;
2078         __u64 inum = fh[2];
2079         inum = (inum << 32) | fh[1];
2080         return ino->i_ino == inum && fh[0] == ino->i_generation;
2081 }
2082
2083 static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
2084                 struct fid *fid, int fh_len, int fh_type)
2085 {
2086         struct inode *inode;
2087         struct dentry *dentry = NULL;
2088         u64 inum = fid->raw[2];
2089         inum = (inum << 32) | fid->raw[1];
2090
2091         if (fh_len < 3)
2092                 return NULL;
2093
2094         inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
2095                         shmem_match, fid->raw);
2096         if (inode) {
2097                 dentry = d_find_alias(inode);
2098                 iput(inode);
2099         }
2100
2101         return dentry;
2102 }
2103
2104 static int shmem_encode_fh(struct dentry *dentry, __u32 *fh, int *len,
2105                                 int connectable)
2106 {
2107         struct inode *inode = dentry->d_inode;
2108
2109         if (*len < 3)
2110                 return 255;
2111
2112         if (hlist_unhashed(&inode->i_hash)) {
2113                 /* Unfortunately insert_inode_hash is not idempotent,
2114                  * so as we hash inodes here rather than at creation
2115                  * time, we need a lock to ensure we only try
2116                  * to do it once
2117                  */
2118                 static DEFINE_SPINLOCK(lock);
2119                 spin_lock(&lock);
2120                 if (hlist_unhashed(&inode->i_hash))
2121                         __insert_inode_hash(inode,
2122                                             inode->i_ino + inode->i_generation);
2123                 spin_unlock(&lock);
2124         }
2125
2126         fh[0] = inode->i_generation;
2127         fh[1] = inode->i_ino;
2128         fh[2] = ((__u64)inode->i_ino) >> 32;
2129
2130         *len = 3;
2131         return 1;
2132 }
2133
2134 static const struct export_operations shmem_export_ops = {
2135         .get_parent     = shmem_get_parent,
2136         .encode_fh      = shmem_encode_fh,
2137         .fh_to_dentry   = shmem_fh_to_dentry,
2138 };
2139
2140 static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
2141                                bool remount)
2142 {
2143         char *this_char, *value, *rest;
2144
2145         while (options != NULL) {
2146                 this_char = options;
2147                 for (;;) {
2148                         /*
2149                          * NUL-terminate this option: unfortunately,
2150                          * mount options form a comma-separated list,
2151                          * but mpol's nodelist may also contain commas.
2152                          */
2153                         options = strchr(options, ',');
2154                         if (options == NULL)
2155                                 break;
2156                         options++;
2157                         if (!isdigit(*options)) {
2158                                 options[-1] = '\0';
2159                                 break;
2160                         }
2161                 }
2162                 if (!*this_char)
2163                         continue;
2164                 if ((value = strchr(this_char,'=')) != NULL) {
2165                         *value++ = 0;
2166                 } else {
2167                         printk(KERN_ERR
2168                             "tmpfs: No value for mount option '%s'\n",
2169                             this_char);
2170                         return 1;
2171                 }
2172
2173                 if (!strcmp(this_char,"size")) {
2174                         unsigned long long size;
2175                         size = memparse(value,&rest);
2176                         if (*rest == '%') {
2177                                 size <<= PAGE_SHIFT;
2178                                 size *= totalram_pages;
2179                                 do_div(size, 100);
2180                                 rest++;
2181                         }
2182                         if (*rest)
2183                                 goto bad_val;
2184                         sbinfo->max_blocks =
2185                                 DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
2186                 } else if (!strcmp(this_char,"nr_blocks")) {
2187                         sbinfo->max_blocks = memparse(value, &rest);
2188                         if (*rest)
2189                                 goto bad_val;
2190                 } else if (!strcmp(this_char,"nr_inodes")) {
2191                         sbinfo->max_inodes = memparse(value, &rest);
2192                         if (*rest)
2193                                 goto bad_val;
2194                 } else if (!strcmp(this_char,"mode")) {
2195                         if (remount)
2196                                 continue;
2197                         sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
2198                         if (*rest)
2199                                 goto bad_val;
2200                 } else if (!strcmp(this_char,"uid")) {
2201                         if (remount)
