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        void **slot;
 339        unsigned int ret = 0;
 340        struct radix_tree_iter iter;
 341
 342        if (!nr_pages)
 343                return 0;
 344
 345        rcu_read_lock();
 346restart:
 347        radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
 348                struct page *page;
 349repeat:
 350                page = radix_tree_deref_slot(slot);
 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 != *slot)) {
 368                        page_cache_release(page);
 369                        goto repeat;
 370                }
 371export:
 372                indices[ret] = iter.index;
 373                pages[ret] = page;
 374                if (++ret == nr_pages)
 375                        break;
 376        }
 377        rcu_read_unlock();
 378        return ret;
 379}
 380
 381/*
 382 * Remove swap entry from radix tree, free the swap and its page cache.
 383 */
 384static int shmem_free_swap(struct address_space *mapping,
 385                           pgoff_t index, void *radswap)
 386{
 387        int error;
 388
 389        spin_lock_irq(&mapping->tree_lock);
 390        error = shmem_radix_tree_replace(mapping, index, radswap, NULL);
 391        spin_unlock_irq(&mapping->tree_lock);
 392        if (!error)
 393                free_swap_and_cache(radix_to_swp_entry(radswap));
 394        return error;
 395}
 396
 397/*
 398 * Pagevec may contain swap entries, so shuffle up pages before releasing.
 399 */
 400static void shmem_deswap_pagevec(struct pagevec *pvec)
 401{
 402        int i, j;
 403
 404        for (i = 0, j = 0; i < pagevec_count(pvec); i++) {
 405                struct page *page = pvec->pages[i];
 406                if (!radix_tree_exceptional_entry(page))
 407                        pvec->pages[j++] = page;
 408        }
 409        pvec->nr = j;
 410}
 411
 412/*
 413 * SysV IPC SHM_UNLOCK restore Unevictable pages to their evictable lists.
 414 */
 415void shmem_unlock_mapping(struct address_space *mapping)
 416{
 417        struct pagevec pvec;
 418        pgoff_t indices[PAGEVEC_SIZE];
 419        pgoff_t index = 0;
 420
 421        pagevec_init(&pvec, 0);
 422        /*
 423         * Minor point, but we might as well stop if someone else SHM_LOCKs it.
 424         */
 425        while (!mapping_unevictable(mapping)) {
 426                /*
 427                 * Avoid pagevec_lookup(): find_get_pages() returns 0 as if it
 428                 * has finished, if it hits a row of PAGEVEC_SIZE swap entries.
 429                 */
 430                pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
 431                                        PAGEVEC_SIZE, pvec.pages, indices);
 432                if (!pvec.nr)
 433                        break;
 434                index = indices[pvec.nr - 1] + 1;
 435                shmem_deswap_pagevec(&pvec);
 436                check_move_unevictable_pages(pvec.pages, pvec.nr);
 437                pagevec_release(&pvec);
 438                cond_resched();
 439        }
 440}
 441
 442/*
 443 * Remove range of pages and swap entries from radix tree, and free them.
 444 * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate.
 445 */
 446static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
 447                                                                 bool unfalloc)
 448{
 449        struct address_space *mapping = inode->i_mapping;
 450        struct shmem_inode_info *info = SHMEM_I(inode);
 451        pgoff_t start = (lstart + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 452        pgoff_t end = (lend + 1) >> PAGE_CACHE_SHIFT;
 453        unsigned int partial_start = lstart & (PAGE_CACHE_SIZE - 1);
 454        unsigned int partial_end = (lend + 1) & (PAGE_CACHE_SIZE - 1);
 455        struct pagevec pvec;
 456        pgoff_t indices[PAGEVEC_SIZE];
 457        long nr_swaps_freed = 0;
 458        pgoff_t index;
 459        int i;
 460
 461        if (lend == -1)
 462                end = -1;       /* unsigned, so actually very big */
 463
 464        pagevec_init(&pvec, 0);
 465        index = start;
 466        while (index < end) {
 467                pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
 468                                min(end - index, (pgoff_t)PAGEVEC_SIZE),
 469                                                        pvec.pages, indices);
 470                if (!pvec.nr)
 471                        break;
 472                mem_cgroup_uncharge_start();
 473                for (i = 0; i < pagevec_count(&pvec); i++) {
 474                        struct page *page = pvec.pages[i];
 475
 476                        index = indices[i];
 477                        if (index >= end)
 478                                break;
 479
 480                        if (radix_tree_exceptional_entry(page)) {
 481                                if (unfalloc)
 482                                        continue;
 483                                nr_swaps_freed += !shmem_free_swap(mapping,
 484                                                                index, page);
 485                                continue;
 486                        }
 487
 488                        if (!trylock_page(page))
 489                                continue;
 490                        if (!unfalloc || !PageUptodate(page)) {
 491                                if (page->mapping == mapping) {
 492                                        VM_BUG_ON(PageWriteback(page));
 493                                        truncate_inode_page(mapping, page);
 494                                }
 495                        }
 496                        unlock_page(page);
 497                }
 498                shmem_deswap_pagevec(&pvec);
 499                pagevec_release(&pvec);
 500                mem_cgroup_uncharge_end();
 501                cond_resched();
 502                index++;
 503        }
 504
 505        if (partial_start) {
 506                struct page *page = NULL;
 507                shmem_getpage(inode, start - 1, &page, SGP_READ, NULL);
 508                if (page) {
 509                        unsigned int top = PAGE_CACHE_SIZE;
 510                        if (start > end) {
 511                                top = partial_end;
 512                                partial_end = 0;
 513                        }
 514                        zero_user_segment(page, partial_start, top);
 515                        set_page_dirty(page);
 516                        unlock_page(page);
 517                        page_cache_release(page);
 518                }
 519        }
 520        if (partial_end) {
 521                struct page *page = NULL;
 522                shmem_getpage(inode, end, &page, SGP_READ, NULL);
 523                if (page) {
 524                        zero_user_segment(page, 0, partial_end);
 525                        set_page_dirty(page);
 526                        unlock_page(page);
 527                        page_cache_release(page);
 528                }
 529        }
 530        if (start >= end)
 531                return;
 532
 533        index = start;
 534        for ( ; ; ) {
 535                cond_resched();
 536                pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
 537                                min(end - index, (pgoff_t)PAGEVEC_SIZE),
 538                                                        pvec.pages, indices);
 539                if (!pvec.nr) {
 540                        if (index == start || unfalloc)
 541                                break;
 542                        index = start;
 543                        continue;
 544                }
 545                if ((index == start || unfalloc) && indices[0] >= end) {
 546                        shmem_deswap_pagevec(&pvec);
 547                        pagevec_release(&pvec);
 548                        break;
 549                }
 550                mem_cgroup_uncharge_start();
 551                for (i = 0; i < pagevec_count(&pvec); i++) {
 552                        struct page *page = pvec.pages[i];
 553
 554                        index = indices[i];
 555                        if (index >= end)
 556                                break;
 557
 558                        if (radix_tree_exceptional_entry(page)) {
 559                                if (unfalloc)
 560                                        continue;
 561                                nr_swaps_freed += !shmem_free_swap(mapping,
 562                                                                index, page);
 563                                continue;
 564                        }
 565
 566                        lock_page(page);
 567                        if (!unfalloc || !PageUptodate(page)) {
 568                                if (page->mapping == mapping) {
 569                                        VM_BUG_ON(PageWriteback(page));
 570                                        truncate_inode_page(mapping, page);
 571                                }
 572                        }
 573                        unlock_page(page);
 574                }
 575                shmem_deswap_pagevec(&pvec);
 576                pagevec_release(&pvec);
 577                mem_cgroup_uncharge_end();
 578                index++;
 579        }
 580
 581        spin_lock(&info->lock);
 582        info->swapped -= nr_swaps_freed;
 583        shmem_recalc_inode(inode);
 584        spin_unlock(&info->lock);
 585}
 586
 587void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
 588{
 589        shmem_undo_range(inode, lstart, lend, false);
 590        inode->i_ctime = inode->i_mtime = CURRENT_TIME;
 591}
 592EXPORT_SYMBOL_GPL(shmem_truncate_range);
 593
 594static int shmem_setattr(struct dentry *dentry, struct iattr *attr)
 595{
 596        struct inode *inode = dentry->d_inode;
 597        int error;
 598
 599        error = inode_change_ok(inode, attr);
 600        if (error)
 601                return error;
 602
 603        if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
 604                loff_t oldsize = inode->i_size;
 605                loff_t newsize = attr->ia_size;
 606
 607                if (newsize != oldsize) {
 608                        i_size_write(inode, newsize);
 609                        inode->i_ctime = inode->i_mtime = CURRENT_TIME;
 610                }
 611                if (newsize < oldsize) {
 612                        loff_t holebegin = round_up(newsize, PAGE_SIZE);
 613                        unmap_mapping_range(inode->i_mapping, holebegin, 0, 1);
 614                        shmem_truncate_range(inode, newsize, (loff_t)-1);
 615                        /* unmap again to remove racily COWed private pages */
 616                        unmap_mapping_range(inode->i_mapping, holebegin, 0, 1);
 617                }
 618        }
 619
 620        setattr_copy(inode, attr);
 621#ifdef CONFIG_TMPFS_POSIX_ACL
 622        if (attr->ia_valid & ATTR_MODE)
 623                error = generic_acl_chmod(inode);
 624#endif
 625        return error;
 626}
 627
 628static void shmem_evict_inode(struct inode *inode)
 629{
 630        struct shmem_inode_info *info = SHMEM_I(inode);
 631
 632        if (inode->i_mapping->a_ops == &shmem_aops) {
 633                shmem_unacct_size(info->flags, inode->i_size);
 634                inode->i_size = 0;
 635                shmem_truncate_range(inode, 0, (loff_t)-1);
 636                if (!list_empty(&info->swaplist)) {
 637                        mutex_lock(&shmem_swaplist_mutex);
 638                        list_del_init(&info->swaplist);
 639                        mutex_unlock(&shmem_swaplist_mutex);
 640                }
 641        } else
 642                kfree(info->symlink);
 643
 644        simple_xattrs_free(&info->xattrs);
 645        WARN_ON(inode->i_blocks);
 646        shmem_free_inode(inode->i_sb);
 647        clear_inode(inode);
 648}
 649
 650/*
 651 * If swap found in inode, free it and move page from swapcache to filecache.
