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) 2002-2003 Hugh Dickins.
  10  * Copyright (C) 2002-2003 VERITAS Software Corporation.
  11  * Copyright (C) 2004 Andi Kleen, SuSE Labs
  12  *
  13  * This file is released under the GPL.
  14  */
  15
  16 /*
  17  * This virtual memory filesystem is heavily based on the ramfs. It
  18  * extends ramfs by the ability to use swap and honor resource limits
  19  * which makes it a completely usable filesystem.
  20  */
  21
  22 #include <linux/config.h>
  23 #include <linux/module.h>
  24 #include <linux/init.h>
  25 #include <linux/devfs_fs_kernel.h>
  26 #include <linux/fs.h>
  27 #include <linux/mm.h>
  28 #include <linux/mman.h>
  29 #include <linux/file.h>
  30 #include <linux/swap.h>
  31 #include <linux/pagemap.h>
  32 #include <linux/string.h>
  33 #include <linux/slab.h>
  34 #include <linux/backing-dev.h>
  35 #include <linux/shmem_fs.h>
  36 #include <linux/mount.h>
  37 #include <linux/writeback.h>
  38 #include <linux/vfs.h>
  39 #include <linux/blkdev.h>
  40 #include <linux/security.h>
  41 #include <linux/swapops.h>
  42 #include <linux/mempolicy.h>
  43 #include <linux/namei.h>
  44 #include <asm/uaccess.h>
  45 #include <asm/div64.h>
  46 #include <asm/pgtable.h>
  47
  48 /* This magic number is used in glibc for posix shared memory */
  49 #define TMPFS_MAGIC     0x01021994
  50
  51 #define ENTRIES_PER_PAGE (PAGE_CACHE_SIZE/sizeof(unsigned long))
  52 #define ENTRIES_PER_PAGEPAGE (ENTRIES_PER_PAGE*ENTRIES_PER_PAGE)
  53 #define BLOCKS_PER_PAGE  (PAGE_CACHE_SIZE/512)
  54
  55 #define SHMEM_MAX_INDEX  (SHMEM_NR_DIRECT + (ENTRIES_PER_PAGEPAGE/2) * (ENTRIES_PER_PAGE+1))
  56 #define SHMEM_MAX_BYTES  ((unsigned long long)SHMEM_MAX_INDEX << PAGE_CACHE_SHIFT)
  57
  58 #define VM_ACCT(size)    (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
  59
  60 /* info->flags needs VM_flags to handle pagein/truncate races efficiently */
  61 #define SHMEM_PAGEIN     VM_READ
  62 #define SHMEM_TRUNCATE   VM_WRITE
  63
  64 /* Pretend that each entry is of this size in directory's i_size */
  65 #define BOGO_DIRENT_SIZE 20
  66
  67 /* Keep swapped page count in private field of indirect struct page */
  68 #define nr_swapped              private
  69
  70 /* Flag allocation requirements to shmem_getpage and shmem_swp_alloc */
  71 enum sgp_type {
  72         SGP_QUICK,      /* don't try more than file page cache lookup */
  73         SGP_READ,       /* don't exceed i_size, don't allocate page */
  74         SGP_CACHE,      /* don't exceed i_size, may allocate page */
  75         SGP_WRITE,      /* may exceed i_size, may allocate page */
  76 };
  77
  78 static int shmem_getpage(struct inode *inode, unsigned long idx,
  79                          struct page **pagep, enum sgp_type sgp, int *type);
  80
  81 static inline struct page *shmem_dir_alloc(unsigned int gfp_mask)
  82 {
  83         /*
  84          * The above definition of ENTRIES_PER_PAGE, and the use of
  85          * BLOCKS_PER_PAGE on indirect pages, assume PAGE_CACHE_SIZE:
  86          * might be reconsidered if it ever diverges from PAGE_SIZE.
  87          */
  88         return alloc_pages(gfp_mask, PAGE_CACHE_SHIFT-PAGE_SHIFT);
  89 }
  90
  91 static inline void shmem_dir_free(struct page *page)
  92 {
  93         __free_pages(page, PAGE_CACHE_SHIFT-PAGE_SHIFT);
  94 }
  95
  96 static struct page **shmem_dir_map(struct page *page)
  97 {
  98         return (struct page **)kmap_atomic(page, KM_USER0);
  99 }
 100
 101 static inline void shmem_dir_unmap(struct page **dir)
 102 {
 103         kunmap_atomic(dir, KM_USER0);
 104 }
 105
 106 static swp_entry_t *shmem_swp_map(struct page *page)
 107 {
 108         return (swp_entry_t *)kmap_atomic(page, KM_USER1);
 109 }
 110
 111 static inline void shmem_swp_balance_unmap(void)
 112 {
 113         /*
 114          * When passing a pointer to an i_direct entry, to code which
 115          * also handles indirect entries and so will shmem_swp_unmap,
 116          * we must arrange for the preempt count to remain in balance.
 117          * What kmap_atomic of a lowmem page does depends on config
 118          * and architecture, so pretend to kmap_atomic some lowmem page.
 119          */
 120         (void) kmap_atomic(ZERO_PAGE(0), KM_USER1);
 121 }
 122
 123 static inline void shmem_swp_unmap(swp_entry_t *entry)
 124 {
 125         kunmap_atomic(entry, KM_USER1);
 126 }
 127
 128 static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
 129 {
 130         return sb->s_fs_info;
 131 }
 132
 133 /*
 134  * shmem_file_setup pre-accounts the whole fixed size of a VM object,
 135  * for shared memory and for shared anonymous (/dev/zero) mappings
 136  * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
 137  * consistent with the pre-accounting of private mappings ...
 138  */
 139 static inline int shmem_acct_size(unsigned long flags, loff_t size)
 140 {
 141         return (flags & VM_ACCOUNT)?
 142                 security_vm_enough_memory(VM_ACCT(size)): 0;
 143 }
 144
 145 static inline void shmem_unacct_size(unsigned long flags, loff_t size)
 146 {
 147         if (flags & VM_ACCOUNT)
 148                 vm_unacct_memory(VM_ACCT(size));
 149 }
 150
 151 /*
 152  * ... whereas tmpfs objects are accounted incrementally as
 153  * pages are allocated, in order to allow huge sparse files.
 154  * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
 155  * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
 156  */
 157 static inline int shmem_acct_block(unsigned long flags)
 158 {
 159         return (flags & VM_ACCOUNT)?
 160                 0: security_vm_enough_memory(VM_ACCT(PAGE_CACHE_SIZE));
 161 }
 162
 163 static inline void shmem_unacct_blocks(unsigned long flags, long pages)
 164 {
 165         if (!(flags & VM_ACCOUNT))
 166                 vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
 167 }
 168
 169 static struct super_operations shmem_ops;
 170 static struct address_space_operations shmem_aops;
 171 static struct file_operations shmem_file_operations;
 172 static struct inode_operations shmem_inode_operations;
 173 static struct inode_operations shmem_dir_inode_operations;
 174 static struct vm_operations_struct shmem_vm_ops;
 175
 176 static struct backing_dev_info shmem_backing_dev_info = {
 177         .ra_pages       = 0,    /* No readahead */
 178         .memory_backed  = 1,    /* Does not contribute to dirty memory */
 179         .unplug_io_fn = default_unplug_io_fn,
 180 };
 181
 182 LIST_HEAD(shmem_inodes);
 183 static spinlock_t shmem_ilock = SPIN_LOCK_UNLOCKED;
 184
 185 static void shmem_free_block(struct inode *inode)
 186 {
 187         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 188         spin_lock(&sbinfo->stat_lock);
 189         sbinfo->free_blocks++;
 190         inode->i_blocks -= BLOCKS_PER_PAGE;
 191         spin_unlock(&sbinfo->stat_lock);
 192 }
 193
 194 /*
 195  * shmem_recalc_inode - recalculate the size of an inode
 196  *
 197  * @inode: inode to recalc
 198  *
 199  * We have to calculate the free blocks since the mm can drop
 200  * undirtied hole pages behind our back.
 201  *
 202  * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
 203  * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
 204  *
 205  * It has to be called with the spinlock held.
 206  */
 207 static void shmem_recalc_inode(struct inode *inode)
 208 {
 209         struct shmem_inode_info *info = SHMEM_I(inode);
 210         long freed;
 211
 212         freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
 213         if (freed > 0) {
 214                 struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 215                 info->alloced -= freed;
 216                 spin_lock(&sbinfo->stat_lock);
 217                 sbinfo->free_blocks += freed;
 218                 inode->i_blocks -= freed*BLOCKS_PER_PAGE;
 219                 spin_unlock(&sbinfo->stat_lock);
 220                 shmem_unacct_blocks(info->flags, freed);
 221         }
 222 }
 223
 224 /*
 225  * shmem_swp_entry - find the swap vector position in the info structure
 226  *
 227  * @info:  info structure for the inode
 228  * @index: index of the page to find
 229  * @page:  optional page to add to the structure. Has to be preset to
 230  *         all zeros
 231  *
 232  * If there is no space allocated yet it will return NULL when
 233  * page is NULL, else it will use the page for the needed block,
 234  * setting it to NULL on return to indicate that it has been used.
 235  *
 236  * The swap vector is organized the following way:
 237  *
 238  * There are SHMEM_NR_DIRECT entries directly stored in the
 239  * shmem_inode_info structure. So small files do not need an addional
 240  * allocation.
