linux/mm/shmem.c
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   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) 2002-2011 Hugh Dickins.
  10 * Copyright (C) 2011 Google Inc.
  11 * Copyright (C) 2002-2005 VERITAS Software Corporation.
  12 * Copyright (C) 2004 Andi Kleen, SuSE Labs
  13 *
  14 * Extended attribute support for tmpfs:
  15 * Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@lkcl.net>
  16 * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
  17 *
  18 * tiny-shmem:
  19 * Copyright (c) 2004, 2008 Matt Mackall <mpm@selenic.com>
  20 *
  21 * This file is released under the GPL.
  22 */
  23
  24#include <linux/fs.h>
  25#include <linux/init.h>
  26#include <linux/vfs.h>
  27#include <linux/mount.h>
  28#include <linux/pagemap.h>
  29#include <linux/file.h>
  30#include <linux/mm.h>
  31#include <linux/export.h>
  32#include <linux/swap.h>
  33
  34static struct vfsmount *shm_mnt;
  35
  36#ifdef CONFIG_SHMEM
  37/*
  38 * This virtual memory filesystem is heavily based on the ramfs. It
  39 * extends ramfs by the ability to use swap and honor resource limits
  40 * which makes it a completely usable filesystem.
  41 */
  42
  43#include <linux/xattr.h>
  44#include <linux/exportfs.h>
  45#include <linux/posix_acl.h>
  46#include <linux/generic_acl.h>
  47#include <linux/mman.h>
  48#include <linux/string.h>
  49#include <linux/slab.h>
  50#include <linux/backing-dev.h>
  51#include <linux/shmem_fs.h>
  52#include <linux/writeback.h>
  53#include <linux/blkdev.h>
  54#include <linux/pagevec.h>
  55#include <linux/percpu_counter.h>
  56#include <linux/falloc.h>
  57#include <linux/splice.h>
  58#include <linux/security.h>
  59#include <linux/swapops.h>
  60#include <linux/mempolicy.h>
  61#include <linux/namei.h>
  62#include <linux/ctype.h>
  63#include <linux/migrate.h>
  64#include <linux/highmem.h>
  65#include <linux/seq_file.h>
  66#include <linux/magic.h>
  67
  68#include <asm/uaccess.h>
  69#include <asm/pgtable.h>
  70
  71#define BLOCKS_PER_PAGE  (PAGE_CACHE_SIZE/512)
  72#define VM_ACCT(size)    (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
  73
  74/* Pretend that each entry is of this size in directory's i_size */
  75#define BOGO_DIRENT_SIZE 20
  76
  77/* Symlink up to this size is kmalloc'ed instead of using a swappable page */
  78#define SHORT_SYMLINK_LEN 128
  79
  80/*
  81 * shmem_fallocate and shmem_writepage communicate via inode->i_private
  82 * (with i_mutex making sure that it has only one user at a time):
  83 * we would prefer not to enlarge the shmem inode just for that.
  84 */
  85struct shmem_falloc {
  86        pgoff_t start;          /* start of range currently being fallocated */
  87        pgoff_t next;           /* the next page offset to be fallocated */
  88        pgoff_t nr_falloced;    /* how many new pages have been fallocated */
  89        pgoff_t nr_unswapped;   /* how often writepage refused to swap out */
  90};
  91
  92/* Flag allocation requirements to shmem_getpage */
  93enum sgp_type {
  94        SGP_READ,       /* don't exceed i_size, don't allocate page */
  95        SGP_CACHE,      /* don't exceed i_size, may allocate page */
  96        SGP_DIRTY,      /* like SGP_CACHE, but set new page dirty */
  97        SGP_WRITE,      /* may exceed i_size, may allocate !Uptodate page */
  98        SGP_FALLOC,     /* like SGP_WRITE, but make existing page Uptodate */
  99};
 100
 101#ifdef CONFIG_TMPFS
 102static unsigned long shmem_default_max_blocks(void)
 103{
 104        return totalram_pages / 2;
 105}
 106
 107static unsigned long shmem_default_max_inodes(void)
 108{
 109        return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
 110}
 111#endif
 112
 113static bool shmem_should_replace_page(struct page *page, gfp_t gfp);
 114static int shmem_replace_page(struct page **pagep, gfp_t gfp,
 115                                struct shmem_inode_info *info, pgoff_t index);
 116static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
 117        struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type);
 118
 119static inline int shmem_getpage(struct inode *inode, pgoff_t index,
 120        struct page **pagep, enum sgp_type sgp, int *fault_type)
 121{
 122        return shmem_getpage_gfp(inode, index, pagep, sgp,
 123                        mapping_gfp_mask(inode->i_mapping), fault_type);
 124}
 125
 126static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
 127{
 128        return sb->s_fs_info;
 129}
 130
 131/*
 132 * shmem_file_setup pre-accounts the whole fixed size of a VM object,
 133 * for shared memory and for shared anonymous (/dev/zero) mappings
 134 * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
 135 * consistent with the pre-accounting of private mappings ...
 136 */
 137static inline int shmem_acct_size(unsigned long flags, loff_t size)
 138{
 139        return (flags & VM_NORESERVE) ?
 140                0 : security_vm_enough_memory_mm(current->mm, VM_ACCT(size));
 141}
 142
 143static inline void shmem_unacct_size(unsigned long flags, loff_t size)
 144{
 145        if (!(flags & VM_NORESERVE))
 146                vm_unacct_memory(VM_ACCT(size));
 147}
 148
 149/*
 150 * ... whereas tmpfs objects are accounted incrementally as
 151 * pages are allocated, in order to allow huge sparse files.
 152 * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
 153 * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
 154 */
 155static inline int shmem_acct_block(unsigned long flags)
 156{
 157        return (flags & VM_NORESERVE) ?
 158                security_vm_enough_memory_mm(current->mm, VM_ACCT(PAGE_CACHE_SIZE)) : 0;
 159}
 160
 161static inline void shmem_unacct_blocks(unsigned long flags, long pages)
 162{
 163        if (flags & VM_NORESERVE)
 164                vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
 165}
 166
 167static const struct super_operations shmem_ops;
 168static const struct address_space_operations shmem_aops;
 169static const struct file_operations shmem_file_operations;
 170static const struct inode_operations shmem_inode_operations;
 171static const struct inode_operations shmem_dir_inode_operations;
 172static const struct inode_operations shmem_special_inode_operations;
 173static const struct vm_operations_struct shmem_vm_ops;
 174
 175static struct backing_dev_info shmem_backing_dev_info  __read_mostly = {
 176        .ra_pages       = 0,    /* No readahead */
 177        .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
 178};
 179
 180static LIST_HEAD(shmem_swaplist);
 181static DEFINE_MUTEX(shmem_swaplist_mutex);
 182
 183static int shmem_reserve_inode(struct super_block *sb)
 184{
 185        struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
 186        if (sbinfo->max_inodes) {
 187                spin_lock(&sbinfo->stat_lock);
 188                if (!sbinfo->free_inodes) {
 189                        spin_unlock(&sbinfo->stat_lock);
 190                        return -ENOSPC;
 191                }
 192                sbinfo->free_inodes--;
 193                spin_unlock(&sbinfo->stat_lock);
 194        }
 195        return 0;
 196}
 197
 198static void shmem_free_inode(struct super_block *sb)
 199{
 200        struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
 201        if (sbinfo->max_inodes) {
 202                spin_lock(&sbinfo->stat_lock);
 203                sbinfo->free_inodes++;
 204                spin_unlock(&sbinfo->stat_lock);
 205        }
 206}
 207
 208/**
 209 * shmem_recalc_inode - recalculate the block usage of an inode
 210 * @inode: inode to recalc
 211 *
 212 * We have to calculate the free blocks since the mm can drop
 213 * undirtied hole pages behind our back.
 214 *
 215 * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
 216 * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
 217 *
 218 * It has to be called with the spinlock held.
 219 */
 220static void shmem_recalc_inode(struct inode *inode)
 221{
 222        struct shmem_inode_info *info = SHMEM_I(inode);
 223        long freed;
 224
 225        freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
 226        if (freed > 0) {
 227                struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 228                if (sbinfo->max_blocks)
 229                        percpu_counter_add(&sbinfo->used_blocks, -freed);
 230                info->alloced -= freed;
 231                inode->i_blocks -= freed * BLOCKS_PER_PAGE;
 232                shmem_unacct_blocks(info->flags, freed);
 233        }
 234}
 235
 236/*
 237 * Replace item expected in radix tree by a new item, while holding tree lock.
 238 */
 239static int shmem_radix_tree_replace(struct address_space *mapping,
 240                        pgoff_t index, void *expected, void *replacement)
 241{
 242        void **pslot;
 243        void *item = NULL;
 244
 245        VM_BUG_ON(!expected);
 246        pslot = radix_tree_lookup_slot(&mapping->page_tree, index);
 247        if (pslot)
 248                item = radix_tree_deref_slot_protected(pslot,
 249                                                        &mapping->tree_lock);
 250        if (item != expected)
 251                return -ENOENT;
 252        if (replacement)
 253                radix_tree_replace_slot(pslot, replacement);
 254        else
 255                radix_tree_delete(&mapping->page_tree, index);
 256        return 0;
 257}
 258
 259/*
 260 * Sometimes, before we decide whether to proceed or to fail, we must check
 261 * that an entry was not already brought back from swap by a racing thread.
 262 *
 263 * Checking page is not enough: by the time a SwapCache page is locked, it
 264 * might be reused, and again be SwapCache, using the same swap as before.
 265 */
 266static bool shmem_confirm_swap(struct address_space *mapping,
 267                               pgoff_t index, swp_entry_t swap)
 268{
 269        void *item;
 270
 271        rcu_read_lock();
 272        item = radix_tree_lookup(&mapping->page_tree, index);
 273        rcu_read_unlock();
 274        return item == swp_to_radix_entry(swap);
 275}
 276
 277/*
 278 * Like add_to_page_cache_locked, but error if expected item has gone.
 279 */
 280static int shmem_add_to_page_cache(struct page *page,
 281                                   struct address_space *mapping,
 282                                   pgoff_t index, gfp_t gfp, void *expected)
 283{
 284        int error;
 285
 286        VM_BUG_ON(!PageLocked(page));
 287        VM_BUG_ON(!PageSwapBacked(page));
 288
 289        page_cache_get(page);
 290        page->mapping = mapping;
 291        page->index = index;
 292
 293        spin_lock_irq(&mapping->tree_lock);
 294        if (!expected)
 295                error = radix_tree_insert(&mapping->page_tree, index, page);
 296        else
 297                error = shmem_radix_tree_replace(mapping, index, expected,
 298                                                                 page);
 299        if (!error) {
 300                mapping->nrpages++;
 301                __inc_zone_page_state(page, NR_FILE_PAGES);
 302                __inc_zone_page_state(page, NR_SHMEM);
 303                spin_unlock_irq(&mapping->tree_lock);
 304        } else {
 305                page->mapping = NULL;
 306                spin_unlock_irq(&mapping->tree_lock);
 307                page_cache_release(page);
 308        }
 309        return error;
 310}
 311
 312/*
 313 * Like delete_from_page_cache, but substitutes swap for page.
 314 */
 315static void shmem_delete_from_page_cache(struct page *page, void *radswap)
 316{
 317        struct address_space *mapping = page->mapping;
 318        int error;
 319
 320        spin_lock_irq(&mapping->tree_lock);
 321        error = shmem_radix_tree_replace(mapping, page->index, page, radswap);
 322        page->mapping = NULL;
 323        mapping->nrpages--;
 324        __dec_zone_page_state(page, NR_FILE_PAGES);
 325        __dec_zone_page_state(page, NR_SHMEM);
 326        spin_unlock_irq(&mapping->tree_lock);
 327        page_cache_release(page);
 328        BUG_ON(error);
 329}
 330
 331/*
 332 * Like find_get_pages, but collecting swap entries as well as pages.
 333 */
 334static unsigned shmem_find_get_pages_and_swap(struct address_space *mapping,
 335                                        pgoff_t start, unsigned int nr_pages,
 336                                        struct page **pages, pgoff_t *indices)
 337{
 338        unsigned int i;
 339        unsigned int ret;
 340        unsigned int nr_found;
 341
 342        rcu_read_lock();
 343restart:
 344        nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
 345                                (void ***)pages, indices, start, nr_pages);
 346        ret = 0;
 347        for (i = 0; i < nr_found; i++) {
 348                struct page *page;
 349repeat:
 350                page = radix_tree_deref_slot((void **)pages[i]);
 351                if (unlikely(!page))
 352                        continue;
 353                if (radix_tree_exception(page)) {
 354                        if (radix_tree_deref_retry(page))
 355                                goto restart;
 356                        /*
 357                         * Otherwise, we must be storing a swap entry
 358                         * here as an exceptional entry: so return it
 359                         * without attempting to raise page count.