 652 */
 653static int shmem_unuse_inode(struct shmem_inode_info *info,
 654                             swp_entry_t swap, struct page **pagep)
 655{
 656        struct address_space *mapping = info->vfs_inode.i_mapping;
 657        void *radswap;
 658        pgoff_t index;
 659        gfp_t gfp;
 660        int error = 0;
 661
 662        radswap = swp_to_radix_entry(swap);
 663        index = radix_tree_locate_item(&mapping->page_tree, radswap);
 664        if (index == -1)
 665                return 0;
 666
 667        /*
 668         * Move _head_ to start search for next from here.
 669         * But be careful: shmem_evict_inode checks list_empty without taking
 670         * mutex, and there's an instant in list_move_tail when info->swaplist
 671         * would appear empty, if it were the only one on shmem_swaplist.
 672         */
 673        if (shmem_swaplist.next != &info->swaplist)
 674                list_move_tail(&shmem_swaplist, &info->swaplist);
 675
 676        gfp = mapping_gfp_mask(mapping);
 677        if (shmem_should_replace_page(*pagep, gfp)) {
 678                mutex_unlock(&shmem_swaplist_mutex);
 679                error = shmem_replace_page(pagep, gfp, info, index);
 680                mutex_lock(&shmem_swaplist_mutex);
 681                /*
 682                 * We needed to drop mutex to make that restrictive page
 683                 * allocation, but the inode might have been freed while we
 684                 * dropped it: although a racing shmem_evict_inode() cannot
 685                 * complete without emptying the radix_tree, our page lock
 686                 * on this swapcache page is not enough to prevent that -
 687                 * free_swap_and_cache() of our swap entry will only
 688                 * trylock_page(), removing swap from radix_tree whatever.
 689                 *
 690                 * We must not proceed to shmem_add_to_page_cache() if the
 691                 * inode has been freed, but of course we cannot rely on
 692                 * inode or mapping or info to check that.  However, we can
 693                 * safely check if our swap entry is still in use (and here
 694                 * it can't have got reused for another page): if it's still
 695                 * in use, then the inode cannot have been freed yet, and we
 696                 * can safely proceed (if it's no longer in use, that tells
 697                 * nothing about the inode, but we don't need to unuse swap).
 698                 */
 699                if (!page_swapcount(*pagep))
 700                        error = -ENOENT;
 701        }
 702
 703        /*
 704         * We rely on shmem_swaplist_mutex, not only to protect the swaplist,
 705         * but also to hold up shmem_evict_inode(): so inode cannot be freed
 706         * beneath us (pagelock doesn't help until the page is in pagecache).
 707         */
 708        if (!error)
 709                error = shmem_add_to_page_cache(*pagep, mapping, index,
 710                                                GFP_NOWAIT, radswap);
 711        if (error != -ENOMEM) {
 712                /*
 713                 * Truncation and eviction use free_swap_and_cache(), which
 714                 * only does trylock page: if we raced, best clean up here.
 715                 */
 716                delete_from_swap_cache(*pagep);
 717                set_page_dirty(*pagep);
 718                if (!error) {
 719                        spin_lock(&info->lock);
 720                        info->swapped--;
 721                        spin_unlock(&info->lock);
 722                        swap_free(swap);
 723                }
 724                error = 1;      /* not an error, but entry was found */
 725        }
 726        return error;
 727}
 728
 729/*
 730 * Search through swapped inodes to find and replace swap by page.
 731 */
 732int shmem_unuse(swp_entry_t swap, struct page *page)
 733{
 734        struct list_head *this, *next;
 735        struct shmem_inode_info *info;
 736        int found = 0;
 737        int error = 0;
 738
 739        /*
 740         * There's a faint possibility that swap page was replaced before
 741         * caller locked it: caller will come back later with the right page.
 742         */
 743        if (unlikely(!PageSwapCache(page) || page_private(page) != swap.val))
 744                goto out;
 745
 746        /*
 747         * Charge page using GFP_KERNEL while we can wait, before taking
 748         * the shmem_swaplist_mutex which might hold up shmem_writepage().
 749         * Charged back to the user (not to caller) when swap account is used.
 750         */
 751        error = mem_cgroup_cache_charge(page, current->mm, GFP_KERNEL);
 752        if (error)
 753                goto out;
 754        /* No radix_tree_preload: swap entry keeps a place for page in tree */
 755
 756        mutex_lock(&shmem_swaplist_mutex);
 757        list_for_each_safe(this, next, &shmem_swaplist) {
 758                info = list_entry(this, struct shmem_inode_info, swaplist);
 759                if (info->swapped)
 760                        found = shmem_unuse_inode(info, swap, &page);
 761                else
 762                        list_del_init(&info->swaplist);
 763                cond_resched();
 764                if (found)
 765                        break;
 766        }
 767        mutex_unlock(&shmem_swaplist_mutex);
 768
 769        if (found < 0)
 770                error = found;
 771out:
 772        unlock_page(page);
 773        page_cache_release(page);
 774        return error;
 775}
 776
 777/*
 778 * Move the page from the page cache to the swap cache.
 779 */
 780static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 781{
 782        struct shmem_inode_info *info;
 783        struct address_space *mapping;
 784        struct inode *inode;
 785        swp_entry_t swap;
 786        pgoff_t index;
 787
 788        BUG_ON(!PageLocked(page));
 789        mapping = page->mapping;
 790        index = page->index;
 791        inode = mapping->host;
 792        info = SHMEM_I(inode);
 793        if (info->flags & VM_LOCKED)
 794                goto redirty;
 795        if (!total_swap_pages)
 796                goto redirty;
 797
 798        /*
 799         * shmem_backing_dev_info's capabilities prevent regular writeback or
 800         * sync from ever calling shmem_writepage; but a stacking filesystem
 801         * might use ->writepage of its underlying filesystem, in which case
 802         * tmpfs should write out to swap only in response to memory pressure,
 803         * and not for the writeback threads or sync.
 804         */
 805        if (!wbc->for_reclaim) {
 806                WARN_ON_ONCE(1);        /* Still happens? Tell us about it! */
 807                goto redirty;
 808        }
 809
 810        /*
 811         * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC
 812         * value into swapfile.c, the only way we can correctly account for a
 813         * fallocated page arriving here is now to initialize it and write it.
 814         *
 815         * That's okay for a page already fallocated earlier, but if we have
 816         * not yet completed the fallocation, then (a) we want to keep track
 817         * of this page in case we have to undo it, and (b) it may not be a
 818         * good idea to continue anyway, once we're pushing into swap.  So
 819         * reactivate the page, and let shmem_fallocate() quit when too many.
 820         */
 821        if (!PageUptodate(page)) {
 822                if (inode->i_private) {
 823                        struct shmem_falloc *shmem_falloc;
 824                        spin_lock(&inode->i_lock);
 825                        shmem_falloc = inode->i_private;
 826                        if (shmem_falloc &&
 827                            index >= shmem_falloc->start &&
 828                            index < shmem_falloc->next)
 829                                shmem_falloc->nr_unswapped++;
 830                        else
 831                                shmem_falloc = NULL;
 832                        spin_unlock(&inode->i_lock);
 833                        if (shmem_falloc)
 834                                goto redirty;
 835                }
 836                clear_highpage(page);
 837                flush_dcache_page(page);
 838                SetPageUptodate(page);
 839        }
 840
 841        swap = get_swap_page();
 842        if (!swap.val)
 843                goto redirty;
 844
 845        /*
 846         * Add inode to shmem_unuse()'s list of swapped-out inodes,
 847         * if it's not already there.  Do it now before the page is
 848         * moved to swap cache, when its pagelock no longer protects
 849         * the inode from eviction.  But don't unlock the mutex until
 850         * we've incremented swapped, because shmem_unuse_inode() will
 851         * prune a !swapped inode from the swaplist under this mutex.
 852         */
 853        mutex_lock(&shmem_swaplist_mutex);
 854        if (list_empty(&info->swaplist))
 855                list_add_tail(&info->swaplist, &shmem_swaplist);
 856
 857        if (add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
 858                swap_shmem_alloc(swap);
 859                shmem_delete_from_page_cache(page, swp_to_radix_entry(swap));
 860
 861                spin_lock(&info->lock);
 862                info->swapped++;
 863                shmem_recalc_inode(inode);
 864                spin_unlock(&info->lock);
 865
 866                mutex_unlock(&shmem_swaplist_mutex);
 867                BUG_ON(page_mapped(page));
 868                swap_writepage(page, wbc);
 869                return 0;
 870        }
 871
 872        mutex_unlock(&shmem_swaplist_mutex);
 873        swapcache_free(swap, NULL);
 874redirty:
 875        set_page_dirty(page);
 876        if (wbc->for_reclaim)
 877                return AOP_WRITEPAGE_ACTIVATE;  /* Return with page locked */
 878        unlock_page(page);
 879        return 0;
 880}
 881
 882#ifdef CONFIG_NUMA
 883#ifdef CONFIG_TMPFS
 884static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
 885{
 886        char buffer[64];
 887
 888        if (!mpol || mpol->mode == MPOL_DEFAULT)
 889                return;         /* show nothing */
 890
 891        mpol_to_str(buffer, sizeof(buffer), mpol);
 892
 893        seq_printf(seq, ",mpol=%s", buffer);
 894}
 895
 896static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
 897{
 898        struct mempolicy *mpol = NULL;
 899        if (sbinfo->mpol) {
 900                spin_lock(&sbinfo->stat_lock);  /* prevent replace/use races */
 901                mpol = sbinfo->mpol;
 902                mpol_get(mpol);
 903                spin_unlock(&sbinfo->stat_lock);
 904        }
 905        return mpol;
 906}
 907#endif /* CONFIG_TMPFS */
 908
 909static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
 910                        struct shmem_inode_info *info, pgoff_t index)
 911{
 912        struct vm_area_struct pvma;
 913        struct page *page;
 914
 915        /* Create a pseudo vma that just contains the policy */
 916        pvma.vm_start = 0;
 917        /* Bias interleave by inode number to distribute better across nodes */
 918        pvma.vm_pgoff = index + info->vfs_inode.i_ino;
 919        pvma.vm_ops = NULL;
 920        pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
 921
 922        page = swapin_readahead(swap, gfp, &pvma, 0);
 923
 924        /* Drop reference taken by mpol_shared_policy_lookup() */
 925        mpol_cond_put(pvma.vm_policy);
 926
 927        return page;
 928}
 929
 930static struct page *shmem_alloc_page(gfp_t gfp,
 931                        struct shmem_inode_info *info, pgoff_t index)
 932{
 933        struct vm_area_struct pvma;
 934        struct page *page;
 935
 936        /* Create a pseudo vma that just contains the policy */
 937        pvma.vm_start = 0;
 938        /* Bias interleave by inode number to distribute better across nodes */
 939        pvma.vm_pgoff = index + info->vfs_inode.i_ino;
 940        pvma.vm_ops = NULL;
 941        pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
 942
 943        page = alloc_page_vma(gfp, &pvma, 0);
 944
 945        /* Drop reference taken by mpol_shared_policy_lookup() */
 946        mpol_cond_put(pvma.vm_policy);
 947
 948        return page;
 949}
 950#else /* !CONFIG_NUMA */
 951#ifdef CONFIG_TMPFS
 952static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
 953{
 954}
 955#endif /* CONFIG_TMPFS */
 956
 957static inline struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
 958                        struct shmem_inode_info *info, pgoff_t index)
 959{
 960        return swapin_readahead(swap, gfp, NULL, 0);
 961}
 962
 963static inline struct page *shmem_alloc_page(gfp_t gfp,
 964                        struct shmem_inode_info *info, pgoff_t index)
 965{
 966        return alloc_page(gfp);
 967}
 968#endif /* CONFIG_NUMA */
 969
 970#if !defined(CONFIG_NUMA) || !defined(CONFIG_TMPFS)
 971static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
 972{
 973        return NULL;
 974}
 975#endif
 976
 977/*
 978 * When a page is moved from swapcache to shmem filecache (either by the
 979 * usual swapin of shmem_getpage_gfp(), or by the less common swapoff of
 980 * shmem_unuse_inode()), it may have been read in earlier from swap, in
 981 * ignorance of the mapping it belongs to.  If that mapping has special
 982 * constraints (like the gma500 GEM driver, which requires RAM below 4GB),
 983 * we may need to copy to a suitable page before moving to filecache.