 241  *
 242  * For pages with index > SHMEM_NR_DIRECT there is the pointer
 243  * i_indirect which points to a page which holds in the first half
 244  * doubly indirect blocks, in the second half triple indirect blocks:
 245  *
 246  * For an artificial ENTRIES_PER_PAGE = 4 this would lead to the
 247  * following layout (for SHMEM_NR_DIRECT == 16):
 248  *
 249  * i_indirect -> dir --> 16-19
 250  *            |      +-> 20-23
 251  *            |
 252  *            +-->dir2 --> 24-27
 253  *            |        +-> 28-31
 254  *            |        +-> 32-35
 255  *            |        +-> 36-39
 256  *            |
 257  *            +-->dir3 --> 40-43
 258  *                     +-> 44-47
 259  *                     +-> 48-51
 260  *                     +-> 52-55
 261  */
 262 static swp_entry_t *shmem_swp_entry(struct shmem_inode_info *info, unsigned long index, struct page **page)
 263 {
 264         unsigned long offset;
 265         struct page **dir;
 266         struct page *subdir;
 267
 268         if (index < SHMEM_NR_DIRECT) {
 269                 shmem_swp_balance_unmap();
 270                 return info->i_direct+index;
 271         }
 272         if (!info->i_indirect) {
 273                 if (page) {
 274                         info->i_indirect = *page;
 275                         *page = NULL;
 276                 }
 277                 return NULL;                    /* need another page */
 278         }
 279
 280         index -= SHMEM_NR_DIRECT;
 281         offset = index % ENTRIES_PER_PAGE;
 282         index /= ENTRIES_PER_PAGE;
 283         dir = shmem_dir_map(info->i_indirect);
 284
 285         if (index >= ENTRIES_PER_PAGE/2) {
 286                 index -= ENTRIES_PER_PAGE/2;
 287                 dir += ENTRIES_PER_PAGE/2 + index/ENTRIES_PER_PAGE;
 288                 index %= ENTRIES_PER_PAGE;
 289                 subdir = *dir;
 290                 if (!subdir) {
 291                         if (page) {
 292                                 *dir = *page;
 293                                 *page = NULL;
 294                         }
 295                         shmem_dir_unmap(dir);
 296                         return NULL;            /* need another page */
 297                 }
 298                 shmem_dir_unmap(dir);
 299                 dir = shmem_dir_map(subdir);
 300         }
 301
 302         dir += index;
 303         subdir = *dir;
 304         if (!subdir) {
 305                 if (!page || !(subdir = *page)) {
 306                         shmem_dir_unmap(dir);
 307                         return NULL;            /* need a page */
 308                 }
 309                 *dir = subdir;
 310                 *page = NULL;
 311         }
 312         shmem_dir_unmap(dir);
 313         return shmem_swp_map(subdir) + offset;
 314 }
 315
 316 static void shmem_swp_set(struct shmem_inode_info *info, swp_entry_t *entry, unsigned long value)
 317 {
 318         long incdec = value? 1: -1;
 319
 320         entry->val = value;
 321         info->swapped += incdec;
 322         if ((unsigned long)(entry - info->i_direct) >= SHMEM_NR_DIRECT)
 323                 kmap_atomic_to_page(entry)->nr_swapped += incdec;
 324 }
 325
 326 /*
 327  * shmem_swp_alloc - get the position of the swap entry for the page.
 328  *                   If it does not exist allocate the entry.
 329  *
 330  * @info:       info structure for the inode
 331  * @index:      index of the page to find
 332  * @sgp:        check and recheck i_size? skip allocation?
 333  */
 334 static swp_entry_t *shmem_swp_alloc(struct shmem_inode_info *info, unsigned long index, enum sgp_type sgp)
 335 {
 336         struct inode *inode = &info->vfs_inode;
 337         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 338         struct page *page = NULL;
 339         swp_entry_t *entry;
 340
 341         if (sgp != SGP_WRITE &&
 342             ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode))
 343                 return ERR_PTR(-EINVAL);
 344
 345         while (!(entry = shmem_swp_entry(info, index, &page))) {
 346                 if (sgp == SGP_READ)
 347                         return shmem_swp_map(ZERO_PAGE(0));
 348                 /*
 349                  * Test free_blocks against 1 not 0, since we have 1 data
 350                  * page (and perhaps indirect index pages) yet to allocate:
 351                  * a waste to allocate index if we cannot allocate data.
 352                  */
 353                 spin_lock(&sbinfo->stat_lock);
 354                 if (sbinfo->free_blocks <= 1) {
 355                         spin_unlock(&sbinfo->stat_lock);
 356                         return ERR_PTR(-ENOSPC);
 357                 }
 358                 sbinfo->free_blocks--;
 359                 inode->i_blocks += BLOCKS_PER_PAGE;
 360                 spin_unlock(&sbinfo->stat_lock);
 361
 362                 spin_unlock(&info->lock);
 363                 page = shmem_dir_alloc(mapping_gfp_mask(inode->i_mapping));
 364                 if (page) {
 365                         clear_highpage(page);
 366                         page->nr_swapped = 0;
 367                 }
 368                 spin_lock(&info->lock);
 369
 370                 if (!page) {
 371                         shmem_free_block(inode);
 372                         return ERR_PTR(-ENOMEM);
 373                 }
 374                 if (sgp != SGP_WRITE &&
 375                     ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
 376                         entry = ERR_PTR(-EINVAL);
 377                         break;
 378                 }
 379                 if (info->next_index <= index)
 380                         info->next_index = index + 1;
 381         }
 382         if (page) {
 383                 /* another task gave its page, or truncated the file */
 384                 shmem_free_block(inode);
 385                 shmem_dir_free(page);
 386         }
 387         if (info->next_index <= index && !IS_ERR(entry))
 388                 info->next_index = index + 1;
 389         return entry;
 390 }
 391
 392 /*
 393  * shmem_free_swp - free some swap entries in a directory
 394  *
 395  * @dir:   pointer to the directory
 396  * @edir:  pointer after last entry of the directory
 397  */
 398 static int shmem_free_swp(swp_entry_t *dir, swp_entry_t *edir)
 399 {
 400         swp_entry_t *ptr;
 401         int freed = 0;
 402
 403         for (ptr = dir; ptr < edir; ptr++) {
 404                 if (ptr->val) {
 405                         free_swap_and_cache(*ptr);
 406                         *ptr = (swp_entry_t){0};
 407                         freed++;
 408                 }
 409         }
 410         return freed;
 411 }
 412
 413 static void shmem_truncate(struct inode *inode)
 414 {
 415         struct shmem_inode_info *info = SHMEM_I(inode);
 416         unsigned long idx;
 417         unsigned long size;
 418         unsigned long limit;
 419         unsigned long stage;
 420         struct page **dir;
 421         struct page *subdir;
 422         struct page *empty;
 423         swp_entry_t *ptr;
 424         int offset;
 425         int freed;
 426
 427         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
 428         idx = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 429         if (idx >= info->next_index)
 430                 return;
 431
 432         spin_lock(&info->lock);
 433         info->flags |= SHMEM_TRUNCATE;
 434         limit = info->next_index;
 435         info->next_index = idx;
 436         if (info->swapped && idx < SHMEM_NR_DIRECT) {
 437                 ptr = info->i_direct;
 438                 size = limit;
 439                 if (size > SHMEM_NR_DIRECT)
 440                         size = SHMEM_NR_DIRECT;
 441                 info->swapped -= shmem_free_swp(ptr+idx, ptr+size);
 442         }
 443         if (!info->i_indirect)
 444                 goto done2;
 445
 446         BUG_ON(limit <= SHMEM_NR_DIRECT);
 447         limit -= SHMEM_NR_DIRECT;
 448         idx = (idx > SHMEM_NR_DIRECT)? (idx - SHMEM_NR_DIRECT): 0;
 449         offset = idx % ENTRIES_PER_PAGE;
 450         idx -= offset;
 451
 452         empty = NULL;
 453         dir = shmem_dir_map(info->i_indirect);
 454         stage = ENTRIES_PER_PAGEPAGE/2;
 455         if (idx < ENTRIES_PER_PAGEPAGE/2)
 456                 dir += idx/ENTRIES_PER_PAGE;
 457         else {
 458                 dir += ENTRIES_PER_PAGE/2;
 459                 dir += (idx - ENTRIES_PER_PAGEPAGE/2)/ENTRIES_PER_PAGEPAGE;
 460                 while (stage <= idx)
 461                         stage += ENTRIES_PER_PAGEPAGE;
 462                 if (*dir) {
 463                         subdir = *dir;
 464                         size = ((idx - ENTRIES_PER_PAGEPAGE/2) %
 465                                 ENTRIES_PER_PAGEPAGE) / ENTRIES_PER_PAGE;
 466                         if (!size && !offset) {
 467                                 empty = subdir;
 468                                 *dir = NULL;
 469                         }
 470                         shmem_dir_unmap(dir);
 471                         dir = shmem_dir_map(subdir) + size;
 472                 } else {
 473                         offset = 0;
 474                         idx = stage;
 475                 }
 476         }
 477
 478         for (; idx < limit; idx += ENTRIES_PER_PAGE, dir++) {
 479                 if (unlikely(idx == stage)) {
 480                         shmem_dir_unmap(dir-1);
 481                         dir = shmem_dir_map(info->i_indirect) +
 482                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
 483                         while (!*dir) {
 484                                 dir++;
 485                                 idx += ENTRIES_PER_PAGEPAGE;
 486                                 if (idx >= limit)
 487                                         goto done1;
 488                         }
 489                         stage = idx + ENTRIES_PER_PAGEPAGE;
 490                         subdir = *dir;
 491                         *dir = NULL;
 492                         shmem_dir_unmap(dir);
 493                         if (empty) {
 494                                 shmem_dir_free(empty);
 495                                 shmem_free_block(inode);
 496                         }
 497                         empty = subdir;
 498                         cond_resched_lock(&info->lock);
 499                         dir = shmem_dir_map(subdir);
 500                 }
 501                 subdir = *dir;
 502                 if (subdir && subdir->nr_swapped) {
 503                         ptr = shmem_swp_map(subdir);
 504                         size = limit - idx;
 505                         if (size > ENTRIES_PER_PAGE)
 506                                 size = ENTRIES_PER_PAGE;
 507                         freed = shmem_free_swp(ptr+offset, ptr+size);
 508                         shmem_swp_unmap(ptr);
 509                         info->swapped -= freed;
 510                         subdir->nr_swapped -= freed;
 511                         BUG_ON(subdir->nr_swapped > offset);
 512                 }
 513                 if (offset)
 514                         offset = 0;
 515                 else if (subdir) {
 516                         *dir = NULL;
 517                         shmem_dir_free(subdir);
 518                         shmem_free_block(inode);
 519                 }
 520         }
 521 done1:
 522         shmem_dir_unmap(dir-1);
 523         if (empty) {
 524                 shmem_dir_free(empty);
 525                 shmem_free_block(inode);
 526         }
 527         if (info->next_index <= SHMEM_NR_DIRECT) {
 528                 shmem_dir_free(info->i_indirect);
 529                 info->i_indirect = NULL;
 530                 shmem_free_block(inode);
 531         }
 532 done2:
 533         BUG_ON(info->swapped > info->next_index);
 534         if (inode->i_mapping->nrpages && (info->flags & SHMEM_PAGEIN)) {
 535                 /*
 536                  * Call truncate_inode_pages again: racing shmem_unuse_inode
 537                  * may have swizzled a page in from swap since vmtruncate or
 538                  * generic_delete_inode did it, before we lowered next_index.