 360                         */
 361                        goto export;
 362                }
 363                if (!page_cache_get_speculative(page))
 364                        goto repeat;
 365
 366                /* Has the page moved? */
 367                if (unlikely(page != *((void **)pages[i]))) {
 368                        page_cache_release(page);
 369                        goto repeat;
 370                }
 371export:
 372                indices[ret] = indices[i];
 373                pages[ret] = page;
 374                ret++;
 375        }
 376        if (unlikely(!ret && nr_found))
 377                goto restart;
 378        rcu_read_unlock();
 379        return ret;
 380}
 381
 382/*
 383 * Remove swap entry from radix tree, free the swap and its page cache.
 384 */
 385static int shmem_free_swap(struct address_space *mapping,
 386                           pgoff_t index, void *radswap)
 387{
 388        int error;
 389
 390        spin_lock_irq(&mapping->tree_lock);
 391        error = shmem_radix_tree_replace(mapping, index, radswap, NULL);
 392        spin_unlock_irq(&mapping->tree_lock);
 393        if (!error)
 394                free_swap_and_cache(radix_to_swp_entry(radswap));
 395        return error;
 396}
 397
 398/*
 399 * Pagevec may contain swap entries, so shuffle up pages before releasing.
 400 */
 401static void shmem_deswap_pagevec(struct pagevec *pvec)
 402{
 403        int i, j;
 404
 405        for (i = 0, j = 0; i < pagevec_count(pvec); i++) {
 406                struct page *page = pvec->pages[i];
 407                if (!radix_tree_exceptional_entry(page))
 408                        pvec->pages[j++] = page;
 409        }
 410        pvec->nr = j;
 411}
 412
 413/*
 414 * SysV IPC SHM_UNLOCK restore Unevictable pages to their evictable lists.
 415 */
 416void shmem_unlock_mapping(struct address_space *mapping)
 417{
 418        struct pagevec pvec;
 419        pgoff_t indices[PAGEVEC_SIZE];
 420        pgoff_t index = 0;
 421
 422        pagevec_init(&pvec, 0);
 423        /*
 424         * Minor point, but we might as well stop if someone else SHM_LOCKs it.
 425         */
 426        while (!mapping_unevictable(mapping)) {
 427                /*
 428                 * Avoid pagevec_lookup(): find_get_pages() returns 0 as if it
 429                 * has finished, if it hits a row of PAGEVEC_SIZE swap entries.
 430                 */
 431                pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
 432                                        PAGEVEC_SIZE, pvec.pages, indices);
 433                if (!pvec.nr)
 434                        break;
 435                index = indices[pvec.nr - 1] + 1;
 436                shmem_deswap_pagevec(&pvec);
 437                check_move_unevictable_pages(pvec.pages, pvec.nr);
 438                pagevec_release(&pvec);
 439                cond_resched();
 440        }
 441}
 442
 443/*
 444 * Remove range of pages and swap entries from radix tree, and free them.
 445 * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate.
 446 */
 447static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
 448                                                                 bool unfalloc)
 449{
 450        struct address_space *mapping = inode->i_mapping;
 451        struct shmem_inode_info *info = SHMEM_I(inode);
 452        pgoff_t start = (lstart + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 453        pgoff_t end = (lend + 1) >> PAGE_CACHE_SHIFT;
 454        unsigned int partial_start = lstart & (PAGE_CACHE_SIZE - 1);
 455        unsigned int partial_end = (lend + 1) & (PAGE_CACHE_SIZE - 1);
 456        struct pagevec pvec;
 457        pgoff_t indices[PAGEVEC_SIZE];
 458        long nr_swaps_freed = 0;
 459        pgoff_t index;
 460        int i;
 461
 462        if (lend == -1)
 463                end = -1;       /* unsigned, so actually very big */
 464
 465        pagevec_init(&pvec, 0);
 466        index = start;
 467        while (index < end) {
 468                pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
 469                                min(end - index, (pgoff_t)PAGEVEC_SIZE),
 470                                                        pvec.pages, indices);
 471                if (!pvec.nr)
 472                        break;
 473                mem_cgroup_uncharge_start();
 474                for (i = 0; i < pagevec_count(&pvec); i++) {
 475                        struct page *page = pvec.pages[i];
 476
 477                        index = indices[i];
 478                        if (index >= end)
 479                                break;
 480
 481                        if (radix_tree_exceptional_entry(page)) {
 482                                if (unfalloc)
 483                                        continue;
 484                                nr_swaps_freed += !shmem_free_swap(mapping,
 485                                                                index, page);
 486                                continue;
 487                        }
 488
 489                        if (!trylock_page(page))
 490                                continue;
 491                        if (!unfalloc || !PageUptodate(page)) {
 492                                if (page->mapping == mapping) {
 493                                        VM_BUG_ON(PageWriteback(page));
 494                                        truncate_inode_page(mapping, page);
 495                                }
 496                        }
 497                        unlock_page(page);
 498                }
 499                shmem_deswap_pagevec(&pvec);
 500                pagevec_release(&pvec);
 501                mem_cgroup_uncharge_end();
 502                cond_resched();
 503                index++;
 504        }
 505
 506        if (partial_start) {
 507                struct page *page = NULL;
 508                shmem_getpage(inode, start - 1, &page, SGP_READ, NULL);
 509                if (page) {
 510                        unsigned int top = PAGE_CACHE_SIZE;
 511                        if (start > end) {
 512                                top = partial_end;
 513                                partial_end = 0;
 514                        }
 515                        zero_user_segment(page, partial_start, top);
 516                        set_page_dirty(page);
 517                        unlock_page(page);
 518                        page_cache_release(page);
 519                }
 520        }
 521        if (partial_end) {
 522                struct page *page = NULL;
 523                shmem_getpage(inode, end, &page, SGP_READ, NULL);
 524                if (page) {
 525                        zero_user_segment(page, 0, partial_end);
 526                        set_page_dirty(page);
 527                        unlock_page(page);
 528                        page_cache_release(page);
 529                }
 530        }
 531        if (start >= end)
 532                return;
 533
 534        index = start;
 535        for ( ; ; ) {
 536                cond_resched();
 537                pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
 538                                min(end - index, (pgoff_t)PAGEVEC_SIZE),
 539                                                        pvec.pages, indices);
 540                if (!pvec.nr) {
 541                        if (index == start || unfalloc)
 542                                break;
 543                        index = start;
 544                        continue;
 545                }
 546                if ((index == start || unfalloc) && indices[0] >= end) {
 547                        shmem_deswap_pagevec(&pvec);
 548                        pagevec_release(&pvec);
 549                        break;
 550                }
 551                mem_cgroup_uncharge_start();
 552                for (i = 0; i < pagevec_count(&pvec); i++) {
 553                        struct page *page = pvec.pages[i];
 554
 555                        index = indices[i];
 556                        if (index >= end)
 557                                break;
 558
 559                        if (radix_tree_exceptional_entry(page)) {
 560                                if (unfalloc)
 561                                        continue;
 562                                nr_swaps_freed += !shmem_free_swap(mapping,
 563                                                                index, page);
 564                                continue;
 565                        }
 566
 567                        lock_page(page);
 568                        if (!unfalloc || !PageUptodate(page)) {
 569                                if (page->mapping == mapping) {
 570                                        VM_BUG_ON(PageWriteback(page));
 571                                        truncate_inode_page(mapping, page);
 572                                }
 573                        }
 574                        unlock_page(page);
 575                }
 576                shmem_deswap_pagevec(&pvec);
 577                pagevec_release(&pvec);
 578                mem_cgroup_uncharge_end();
 579                index++;
 580        }
 581
 582        spin_lock(&info->lock);
 583        info->swapped -= nr_swaps_freed;
 584        shmem_recalc_inode(inode);
 585        spin_unlock(&info->lock);
 586}
 587
 588void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
 589{
 590        shmem_undo_range(inode, lstart, lend, false);
 591        inode->i_ctime = inode->i_mtime = CURRENT_TIME;
 592}
 593EXPORT_SYMBOL_GPL(shmem_truncate_range);
 594
 595static int shmem_setattr(struct dentry *dentry, struct iattr *attr)
 596{
 597        struct inode *inode = dentry->d_inode;
 598        int error;
 599
 600        error = inode_change_ok(inode, attr);
 601        if (error)
 602                return error;
 603
 604        if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
 605                loff_t oldsize = inode->i_size;
 606                loff_t newsize = attr->ia_size;
 607
 608                if (newsize != oldsize) {
 609                        i_size_write(inode, newsize);
 610                        inode->i_ctime = inode->i_mtime = CURRENT_TIME;
 611                }
 612                if (newsize < oldsize) {
 613                        loff_t holebegin = round_up(newsize, PAGE_SIZE);
 614                        unmap_mapping_range(inode->i_mapping, holebegin, 0, 1);
 615                        shmem_truncate_range(inode, newsize, (loff_t)-1);
 616                        /* unmap again to remove racily COWed private pages */
 617                        unmap_mapping_range(inode->i_mapping, holebegin, 0, 1);
 618                }
 619        }
 620
 621        setattr_copy(inode, attr);
 622#ifdef CONFIG_TMPFS_POSIX_ACL
 623        if (attr->ia_valid & ATTR_MODE)
 624                error = generic_acl_chmod(inode);
 625#endif
 626        return error;
 627}
 628
 629static void shmem_evict_inode(struct inode *inode)
 630{
 631        struct shmem_inode_info *info = SHMEM_I(inode);
 632
 633        if (inode->i_mapping->a_ops == &shmem_aops) {
 634                shmem_unacct_size(info->flags, inode->i_size);
 635                inode->i_size = 0;
 636                shmem_truncate_range(inode, 0, (loff_t)-1);
 637                if (!list_empty(&info->swaplist)) {
 638                        mutex_lock(&shmem_swaplist_mutex);
 639                        list_del_init(&info->swaplist);
 640                        mutex_unlock(&shmem_swaplist_mutex);
 641                }
 642        } else
 643                kfree(info->symlink);
 644
 645        simple_xattrs_free(&info->xattrs);
 646        WARN_ON(inode->i_blocks);
 647        shmem_free_inode(inode->i_sb);
 648        clear_inode(inode);
 649}
 650
 651/*
 652 * If swap found in inode, free it and move page from swapcache to filecache.
 653 */
 654static int shmem_unuse_inode(struct shmem_inode_info *info,
 655                             swp_entry_t swap, struct page **pagep)
 656{
 657        struct address_space *mapping = info->vfs_inode.i_mapping;
 658        void *radswap;
 659        pgoff_t index;
 660        gfp_t gfp;
 661        int error = 0;
 662
 663        radswap = swp_to_radix_entry(swap);
 664        index = radix_tree_locate_item(&mapping->page_tree, radswap);
 665        if (index == -1)
 666                return 0;
 667
 668        /*
 669         * Move _head_ to start search for next from here.
 670         * But be careful: shmem_evict_inode checks list_empty without taking
 671         * mutex, and there's an instant in list_move_tail when info->swaplist
 672         * would appear empty, if it were the only one on shmem_swaplist.
 673         */
 674        if (shmem_swaplist.next != &info->swaplist)
 675                list_move_tail(&shmem_swaplist, &info->swaplist);
 676
 677        gfp = mapping_gfp_mask(mapping);
 678        if (shmem_should_replace_page(*pagep, gfp)) {
 679                mutex_unlock(&shmem_swaplist_mutex);
 680                error = shmem_replace_page(pagep, gfp, info, index);
 681                mutex_lock(&shmem_swaplist_mutex);
 682                /*
 683                 * We needed to drop mutex to make that restrictive page
 684                 * allocation, but the inode might have been freed while we
 685                 * dropped it: although a racing shmem_evict_inode() cannot
 686                 * complete without emptying the radix_tree, our page lock
 687                 * on this swapcache page is not enough to prevent that -
 688                 * free_swap_and_cache() of our swap entry will only
 689                 * trylock_page(), removing swap from radix_tree whatever.
 690                 *
 691                 * We must not proceed to shmem_add_to_page_cache() if the
 692                 * inode has been freed, but of course we cannot rely on
 693                 * inode or mapping or info to check that.  However, we can
 694                 * safely check if our swap entry is still in use (and here
 695                 * it can't have got reused for another page): if it's still
 696                 * in use, then the inode cannot have been freed yet, and we
 697                 * can safely proceed (if it's no longer in use, that tells
 698                 * nothing about the inode, but we don't need to unuse swap).
 699                 */
 700                if (!page_swapcount(*pagep))
 701                        error = -ENOENT;
 702        }
 703
 704        /*
 705         * We rely on shmem_swaplist_mutex, not only to protect the swaplist,
 706         * but also to hold up shmem_evict_inode(): so inode cannot be freed
 707         * beneath us (pagelock doesn't help until the page is in pagecache).
 708         */
 709        if (!error)
 710                error = shmem_add_to_page_cache(*pagep, mapping, index,
 711                                                GFP_NOWAIT, radswap);
 712        if (error != -ENOMEM) {
 713                /*
 714                 * Truncation and eviction use free_swap_and_cache(), which
 715                 * only does trylock page: if we raced, best clean up here.