 984 *
 985 * In a future release, this may well be extended to respect cpuset and
 986 * NUMA mempolicy, and applied also to anonymous pages in do_swap_page();
 987 * but for now it is a simple matter of zone.
 988 */
 989static bool shmem_should_replace_page(struct page *page, gfp_t gfp)
 990{
 991        return page_zonenum(page) > gfp_zone(gfp);
 992}
 993
 994static int shmem_replace_page(struct page **pagep, gfp_t gfp,
 995                                struct shmem_inode_info *info, pgoff_t index)
 996{
 997        struct page *oldpage, *newpage;
 998        struct address_space *swap_mapping;
 999        pgoff_t swap_index;
1000        int error;
1001
1002        oldpage = *pagep;
1003        swap_index = page_private(oldpage);
1004        swap_mapping = page_mapping(oldpage);
1005
1006        /*
1007         * We have arrived here because our zones are constrained, so don't
1008         * limit chance of success by further cpuset and node constraints.
1009         */
1010        gfp &= ~GFP_CONSTRAINT_MASK;
1011        newpage = shmem_alloc_page(gfp, info, index);
1012        if (!newpage)
1013                return -ENOMEM;
1014
1015        page_cache_get(newpage);
1016        copy_highpage(newpage, oldpage);
1017        flush_dcache_page(newpage);
1018
1019        __set_page_locked(newpage);
1020        SetPageUptodate(newpage);
1021        SetPageSwapBacked(newpage);
1022        set_page_private(newpage, swap_index);
1023        SetPageSwapCache(newpage);
1024
1025        /*
1026         * Our caller will very soon move newpage out of swapcache, but it's
1027         * a nice clean interface for us to replace oldpage by newpage there.
1028         */
1029        spin_lock_irq(&swap_mapping->tree_lock);
1030        error = shmem_radix_tree_replace(swap_mapping, swap_index, oldpage,
1031                                                                   newpage);
1032        if (!error) {
1033                __inc_zone_page_state(newpage, NR_FILE_PAGES);
1034                __dec_zone_page_state(oldpage, NR_FILE_PAGES);
1035        }
1036        spin_unlock_irq(&swap_mapping->tree_lock);
1037
1038        if (unlikely(error)) {
1039                /*
1040                 * Is this possible?  I think not, now that our callers check
1041                 * both PageSwapCache and page_private after getting page lock;
1042                 * but be defensive.  Reverse old to newpage for clear and free.
1043                 */
1044                oldpage = newpage;
1045        } else {
1046                mem_cgroup_replace_page_cache(oldpage, newpage);
1047                lru_cache_add_anon(newpage);
1048                *pagep = newpage;
1049        }
1050
1051        ClearPageSwapCache(oldpage);
1052        set_page_private(oldpage, 0);
1053
1054        unlock_page(oldpage);
1055        page_cache_release(oldpage);
1056        page_cache_release(oldpage);
1057        return error;
1058}
1059
1060/*
1061 * shmem_getpage_gfp - find page in cache, or get from swap, or allocate
1062 *
1063 * If we allocate a new one we do not mark it dirty. That's up to the
1064 * vm. If we swap it in we mark it dirty since we also free the swap
1065 * entry since a page cannot live in both the swap and page cache
1066 */
1067static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
1068        struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type)
1069{
1070        struct address_space *mapping = inode->i_mapping;
1071        struct shmem_inode_info *info;
1072        struct shmem_sb_info *sbinfo;
1073        struct page *page;
1074        swp_entry_t swap;
1075        int error;
1076        int once = 0;
1077        int alloced = 0;
1078
1079        if (index > (MAX_LFS_FILESIZE >> PAGE_CACHE_SHIFT))
1080                return -EFBIG;
1081repeat:
1082        swap.val = 0;
1083        page = find_lock_page(mapping, index);
1084        if (radix_tree_exceptional_entry(page)) {
1085                swap = radix_to_swp_entry(page);
1086                page = NULL;
1087        }
1088
1089        if (sgp != SGP_WRITE && sgp != SGP_FALLOC &&
1090            ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
1091                error = -EINVAL;
1092                goto failed;
1093        }
1094
1095        /* fallocated page? */
1096        if (page && !PageUptodate(page)) {
1097                if (sgp != SGP_READ)
1098                        goto clear;
1099                unlock_page(page);
1100                page_cache_release(page);
1101                page = NULL;
1102        }
1103        if (page || (sgp == SGP_READ && !swap.val)) {
1104                *pagep = page;
1105                return 0;
1106        }
1107
1108        /*
1109         * Fast cache lookup did not find it:
1110         * bring it back from swap or allocate.
1111         */
1112        info = SHMEM_I(inode);
1113        sbinfo = SHMEM_SB(inode->i_sb);
1114
1115        if (swap.val) {
1116                /* Look it up and read it in.. */
1117                page = lookup_swap_cache(swap);
1118                if (!page) {
1119                        /* here we actually do the io */
1120                        if (fault_type)
1121                                *fault_type |= VM_FAULT_MAJOR;
1122                        page = shmem_swapin(swap, gfp, info, index);
1123                        if (!page) {
1124                                error = -ENOMEM;
1125                                goto failed;
1126                        }
1127                }
1128
1129                /* We have to do this with page locked to prevent races */
1130                lock_page(page);
1131                if (!PageSwapCache(page) || page_private(page) != swap.val ||
1132                    !shmem_confirm_swap(mapping, index, swap)) {
1133                        error = -EEXIST;        /* try again */
1134                        goto unlock;
1135                }
1136                if (!PageUptodate(page)) {
1137                        error = -EIO;
1138                        goto failed;
1139                }
1140                wait_on_page_writeback(page);
1141
1142                if (shmem_should_replace_page(page, gfp)) {
1143                        error = shmem_replace_page(&page, gfp, info, index);
1144                        if (error)
1145                                goto failed;
1146                }
1147
1148                error = mem_cgroup_cache_charge(page, current->mm,
1149                                                gfp & GFP_RECLAIM_MASK);
1150                if (!error) {
1151                        error = shmem_add_to_page_cache(page, mapping, index,
1152                                                gfp, swp_to_radix_entry(swap));
1153                        /*
1154                         * We already confirmed swap under page lock, and make
1155                         * no memory allocation here, so usually no possibility
1156                         * of error; but free_swap_and_cache() only trylocks a
1157                         * page, so it is just possible that the entry has been
1158                         * truncated or holepunched since swap was confirmed.
1159                         * shmem_undo_range() will have done some of the
1160                         * unaccounting, now delete_from_swap_cache() will do
1161                         * the rest (including mem_cgroup_uncharge_swapcache).
1162                         * Reset swap.val? No, leave it so "failed" goes back to
1163                         * "repeat": reading a hole and writing should succeed.
1164                         */
1165                        if (error)
1166                                delete_from_swap_cache(page);
1167                }
1168                if (error)
1169                        goto failed;
1170
1171                spin_lock(&info->lock);
1172                info->swapped--;
1173                shmem_recalc_inode(inode);
1174                spin_unlock(&info->lock);
1175
1176                delete_from_swap_cache(page);
1177                set_page_dirty(page);
1178                swap_free(swap);
1179
1180        } else {
1181                if (shmem_acct_block(info->flags)) {
1182                        error = -ENOSPC;
1183                        goto failed;
1184                }
1185                if (sbinfo->max_blocks) {
1186                        if (percpu_counter_compare(&sbinfo->used_blocks,
1187                                                sbinfo->max_blocks) >= 0) {
1188                                error = -ENOSPC;
1189                                goto unacct;
1190                        }
1191                        percpu_counter_inc(&sbinfo->used_blocks);
1192                }
1193
1194                page = shmem_alloc_page(gfp, info, index);
1195                if (!page) {
1196                        error = -ENOMEM;
1197                        goto decused;
1198                }
1199
1200                SetPageSwapBacked(page);
1201                __set_page_locked(page);
1202                error = mem_cgroup_cache_charge(page, current->mm,
1203                                                gfp & GFP_RECLAIM_MASK);
1204                if (error)
1205                        goto decused;
1206                error = radix_tree_preload(gfp & GFP_RECLAIM_MASK);
1207                if (!error) {
1208                        error = shmem_add_to_page_cache(page, mapping, index,
1209                                                        gfp, NULL);
1210                        radix_tree_preload_end();
1211                }
1212                if (error) {
1213                        mem_cgroup_uncharge_cache_page(page);
1214                        goto decused;
1215                }
1216                lru_cache_add_anon(page);
1217
1218                spin_lock(&info->lock);
1219                info->alloced++;
1220                inode->i_blocks += BLOCKS_PER_PAGE;
1221                shmem_recalc_inode(inode);
1222                spin_unlock(&info->lock);
1223                alloced = true;
1224
1225                /*
1226                 * Let SGP_FALLOC use the SGP_WRITE optimization on a new page.