 539                  * Also, though shmem_getpage checks i_size before adding to
 540                  * cache, no recheck after: so fix the narrow window there too.
 541                  */
 542                 spin_unlock(&info->lock);
 543                 truncate_inode_pages(inode->i_mapping, inode->i_size);
 544                 spin_lock(&info->lock);
 545         }
 546         info->flags &= ~SHMEM_TRUNCATE;
 547         shmem_recalc_inode(inode);
 548         spin_unlock(&info->lock);
 549 }
 550
 551 static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
 552 {
 553         struct inode *inode = dentry->d_inode;
 554         struct page *page = NULL;
 555         int error;
 556
 557         if (attr->ia_valid & ATTR_SIZE) {
 558                 if (attr->ia_size < inode->i_size) {
 559                         /*
 560                          * If truncating down to a partial page, then
 561                          * if that page is already allocated, hold it
 562                          * in memory until the truncation is over, so
 563                          * truncate_partial_page cannnot miss it were
 564                          * it assigned to swap.
 565                          */
 566                         if (attr->ia_size & (PAGE_CACHE_SIZE-1)) {
 567                                 (void) shmem_getpage(inode,
 568                                         attr->ia_size>>PAGE_CACHE_SHIFT,
 569                                                 &page, SGP_READ, NULL);
 570                         }
 571                         /*
 572                          * Reset SHMEM_PAGEIN flag so that shmem_truncate can
 573                          * detect if any pages might have been added to cache
 574                          * after truncate_inode_pages.  But we needn't bother
 575                          * if it's being fully truncated to zero-length: the
 576                          * nrpages check is efficient enough in that case.
 577                          */
 578                         if (attr->ia_size) {
 579                                 struct shmem_inode_info *info = SHMEM_I(inode);
 580                                 spin_lock(&info->lock);
 581                                 info->flags &= ~SHMEM_PAGEIN;
 582                                 spin_unlock(&info->lock);
 583                         }
 584                 }
 585         }
 586
 587         error = inode_change_ok(inode, attr);
 588         if (!error)
 589                 error = inode_setattr(inode, attr);
 590         if (page)
 591                 page_cache_release(page);
 592         return error;
 593 }
 594
 595 static void shmem_delete_inode(struct inode *inode)
 596 {
 597         struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 598         struct shmem_inode_info *info = SHMEM_I(inode);
 599
 600         if (inode->i_op->truncate == shmem_truncate) {
 601                 spin_lock(&shmem_ilock);
 602                 list_del(&info->list);
 603                 spin_unlock(&shmem_ilock);
 604                 shmem_unacct_size(info->flags, inode->i_size);
 605                 inode->i_size = 0;
 606                 shmem_truncate(inode);
 607         }
 608         BUG_ON(inode->i_blocks);
 609         spin_lock(&sbinfo->stat_lock);
 610         sbinfo->free_inodes++;
 611         spin_unlock(&sbinfo->stat_lock);
 612         clear_inode(inode);
 613 }
 614
 615 static inline int shmem_find_swp(swp_entry_t entry, swp_entry_t *dir, swp_entry_t *edir)
 616 {
 617         swp_entry_t *ptr;
 618
 619         for (ptr = dir; ptr < edir; ptr++) {
 620                 if (ptr->val == entry.val)
 621                         return ptr - dir;
 622         }
 623         return -1;
 624 }
 625
 626 static int shmem_unuse_inode(struct shmem_inode_info *info, swp_entry_t entry, struct page *page)
 627 {
 628         struct inode *inode;
 629         unsigned long idx;
 630         unsigned long size;
 631         unsigned long limit;
 632         unsigned long stage;
 633         struct page **dir;
 634         struct page *subdir;
 635         swp_entry_t *ptr;
 636         int offset;
 637
 638         idx = 0;
 639         ptr = info->i_direct;
 640         spin_lock(&info->lock);
 641         limit = info->next_index;
 642         size = limit;
 643         if (size > SHMEM_NR_DIRECT)
 644                 size = SHMEM_NR_DIRECT;
 645         offset = shmem_find_swp(entry, ptr, ptr+size);
 646         if (offset >= 0) {
 647                 shmem_swp_balance_unmap();
 648                 goto found;
 649         }
 650         if (!info->i_indirect)
 651                 goto lost2;
 652         /* we might be racing with shmem_truncate */
 653         if (limit <= SHMEM_NR_DIRECT)
 654                 goto lost2;
 655
 656         dir = shmem_dir_map(info->i_indirect);
 657         stage = SHMEM_NR_DIRECT + ENTRIES_PER_PAGEPAGE/2;
 658
 659         for (idx = SHMEM_NR_DIRECT; idx < limit; idx += ENTRIES_PER_PAGE, dir++) {
 660                 if (unlikely(idx == stage)) {
 661                         shmem_dir_unmap(dir-1);
 662                         dir = shmem_dir_map(info->i_indirect) +
 663                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
 664                         while (!*dir) {
 665                                 dir++;
 666                                 idx += ENTRIES_PER_PAGEPAGE;
 667                                 if (idx >= limit)
 668                                         goto lost1;
 669                         }
 670                         stage = idx + ENTRIES_PER_PAGEPAGE;
 671                         subdir = *dir;
 672                         shmem_dir_unmap(dir);
 673                         dir = shmem_dir_map(subdir);
 674                 }
 675                 subdir = *dir;
 676                 if (subdir && subdir->nr_swapped) {
 677                         ptr = shmem_swp_map(subdir);
 678                         size = limit - idx;
 679                         if (size > ENTRIES_PER_PAGE)
 680                                 size = ENTRIES_PER_PAGE;
 681                         offset = shmem_find_swp(entry, ptr, ptr+size);
 682                         if (offset >= 0) {
 683                                 shmem_dir_unmap(dir);
 684                                 goto found;
 685                         }
 686                         shmem_swp_unmap(ptr);
 687                 }
 688         }
 689 lost1:
 690         shmem_dir_unmap(dir-1);
 691 lost2:
 692         spin_unlock(&info->lock);
 693         return 0;
 694 found:
 695         idx += offset;
 696         inode = &info->vfs_inode;
 697         if (move_from_swap_cache(page, idx, inode->i_mapping) == 0) {
 698                 info->flags |= SHMEM_PAGEIN;
 699                 shmem_swp_set(info, ptr + offset, 0);
 700         }
 701         shmem_swp_unmap(ptr);
 702         spin_unlock(&info->lock);
 703         /*
 704          * Decrement swap count even when the entry is left behind:
 705          * try_to_unuse will skip over mms, then reincrement count.
 706          */
 707         swap_free(entry);
 708         return 1;
 709 }
 710
 711 /*
 712  * shmem_unuse() search for an eventually swapped out shmem page.
 713  */
 714 int shmem_unuse(swp_entry_t entry, struct page *page)
 715 {
 716         struct list_head *p;
 717         struct shmem_inode_info *info;
 718         int found = 0;
 719
 720         spin_lock(&shmem_ilock);
 721         list_for_each(p, &shmem_inodes) {
 722                 info = list_entry(p, struct shmem_inode_info, list);
 723
 724                 if (info->swapped && shmem_unuse_inode(info, entry, page)) {
 725                         /* move head to start search for next from here */
 726                         list_move_tail(&shmem_inodes, &info->list);
 727                         found = 1;
 728                         break;
 729                 }
 730         }
 731         spin_unlock(&shmem_ilock);
 732         return found;
 733 }
 734
 735 /*
 736  * Move the page from the page cache to the swap cache.
