mm/shmem.c

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