2202                                 continue;
2203                         sbinfo->uid = simple_strtoul(value, &rest, 0);
2204                         if (*rest)
2205                                 goto bad_val;
2206                 } else if (!strcmp(this_char,"gid")) {
2207                         if (remount)
2208                                 continue;
2209                         sbinfo->gid = simple_strtoul(value, &rest, 0);
2210                         if (*rest)
2211                                 goto bad_val;
2212                 } else if (!strcmp(this_char,"mpol")) {
2213                         if (shmem_parse_mpol(value, &sbinfo->policy,
2214                                              &sbinfo->policy_nodes))
2215                                 goto bad_val;
2216                 } else {
2217                         printk(KERN_ERR "tmpfs: Bad mount option %s\n",
2218                                this_char);
2219                         return 1;
2220                 }
2221         }
2222         return 0;
2223
2224 bad_val:
2225         printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
2226                value, this_char);
2227         return 1;
2228
2229 }
2230
2231 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2232 {
2233         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2234         struct shmem_sb_info config = *sbinfo;
2235         unsigned long blocks;
2236         unsigned long inodes;
2237         int error = -EINVAL;
2238
2239         if (shmem_parse_options(data, &config, true))
2240                 return error;
2241
2242         spin_lock(&sbinfo->stat_lock);
2243         blocks = sbinfo->max_blocks - sbinfo->free_blocks;
2244         inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2245         if (config.max_blocks < blocks)
2246                 goto out;
2247         if (config.max_inodes < inodes)
2248                 goto out;
2249         /*
2250          * Those tests also disallow limited->unlimited while any are in
2251          * use, so i_blocks will always be zero when max_blocks is zero;
2252          * but we must separately disallow unlimited->limited, because
2253          * in that case we have no record of how much is already in use.
2254          */
2255         if (config.max_blocks && !sbinfo->max_blocks)
2256                 goto out;
2257         if (config.max_inodes && !sbinfo->max_inodes)
2258                 goto out;
2259
2260         error = 0;
2261         sbinfo->max_blocks  = config.max_blocks;
2262         sbinfo->free_blocks = config.max_blocks - blocks;
2263         sbinfo->max_inodes  = config.max_inodes;
2264         sbinfo->free_inodes = config.max_inodes - inodes;
2265         sbinfo->policy      = config.policy;
2266         sbinfo->policy_nodes = config.policy_nodes;
2267 out:
2268         spin_unlock(&sbinfo->stat_lock);
2269         return error;
2270 }
2271
2272 static int shmem_show_options(struct seq_file *seq, struct vfsmount *vfs)
2273 {
2274         struct shmem_sb_info *sbinfo = SHMEM_SB(vfs->mnt_sb);
2275
2276         if (sbinfo->max_blocks != shmem_default_max_blocks())
2277                 seq_printf(seq, ",size=%luk",
2278                         sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10));
2279         if (sbinfo->max_inodes != shmem_default_max_inodes())
2280                 seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
2281         if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
2282                 seq_printf(seq, ",mode=%03o", sbinfo->mode);
2283         if (sbinfo->uid != 0)
2284                 seq_printf(seq, ",uid=%u", sbinfo->uid);
2285         if (sbinfo->gid != 0)
2286                 seq_printf(seq, ",gid=%u", sbinfo->gid);
2287         shmem_show_mpol(seq, sbinfo->policy, sbinfo->policy_nodes);
2288         return 0;
2289 }
2290 #endif /* CONFIG_TMPFS */
2291
2292 static void shmem_put_super(struct super_block *sb)
2293 {
2294         kfree(sb->s_fs_info);
2295         sb->s_fs_info = NULL;
2296 }
2297
2298 static int shmem_fill_super(struct super_block *sb,
2299                             void *data, int silent)
2300 {
2301         struct inode *inode;
2302         struct dentry *root;
2303         struct shmem_sb_info *sbinfo;
2304         int err = -ENOMEM;
2305
2306         /* Round up to L1_CACHE_BYTES to resist false sharing */
2307         sbinfo = kmalloc(max((int)sizeof(struct shmem_sb_info),
2308                                 L1_CACHE_BYTES), GFP_KERNEL);
2309         if (!sbinfo)
2310                 return -ENOMEM;
2311
2312         sbinfo->max_blocks = 0;
2313         sbinfo->max_inodes = 0;
2314         sbinfo->mode = S_IRWXUGO | S_ISVTX;
2315         sbinfo->uid = current->fsuid;
2316         sbinfo->gid = current->fsgid;
2317         sbinfo->policy = MPOL_DEFAULT;
2318         sbinfo->policy_nodes = node_states[N_HIGH_MEMORY];
2319         sb->s_fs_info = sbinfo;
2320
2321 #ifdef CONFIG_TMPFS
2322         /*
2323          * Per default we only allow half of the physical ram per
2324          * tmpfs instance, limiting inodes to one per page of lowmem;
2325          * but the internal instance is left unlimited.