 716                 */
 717                delete_from_swap_cache(*pagep);
 718                set_page_dirty(*pagep);
 719                if (!error) {
 720                        spin_lock(&info->lock);
 721                        info->swapped--;
 722                        spin_unlock(&info->lock);
 723                        swap_free(swap);
 724                }
 725                error = 1;      /* not an error, but entry was found */
 726        }
 727        return error;
 728}
 729
 730/*
 731 * Search through swapped inodes to find and replace swap by page.
 732 */
 733int shmem_unuse(swp_entry_t swap, struct page *page)
 734{
 735        struct list_head *this, *next;
 736        struct shmem_inode_info *info;
 737        int found = 0;
 738        int error = 0;
 739
 740        /*
 741         * There's a faint possibility that swap page was replaced before
 742         * caller locked it: caller will come back later with the right page.
 743         */
 744        if (unlikely(!PageSwapCache(page) || page_private(page) != swap.val))
 745                goto out;
 746
 747        /*
 748         * Charge page using GFP_KERNEL while we can wait, before taking
 749         * the shmem_swaplist_mutex which might hold up shmem_writepage().
 750         * Charged back to the user (not to caller) when swap account is used.
 751         */
 752        error = mem_cgroup_cache_charge(page, current->mm, GFP_KERNEL);
 753        if (error)
 754                goto out;
 755        /* No radix_tree_preload: swap entry keeps a place for page in tree */
 756
 757        mutex_lock(&shmem_swaplist_mutex);
 758        list_for_each_safe(this, next, &shmem_swaplist) {
 759                info = list_entry(this, struct shmem_inode_info, swaplist);
 760                if (info->swapped)
 761                        found = shmem_unuse_inode(info, swap, &page);
 762                else
 763                        list_del_init(&info->swaplist);
 764                cond_resched();
 765                if (found)
 766                        break;
 767        }
 768        mutex_unlock(&shmem_swaplist_mutex);
 769
 770        if (found < 0)
 771                error = found;
 772out:
 773        unlock_page(page);
 774        page_cache_release(page);
 775        return error;
 776}
 777
 778/*
 779 * Move the page from the page cache to the swap cache.
 780 */
 781static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 782{
 783        struct shmem_inode_info *info;
 784        struct address_space *mapping;
 785        struct inode *inode;
 786        swp_entry_t swap;
 787        pgoff_t index;
 788
 789        BUG_ON(!PageLocked(page));
 790        mapping = page->mapping;
 791        index = page->index;
 792        inode = mapping->host;
 793        info = SHMEM_I(inode);
 794        if (info->flags & VM_LOCKED)
 795                goto redirty;
 796        if (!total_swap_pages)
 797                goto redirty;
 798
 799        /*
 800         * shmem_backing_dev_info's capabilities prevent regular writeback or
 801         * sync from ever calling shmem_writepage; but a stacking filesystem
 802         * might use ->writepage of its underlying filesystem, in which case
 803         * tmpfs should write out to swap only in response to memory pressure,
 804         * and not for the writeback threads or sync.
 805         */
 806        if (!wbc->for_reclaim) {
 807                WARN_ON_ONCE(1);        /* Still happens? Tell us about it! */
 808                goto redirty;
 809        }
 810
 811        /*
 812         * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC
 813         * value into swapfile.c, the only way we can correctly account for a
 814         * fallocated page arriving here is now to initialize it and write it.
 815         *
 816         * That's okay for a page already fallocated earlier, but if we have
 817         * not yet completed the fallocation, then (a) we want to keep track
 818         * of this page in case we have to undo it, and (b) it may not be a
 819         * good idea to continue anyway, once we're pushing into swap.  So
 820         * reactivate the page, and let shmem_fallocate() quit when too many.
 821         */
 822        if (!PageUptodate(page)) {
 823                if (inode->i_private) {
 824                        struct shmem_falloc *shmem_falloc;
 825                        spin_lock(&inode->i_lock);
 826                        shmem_falloc = inode->i_private;
 827                        if (shmem_falloc &&
 828                            index >= shmem_falloc->start &&
 829                            index < shmem_falloc->next)
 830                                shmem_falloc->nr_unswapped++;
 831                        else
 832                                shmem_falloc = NULL;
 833                        spin_unlock(&inode->i_lock);
 834                        if (shmem_falloc)
 835                                goto redirty;
 836                }
 837                clear_highpage(page);
 838                flush_dcache_page(page);
 839                SetPageUptodate(page);
 840        }
 841
 842        swap = get_swap_page();
 843        if (!swap.val)
 844                goto redirty;
 845
 846        /*
 847         * Add inode to shmem_unuse()'s list of swapped-out inodes,
 848         * if it's not already there.  Do it now before the page is
 849         * moved to swap cache, when its pagelock no longer protects
 850         * the inode from eviction.  But don't unlock the mutex until
 851         * we've incremented swapped, because shmem_unuse_inode() will
 852         * prune a !swapped inode from the swaplist under this mutex.
 853         */
 854        mutex_lock(&shmem_swaplist_mutex);
 855        if (list_empty(&info->swaplist))
 856                list_add_tail(&info->swaplist, &shmem_swaplist);
 857
 858        if (add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
 859                swap_shmem_alloc(swap);
 860                shmem_delete_from_page_cache(page, swp_to_radix_entry(swap));
 861
 862                spin_lock(&info->lock);
 863                info->swapped++;
 864                shmem_recalc_inode(inode);
 865                spin_unlock(&info->lock);
 866
 867                mutex_unlock(&shmem_swaplist_mutex);
 868                BUG_ON(page_mapped(page));
 869                swap_writepage(page, wbc);
 870                return 0;
 871        }
 872
 873        mutex_unlock(&shmem_swaplist_mutex);
 874        swapcache_free(swap, NULL);
 875redirty:
 876        set_page_dirty(page);
 877        if (wbc->for_reclaim)
 878                return AOP_WRITEPAGE_ACTIVATE;  /* Return with page locked */
 879        unlock_page(page);
 880        return 0;
 881}
 882
 883#ifdef CONFIG_NUMA
 884#ifdef CONFIG_TMPFS
 885static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
 886{
 887        char buffer[64];
 888
 889        if (!mpol || mpol->mode == MPOL_DEFAULT)
 890                return;         /* show nothing */
 891
 892        mpol_to_str(buffer, sizeof(buffer), mpol);
 893
 894        seq_printf(seq, ",mpol=%s", buffer);
 895}
 896
 897static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
 898{
 899        struct mempolicy *mpol = NULL;
 900        if (sbinfo->mpol) {
 901                spin_lock(&sbinfo->stat_lock);  /* prevent replace/use races */
 902                mpol = sbinfo->mpol;
 903                mpol_get(mpol);
 904                spin_unlock(&sbinfo->stat_lock);
 905        }
 906        return mpol;
 907}
 908#endif /* CONFIG_TMPFS */
 909
 910static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
 911                        struct shmem_inode_info *info, pgoff_t index)
 912{
 913        struct vm_area_struct pvma;
 914        struct page *page;
 915
 916        /* Create a pseudo vma that just contains the policy */
 917        pvma.vm_start = 0;
 918        /* Bias interleave by inode number to distribute better across nodes */
 919        pvma.vm_pgoff = index + info->vfs_inode.i_ino;
 920        pvma.vm_ops = NULL;
 921        pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
 922
 923        page = swapin_readahead(swap, gfp, &pvma, 0);
 924
 925        /* Drop reference taken by mpol_shared_policy_lookup() */
 926        mpol_cond_put(pvma.vm_policy);
 927
 928        return page;
 929}
 930
 931static struct page *shmem_alloc_page(gfp_t gfp,
 932                        struct shmem_inode_info *info, pgoff_t index)
 933{
 934        struct vm_area_struct pvma;
 935        struct page *page;
 936
 937        /* Create a pseudo vma that just contains the policy */
 938        pvma.vm_start = 0;
 939        /* Bias interleave by inode number to distribute better across nodes */
 940        pvma.vm_pgoff = index + info->vfs_inode.i_ino;
 941        pvma.vm_ops = NULL;
 942        pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
 943
 944        page = alloc_page_vma(gfp, &pvma, 0);
 945
 946        /* Drop reference taken by mpol_shared_policy_lookup() */
 947        mpol_cond_put(pvma.vm_policy);
 948
 949        return page;
 950}
 951#else /* !CONFIG_NUMA */
 952#ifdef CONFIG_TMPFS
 953static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
 954{
 955}
 956#endif /* CONFIG_TMPFS */
 957
 958static inline struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
 959                        struct shmem_inode_info *info, pgoff_t index)
 960{
 961        return swapin_readahead(swap, gfp, NULL, 0);
 962}
 963
 964static inline struct page *shmem_alloc_page(gfp_t gfp,
 965                        struct shmem_inode_info *info, pgoff_t index)
 966{
 967        return alloc_page(gfp);
 968}
 969#endif /* CONFIG_NUMA */
 970
 971#if !defined(CONFIG_NUMA) || !defined(CONFIG_TMPFS)
 972static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
 973{
 974        return NULL;
 975}
 976#endif
 977
 978/*
 979 * When a page is moved from swapcache to shmem filecache (either by the
 980 * usual swapin of shmem_getpage_gfp(), or by the less common swapoff of
 981 * shmem_unuse_inode()), it may have been read in earlier from swap, in
 982 * ignorance of the mapping it belongs to.  If that mapping has special
 983 * constraints (like the gma500 GEM driver, which requires RAM below 4GB),
 984 * we may need to copy to a suitable page before moving to filecache.
 985 *
 986 * In a future release, this may well be extended to respect cpuset and
 987 * NUMA mempolicy, and applied also to anonymous pages in do_swap_page();
 988 * but for now it is a simple matter of zone.
 989 */
 990static bool shmem_should_replace_page(struct page *page, gfp_t gfp)
 991{
 992        return page_zonenum(page) > gfp_zone(gfp);
 993}
 994
 995static int shmem_replace_page(struct page **pagep, gfp_t gfp,
 996                                struct shmem_inode_info *info, pgoff_t index)
 997{
 998        struct page *oldpage, *newpage;
 999        struct address_space *swap_mapping;
1000        pgoff_t swap_index;
1001        int error;
1002
1003        oldpage = *pagep;
1004        swap_index = page_private(oldpage);
1005        swap_mapping = page_mapping(oldpage);
1006
1007        /*
1008         * We have arrived here because our zones are constrained, so don't
1009         * limit chance of success by further cpuset and node constraints.
1010         */
1011        gfp &= ~GFP_CONSTRAINT_MASK;
1012        newpage = shmem_alloc_page(gfp, info, index);
1013        if (!newpage)
1014                return -ENOMEM;
1015
1016        page_cache_get(newpage);
1017        copy_highpage(newpage, oldpage);
1018        flush_dcache_page(newpage);
1019
1020        __set_page_locked(newpage);
1021        SetPageUptodate(newpage);
1022        SetPageSwapBacked(newpage);
1023        set_page_private(newpage, swap_index);
1024        SetPageSwapCache(newpage);
1025
1026        /*
1027         * Our caller will very soon move newpage out of swapcache, but it's
1028         * a nice clean interface for us to replace oldpage by newpage there.
1029         */
1030        spin_lock_irq(&swap_mapping->tree_lock);
1031        error = shmem_radix_tree_replace(swap_mapping, swap_index, oldpage,
1032                                                                   newpage);
1033        if (!error) {
1034                __inc_zone_page_state(newpage, NR_FILE_PAGES);
1035                __dec_zone_page_state(oldpage, NR_FILE_PAGES);
1036        }
1037        spin_unlock_irq(&swap_mapping->tree_lock);
1038
1039        if (unlikely(error)) {
1040                /*
1041                 * Is this possible?  I think not, now that our callers check
1042                 * both PageSwapCache and page_private after getting page lock;
1043                 * but be defensive.  Reverse old to newpage for clear and free.