1227                 */
1228                if (sgp == SGP_FALLOC)
1229                        sgp = SGP_WRITE;
1230clear:
1231                /*
1232                 * Let SGP_WRITE caller clear ends if write does not fill page;
1233                 * but SGP_FALLOC on a page fallocated earlier must initialize
1234                 * it now, lest undo on failure cancel our earlier guarantee.
1235                 */
1236                if (sgp != SGP_WRITE) {
1237                        clear_highpage(page);
1238                        flush_dcache_page(page);
1239                        SetPageUptodate(page);
1240                }
1241                if (sgp == SGP_DIRTY)
1242                        set_page_dirty(page);
1243        }
1244
1245        /* Perhaps the file has been truncated since we checked */
1246        if (sgp != SGP_WRITE && sgp != SGP_FALLOC &&
1247            ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
1248                error = -EINVAL;
1249                if (alloced)
1250                        goto trunc;
1251                else
1252                        goto failed;
1253        }
1254        *pagep = page;
1255        return 0;
1256
1257        /*
1258         * Error recovery.
1259         */
1260trunc:
1261        info = SHMEM_I(inode);
1262        ClearPageDirty(page);
1263        delete_from_page_cache(page);
1264        spin_lock(&info->lock);
1265        info->alloced--;
1266        inode->i_blocks -= BLOCKS_PER_PAGE;
1267        spin_unlock(&info->lock);
1268decused:
1269        sbinfo = SHMEM_SB(inode->i_sb);
1270        if (sbinfo->max_blocks)
1271                percpu_counter_add(&sbinfo->used_blocks, -1);
1272unacct:
1273        shmem_unacct_blocks(info->flags, 1);
1274failed:
1275        if (swap.val && error != -EINVAL &&
1276            !shmem_confirm_swap(mapping, index, swap))
1277                error = -EEXIST;
1278unlock:
1279        if (page) {
1280                unlock_page(page);
1281                page_cache_release(page);
1282        }
1283        if (error == -ENOSPC && !once++) {
1284                info = SHMEM_I(inode);
1285                spin_lock(&info->lock);
1286                shmem_recalc_inode(inode);
1287                spin_unlock(&info->lock);
1288                goto repeat;
1289        }
1290        if (error == -EEXIST)   /* from above or from radix_tree_insert */
1291                goto repeat;
1292        return error;
1293}
1294
1295static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1296{
1297        struct inode *inode = file_inode(vma->vm_file);
1298        int error;
1299        int ret = VM_FAULT_LOCKED;
1300
1301        error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret);
1302        if (error)
1303                return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1304
1305        if (ret & VM_FAULT_MAJOR) {
1306                count_vm_event(PGMAJFAULT);
1307                mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1308        }
1309        return ret;
1310}
1311
1312#ifdef CONFIG_NUMA
1313static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *mpol)
1314{
1315        struct inode *inode = file_inode(vma->vm_file);
1316        return mpol_set_shared_policy(&SHMEM_I(inode)->policy, vma, mpol);
1317}
1318
1319static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
1320                                          unsigned long addr)
1321{
1322        struct inode *inode = file_inode(vma->vm_file);
1323        pgoff_t index;
1324
1325        index = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1326        return mpol_shared_policy_lookup(&SHMEM_I(inode)->policy, index);
1327}
1328#endif
1329
1330int shmem_lock(struct file *file, int lock, struct user_struct *user)
1331{
1332        struct inode *inode = file_inode(file);
1333        struct shmem_inode_info *info = SHMEM_I(inode);
1334        int retval = -ENOMEM;
1335
1336        spin_lock(&info->lock);
1337        if (lock && !(info->flags & VM_LOCKED)) {
1338                if (!user_shm_lock(inode->i_size, user))
1339                        goto out_nomem;
1340                info->flags |= VM_LOCKED;
1341                mapping_set_unevictable(file->f_mapping);
1342        }
1343        if (!lock && (info->flags & VM_LOCKED) && user) {
1344                user_shm_unlock(inode->i_size, user);
1345                info->flags &= ~VM_LOCKED;
1346                mapping_clear_unevictable(file->f_mapping);
1347        }
1348        retval = 0;
1349
1350out_nomem:
1351        spin_unlock(&info->lock);
1352        return retval;
1353}
1354
1355static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1356{
1357        file_accessed(file);
1358        vma->vm_ops = &shmem_vm_ops;
1359        return 0;
1360}
1361
1362static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir,
1363                                     umode_t mode, dev_t dev, unsigned long flags)
1364{
1365        struct inode *inode;
1366        struct shmem_inode_info *info;
1367        struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1368
1369        if (shmem_reserve_inode(sb))
1370                return NULL;
1371
1372        inode = new_inode(sb);
1373        if (inode) {
1374                inode->i_ino = get_next_ino();
1375                inode_init_owner(inode, dir, mode);
1376                inode->i_blocks = 0;
1377                inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1378                inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1379                inode->i_generation = get_seconds();
1380                info = SHMEM_I(inode);
1381                memset(info, 0, (char *)inode - (char *)info);
1382                spin_lock_init(&info->lock);
1383                info->flags = flags & VM_NORESERVE;
1384                INIT_LIST_HEAD(&info->swaplist);
1385                simple_xattrs_init(&info->xattrs);
1386                cache_no_acl(inode);
1387
1388                switch (mode & S_IFMT) {
1389                default:
1390                        inode->i_op = &shmem_special_inode_operations;
1391                        init_special_inode(inode, mode, dev);
1392                        break;
1393                case S_IFREG:
1394                        inode->i_mapping->a_ops = &shmem_aops;
1395                        inode->i_op = &shmem_inode_operations;
1396                        inode->i_fop = &shmem_file_operations;
1397                        mpol_shared_policy_init(&info->policy,
1398                                                 shmem_get_sbmpol(sbinfo));
1399                        break;
1400                case S_IFDIR:
1401                        inc_nlink(inode);
1402                        /* Some things misbehave if size == 0 on a directory */
1403                        inode->i_size = 2 * BOGO_DIRENT_SIZE;
1404                        inode->i_op = &shmem_dir_inode_operations;
1405                        inode->i_fop = &simple_dir_operations;
1406                        break;
1407                case S_IFLNK:
1408                        /*
1409                         * Must not load anything in the rbtree,
1410                         * mpol_free_shared_policy will not be called.
1411                         */
1412                        mpol_shared_policy_init(&info->policy, NULL);
1413                        break;
1414                }
1415        } else
1416                shmem_free_inode(sb);
1417        return inode;
1418}
1419
1420#ifdef CONFIG_TMPFS
1421static const struct inode_operations shmem_symlink_inode_operations;
1422static const struct inode_operations shmem_short_symlink_operations;
1423
1424#ifdef CONFIG_TMPFS_XATTR
1425static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
1426#else
1427#define shmem_initxattrs NULL
1428#endif
1429
1430static int
1431shmem_write_begin(struct file *file, struct address_space *mapping,
1432                        loff_t pos, unsigned len, unsigned flags,
1433                        struct page **pagep, void **fsdata)
1434{
1435        struct inode *inode = mapping->host;
1436        pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1437        return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
1438}
1439
1440static int
1441shmem_write_end(struct file *file, struct address_space *mapping,
1442                        loff_t pos, unsigned len, unsigned copied,
1443                        struct page *page, void *fsdata)
1444{
1445        struct inode *inode = mapping->host;
1446
1447        if (pos + copied > inode->i_size)
1448                i_size_write(inode, pos + copied);
1449
1450        if (!PageUptodate(page)) {
1451                if (copied < PAGE_CACHE_SIZE) {
1452                        unsigned from = pos & (PAGE_CACHE_SIZE - 1);
1453                        zero_user_segments(page, 0, from,
1454                                        from + copied, PAGE_CACHE_SIZE);
1455                }
1456                SetPageUptodate(page);
1457        }
1458        set_page_dirty(page);
1459        unlock_page(page);
1460        page_cache_release(page);
1461
1462        return copied;
1463}
1464
1465static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
1466{
1467        struct inode *inode = file_inode(filp);
1468        struct address_space *mapping = inode->i_mapping;
1469        pgoff_t index;
1470        unsigned long offset;
1471        enum sgp_type sgp = SGP_READ;
1472
1473        /*
1474         * Might this read be for a stacking filesystem?  Then when reading
1475         * holes of a sparse file, we actually need to allocate those pages,
1476         * and even mark them dirty, so it cannot exceed the max_blocks limit.
1477         */
1478        if (segment_eq(get_fs(), KERNEL_DS))
1479                sgp = SGP_DIRTY;
1480
1481        index = *ppos >> PAGE_CACHE_SHIFT;
1482        offset = *ppos & ~PAGE_CACHE_MASK;
1483
1484        for (;;) {
1485                struct page *page = NULL;
1486                pgoff_t end_index;
1487                unsigned long nr, ret;
1488                loff_t i_size = i_size_read(inode);
1489
1490                end_index = i_size >> PAGE_CACHE_SHIFT;
1491                if (index > end_index)
1492                        break;
1493                if (index == end_index) {
1494                        nr = i_size & ~PAGE_CACHE_MASK;
1495                        if (nr <= offset)
1496                                break;
1497                }
1498
1499                desc->error = shmem_getpage(inode, index, &page, sgp, NULL);
1500                if (desc->error) {
1501                        if (desc->error == -EINVAL)
1502                                desc->error = 0;
1503                        break;
1504                }
1505                if (page)
1506                        unlock_page(page);
1507
1508                /*
1509                 * We must evaluate after, since reads (unlike writes)
1510                 * are called without i_mutex protection against truncate
1511                 */
1512                nr = PAGE_CACHE_SIZE;
1513                i_size = i_size_read(inode);
1514                end_index = i_size >> PAGE_CACHE_SHIFT;
1515                if (index == end_index) {
1516                        nr = i_size & ~PAGE_CACHE_MASK;
1517                        if (nr <= offset) {
1518                                if (page)
1519                                        page_cache_release(page);
1520                                break;
1521                        }
1522                }
1523                nr -= offset;
1524
1525                if (page) {
1526                        /*
1527                         * If users can be writing to this page using arbitrary
1528                         * virtual addresses, take care about potential aliasing
1529                         * before reading the page on the kernel side.