2326          */
2327         if (!(sb->s_flags & MS_NOUSER)) {
2328                 sbinfo->max_blocks = shmem_default_max_blocks();
2329                 sbinfo->max_inodes = shmem_default_max_inodes();
2330                 if (shmem_parse_options(data, sbinfo, false)) {
2331                         err = -EINVAL;
2332                         goto failed;
2333                 }
2334         }
2335         sb->s_export_op = &shmem_export_ops;
2336 #else
2337         sb->s_flags |= MS_NOUSER;
2338 #endif
2339
2340         spin_lock_init(&sbinfo->stat_lock);
2341         sbinfo->free_blocks = sbinfo->max_blocks;
2342         sbinfo->free_inodes = sbinfo->max_inodes;
2343
2344         sb->s_maxbytes = SHMEM_MAX_BYTES;
2345         sb->s_blocksize = PAGE_CACHE_SIZE;
2346         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
2347         sb->s_magic = TMPFS_MAGIC;
2348         sb->s_op = &shmem_ops;
2349         sb->s_time_gran = 1;
2350 #ifdef CONFIG_TMPFS_POSIX_ACL
2351         sb->s_xattr = shmem_xattr_handlers;
2352         sb->s_flags |= MS_POSIXACL;
2353 #endif
2354
2355         inode = shmem_get_inode(sb, S_IFDIR | sbinfo->mode, 0);
2356         if (!inode)
2357                 goto failed;
2358         inode->i_uid = sbinfo->uid;
2359         inode->i_gid = sbinfo->gid;
2360         root = d_alloc_root(inode);
2361         if (!root)
2362                 goto failed_iput;
2363         sb->s_root = root;
2364         return 0;
2365
2366 failed_iput:
2367         iput(inode);
2368 failed:
2369         shmem_put_super(sb);
2370         return err;
2371 }
2372
2373 static struct kmem_cache *shmem_inode_cachep;
2374
2375 static struct inode *shmem_alloc_inode(struct super_block *sb)
2376 {
2377         struct shmem_inode_info *p;
2378         p = (struct shmem_inode_info *)kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
2379         if (!p)
2380                 return NULL;
2381         return &p->vfs_inode;
2382 }
2383
2384 static void shmem_destroy_inode(struct inode *inode)
2385 {
2386         if ((inode->i_mode & S_IFMT) == S_IFREG) {
2387                 /* only struct inode is valid if it's an inline symlink */
2388                 mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2389         }
2390         shmem_acl_destroy_inode(inode);
2391         kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2392 }
2393
2394 static void init_once(struct kmem_cache *cachep, void *foo)
2395 {
2396         struct shmem_inode_info *p = (struct shmem_inode_info *) foo;
2397
2398         inode_init_once(&p->vfs_inode);
2399 #ifdef CONFIG_TMPFS_POSIX_ACL
2400         p->i_acl = NULL;
2401         p->i_default_acl = NULL;
2402 #endif
2403 }
2404
2405 static int init_inodecache(void)
2406 {
2407         shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
2408                                 sizeof(struct shmem_inode_info),
2409                                 0, SLAB_PANIC, init_once);
2410         return 0;
2411 }
2412
2413 static void destroy_inodecache(void)
2414 {
2415         kmem_cache_destroy(shmem_inode_cachep);
2416 }
2417
2418 static const struct address_space_operations shmem_aops = {
2419         .writepage      = shmem_writepage,
2420         .set_page_dirty = __set_page_dirty_no_writeback,
2421 #ifdef CONFIG_TMPFS
2422         .readpage       = shmem_readpage,
2423         .write_begin    = shmem_write_begin,
2424         .write_end      = shmem_write_end,
2425 #endif
2426         .migratepage    = migrate_page,
2427 };
2428
2429 static const struct file_operations shmem_file_operations = {
2430         .mmap           = shmem_mmap,