 737  */
 738 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 739 {
 740         struct shmem_inode_info *info;
 741         swp_entry_t *entry, swap;
 742         struct address_space *mapping;
 743         unsigned long index;
 744         struct inode *inode;
 745
 746         BUG_ON(!PageLocked(page));
 747         BUG_ON(page_mapped(page));
 748
 749         mapping = page->mapping;
 750         index = page->index;
 751         inode = mapping->host;
 752         info = SHMEM_I(inode);
 753         if (info->flags & VM_LOCKED)
 754                 goto redirty;
 755         swap = get_swap_page();
 756         if (!swap.val)
 757                 goto redirty;
 758
 759         spin_lock(&info->lock);
 760         shmem_recalc_inode(inode);
 761         if (index >= info->next_index) {
 762                 BUG_ON(!(info->flags & SHMEM_TRUNCATE));
 763                 goto unlock;
 764         }
 765         entry = shmem_swp_entry(info, index, NULL);
 766         BUG_ON(!entry);
 767         BUG_ON(entry->val);
 768
 769         if (move_to_swap_cache(page, swap) == 0) {
 770                 shmem_swp_set(info, entry, swap.val);
 771                 shmem_swp_unmap(entry);
 772                 spin_unlock(&info->lock);
 773                 unlock_page(page);
 774                 return 0;
 775         }
 776
 777         shmem_swp_unmap(entry);
 778 unlock:
 779         spin_unlock(&info->lock);
 780         swap_free(swap);
 781 redirty:
 782         set_page_dirty(page);
 783         return WRITEPAGE_ACTIVATE;      /* Return with the page locked */
 784 }
 785
 786 #ifdef CONFIG_NUMA
 787 static struct page *shmem_swapin_async(struct shared_policy *p,
 788                                        swp_entry_t entry, unsigned long idx)
 789 {
 790         struct page *page;
 791         struct vm_area_struct pvma;
 792
 793         /* Create a pseudo vma that just contains the policy */
 794         memset(&pvma, 0, sizeof(struct vm_area_struct));
 795         pvma.vm_end = PAGE_SIZE;
 796         pvma.vm_pgoff = idx;
 797         pvma.vm_policy = mpol_shared_policy_lookup(p, idx);
 798         page = read_swap_cache_async(entry, &pvma, 0);
 799         mpol_free(pvma.vm_policy);
 800         return page;
 801 }
 802
 803 struct page *shmem_swapin(struct shmem_inode_info *info, swp_entry_t entry,
 804                           unsigned long idx)
 805 {
 806         struct shared_policy *p = &info->policy;
 807         int i, num;
 808         struct page *page;
 809         unsigned long offset;
 810
 811         num = valid_swaphandles(entry, &offset);
 812         for (i = 0; i < num; offset++, i++) {
 813                 page = shmem_swapin_async(p,
 814                                 swp_entry(swp_type(entry), offset), idx);
 815                 if (!page)
 816                         break;
 817                 page_cache_release(page);
 818         }
 819         lru_add_drain();        /* Push any new pages onto the LRU now */
 820         return shmem_swapin_async(p, entry, idx);
 821 }
 822
 823 static struct page *
 824 shmem_alloc_page(unsigned long gfp, struct shmem_inode_info *info,
 825                  unsigned long idx)
 826 {
 827         struct vm_area_struct pvma;
 828         struct page *page;
 829
 830         memset(&pvma, 0, sizeof(struct vm_area_struct));
 831         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx);
 832         pvma.vm_pgoff = idx;
 833         pvma.vm_end = PAGE_SIZE;
 834         page = alloc_page_vma(gfp, &pvma, 0);
 835         mpol_free(pvma.vm_policy);
 836         return page;
 837 }
 838 #else
 839 static inline struct page *
 840 shmem_swapin(struct shmem_inode_info *info,swp_entry_t entry,unsigned long idx)
 841 {
 842         swapin_readahead(entry, 0, NULL);
 843         return read_swap_cache_async(entry, NULL, 0);
 844 }
 845
 846 static inline struct page *
 847 shmem_alloc_page(unsigned long gfp,struct shmem_inode_info *info,
 848                                  unsigned long idx)
 849 {
 850         return alloc_page(gfp);
 851 }
 852 #endif
 853
 854 /*
 855  * shmem_getpage - either get the page from swap or allocate a new one
 856  *
 857  * If we allocate a new one we do not mark it dirty. That's up to the
 858  * vm. If we swap it in we mark it dirty since we also free the swap
 859  * entry since a page cannot live in both the swap and page cache
 860  */
 861 static int shmem_getpage(struct inode *inode, unsigned long idx,
 862                         struct page **pagep, enum sgp_type sgp, int *type)
 863 {
 864         struct address_space *mapping = inode->i_mapping;
 865         struct shmem_inode_info *info = SHMEM_I(inode);
 866         struct shmem_sb_info *sbinfo;
 867         struct page *filepage = *pagep;
 868         struct page *swappage;
 869         swp_entry_t *entry;
 870         swp_entry_t swap;
 871         int error, majmin = VM_FAULT_MINOR;
 872
 873         if (idx >= SHMEM_MAX_INDEX)
 874                 return -EFBIG;
 875         /*
 876          * Normally, filepage is NULL on entry, and either found
 877          * uptodate immediately, or allocated and zeroed, or read
 878          * in under swappage, which is then assigned to filepage.
 879          * But shmem_prepare_write passes in a locked filepage,
 880          * which may be found not uptodate by other callers too,
 881          * and may need to be copied from the swappage read in.
 882          */
 883 repeat:
 884         if (!filepage)
 885                 filepage = find_lock_page(mapping, idx);
 886         if (filepage && PageUptodate(filepage))
 887                 goto done;
 888         error = 0;
 889         if (sgp == SGP_QUICK)
 890                 goto failed;
 891
 892         spin_lock(&info->lock);
 893         shmem_recalc_inode(inode);
 894         entry = shmem_swp_alloc(info, idx, sgp);
 895         if (IS_ERR(entry)) {
 896                 spin_unlock(&info->lock);
 897                 error = PTR_ERR(entry);
 898                 goto failed;
 899         }
 900         swap = *entry;
 901
 902         if (swap.val) {
 903                 /* Look it up and read it in.. */
 904                 swappage = lookup_swap_cache(swap);
 905                 if (!swappage) {
 906                         shmem_swp_unmap(entry);
 907                         spin_unlock(&info->lock);
 908                         /* here we actually do the io */
 909                         if (majmin == VM_FAULT_MINOR && type)
 910                                 inc_page_state(pgmajfault);
 911                         majmin = VM_FAULT_MAJOR;
 912                         swappage = shmem_swapin(info, swap, idx);
 913                         if (!swappage) {
 914                                 spin_lock(&info->lock);
 915                                 entry = shmem_swp_alloc(info, idx, sgp);
 916                                 if (IS_ERR(entry))
 917                                         error = PTR_ERR(entry);
 918                                 else {
 919                                         if (entry->val == swap.val)
 920                                                 error = -ENOMEM;
 921                                         shmem_swp_unmap(entry);
 922                                 }
 923                                 spin_unlock(&info->lock);
 924                                 if (error)
 925                                         goto failed;
 926                                 goto repeat;
 927                         }
 928                         wait_on_page_locked(swappage);
 929                         page_cache_release(swappage);
 930                         goto repeat;
 931                 }
 932
 933                 /* We have to do this with page locked to prevent races */
 934                 if (TestSetPageLocked(swappage)) {
 935                         shmem_swp_unmap(entry);
 936                         spin_unlock(&info->lock);
 937                         wait_on_page_locked(swappage);
 938                         page_cache_release(swappage);
 939                         goto repeat;
 940                 }
 941                 if (PageWriteback(swappage)) {
 942                         shmem_swp_unmap(entry);
 943                         spin_unlock(&info->lock);
 944                         wait_on_page_writeback(swappage);
 945                         unlock_page(swappage);
 946                         page_cache_release(swappage);
 947                         goto repeat;
 948                 }
 949                 if (!PageUptodate(swappage)) {
 950                         shmem_swp_unmap(entry);
 951                         spin_unlock(&info->lock);
 952                         unlock_page(swappage);
 953                         page_cache_release(swappage);
 954                         error = -EIO;
 955                         goto failed;
 956                 }
 957
 958                 if (filepage) {
 959                         shmem_swp_set(info, entry, 0);
 960                         shmem_swp_unmap(entry);
 961                         delete_from_swap_cache(swappage);
 962                         spin_unlock(&info->lock);
 963                         copy_highpage(filepage, swappage);
 964                         unlock_page(swappage);
 965                         page_cache_release(swappage);
 966                         flush_dcache_page(filepage);
 967                         SetPageUptodate(filepage);
 968                         set_page_dirty(filepage);
 969                         swap_free(swap);
 970                 } else if (!(error = move_from_swap_cache(
 971                                 swappage, idx, mapping))) {
 972                         info->flags |= SHMEM_PAGEIN;
 973                         shmem_swp_set(info, entry, 0);
 974                         shmem_swp_unmap(entry);
 975                         spin_unlock(&info->lock);
 976                         filepage = swappage;
 977                         swap_free(swap);
 978                 } else {
 979                         shmem_swp_unmap(entry);
 980                         spin_unlock(&info->lock);
 981                         unlock_page(swappage);
 982                         page_cache_release(swappage);
 983                         if (error == -ENOMEM) {
 984                                 /* let kswapd refresh zone for GFP_ATOMICs */
 985                                 blk_congestion_wait(WRITE, HZ/50);
 986                         }
 987                         goto repeat;
 988                 }
 989         } else if (sgp == SGP_READ && !filepage) {
 990                 shmem_swp_unmap(entry);
 991                 filepage = find_get_page(mapping, idx);
 992                 if (filepage &&