1044                 */
1045                oldpage = newpage;
1046        } else {
1047                mem_cgroup_replace_page_cache(oldpage, newpage);
1048                lru_cache_add_anon(newpage);
1049                *pagep = newpage;
1050        }
1051
1052        ClearPageSwapCache(oldpage);
1053        set_page_private(oldpage, 0);
1054
1055        unlock_page(oldpage);
1056        page_cache_release(oldpage);
1057        page_cache_release(oldpage);
1058        return error;
1059}
1060
1061/*
1062 * shmem_getpage_gfp - find page in cache, or get from swap, or allocate
1063 *
1064 * If we allocate a new one we do not mark it dirty. That's up to the
1065 * vm. If we swap it in we mark it dirty since we also free the swap
1066 * entry since a page cannot live in both the swap and page cache
1067 */
1068static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
1069        struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type)
1070{
1071        struct address_space *mapping = inode->i_mapping;
1072        struct shmem_inode_info *info;
1073        struct shmem_sb_info *sbinfo;
1074        struct page *page;
1075        swp_entry_t swap;
1076        int error;
1077        int once = 0;
1078        int alloced = 0;
1079
1080        if (index > (MAX_LFS_FILESIZE >> PAGE_CACHE_SHIFT))
1081                return -EFBIG;
1082repeat:
1083        swap.val = 0;
1084        page = find_lock_page(mapping, index);
1085        if (radix_tree_exceptional_entry(page)) {
1086                swap = radix_to_swp_entry(page);
1087                page = NULL;
1088        }
1089
1090        if (sgp != SGP_WRITE && sgp != SGP_FALLOC &&
1091            ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
1092                error = -EINVAL;
1093                goto failed;
1094        }
1095
1096        /* fallocated page? */
1097        if (page && !PageUptodate(page)) {
1098                if (sgp != SGP_READ)
1099                        goto clear;
1100                unlock_page(page);
1101                page_cache_release(page);
1102                page = NULL;
1103        }
1104        if (page || (sgp == SGP_READ && !swap.val)) {
1105                *pagep = page;
1106                return 0;
1107        }
1108
1109        /*
1110         * Fast cache lookup did not find it:
1111         * bring it back from swap or allocate.
1112         */
1113        info = SHMEM_I(inode);
1114        sbinfo = SHMEM_SB(inode->i_sb);
1115
1116        if (swap.val) {
1117                /* Look it up and read it in.. */
1118                page = lookup_swap_cache(swap);
1119                if (!page) {
1120                        /* here we actually do the io */
1121                        if (fault_type)
1122                                *fault_type |= VM_FAULT_MAJOR;
1123                        page = shmem_swapin(swap, gfp, info, index);
1124                        if (!page) {
1125                                error = -ENOMEM;
1126                                goto failed;
1127                        }
1128                }
1129
1130                /* We have to do this with page locked to prevent races */
1131                lock_page(page);
1132                if (!PageSwapCache(page) || page_private(page) != swap.val ||
1133                    !shmem_confirm_swap(mapping, index, swap)) {
1134                        error = -EEXIST;        /* try again */
1135                        goto unlock;
1136                }
1137                if (!PageUptodate(page)) {
1138                        error = -EIO;
1139                        goto failed;
1140                }
1141                wait_on_page_writeback(page);
1142
1143                if (shmem_should_replace_page(page, gfp)) {
1144                        error = shmem_replace_page(&page, gfp, info, index);
1145                        if (error)
1146                                goto failed;
1147                }
1148
1149                error = mem_cgroup_cache_charge(page, current->mm,
1150                                                gfp & GFP_RECLAIM_MASK);
1151                if (!error) {
1152                        error = shmem_add_to_page_cache(page, mapping, index,
1153                                                gfp, swp_to_radix_entry(swap));
1154                        /*
1155                         * We already confirmed swap under page lock, and make
1156                         * no memory allocation here, so usually no possibility
1157                         * of error; but free_swap_and_cache() only trylocks a
1158                         * page, so it is just possible that the entry has been
1159                         * truncated or holepunched since swap was confirmed.
1160                         * shmem_undo_range() will have done some of the
1161                         * unaccounting, now delete_from_swap_cache() will do
1162                         * the rest (including mem_cgroup_uncharge_swapcache).
1163                         * Reset swap.val? No, leave it so "failed" goes back to
1164                         * "repeat": reading a hole and writing should succeed.
1165                         */
1166                        if (error)
1167                                delete_from_swap_cache(page);
1168                }
1169                if (error)
1170                        goto failed;
1171
1172                spin_lock(&info->lock);
1173                info->swapped--;
1174                shmem_recalc_inode(inode);
1175                spin_unlock(&info->lock);
1176
1177                delete_from_swap_cache(page);
1178                set_page_dirty(page);
1179                swap_free(swap);
1180
1181        } else {
1182                if (shmem_acct_block(info->flags)) {
1183                        error = -ENOSPC;
1184                        goto failed;
1185                }
1186                if (sbinfo->max_blocks) {
1187                        if (percpu_counter_compare(&sbinfo->used_blocks,
1188                                                sbinfo->max_blocks) >= 0) {
1189                                error = -ENOSPC;
1190                                goto unacct;
1191                        }
1192                        percpu_counter_inc(&sbinfo->used_blocks);
1193                }
1194
1195                page = shmem_alloc_page(gfp, info, index);
1196                if (!page) {
1197                        error = -ENOMEM;
1198                        goto decused;
1199                }
1200
1201                SetPageSwapBacked(page);
1202                __set_page_locked(page);
1203                error = mem_cgroup_cache_charge(page, current->mm,
1204                                                gfp & GFP_RECLAIM_MASK);
1205                if (error)
1206                        goto decused;
1207                error = radix_tree_preload(gfp & GFP_RECLAIM_MASK);
1208                if (!error) {
1209                        error = shmem_add_to_page_cache(page, mapping, index,
1210                                                        gfp, NULL);
1211                        radix_tree_preload_end();
1212                }
1213                if (error) {
1214                        mem_cgroup_uncharge_cache_page(page);
1215                        goto decused;
1216                }
1217                lru_cache_add_anon(page);
1218
1219                spin_lock(&info->lock);
1220                info->alloced++;
1221                inode->i_blocks += BLOCKS_PER_PAGE;
1222                shmem_recalc_inode(inode);
1223                spin_unlock(&info->lock);
1224                alloced = true;
1225
1226                /*
1227                 * Let SGP_FALLOC use the SGP_WRITE optimization on a new page.
1228                 */
1229                if (sgp == SGP_FALLOC)
1230                        sgp = SGP_WRITE;
1231clear:
1232                /*
1233                 * Let SGP_WRITE caller clear ends if write does not fill page;
1234                 * but SGP_FALLOC on a page fallocated earlier must initialize
1235                 * it now, lest undo on failure cancel our earlier guarantee.
1236                 */
1237                if (sgp != SGP_WRITE) {
1238                        clear_highpage(page);
1239                        flush_dcache_page(page);
1240                        SetPageUptodate(page);
1241                }
1242                if (sgp == SGP_DIRTY)
1243                        set_page_dirty(page);
1244        }
1245
1246        /* Perhaps the file has been truncated since we checked */
1247        if (sgp != SGP_WRITE && sgp != SGP_FALLOC &&
1248            ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
1249                error = -EINVAL;
1250                if (alloced)
1251                        goto trunc;
1252                else
1253                        goto failed;
1254        }
1255        *pagep = page;
1256        return 0;
1257
1258        /*
1259         * Error recovery.
1260         */
1261trunc:
1262        info = SHMEM_I(inode);
1263        ClearPageDirty(page);
1264        delete_from_page_cache(page);
1265        spin_lock(&info->lock);
1266        info->alloced--;
1267        inode->i_blocks -= BLOCKS_PER_PAGE;
1268        spin_unlock(&info->lock);
1269decused:
1270        sbinfo = SHMEM_SB(inode->i_sb);
1271        if (sbinfo->max_blocks)
1272                percpu_counter_add(&sbinfo->used_blocks, -1);
1273unacct:
1274        shmem_unacct_blocks(info->flags, 1);
1275failed:
1276        if (swap.val && error != -EINVAL &&
1277            !shmem_confirm_swap(mapping, index, swap))
1278                error = -EEXIST;
1279unlock:
1280        if (page) {
1281                unlock_page(page);
1282                page_cache_release(page);
1283        }
1284        if (error == -ENOSPC && !once++) {
1285                info = SHMEM_I(inode);
1286                spin_lock(&info->lock);
1287                shmem_recalc_inode(inode);
1288                spin_unlock(&info->lock);
1289                goto repeat;
1290        }
1291        if (error == -EEXIST)   /* from above or from radix_tree_insert */
1292                goto repeat;
1293        return error;
1294}
1295
1296static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1297{
1298        struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1299        int error;
1300        int ret = VM_FAULT_LOCKED;
1301
1302        error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret);
1303        if (error)
1304                return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1305
1306        if (ret & VM_FAULT_MAJOR) {
1307                count_vm_event(PGMAJFAULT);
1308                mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1309        }
1310        return ret;
1311}
1312
1313#ifdef CONFIG_NUMA
1314static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *mpol)
1315{
1316        struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1317        return mpol_set_shared_policy(&SHMEM_I(inode)->policy, vma, mpol);
1318}
1319
1320static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
1321                                          unsigned long addr)
1322{
1323        struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1324        pgoff_t index;
1325
1326        index = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1327        return mpol_shared_policy_lookup(&SHMEM_I(inode)->policy, index);
1328}
1329#endif
1330
1331int shmem_lock(struct file *file, int lock, struct user_struct *user)
1332{
1333        struct inode *inode = file->f_path.dentry->d_inode;
1334        struct shmem_inode_info *info = SHMEM_I(inode);
1335        int retval = -ENOMEM;
1336
1337        spin_lock(&info->lock);
1338        if (lock && !(info->flags & VM_LOCKED)) {
1339                if (!user_shm_lock(inode->i_size, user))
1340                        goto out_nomem;
1341                info->flags |= VM_LOCKED;
1342                mapping_set_unevictable(file->f_mapping);
1343        }
1344        if (!lock && (info->flags & VM_LOCKED) && user) {
1345                user_shm_unlock(inode->i_size, user);
1346                info->flags &= ~VM_LOCKED;
1347                mapping_clear_unevictable(file->f_mapping);
1348        }
1349        retval = 0;
1350
1351out_nomem:
1352        spin_unlock(&info->lock);
1353        return retval;
1354}
1355
1356static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1357{
1358        file_accessed(file);
1359        vma->vm_ops = &shmem_vm_ops;
1360        return 0;
1361}
1362
1363static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir,
1364                                     umode_t mode, dev_t dev, unsigned long flags)
1365{
1366        struct inode *inode;
1367        struct shmem_inode_info *info;
1368        struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1369
1370        if (shmem_reserve_inode(sb))
1371                return NULL;
1372
1373        inode = new_inode(sb);
1374        if (inode) {
1375                inode->i_ino = get_next_ino();
1376                inode_init_owner(inode, dir, mode);
1377                inode->i_blocks = 0;
1378                inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1379                inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1380                inode->i_generation = get_seconds();
1381                info = SHMEM_I(inode);
1382                memset(info, 0, (char *)inode - (char *)info);
1383                spin_lock_init(&info->lock);
1384                info->flags = flags & VM_NORESERVE;
1385                INIT_LIST_HEAD(&info->swaplist);
1386                simple_xattrs_init(&info->xattrs);
1387                cache_no_acl(inode);
1388
1389                switch (mode & S_IFMT) {
1390                default:
1391                        inode->i_op = &shmem_special_inode_operations;
1392                        init_special_inode(inode, mode, dev);
1393                        break;
1394                case S_IFREG:
1395                        inode->i_mapping->a_ops = &shmem_aops;
1396                        inode->i_op = &shmem_inode_operations;
1397                        inode->i_fop = &shmem_file_operations;
1398                        mpol_shared_policy_init(&info->policy,
1399                                                 shmem_get_sbmpol(sbinfo));
1400                        break;
1401                case S_IFDIR:
1402                        inc_nlink(inode);
1403                        /* Some things misbehave if size == 0 on a directory */
1404                        inode->i_size = 2 * BOGO_DIRENT_SIZE;
1405                        inode->i_op = &shmem_dir_inode_operations;
1406                        inode->i_fop = &simple_dir_operations;
1407                        break;
1408                case S_IFLNK:
1409                        /*
1410                         * Must not load anything in the rbtree,
1411                         * mpol_free_shared_policy will not be called.
1412                         */
1413                        mpol_shared_policy_init(&info->policy, NULL);
1414                        break;
1415                }
1416        } else
1417                shmem_free_inode(sb);
1418        return inode;
1419}
1420
1421#ifdef CONFIG_TMPFS
1422static const struct inode_operations shmem_symlink_inode_operations;
1423static const struct inode_operations shmem_short_symlink_operations;
1424
1425#ifdef CONFIG_TMPFS_XATTR
1426static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
1427#else
1428#define shmem_initxattrs NULL
1429#endif
1430
1431static int
1432shmem_write_begin(struct file *file, struct address_space *mapping,
1433                        loff_t pos, unsigned len, unsigned flags,
1434                        struct page **pagep, void **fsdata)
1435{
1436        struct inode *inode = mapping->host;
1437        pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1438        return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
1439}
1440
1441static int
1442shmem_write_end(struct file *file, struct address_space *mapping,
1443                        loff_t pos, unsigned len, unsigned copied,
1444                        struct page *page, void *fsdata)
1445{
1446        struct inode *inode = mapping->host;
1447
1448        if (pos + copied > inode->i_size)
1449                i_size_write(inode, pos + copied);
1450
1451        if (!PageUptodate(page)) {
1452                if (copied < PAGE_CACHE_SIZE) {
1453                        unsigned from = pos & (PAGE_CACHE_SIZE - 1);
1454                        zero_user_segments(page, 0, from,
1455                                        from + copied, PAGE_CACHE_SIZE);
1456                }
1457                SetPageUptodate(page);
1458        }
1459        set_page_dirty(page);
1460        unlock_page(page);
1461        page_cache_release(page);
1462
1463        return copied;
1464}
1465
1466static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
1467{
1468        struct inode *inode = filp->f_path.dentry->d_inode;
1469        struct address_space *mapping = inode->i_mapping;
1470        pgoff_t index;
1471        unsigned long offset;
1472        enum sgp_type sgp = SGP_READ;
1473
1474        /*
1475         * Might this read be for a stacking filesystem?  Then when reading
1476         * holes of a sparse file, we actually need to allocate those pages,
1477         * and even mark them dirty, so it cannot exceed the max_blocks limit.
