mm/shmem.c

   1 /*
   2  * Resizable virtual memory filesystem for Linux.
   3  *
   4  * Copyright (C) 2000 Linus Torvalds.
   5  *               2000 Transmeta Corp.
   6  *               2000-2001 Christoph Rohland
   7  *               2000-2001 SAP AG
   8  *               2002 Red Hat Inc.
   9  * Copyright (C) 2002-2005 Hugh Dickins.
  10  * Copyright (C) 2002-2005 VERITAS Software Corporation.
  11  * Copyright (C) 2004 Andi Kleen, SuSE Labs
  12  *
  13  * Extended attribute support for tmpfs:
  14  * Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@lkcl.net>
  15  * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
  16  *
  17  * tiny-shmem:
  18  * Copyright (c) 2004, 2008 Matt Mackall <mpm@selenic.com>
  19  *
  20  * This file is released under the GPL.
  21  */
  22
  23 #include <linux/fs.h>
  24 #include <linux/init.h>
  25 #include <linux/vfs.h>
  26 #include <linux/mount.h>
  27 #include <linux/file.h>
  28 #include <linux/mm.h>
  29 #include <linux/module.h>
  30 #include <linux/swap.h>
  31
  32 static struct vfsmount *shm_mnt;
  33
  34 #ifdef CONFIG_SHMEM
  35 /*
  36  * This virtual memory filesystem is heavily based on the ramfs. It
  37  * extends ramfs by the ability to use swap and honor resource limits
  38  * which makes it a completely usable filesystem.
  39  */
  40
  41 #include <linux/xattr.h>
  42 #include <linux/exportfs.h>
  43 #include <linux/generic_acl.h>
  44 #include <linux/mman.h>
  45 #include <linux/pagemap.h>
  46 #include <linux/string.h>
  47 #include <linux/slab.h>
  48 #include <linux/backing-dev.h>
  49 #include <linux/shmem_fs.h>
  50 #include <linux/writeback.h>
  51 #include <linux/vfs.h>
  52 #include <linux/blkdev.h>
  53 #include <linux/security.h>
  54 #include <linux/swapops.h>
  55 #include <linux/mempolicy.h>
  56 #include <linux/namei.h>
  57 #include <linux/ctype.h>
  58 #include <linux/migrate.h>
  59 #include <linux/highmem.h>
  60 #include <linux/seq_file.h>
  61 #include <linux/magic.h>
  62
  63 #include <asm/uaccess.h>
  64 #include <asm/div64.h>
  65 #include <asm/pgtable.h>
  66
  67 #define ENTRIES_PER_PAGE (PAGE_CACHE_SIZE/sizeof(unsigned long))
  68 #define ENTRIES_PER_PAGEPAGE (ENTRIES_PER_PAGE*ENTRIES_PER_PAGE)
  69 #define BLOCKS_PER_PAGE  (PAGE_CACHE_SIZE/512)
  70
  71 #define SHMEM_MAX_INDEX  (SHMEM_NR_DIRECT + (ENTRIES_PER_PAGEPAGE/2) * (ENTRIES_PER_PAGE+1))
  72 #define SHMEM_MAX_BYTES  ((unsigned long long)SHMEM_MAX_INDEX << PAGE_CACHE_SHIFT)
  73
  74 #define VM_ACCT(size)    (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
  75
  76 /* info->flags needs VM_flags to handle pagein/truncate races efficiently */
  77 #define SHMEM_PAGEIN     VM_READ
  78 #define SHMEM_TRUNCATE   VM_WRITE
  79
  80 /* Definition to limit shmem_truncate's steps between cond_rescheds */
  81 #define LATENCY_LIMIT    64
  82
  83 /* Pretend that each entry is of this size in directory's i_size */
  84 #define BOGO_DIRENT_SIZE 20
  85
  86 /* Flag allocation requirements to shmem_getpage and shmem_swp_alloc */
  87 enum sgp_type {
  88         SGP_READ,       /* don't exceed i_size, don't allocate page */
  89         SGP_CACHE,      /* don't exceed i_size, may allocate page */
  90         SGP_DIRTY,      /* like SGP_CACHE, but set new page dirty */
  91         SGP_WRITE,      /* may exceed i_size, may allocate page */
  92 };
  93
  94 #ifdef CONFIG_TMPFS
  95 static unsigned long shmem_default_max_blocks(void)
  96 {
  97         return totalram_pages / 2;
  98 }
  99
 100 static unsigned long shmem_default_max_inodes(void)
 101 {
 102         return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
 103 }
 104 #endif
 105
 106 static int shmem_getpage(struct inode *inode, unsigned long idx,
 107                          struct page **pagep, enum sgp_type sgp, int *type);
 108
 109 static inline struct page *shmem_dir_alloc(gfp_t gfp_mask)
 110 {
 111         /*
 112          * The above definition of ENTRIES_PER_PAGE, and the use of
 113          * BLOCKS_PER_PAGE on indirect pages, assume PAGE_CACHE_SIZE:
 114          * might be reconsidered if it ever diverges from PAGE_SIZE.
 115          *
 116          * Mobility flags are masked out as swap vectors cannot move
 117          */
 118         return alloc_pages((gfp_mask & ~GFP_MOVABLE_MASK) | __GFP_ZERO,
 119                                 PAGE_CACHE_SHIFT-PAGE_SHIFT);
 120 }
 121
 122 static inline void shmem_dir_free(struct page *page)
 123 {
 124         __free_pages(page, PAGE_CACHE_SHIFT-PAGE_SHIFT);
 125 }
 126
 127 static struct page **shmem_dir_map(struct page *page)
 128 {
 129         return (struct page **)kmap_atomic(page, KM_USER0);
 130 }
 131
 132 static inline void shmem_dir_unmap(struct page **dir)
 133 {
 134         kunmap_atomic(dir, KM_USER0);
 135 }
 136
 137 static swp_entry_t *shmem_swp_map(struct page *page)
 138 {
 139         return (swp_entry_t *)kmap_atomic(page, KM_USER1);
 140 }
 141
 142 static inline void shmem_swp_balance_unmap(void)
 143 {
 144         /*
 145          * When passing a pointer to an i_direct entry, to code which
 146          * also handles indirect entries and so will shmem_swp_unmap,
 147          * we must arrange for the preempt count to remain in balance.
 148          * What kmap_atomic of a lowmem page does depends on config
 149          * and architecture, so pretend to kmap_atomic some lowmem page.
 150          */
 151         (void) kmap_atomic(ZERO_PAGE(0), KM_USER1);
 152 }
 153
 154 static inline void shmem_swp_unmap(swp_entry_t *entry)
 155 {
 156         kunmap_atomic(entry, KM_USER1);
 157 }
 158
 159 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
 160 {
 161         return sb->s_fs_info;
 162 }
 163
 164 /*
 165  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
 166  * for shared memory and for shared anonymous (/dev/zero) mappings
 167  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
 168  * consistent with the pre-accounting of private mappings ...
 169  */
 170 static inline int shmem_acct_size(unsigned long flags, loff_t size)
 171 {
 172         return (flags & VM_ACCOUNT) ?
 173                 security_vm_enough_memory_kern(VM_ACCT(size)) : 0;
 174 }
 175
 176 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
 177 {
 178         if (flags & VM_ACCOUNT)
 179                 vm_unacct_memory(VM_ACCT(size));
 180 }
 181
 182 /*
 183  * ... whereas tmpfs objects are accounted incrementally as
 184  * pages are allocated, in order to allow huge sparse files.
 185  * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
 186  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
 187  */
 188 static inline int shmem_acct_block(unsigned long flags)
 189 {
 190         return (flags & VM_ACCOUNT) ?
 191                 0 : security_vm_enough_memory_kern(VM_ACCT(PAGE_CACHE_SIZE));
 192 }
 193
 194 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
 195 {
 196         if (!(flags & VM_ACCOUNT))
 197                 vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
 198 }
 199
 200 static const struct super_operations shmem_ops;
 201 static const struct address_space_operations shmem_aops;
 202 static const struct file_operations shmem_file_operations;
 203 static const struct inode_operations shmem_inode_operations;
 204 static const struct inode_operations shmem_dir_inode_operations;
 205 static const struct inode_operations shmem_special_inode_operations;
 206 static struct vm_operations_struct shmem_vm_ops;
 207
 208 static struct backing_dev_info shmem_backing_dev_info  __read_mostly = {
 209         .ra_pages       = 0,    /* No readahead */
 210         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
 211         .unplug_io_fn   = default_unplug_io_fn,
 212 };
 213
 214 static LIST_HEAD(shmem_swaplist);
 215 static DEFINE_MUTEX(shmem_swaplist_mutex);
 216
 217 static void shmem_free_blocks(struct inode *inode, long pages)
 218 {
 219         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 220         if (sbinfo->max_blocks) {
 221                 spin_lock(&sbinfo->stat_lock);
 222                 sbinfo->free_blocks += pages;
 223                 inode->i_blocks -= pages*BLOCKS_PER_PAGE;
 224                 spin_unlock(&sbinfo->stat_lock);
 225         }
 226 }
 227
 228 static int shmem_reserve_inode(struct super_block *sb)
 229 {
 230         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
 231         if (sbinfo->max_inodes) {
 232                 spin_lock(&sbinfo->stat_lock);
 233                 if (!sbinfo->free_inodes) {
 234                         spin_unlock(&sbinfo->stat_lock);
 235                         return -ENOSPC;
 236                 }
 237                 sbinfo->free_inodes--;
 238                 spin_unlock(&sbinfo->stat_lock);
 239         }
 240         return 0;
 241 }
 242
 243 static void shmem_free_inode(struct super_block *sb)
 244 {
 245         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
 246         if (sbinfo->max_inodes) {
 247                 spin_lock(&sbinfo->stat_lock);
 248                 sbinfo->free_inodes++;
 249                 spin_unlock(&sbinfo->stat_lock);
 250         }
 251 }
 252
 253 /**
 254  * shmem_recalc_inode - recalculate the size of an inode
 255  * @inode: inode to recalc
 256  *
 257  * We have to calculate the free blocks since the mm can drop
 258  * undirtied hole pages behind our back.
 259  *
 260  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
 261  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
 262  *
 263  * It has to be called with the spinlock held.
 264  */
 265 static void shmem_recalc_inode(struct inode *inode)
 266 {
 267         struct shmem_inode_info *info = SHMEM_I(inode);
 268         long freed;
 269
 270         freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
 271         if (freed > 0) {
 272                 info->alloced -= freed;
 273                 shmem_unacct_blocks(info->flags, freed);
 274                 shmem_free_blocks(inode, freed);
 275         }
 276 }
 277
 278 /**
 279  * shmem_swp_entry - find the swap vector position in the info structure
 280  * @info:  info structure for the inode
 281  * @index: index of the page to find
 282  * @page:  optional page to add to the structure. Has to be preset to
 283  *         all zeros
 284  *
 285  * If there is no space allocated yet it will return NULL when
 286  * page is NULL, else it will use the page for the needed block,
 287  * setting it to NULL on return to indicate that it has been used.
 288  *
 289  * The swap vector is organized the following way:
 290  *
 291  * There are SHMEM_NR_DIRECT entries directly stored in the
 292  * shmem_inode_info structure. So small files do not need an addional
 293  * allocation.