 993                     (!PageUptodate(filepage) || TestSetPageLocked(filepage))) {
 994                         spin_unlock(&info->lock);
 995                         wait_on_page_locked(filepage);
 996                         page_cache_release(filepage);
 997                         filepage = NULL;
 998                         goto repeat;
 999                 }
1000                 spin_unlock(&info->lock);
1001         } else {
1002                 shmem_swp_unmap(entry);
1003                 sbinfo = SHMEM_SB(inode->i_sb);
1004                 spin_lock(&sbinfo->stat_lock);
1005                 if (sbinfo->free_blocks == 0 || shmem_acct_block(info->flags)) {
1006                         spin_unlock(&sbinfo->stat_lock);
1007                         spin_unlock(&info->lock);
1008                         error = -ENOSPC;
1009                         goto failed;
1010                 }
1011                 sbinfo->free_blocks--;
1012                 inode->i_blocks += BLOCKS_PER_PAGE;
1013                 spin_unlock(&sbinfo->stat_lock);
1014
1015                 if (!filepage) {
1016                         spin_unlock(&info->lock);
1017                         filepage = shmem_alloc_page(mapping_gfp_mask(mapping),
1018                                                     info,
1019                                                     idx);
1020                         if (!filepage) {
1021                                 shmem_unacct_blocks(info->flags, 1);
1022                                 shmem_free_block(inode);
1023                                 error = -ENOMEM;
1024                                 goto failed;
1025                         }
1026
1027                         spin_lock(&info->lock);
1028                         entry = shmem_swp_alloc(info, idx, sgp);
1029                         if (IS_ERR(entry))
1030                                 error = PTR_ERR(entry);
1031                         else {
1032                                 swap = *entry;
1033                                 shmem_swp_unmap(entry);
1034                         }
1035                         if (error || swap.val || 0 != add_to_page_cache_lru(
1036                                         filepage, mapping, idx, GFP_ATOMIC)) {
1037                                 spin_unlock(&info->lock);
1038                                 page_cache_release(filepage);
1039                                 shmem_unacct_blocks(info->flags, 1);
1040                                 shmem_free_block(inode);
1041                                 filepage = NULL;
1042                                 if (error)
1043                                         goto failed;
1044                                 goto repeat;
1045                         }
1046                         info->flags |= SHMEM_PAGEIN;
1047                 }
1048
1049                 info->alloced++;
1050                 spin_unlock(&info->lock);
1051                 clear_highpage(filepage);
1052                 flush_dcache_page(filepage);
1053                 SetPageUptodate(filepage);
1054         }
1055 done:
1056         if (!*pagep) {
1057                 if (filepage) {
1058                         unlock_page(filepage);
1059                         *pagep = filepage;
1060                 } else
1061                         *pagep = ZERO_PAGE(0);
1062         }
1063         if (type)
1064                 *type = majmin;
1065         return 0;
1066
1067 failed:
1068         if (*pagep != filepage) {
1069                 unlock_page(filepage);
1070                 page_cache_release(filepage);
1071         }
1072         return error;
1073 }
1074
1075 struct page *shmem_nopage(struct vm_area_struct *vma, unsigned long address, int *type)
1076 {
1077         struct inode *inode = vma->vm_file->f_dentry->d_inode;
1078         struct page *page = NULL;
1079         unsigned long idx;
1080         int error;
1081
1082         idx = (address - vma->vm_start) >> PAGE_SHIFT;
1083         idx += vma->vm_pgoff;
1084         idx >>= PAGE_CACHE_SHIFT - PAGE_SHIFT;
1085
1086         error = shmem_getpage(inode, idx, &page, SGP_CACHE, type);
1087         if (error)
1088                 return (error == -ENOMEM)? NOPAGE_OOM: NOPAGE_SIGBUS;
1089
1090         mark_page_accessed(page);
1091         return page;
1092 }
1093
1094 static int shmem_populate(struct vm_area_struct *vma,
1095         unsigned long addr, unsigned long len,
1096         pgprot_t prot, unsigned long pgoff, int nonblock)
1097 {
1098         struct inode *inode = vma->vm_file->f_dentry->d_inode;
1099         struct mm_struct *mm = vma->vm_mm;
1100         enum sgp_type sgp = nonblock? SGP_QUICK: SGP_CACHE;
1101         unsigned long size;
1102
1103         size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
1104         if (pgoff >= size || pgoff + (len >> PAGE_SHIFT) > size)
1105                 return -EINVAL;
1106
1107         while ((long) len > 0) {
1108                 struct page *page = NULL;
1109                 int err;
1110                 /*
1111                  * Will need changing if PAGE_CACHE_SIZE != PAGE_SIZE
1112                  */
1113                 err = shmem_getpage(inode, pgoff, &page, sgp, NULL);
1114                 if (err)
1115                         return err;
1116                 if (page) {
1117                         mark_page_accessed(page);
1118                         err = install_page(mm, vma, addr, page, prot);
1119                         if (err) {
1120                                 page_cache_release(page);
1121                                 return err;
1122                         }
1123                 } else if (nonblock) {
1124                         err = install_file_pte(mm, vma, addr, pgoff, prot);
1125                         if (err)
1126                                 return err;
1127                 }
1128
1129                 len -= PAGE_SIZE;
1130                 addr += PAGE_SIZE;
1131                 pgoff++;
1132         }
1133         return 0;
1134 }
1135
1136 #ifdef CONFIG_NUMA
1137 int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *new)
1138 {
1139         struct inode *i = vma->vm_file->f_dentry->d_inode;
1140         return mpol_set_shared_policy(&SHMEM_I(i)->policy, vma, new);
1141 }
1142
1143 struct mempolicy *
1144 shmem_get_policy(struct vm_area_struct *vma, unsigned long addr)
1145 {
1146         struct inode *i = vma->vm_file->f_dentry->d_inode;
1147         unsigned long idx;
1148
1149         idx = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1150         return mpol_shared_policy_lookup(&SHMEM_I(i)->policy, idx);
1151 }
1152 #endif
1153
1154 void shmem_lock(struct file *file, int lock)
1155 {
1156         struct inode *inode = file->f_dentry->d_inode;
1157         struct shmem_inode_info *info = SHMEM_I(inode);
1158
1159         spin_lock(&info->lock);
1160         if (lock)
1161                 info->flags |= VM_LOCKED;
1162         else
1163                 info->flags &= ~VM_LOCKED;
1164         spin_unlock(&info->lock);
1165 }
1166
1167 static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1168 {
1169         file_accessed(file);
1170         vma->vm_ops = &shmem_vm_ops;
1171         return 0;
1172 }
1173
1174 static struct inode *
1175 shmem_get_inode(struct super_block *sb, int mode, dev_t dev)
1176 {
1177         struct inode *inode;
1178         struct shmem_inode_info *info;
1179         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1180
1181         spin_lock(&sbinfo->stat_lock);
1182         if (!sbinfo->free_inodes) {
1183                 spin_unlock(&sbinfo->stat_lock);
1184                 return NULL;
1185         }
1186         sbinfo->free_inodes--;
1187         spin_unlock(&sbinfo->stat_lock);
1188
1189         inode = new_inode(sb);
1190         if (inode) {
1191                 inode->i_mode = mode;
1192                 inode->i_uid = current->fsuid;
1193                 inode->i_gid = current->fsgid;
1194                 inode->i_blksize = PAGE_CACHE_SIZE;
1195                 inode->i_blocks = 0;
1196                 inode->i_mapping->a_ops = &shmem_aops;
1197                 inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1198                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1199                 info = SHMEM_I(inode);
1200                 memset(info, 0, (char *)inode - (char *)info);
1201                 spin_lock_init(&info->lock);
1202                 mpol_shared_policy_init(&info->policy);
1203                 switch (mode & S_IFMT) {
1204                 default:
1205                         init_special_inode(inode, mode, dev);
1206                         break;
1207                 case S_IFREG:
1208                         inode->i_op = &shmem_inode_operations;
1209                         inode->i_fop = &shmem_file_operations;
1210                         spin_lock(&shmem_ilock);
1211                         list_add_tail(&info->list, &shmem_inodes);
1212                         spin_unlock(&shmem_ilock);
1213                         break;
1214                 case S_IFDIR:
1215                         inode->i_nlink++;
1216                         /* Some things misbehave if size == 0 on a directory */
1217                         inode->i_size = 2 * BOGO_DIRENT_SIZE;
1218                         inode->i_op = &shmem_dir_inode_operations;
1219                         inode->i_fop = &simple_dir_operations;
1220                         break;
1221                 case S_IFLNK:
1222                         break;
1223                 }
1224         }
1225         return inode;
1226 }
1227
1228 static int shmem_set_size(struct shmem_sb_info *info,
1229                           unsigned long max_blocks, unsigned long max_inodes)
1230 {
1231         int error;
1232         unsigned long blocks, inodes;
1233
1234         spin_lock(&info->stat_lock);
1235         blocks = info->max_blocks - info->free_blocks;
1236         inodes = info->max_inodes - info->free_inodes;
1237         error = -EINVAL;
1238         if (max_blocks < blocks)
1239                 goto out;
1240         if (max_inodes < inodes)
1241                 goto out;
1242         error = 0;
1243         info->max_blocks  = max_blocks;
1244         info->free_blocks = max_blocks - blocks;
1245         info->max_inodes  = max_inodes;
1246         info->free_inodes = max_inodes - inodes;
1247 out:
1248         spin_unlock(&info->stat_lock);
1249         return error;
1250 }
1251
1252 #ifdef CONFIG_TMPFS
1253
1254 static struct inode_operations shmem_symlink_inode_operations;
1255 static struct inode_operations shmem_symlink_inline_operations;
1256
1257 /*
1258  * Normally tmpfs makes no use of shmem_prepare_write, but it
1259  * lets a tmpfs file be used read-write below the loop driver.