2431 #ifdef CONFIG_TMPFS
2432         .llseek         = generic_file_llseek,
2433         .read           = shmem_file_read,
2434         .write          = do_sync_write,
2435         .aio_write      = generic_file_aio_write,
2436         .fsync          = simple_sync_file,
2437         .splice_read    = generic_file_splice_read,
2438         .splice_write   = generic_file_splice_write,
2439 #endif
2440 };
2441
2442 static const struct inode_operations shmem_inode_operations = {
2443         .truncate       = shmem_truncate,
2444         .setattr        = shmem_notify_change,
2445         .truncate_range = shmem_truncate_range,
2446 #ifdef CONFIG_TMPFS_POSIX_ACL
2447         .setxattr       = generic_setxattr,
2448         .getxattr       = generic_getxattr,
2449         .listxattr      = generic_listxattr,
2450         .removexattr    = generic_removexattr,
2451         .permission     = shmem_permission,
2452 #endif
2453
2454 };
2455
2456 static const struct inode_operations shmem_dir_inode_operations = {
2457 #ifdef CONFIG_TMPFS
2458         .create         = shmem_create,
2459         .lookup         = simple_lookup,
2460         .link           = shmem_link,
2461         .unlink         = shmem_unlink,
2462         .symlink        = shmem_symlink,
2463         .mkdir          = shmem_mkdir,
2464         .rmdir          = shmem_rmdir,
2465         .mknod          = shmem_mknod,
2466         .rename         = shmem_rename,
2467 #endif
2468 #ifdef CONFIG_TMPFS_POSIX_ACL
2469         .setattr        = shmem_notify_change,
2470         .setxattr       = generic_setxattr,
2471         .getxattr       = generic_getxattr,
2472         .listxattr      = generic_listxattr,
2473         .removexattr    = generic_removexattr,
2474         .permission     = shmem_permission,
2475 #endif
2476 };
2477
2478 static const struct inode_operations shmem_special_inode_operations = {
2479 #ifdef CONFIG_TMPFS_POSIX_ACL
2480         .setattr        = shmem_notify_change,
2481         .setxattr       = generic_setxattr,
2482         .getxattr       = generic_getxattr,
2483         .listxattr      = generic_listxattr,
2484         .removexattr    = generic_removexattr,
2485         .permission     = shmem_permission,
2486 #endif
2487 };
2488
2489 static const struct super_operations shmem_ops = {
2490         .alloc_inode    = shmem_alloc_inode,
2491         .destroy_inode  = shmem_destroy_inode,
2492 #ifdef CONFIG_TMPFS
2493         .statfs         = shmem_statfs,
2494         .remount_fs     = shmem_remount_fs,
2495         .show_options   = shmem_show_options,
2496 #endif
2497         .delete_inode   = shmem_delete_inode,
2498         .drop_inode     = generic_delete_inode,
2499         .put_super      = shmem_put_super,
2500 };
2501
2502 static struct vm_operations_struct shmem_vm_ops = {
2503         .fault          = shmem_fault,
2504 #ifdef CONFIG_NUMA
2505         .set_policy     = shmem_set_policy,
2506         .get_policy     = shmem_get_policy,
2507 #endif
2508 };
2509
2510
2511 static int shmem_get_sb(struct file_system_type *fs_type,
2512         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
2513 {
2514         return get_sb_nodev(fs_type, flags, data, shmem_fill_super, mnt);
2515 }
2516
2517 static struct file_system_type tmpfs_fs_type = {
2518         .owner          = THIS_MODULE,
2519         .name           = "tmpfs",
2520         .get_sb         = shmem_get_sb,
2521         .kill_sb        = kill_litter_super,
2522 };
2523 static struct vfsmount *shm_mnt;
2524
2525 static int __init init_tmpfs(void)
2526 {