1478         */
1479        if (segment_eq(get_fs(), KERNEL_DS))
1480                sgp = SGP_DIRTY;
1481
1482        index = *ppos >> PAGE_CACHE_SHIFT;
1483        offset = *ppos & ~PAGE_CACHE_MASK;
1484
1485        for (;;) {
1486                struct page *page = NULL;
1487                pgoff_t end_index;
1488                unsigned long nr, ret;
1489                loff_t i_size = i_size_read(inode);
1490
1491                end_index = i_size >> PAGE_CACHE_SHIFT;
1492                if (index > end_index)
1493                        break;
1494                if (index == end_index) {
1495                        nr = i_size & ~PAGE_CACHE_MASK;
1496                        if (nr <= offset)
1497                                break;
1498                }
1499
1500                desc->error = shmem_getpage(inode, index, &page, sgp, NULL);
1501                if (desc->error) {
1502                        if (desc->error == -EINVAL)
1503                                desc->error = 0;
1504                        break;
1505                }
1506                if (page)
1507                        unlock_page(page);
1508
1509                /*
1510                 * We must evaluate after, since reads (unlike writes)
1511                 * are called without i_mutex protection against truncate
1512                 */
1513                nr = PAGE_CACHE_SIZE;
1514                i_size = i_size_read(inode);
1515                end_index = i_size >> PAGE_CACHE_SHIFT;
1516                if (index == end_index) {
1517                        nr = i_size & ~PAGE_CACHE_MASK;
1518                        if (nr <= offset) {
1519                                if (page)
1520                                        page_cache_release(page);
1521                                break;
1522                        }
1523                }
1524                nr -= offset;
1525
1526                if (page) {
1527                        /*
1528                         * If users can be writing to this page using arbitrary
1529                         * virtual addresses, take care about potential aliasing
1530                         * before reading the page on the kernel side.
1531                         */
1532                        if (mapping_writably_mapped(mapping))
1533                                flush_dcache_page(page);
1534                        /*
1535                         * Mark the page accessed if we read the beginning.
1536                         */
1537                        if (!offset)
1538                                mark_page_accessed(page);
1539                } else {
1540                        page = ZERO_PAGE(0);
1541                        page_cache_get(page);
1542                }
1543
1544                /*
1545                 * Ok, we have the page, and it's up-to-date, so
1546                 * now we can copy it to user space...
1547                 *
1548                 * The actor routine returns how many bytes were actually used..
1549                 * NOTE! This may not be the same as how much of a user buffer
1550                 * we filled up (we may be padding etc), so we can only update
1551                 * "pos" here (the actor routine has to update the user buffer
1552                 * pointers and the remaining count).
1553                 */
1554                ret = actor(desc, page, offset, nr);
1555                offset += ret;
1556                index += offset >> PAGE_CACHE_SHIFT;
1557                offset &= ~PAGE_CACHE_MASK;
1558
1559                page_cache_release(page);
1560                if (ret != nr || !desc->count)
1561                        break;
1562
1563                cond_resched();
1564        }
1565
1566        *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1567        file_accessed(filp);
1568}
1569
1570static ssize_t shmem_file_aio_read(struct kiocb *iocb,
1571                const struct iovec *iov, unsigned long nr_segs, loff_t pos)
1572{
1573        struct file *filp = iocb->ki_filp;
1574        ssize_t retval;
1575        unsigned long seg;
1576        size_t count;
1577        loff_t *ppos = &iocb->ki_pos;
1578
1579        retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1580        if (retval)
1581                return retval;
1582
1583        for (seg = 0; seg < nr_segs; seg++) {
1584                read_descriptor_t desc;
1585
1586                desc.written = 0;
1587                desc.arg.buf = iov[seg].iov_base;
1588                desc.count = iov[seg].iov_len;
1589                if (desc.count == 0)
1590                        continue;
1591                desc.error = 0;
1592                do_shmem_file_read(filp, ppos, &desc, file_read_actor);
1593                retval += desc.written;
1594                if (desc.error) {
1595                        retval = retval ?: desc.error;
1596                        break;
1597                }
1598                if (desc.count > 0)
1599                        break;
1600        }
1601        return retval;
1602}
1603
1604static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
1605                                struct pipe_inode_info *pipe, size_t len,
1606                                unsigned int flags)
1607{
1608        struct address_space *mapping = in->f_mapping;
1609        struct inode *inode = mapping->host;
1610        unsigned int loff, nr_pages, req_pages;
1611        struct page *pages[PIPE_DEF_BUFFERS];
1612        struct partial_page partial[PIPE_DEF_BUFFERS];
1613        struct page *page;
1614        pgoff_t index, end_index;
1615        loff_t isize, left;
1616        int error, page_nr;
1617        struct splice_pipe_desc spd = {
1618                .pages = pages,
1619                .partial = partial,
1620                .nr_pages_max = PIPE_DEF_BUFFERS,
1621                .flags = flags,
1622                .ops = &page_cache_pipe_buf_ops,
1623                .spd_release = spd_release_page,
1624        };
1625
1626        isize = i_size_read(inode);
1627        if (unlikely(*ppos >= isize))
1628                return 0;
1629
1630        left = isize - *ppos;
1631        if (unlikely(left < len))
1632                len = left;
1633
1634        if (splice_grow_spd(pipe, &spd))
1635                return -ENOMEM;
1636
1637        index = *ppos >> PAGE_CACHE_SHIFT;
1638        loff = *ppos & ~PAGE_CACHE_MASK;
1639        req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1640        nr_pages = min(req_pages, pipe->buffers);
1641
1642        spd.nr_pages = find_get_pages_contig(mapping, index,
1643                                                nr_pages, spd.pages);
1644        index += spd.nr_pages;
1645        error = 0;
1646
1647        while (spd.nr_pages < nr_pages) {
1648                error = shmem_getpage(inode, index, &page, SGP_CACHE, NULL);
1649                if (error)
1650                        break;
1651                unlock_page(page);
1652                spd.pages[spd.nr_pages++] = page;
1653                index++;
1654        }
1655
1656        index = *ppos >> PAGE_CACHE_SHIFT;
1657        nr_pages = spd.nr_pages;
1658        spd.nr_pages = 0;
1659
1660        for (page_nr = 0; page_nr < nr_pages; page_nr++) {
1661                unsigned int this_len;
1662
1663                if (!len)
1664                        break;
1665
1666                this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
1667                page = spd.pages[page_nr];
1668
1669                if (!PageUptodate(page) || page->mapping != mapping) {
1670                        error = shmem_getpage(inode, index, &page,
1671                                                        SGP_CACHE, NULL);
1672                        if (error)
1673                                break;
1674                        unlock_page(page);
1675                        page_cache_release(spd.pages[page_nr]);
1676                        spd.pages[page_nr] = page;
1677                }
1678
1679                isize = i_size_read(inode);
1680                end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1681                if (unlikely(!isize || index > end_index))
1682                        break;
1683
1684                if (end_index == index) {
1685                        unsigned int plen;
1686
1687                        plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1688                        if (plen <= loff)
1689                                break;
1690
1691                        this_len = min(this_len, plen - loff);
1692                        len = this_len;
1693                }
1694
1695                spd.partial[page_nr].offset = loff;
1696                spd.partial[page_nr].len = this_len;
1697                len -= this_len;
1698                loff = 0;
1699                spd.nr_pages++;
1700                index++;
1701        }
1702
1703        while (page_nr < nr_pages)
1704                page_cache_release(spd.pages[page_nr++]);
1705
1706        if (spd.nr_pages)
1707                error = splice_to_pipe(pipe, &spd);
1708
1709        splice_shrink_spd(&spd);
1710
1711        if (error > 0) {
1712                *ppos += error;
1713                file_accessed(in);
1714        }
1715        return error;
1716}
1717
1718/*
1719 * llseek SEEK_DATA or SEEK_HOLE through the radix_tree.
1720 */
1721static pgoff_t shmem_seek_hole_data(struct address_space *mapping,
1722                                    pgoff_t index, pgoff_t end, int whence)
1723{
1724        struct page *page;
1725        struct pagevec pvec;
1726        pgoff_t indices[PAGEVEC_SIZE];
1727        bool done = false;
1728        int i;
1729
1730        pagevec_init(&pvec, 0);
1731        pvec.nr = 1;            /* start small: we may be there already */
1732        while (!done) {
1733                pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
1734                                        pvec.nr, pvec.pages, indices);
1735                if (!pvec.nr) {
1736                        if (whence == SEEK_DATA)
1737                                index = end;
1738                        break;
1739                }
1740                for (i = 0; i < pvec.nr; i++, index++) {
1741                        if (index < indices[i]) {
1742                                if (whence == SEEK_HOLE) {
1743                                        done = true;
1744                                        break;
1745                                }
1746                                index = indices[i];
1747                        }
1748                        page = pvec.pages[i];
1749                        if (page && !radix_tree_exceptional_entry(page)) {
1750                                if (!PageUptodate(page))
1751                                        page = NULL;
1752                        }
1753                        if (index >= end ||
1754                            (page && whence == SEEK_DATA) ||
1755                            (!page && whence == SEEK_HOLE)) {
1756                                done = true;
1757                                break;
1758                        }
1759                }
1760                shmem_deswap_pagevec(&pvec);
1761                pagevec_release(&pvec);
1762                pvec.nr = PAGEVEC_SIZE;
1763                cond_resched();
1764        }
1765        return index;
1766}
1767
1768static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence)
1769{
1770        struct address_space *mapping = file->f_mapping;
1771        struct inode *inode = mapping->host;
1772        pgoff_t start, end;
1773        loff_t new_offset;
1774
1775        if (whence != SEEK_DATA && whence != SEEK_HOLE)
1776                return generic_file_llseek_size(file, offset, whence,
1777                                        MAX_LFS_FILESIZE, i_size_read(inode));
1778        mutex_lock(&inode->i_mutex);
1779        /* We're holding i_mutex so we can access i_size directly */
1780
1781        if (offset < 0)
1782                offset = -EINVAL;
1783        else if (offset >= inode->i_size)
1784                offset = -ENXIO;
1785        else {
1786                start = offset >> PAGE_CACHE_SHIFT;
1787                end = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1788                new_offset = shmem_seek_hole_data(mapping, start, end, whence);
1789                new_offset <<= PAGE_CACHE_SHIFT;
1790                if (new_offset > offset) {
1791                        if (new_offset < inode->i_size)
1792                                offset = new_offset;
1793                        else if (whence == SEEK_DATA)
1794                                offset = -ENXIO;
1795                        else
1796                                offset = inode->i_size;
1797                }
1798        }
1799
1800        if (offset >= 0 && offset != file->f_pos) {
1801                file->f_pos = offset;
1802                file->f_version = 0;
1803        }
1804        mutex_unlock(&inode->i_mutex);
1805        return offset;
1806}
1807
1808static long shmem_fallocate(struct file *file, int mode, loff_t offset,
1809                                                         loff_t len)
1810{
1811        struct inode *inode = file->f_path.dentry->d_inode;
1812        struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1813        struct shmem_falloc shmem_falloc;
1814        pgoff_t start, index, end;
1815        int error;
1816
1817        mutex_lock(&inode->i_mutex);
1818
1819        if (mode & FALLOC_FL_PUNCH_HOLE) {
1820                struct address_space *mapping = file->f_mapping;
1821                loff_t unmap_start = round_up(offset, PAGE_SIZE);
1822                loff_t unmap_end = round_down(offset + len, PAGE_SIZE) - 1;
1823
1824                if ((u64)unmap_end > (u64)unmap_start)
1825                        unmap_mapping_range(mapping, unmap_start,
1826                                            1 + unmap_end - unmap_start, 0);
1827                shmem_truncate_range(inode, offset, offset + len - 1);
1828                /* No need to unmap again: hole-punching leaves COWed pages */
1829                error = 0;
1830                goto out;
1831        }
1832
1833        /* We need to check rlimit even when FALLOC_FL_KEEP_SIZE */
1834        error = inode_newsize_ok(inode, offset + len);
1835        if (error)
1836                goto out;
1837
1838        start = offset >> PAGE_CACHE_SHIFT;
1839        end = (offset + len + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1840        /* Try to avoid a swapstorm if len is impossible to satisfy */
1841        if (sbinfo->max_blocks && end - start > sbinfo->max_blocks) {
1842                error = -ENOSPC;
1843                goto out;
1844        }
1845
1846        shmem_falloc.start = start;
1847        shmem_falloc.next  = start;
1848        shmem_falloc.nr_falloced = 0;
1849        shmem_falloc.nr_unswapped = 0;
1850        spin_lock(&inode->i_lock);
1851        inode->i_private = &shmem_falloc;
1852        spin_unlock(&inode->i_lock);
1853
1854        for (index = start; index < end; index++) {
1855                struct page *page;
1856
1857                /*
1858                 * Good, the fallocate(2) manpage permits EINTR: we may have
1859                 * been interrupted because we are using up too much memory.