1260  */
1261 static int
1262 shmem_prepare_write(struct file *file, struct page *page, unsigned offset, unsigned to)
1263 {
1264         struct inode *inode = page->mapping->host;
1265         return shmem_getpage(inode, page->index, &page, SGP_WRITE, NULL);
1266 }
1267
1268 static ssize_t
1269 shmem_file_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
1270 {
1271         struct inode    *inode = file->f_dentry->d_inode;
1272         loff_t          pos;
1273         unsigned long   written;
1274         int             err;
1275
1276         if ((ssize_t) count < 0)
1277                 return -EINVAL;
1278
1279         if (!access_ok(VERIFY_READ, buf, count))
1280                 return -EFAULT;
1281
1282         down(&inode->i_sem);
1283
1284         pos = *ppos;
1285         written = 0;
1286
1287         err = generic_write_checks(file, &pos, &count, 0);
1288         if (err || !count)
1289                 goto out;
1290
1291         err = remove_suid(file->f_dentry);
1292         if (err)
1293                 goto out;
1294
1295         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
1296
1297         do {
1298                 struct page *page = NULL;
1299                 unsigned long bytes, index, offset;
1300                 char *kaddr;
1301                 int left;
1302
1303                 offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
1304                 index = pos >> PAGE_CACHE_SHIFT;
1305                 bytes = PAGE_CACHE_SIZE - offset;
1306                 if (bytes > count)
1307                         bytes = count;
1308
1309                 /*
1310                  * We don't hold page lock across copy from user -
1311                  * what would it guard against? - so no deadlock here.
1312                  * But it still may be a good idea to prefault below.
1313                  */
1314
1315                 err = shmem_getpage(inode, index, &page, SGP_WRITE, NULL);
1316                 if (err)
1317                         break;
1318
1319                 left = bytes;
1320                 if (PageHighMem(page)) {
1321                         volatile unsigned char dummy;
1322                         __get_user(dummy, buf);
1323                         __get_user(dummy, buf + bytes - 1);
1324
1325                         kaddr = kmap_atomic(page, KM_USER0);
1326                         left = __copy_from_user(kaddr + offset, buf, bytes);
1327                         kunmap_atomic(kaddr, KM_USER0);
1328                 }
1329                 if (left) {
1330                         kaddr = kmap(page);
1331                         left = __copy_from_user(kaddr + offset, buf, bytes);
1332                         kunmap(page);
1333                 }
1334
1335                 written += bytes;
1336                 count -= bytes;
1337                 pos += bytes;
1338                 buf += bytes;
1339                 if (pos > inode->i_size)
1340                         i_size_write(inode, pos);
1341
1342                 flush_dcache_page(page);
1343                 set_page_dirty(page);
1344                 mark_page_accessed(page);
1345                 page_cache_release(page);
1346
1347                 if (left) {
1348                         pos -= left;
1349                         written -= left;
1350                         err = -EFAULT;
1351                         break;
1352                 }
1353
1354                 /*
1355                  * Our dirty pages are not counted in nr_dirty,
1356                  * and we do not attempt to balance dirty pages.
1357                  */
1358
1359                 cond_resched();
1360         } while (count);
1361
1362         *ppos = pos;
1363         if (written)
1364                 err = written;
1365 out:
1366         up(&inode->i_sem);
1367         return err;
1368 }
1369
1370 static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
1371 {
1372         struct inode *inode = filp->f_dentry->d_inode;
1373         struct address_space *mapping = inode->i_mapping;
1374         unsigned long index, offset;
1375
1376         index = *ppos >> PAGE_CACHE_SHIFT;
1377         offset = *ppos & ~PAGE_CACHE_MASK;
1378
1379         for (;;) {
1380                 struct page *page = NULL;
1381                 unsigned long end_index, nr, ret;
1382                 loff_t i_size = i_size_read(inode);
1383
1384                 end_index = i_size >> PAGE_CACHE_SHIFT;
1385                 if (index > end_index)
1386                         break;
1387                 if (index == end_index) {
1388                         nr = i_size & ~PAGE_CACHE_MASK;
1389                         if (nr <= offset)
1390                                 break;
1391                 }
1392
1393                 desc->error = shmem_getpage(inode, index, &page, SGP_READ, NULL);
1394                 if (desc->error) {
1395                         if (desc->error == -EINVAL)
1396                                 desc->error = 0;
1397                         break;
1398                 }
1399
1400                 /*
1401                  * We must evaluate after, since reads (unlike writes)
1402                  * are called without i_sem protection against truncate
1403                  */
1404                 nr = PAGE_CACHE_SIZE;
1405                 i_size = i_size_read(inode);
1406                 end_index = i_size >> PAGE_CACHE_SHIFT;
1407                 if (index == end_index) {
1408                         nr = i_size & ~PAGE_CACHE_MASK;
1409                         if (nr <= offset) {
1410                                 page_cache_release(page);
1411                                 break;
1412                         }
1413                 }
1414                 nr -= offset;
1415
1416                 if (page != ZERO_PAGE(0)) {
1417                         /*
1418                          * If users can be writing to this page using arbitrary
1419                          * virtual addresses, take care about potential aliasing
1420                          * before reading the page on the kernel side.
1421                          */
1422                         if (mapping_writably_mapped(mapping))
1423                                 flush_dcache_page(page);
1424                         /*
1425                          * Mark the page accessed if we read the beginning.
1426                          */
1427                         if (!offset)
1428                                 mark_page_accessed(page);
1429                 }
1430
1431                 /*
1432                  * Ok, we have the page, and it's up-to-date, so
1433                  * now we can copy it to user space...
1434                  *
1435                  * The actor routine returns how many bytes were actually used..
1436                  * NOTE! This may not be the same as how much of a user buffer
1437                  * we filled up (we may be padding etc), so we can only update
1438                  * "pos" here (the actor routine has to update the user buffer
1439                  * pointers and the remaining count).
1440                  */
1441                 ret = actor(desc, page, offset, nr);
1442                 offset += ret;
1443                 index += offset >> PAGE_CACHE_SHIFT;
1444                 offset &= ~PAGE_CACHE_MASK;
1445
1446                 page_cache_release(page);
1447                 if (ret != nr || !desc->count)
1448                         break;
1449
1450                 cond_resched();
1451         }
1452
1453         *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1454         file_accessed(filp);
1455 }
1456
1457 static ssize_t shmem_file_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
1458 {
1459         read_descriptor_t desc;
1460
1461         if ((ssize_t) count < 0)
1462                 return -EINVAL;
1463         if (!access_ok(VERIFY_WRITE, buf, count))
1464                 return -EFAULT;
1465         if (!count)
1466                 return 0;
1467
1468         desc.written = 0;
1469         desc.count = count;
1470         desc.arg.buf = buf;
1471         desc.error = 0;
1472
1473         do_shmem_file_read(filp, ppos, &desc, file_read_actor);
1474         if (desc.written)
1475                 return desc.written;
1476         return desc.error;
1477 }
1478
1479 static ssize_t shmem_file_sendfile(struct file *in_file, loff_t *ppos,
1480                          size_t count, read_actor_t actor, void *target)
1481 {
1482         read_descriptor_t desc;
1483
1484         if (!count)
1485                 return 0;
1486
1487         desc.written = 0;
1488         desc.count = count;
1489         desc.arg.data = target;
1490         desc.error = 0;
1491
1492         do_shmem_file_read(in_file, ppos, &desc, actor);
1493         if (desc.written)
1494                 return desc.written;
1495         return desc.error;
1496 }
1497
1498 static int shmem_statfs(struct super_block *sb, struct kstatfs *buf)
1499 {
1500         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1501
1502         buf->f_type = TMPFS_MAGIC;
1503         buf->f_bsize = PAGE_CACHE_SIZE;
1504         spin_lock(&sbinfo->stat_lock);
1505         buf->f_blocks = sbinfo->max_blocks;
1506         buf->f_bavail = buf->f_bfree = sbinfo->free_blocks;
1507         buf->f_files = sbinfo->max_inodes;
1508         buf->f_ffree = sbinfo->free_inodes;
1509         spin_unlock(&sbinfo->stat_lock);
1510         buf->f_namelen = NAME_MAX;
1511         return 0;
1512 }
1513
1514 /*
1515  * File creation. Allocate an inode, and we're done..
1516  */
1517 static int
1518 shmem_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
1519 {
1520         struct inode *inode = shmem_get_inode(dir->i_sb, mode, dev);
1521         int error = -ENOSPC;
1522
1523         if (inode) {
1524                 if (dir->i_mode & S_ISGID) {
1525                         inode->i_gid = dir->i_gid;
1526                         if (S_ISDIR(mode))
1527                                 inode->i_mode |= S_ISGID;
1528                 }
1529                 dir->i_size += BOGO_DIRENT_SIZE;
1530                 dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1531                 d_instantiate(dentry, inode);
1532                 dget(dentry); /* Extra count - pin the dentry in core */
1533                 error = 0;
1534         }
1535         return error;
1536 }
1537
1538 static int shmem_mkdir(struct inode *dir, struct dentry *dentry, int mode)
1539 {
1540         int error;
1541
1542         if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
1543                 return error;
1544         dir->i_nlink++;
1545         return 0;
1546 }
1547
1548 static int shmem_create(struct inode *dir, struct dentry *dentry, int mode,
1549                 struct nameidata *nd)
1550 {
1551         return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
1552 }
1553
1554 /*
1555  * Link a file..