1530                         */
1531                        if (mapping_writably_mapped(mapping))
1532                                flush_dcache_page(page);
1533                        /*
1534                         * Mark the page accessed if we read the beginning.
1535                         */
1536                        if (!offset)
1537                                mark_page_accessed(page);
1538                } else {
1539                        page = ZERO_PAGE(0);
1540                        page_cache_get(page);
1541                }
1542
1543                /*
1544                 * Ok, we have the page, and it's up-to-date, so
1545                 * now we can copy it to user space...
1546                 *
1547                 * The actor routine returns how many bytes were actually used..
1548                 * NOTE! This may not be the same as how much of a user buffer
1549                 * we filled up (we may be padding etc), so we can only update
1550                 * "pos" here (the actor routine has to update the user buffer
1551                 * pointers and the remaining count).
1552                 */
1553                ret = actor(desc, page, offset, nr);
1554                offset += ret;
1555                index += offset >> PAGE_CACHE_SHIFT;
1556                offset &= ~PAGE_CACHE_MASK;
1557
1558                page_cache_release(page);
1559                if (ret != nr || !desc->count)
1560                        break;
1561
1562                cond_resched();
1563        }
1564
1565        *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1566        file_accessed(filp);
1567}
1568
1569static ssize_t shmem_file_aio_read(struct kiocb *iocb,
1570                const struct iovec *iov, unsigned long nr_segs, loff_t pos)
1571{
1572        struct file *filp = iocb->ki_filp;
1573        ssize_t retval;
1574        unsigned long seg;
1575        size_t count;
1576        loff_t *ppos = &iocb->ki_pos;
1577
1578        retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1579        if (retval)
1580                return retval;
1581
1582        for (seg = 0; seg < nr_segs; seg++) {
1583                read_descriptor_t desc;
1584
1585                desc.written = 0;
1586                desc.arg.buf = iov[seg].iov_base;
1587                desc.count = iov[seg].iov_len;
1588                if (desc.count == 0)
1589                        continue;
1590                desc.error = 0;
1591                do_shmem_file_read(filp, ppos, &desc, file_read_actor);
1592                retval += desc.written;
1593                if (desc.error) {
1594                        retval = retval ?: desc.error;
1595                        break;
1596                }
1597                if (desc.count > 0)
1598                        break;
1599        }
1600        return retval;
1601}
1602
1603static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
1604                                struct pipe_inode_info *pipe, size_t len,
1605                                unsigned int flags)
1606{
1607        struct address_space *mapping = in->f_mapping;
1608        struct inode *inode = mapping->host;
1609        unsigned int loff, nr_pages, req_pages;
1610        struct page *pages[PIPE_DEF_BUFFERS];
1611        struct partial_page partial[PIPE_DEF_BUFFERS];
1612        struct page *page;
1613        pgoff_t index, end_index;
1614        loff_t isize, left;
1615        int error, page_nr;
1616        struct splice_pipe_desc spd = {
1617                .pages = pages,
1618                .partial = partial,
1619                .nr_pages_max = PIPE_DEF_BUFFERS,
1620                .flags = flags,
1621                .ops = &page_cache_pipe_buf_ops,
1622                .spd_release = spd_release_page,
1623        };
1624
1625        isize = i_size_read(inode);
1626        if (unlikely(*ppos >= isize))
1627                return 0;
1628
1629        left = isize - *ppos;
1630        if (unlikely(left < len))
1631                len = left;
1632
1633        if (splice_grow_spd(pipe, &spd))
1634                return -ENOMEM;
1635
1636        index = *ppos >> PAGE_CACHE_SHIFT;
1637        loff = *ppos & ~PAGE_CACHE_MASK;
1638        req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1639        nr_pages = min(req_pages, pipe->buffers);
1640
1641        spd.nr_pages = find_get_pages_contig(mapping, index,
1642                                                nr_pages, spd.pages);
1643        index += spd.nr_pages;
1644        error = 0;
1645
1646        while (spd.nr_pages < nr_pages) {
1647                error = shmem_getpage(inode, index, &page, SGP_CACHE, NULL);
1648                if (error)
1649                        break;
1650                unlock_page(page);
1651                spd.pages[spd.nr_pages++] = page;
1652                index++;
1653        }
1654
1655        index = *ppos >> PAGE_CACHE_SHIFT;
1656        nr_pages = spd.nr_pages;
1657        spd.nr_pages = 0;
1658
1659        for (page_nr = 0; page_nr < nr_pages; page_nr++) {
1660                unsigned int this_len;
1661
1662                if (!len)
1663                        break;
1664
1665                this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
1666                page = spd.pages[page_nr];
1667
1668                if (!PageUptodate(page) || page->mapping != mapping) {
1669                        error = shmem_getpage(inode, index, &page,
1670                                                        SGP_CACHE, NULL);
1671                        if (error)
1672                                break;
1673                        unlock_page(page);
1674                        page_cache_release(spd.pages[page_nr]);
1675                        spd.pages[page_nr] = page;
1676                }
1677
1678                isize = i_size_read(inode);
1679                end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1680                if (unlikely(!isize || index > end_index))
1681                        break;
1682
1683                if (end_index == index) {
1684                        unsigned int plen;
1685
1686                        plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1687                        if (plen <= loff)
1688                                break;
1689
1690                        this_len = min(this_len, plen - loff);
1691                        len = this_len;
1692                }
1693
1694                spd.partial[page_nr].offset = loff;
1695                spd.partial[page_nr].len = this_len;
1696                len -= this_len;
1697                loff = 0;
1698                spd.nr_pages++;
1699                index++;
1700        }
1701
1702        while (page_nr < nr_pages)
1703                page_cache_release(spd.pages[page_nr++]);
1704
1705        if (spd.nr_pages)
1706                error = splice_to_pipe(pipe, &spd);
1707
1708        splice_shrink_spd(&spd);
1709
1710        if (error > 0) {
1711                *ppos += error;
1712                file_accessed(in);
1713        }
1714        return error;
1715}
1716
1717/*
1718 * llseek SEEK_DATA or SEEK_HOLE through the radix_tree.
1719 */
1720static pgoff_t shmem_seek_hole_data(struct address_space *mapping,
1721                                    pgoff_t index, pgoff_t end, int whence)
1722{
1723        struct page *page;
1724        struct pagevec pvec;
1725        pgoff_t indices[PAGEVEC_SIZE];
1726        bool done = false;
1727        int i;
1728
1729        pagevec_init(&pvec, 0);
1730        pvec.nr = 1;            /* start small: we may be there already */
1731        while (!done) {
1732                pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
1733                                        pvec.nr, pvec.pages, indices);
1734                if (!pvec.nr) {
1735                        if (whence == SEEK_DATA)
1736                                index = end;
1737                        break;
1738                }
1739                for (i = 0; i < pvec.nr; i++, index++) {
1740                        if (index < indices[i]) {
1741                                if (whence == SEEK_HOLE) {
1742                                        done = true;
1743                                        break;
1744                                }
1745                                index = indices[i];
1746                        }
1747                        page = pvec.pages[i];
1748                        if (page && !radix_tree_exceptional_entry(page)) {
1749                                if (!PageUptodate(page))
1750                                        page = NULL;
1751                        }
1752                        if (index >= end ||
1753                            (page && whence == SEEK_DATA) ||
1754                            (!page && whence == SEEK_HOLE)) {
1755                                done = true;
1756                                break;
1757                        }
1758                }
1759                shmem_deswap_pagevec(&pvec);
1760                pagevec_release(&pvec);
1761                pvec.nr = PAGEVEC_SIZE;
1762                cond_resched();
1763        }
1764        return index;
1765}
1766
1767static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence)
1768{
1769        struct address_space *mapping = file->f_mapping;
1770        struct inode *inode = mapping->host;
1771        pgoff_t start, end;
1772        loff_t new_offset;
1773
1774        if (whence != SEEK_DATA && whence != SEEK_HOLE)
1775                return generic_file_llseek_size(file, offset, whence,
1776                                        MAX_LFS_FILESIZE, i_size_read(inode));
1777        mutex_lock(&inode->i_mutex);
1778        /* We're holding i_mutex so we can access i_size directly */
1779
1780        if (offset < 0)
1781                offset = -EINVAL;
1782        else if (offset >= inode->i_size)
1783                offset = -ENXIO;
1784        else {
1785                start = offset >> PAGE_CACHE_SHIFT;
1786                end = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1787                new_offset = shmem_seek_hole_data(mapping, start, end, whence);
1788                new_offset <<= PAGE_CACHE_SHIFT;
1789                if (new_offset > offset) {
1790                        if (new_offset < inode->i_size)
1791                                offset = new_offset;
1792                        else if (whence == SEEK_DATA)
1793                                offset = -ENXIO;
1794                        else
1795                                offset = inode->i_size;
1796                }
1797        }
1798
1799        if (offset >= 0 && offset != file->f_pos) {
1800                file->f_pos = offset;
1801                file->f_version = 0;
1802        }
1803        mutex_unlock(&inode->i_mutex);
1804        return offset;
1805}
1806
1807static long shmem_fallocate(struct file *file, int mode, loff_t offset,
1808                                                         loff_t len)
1809{
1810        struct inode *inode = file_inode(file);
1811        struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1812        struct shmem_falloc shmem_falloc;
1813        pgoff_t start, index, end;
1814        int error;
1815
1816        mutex_lock(&inode->i_mutex);
1817
1818        if (mode & FALLOC_FL_PUNCH_HOLE) {
1819                struct address_space *mapping = file->f_mapping;
1820                loff_t unmap_start = round_up(offset, PAGE_SIZE);
1821                loff_t unmap_end = round_down(offset + len, PAGE_SIZE) - 1;
1822
1823                if ((u64)unmap_end > (u64)unmap_start)
1824                        unmap_mapping_range(mapping, unmap_start,
1825                                            1 + unmap_end - unmap_start, 0);
1826                shmem_truncate_range(inode, offset, offset + len - 1);
1827                /* No need to unmap again: hole-punching leaves COWed pages */
1828                error = 0;
1829                goto out;
1830        }
1831
1832        /* We need to check rlimit even when FALLOC_FL_KEEP_SIZE */
1833        error = inode_newsize_ok(inode, offset + len);
1834        if (error)
1835                goto out;
1836
1837        start = offset >> PAGE_CACHE_SHIFT;
1838        end = (offset + len + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1839        /* Try to avoid a swapstorm if len is impossible to satisfy */
1840        if (sbinfo->max_blocks && end - start > sbinfo->max_blocks) {
1841                error = -ENOSPC;
1842                goto out;
1843        }
1844
1845        shmem_falloc.start = start;
1846        shmem_falloc.next  = start;
1847        shmem_falloc.nr_falloced = 0;
1848        shmem_falloc.nr_unswapped = 0;
1849        spin_lock(&inode->i_lock);
1850        inode->i_private = &shmem_falloc;
1851        spin_unlock(&inode->i_lock);
1852
1853        for (index = start; index < end; index++) {
1854                struct page *page;
1855
1856                /*
1857                 * Good, the fallocate(2) manpage permits EINTR: we may have
1858                 * been interrupted because we are using up too much memory.