1860                 */
1861                if (signal_pending(current))
1862                        error = -EINTR;
1863                else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
1864                        error = -ENOMEM;
1865                else
1866                        error = shmem_getpage(inode, index, &page, SGP_FALLOC,
1867                                                                        NULL);
1868                if (error) {
1869                        /* Remove the !PageUptodate pages we added */
1870                        shmem_undo_range(inode,
1871                                (loff_t)start << PAGE_CACHE_SHIFT,
1872                                (loff_t)index << PAGE_CACHE_SHIFT, true);
1873                        goto undone;
1874                }
1875
1876                /*
1877                 * Inform shmem_writepage() how far we have reached.
1878                 * No need for lock or barrier: we have the page lock.
1879                 */
1880                shmem_falloc.next++;
1881                if (!PageUptodate(page))
1882                        shmem_falloc.nr_falloced++;
1883
1884                /*
1885                 * If !PageUptodate, leave it that way so that freeable pages
1886                 * can be recognized if we need to rollback on error later.
1887                 * But set_page_dirty so that memory pressure will swap rather
1888                 * than free the pages we are allocating (and SGP_CACHE pages
1889                 * might still be clean: we now need to mark those dirty too).
1890                 */
1891                set_page_dirty(page);
1892                unlock_page(page);
1893                page_cache_release(page);
1894                cond_resched();
1895        }
1896
1897        if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
1898                i_size_write(inode, offset + len);
1899        inode->i_ctime = CURRENT_TIME;
1900undone:
1901        spin_lock(&inode->i_lock);
1902        inode->i_private = NULL;
1903        spin_unlock(&inode->i_lock);
1904out:
1905        mutex_unlock(&inode->i_mutex);
1906        return error;
1907}
1908
1909static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
1910{
1911        struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
1912
1913        buf->f_type = TMPFS_MAGIC;
1914        buf->f_bsize = PAGE_CACHE_SIZE;
1915        buf->f_namelen = NAME_MAX;
1916        if (sbinfo->max_blocks) {
1917                buf->f_blocks = sbinfo->max_blocks;
1918                buf->f_bavail =
1919                buf->f_bfree  = sbinfo->max_blocks -
1920                                percpu_counter_sum(&sbinfo->used_blocks);
1921        }
1922        if (sbinfo->max_inodes) {
1923                buf->f_files = sbinfo->max_inodes;
1924                buf->f_ffree = sbinfo->free_inodes;
1925        }
1926        /* else leave those fields 0 like simple_statfs */
1927        return 0;
1928}
1929
1930/*
1931 * File creation. Allocate an inode, and we're done..
1932 */
1933static int
1934shmem_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
1935{
1936        struct inode *inode;
1937        int error = -ENOSPC;
1938
1939        inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
1940        if (inode) {
1941                error = security_inode_init_security(inode, dir,
1942                                                     &dentry->d_name,
1943                                                     shmem_initxattrs, NULL);
1944                if (error) {
1945                        if (error != -EOPNOTSUPP) {
1946                                iput(inode);
1947                                return error;
1948                        }
1949                }
1950#ifdef CONFIG_TMPFS_POSIX_ACL
1951                error = generic_acl_init(inode, dir);
1952                if (error) {
1953                        iput(inode);
1954                        return error;
1955                }
1956#else
1957                error = 0;
1958#endif
1959                dir->i_size += BOGO_DIRENT_SIZE;
1960                dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1961                d_instantiate(dentry, inode);
1962                dget(dentry); /* Extra count - pin the dentry in core */
1963        }
1964        return error;
1965}
1966
1967static int shmem_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
1968{
1969        int error;
1970
1971        if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
1972                return error;
1973        inc_nlink(dir);
1974        return 0;
1975}
1976
1977static int shmem_create(struct inode *dir, struct dentry *dentry, umode_t mode,
1978                bool excl)
1979{
1980        return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
1981}
1982
1983/*
1984 * Link a file..
1985 */
1986static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
1987{
1988        struct inode *inode = old_dentry->d_inode;
1989        int ret;
1990
1991        /*
1992         * No ordinary (disk based) filesystem counts links as inodes;
1993         * but each new link needs a new dentry, pinning lowmem, and
1994         * tmpfs dentries cannot be pruned until they are unlinked.
1995         */
1996        ret = shmem_reserve_inode(inode->i_sb);
1997        if (ret)
1998                goto out;
1999
2000        dir->i_size += BOGO_DIRENT_SIZE;
2001        inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2002        inc_nlink(inode);
2003        ihold(inode);   /* New dentry reference */
2004        dget(dentry);           /* Extra pinning count for the created dentry */
2005        d_instantiate(dentry, inode);
2006out:
2007        return ret;
2008}
2009
2010static int shmem_unlink(struct inode *dir, struct dentry *dentry)
2011{
2012        struct inode *inode = dentry->d_inode;
2013
2014        if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
2015                shmem_free_inode(inode->i_sb);
2016
2017        dir->i_size -= BOGO_DIRENT_SIZE;
2018        inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2019        drop_nlink(inode);
2020        dput(dentry);   /* Undo the count from "create" - this does all the work */
2021        return 0;
2022}
2023
2024static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
2025{
2026        if (!simple_empty(dentry))
2027                return -ENOTEMPTY;
2028
2029        drop_nlink(dentry->d_inode);
2030        drop_nlink(dir);
2031        return shmem_unlink(dir, dentry);
2032}
2033
2034/*
2035 * The VFS layer already does all the dentry stuff for rename,
2036 * we just have to decrement the usage count for the target if
2037 * it exists so that the VFS layer correctly free's it when it
2038 * gets overwritten.
2039 */
2040static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
2041{
2042        struct inode *inode = old_dentry->d_inode;
2043        int they_are_dirs = S_ISDIR(inode->i_mode);
2044
2045        if (!simple_empty(new_dentry))
2046                return -ENOTEMPTY;
2047
2048        if (new_dentry->d_inode) {
2049                (void) shmem_unlink(new_dir, new_dentry);
2050                if (they_are_dirs)
2051                        drop_nlink(old_dir);
2052        } else if (they_are_dirs) {
2053                drop_nlink(old_dir);
2054                inc_nlink(new_dir);
2055        }
2056
2057        old_dir->i_size -= BOGO_DIRENT_SIZE;
2058        new_dir->i_size += BOGO_DIRENT_SIZE;
2059        old_dir->i_ctime = old_dir->i_mtime =
2060        new_dir->i_ctime = new_dir->i_mtime =
2061        inode->i_ctime = CURRENT_TIME;
2062        return 0;
2063}
2064
2065static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
2066{
2067        int error;
2068        int len;
2069        struct inode *inode;
2070        struct page *page;
2071        char *kaddr;
2072        struct shmem_inode_info *info;
2073
2074        len = strlen(symname) + 1;
2075        if (len > PAGE_CACHE_SIZE)
2076                return -ENAMETOOLONG;
2077
2078        inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0, VM_NORESERVE);
2079        if (!inode)
2080                return -ENOSPC;
2081
2082        error = security_inode_init_security(inode, dir, &dentry->d_name,
2083                                             shmem_initxattrs, NULL);
2084        if (error) {
2085                if (error != -EOPNOTSUPP) {
2086                        iput(inode);
2087                        return error;
2088                }
2089                error = 0;
2090        }
2091
2092        info = SHMEM_I(inode);
2093        inode->i_size = len-1;
2094        if (len <= SHORT_SYMLINK_LEN) {
2095                info->symlink = kmemdup(symname, len, GFP_KERNEL);
2096                if (!info->symlink) {
2097                        iput(inode);
2098                        return -ENOMEM;
2099                }
2100                inode->i_op = &shmem_short_symlink_operations;
2101        } else {
2102                error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
2103                if (error) {
2104                        iput(inode);
2105                        return error;
2106                }
2107                inode->i_mapping->a_ops = &shmem_aops;
2108                inode->i_op = &shmem_symlink_inode_operations;
2109                kaddr = kmap_atomic(page);
2110                memcpy(kaddr, symname, len);
2111                kunmap_atomic(kaddr);
2112                SetPageUptodate(page);
2113                set_page_dirty(page);
2114                unlock_page(page);
2115                page_cache_release(page);
2116        }
2117        dir->i_size += BOGO_DIRENT_SIZE;
2118        dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2119        d_instantiate(dentry, inode);
2120        dget(dentry);
2121        return 0;
2122}
2123
2124static void *shmem_follow_short_symlink(struct dentry *dentry, struct nameidata *nd)
2125{
2126        nd_set_link(nd, SHMEM_I(dentry->d_inode)->symlink);
2127        return NULL;
2128}
2129
2130static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
2131{
2132        struct page *page = NULL;
2133        int error = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
2134        nd_set_link(nd, error ? ERR_PTR(error) : kmap(page));
2135        if (page)
2136                unlock_page(page);
2137        return page;
2138}
2139
2140static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
2141{
2142        if (!IS_ERR(nd_get_link(nd))) {
2143                struct page *page = cookie;
2144                kunmap(page);
2145                mark_page_accessed(page);
2146                page_cache_release(page);
2147        }
2148}
2149
2150#ifdef CONFIG_TMPFS_XATTR
2151/*
2152 * Superblocks without xattr inode operations may get some security.* xattr
2153 * support from the LSM "for free". As soon as we have any other xattrs
2154 * like ACLs, we also need to implement the security.* handlers at
2155 * filesystem level, though.
2156 */
2157
2158/*
2159 * Callback for security_inode_init_security() for acquiring xattrs.
2160 */
2161static int shmem_initxattrs(struct inode *inode,
2162                            const struct xattr *xattr_array,
2163                            void *fs_info)
2164{
2165        struct shmem_inode_info *info = SHMEM_I(inode);
2166        const struct xattr *xattr;
2167        struct simple_xattr *new_xattr;
2168        size_t len;
2169
2170        for (xattr = xattr_array; xattr->name != NULL; xattr++) {
2171                new_xattr = simple_xattr_alloc(xattr->value, xattr->value_len);
2172                if (!new_xattr)
2173                        return -ENOMEM;
2174
2175                len = strlen(xattr->name) + 1;
2176                new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
2177                                          GFP_KERNEL);
2178                if (!new_xattr->name) {
2179                        kfree(new_xattr);
2180                        return -ENOMEM;
2181                }
2182
2183                memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
2184                       XATTR_SECURITY_PREFIX_LEN);
2185                memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
2186                       xattr->name, len);
2187
2188                simple_xattr_list_add(&info->xattrs, new_xattr);
2189        }
2190
2191        return 0;
2192}
2193
2194static const struct xattr_handler *shmem_xattr_handlers[] = {
2195#ifdef CONFIG_TMPFS_POSIX_ACL
2196        &generic_acl_access_handler,
2197        &generic_acl_default_handler,
2198#endif
2199        NULL
2200};
2201
2202static int shmem_xattr_validate(const char *name)
2203{
2204        struct { const char *prefix; size_t len; } arr[] = {
2205                { XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN },
2206                { XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN }
2207        };
2208        int i;
2209
2210        for (i = 0; i < ARRAY_SIZE(arr); i++) {
2211                size_t preflen = arr[i].len;
2212                if (strncmp(name, arr[i].prefix, preflen) == 0) {
2213                        if (!name[preflen])
2214                                return -EINVAL;
2215                        return 0;
2216                }
2217        }
2218        return -EOPNOTSUPP;
2219}
2220
2221static ssize_t shmem_getxattr(struct dentry *dentry, const char *name,
2222                              void *buffer, size_t size)
2223{
2224        struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2225        int err;
2226
2227        /*
2228         * If this is a request for a synthetic attribute in the system.*
2229         * namespace use the generic infrastructure to resolve a handler
2230         * for it via sb->s_xattr.