1556  */
1557 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
1558 {
1559         struct inode *inode = old_dentry->d_inode;
1560
1561         dir->i_size += BOGO_DIRENT_SIZE;
1562         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1563         inode->i_nlink++;
1564         atomic_inc(&inode->i_count);    /* New dentry reference */
1565         dget(dentry);           /* Extra pinning count for the created dentry */
1566         d_instantiate(dentry, inode);
1567         return 0;
1568 }
1569
1570 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
1571 {
1572         struct inode *inode = dentry->d_inode;
1573
1574         dir->i_size -= BOGO_DIRENT_SIZE;
1575         inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1576         inode->i_nlink--;
1577         dput(dentry);   /* Undo the count from "create" - this does all the work */
1578         return 0;
1579 }
1580
1581 static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
1582 {
1583         if (!simple_empty(dentry))
1584                 return -ENOTEMPTY;
1585
1586         dir->i_nlink--;
1587         return shmem_unlink(dir, dentry);
1588 }
1589
1590 /*
1591  * The VFS layer already does all the dentry stuff for rename,
1592  * we just have to decrement the usage count for the target if
1593  * it exists so that the VFS layer correctly free's it when it
1594  * gets overwritten.
1595  */
1596 static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
1597 {
1598         struct inode *inode = old_dentry->d_inode;
1599         int they_are_dirs = S_ISDIR(inode->i_mode);
1600
1601         if (!simple_empty(new_dentry))
1602                 return -ENOTEMPTY;
1603
1604         if (new_dentry->d_inode) {
1605                 (void) shmem_unlink(new_dir, new_dentry);
1606                 if (they_are_dirs)
1607                         old_dir->i_nlink--;
1608         } else if (they_are_dirs) {
1609                 old_dir->i_nlink--;
1610                 new_dir->i_nlink++;
1611         }
1612
1613         old_dir->i_size -= BOGO_DIRENT_SIZE;
1614         new_dir->i_size += BOGO_DIRENT_SIZE;
1615         old_dir->i_ctime = old_dir->i_mtime =
1616         new_dir->i_ctime = new_dir->i_mtime =
1617         inode->i_ctime = CURRENT_TIME;
1618         return 0;
1619 }
1620
1621 static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
1622 {
1623         int error;
1624         int len;
1625         struct inode *inode;
1626         struct page *page = NULL;
1627         char *kaddr;
1628         struct shmem_inode_info *info;
1629
1630         len = strlen(symname) + 1;
1631         if (len > PAGE_CACHE_SIZE)
1632                 return -ENAMETOOLONG;
1633
1634         inode = shmem_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0);
1635         if (!inode)
1636                 return -ENOSPC;
1637
1638         info = SHMEM_I(inode);
1639         inode->i_size = len-1;
1640         if (len <= (char *)inode - (char *)info) {
1641                 /* do it inline */
1642                 memcpy(info, symname, len);
1643                 inode->i_op = &shmem_symlink_inline_operations;
1644         } else {
1645                 error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
1646                 if (error) {
1647                         iput(inode);
1648                         return error;
1649                 }
1650                 inode->i_op = &shmem_symlink_inode_operations;
1651                 spin_lock(&shmem_ilock);
1652                 list_add_tail(&info->list, &shmem_inodes);
1653                 spin_unlock(&shmem_ilock);
1654                 kaddr = kmap_atomic(page, KM_USER0);
1655                 memcpy(kaddr, symname, len);
1656                 kunmap_atomic(kaddr, KM_USER0);
1657                 set_page_dirty(page);
1658                 page_cache_release(page);
1659         }
1660         if (dir->i_mode & S_ISGID)
1661                 inode->i_gid = dir->i_gid;
1662         dir->i_size += BOGO_DIRENT_SIZE;
1663         dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1664         d_instantiate(dentry, inode);
1665         dget(dentry);
1666         return 0;
1667 }
1668
1669 static int shmem_follow_link_inline(struct dentry *dentry, struct nameidata *nd)
1670 {
1671         nd_set_link(nd, (char *)SHMEM_I(dentry->d_inode));
1672         return 0;
1673 }
1674
1675 static int shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
1676 {
1677         struct page *page = NULL;
1678         int res = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
1679         nd_set_link(nd, res ? ERR_PTR(res) : kmap(page));
1680         return 0;
1681 }
1682
1683 static void shmem_put_link(struct dentry *dentry, struct nameidata *nd)
1684 {
1685         if (!IS_ERR(nd_get_link(nd))) {
1686                 struct page *page;
1687
1688                 page = find_get_page(dentry->d_inode->i_mapping, 0);
1689                 if (!page)
1690                         BUG();
1691                 kunmap(page);
1692                 mark_page_accessed(page);
1693                 page_cache_release(page);
1694                 page_cache_release(page);
1695         }
1696 }
1697
1698 static struct inode_operations shmem_symlink_inline_operations = {
1699         .readlink       = generic_readlink,
1700         .follow_link    = shmem_follow_link_inline,
1701 };
1702
1703 static struct inode_operations shmem_symlink_inode_operations = {
1704         .truncate       = shmem_truncate,
1705         .readlink       = generic_readlink,
1706         .follow_link    = shmem_follow_link,
1707         .put_link       = shmem_put_link,
1708 };
1709
1710 static int shmem_parse_options(char *options, int *mode, uid_t *uid, gid_t *gid, unsigned long *blocks, unsigned long *inodes)
1711 {
1712         char *this_char, *value, *rest;
1713
1714         while ((this_char = strsep(&options, ",")) != NULL) {
1715                 if (!*this_char)
1716                         continue;
1717                 if ((value = strchr(this_char,'=')) != NULL) {
1718                         *value++ = 0;
1719                 } else {
1720                         printk(KERN_ERR
1721                             "tmpfs: No value for mount option '%s'\n",
1722                             this_char);
1723                         return 1;
1724                 }
1725
1726                 if (!strcmp(this_char,"size")) {
1727                         unsigned long long size;
1728                         size = memparse(value,&rest);
1729                         if (*rest == '%') {
1730                                 size <<= PAGE_SHIFT;
1731                                 size *= totalram_pages;
1732                                 do_div(size, 100);
1733                                 rest++;
1734                         }
1735                         if (*rest)
1736                                 goto bad_val;
1737                         *blocks = size >> PAGE_CACHE_SHIFT;
1738                 } else if (!strcmp(this_char,"nr_blocks")) {
1739                         *blocks = memparse(value,&rest);
1740                         if (*rest)
1741                                 goto bad_val;
1742                 } else if (!strcmp(this_char,"nr_inodes")) {
1743                         *inodes = memparse(value,&rest);
1744                         if (*rest)
1745                                 goto bad_val;
1746                 } else if (!strcmp(this_char,"mode")) {
1747                         if (!mode)
1748                                 continue;
1749                         *mode = simple_strtoul(value,&rest,8);
1750                         if (*rest)
1751                                 goto bad_val;
1752                 } else if (!strcmp(this_char,"uid")) {
1753                         if (!uid)
1754                                 continue;
1755                         *uid = simple_strtoul(value,&rest,0);
1756                         if (*rest)
1757                                 goto bad_val;
1758                 } else if (!strcmp(this_char,"gid")) {
1759                         if (!gid)
1760                                 continue;
1761                         *gid = simple_strtoul(value,&rest,0);
1762                         if (*rest)
1763                                 goto bad_val;
1764                 } else {
1765                         printk(KERN_ERR "tmpfs: Bad mount option %s\n",
1766                                this_char);
1767                         return 1;
1768                 }
1769         }
1770         return 0;
1771
1772 bad_val:
1773         printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
1774                value, this_char);
1775         return 1;
1776
1777 }
1778
1779 static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
1780 {
1781         struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1782         unsigned long max_blocks = sbinfo->max_blocks;
1783         unsigned long max_inodes = sbinfo->max_inodes;
1784
1785         if (shmem_parse_options(data, NULL, NULL, NULL, &max_blocks, &max_inodes))
1786                 return -EINVAL;
1787         return shmem_set_size(sbinfo, max_blocks, max_inodes);
1788 }
1789 #endif
1790
1791 static int shmem_fill_super(struct super_block *sb,
1792                             void *data, int silent)
1793 {
1794         struct inode *inode;
1795         struct dentry *root;
1796         unsigned long blocks, inodes;
1797         int mode   = S_IRWXUGO | S_ISVTX;
1798         uid_t uid = current->fsuid;
1799         gid_t gid = current->fsgid;
1800         struct shmem_sb_info *sbinfo;
1801         int err = -ENOMEM;
1802
1803         sbinfo = kmalloc(sizeof(struct shmem_sb_info), GFP_KERNEL);