 294  *
 295  * For pages with index > SHMEM_NR_DIRECT there is the pointer
 296  * i_indirect which points to a page which holds in the first half
 297  * doubly indirect blocks, in the second half triple indirect blocks:
 298  *
 299  * For an artificial ENTRIES_PER_PAGE = 4 this would lead to the
 300  * following layout (for SHMEM_NR_DIRECT == 16):
 301  *
 302  * i_indirect -> dir --> 16-19
 303  *            |      +-> 20-23
 304  *            |
 305  *            +-->dir2 --> 24-27
 306  *            |        +-> 28-31
 307  *            |        +-> 32-35
 308  *            |        +-> 36-39
 309  *            |
 310  *            +-->dir3 --> 40-43
 311  *                     +-> 44-47
 312  *                     +-> 48-51
 313  *                     +-> 52-55
 314  */
 315 static swp_entry_t *shmem_swp_entry(struct shmem_inode_info *info, unsigned long index, struct page **page)
 316 {
 317         unsigned long offset;
 318         struct page **dir;
 319         struct page *subdir;
 320
 321         if (index < SHMEM_NR_DIRECT) {
 322                 shmem_swp_balance_unmap();
 323                 return info->i_direct+index;
 324         }
 325         if (!info->i_indirect) {
 326                 if (page) {
 327                         info->i_indirect = *page;
 328                         *page = NULL;
 329                 }
 330                 return NULL;                    /* need another page */
 331         }
 332
 333         index -= SHMEM_NR_DIRECT;
 334         offset = index % ENTRIES_PER_PAGE;
 335         index /= ENTRIES_PER_PAGE;
 336         dir = shmem_dir_map(info->i_indirect);
 337
 338         if (index >= ENTRIES_PER_PAGE/2) {
 339                 index -= ENTRIES_PER_PAGE/2;
 340                 dir += ENTRIES_PER_PAGE/2 + index/ENTRIES_PER_PAGE;
 341                 index %= ENTRIES_PER_PAGE;
 342                 subdir = *dir;
 343                 if (!subdir) {
 344                         if (page) {
 345                                 *dir = *page;
 346                                 *page = NULL;
 347                         }
 348                         shmem_dir_unmap(dir);
 349                         return NULL;            /* need another page */
 350                 }
 351                 shmem_dir_unmap(dir);
 352                 dir = shmem_dir_map(subdir);
 353         }
 354
 355         dir += index;
 356         subdir = *dir;
 357         if (!subdir) {
 358                 if (!page || !(subdir = *page)) {
 359                         shmem_dir_unmap(dir);
 360                         return NULL;            /* need a page */
 361                 }
 362                 *dir = subdir;
 363                 *page = NULL;
 364         }
 365         shmem_dir_unmap(dir);
 366         return shmem_swp_map(subdir) + offset;
 367 }
 368
 369 static void shmem_swp_set(struct shmem_inode_info *info, swp_entry_t *entry, unsigned long value)
 370 {
 371         long incdec = value? 1: -1;
 372
 373         entry->val = value;
 374         info->swapped += incdec;
 375         if ((unsigned long)(entry - info->i_direct) >= SHMEM_NR_DIRECT) {
 376                 struct page *page = kmap_atomic_to_page(entry);
 377                 set_page_private(page, page_private(page) + incdec);
 378         }
 379 }
 380
 381 /**
 382  * shmem_swp_alloc - get the position of the swap entry for the page.
 383  * @info:       info structure for the inode
 384  * @index:      index of the page to find
 385  * @sgp:        check and recheck i_size? skip allocation?
 386  *
 387  * If the entry does not exist, allocate it.
 388  */
 389 static swp_entry_t *shmem_swp_alloc(struct shmem_inode_info *info, unsigned long index, enum sgp_type sgp)
 390 {
 391         struct inode *inode = &info->vfs_inode;
 392         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 393         struct page *page = NULL;
 394         swp_entry_t *entry;
 395
 396         if (sgp != SGP_WRITE &&
 397             ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode))
 398                 return ERR_PTR(-EINVAL);
 399
 400         while (!(entry = shmem_swp_entry(info, index, &page))) {
 401                 if (sgp == SGP_READ)
 402                         return shmem_swp_map(ZERO_PAGE(0));
 403                 /*
 404                  * Test free_blocks against 1 not 0, since we have 1 data
 405                  * page (and perhaps indirect index pages) yet to allocate:
 406                  * a waste to allocate index if we cannot allocate data.
 407                  */
 408                 if (sbinfo->max_blocks) {
 409                         spin_lock(&sbinfo->stat_lock);
 410                         if (sbinfo->free_blocks <= 1) {
 411                                 spin_unlock(&sbinfo->stat_lock);
 412                                 return ERR_PTR(-ENOSPC);
 413                         }
 414                         sbinfo->free_blocks--;
 415                         inode->i_blocks += BLOCKS_PER_PAGE;
 416                         spin_unlock(&sbinfo->stat_lock);
 417                 }
 418
 419                 spin_unlock(&info->lock);
 420                 page = shmem_dir_alloc(mapping_gfp_mask(inode->i_mapping));
 421                 if (page)
 422                         set_page_private(page, 0);
 423                 spin_lock(&info->lock);
 424
 425                 if (!page) {
 426                         shmem_free_blocks(inode, 1);
 427                         return ERR_PTR(-ENOMEM);
 428                 }
 429                 if (sgp != SGP_WRITE &&
 430                     ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
 431                         entry = ERR_PTR(-EINVAL);
 432                         break;
 433                 }
 434                 if (info->next_index <= index)
 435                         info->next_index = index + 1;
 436         }
 437         if (page) {
 438                 /* another task gave its page, or truncated the file */
 439                 shmem_free_blocks(inode, 1);
 440                 shmem_dir_free(page);
 441         }
 442         if (info->next_index <= index && !IS_ERR(entry))
 443                 info->next_index = index + 1;
 444         return entry;
 445 }
 446
 447 /**
 448  * shmem_free_swp - free some swap entries in a directory
 449  * @dir:        pointer to the directory
 450  * @edir:       pointer after last entry of the directory
 451  * @punch_lock: pointer to spinlock when needed for the holepunch case
 452  */
 453 static int shmem_free_swp(swp_entry_t *dir, swp_entry_t *edir,
 454                                                 spinlock_t *punch_lock)
 455 {
 456         spinlock_t *punch_unlock = NULL;
 457         swp_entry_t *ptr;
 458         int freed = 0;
 459
 460         for (ptr = dir; ptr < edir; ptr++) {
 461                 if (ptr->val) {
 462                         if (unlikely(punch_lock)) {
 463                                 punch_unlock = punch_lock;
 464                                 punch_lock = NULL;
 465                                 spin_lock(punch_unlock);
 466                                 if (!ptr->val)
 467                                         continue;
 468                         }
 469                         free_swap_and_cache(*ptr);
 470                         *ptr = (swp_entry_t){0};
 471                         freed++;
 472                 }
 473         }
 474         if (punch_unlock)
 475                 spin_unlock(punch_unlock);
 476         return freed;
 477 }
 478
 479 static int shmem_map_and_free_swp(struct page *subdir, int offset,
 480                 int limit, struct page ***dir, spinlock_t *punch_lock)
 481 {
 482         swp_entry_t *ptr;
 483         int freed = 0;
 484
 485         ptr = shmem_swp_map(subdir);
 486         for (; offset < limit; offset += LATENCY_LIMIT) {
 487                 int size = limit - offset;
 488                 if (size > LATENCY_LIMIT)
 489                         size = LATENCY_LIMIT;
 490                 freed += shmem_free_swp(ptr+offset, ptr+offset+size,
 491                                                         punch_lock);
 492                 if (need_resched()) {
 493                         shmem_swp_unmap(ptr);
 494                         if (*dir) {
 495                                 shmem_dir_unmap(*dir);
 496                                 *dir = NULL;
 497                         }
 498                         cond_resched();
 499                         ptr = shmem_swp_map(subdir);
 500                 }
 501         }
 502         shmem_swp_unmap(ptr);
 503         return freed;
 504 }
 505
 506 static void shmem_free_pages(struct list_head *next)
 507 {
 508         struct page *page;
 509         int freed = 0;
 510
 511         do {
 512                 page = container_of(next, struct page, lru);
 513                 next = next->next;
 514                 shmem_dir_free(page);
 515                 freed++;
 516                 if (freed >= LATENCY_LIMIT) {
 517                         cond_resched();
 518                         freed = 0;
 519                 }
 520         } while (next);
 521 }
 522
 523 static void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end)
 524 {
 525         struct shmem_inode_info *info = SHMEM_I(inode);
 526         unsigned long idx;
 527         unsigned long size;
 528         unsigned long limit;
 529         unsigned long stage;
 530         unsigned long diroff;
 531         struct page **dir;
 532         struct page *topdir;
 533         struct page *middir;
 534         struct page *subdir;
 535         swp_entry_t *ptr;
 536         LIST_HEAD(pages_to_free);
 537         long nr_pages_to_free = 0;
 538         long nr_swaps_freed = 0;
 539         int offset;
 540         int freed;
 541         int punch_hole;
 542         spinlock_t *needs_lock;
 543         spinlock_t *punch_lock;
 544         unsigned long upper_limit;
 545
 546         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
 547         idx = (start + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 548         if (idx >= info->next_index)
 549                 return;
 550
 551         spin_lock(&info->lock);
 552         info->flags |= SHMEM_TRUNCATE;
 553         if (likely(end == (loff_t) -1)) {
 554                 limit = info->next_index;
 555                 upper_limit = SHMEM_MAX_INDEX;
 556                 info->next_index = idx;
 557                 needs_lock = NULL;
 558                 punch_hole = 0;
 559         } else {
 560                 if (end + 1 >= inode->i_size) { /* we may free a little more */
 561                         limit = (inode->i_size + PAGE_CACHE_SIZE - 1) >>
 562                                                         PAGE_CACHE_SHIFT;
 563                         upper_limit = SHMEM_MAX_INDEX;
 564                 } else {
 565                         limit = (end + 1) >> PAGE_CACHE_SHIFT;
 566                         upper_limit = limit;
 567                 }
 568                 needs_lock = &info->lock;
 569                 punch_hole = 1;
 570         }
 571
 572         topdir = info->i_indirect;
 573         if (topdir && idx <= SHMEM_NR_DIRECT && !punch_hole) {
 574                 info->i_indirect = NULL;
 575                 nr_pages_to_free++;
 576                 list_add(&topdir->lru, &pages_to_free);
 577         }
 578         spin_unlock(&info->lock);
 579
 580         if (info->swapped && idx < SHMEM_NR_DIRECT) {
 581                 ptr = info->i_direct;
 582                 size = limit;
 583                 if (size > SHMEM_NR_DIRECT)
 584                         size = SHMEM_NR_DIRECT;
 585                 nr_swaps_freed = shmem_free_swp(ptr+idx, ptr+size, needs_lock);
 586         }
 587
 588         /*
 589          * If there are no indirect blocks or we are punching a hole
 590          * below indirect blocks, nothing to be done.
 591          */
 592         if (!topdir || limit <= SHMEM_NR_DIRECT)
 593                 goto done2;
 594
 595         /*
 596          * The truncation case has already dropped info->lock, and we're safe
 597          * because i_size and next_index have already been lowered, preventing
 598          * access beyond.  But in the punch_hole case, we still need to take
 599          * the lock when updating the swap directory, because there might be
 600          * racing accesses by shmem_getpage(SGP_CACHE), shmem_unuse_inode or
 601          * shmem_writepage.  However, whenever we find we can remove a whole
 602          * directory page (not at the misaligned start or end of the range),
 603          * we first NULLify its pointer in the level above, and then have no
 604          * need to take the lock when updating its contents: needs_lock and
 605          * punch_lock (either pointing to info->lock or NULL) manage this.