1859                 */
1860                if (signal_pending(current))
1861                        error = -EINTR;
1862                else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
1863                        error = -ENOMEM;
1864                else
1865                        error = shmem_getpage(inode, index, &page, SGP_FALLOC,
1866                                                                        NULL);
1867                if (error) {
1868                        /* Remove the !PageUptodate pages we added */
1869                        shmem_undo_range(inode,
1870                                (loff_t)start << PAGE_CACHE_SHIFT,
1871                                (loff_t)index << PAGE_CACHE_SHIFT, true);
1872                        goto undone;
1873                }
1874
1875                /*
1876                 * Inform shmem_writepage() how far we have reached.
1877                 * No need for lock or barrier: we have the page lock.
1878                 */
1879                shmem_falloc.next++;
1880                if (!PageUptodate(page))
1881                        shmem_falloc.nr_falloced++;
1882
1883                /*
1884                 * If !PageUptodate, leave it that way so that freeable pages
1885                 * can be recognized if we need to rollback on error later.
1886                 * But set_page_dirty so that memory pressure will swap rather
1887                 * than free the pages we are allocating (and SGP_CACHE pages
1888                 * might still be clean: we now need to mark those dirty too).
1889                 */
1890                set_page_dirty(page);
1891                unlock_page(page);
1892                page_cache_release(page);
1893                cond_resched();
1894        }
1895
1896        if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
1897                i_size_write(inode, offset + len);
1898        inode->i_ctime = CURRENT_TIME;
1899undone:
1900        spin_lock(&inode->i_lock);
1901        inode->i_private = NULL;
1902        spin_unlock(&inode->i_lock);
1903out:
1904        mutex_unlock(&inode->i_mutex);
1905        return error;
1906}
1907
1908static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
1909{
1910        struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
1911
1912        buf->f_type = TMPFS_MAGIC;
1913        buf->f_bsize = PAGE_CACHE_SIZE;
1914        buf->f_namelen = NAME_MAX;
1915        if (sbinfo->max_blocks) {
1916                buf->f_blocks = sbinfo->max_blocks;
1917                buf->f_bavail =
1918                buf->f_bfree  = sbinfo->max_blocks -
1919                                percpu_counter_sum(&sbinfo->used_blocks);
1920        }
1921        if (sbinfo->max_inodes) {
1922                buf->f_files = sbinfo->max_inodes;
1923                buf->f_ffree = sbinfo->free_inodes;
1924        }
1925        /* else leave those fields 0 like simple_statfs */
1926        return 0;
1927}
1928
1929/*
1930 * File creation. Allocate an inode, and we're done..
1931 */
1932static int
1933shmem_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
1934{
1935        struct inode *inode;
1936        int error = -ENOSPC;
1937
1938        inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
1939        if (inode) {
1940                error = security_inode_init_security(inode, dir,
1941                                                     &dentry->d_name,
1942                                                     shmem_initxattrs, NULL);
1943                if (error) {
1944                        if (error != -EOPNOTSUPP) {
1945                                iput(inode);
1946                                return error;
1947                        }
1948                }
1949#ifdef CONFIG_TMPFS_POSIX_ACL
1950                error = generic_acl_init(inode, dir);
1951                if (error) {
1952                        iput(inode);
1953                        return error;
1954                }
1955#else
1956                error = 0;
1957#endif
1958                dir->i_size += BOGO_DIRENT_SIZE;
1959                dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1960                d_instantiate(dentry, inode);
1961                dget(dentry); /* Extra count - pin the dentry in core */
1962        }
1963        return error;
1964}
1965
1966static int shmem_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
1967{
1968        int error;
1969
1970        if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
1971                return error;
1972        inc_nlink(dir);
1973        return 0;
1974}
1975
1976static int shmem_create(struct inode *dir, struct dentry *dentry, umode_t mode,
1977                bool excl)
1978{
1979        return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
1980}
1981
1982/*
1983 * Link a file..
1984 */
1985static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
1986{
1987        struct inode *inode = old_dentry->d_inode;
1988        int ret;
1989
1990        /*
1991         * No ordinary (disk based) filesystem counts links as inodes;
1992         * but each new link needs a new dentry, pinning lowmem, and
1993         * tmpfs dentries cannot be pruned until they are unlinked.
1994         */
1995        ret = shmem_reserve_inode(inode->i_sb);
1996        if (ret)
1997                goto out;
1998
1999        dir->i_size += BOGO_DIRENT_SIZE;
2000        inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2001        inc_nlink(inode);
2002        ihold(inode);   /* New dentry reference */
2003        dget(dentry);           /* Extra pinning count for the created dentry */
2004        d_instantiate(dentry, inode);
2005out:
2006        return ret;
2007}
2008
2009static int shmem_unlink(struct inode *dir, struct dentry *dentry)
2010{
2011        struct inode *inode = dentry->d_inode;
2012
2013        if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
2014                shmem_free_inode(inode->i_sb);
2015
2016        dir->i_size -= BOGO_DIRENT_SIZE;
2017        inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2018        drop_nlink(inode);
2019        dput(dentry);   /* Undo the count from "create" - this does all the work */
2020        return 0;
2021}
2022
2023static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
2024{
2025        if (!simple_empty(dentry))
2026                return -ENOTEMPTY;
2027
2028        drop_nlink(dentry->d_inode);
2029        drop_nlink(dir);
2030        return shmem_unlink(dir, dentry);
2031}
2032
2033/*
2034 * The VFS layer already does all the dentry stuff for rename,
2035 * we just have to decrement the usage count for the target if
2036 * it exists so that the VFS layer correctly free's it when it
2037 * gets overwritten.
2038 */
2039static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
2040{
2041        struct inode *inode = old_dentry->d_inode;
2042        int they_are_dirs = S_ISDIR(inode->i_mode);
2043
2044        if (!simple_empty(new_dentry))
2045                return -ENOTEMPTY;
2046
2047        if (new_dentry->d_inode) {
2048                (void) shmem_unlink(new_dir, new_dentry);
2049                if (they_are_dirs)
2050                        drop_nlink(old_dir);
2051        } else if (they_are_dirs) {
2052                drop_nlink(old_dir);
2053                inc_nlink(new_dir);
2054        }
2055
2056        old_dir->i_size -= BOGO_DIRENT_SIZE;
2057        new_dir->i_size += BOGO_DIRENT_SIZE;
2058        old_dir->i_ctime = old_dir->i_mtime =
2059        new_dir->i_ctime = new_dir->i_mtime =
2060        inode->i_ctime = CURRENT_TIME;
2061        return 0;
2062}
2063
2064static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
2065{
2066        int error;
2067        int len;
2068        struct inode *inode;
2069        struct page *page;
2070        char *kaddr;
2071        struct shmem_inode_info *info;
2072
2073        len = strlen(symname) + 1;
2074        if (len > PAGE_CACHE_SIZE)
2075                return -ENAMETOOLONG;
2076
2077        inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0, VM_NORESERVE);
2078        if (!inode)
2079                return -ENOSPC;
2080
2081        error = security_inode_init_security(inode, dir, &dentry->d_name,
2082                                             shmem_initxattrs, NULL);
2083        if (error) {
2084                if (error != -EOPNOTSUPP) {
2085                        iput(inode);
2086                        return error;
2087                }
2088                error = 0;
2089        }
2090
2091        info = SHMEM_I(inode);
2092        inode->i_size = len-1;
2093        if (len <= SHORT_SYMLINK_LEN) {
2094                info->symlink = kmemdup(symname, len, GFP_KERNEL);
2095                if (!info->symlink) {
2096                        iput(inode);
2097                        return -ENOMEM;
2098                }
2099                inode->i_op = &shmem_short_symlink_operations;
2100        } else {
2101                error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
2102                if (error) {
2103                        iput(inode);
2104                        return error;
2105                }
2106                inode->i_mapping->a_ops = &shmem_aops;
2107                inode->i_op = &shmem_symlink_inode_operations;
2108                kaddr = kmap_atomic(page);
2109                memcpy(kaddr, symname, len);
2110                kunmap_atomic(kaddr);
2111                SetPageUptodate(page);
2112                set_page_dirty(page);
2113                unlock_page(page);
2114                page_cache_release(page);
2115        }
2116        dir->i_size += BOGO_DIRENT_SIZE;
2117        dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2118        d_instantiate(dentry, inode);
2119        dget(dentry);
2120        return 0;
2121}
2122
2123static void *shmem_follow_short_symlink(struct dentry *dentry, struct nameidata *nd)
2124{
2125        nd_set_link(nd, SHMEM_I(dentry->d_inode)->symlink);
2126        return NULL;
2127}
2128
2129static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
2130{
2131        struct page *page = NULL;
2132        int error = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
2133        nd_set_link(nd, error ? ERR_PTR(error) : kmap(page));
2134        if (page)
2135                unlock_page(page);
2136        return page;
2137}
2138
2139static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
2140{
2141        if (!IS_ERR(nd_get_link(nd))) {
2142                struct page *page = cookie;
2143                kunmap(page);
2144                mark_page_accessed(page);
2145                page_cache_release(page);
2146        }
2147}
2148
2149#ifdef CONFIG_TMPFS_XATTR
2150/*
2151 * Superblocks without xattr inode operations may get some security.* xattr
2152 * support from the LSM "for free". As soon as we have any other xattrs
2153 * like ACLs, we also need to implement the security.* handlers at
2154 * filesystem level, though.