2527         int error;
2528
2529         error = bdi_init(&shmem_backing_dev_info);
2530         if (error)
2531                 goto out4;
2532
2533         error = init_inodecache();
2534         if (error)
2535                 goto out3;
2536
2537         error = register_filesystem(&tmpfs_fs_type);
2538         if (error) {
2539                 printk(KERN_ERR "Could not register tmpfs\n");
2540                 goto out2;
2541         }
2542
2543         shm_mnt = vfs_kern_mount(&tmpfs_fs_type, MS_NOUSER,
2544                                 tmpfs_fs_type.name, NULL);
2545         if (IS_ERR(shm_mnt)) {
2546                 error = PTR_ERR(shm_mnt);
2547                 printk(KERN_ERR "Could not kern_mount tmpfs\n");
2548                 goto out1;
2549         }
2550         return 0;
2551
2552 out1:
2553         unregister_filesystem(&tmpfs_fs_type);
2554 out2:
2555         destroy_inodecache();
2556 out3:
2557         bdi_destroy(&shmem_backing_dev_info);
2558 out4:
2559         shm_mnt = ERR_PTR(error);
2560         return error;
2561 }
2562 module_init(init_tmpfs)
2563
2564 /*
2565  * shmem_file_setup - get an unlinked file living in tmpfs
2566  *
2567  * @name: name for dentry (to be seen in /proc/<pid>/maps
2568  * @size: size to be set for the file
2569  *
2570  */
2571 struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags)
2572 {
2573         int error;
2574         struct file *file;
2575         struct inode *inode;
2576         struct dentry *dentry, *root;
2577         struct qstr this;
2578
2579         if (IS_ERR(shm_mnt))
2580                 return (void *)shm_mnt;
2581
2582         if (size < 0 || size > SHMEM_MAX_BYTES)
2583                 return ERR_PTR(-EINVAL);
2584
2585         if (shmem_acct_size(flags, size))
2586                 return ERR_PTR(-ENOMEM);
2587
2588         error = -ENOMEM;
2589         this.name = name;
2590         this.len = strlen(name);
2591         this.hash = 0; /* will go */
2592         root = shm_mnt->mnt_root;
2593         dentry = d_alloc(root, &this);
2594         if (!dentry)
2595                 goto put_memory;
2596
2597         error = -ENFILE;
2598         file = get_empty_filp();
2599         if (!file)
2600                 goto put_dentry;
2601
2602         error = -ENOSPC;
2603         inode = shmem_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0);
2604         if (!inode)
2605                 goto close_file;
2606
2607         SHMEM_I(inode)->flags = flags & VM_ACCOUNT;
2608         d_instantiate(dentry, inode);
2609         inode->i_size = size;
2610         inode->i_nlink = 0;     /* It is unlinked */
2611         init_file(file, shm_mnt, dentry, FMODE_WRITE | FMODE_READ,
2612                         &shmem_file_operations);
2613         return file;
2614
2615 close_file:
2616         put_filp(file);
2617 put_dentry:
2618         dput(dentry);
2619 put_memory:
2620         shmem_unacct_size(flags, size);
2621         return ERR_PTR(error);
2622 }
2623
2624 /*
2625  * shmem_zero_setup - setup a shared anonymous mapping
2626  *
2627  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
2628  */
2629 int shmem_zero_setup(struct vm_area_struct *vma)
2630 {
2631         struct file *file;
2632         loff_t size = vma->vm_end - vma->vm_start;
2633
2634         file = shmem_file_setup("dev/zero", size, vma->vm_flags);
2635         if (IS_ERR(file))
2636                 return PTR_ERR(file);
2637
2638         if (vma->vm_file)
2639                 fput(vma->vm_file);
2640         vma->vm_file = file;
2641         vma->vm_ops = &shmem_vm_ops;
2642         return 0;
2643 }