 606          */
 607
 608         upper_limit -= SHMEM_NR_DIRECT;
 609         limit -= SHMEM_NR_DIRECT;
 610         idx = (idx > SHMEM_NR_DIRECT)? (idx - SHMEM_NR_DIRECT): 0;
 611         offset = idx % ENTRIES_PER_PAGE;
 612         idx -= offset;
 613
 614         dir = shmem_dir_map(topdir);
 615         stage = ENTRIES_PER_PAGEPAGE/2;
 616         if (idx < ENTRIES_PER_PAGEPAGE/2) {
 617                 middir = topdir;
 618                 diroff = idx/ENTRIES_PER_PAGE;
 619         } else {
 620                 dir += ENTRIES_PER_PAGE/2;
 621                 dir += (idx - ENTRIES_PER_PAGEPAGE/2)/ENTRIES_PER_PAGEPAGE;
 622                 while (stage <= idx)
 623                         stage += ENTRIES_PER_PAGEPAGE;
 624                 middir = *dir;
 625                 if (*dir) {
 626                         diroff = ((idx - ENTRIES_PER_PAGEPAGE/2) %
 627                                 ENTRIES_PER_PAGEPAGE) / ENTRIES_PER_PAGE;
 628                         if (!diroff && !offset && upper_limit >= stage) {
 629                                 if (needs_lock) {
 630                                         spin_lock(needs_lock);
 631                                         *dir = NULL;
 632                                         spin_unlock(needs_lock);
 633                                         needs_lock = NULL;
 634                                 } else
 635                                         *dir = NULL;
 636                                 nr_pages_to_free++;
 637                                 list_add(&middir->lru, &pages_to_free);
 638                         }
 639                         shmem_dir_unmap(dir);
 640                         dir = shmem_dir_map(middir);
 641                 } else {
 642                         diroff = 0;
 643                         offset = 0;
 644                         idx = stage;
 645                 }
 646         }
 647
 648         for (; idx < limit; idx += ENTRIES_PER_PAGE, diroff++) {
 649                 if (unlikely(idx == stage)) {
 650                         shmem_dir_unmap(dir);
 651                         dir = shmem_dir_map(topdir) +
 652                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
 653                         while (!*dir) {
 654                                 dir++;
 655                                 idx += ENTRIES_PER_PAGEPAGE;
 656                                 if (idx >= limit)
 657                                         goto done1;
 658                         }
 659                         stage = idx + ENTRIES_PER_PAGEPAGE;
 660                         middir = *dir;
 661                         if (punch_hole)
 662                                 needs_lock = &info->lock;
 663                         if (upper_limit >= stage) {
 664                                 if (needs_lock) {
 665                                         spin_lock(needs_lock);
 666                                         *dir = NULL;
 667                                         spin_unlock(needs_lock);
 668                                         needs_lock = NULL;
 669                                 } else
 670                                         *dir = NULL;
 671                                 nr_pages_to_free++;
 672                                 list_add(&middir->lru, &pages_to_free);
 673                         }
 674                         shmem_dir_unmap(dir);
 675                         cond_resched();
 676                         dir = shmem_dir_map(middir);
 677                         diroff = 0;
 678                 }
 679                 punch_lock = needs_lock;
 680                 subdir = dir[diroff];
 681                 if (subdir && !offset && upper_limit-idx >= ENTRIES_PER_PAGE) {
 682                         if (needs_lock) {
 683                                 spin_lock(needs_lock);
 684                                 dir[diroff] = NULL;
 685                                 spin_unlock(needs_lock);
 686                                 punch_lock = NULL;
 687                         } else
 688                                 dir[diroff] = NULL;
 689                         nr_pages_to_free++;
 690                         list_add(&subdir->lru, &pages_to_free);
 691                 }
 692                 if (subdir && page_private(subdir) /* has swap entries */) {
 693                         size = limit - idx;
 694                         if (size > ENTRIES_PER_PAGE)
 695                                 size = ENTRIES_PER_PAGE;
 696                         freed = shmem_map_and_free_swp(subdir,
 697                                         offset, size, &dir, punch_lock);
 698                         if (!dir)
 699                                 dir = shmem_dir_map(middir);
 700                         nr_swaps_freed += freed;
 701                         if (offset || punch_lock) {
 702                                 spin_lock(&info->lock);
 703                                 set_page_private(subdir,
 704                                         page_private(subdir) - freed);
 705                                 spin_unlock(&info->lock);
 706                         } else
 707                                 BUG_ON(page_private(subdir) != freed);
 708                 }
 709                 offset = 0;
 710         }
 711 done1:
 712         shmem_dir_unmap(dir);
 713 done2:
 714         if (inode->i_mapping->nrpages && (info->flags & SHMEM_PAGEIN)) {
 715                 /*
 716                  * Call truncate_inode_pages again: racing shmem_unuse_inode
 717                  * may have swizzled a page in from swap since vmtruncate or
 718                  * generic_delete_inode did it, before we lowered next_index.
 719                  * Also, though shmem_getpage checks i_size before adding to
 720                  * cache, no recheck after: so fix the narrow window there too.
 721                  *
 722                  * Recalling truncate_inode_pages_range and unmap_mapping_range
 723                  * every time for punch_hole (which never got a chance to clear
 724                  * SHMEM_PAGEIN at the start of vmtruncate_range) is expensive,
 725                  * yet hardly ever necessary: try to optimize them out later.
 726                  */
 727                 truncate_inode_pages_range(inode->i_mapping, start, end);
 728                 if (punch_hole)
 729                         unmap_mapping_range(inode->i_mapping, start,
 730                                                         end - start, 1);
 731         }
 732
 733         spin_lock(&info->lock);
 734         info->flags &= ~SHMEM_TRUNCATE;
 735         info->swapped -= nr_swaps_freed;
 736         if (nr_pages_to_free)
 737                 shmem_free_blocks(inode, nr_pages_to_free);
 738         shmem_recalc_inode(inode);
 739         spin_unlock(&info->lock);
 740
 741         /*
 742          * Empty swap vector directory pages to be freed?
 743          */
 744         if (!list_empty(&pages_to_free)) {
 745                 pages_to_free.prev->next = NULL;
 746                 shmem_free_pages(pages_to_free.next);
 747         }
 748 }
 749
 750 static void shmem_truncate(struct inode *inode)
 751 {
 752         shmem_truncate_range(inode, inode->i_size, (loff_t)-1);
 753 }
 754
 755 static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
 756 {
 757         struct inode *inode = dentry->d_inode;
 758         struct page *page = NULL;
 759         int error;
 760
 761         if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
 762                 if (attr->ia_size < inode->i_size) {
 763                         /*
 764                          * If truncating down to a partial page, then
 765                          * if that page is already allocated, hold it
 766                          * in memory until the truncation is over, so
 767                          * truncate_partial_page cannnot miss it were
 768                          * it assigned to swap.
 769                          */
 770                         if (attr->ia_size & (PAGE_CACHE_SIZE-1)) {
 771                                 (void) shmem_getpage(inode,
 772                                         attr->ia_size>>PAGE_CACHE_SHIFT,
 773                                                 &page, SGP_READ, NULL);
 774                                 if (page)
 775                                         unlock_page(page);
 776                         }
 777                         /*
 778                          * Reset SHMEM_PAGEIN flag so that shmem_truncate can
 779                          * detect if any pages might have been added to cache
 780                          * after truncate_inode_pages.  But we needn't bother
 781                          * if it's being fully truncated to zero-length: the
 782                          * nrpages check is efficient enough in that case.
 783                          */
 784                         if (attr->ia_size) {
 785                                 struct shmem_inode_info *info = SHMEM_I(inode);
 786                                 spin_lock(&info->lock);
 787                                 info->flags &= ~SHMEM_PAGEIN;
 788                                 spin_unlock(&info->lock);
 789                         }
 790                 }
 791         }
 792
 793         error = inode_change_ok(inode, attr);
 794         if (!error)
 795                 error = inode_setattr(inode, attr);
 796 #ifdef CONFIG_TMPFS_POSIX_ACL
 797         if (!error && (attr->ia_valid & ATTR_MODE))
 798                 error = generic_acl_chmod(inode, &shmem_acl_ops);
 799 #endif
 800         if (page)
 801                 page_cache_release(page);
 802         return error;
 803 }
 804
 805 static void shmem_delete_inode(struct inode *inode)
 806 {
 807         struct shmem_inode_info *info = SHMEM_I(inode);
 808
 809         if (inode->i_op->truncate == shmem_truncate) {
 810                 truncate_inode_pages(inode->i_mapping, 0);
 811                 shmem_unacct_size(info->flags, inode->i_size);
 812                 inode->i_size = 0;
 813                 shmem_truncate(inode);
 814                 if (!list_empty(&info->swaplist)) {
 815                         mutex_lock(&shmem_swaplist_mutex);
 816                         list_del_init(&info->swaplist);
 817                         mutex_unlock(&shmem_swaplist_mutex);
 818                 }
 819         }
 820         BUG_ON(inode->i_blocks);
 821         shmem_free_inode(inode->i_sb);
 822         clear_inode(inode);
 823 }
 824
 825 static inline int shmem_find_swp(swp_entry_t entry, swp_entry_t *dir, swp_entry_t *edir)
 826 {
 827         swp_entry_t *ptr;
 828
 829         for (ptr = dir; ptr < edir; ptr++) {
 830                 if (ptr->val == entry.val)
 831                         return ptr - dir;
 832         }
 833         return -1;
 834 }
 835
 836 static int shmem_unuse_inode(struct shmem_inode_info *info, swp_entry_t entry, struct page *page)
 837 {
 838         struct inode *inode;
 839         unsigned long idx;
 840         unsigned long size;
 841         unsigned long limit;
 842         unsigned long stage;
 843         struct page **dir;
 844         struct page *subdir;
 845         swp_entry_t *ptr;
 846         int offset;
 847         int error;
 848
 849         idx = 0;
 850         ptr = info->i_direct;
 851         spin_lock(&info->lock);
 852         if (!info->swapped) {
 853                 list_del_init(&info->swaplist);
 854                 goto lost2;
 855         }
 856         limit = info->next_index;
 857         size = limit;
 858         if (size > SHMEM_NR_DIRECT)
 859                 size = SHMEM_NR_DIRECT;
 860         offset = shmem_find_swp(entry, ptr, ptr+size);
 861         if (offset >= 0)
 862                 goto found;
 863         if (!info->i_indirect)
 864                 goto lost2;
 865
 866         dir = shmem_dir_map(info->i_indirect);
 867         stage = SHMEM_NR_DIRECT + ENTRIES_PER_PAGEPAGE/2;
 868
 869         for (idx = SHMEM_NR_DIRECT; idx < limit; idx += ENTRIES_PER_PAGE, dir++) {
 870                 if (unlikely(idx == stage)) {
 871                         shmem_dir_unmap(dir-1);
 872                         if (cond_resched_lock(&info->lock)) {
 873                                 /* check it has not been truncated */
 874                                 if (limit > info->next_index) {
 875                                         limit = info->next_index;
 876                                         if (idx >= limit)
 877                                                 goto lost2;
 878                                 }
 879                         }
 880                         dir = shmem_dir_map(info->i_indirect) +
 881                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
 882                         while (!*dir) {
 883                                 dir++;
 884                                 idx += ENTRIES_PER_PAGEPAGE;
 885                                 if (idx >= limit)
 886                                         goto lost1;
 887                         }
 888                         stage = idx + ENTRIES_PER_PAGEPAGE;
 889                         subdir = *dir;
 890                         shmem_dir_unmap(dir);
 891                         dir = shmem_dir_map(subdir);
 892                 }
 893                 subdir = *dir;
 894                 if (subdir && page_private(subdir)) {
 895                         ptr = shmem_swp_map(subdir);
 896                         size = limit - idx;
 897                         if (size > ENTRIES_PER_PAGE)
 898                                 size = ENTRIES_PER_PAGE;
 899                         offset = shmem_find_swp(entry, ptr, ptr+size);
 900                         shmem_swp_unmap(ptr);
 901                         if (offset >= 0) {
 902                                 shmem_dir_unmap(dir);
 903                                 goto found;
 904                         }
 905                 }
 906         }
 907 lost1:
 908         shmem_dir_unmap(dir-1);
 909 lost2:
 910         spin_unlock(&info->lock);
 911         return 0;
 912 found:
 913         idx += offset;
 914         inode = igrab(&info->vfs_inode);
 915         spin_unlock(&info->lock);
 916
 917         /*
 918          * Move _head_ to start search for next from here.
 919          * But be careful: shmem_delete_inode checks list_empty without taking
 920          * mutex, and there's an instant in list_move_tail when info->swaplist
 921          * would appear empty, if it were the only one on shmem_swaplist.  We
 922          * could avoid doing it if inode NULL; or use this minor optimization.
 923          */
 924         if (shmem_swaplist.next != &info->swaplist)
 925                 list_move_tail(&shmem_swaplist, &info->swaplist);
 926         mutex_unlock(&shmem_swaplist_mutex);
 927
 928         error = 1;
 929         if (!inode)
 930                 goto out;
 931         /*
 932          * Charge page using GFP_KERNEL while we can wait.
 933          * Charged back to the user(not to caller) when swap account is used.
 934          * add_to_page_cache() will be called with GFP_NOWAIT.
