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