2155 */
2156
2157/*
2158 * Callback for security_inode_init_security() for acquiring xattrs.
2159 */
2160static int shmem_initxattrs(struct inode *inode,
2161                            const struct xattr *xattr_array,
2162                            void *fs_info)
2163{
2164        struct shmem_inode_info *info = SHMEM_I(inode);
2165        const struct xattr *xattr;
2166        struct simple_xattr *new_xattr;
2167        size_t len;
2168
2169        for (xattr = xattr_array; xattr->name != NULL; xattr++) {
2170                new_xattr = simple_xattr_alloc(xattr->value, xattr->value_len);
2171                if (!new_xattr)
2172                        return -ENOMEM;
2173
2174                len = strlen(xattr->name) + 1;
2175                new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
2176                                          GFP_KERNEL);
2177                if (!new_xattr->name) {
2178                        kfree(new_xattr);
2179                        return -ENOMEM;
2180                }
2181
2182                memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
2183                       XATTR_SECURITY_PREFIX_LEN);
2184                memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
2185                       xattr->name, len);
2186
2187                simple_xattr_list_add(&info->xattrs, new_xattr);
2188        }
2189
2190        return 0;
2191}
2192
2193static const struct xattr_handler *shmem_xattr_handlers[] = {
2194#ifdef CONFIG_TMPFS_POSIX_ACL
2195        &generic_acl_access_handler,
2196        &generic_acl_default_handler,
2197#endif
2198        NULL
2199};
2200
2201static int shmem_xattr_validate(const char *name)
2202{
2203        struct { const char *prefix; size_t len; } arr[] = {
2204                { XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN },
2205                { XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN }
2206        };
2207        int i;
2208
2209        for (i = 0; i < ARRAY_SIZE(arr); i++) {
2210                size_t preflen = arr[i].len;
2211                if (strncmp(name, arr[i].prefix, preflen) == 0) {
2212                        if (!name[preflen])
2213                                return -EINVAL;
2214                        return 0;
2215                }
2216        }
2217        return -EOPNOTSUPP;
2218}
2219
2220static ssize_t shmem_getxattr(struct dentry *dentry, const char *name,
2221                              void *buffer, size_t size)
2222{
2223        struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2224        int err;
2225
2226        /*
2227         * If this is a request for a synthetic attribute in the system.*
2228         * namespace use the generic infrastructure to resolve a handler
2229         * for it via sb->s_xattr.
2230         */
2231        if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2232                return generic_getxattr(dentry, name, buffer, size);
2233
2234        err = shmem_xattr_validate(name);
2235        if (err)
2236                return err;
2237
2238        return simple_xattr_get(&info->xattrs, name, buffer, size);
2239}
2240
2241static int shmem_setxattr(struct dentry *dentry, const char *name,
2242                          const void *value, size_t size, int flags)
2243{
2244        struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2245        int err;
2246
2247        /*
2248         * If this is a request for a synthetic attribute in the system.*
2249         * namespace use the generic infrastructure to resolve a handler
2250         * for it via sb->s_xattr.
2251         */
2252        if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2253                return generic_setxattr(dentry, name, value, size, flags);
2254
2255        err = shmem_xattr_validate(name);
2256        if (err)
2257                return err;
2258
2259        return simple_xattr_set(&info->xattrs, name, value, size, flags);
2260}
2261
2262static int shmem_removexattr(struct dentry *dentry, const char *name)
2263{
2264        struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2265        int err;
2266
2267        /*
2268         * If this is a request for a synthetic attribute in the system.*
2269         * namespace use the generic infrastructure to resolve a handler
2270         * for it via sb->s_xattr.
2271         */
2272        if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2273                return generic_removexattr(dentry, name);
2274
2275        err = shmem_xattr_validate(name);
2276        if (err)
2277                return err;
2278
2279        return simple_xattr_remove(&info->xattrs, name);
2280}
2281
2282static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
2283{
2284        struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2285        return simple_xattr_list(&info->xattrs, buffer, size);
2286}
2287#endif /* CONFIG_TMPFS_XATTR */
2288
2289static const struct inode_operations shmem_short_symlink_operations = {
2290        .readlink       = generic_readlink,
2291        .follow_link    = shmem_follow_short_symlink,
2292#ifdef CONFIG_TMPFS_XATTR
2293        .setxattr       = shmem_setxattr,
2294        .getxattr       = shmem_getxattr,
2295        .listxattr      = shmem_listxattr,
2296        .removexattr    = shmem_removexattr,
2297#endif
2298};
2299
2300static const struct inode_operations shmem_symlink_inode_operations = {
2301        .readlink       = generic_readlink,
2302        .follow_link    = shmem_follow_link,
2303        .put_link       = shmem_put_link,
2304#ifdef CONFIG_TMPFS_XATTR
2305        .setxattr       = shmem_setxattr,
2306        .getxattr       = shmem_getxattr,
2307        .listxattr      = shmem_listxattr,
2308        .removexattr    = shmem_removexattr,
2309#endif
2310};
2311
2312static struct dentry *shmem_get_parent(struct dentry *child)
2313{
2314        return ERR_PTR(-ESTALE);
2315}
2316
2317static int shmem_match(struct inode *ino, void *vfh)
2318{
2319        __u32 *fh = vfh;
2320        __u64 inum = fh[2];
2321        inum = (inum << 32) | fh[1];
2322        return ino->i_ino == inum && fh[0] == ino->i_generation;
2323}
2324
2325static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
2326                struct fid *fid, int fh_len, int fh_type)
2327{
2328        struct inode *inode;
2329        struct dentry *dentry = NULL;
2330        u64 inum;
2331
2332        if (fh_len < 3)
2333                return NULL;
2334
2335        inum = fid->raw[2];
2336        inum = (inum << 32) | fid->raw[1];
2337
2338        inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
2339                        shmem_match, fid->raw);
2340        if (inode) {
2341                dentry = d_find_alias(inode);
2342                iput(inode);
2343        }
2344
2345        return dentry;
2346}
2347
2348static int shmem_encode_fh(struct inode *inode, __u32 *fh, int *len,
2349                                struct inode *parent)
2350{
2351        if (*len < 3) {
2352                *len = 3;
2353                return FILEID_INVALID;
2354        }
2355
2356        if (inode_unhashed(inode)) {
2357                /* Unfortunately insert_inode_hash is not idempotent,
2358                 * so as we hash inodes here rather than at creation
2359                 * time, we need a lock to ensure we only try
2360                 * to do it once
2361                 */
2362                static DEFINE_SPINLOCK(lock);
2363                spin_lock(&lock);
2364                if (inode_unhashed(inode))
2365                        __insert_inode_hash(inode,
2366                                            inode->i_ino + inode->i_generation);
2367                spin_unlock(&lock);
2368        }
2369
2370        fh[0] = inode->i_generation;
2371        fh[1] = inode->i_ino;
2372        fh[2] = ((__u64)inode->i_ino) >> 32;
2373
2374        *len = 3;
2375        return 1;
2376}
2377
2378static const struct export_operations shmem_export_ops = {
2379        .get_parent     = shmem_get_parent,
2380        .encode_fh      = shmem_encode_fh,
2381        .fh_to_dentry   = shmem_fh_to_dentry,
2382};
2383
2384static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
2385                               bool remount)
2386{
2387        char *this_char, *value, *rest;
2388        struct mempolicy *mpol = NULL;
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                        goto error;
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                        mpol_put(mpol);
2467                        mpol = NULL;
2468                        if (mpol_parse_str(value, &mpol))
2469                                goto bad_val;
2470                } else {
2471                        printk(KERN_ERR "tmpfs: Bad mount option %s\n",
2472                               this_char);
2473                        goto error;
2474                }
2475        }
2476        sbinfo->mpol = mpol;
2477        return 0;
2478
2479bad_val:
2480        printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
2481               value, this_char);
2482error:
2483        mpol_put(mpol);
2484        return 1;
2485
2486}
2487
2488static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2489{
2490        struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2491        struct shmem_sb_info config = *sbinfo;
2492        unsigned long inodes;
2493        int error = -EINVAL;
2494
2495        config.mpol = NULL;
2496        if (shmem_parse_options(data, &config, true))
2497                return error;
2498
2499        spin_lock(&sbinfo->stat_lock);
2500        inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2501        if (percpu_counter_compare(&sbinfo->used_blocks, config.max_blocks) > 0)
2502                goto out;
2503        if (config.max_inodes < inodes)
2504                goto out;
2505        /*
2506         * Those tests disallow limited->unlimited while any are in use;
2507         * but we must separately disallow unlimited->limited, because
2508         * in that case we have no record of how much is already in use.
2509         */
2510        if (config.max_blocks && !sbinfo->max_blocks)
2511                goto out;
2512        if (config.max_inodes && !sbinfo->max_inodes)
2513                goto out;
2514
2515        error = 0;
2516        sbinfo->max_blocks  = config.max_blocks;
2517        sbinfo->max_inodes  = config.max_inodes;
2518        sbinfo->free_inodes = config.max_inodes - inodes;
2519
2520        /*
2521         * Preserve previous mempolicy unless mpol remount option was specified.