 935          */
 936         error = mem_cgroup_cache_charge(page, current->mm, GFP_KERNEL);
 937         if (error)
 938                 goto out;
 939         error = radix_tree_preload(GFP_KERNEL);
 940         if (error) {
 941                 mem_cgroup_uncharge_cache_page(page);
 942                 goto out;
 943         }
 944         error = 1;
 945
 946         spin_lock(&info->lock);
 947         ptr = shmem_swp_entry(info, idx, NULL);
 948         if (ptr && ptr->val == entry.val) {
 949                 error = add_to_page_cache_locked(page, inode->i_mapping,
 950                                                 idx, GFP_NOWAIT);
 951                 /* does mem_cgroup_uncharge_cache_page on error */
 952         } else  /* we must compensate for our precharge above */
 953                 mem_cgroup_uncharge_cache_page(page);
 954
 955         if (error == -EEXIST) {
 956                 struct page *filepage = find_get_page(inode->i_mapping, idx);
 957                 error = 1;
 958                 if (filepage) {
 959                         /*
 960                          * There might be a more uptodate page coming down
 961                          * from a stacked writepage: forget our swappage if so.
 962                          */
 963                         if (PageUptodate(filepage))
 964                                 error = 0;
 965                         page_cache_release(filepage);
 966                 }
 967         }
 968         if (!error) {
 969                 delete_from_swap_cache(page);
 970                 set_page_dirty(page);
 971                 info->flags |= SHMEM_PAGEIN;
 972                 shmem_swp_set(info, ptr, 0);
 973                 swap_free(entry);
 974                 error = 1;      /* not an error, but entry was found */
 975         }
 976         if (ptr)
 977                 shmem_swp_unmap(ptr);
 978         spin_unlock(&info->lock);
 979         radix_tree_preload_end();
 980 out:
 981         unlock_page(page);
 982         page_cache_release(page);
 983         iput(inode);            /* allows for NULL */
 984         return error;
 985 }
 986
 987 /*
 988  * shmem_unuse() search for an eventually swapped out shmem page.
 989  */
 990 int shmem_unuse(swp_entry_t entry, struct page *page)
 991 {
 992         struct list_head *p, *next;
 993         struct shmem_inode_info *info;
 994         int found = 0;
 995
 996         mutex_lock(&shmem_swaplist_mutex);
 997         list_for_each_safe(p, next, &shmem_swaplist) {
 998                 info = list_entry(p, struct shmem_inode_info, swaplist);
 999                 found = shmem_unuse_inode(info, entry, page);
1000                 cond_resched();
1001                 if (found)
1002                         goto out;
1003         }
1004         mutex_unlock(&shmem_swaplist_mutex);
1005 out:    return found;   /* 0 or 1 or -ENOMEM */
1006 }
1007
1008 /*
1009  * Move the page from the page cache to the swap cache.
1010  */
1011 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
1012 {
1013         struct shmem_inode_info *info;
1014         swp_entry_t *entry, swap;
1015         struct address_space *mapping;
1016         unsigned long index;
1017         struct inode *inode;
1018
1019         BUG_ON(!PageLocked(page));
1020         mapping = page->mapping;
1021         index = page->index;
1022         inode = mapping->host;
1023         info = SHMEM_I(inode);
1024         if (info->flags & VM_LOCKED)
1025                 goto redirty;
1026         if (!total_swap_pages)
1027                 goto redirty;
1028
1029         /*
1030          * shmem_backing_dev_info's capabilities prevent regular writeback or
1031          * sync from ever calling shmem_writepage; but a stacking filesystem
1032          * may use the ->writepage of its underlying filesystem, in which case
1033          * tmpfs should write out to swap only in response to memory pressure,
1034          * and not for pdflush or sync.  However, in those cases, we do still
1035          * want to check if there's a redundant swappage to be discarded.
1036          */
1037         if (wbc->for_reclaim)
1038                 swap = get_swap_page();
1039         else
1040                 swap.val = 0;
1041
1042         spin_lock(&info->lock);
1043         if (index >= info->next_index) {
1044                 BUG_ON(!(info->flags & SHMEM_TRUNCATE));
1045                 goto unlock;
1046         }
1047         entry = shmem_swp_entry(info, index, NULL);
1048         if (entry->val) {
1049                 /*
1050                  * The more uptodate page coming down from a stacked
1051                  * writepage should replace our old swappage.
1052                  */
1053                 free_swap_and_cache(*entry);
1054                 shmem_swp_set(info, entry, 0);
1055         }
1056         shmem_recalc_inode(inode);
1057
1058         if (swap.val && add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
1059                 remove_from_page_cache(page);
1060                 shmem_swp_set(info, entry, swap.val);
1061                 shmem_swp_unmap(entry);
1062                 if (list_empty(&info->swaplist))
1063                         inode = igrab(inode);
1064                 else
1065                         inode = NULL;
1066                 spin_unlock(&info->lock);
1067                 swap_duplicate(swap);
1068                 BUG_ON(page_mapped(page));
1069                 page_cache_release(page);       /* pagecache ref */
1070                 set_page_dirty(page);
1071                 unlock_page(page);
1072                 if (inode) {
1073                         mutex_lock(&shmem_swaplist_mutex);
1074                         /* move instead of add in case we're racing */
1075                         list_move_tail(&info->swaplist, &shmem_swaplist);
1076                         mutex_unlock(&shmem_swaplist_mutex);
1077                         iput(inode);
1078                 }
1079                 return 0;
1080         }
1081
1082         shmem_swp_unmap(entry);
1083 unlock:
1084         spin_unlock(&info->lock);
1085         swap_free(swap);
1086 redirty:
1087         set_page_dirty(page);
1088         if (wbc->for_reclaim)
1089                 return AOP_WRITEPAGE_ACTIVATE;  /* Return with page locked */
1090         unlock_page(page);
1091         return 0;
1092 }
1093
1094 #ifdef CONFIG_NUMA
1095 #ifdef CONFIG_TMPFS
1096 static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
1097 {
1098         char buffer[64];
1099
1100         if (!mpol || mpol->mode == MPOL_DEFAULT)
1101                 return;         /* show nothing */
1102
1103         mpol_to_str(buffer, sizeof(buffer), mpol, 1);
1104
1105         seq_printf(seq, ",mpol=%s", buffer);
1106 }
1107
1108 static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1109 {
1110         struct mempolicy *mpol = NULL;
1111         if (sbinfo->mpol) {
1112                 spin_lock(&sbinfo->stat_lock);  /* prevent replace/use races */
1113                 mpol = sbinfo->mpol;
1114                 mpol_get(mpol);
1115                 spin_unlock(&sbinfo->stat_lock);
1116         }
1117         return mpol;
1118 }
1119 #endif /* CONFIG_TMPFS */
1120
1121 static struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
1122                         struct shmem_inode_info *info, unsigned long idx)
1123 {
1124         struct mempolicy mpol, *spol;
1125         struct vm_area_struct pvma;
1126         struct page *page;
1127
1128         spol = mpol_cond_copy(&mpol,
1129                                 mpol_shared_policy_lookup(&info->policy, idx));
1130
1131         /* Create a pseudo vma that just contains the policy */
1132         pvma.vm_start = 0;
1133         pvma.vm_pgoff = idx;
1134         pvma.vm_ops = NULL;
1135         pvma.vm_policy = spol;
1136         page = swapin_readahead(entry, gfp, &pvma, 0);
1137         return page;
1138 }
1139
1140 static struct page *shmem_alloc_page(gfp_t gfp,
1141                         struct shmem_inode_info *info, unsigned long idx)
1142 {
1143         struct vm_area_struct pvma;
1144
1145         /* Create a pseudo vma that just contains the policy */
1146         pvma.vm_start = 0;
1147         pvma.vm_pgoff = idx;
1148         pvma.vm_ops = NULL;
1149         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx);
1150
1151         /*
1152          * alloc_page_vma() will drop the shared policy reference
1153          */
1154         return alloc_page_vma(gfp, &pvma, 0);
1155 }
1156 #else /* !CONFIG_NUMA */
1157 #ifdef CONFIG_TMPFS
1158 static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *p)
1159 {
1160 }
1161 #endif /* CONFIG_TMPFS */
1162
1163 static inline struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
1164                         struct shmem_inode_info *info, unsigned long idx)
1165 {
1166         return swapin_readahead(entry, gfp, NULL, 0);
1167 }
1168
1169 static inline struct page *shmem_alloc_page(gfp_t gfp,
1170                         struct shmem_inode_info *info, unsigned long idx)
1171 {
1172         return alloc_page(gfp);
1173 }
1174 #endif /* CONFIG_NUMA */
1175
1176 #if !defined(CONFIG_NUMA) || !defined(CONFIG_TMPFS)
1177 static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1178 {
1179         return NULL;
1180 }
1181 #endif
1182
1183 /*
1184  * shmem_getpage - either get the page from swap or allocate a new one
1185  *
1186  * If we allocate a new one we do not mark it dirty. That's up to the
1187  * vm. If we swap it in we mark it dirty since we also free the swap
1188  * entry since a page cannot live in both the swap and page cache
1189  */
1190 static int shmem_getpage(struct inode *inode, unsigned long idx,
1191                         struct page **pagep, enum sgp_type sgp, int *type)
1192 {
1193         struct address_space *mapping = inode->i_mapping;
1194         struct shmem_inode_info *info = SHMEM_I(inode);
1195         struct shmem_sb_info *sbinfo;
1196         struct page *filepage = *pagep;
1197         struct page *swappage;
1198         swp_entry_t *entry;
1199         swp_entry_t swap;
1200         gfp_t gfp;
1201         int error;
1202
1203         if (idx >= SHMEM_MAX_INDEX)
1204                 return -EFBIG;
1205
1206         if (type)
1207                 *type = 0;
1208
1209         /*
1210          * Normally, filepage is NULL on entry, and either found
1211          * uptodate immediately, or allocated and zeroed, or read
1212          * in under swappage, which is then assigned to filepage.
1213          * But shmem_readpage (required for splice) passes in a locked
1214          * filepage, which may be found not uptodate by other callers
1215          * too, and may need to be copied from the swappage read in.
1216          */
1217 repeat:
1218         if (!filepage)
1219                 filepage = find_lock_page(mapping, idx);
1220         if (filepage && PageUptodate(filepage))
1221                 goto done;
1222         error = 0;
1223         gfp = mapping_gfp_mask(mapping);
1224         if (!filepage) {
1225                 /*
1226                  * Try to preload while we can wait, to not make a habit of
1227                  * draining atomic reserves; but don't latch on to this cpu.