1804         if (!sbinfo)
1805                 return -ENOMEM;
1806         sb->s_fs_info = sbinfo;
1807         memset(sbinfo, 0, sizeof(struct shmem_sb_info));
1808
1809         /*
1810          * Per default we only allow half of the physical ram per
1811          * tmpfs instance
1812          */
1813         blocks = inodes = totalram_pages / 2;
1814
1815 #ifdef CONFIG_TMPFS
1816         if (shmem_parse_options(data, &mode, &uid, &gid, &blocks, &inodes)) {
1817                 err = -EINVAL;
1818                 goto failed;
1819         }
1820 #else
1821         sb->s_flags |= MS_NOUSER;
1822 #endif
1823
1824         spin_lock_init(&sbinfo->stat_lock);
1825         sbinfo->max_blocks = blocks;
1826         sbinfo->free_blocks = blocks;
1827         sbinfo->max_inodes = inodes;
1828         sbinfo->free_inodes = inodes;
1829         sb->s_maxbytes = SHMEM_MAX_BYTES;
1830         sb->s_blocksize = PAGE_CACHE_SIZE;
1831         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
1832         sb->s_magic = TMPFS_MAGIC;
1833         sb->s_op = &shmem_ops;
1834         inode = shmem_get_inode(sb, S_IFDIR | mode, 0);
1835         if (!inode)
1836                 goto failed;
1837         inode->i_uid = uid;
1838         inode->i_gid = gid;
1839         root = d_alloc_root(inode);
1840         if (!root)
1841                 goto failed_iput;
1842         sb->s_root = root;
1843         return 0;
1844
1845 failed_iput:
1846         iput(inode);
1847 failed:
1848         kfree(sbinfo);
1849         sb->s_fs_info = NULL;
1850         return err;
1851 }
1852
1853 static void shmem_put_super(struct super_block *sb)
1854 {
1855         kfree(sb->s_fs_info);
1856         sb->s_fs_info = NULL;
1857 }
1858
1859 static kmem_cache_t *shmem_inode_cachep;
1860
1861 static struct inode *shmem_alloc_inode(struct super_block *sb)
1862 {
1863         struct shmem_inode_info *p;
1864         p = (struct shmem_inode_info *)kmem_cache_alloc(shmem_inode_cachep, SLAB_KERNEL);
1865         if (!p)
1866                 return NULL;
1867         return &p->vfs_inode;
1868 }
1869
1870 static void shmem_destroy_inode(struct inode *inode)
1871 {
1872         mpol_free_shared_policy(&SHMEM_I(inode)->policy);
1873         kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
1874 }
1875
1876 static void init_once(void *foo, kmem_cache_t *cachep, unsigned long flags)
1877 {
1878         struct shmem_inode_info *p = (struct shmem_inode_info *) foo;
1879
1880         if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
1881             SLAB_CTOR_CONSTRUCTOR) {
1882                 inode_init_once(&p->vfs_inode);
1883         }
1884 }
1885
1886 static int init_inodecache(void)
1887 {
1888         shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
1889                                 sizeof(struct shmem_inode_info),
1890                                 0, SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT,
1891                                 init_once, NULL);
1892         if (shmem_inode_cachep == NULL)
1893                 return -ENOMEM;
1894         return 0;
1895 }
1896
1897 static void destroy_inodecache(void)
1898 {
1899         if (kmem_cache_destroy(shmem_inode_cachep))
1900                 printk(KERN_INFO "shmem_inode_cache: not all structures were freed\n");
1901 }
1902
1903 static struct address_space_operations shmem_aops = {
1904         .writepage      = shmem_writepage,
1905         .set_page_dirty = __set_page_dirty_nobuffers,
1906 #ifdef CONFIG_TMPFS
1907         .prepare_write  = shmem_prepare_write,
1908         .commit_write   = simple_commit_write,
1909 #endif
1910 };
1911
1912 static struct file_operations shmem_file_operations = {
1913         .mmap           = shmem_mmap,
1914 #ifdef CONFIG_TMPFS
1915         .llseek         = generic_file_llseek,
1916         .read           = shmem_file_read,
1917         .write          = shmem_file_write,
1918         .fsync          = simple_sync_file,
1919         .sendfile       = shmem_file_sendfile,
1920 #endif
1921 };
1922
1923 static struct inode_operations shmem_inode_operations = {
1924         .truncate       = shmem_truncate,
1925         .setattr        = shmem_notify_change,
1926 };
1927
1928 static struct inode_operations shmem_dir_inode_operations = {
1929 #ifdef CONFIG_TMPFS
1930         .create         = shmem_create,
1931         .lookup         = simple_lookup,
1932         .link           = shmem_link,
1933         .unlink         = shmem_unlink,
1934         .symlink        = shmem_symlink,
1935         .mkdir          = shmem_mkdir,
1936         .rmdir          = shmem_rmdir,
1937         .mknod          = shmem_mknod,
1938         .rename         = shmem_rename,
1939 #endif
1940 };
1941
1942 static struct super_operations shmem_ops = {
1943         .alloc_inode    = shmem_alloc_inode,
1944         .destroy_inode  = shmem_destroy_inode,
1945 #ifdef CONFIG_TMPFS
1946         .statfs         = shmem_statfs,
1947         .remount_fs     = shmem_remount_fs,
1948 #endif
1949         .delete_inode   = shmem_delete_inode,
1950         .drop_inode     = generic_delete_inode,
1951         .put_super      = shmem_put_super,
1952 };
1953
1954 static struct vm_operations_struct shmem_vm_ops = {
1955         .nopage         = shmem_nopage,
1956         .populate       = shmem_populate,
1957 #ifdef CONFIG_NUMA
1958         .set_policy     = shmem_set_policy,
1959         .get_policy     = shmem_get_policy,
1960 #endif
1961 };
1962
1963 static struct super_block *shmem_get_sb(struct file_system_type *fs_type,
1964         int flags, const char *dev_name, void *data)
1965 {
1966         return get_sb_nodev(fs_type, flags, data, shmem_fill_super);
1967 }
1968
1969 static struct file_system_type tmpfs_fs_type = {
1970         .owner          = THIS_MODULE,
1971         .name           = "tmpfs",
1972         .get_sb         = shmem_get_sb,
1973         .kill_sb        = kill_litter_super,
1974 };
1975 static struct vfsmount *shm_mnt;
1976
1977 static int __init init_tmpfs(void)
1978 {
1979         int error;
1980
1981         error = init_inodecache();
1982         if (error)
1983                 goto out3;
1984
1985         error = register_filesystem(&tmpfs_fs_type);
1986         if (error) {
1987                 printk(KERN_ERR "Could not register tmpfs\n");
1988                 goto out2;
1989         }
1990 #ifdef CONFIG_TMPFS
1991         devfs_mk_dir("shm");
1992 #endif
1993         shm_mnt = kern_mount(&tmpfs_fs_type);
1994         if (IS_ERR(shm_mnt)) {
1995                 error = PTR_ERR(shm_mnt);
1996                 printk(KERN_ERR "Could not kern_mount tmpfs\n");
1997                 goto out1;
1998         }
1999
2000         /* The internal instance should not do size checking */
2001         shmem_set_size(SHMEM_SB(shm_mnt->mnt_sb), ULONG_MAX, ULONG_MAX);
2002         return 0;
2003
2004 out1:
2005         unregister_filesystem(&tmpfs_fs_type);
2006 out2:
2007         destroy_inodecache();
2008 out3:
2009         shm_mnt = ERR_PTR(error);
2010         return error;
2011 }
2012 module_init(init_tmpfs)
2013
2014 /*
2015  * shmem_file_setup - get an unlinked file living in tmpfs
2016  *
2017  * @name: name for dentry (to be seen in /proc/<pid>/maps
2018  * @size: size to be set for the file
2019  *
2020  */
2021 struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags)
2022 {
2023         int error;
2024         struct file *file;
2025         struct inode *inode;
2026         struct dentry *dentry, *root;
2027         struct qstr this;
2028
2029         if (IS_ERR(shm_mnt))
2030                 return (void *)shm_mnt;
2031
2032         if (size > SHMEM_MAX_BYTES)
2033                 return ERR_PTR(-EINVAL);
2034
2035         if (shmem_acct_size(flags, size))
2036                 return ERR_PTR(-ENOMEM);
2037
2038         error = -ENOMEM;
2039         this.name = name;
2040         this.len = strlen(name);
2041         this.hash = 0; /* will go */
2042         root = shm_mnt->mnt_root;
2043         dentry = d_alloc(root, &this);
2044         if (!dentry)
2045                 goto put_memory;
2046
2047         error = -ENFILE;
2048         file = get_empty_filp();
2049         if (!file)
2050                 goto put_dentry;
2051
2052         error = -ENOSPC;
2053         inode = shmem_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0);
2054         if (!inode)
2055                 goto close_file;
2056
2057         SHMEM_I(inode)->flags = flags & VM_ACCOUNT;
2058         d_instantiate(dentry, inode);
2059         inode->i_size = size;
2060         inode->i_nlink = 0;     /* It is unlinked */
2061         file->f_vfsmnt = mntget(shm_mnt);
2062         file->f_dentry = dentry;
2063         file->f_mapping = inode->i_mapping;
2064         file->f_op = &shmem_file_operations;
2065         file->f_mode = FMODE_WRITE | FMODE_READ;
2066         return(file);
2067
2068 close_file:
2069         put_filp(file);
2070 put_dentry:
2071         dput(dentry);
2072 put_memory:
2073         shmem_unacct_size(flags, size);
2074         return ERR_PTR(error);
2075 }
2076
2077 /*
2078  * shmem_zero_setup - setup a shared anonymous mapping
2079  *
2080  * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
2081  */
2082 int shmem_zero_setup(struct vm_area_struct *vma)
2083 {
2084         struct file *file;
2085         loff_t size = vma->vm_end - vma->vm_start;
2086
2087         file = shmem_file_setup("dev/zero", size, vma->vm_flags);
2088         if (IS_ERR(file))
2089                 return PTR_ERR(file);
2090
2091         if (vma->vm_file)
2092                 fput(vma->vm_file);
2093         vma->vm_file = file;
2094         vma->vm_ops = &shmem_vm_ops;
2095         return 0;
2096 }
2097
2098 EXPORT_SYMBOL(shmem_file_setup);