2231         */
2232        if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2233                return generic_getxattr(dentry, name, buffer, size);
2234
2235        err = shmem_xattr_validate(name);
2236        if (err)
2237                return err;
2238
2239        return simple_xattr_get(&info->xattrs, name, buffer, size);
2240}
2241
2242static int shmem_setxattr(struct dentry *dentry, const char *name,
2243                          const void *value, size_t size, int flags)
2244{
2245        struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2246        int err;
2247
2248        /*
2249         * If this is a request for a synthetic attribute in the system.*
2250         * namespace use the generic infrastructure to resolve a handler
2251         * for it via sb->s_xattr.
2252         */
2253        if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2254                return generic_setxattr(dentry, name, value, size, flags);
2255
2256        err = shmem_xattr_validate(name);
2257        if (err)
2258                return err;
2259
2260        return simple_xattr_set(&info->xattrs, name, value, size, flags);
2261}
2262
2263static int shmem_removexattr(struct dentry *dentry, const char *name)
2264{
2265        struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2266        int err;
2267
2268        /*
2269         * If this is a request for a synthetic attribute in the system.*
2270         * namespace use the generic infrastructure to resolve a handler
2271         * for it via sb->s_xattr.
2272         */
2273        if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2274                return generic_removexattr(dentry, name);
2275
2276        err = shmem_xattr_validate(name);
2277        if (err)
2278                return err;
2279
2280        return simple_xattr_remove(&info->xattrs, name);
2281}
2282
2283static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
2284{
2285        struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2286        return simple_xattr_list(&info->xattrs, buffer, size);
2287}
2288#endif /* CONFIG_TMPFS_XATTR */
2289
2290static const struct inode_operations shmem_short_symlink_operations = {
2291        .readlink       = generic_readlink,
2292        .follow_link    = shmem_follow_short_symlink,
2293#ifdef CONFIG_TMPFS_XATTR
2294        .setxattr       = shmem_setxattr,
2295        .getxattr       = shmem_getxattr,
2296        .listxattr      = shmem_listxattr,
2297        .removexattr    = shmem_removexattr,
2298#endif
2299};
2300
2301static const struct inode_operations shmem_symlink_inode_operations = {
2302        .readlink       = generic_readlink,
2303        .follow_link    = shmem_follow_link,
2304        .put_link       = shmem_put_link,
2305#ifdef CONFIG_TMPFS_XATTR
2306        .setxattr       = shmem_setxattr,
2307        .getxattr       = shmem_getxattr,
2308        .listxattr      = shmem_listxattr,
2309        .removexattr    = shmem_removexattr,
2310#endif
2311};
2312
2313static struct dentry *shmem_get_parent(struct dentry *child)
2314{
2315        return ERR_PTR(-ESTALE);
2316}
2317
2318static int shmem_match(struct inode *ino, void *vfh)
2319{
2320        __u32 *fh = vfh;
2321        __u64 inum = fh[2];
2322        inum = (inum << 32) | fh[1];
2323        return ino->i_ino == inum && fh[0] == ino->i_generation;
2324}
2325
2326static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
2327                struct fid *fid, int fh_len, int fh_type)
2328{
2329        struct inode *inode;
2330        struct dentry *dentry = NULL;
2331        u64 inum;
2332
2333        if (fh_len < 3)
2334                return NULL;
2335
2336        inum = fid->raw[2];
2337        inum = (inum << 32) | fid->raw[1];
2338
2339        inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
2340                        shmem_match, fid->raw);
2341        if (inode) {
2342                dentry = d_find_alias(inode);
2343                iput(inode);
2344        }
2345
2346        return dentry;
2347}
2348
2349static int shmem_encode_fh(struct inode *inode, __u32 *fh, int *len,
2350                                struct inode *parent)
2351{
2352        if (*len < 3) {
2353                *len = 3;
2354                return 255;
2355        }
2356
2357        if (inode_unhashed(inode)) {
2358                /* Unfortunately insert_inode_hash is not idempotent,
2359                 * so as we hash inodes here rather than at creation
2360                 * time, we need a lock to ensure we only try
2361                 * to do it once
2362                 */
2363                static DEFINE_SPINLOCK(lock);
2364                spin_lock(&lock);
2365                if (inode_unhashed(inode))
2366                        __insert_inode_hash(inode,
2367                                            inode->i_ino + inode->i_generation);
2368                spin_unlock(&lock);
2369        }
2370
2371        fh[0] = inode->i_generation;
2372        fh[1] = inode->i_ino;
2373        fh[2] = ((__u64)inode->i_ino) >> 32;
2374
2375        *len = 3;
2376        return 1;
2377}
2378
2379static const struct export_operations shmem_export_ops = {
2380        .get_parent     = shmem_get_parent,
2381        .encode_fh      = shmem_encode_fh,
2382        .fh_to_dentry   = shmem_fh_to_dentry,
2383};
2384
2385static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
2386                               bool remount)
2387{
2388        char *this_char, *value, *rest;
2389        uid_t uid;
2390        gid_t gid;
2391
2392        while (options != NULL) {
2393                this_char = options;
2394                for (;;) {
2395                        /*
2396                         * NUL-terminate this option: unfortunately,
2397                         * mount options form a comma-separated list,
2398                         * but mpol's nodelist may also contain commas.
2399                         */
2400                        options = strchr(options, ',');
2401                        if (options == NULL)
2402                                break;
2403                        options++;
2404                        if (!isdigit(*options)) {
2405                                options[-1] = '\0';
2406                                break;
2407                        }
2408                }
2409                if (!*this_char)
2410                        continue;
2411                if ((value = strchr(this_char,'=')) != NULL) {
2412                        *value++ = 0;
2413                } else {
2414                        printk(KERN_ERR
2415                            "tmpfs: No value for mount option '%s'\n",
2416                            this_char);
2417                        return 1;
2418                }
2419
2420                if (!strcmp(this_char,"size")) {
2421                        unsigned long long size;
2422                        size = memparse(value,&rest);
2423                        if (*rest == '%') {
2424                                size <<= PAGE_SHIFT;
2425                                size *= totalram_pages;
2426                                do_div(size, 100);
2427                                rest++;
2428                        }
2429                        if (*rest)
2430                                goto bad_val;
2431                        sbinfo->max_blocks =
2432                                DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
2433                } else if (!strcmp(this_char,"nr_blocks")) {
2434                        sbinfo->max_blocks = memparse(value, &rest);
2435                        if (*rest)
2436                                goto bad_val;
2437                } else if (!strcmp(this_char,"nr_inodes")) {
2438                        sbinfo->max_inodes = memparse(value, &rest);
2439                        if (*rest)
2440                                goto bad_val;
2441                } else if (!strcmp(this_char,"mode")) {
2442                        if (remount)
2443                                continue;
2444                        sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
2445                        if (*rest)
2446                                goto bad_val;
2447                } else if (!strcmp(this_char,"uid")) {
2448                        if (remount)
2449                                continue;
2450                        uid = simple_strtoul(value, &rest, 0);
2451                        if (*rest)
2452                                goto bad_val;
2453                        sbinfo->uid = make_kuid(current_user_ns(), uid);
2454                        if (!uid_valid(sbinfo->uid))
2455                                goto bad_val;
2456                } else if (!strcmp(this_char,"gid")) {
2457                        if (remount)
2458                                continue;
2459                        gid = simple_strtoul(value, &rest, 0);
2460                        if (*rest)
2461                                goto bad_val;
2462                        sbinfo->gid = make_kgid(current_user_ns(), gid);
2463                        if (!gid_valid(sbinfo->gid))
2464                                goto bad_val;
2465                } else if (!strcmp(this_char,"mpol")) {
2466                        if (mpol_parse_str(value, &sbinfo->mpol))
2467                                goto bad_val;
2468                } else {
2469                        printk(KERN_ERR "tmpfs: Bad mount option %s\n",
2470                               this_char);
2471                        return 1;
2472                }
2473        }
2474        return 0;
2475
2476bad_val:
2477        printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
2478               value, this_char);
2479        return 1;
2480
2481}
2482
2483static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2484{
2485        struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2486        struct shmem_sb_info config = *sbinfo;
2487        unsigned long inodes;
2488        int error = -EINVAL;
2489
2490        config.mpol = NULL;
2491        if (shmem_parse_options(data, &config, true))
2492                return error;
2493
2494        spin_lock(&sbinfo->stat_lock);
2495        inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2496        if (percpu_counter_compare(&sbinfo->used_blocks, config.max_blocks) > 0)
2497                goto out;
2498        if (config.max_inodes < inodes)
2499                goto out;
2500        /*
2501         * Those tests disallow limited->unlimited while any are in use;
2502         * but we must separately disallow unlimited->limited, because
2503         * in that case we have no record of how much is already in use.
2504         */
2505        if (config.max_blocks && !sbinfo->max_blocks)
2506                goto out;
2507        if (config.max_inodes && !sbinfo->max_inodes)
2508                goto out;
2509
2510        error = 0;
2511        sbinfo->max_blocks  = config.max_blocks;
2512        sbinfo->max_inodes  = config.max_inodes;
2513        sbinfo->free_inodes = config.max_inodes - inodes;
2514
2515        /*
2516         * Preserve previous mempolicy unless mpol remount option was specified.
2517         */
2518        if (config.mpol) {
2519                mpol_put(sbinfo->mpol);
2520                sbinfo->mpol = config.mpol;     /* transfers initial ref */
2521        }
2522out:
2523        spin_unlock(&sbinfo->stat_lock);
2524        return error;
2525}
2526
2527static int shmem_show_options(struct seq_file *seq, struct dentry *root)
2528{
2529        struct shmem_sb_info *sbinfo = SHMEM_SB(root->d_sb);
2530
2531        if (sbinfo->max_blocks != shmem_default_max_blocks())
2532                seq_printf(seq, ",size=%luk",
2533                        sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10));
2534        if (sbinfo->max_inodes != shmem_default_max_inodes())
2535                seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
2536        if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
2537                seq_printf(seq, ",mode=%03ho", sbinfo->mode);
2538        if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID))
2539                seq_printf(seq, ",uid=%u",
2540                                from_kuid_munged(&init_user_ns, sbinfo->uid));
2541        if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
2542                seq_printf(seq, ",gid=%u",
2543                                from_kgid_munged(&init_user_ns, sbinfo->gid));
2544        shmem_show_mpol(seq, sbinfo->mpol);
2545        return 0;
2546}
2547#endif /* CONFIG_TMPFS */
2548
2549static void shmem_put_super(struct super_block *sb)
2550{
2551        struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2552
2553        percpu_counter_destroy(&sbinfo->used_blocks);
2554        kfree(sbinfo);
2555        sb->s_fs_info = NULL;
2556}
2557
2558int shmem_fill_super(struct super_block *sb, void *data, int silent)
2559{
2560        struct inode *inode;
2561        struct shmem_sb_info *sbinfo;
2562        int err = -ENOMEM;
2563
2564        /* Round up to L1_CACHE_BYTES to resist false sharing */
2565        sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
2566                                L1_CACHE_BYTES), GFP_KERNEL);
2567        if (!sbinfo)
2568                return -ENOMEM;
2569
2570        sbinfo->mode = S_IRWXUGO | S_ISVTX;
2571        sbinfo->uid = current_fsuid();
2572        sbinfo->gid = current_fsgid();
2573        sb->s_fs_info = sbinfo;
2574
2575#ifdef CONFIG_TMPFS
2576        /*
2577         * Per default we only allow half of the physical ram per
2578         * tmpfs instance, limiting inodes to one per page of lowmem;
2579         * but the internal instance is left unlimited.