1228                  */
1229                 error = radix_tree_preload(gfp & ~__GFP_HIGHMEM);
1230                 if (error)
1231                         goto failed;
1232                 radix_tree_preload_end();
1233         }
1234
1235         spin_lock(&info->lock);
1236         shmem_recalc_inode(inode);
1237         entry = shmem_swp_alloc(info, idx, sgp);
1238         if (IS_ERR(entry)) {
1239                 spin_unlock(&info->lock);
1240                 error = PTR_ERR(entry);
1241                 goto failed;
1242         }
1243         swap = *entry;
1244
1245         if (swap.val) {
1246                 /* Look it up and read it in.. */
1247                 swappage = lookup_swap_cache(swap);
1248                 if (!swappage) {
1249                         shmem_swp_unmap(entry);
1250                         /* here we actually do the io */
1251                         if (type && !(*type & VM_FAULT_MAJOR)) {
1252                                 __count_vm_event(PGMAJFAULT);
1253                                 *type |= VM_FAULT_MAJOR;
1254                         }
1255                         spin_unlock(&info->lock);
1256                         swappage = shmem_swapin(swap, gfp, info, idx);
1257                         if (!swappage) {
1258                                 spin_lock(&info->lock);
1259                                 entry = shmem_swp_alloc(info, idx, sgp);
1260                                 if (IS_ERR(entry))
1261                                         error = PTR_ERR(entry);
1262                                 else {
1263                                         if (entry->val == swap.val)
1264                                                 error = -ENOMEM;
1265                                         shmem_swp_unmap(entry);
1266                                 }
1267                                 spin_unlock(&info->lock);
1268                                 if (error)
1269                                         goto failed;
1270                                 goto repeat;
1271                         }
1272                         wait_on_page_locked(swappage);
1273                         page_cache_release(swappage);
1274                         goto repeat;
1275                 }
1276
1277                 /* We have to do this with page locked to prevent races */
1278                 if (!trylock_page(swappage)) {
1279                         shmem_swp_unmap(entry);
1280                         spin_unlock(&info->lock);
1281                         wait_on_page_locked(swappage);
1282                         page_cache_release(swappage);
1283                         goto repeat;
1284                 }
1285                 if (PageWriteback(swappage)) {
1286                         shmem_swp_unmap(entry);
1287                         spin_unlock(&info->lock);
1288                         wait_on_page_writeback(swappage);
1289                         unlock_page(swappage);
1290                         page_cache_release(swappage);
1291                         goto repeat;
1292                 }
1293                 if (!PageUptodate(swappage)) {
1294                         shmem_swp_unmap(entry);
1295                         spin_unlock(&info->lock);
1296                         unlock_page(swappage);
1297                         page_cache_release(swappage);
1298                         error = -EIO;
1299                         goto failed;
1300                 }
1301
1302                 if (filepage) {
1303                         shmem_swp_set(info, entry, 0);
1304                         shmem_swp_unmap(entry);
1305                         delete_from_swap_cache(swappage);
1306                         spin_unlock(&info->lock);
1307                         copy_highpage(filepage, swappage);
1308                         unlock_page(swappage);
1309                         page_cache_release(swappage);
1310                         flush_dcache_page(filepage);
1311                         SetPageUptodate(filepage);
1312                         set_page_dirty(filepage);
1313                         swap_free(swap);
1314                 } else if (!(error = add_to_page_cache_locked(swappage, mapping,
1315                                         idx, GFP_NOWAIT))) {
1316                         info->flags |= SHMEM_PAGEIN;
1317                         shmem_swp_set(info, entry, 0);
1318                         shmem_swp_unmap(entry);
1319                         delete_from_swap_cache(swappage);
1320                         spin_unlock(&info->lock);
1321                         filepage = swappage;
1322                         set_page_dirty(filepage);
1323                         swap_free(swap);
1324                 } else {
1325                         shmem_swp_unmap(entry);
1326                         spin_unlock(&info->lock);
1327                         if (error == -ENOMEM) {
1328                                 /* allow reclaim from this memory cgroup */
1329                                 error = mem_cgroup_shrink_usage(swappage,
1330                                                                 current->mm,
1331                                                                 gfp);
1332                                 if (error) {
1333                                         unlock_page(swappage);
1334                                         page_cache_release(swappage);
1335                                         goto failed;
1336                                 }
1337                         }
1338                         unlock_page(swappage);
1339                         page_cache_release(swappage);
1340                         goto repeat;
1341                 }
1342         } else if (sgp == SGP_READ && !filepage) {
1343                 shmem_swp_unmap(entry);
1344                 filepage = find_get_page(mapping, idx);
1345                 if (filepage &&
1346                     (!PageUptodate(filepage) || !trylock_page(filepage))) {
1347                         spin_unlock(&info->lock);
1348                         wait_on_page_locked(filepage);
1349                         page_cache_release(filepage);
1350                         filepage = NULL;
1351                         goto repeat;
1352                 }
1353                 spin_unlock(&info->lock);
1354         } else {
1355                 shmem_swp_unmap(entry);
1356                 sbinfo = SHMEM_SB(inode->i_sb);
1357                 if (sbinfo->max_blocks) {
1358                         spin_lock(&sbinfo->stat_lock);
1359                         if (sbinfo->free_blocks == 0 ||
1360                             shmem_acct_block(info->flags)) {
1361                                 spin_unlock(&sbinfo->stat_lock);
1362                                 spin_unlock(&info->lock);
1363                                 error = -ENOSPC;
1364                                 goto failed;
1365                         }
1366                         sbinfo->free_blocks--;
1367                         inode->i_blocks += BLOCKS_PER_PAGE;
1368                         spin_unlock(&sbinfo->stat_lock);
1369                 } else if (shmem_acct_block(info->flags)) {
1370                         spin_unlock(&info->lock);
1371                         error = -ENOSPC;
1372                         goto failed;
1373                 }
1374
1375                 if (!filepage) {
1376                         int ret;
1377
1378                         spin_unlock(&info->lock);
1379                         filepage = shmem_alloc_page(gfp, info, idx);
1380                         if (!filepage) {
1381                                 shmem_unacct_blocks(info->flags, 1);
1382                                 shmem_free_blocks(inode, 1);
1383                                 error = -ENOMEM;
1384                                 goto failed;
1385                         }
1386                         SetPageSwapBacked(filepage);
1387
1388                         /* Precharge page while we can wait, compensate after */
1389                         error = mem_cgroup_cache_charge(filepage, current->mm,
1390                                         GFP_KERNEL);
1391                         if (error) {
1392                                 page_cache_release(filepage);
1393                                 shmem_unacct_blocks(info->flags, 1);
1394                                 shmem_free_blocks(inode, 1);
1395                                 filepage = NULL;
1396                                 goto failed;
1397                         }
1398
1399                         spin_lock(&info->lock);
1400                         entry = shmem_swp_alloc(info, idx, sgp);
1401                         if (IS_ERR(entry))
1402                                 error = PTR_ERR(entry);
1403                         else {
1404                                 swap = *entry;
1405                                 shmem_swp_unmap(entry);
1406                         }
1407                         ret = error || swap.val;
1408                         if (ret)
1409                                 mem_cgroup_uncharge_cache_page(filepage);
1410                         else
1411                                 ret = add_to_page_cache_lru(filepage, mapping,
1412                                                 idx, GFP_NOWAIT);
1413                         /*
1414                          * At add_to_page_cache_lru() failure, uncharge will
1415                          * be done automatically.
1416                          */
1417                         if (ret) {
1418                                 spin_unlock(&info->lock);
1419                                 page_cache_release(filepage);
1420                                 shmem_unacct_blocks(info->flags, 1);
1421                                 shmem_free_blocks(inode, 1);
1422                                 filepage = NULL;
1423                                 if (error)
1424                                         goto failed;
1425                                 goto repeat;
1426                         }
1427                         info->flags |= SHMEM_PAGEIN;
1428                 }
1429
1430                 info->alloced++;
1431                 spin_unlock(&info->lock);
1432                 clear_highpage(filepage);
1433                 flush_dcache_page(filepage);
1434                 SetPageUptodate(filepage);
1435                 if (sgp == SGP_DIRTY)
1436                         set_page_dirty(filepage);
1437         }
1438 done:
1439         *pagep = filepage;
1440         return 0;
1441
1442 failed:
1443         if (*pagep != filepage) {
1444                 unlock_page(filepage);
1445                 page_cache_release(filepage);
1446         }
1447         return error;
1448 }
1449
1450 static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1451 {
1452         struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1453         int error;
1454         int ret;
1455
1456         if (((loff_t)vmf->pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
1457                 return VM_FAULT_SIGBUS;
1458
1459         error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret);
1460         if (error)
1461                 return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1462
1463         return ret | VM_FAULT_LOCKED;
1464 }
1465
1466 #ifdef CONFIG_NUMA
1467 static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *new)
1468 {
1469         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1470         return mpol_set_shared_policy(&SHMEM_I(i)->policy, vma, new);
1471 }
1472
1473 static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
1474                                           unsigned long addr)
1475 {
1476         struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1477         unsigned long idx;
1478
1479         idx = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1480         return mpol_shared_policy_lookup(&SHMEM_I(i)->policy, idx);
1481 }
1482 #endif
1483
1484 int shmem_lock(struct file *file, int lock, struct user_struct *user)
1485 {
1486         struct inode *inode = file->f_path.dentry->d_inode;
1487         struct shmem_inode_info *info = SHMEM_I(inode);
1488         int retval = -ENOMEM;
1489
1490         spin_lock(&info->lock);
1491         if (lock && !(info->flags & VM_LOCKED)) {
1492                 if (!user_shm_lock(inode->i_size, user))
1493                         goto out_nomem;
1494                 info->flags |= VM_LOCKED;
1495                 mapping_set_unevictable(file->f_mapping);
1496         }
1497         if (!lock && (info->flags & VM_LOCKED) && user) {
1498                 user_shm_unlock(inode->i_size, user);
1499                 info->flags &= ~VM_LOCKED;
1500                 mapping_clear_unevictable(file->f_mapping);
1501                 scan_mapping_unevictable_pages(file->f_mapping);
1502         }
1503         retval = 0;
1504
1505 out_nomem:
1506         spin_unlock(&info->lock);
1507         return retval;
1508 }
1509
1510 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1511 {
1512         file_accessed(file);
1513         vma->vm_ops = &shmem_vm_ops;
1514         vma->vm_flags |= VM_CAN_NONLINEAR;
1515         return 0;
1516 }
1517
1518 static struct inode *
1519 shmem_get_inode(struct super_block *sb, int mode, dev_t dev)
1520 {
1521         struct inode *inode;
1522         struct shmem_inode_info *info;
1523         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1524
1525         if (shmem_reserve_inode(sb))
1526                 return NULL;
1527
1528         inode = new_inode(sb);
1529         if (inode) {
1530                 inode->i_mode = mode;
1531                 inode->i_uid = current_fsuid();
1532                 inode->i_gid = current_fsgid();
1533                 inode->i_blocks = 0;
1534                 inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1535                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1536                 inode->i_generation = get_seconds();
1537                 info = SHMEM_I(inode);
1538                 memset(info, 0, (char *)inode - (char *)info);
1539                 spin_lock_init(&info->lock);
1540                 INIT_LIST_HEAD(&info->swaplist);
1541
1542                 switch (mode & S_IFMT) {
1543                 default:
1544                         inode->i_op = &shmem_special_inode_operations;
1545                         init_special_inode(inode, mode, dev);
1546                         break;
1547                 case S_IFREG:
1548                         inode->i_mapping->a_ops = &shmem_aops;
1549                         inode->i_op = &shmem_inode_operations;
1550                         inode->i_fop = &shmem_file_operations;
1551                         mpol_shared_policy_init(&info->policy,
1552                                                  shmem_get_sbmpol(sbinfo));
1553                         break;
1554                 case S_IFDIR:
1555                         inc_nlink(inode);
1556                         /* Some things misbehave if size == 0 on a directory */
1557                         inode->i_size = 2 * BOGO_DIRENT_SIZE;
1558                         inode->i_op = &shmem_dir_inode_operations;
1559                         inode->i_fop = &simple_dir_operations;
1560                         break;
1561                 case S_IFLNK:
1562                         /*
1563                          * Must not load anything in the rbtree,
1564                          * mpol_free_shared_policy will not be called.
1565                          */
1566                         mpol_shared_policy_init(&info->policy, NULL);
1567                         break;
1568                 }
1569         } else
1570                 shmem_free_inode(sb);
1571         return inode;
1572 }
1573
1574 #ifdef CONFIG_TMPFS
1575 static const struct inode_operations shmem_symlink_inode_operations;
1576 static const struct inode_operations shmem_symlink_inline_operations;
1577
1578 /*
1579  * Normally tmpfs avoids the use of shmem_readpage and shmem_write_begin;
1580  * but providing them allows a tmpfs file to be used for splice, sendfile, and
1581  * below the loop driver, in the generic fashion that many filesystems support.
1582  */
1583 static int shmem_readpage(struct file *file, struct page *page)
1584 {
1585         struct inode *inode = page->mapping->host;
1586         int error = shmem_getpage(inode, page->index, &page, SGP_CACHE, NULL);
1587         unlock_page(page);
1588         return error;
1589 }
1590
1591 static int
1592 shmem_write_begin(struct file *file, struct address_space *mapping,
1593                         loff_t pos, unsigned len, unsigned flags,
1594                         struct page **pagep, void **fsdata)
1595 {
1596         struct inode *inode = mapping->host;
1597         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1598         *pagep = NULL;
1599         return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
1600 }
1601
1602 static int
1603 shmem_write_end(struct file *file, struct address_space *mapping,
1604                         loff_t pos, unsigned len, unsigned copied,
1605                         struct page *page, void *fsdata)
1606 {
1607         struct inode *inode = mapping->host;
1608
1609         if (pos + copied > inode->i_size)
1610                 i_size_write(inode, pos + copied);
1611
1612         unlock_page(page);
1613         set_page_dirty(page);
1614         page_cache_release(page);
1615
1616         return copied;
1617 }
1618
1619 static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
1620 {
1621         struct inode *inode = filp->f_path.dentry->d_inode;
1622         struct address_space *mapping = inode->i_mapping;
1623         unsigned long index, offset;
1624         enum sgp_type sgp = SGP_READ;
1625
1626         /*
1627          * Might this read be for a stacking filesystem?  Then when reading
1628          * holes of a sparse file, we actually need to allocate those pages,
1629          * and even mark them dirty, so it cannot exceed the max_blocks limit.
1630          */
1631         if (segment_eq(get_fs(), KERNEL_DS))
1632                 sgp = SGP_DIRTY;
1633
1634         index = *ppos >> PAGE_CACHE_SHIFT;
1635         offset = *ppos & ~PAGE_CACHE_MASK;
1636
1637         for (;;) {
1638                 struct page *page = NULL;
1639                 unsigned long end_index, nr, ret;
1640                 loff_t i_size = i_size_read(inode);
1641
1642                 end_index = i_size >> PAGE_CACHE_SHIFT;
1643                 if (index > end_index)
1644                         break;
1645                 if (index == end_index) {
1646                         nr = i_size & ~PAGE_CACHE_MASK;
1647                         if (nr <= offset)
1648                                 break;
1649                 }
1650
1651                 desc->error = shmem_getpage(inode, index, &page, sgp, NULL);
1652                 if (desc->error) {
1653                         if (desc->error == -EINVAL)
1654                                 desc->error = 0;
1655                         break;
1656                 }
1657                 if (page)
1658                         unlock_page(page);
1659
1660                 /*
1661                  * We must evaluate after, since reads (unlike writes)
1662                  * are called without i_mutex protection against truncate
1663                  */
1664                 nr = PAGE_CACHE_SIZE;
1665                 i_size = i_size_read(inode);
1666                 end_index = i_size >> PAGE_CACHE_SHIFT;
1667                 if (index == end_index) {
1668                         nr = i_size & ~PAGE_CACHE_MASK;
1669                         if (nr <= offset) {
1670                                 if (page)
1671                                         page_cache_release(page);
1672                                 break;
1673                         }
1674                 }
1675                 nr -= offset;
1676
1677                 if (page) {
1678                         /*
1679                          * If users can be writing to this page using arbitrary
1680                          * virtual addresses, take care about potential aliasing
1681                          * before reading the page on the kernel side.
1682                          */
1683                         if (mapping_writably_mapped(mapping))
1684                                 flush_dcache_page(page);
1685                         /*
1686                          * Mark the page accessed if we read the beginning.
1687                          */
1688                         if (!offset)
1689                                 mark_page_accessed(page);
1690                 } else {
1691                         page = ZERO_PAGE(0);
1692                         page_cache_get(page);
1693                 }
1694
1695                 /*
1696                  * Ok, we have the page, and it's up-to-date, so
1697                  * now we can copy it to user space...
1698                  *
1699                  * The actor routine returns how many bytes were actually used..
1700                  * NOTE! This may not be the same as how much of a user buffer
1701                  * we filled up (we may be padding etc), so we can only update
1702                  * "pos" here (the actor routine has to update the user buffer
1703                  * pointers and the remaining count).
1704                  */
1705                 ret = actor(desc, page, offset, nr);
1706                 offset += ret;
1707                 index += offset >> PAGE_CACHE_SHIFT;
1708                 offset &= ~PAGE_CACHE_MASK;
1709
1710                 page_cache_release(page);
1711                 if (ret != nr || !desc->count)
1712                         break;
1713
1714                 cond_resched();
1715         }
1716
1717         *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1718         file_accessed(filp);
1719 }
1720
1721 static ssize_t shmem_file_aio_read(struct kiocb *iocb,
1722                 const struct iovec *iov, unsigned long nr_segs, loff_t pos)
1723 {
1724         struct file *filp = iocb->ki_filp;
1725         ssize_t retval;
1726         unsigned long seg;
1727         size_t count;
1728         loff_t *ppos = &iocb->ki_pos;
1729
1730         retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1731         if (retval)
1732                 return retval;
1733
1734         for (seg = 0; seg < nr_segs; seg++) {
1735                 read_descriptor_t desc;
1736
1737                 desc.written = 0;
1738                 desc.arg.buf = iov[seg].iov_base;
1739                 desc.count = iov[seg].iov_len;
1740                 if (desc.count == 0)
1741                         continue;
1742                 desc.error = 0;
1743                 do_shmem_file_read(filp, ppos, &desc, file_read_actor);
1744                 retval += desc.written;
1745                 if (desc.error) {
1746                         retval = retval ?: desc.error;
1747                         break;
1748                 }
1749                 if (desc.count > 0)
1750                         break;
1751         }
1752         return retval;
1753 }
1754
1755 static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
1756 {
1757         struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
1758
1759         buf->f_type = TMPFS_MAGIC;
1760         buf->f_bsize = PAGE_CACHE_SIZE;
1761         buf->f_namelen = NAME_MAX;
1762         spin_lock(&sbinfo->stat_lock);
1763         if (sbinfo->max_blocks) {
1764                 buf->f_blocks = sbinfo->max_blocks;
1765                 buf->f_bavail = buf->f_bfree = sbinfo->free_blocks;
1766         }
1767         if (sbinfo->max_inodes) {
1768                 buf->f_files = sbinfo->max_inodes;
1769                 buf->f_ffree = sbinfo->free_inodes;
1770         }
1771         /* else leave those fields 0 like simple_statfs */
1772         spin_unlock(&sbinfo->stat_lock);
1773         return 0;
1774 }
1775
1776 /*
1777  * File creation. Allocate an inode, and we're done..
1778  */
1779 static int
1780 shmem_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
1781 {
1782         struct inode *inode = shmem_get_inode(dir->i_sb, mode, dev);
1783         int error = -ENOSPC;
1784
1785         if (inode) {
1786                 error = security_inode_init_security(inode, dir, NULL, NULL,
1787                                                      NULL);
1788                 if (error) {
1789                         if (error != -EOPNOTSUPP) {
1790                                 iput(inode);
1791                                 return error;
1792                         }
1793                 }
1794                 error = shmem_acl_init(inode, dir);
1795                 if (error) {
1796                         iput(inode);
1797                         return error;
1798                 }
1799                 if (dir->i_mode & S_ISGID) {
1800                         inode->i_gid = dir->i_gid;
1801                         if (S_ISDIR(mode))
1802                                 inode->i_mode |= S_ISGID;
1803                 }
1804                 dir->i_size += BOGO_DIRENT_SIZE;
1805                 dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1806                 d_instantiate(dentry, inode);
1807                 dget(dentry); /* Extra count - pin the dentry in core */
1808         }
1809         return error;
1810 }
1811
1812 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, int mode)
1813 {
1814         int error;
1815
1816         if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
1817                 return error;
1818         inc_nlink(dir);
1819         return 0;
1820 }
1821
1822 static int shmem_create(struct inode *dir, struct dentry *dentry, int mode,
1823                 struct nameidata *nd)
1824 {
1825         return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
1826 }
1827
1828 /*
1829  * Link a file..
1830  */
1831 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
1832 {
1833         struct inode *inode = old_dentry->d_inode;
1834         int ret;
1835
1836         /*
1837          * No ordinary (disk based) filesystem counts links as inodes;
1838          * but each new link needs a new dentry, pinning lowmem, and
1839          * tmpfs dentries cannot be pruned until they are unlinked.
1840          */
1841         ret = shmem_reserve_inode(inode->i_sb);
1842         if (ret)
1843                 goto out;
1844
1845         dir->i_size += BOGO_DIRENT_SIZE;
1846         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1847         inc_nlink(inode);
1848         atomic_inc(&inode->i_count);    /* New dentry reference */
1849         dget(dentry);           /* Extra pinning count for the created dentry */
1850         d_instantiate(dentry, inode);
1851 out:
1852         return ret;
1853 }
1854
1855 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
1856 {
1857         struct inode *inode = dentry->d_inode;
1858
1859         if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
1860                 shmem_free_inode(inode->i_sb);
1861
1862         dir->i_size -= BOGO_DIRENT_SIZE;
1863         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1864         drop_nlink(inode);
1865         dput(dentry);   /* Undo the count from "create" - this does all the work */
1866         return 0;
1867 }
1868
1869 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
1870 {
1871         if (!simple_empty(dentry))
1872                 return -ENOTEMPTY;
1873
1874         drop_nlink(dentry->d_inode);
1875         drop_nlink(dir);
1876         return shmem_unlink(dir, dentry);
1877 }
1878
1879 /*
1880  * The VFS layer already does all the dentry stuff for rename,
1881  * we just have to decrement the usage count for the target if
1882  * it exists so that the VFS layer correctly free's it when it
1883  * gets overwritten.
1884  */
1885 static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
1886 {
1887         struct inode *inode = old_dentry->d_inode;
1888         int they_are_dirs = S_ISDIR(inode->i_mode);
1889
1890         if (!simple_empty(new_dentry))
1891                 return -ENOTEMPTY;
1892
1893         if (new_dentry->d_inode) {
1894                 (void) shmem_unlink(new_dir, new_dentry);
1895                 if (they_are_dirs)
1896                         drop_nlink(old_dir);
1897         } else if (they_are_dirs) {
1898                 drop_nlink(old_dir);
1899                 inc_nlink(new_dir);
1900         }
1901
1902         old_dir->i_size -= BOGO_DIRENT_SIZE;
1903         new_dir->i_size += BOGO_DIRENT_SIZE;
1904         old_dir->i_ctime = old_dir->i_mtime =
1905         new_dir->i_ctime = new_dir->i_mtime =
1906         inode->i_ctime = CURRENT_TIME;
1907         return 0;
1908 }
1909
1910 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
1911 {
1912         int error;
1913         int len;
1914         struct inode *inode;
1915         struct page *page = NULL;
1916         char *kaddr;
1917         struct shmem_inode_info *info;
1918
1919         len = strlen(symname) + 1;
1920         if (len > PAGE_CACHE_SIZE)
1921                 return -ENAMETOOLONG;
1922
1923         inode = shmem_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0);
1924         if (!inode)
1925                 return -ENOSPC;
1926
1927         error = security_inode_init_security(inode, dir, NULL, NULL,
1928                                              NULL);
1929         if (error) {
1930                 if (error != -EOPNOTSUPP) {
1931                         iput(inode);
1932                         return error;
1933                 }
1934                 error = 0;
1935         }
1936
1937         info = SHMEM_I(inode);
1938         inode->i_size = len-1;
1939         if (len <= (char *)inode - (char *)info) {
1940                 /* do it inline */
1941                 memcpy(info, symname, len);
1942                 inode->i_op = &shmem_symlink_inline_operations;
1943         } else {
1944                 error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
1945                 if (error) {
1946                         iput(inode);
1947                         return error;
1948                 }
1949                 unlock_page(page);
1950                 inode->i_mapping->a_ops = &shmem_aops;
1951                 inode->i_op = &shmem_symlink_inode_operations;
1952                 kaddr = kmap_atomic(page, KM_USER0);
1953                 memcpy(kaddr, symname, len);
1954                 kunmap_atomic(kaddr, KM_USER0);
1955                 set_page_dirty(page);
1956                 page_cache_release(page);
1957         }
1958         if (dir->i_mode & S_ISGID)
1959                 inode->i_gid = dir->i_gid;
1960         dir->i_size += BOGO_DIRENT_SIZE;
1961         dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1962         d_instantiate(dentry, inode);
1963         dget(dentry);
1964         return 0;
1965 }
1966
1967 static void *shmem_follow_link_inline(struct dentry *dentry, struct nameidata *nd)
1968 {
1969         nd_set_link(nd, (char *)SHMEM_I(dentry->d_inode));
1970         return NULL;
1971 }
1972
1973 static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
1974 {
1975         struct page *page = NULL;
1976         int res = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
1977         nd_set_link(nd, res ? ERR_PTR(res) : kmap(page));
1978         if (page)
1979                 unlock_page(page);
1980         return page;
1981 }
1982
1983 static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
1984 {
1985         if (!IS_ERR(nd_get_link(nd))) {
1986                 struct page *page = cookie;
1987                 kunmap(page);
1988                 mark_page_accessed(page);
1989                 page_cache_release(page);
1990         }
1991 }
1992
1993 static const struct inode_operations shmem_symlink_inline_operations = {
1994         .readlink       = generic_readlink,
1995         .follow_link    = shmem_follow_link_inline,
1996 };
1997
1998 static const struct inode_operations shmem_symlink_inode_operations = {
1999         .truncate       = shmem_truncate,
2000         .readlink       = generic_readlink,
2001         .follow_link    = shmem_follow_link,
2002         .put_link       = shmem_put_link,
2003 };
2004
2005 #ifdef CONFIG_TMPFS_POSIX_ACL
2006 /*
2007  * Superblocks without xattr inode operations will get security.* xattr
2008  * support from the VFS "for free". As soon as we have any other xattrs
2009  * like ACLs, we also need to implement the security.* handlers at
2010  * filesystem level, though.