2580         */
2581        if (!(sb->s_flags & MS_NOUSER)) {
2582                sbinfo->max_blocks = shmem_default_max_blocks();
2583                sbinfo->max_inodes = shmem_default_max_inodes();
2584                if (shmem_parse_options(data, sbinfo, false)) {
2585                        err = -EINVAL;
2586                        goto failed;
2587                }
2588        }
2589        sb->s_export_op = &shmem_export_ops;
2590        sb->s_flags |= MS_NOSEC;
2591#else
2592        sb->s_flags |= MS_NOUSER;
2593#endif
2594
2595        spin_lock_init(&sbinfo->stat_lock);
2596        if (percpu_counter_init(&sbinfo->used_blocks, 0))
2597                goto failed;
2598        sbinfo->free_inodes = sbinfo->max_inodes;
2599
2600        sb->s_maxbytes = MAX_LFS_FILESIZE;
2601        sb->s_blocksize = PAGE_CACHE_SIZE;
2602        sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
2603        sb->s_magic = TMPFS_MAGIC;
2604        sb->s_op = &shmem_ops;
2605        sb->s_time_gran = 1;
2606#ifdef CONFIG_TMPFS_XATTR
2607        sb->s_xattr = shmem_xattr_handlers;
2608#endif
2609#ifdef CONFIG_TMPFS_POSIX_ACL
2610        sb->s_flags |= MS_POSIXACL;
2611#endif
2612
2613        inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
2614        if (!inode)
2615                goto failed;
2616        inode->i_uid = sbinfo->uid;
2617        inode->i_gid = sbinfo->gid;
2618        sb->s_root = d_make_root(inode);
2619        if (!sb->s_root)
2620                goto failed;
2621        return 0;
2622
2623failed:
2624        shmem_put_super(sb);
2625        return err;
2626}
2627
2628static struct kmem_cache *shmem_inode_cachep;
2629
2630static struct inode *shmem_alloc_inode(struct super_block *sb)
2631{
2632        struct shmem_inode_info *info;
2633        info = kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
2634        if (!info)
2635                return NULL;
2636        return &info->vfs_inode;
2637}
2638
2639static void shmem_destroy_callback(struct rcu_head *head)
2640{
2641        struct inode *inode = container_of(head, struct inode, i_rcu);
2642        kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2643}
2644
2645static void shmem_destroy_inode(struct inode *inode)
2646{
2647        if (S_ISREG(inode->i_mode))
2648                mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2649        call_rcu(&inode->i_rcu, shmem_destroy_callback);
2650}
2651
2652static void shmem_init_inode(void *foo)
2653{
2654        struct shmem_inode_info *info = foo;
2655        inode_init_once(&info->vfs_inode);
2656}
2657
2658static int shmem_init_inodecache(void)
2659{
2660        shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
2661                                sizeof(struct shmem_inode_info),
2662                                0, SLAB_PANIC, shmem_init_inode);
2663        return 0;
2664}
2665
2666static void shmem_destroy_inodecache(void)
2667{
2668        kmem_cache_destroy(shmem_inode_cachep);
2669}
2670
2671static const struct address_space_operations shmem_aops = {
2672        .writepage      = shmem_writepage,
2673        .set_page_dirty = __set_page_dirty_no_writeback,
2674#ifdef CONFIG_TMPFS
2675        .write_begin    = shmem_write_begin,
2676        .write_end      = shmem_write_end,
2677#endif
2678        .migratepage    = migrate_page,
2679        .error_remove_page = generic_error_remove_page,
2680};
2681
2682static const struct file_operations shmem_file_operations = {
2683        .mmap           = shmem_mmap,
2684#ifdef CONFIG_TMPFS
2685        .llseek         = shmem_file_llseek,
2686        .read           = do_sync_read,
2687        .write          = do_sync_write,
2688        .aio_read       = shmem_file_aio_read,
2689        .aio_write      = generic_file_aio_write,
2690        .fsync          = noop_fsync,
2691        .splice_read    = shmem_file_splice_read,
2692        .splice_write   = generic_file_splice_write,
2693        .fallocate      = shmem_fallocate,
2694#endif
2695};
2696
2697static const struct inode_operations shmem_inode_operations = {
2698        .setattr        = shmem_setattr,
2699#ifdef CONFIG_TMPFS_XATTR
2700        .setxattr       = shmem_setxattr,
2701        .getxattr       = shmem_getxattr,
2702        .listxattr      = shmem_listxattr,
2703        .removexattr    = shmem_removexattr,
2704#endif
2705};
2706
2707static const struct inode_operations shmem_dir_inode_operations = {
2708#ifdef CONFIG_TMPFS
2709        .create         = shmem_create,
2710        .lookup         = simple_lookup,
2711        .link           = shmem_link,
2712        .unlink         = shmem_unlink,
2713        .symlink        = shmem_symlink,
2714        .mkdir          = shmem_mkdir,
2715        .rmdir          = shmem_rmdir,
2716        .mknod          = shmem_mknod,
2717        .rename         = shmem_rename,
2718#endif
2719#ifdef CONFIG_TMPFS_XATTR
2720        .setxattr       = shmem_setxattr,
2721        .getxattr       = shmem_getxattr,
2722        .listxattr      = shmem_listxattr,
2723        .removexattr    = shmem_removexattr,
2724#endif
2725#ifdef CONFIG_TMPFS_POSIX_ACL
2726        .setattr        = shmem_setattr,
2727#endif
2728};
2729
2730static const struct inode_operations shmem_special_inode_operations = {
2731#ifdef CONFIG_TMPFS_XATTR
2732        .setxattr       = shmem_setxattr,
2733        .getxattr       = shmem_getxattr,
2734        .listxattr      = shmem_listxattr,
2735        .removexattr    = shmem_removexattr,
2736#endif
2737#ifdef CONFIG_TMPFS_POSIX_ACL
2738        .setattr        = shmem_setattr,
2739#endif
2740};
2741
2742static const struct super_operations shmem_ops = {
2743        .alloc_inode    = shmem_alloc_inode,
2744        .destroy_inode  = shmem_destroy_inode,
2745#ifdef CONFIG_TMPFS
2746        .statfs         = shmem_statfs,
2747        .remount_fs     = shmem_remount_fs,
2748        .show_options   = shmem_show_options,
2749#endif
2750        .evict_inode    = shmem_evict_inode,
2751        .drop_inode     = generic_delete_inode,
2752        .put_super      = shmem_put_super,
2753};
2754
2755static const struct vm_operations_struct shmem_vm_ops = {
2756        .fault          = shmem_fault,
2757#ifdef CONFIG_NUMA
2758        .set_policy     = shmem_set_policy,
2759        .get_policy     = shmem_get_policy,
2760#endif
2761        .remap_pages    = generic_file_remap_pages,
2762};
2763
2764static struct dentry *shmem_mount(struct file_system_type *fs_type,
2765        int flags, const char *dev_name, void *data)
2766{
2767        return mount_nodev(fs_type, flags, data, shmem_fill_super);
2768}
2769
2770static struct file_system_type shmem_fs_type = {
2771        .owner          = THIS_MODULE,
2772        .name           = "tmpfs",
2773        .mount          = shmem_mount,
2774        .kill_sb        = kill_litter_super,
2775};
2776
2777int __init shmem_init(void)
2778{
2779        int error;
2780
2781        error = bdi_init(&shmem_backing_dev_info);
2782        if (error)
2783                goto out4;
2784
2785        error = shmem_init_inodecache();
2786        if (error)
2787                goto out3;
2788
2789        error = register_filesystem(&shmem_fs_type);
2790        if (error) {
2791                printk(KERN_ERR "Could not register tmpfs\n");
2792                goto out2;
2793        }
2794
2795        shm_mnt = vfs_kern_mount(&shmem_fs_type, MS_NOUSER,
2796                                 shmem_fs_type.name, NULL);
2797        if (IS_ERR(shm_mnt)) {
2798                error = PTR_ERR(shm_mnt);
2799                printk(KERN_ERR "Could not kern_mount tmpfs\n");
2800                goto out1;
2801        }
2802        return 0;
2803
2804out1:
2805        unregister_filesystem(&shmem_fs_type);
2806out2:
2807        shmem_destroy_inodecache();
2808out3:
2809        bdi_destroy(&shmem_backing_dev_info);
2810out4:
2811        shm_mnt = ERR_PTR(error);
2812        return error;
2813}
2814
2815#else /* !CONFIG_SHMEM */
2816
2817/*
2818 * tiny-shmem: simple shmemfs and tmpfs using ramfs code
2819 *
2820 * This is intended for small system where the benefits of the full
2821 * shmem code (swap-backed and resource-limited) are outweighed by
2822 * their complexity. On systems without swap this code should be
2823 * effectively equivalent, but much lighter weight.
2824 */
2825
2826#include <linux/ramfs.h>
2827
2828static struct file_system_type shmem_fs_type = {
2829        .name           = "tmpfs",
2830        .mount          = ramfs_mount,
2831        .kill_sb        = kill_litter_super,
2832};
2833
2834int __init shmem_init(void)
2835{
2836        BUG_ON(register_filesystem(&shmem_fs_type) != 0);
2837
2838        shm_mnt = kern_mount(&shmem_fs_type);
2839        BUG_ON(IS_ERR(shm_mnt));
2840
2841        return 0;
2842}
2843
2844int shmem_unuse(swp_entry_t swap, struct page *page)
2845{
2846        return 0;
2847}
2848
2849int shmem_lock(struct file *file, int lock, struct user_struct *user)
2850{
2851        return 0;
2852}
2853
2854void shmem_unlock_mapping(struct address_space *mapping)
2855{
2856}
2857
2858void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
2859{
2860        truncate_inode_pages_range(inode->i_mapping, lstart, lend);
2861}
2862EXPORT_SYMBOL_GPL(shmem_truncate_range);
2863
2864#define shmem_vm_ops                            generic_file_vm_ops
2865#define shmem_file_operations                   ramfs_file_operations
2866#define shmem_get_inode(sb, dir, mode, dev, flags)      ramfs_get_inode(sb, dir, mode, dev)
2867#define shmem_acct_size(flags, size)            0
2868#define shmem_unacct_size(flags, size)          do {} while (0)
2869
2870#endif /* CONFIG_SHMEM */
2871
2872/* common code */
2873
2874/**
2875 * shmem_file_setup - get an unlinked file living in tmpfs
2876 * @name: name for dentry (to be seen in /proc/<pid>/maps
2877 * @size: size to be set for the file
2878 * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
2879 */
2880struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
2881{
2882        int error;
2883        struct file *file;
2884        struct inode *inode;
2885        struct path path;
2886        struct dentry *root;
2887        struct qstr this;
2888
2889        if (IS_ERR(shm_mnt))
2890                return (void *)shm_mnt;
2891
2892        if (size < 0 || size > MAX_LFS_FILESIZE)
2893                return ERR_PTR(-EINVAL);
2894
2895        if (shmem_acct_size(flags, size))
2896                return ERR_PTR(-ENOMEM);
2897
2898        error = -ENOMEM;
2899        this.name = name;
2900        this.len = strlen(name);
2901        this.hash = 0; /* will go */
2902        root = shm_mnt->mnt_root;
2903        path.dentry = d_alloc(root, &this);
2904        if (!path.dentry)
2905                goto put_memory;
2906        path.mnt = mntget(shm_mnt);
2907
2908        error = -ENOSPC;
2909        inode = shmem_get_inode(root->d_sb, NULL, S_IFREG | S_IRWXUGO, 0, flags);
2910        if (!inode)
2911                goto put_dentry;
2912
2913        d_instantiate(path.dentry, inode);
2914        inode->i_size = size;
2915        clear_nlink(inode);     /* It is unlinked */
2916#ifndef CONFIG_MMU
2917        error = ramfs_nommu_expand_for_mapping(inode, size);
2918        if (error)
2919                goto put_dentry;
2920#endif
2921
2922        error = -ENFILE;
2923        file = alloc_file(&path, FMODE_WRITE | FMODE_READ,
2924                  &shmem_file_operations);
2925        if (!file)
2926                goto put_dentry;
2927
2928        return file;
2929
2930put_dentry:
2931        path_put(&path);
2932put_memory:
2933        shmem_unacct_size(flags, size);
2934        return ERR_PTR(error);
2935}
2936EXPORT_SYMBOL_GPL(shmem_file_setup);
2937
2938/**
2939 * shmem_zero_setup - setup a shared anonymous mapping
2940 * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
2941 */
2942int shmem_zero_setup(struct vm_area_struct *vma)
2943{
2944        struct file *file;
2945        loff_t size = vma->vm_end - vma->vm_start;
2946
2947        file = shmem_file_setup("dev/zero", size, vma->vm_flags);
2948        if (IS_ERR(file))
2949                return PTR_ERR(file);
2950
2951        if (vma->vm_file)
2952                fput(vma->vm_file);
2953        vma->vm_file = file;
2954        vma->vm_ops = &shmem_vm_ops;
2955        return 0;
2956}
2957
2958/**
2959 * shmem_read_mapping_page_gfp - read into page cache, using specified page allocation flags.
2960 * @mapping:    the page's address_space
2961 * @index:      the page index
2962 * @gfp:        the page allocator flags to use if allocating
2963 *
2964 * This behaves as a tmpfs "read_cache_page_gfp(mapping, index, gfp)",
2965 * with any new page allocations done using the specified allocation flags.
2966 * But read_cache_page_gfp() uses the ->readpage() method: which does not
2967 * suit tmpfs, since it may have pages in swapcache, and needs to find those
2968 * for itself; although drivers/gpu/drm i915 and ttm rely upon this support.
2969 *
2970 * i915_gem_object_get_pages_gtt() mixes __GFP_NORETRY | __GFP_NOWARN in
2971 * with the mapping_gfp_mask(), to avoid OOMing the machine unnecessarily.
2972 */
2973struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
2974                                         pgoff_t index, gfp_t gfp)
2975{
2976#ifdef CONFIG_SHMEM
2977        struct inode *inode = mapping->host;
2978        struct page *page;
2979        int error;
2980
2981        BUG_ON(mapping->a_ops != &shmem_aops);
2982        error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE, gfp, NULL);
2983        if (error)
2984                page = ERR_PTR(error);
2985        else
2986                unlock_page(page);
2987        return page;
2988#else
2989        /*
2990         * The tiny !SHMEM case uses ramfs without swap
2991         */
2992        return read_cache_page_gfp(mapping, index, gfp);
2993#endif
2994}
2995EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);
2996
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