2011  */
2012
2013 static size_t shmem_xattr_security_list(struct inode *inode, char *list,
2014                                         size_t list_len, const char *name,
2015                                         size_t name_len)
2016 {
2017         return security_inode_listsecurity(inode, list, list_len);
2018 }
2019
2020 static int shmem_xattr_security_get(struct inode *inode, const char *name,
2021                                     void *buffer, size_t size)
2022 {
2023         if (strcmp(name, "") == 0)
2024                 return -EINVAL;
2025         return xattr_getsecurity(inode, name, buffer, size);
2026 }
2027
2028 static int shmem_xattr_security_set(struct inode *inode, const char *name,
2029                                     const void *value, size_t size, int flags)
2030 {
2031         if (strcmp(name, "") == 0)
2032                 return -EINVAL;
2033         return security_inode_setsecurity(inode, name, value, size, flags);
2034 }
2035
2036 static struct xattr_handler shmem_xattr_security_handler = {
2037         .prefix = XATTR_SECURITY_PREFIX,
2038         .list   = shmem_xattr_security_list,
2039         .get    = shmem_xattr_security_get,
2040         .set    = shmem_xattr_security_set,
2041 };
2042
2043 static struct xattr_handler *shmem_xattr_handlers[] = {
2044         &shmem_xattr_acl_access_handler,
2045         &shmem_xattr_acl_default_handler,
2046         &shmem_xattr_security_handler,
2047         NULL
2048 };
2049 #endif
2050
2051 static struct dentry *shmem_get_parent(struct dentry *child)
2052 {
2053         return ERR_PTR(-ESTALE);
2054 }
2055
2056 static int shmem_match(struct inode *ino, void *vfh)
2057 {
2058         __u32 *fh = vfh;
2059         __u64 inum = fh[2];
2060         inum = (inum << 32) | fh[1];
2061         return ino->i_ino == inum && fh[0] == ino->i_generation;
2062 }
2063
2064 static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
2065                 struct fid *fid, int fh_len, int fh_type)
2066 {
2067         struct inode *inode;
2068         struct dentry *dentry = NULL;
2069         u64 inum = fid->raw[2];
2070         inum = (inum << 32) | fid->raw[1];
2071
2072         if (fh_len < 3)
2073                 return NULL;
2074
2075         inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
2076                         shmem_match, fid->raw);
2077         if (inode) {
2078                 dentry = d_find_alias(inode);
2079                 iput(inode);
2080         }
2081
2082         return dentry;
2083 }
2084
2085 static int shmem_encode_fh(struct dentry *dentry, __u32 *fh, int *len,
2086                                 int connectable)
2087 {
2088         struct inode *inode = dentry->d_inode;
2089
2090         if (*len < 3)
2091                 return 255;
2092
2093         if (hlist_unhashed(&inode->i_hash)) {
2094                 /* Unfortunately insert_inode_hash is not idempotent,
2095                  * so as we hash inodes here rather than at creation
2096                  * time, we need a lock to ensure we only try
2097                  * to do it once
2098                  */
2099                 static DEFINE_SPINLOCK(lock);
2100                 spin_lock(&lock);
2101                 if (hlist_unhashed(&inode->i_hash))
2102                         __insert_inode_hash(inode,
2103                                             inode->i_ino + inode->i_generation);
2104                 spin_unlock(&lock);
2105         }
2106
2107         fh[0] = inode->i_generation;
2108         fh[1] = inode->i_ino;
2109         fh[2] = ((__u64)inode->i_ino) >> 32;
2110
2111         *len = 3;
2112         return 1;
2113 }
2114
2115 static const struct export_operations shmem_export_ops = {
2116         .get_parent     = shmem_get_parent,
2117         .encode_fh      = shmem_encode_fh,
2118         .fh_to_dentry   = shmem_fh_to_dentry,
2119 };
2120
2121 static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
2122                                bool remount)
2123 {
2124         char *this_char, *value, *rest;
2125
2126         while (options != NULL) {
2127                 this_char = options;
2128                 for (;;) {
2129                         /*
2130                          * NUL-terminate this option: unfortunately,
2131                          * mount options form a comma-separated list,
2132                          * but mpol's nodelist may also contain commas.
2133                          */
2134                         options = strchr(options, ',');
2135                         if (options == NULL)
2136                                 break;
2137                         options++;
2138                         if (!isdigit(*options)) {
2139                                 options[-1] = '\0';
2140                                 break;
2141                         }
2142                 }
2143                 if (!*this_char)
2144                         continue;
2145                 if ((value = strchr(this_char,'=')) != NULL) {
2146                         *value++ = 0;
2147                 } else {
2148                         printk(KERN_ERR
2149                             "tmpfs: No value for mount option '%s'\n",
2150                             this_char);
2151                         return 1;
2152                 }
2153
2154                 if (!strcmp(this_char,"size")) {
2155                         unsigned long long size;
2156                         size = memparse(value,&rest);
2157                         if (*rest == '%') {
2158                                 size <<= PAGE_SHIFT;
2159                                 size *= totalram_pages;
2160                                 do_div(size, 100);
2161                                 rest++;
2162                         }
2163                         if (*rest)
2164                                 goto bad_val;
2165                         sbinfo->max_blocks =
2166                                 DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
2167                 } else if (!strcmp(this_char,"nr_blocks")) {
2168                         sbinfo->max_blocks = memparse(value, &rest);
2169                         if (*rest)
2170                                 goto bad_val;
2171                 } else if (!strcmp(this_char,"nr_inodes")) {
2172                         sbinfo->max_inodes = memparse(value, &rest);
2173                         if (*rest)
2174                                 goto bad_val;
2175                 } else if (!strcmp(this_char,"mode")) {
2176                         if (remount)
2177                                 continue;
2178                         sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
2179                         if (*rest)
2180                                 goto bad_val;
2181                 } else if (!strcmp(this_char,"uid")) {
2182                         if (remount)
2183                                 continue;
2184                         sbinfo->uid = simple_strtoul(value, &rest, 0);
2185                         if (*rest)
2186                                 goto bad_val;
2187                 } else if (!strcmp(this_char,"gid")) {
2188                         if (remount)
2189                                 continue;
2190                         sbinfo->gid = simple_strtoul(value, &rest, 0);
2191                         if (*rest)
2192                                 goto bad_val;
2193                 } else if (!strcmp(this_char,"mpol")) {
2194                         if (mpol_parse_str(value, &sbinfo->mpol, 1))
2195                                 goto bad_val;
2196                 } else {
2197                         printk(KERN_ERR "tmpfs: Bad mount option %s\n",
2198                                this_char);
2199                         return 1;
2200                 }
2201         }
2202         return 0;
2203
2204 bad_val:
2205         printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
2206                value, this_char);
2207         return 1;
2208
2209 }
2210
2211 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2212 {
2213         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2214         struct shmem_sb_info config = *sbinfo;
2215         unsigned long blocks;
2216         unsigned long inodes;
2217         int error = -EINVAL;
2218
2219         if (shmem_parse_options(data, &config, true))
2220                 return error;
2221
2222         spin_lock(&sbinfo->stat_lock);
2223         blocks = sbinfo->max_blocks - sbinfo->free_blocks;
2224         inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2225         if (config.max_blocks < blocks)
2226                 goto out;
2227         if (config.max_inodes < inodes)
2228                 goto out;
2229         /*
2230          * Those tests also disallow limited->unlimited while any are in
2231          * use, so i_blocks will always be zero when max_blocks is zero;
2232          * but we must separately disallow unlimited->limited, because
2233          * in that case we have no record of how much is already in use.
2234          */
2235         if (config.max_blocks && !sbinfo->max_blocks)
2236                 goto out;
2237         if (config.max_inodes && !sbinfo->max_inodes)
2238                 goto out;
2239
2240         error = 0;
2241         sbinfo->max_blocks  = config.max_blocks;
2242         sbinfo->free_blocks = config.max_blocks - blocks;
2243         sbinfo->max_inodes  = config.max_inodes;
2244         sbinfo->free_inodes = config.max_inodes - inodes;
2245
2246         mpol_put(sbinfo->mpol);
2247         sbinfo->mpol        = config.mpol;      /* transfers initial ref */
2248 out:
2249         spin_unlock(&sbinfo->stat_lock);
2250         return error;
2251 }
2252
2253 static int shmem_show_options(struct seq_file *seq, struct vfsmount *vfs)
2254 {
2255         struct shmem_sb_info *sbinfo = SHMEM_SB(vfs->mnt_sb);
2256
2257         if (sbinfo->max_blocks != shmem_default_max_blocks())
2258                 seq_printf(seq, ",size=%luk",
2259                         sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10));
2260         if (sbinfo->max_inodes != shmem_default_max_inodes())
2261                 seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
2262         if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
2263                 seq_printf(seq, ",mode=%03o", sbinfo->mode);
2264         if (sbinfo->uid != 0)
2265                 seq_printf(seq, ",uid=%u", sbinfo->uid);
2266         if (sbinfo->gid != 0)
2267                 seq_printf(seq, ",gid=%u", sbinfo->gid);
2268         shmem_show_mpol(seq, sbinfo->mpol);
2269         return 0;
2270 }
2271 #endif /* CONFIG_TMPFS */
2272
2273 static void shmem_put_super(struct super_block *sb)
2274 {
2275         kfree(sb->s_fs_info);
2276         sb->s_fs_info = NULL;
2277 }
2278
2279 static int shmem_fill_super(struct super_block *sb,
2280                             void *data, int silent)
2281 {
2282         struct inode *inode;
2283         struct dentry *root;
2284         struct shmem_sb_info *sbinfo;
2285         int err = -ENOMEM;
2286
2287         /* Round up to L1_CACHE_BYTES to resist false sharing */
2288         sbinfo = kmalloc(max((int)sizeof(struct shmem_sb_info),
2289                                 L1_CACHE_BYTES), GFP_KERNEL);
2290         if (!sbinfo)
2291                 return -ENOMEM;
2292
2293         sbinfo->max_blocks = 0;
2294         sbinfo->max_inodes = 0;
2295         sbinfo->mode = S_IRWXUGO | S_ISVTX;
2296         sbinfo->uid = current_fsuid();
2297         sbinfo->gid = current_fsgid();
2298         sbinfo->mpol = NULL;
2299         sb->s_fs_info = sbinfo;
2300
2301 #ifdef CONFIG_TMPFS
2302         /*
2303          * Per default we only allow half of the physical ram per
2304          * tmpfs instance, limiting inodes to one per page of lowmem;
2305          * but the internal instance is left unlimited.
2306          */
2307         if (!(sb->s_flags & MS_NOUSER)) {
2308                 sbinfo->max_blocks = shmem_default_max_blocks();
2309                 sbinfo->max_inodes = shmem_default_max_inodes();
2310                 if (shmem_parse_options(data, sbinfo, false)) {
2311                         err = -EINVAL;
2312                         goto failed;
2313                 }
2314         }
2315         sb->s_export_op = &shmem_export_ops;
2316 #else
2317         sb->s_flags |= MS_NOUSER;
2318 #endif
2319
2320         spin_lock_init(&sbinfo->stat_lock);
2321         sbinfo->free_blocks = sbinfo->max_blocks;
2322         sbinfo->free_inodes = sbinfo->max_inodes;
2323
2324         sb->s_maxbytes = SHMEM_MAX_BYTES;
2325         sb->s_blocksize = PAGE_CACHE_SIZE;
2326         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
2327         sb->s_magic = TMPFS_MAGIC;
2328         sb->s_op = &shmem_ops;
2329         sb->s_time_gran = 1;
2330 #ifdef CONFIG_TMPFS_POSIX_ACL
2331         sb->s_xattr = shmem_xattr_handlers;
2332         sb->s_flags |= MS_POSIXACL;
2333 #endif
2334
2335         inode = shmem_get_inode(sb, S_IFDIR | sbinfo->mode, 0);
2336         if (!inode)
2337                 goto failed;
2338         inode->i_uid = sbinfo->uid;
2339         inode->i_gid = sbinfo->gid;
2340         root = d_alloc_root(inode);
2341         if (!root)
2342                 goto failed_iput;
2343         sb->s_root = root;
2344         return 0;
2345
2346 failed_iput:
2347         iput(inode);
2348 failed:
2349         shmem_put_super(sb);
2350         return err;
2351 }
2352
2353 static struct kmem_cache *shmem_inode_cachep;
2354
2355 static struct inode *shmem_alloc_inode(struct super_block *sb)
2356 {
2357         struct shmem_inode_info *p;
2358         p = (struct shmem_inode_info *)kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
2359         if (!p)
2360                 return NULL;
2361         return &p->vfs_inode;
2362 }
2363
2364 static void shmem_destroy_inode(struct inode *inode)
2365 {
2366         if ((inode->i_mode & S_IFMT) == S_IFREG) {
2367                 /* only struct inode is valid if it's an inline symlink */
2368                 mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2369         }
2370         shmem_acl_destroy_inode(inode);
2371         kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2372 }
2373
2374 static void init_once(void *foo)
2375 {
2376         struct shmem_inode_info *p = (struct shmem_inode_info *) foo;
2377
2378         inode_init_once(&p->vfs_inode);
2379 #ifdef CONFIG_TMPFS_POSIX_ACL
2380         p->i_acl = NULL;
2381         p->i_default_acl = NULL;
2382 #endif
2383 }
2384
2385 static int init_inodecache(void)
2386 {
2387         shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
2388                                 sizeof(struct shmem_inode_info),
2389                                 0, SLAB_PANIC, init_once);
2390         return 0;
2391 }
2392
2393 static void destroy_inodecache(void)
2394 {
2395         kmem_cache_destroy(shmem_inode_cachep);
2396 }
2397
2398 static const struct address_space_operations shmem_aops = {
2399         .writepage      = shmem_writepage,
2400         .set_page_dirty = __set_page_dirty_no_writeback,
2401 #ifdef CONFIG_TMPFS
2402         .readpage       = shmem_readpage,
2403         .write_begin    = shmem_write_begin,
2404         .write_end      = shmem_write_end,
2405 #endif
2406         .migratepage    = migrate_page,
2407 };
2408
2409 static const struct file_operations shmem_file_operations = {
2410         .mmap           = shmem_mmap,
2411 #ifdef CONFIG_TMPFS
2412         .llseek         = generic_file_llseek,
2413         .read           = do_sync_read,
2414         .write          = do_sync_write,
2415         .aio_read       = shmem_file_aio_read,
2416         .aio_write      = generic_file_aio_write,
2417         .fsync          = simple_sync_file,
2418         .splice_read    = generic_file_splice_read,
2419         .splice_write   = generic_file_splice_write,
2420 #endif
2421 };
2422
2423 static const struct inode_operations shmem_inode_operations = {
2424         .truncate       = shmem_truncate,
2425         .setattr        = shmem_notify_change,
2426         .truncate_range = shmem_truncate_range,
2427 #ifdef CONFIG_TMPFS_POSIX_ACL
2428         .setxattr       = generic_setxattr,
2429         .getxattr       = generic_getxattr,
2430         .listxattr      = generic_listxattr,
2431         .removexattr    = generic_removexattr,
2432         .permission     = shmem_permission,
2433 #endif
2434
2435 };
2436
2437 static const struct inode_operations shmem_dir_inode_operations = {
2438 #ifdef CONFIG_TMPFS
2439         .create         = shmem_create,
2440         .lookup         = simple_lookup,
2441         .link           = shmem_link,
2442         .unlink         = shmem_unlink,
2443         .symlink        = shmem_symlink,
2444         .mkdir          = shmem_mkdir,
2445         .rmdir          = shmem_rmdir,
2446         .mknod          = shmem_mknod,
2447         .rename         = shmem_rename,
2448 #endif
2449 #ifdef CONFIG_TMPFS_POSIX_ACL
2450         .setattr        = shmem_notify_change,
2451         .setxattr       = generic_setxattr,
2452         .getxattr       = generic_getxattr,
2453         .listxattr      = generic_listxattr,
2454         .removexattr    = generic_removexattr,
2455         .permission     = shmem_permission,
2456 #endif
2457 };
2458
2459 static const struct inode_operations shmem_special_inode_operations = {
2460 #ifdef CONFIG_TMPFS_POSIX_ACL
2461         .setattr        = shmem_notify_change,
2462         .setxattr       = generic_setxattr,
2463         .getxattr       = generic_getxattr,
2464         .listxattr      = generic_listxattr,
2465         .removexattr    = generic_removexattr,
2466         .permission     = shmem_permission,
2467 #endif
2468 };
2469
2470 static const struct super_operations shmem_ops = {
2471         .alloc_inode    = shmem_alloc_inode,
2472         .destroy_inode  = shmem_destroy_inode,
2473 #ifdef CONFIG_TMPFS
2474         .statfs         = shmem_statfs,
2475         .remount_fs     = shmem_remount_fs,
2476         .show_options   = shmem_show_options,
2477 #endif
2478         .delete_inode   = shmem_delete_inode,
2479         .drop_inode     = generic_delete_inode,
2480         .put_super      = shmem_put_super,
2481 };
2482
2483 static struct vm_operations_struct shmem_vm_ops = {
2484         .fault          = shmem_fault,
2485 #ifdef CONFIG_NUMA
2486         .set_policy     = shmem_set_policy,
2487         .get_policy     = shmem_get_policy,
2488 #endif
2489 };
2490
2491
2492 static int shmem_get_sb(struct file_system_type *fs_type,
2493         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
2494 {
2495         return get_sb_nodev(fs_type, flags, data, shmem_fill_super, mnt);
2496 }
2497
2498 static struct file_system_type tmpfs_fs_type = {
2499         .owner          = THIS_MODULE,
2500         .name           = "tmpfs",
2501         .get_sb         = shmem_get_sb,
2502         .kill_sb        = kill_litter_super,
2503 };
2504
2505 static int __init init_tmpfs(void)
2506 {
2507         int error;
2508
2509         error = bdi_init(&shmem_backing_dev_info);
2510         if (error)
2511                 goto out4;
2512
2513         error = init_inodecache();
2514         if (error)
2515                 goto out3;
2516
2517         error = register_filesystem(&tmpfs_fs_type);
2518         if (error) {
2519                 printk(KERN_ERR "Could not register tmpfs\n");
2520                 goto out2;
2521         }
2522
2523         shm_mnt = vfs_kern_mount(&tmpfs_fs_type, MS_NOUSER,
2524                                 tmpfs_fs_type.name, NULL);
2525         if (IS_ERR(shm_mnt)) {
2526                 error = PTR_ERR(shm_mnt);
2527                 printk(KERN_ERR "Could not kern_mount tmpfs\n");
2528                 goto out1;
2529         }
2530         return 0;
2531
2532 out1:
2533         unregister_filesystem(&tmpfs_fs_type);
2534 out2:
2535         destroy_inodecache();
2536 out3:
2537         bdi_destroy(&shmem_backing_dev_info);
2538 out4:
2539         shm_mnt = ERR_PTR(error);
2540         return error;
2541 }
2542
2543 #else /* !CONFIG_SHMEM */
2544
2545 /*
2546  * tiny-shmem: simple shmemfs and tmpfs using ramfs code
2547  *
2548  * This is intended for small system where the benefits of the full
2549  * shmem code (swap-backed and resource-limited) are outweighed by
2550  * their complexity. On systems without swap this code should be
2551  * effectively equivalent, but much lighter weight.
2552  */
2553
2554 #include <linux/ramfs.h>
2555
2556 static struct file_system_type tmpfs_fs_type = {
2557         .name           = "tmpfs",
2558         .get_sb         = ramfs_get_sb,
2559         .kill_sb        = kill_litter_super,
2560 };
2561
2562 static int __init init_tmpfs(void)
2563 {
2564         BUG_ON(register_filesystem(&tmpfs_fs_type) != 0);
2565
2566         shm_mnt = kern_mount(&tmpfs_fs_type);
2567         BUG_ON(IS_ERR(shm_mnt));
2568
2569         return 0;
2570 }
2571
2572 int shmem_unuse(swp_entry_t entry, struct page *page)
2573 {
2574         return 0;
2575 }
2576
2577 #define shmem_file_operations ramfs_file_operations
2578 #define shmem_vm_ops generic_file_vm_ops
2579 #define shmem_get_inode ramfs_get_inode
2580 #define shmem_acct_size(a, b) 0
2581 #define shmem_unacct_size(a, b) do {} while (0)
2582 #define SHMEM_MAX_BYTES LLONG_MAX
2583
2584 #endif /* CONFIG_SHMEM */
2585
2586 /* common code */
2587
2588 /**
2589  * shmem_file_setup - get an unlinked file living in tmpfs
2590  * @name: name for dentry (to be seen in /proc/<pid>/maps
2591  * @size: size to be set for the file
2592  * @flags: vm_flags
2593  */
2594 struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags)
2595 {
2596         int error;
2597         struct file *file;
2598         struct inode *inode;
2599         struct dentry *dentry, *root;
2600         struct qstr this;
2601
2602         if (IS_ERR(shm_mnt))
2603                 return (void *)shm_mnt;
2604
2605         if (size < 0 || size > SHMEM_MAX_BYTES)
2606                 return ERR_PTR(-EINVAL);
2607
2608         if (shmem_acct_size(flags, size))
2609                 return ERR_PTR(-ENOMEM);
2610
2611         error = -ENOMEM;
2612         this.name = name;
2613         this.len = strlen(name);
2614         this.hash = 0; /* will go */
2615         root = shm_mnt->mnt_root;
2616         dentry = d_alloc(root, &this);
2617         if (!dentry)
2618                 goto put_memory;
2619
2620         error = -ENFILE;
2621         file = get_empty_filp();
2622         if (!file)
2623                 goto put_dentry;
2624
2625         error = -ENOSPC;
2626         inode = shmem_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0);
2627         if (!inode)
2628                 goto close_file;
2629
2630 #ifdef CONFIG_SHMEM
2631         SHMEM_I(inode)->flags = (flags & VM_NORESERVE) ? 0 : VM_ACCOUNT;
2632 #endif
2633         d_instantiate(dentry, inode);
2634         inode->i_size = size;
2635         inode->i_nlink = 0;     /* It is unlinked */
2636         init_file(file, shm_mnt, dentry, FMODE_WRITE | FMODE_READ,
2637                   &shmem_file_operations);
2638
2639 #ifndef CONFIG_MMU
2640         error = ramfs_nommu_expand_for_mapping(inode, size);
2641         if (error)
2642                 goto close_file;
2643 #endif
2644         return file;
2645
2646 close_file:
2647         put_filp(file);
2648 put_dentry:
2649         dput(dentry);
2650 put_memory:
2651         shmem_unacct_size(flags, size);
2652         return ERR_PTR(error);
2653 }
2654 EXPORT_SYMBOL_GPL(shmem_file_setup);
2655
2656 /**
2657  * shmem_zero_setup - setup a shared anonymous mapping
2658  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
2659  */
2660 int shmem_zero_setup(struct vm_area_struct *vma)
2661 {
2662         struct file *file;
2663         loff_t size = vma->vm_end - vma->vm_start;
2664
2665         file = shmem_file_setup("dev/zero", size, vma->vm_flags);
2666         if (IS_ERR(file))
2667                 return PTR_ERR(file);
2668
2669         if (vma->vm_file)
2670                 fput(vma->vm_file);
2671         vma->vm_file = file;
2672         vma->vm_ops = &shmem_vm_ops;
2673         return 0;
2674 }
2675
2676 module_init(init_tmpfs)