2522         */
2523        if (config.mpol) {
2524                mpol_put(sbinfo->mpol);
2525                sbinfo->mpol = config.mpol;     /* transfers initial ref */
2526        }
2527out:
2528        spin_unlock(&sbinfo->stat_lock);
2529        return error;
2530}
2531
2532static int shmem_show_options(struct seq_file *seq, struct dentry *root)
2533{
2534        struct shmem_sb_info *sbinfo = SHMEM_SB(root->d_sb);
2535
2536        if (sbinfo->max_blocks != shmem_default_max_blocks())
2537                seq_printf(seq, ",size=%luk",
2538                        sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10));
2539        if (sbinfo->max_inodes != shmem_default_max_inodes())
2540                seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
2541        if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
2542                seq_printf(seq, ",mode=%03ho", sbinfo->mode);
2543        if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID))
2544                seq_printf(seq, ",uid=%u",
2545                                from_kuid_munged(&init_user_ns, sbinfo->uid));
2546        if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
2547                seq_printf(seq, ",gid=%u",
2548                                from_kgid_munged(&init_user_ns, sbinfo->gid));
2549        shmem_show_mpol(seq, sbinfo->mpol);
2550        return 0;
2551}
2552#endif /* CONFIG_TMPFS */
2553
2554static void shmem_put_super(struct super_block *sb)
2555{
2556        struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2557
2558        percpu_counter_destroy(&sbinfo->used_blocks);
2559        mpol_put(sbinfo->mpol);
2560        kfree(sbinfo);
2561        sb->s_fs_info = NULL;
2562}
2563
2564int shmem_fill_super(struct super_block *sb, void *data, int silent)
2565{
2566        struct inode *inode;
2567        struct shmem_sb_info *sbinfo;
2568        int err = -ENOMEM;
2569
2570        /* Round up to L1_CACHE_BYTES to resist false sharing */
2571        sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
2572                                L1_CACHE_BYTES), GFP_KERNEL);
2573        if (!sbinfo)
2574                return -ENOMEM;
2575
2576        sbinfo->mode = S_IRWXUGO | S_ISVTX;
2577        sbinfo->uid = current_fsuid();
2578        sbinfo->gid = current_fsgid();
2579        sb->s_fs_info = sbinfo;
2580
2581#ifdef CONFIG_TMPFS
2582        /*
2583         * Per default we only allow half of the physical ram per
2584         * tmpfs instance, limiting inodes to one per page of lowmem;
2585         * but the internal instance is left unlimited.
2586         */
2587        if (!(sb->s_flags & MS_NOUSER)) {
2588                sbinfo->max_blocks = shmem_default_max_blocks();
2589                sbinfo->max_inodes = shmem_default_max_inodes();
2590                if (shmem_parse_options(data, sbinfo, false)) {
2591                        err = -EINVAL;
2592                        goto failed;
2593                }
2594        }
2595        sb->s_export_op = &shmem_export_ops;
2596        sb->s_flags |= MS_NOSEC;
2597#else
2598        sb->s_flags |= MS_NOUSER;
2599#endif
2600
2601        spin_lock_init(&sbinfo->stat_lock);
2602        if (percpu_counter_init(&sbinfo->used_blocks, 0))
2603                goto failed;
2604        sbinfo->free_inodes = sbinfo->max_inodes;
2605
2606        sb->s_maxbytes = MAX_LFS_FILESIZE;
2607        sb->s_blocksize = PAGE_CACHE_SIZE;
2608        sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
2609        sb->s_magic = TMPFS_MAGIC;
2610        sb->s_op = &shmem_ops;
2611        sb->s_time_gran = 1;
2612#ifdef CONFIG_TMPFS_XATTR
2613        sb->s_xattr = shmem_xattr_handlers;
2614#endif
2615#ifdef CONFIG_TMPFS_POSIX_ACL
2616        sb->s_flags |= MS_POSIXACL;
2617#endif
2618
2619        inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
2620        if (!inode)
2621                goto failed;
2622        inode->i_uid = sbinfo->uid;
2623        inode->i_gid = sbinfo->gid;
2624        sb->s_root = d_make_root(inode);
2625        if (!sb->s_root)
2626                goto failed;
2627        return 0;
2628
2629failed:
2630        shmem_put_super(sb);
2631        return err;
2632}
2633
2634static struct kmem_cache *shmem_inode_cachep;
2635
2636static struct inode *shmem_alloc_inode(struct super_block *sb)
2637{
2638        struct shmem_inode_info *info;
2639        info = kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
2640        if (!info)
2641                return NULL;
2642        return &info->vfs_inode;
2643}
2644
2645static void shmem_destroy_callback(struct rcu_head *head)
2646{
2647        struct inode *inode = container_of(head, struct inode, i_rcu);
2648        kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2649}
2650
2651static void shmem_destroy_inode(struct inode *inode)
2652{
2653        if (S_ISREG(inode->i_mode))
2654                mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2655        call_rcu(&inode->i_rcu, shmem_destroy_callback);
2656}
2657
2658static void shmem_init_inode(void *foo)
2659{
2660        struct shmem_inode_info *info = foo;
2661        inode_init_once(&info->vfs_inode);
2662}
2663
2664static int shmem_init_inodecache(void)
2665{
2666        shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
2667                                sizeof(struct shmem_inode_info),
2668                                0, SLAB_PANIC, shmem_init_inode);
2669        return 0;
2670}
2671
2672static void shmem_destroy_inodecache(void)
2673{
2674        kmem_cache_destroy(shmem_inode_cachep);
2675}
2676
2677static const struct address_space_operations shmem_aops = {
2678        .writepage      = shmem_writepage,
2679        .set_page_dirty = __set_page_dirty_no_writeback,
2680#ifdef CONFIG_TMPFS
2681        .write_begin    = shmem_write_begin,
2682        .write_end      = shmem_write_end,
2683#endif
2684        .migratepage    = migrate_page,
2685        .error_remove_page = generic_error_remove_page,
2686};
2687
2688static const struct file_operations shmem_file_operations = {
2689        .mmap           = shmem_mmap,
2690#ifdef CONFIG_TMPFS
2691        .llseek         = shmem_file_llseek,
2692        .read           = do_sync_read,
2693        .write          = do_sync_write,
2694        .aio_read       = shmem_file_aio_read,
2695        .aio_write      = generic_file_aio_write,
2696        .fsync          = noop_fsync,
2697        .splice_read    = shmem_file_splice_read,
2698        .splice_write   = generic_file_splice_write,
2699        .fallocate      = shmem_fallocate,
2700#endif
2701};
2702
2703static const struct inode_operations shmem_inode_operations = {
2704        .setattr        = shmem_setattr,
2705#ifdef CONFIG_TMPFS_XATTR
2706        .setxattr       = shmem_setxattr,
2707        .getxattr       = shmem_getxattr,
2708        .listxattr      = shmem_listxattr,
2709        .removexattr    = shmem_removexattr,
2710#endif
2711};
2712
2713static const struct inode_operations shmem_dir_inode_operations = {
2714#ifdef CONFIG_TMPFS
2715        .create         = shmem_create,
2716        .lookup         = simple_lookup,
2717        .link           = shmem_link,
2718        .unlink         = shmem_unlink,
2719        .symlink        = shmem_symlink,
2720        .mkdir          = shmem_mkdir,
2721        .rmdir          = shmem_rmdir,
2722        .mknod          = shmem_mknod,
2723        .rename         = shmem_rename,
2724#endif
2725#ifdef CONFIG_TMPFS_XATTR
2726        .setxattr       = shmem_setxattr,
2727        .getxattr       = shmem_getxattr,
2728        .listxattr      = shmem_listxattr,
2729        .removexattr    = shmem_removexattr,
2730#endif
2731#ifdef CONFIG_TMPFS_POSIX_ACL
2732        .setattr        = shmem_setattr,
2733#endif
2734};
2735
2736static const struct inode_operations shmem_special_inode_operations = {
2737#ifdef CONFIG_TMPFS_XATTR
2738        .setxattr       = shmem_setxattr,
2739        .getxattr       = shmem_getxattr,
2740        .listxattr      = shmem_listxattr,
2741        .removexattr    = shmem_removexattr,
2742#endif
2743#ifdef CONFIG_TMPFS_POSIX_ACL
2744        .setattr        = shmem_setattr,
2745#endif
2746};
2747
2748static const struct super_operations shmem_ops = {
2749        .alloc_inode    = shmem_alloc_inode,
2750        .destroy_inode  = shmem_destroy_inode,
2751#ifdef CONFIG_TMPFS
2752        .statfs         = shmem_statfs,
2753        .remount_fs     = shmem_remount_fs,
2754        .show_options   = shmem_show_options,
2755#endif
2756        .evict_inode    = shmem_evict_inode,
2757        .drop_inode     = generic_delete_inode,
2758        .put_super      = shmem_put_super,
2759};
2760
2761static const struct vm_operations_struct shmem_vm_ops = {
2762        .fault          = shmem_fault,
2763#ifdef CONFIG_NUMA
2764        .set_policy     = shmem_set_policy,
2765        .get_policy     = shmem_get_policy,
2766#endif
2767        .remap_pages    = generic_file_remap_pages,
2768};
2769
2770static struct dentry *shmem_mount(struct file_system_type *fs_type,
2771        int flags, const char *dev_name, void *data)
2772{
2773        return mount_nodev(fs_type, flags, data, shmem_fill_super);
2774}
2775
2776static struct file_system_type shmem_fs_type = {
2777        .owner          = THIS_MODULE,
2778        .name           = "tmpfs",
2779        .mount          = shmem_mount,
2780        .kill_sb        = kill_litter_super,
2781        .fs_flags       = FS_USERNS_MOUNT,
2782};
2783
2784int __init shmem_init(void)
2785{
2786        int error;
2787
2788        error = bdi_init(&shmem_backing_dev_info);
2789        if (error)
2790                goto out4;
2791
2792        error = shmem_init_inodecache();
2793        if (error)
2794                goto out3;
2795
2796        error = register_filesystem(&shmem_fs_type);
2797        if (error) {
2798                printk(KERN_ERR "Could not register tmpfs\n");
2799                goto out2;
2800        }
2801
2802        shm_mnt = vfs_kern_mount(&shmem_fs_type, MS_NOUSER,
2803                                 shmem_fs_type.name, NULL);
2804        if (IS_ERR(shm_mnt)) {
2805                error = PTR_ERR(shm_mnt);
2806                printk(KERN_ERR "Could not kern_mount tmpfs\n");
2807                goto out1;
2808        }
2809        return 0;
2810
2811out1:
2812        unregister_filesystem(&shmem_fs_type);
2813out2:
2814        shmem_destroy_inodecache();
2815out3:
2816        bdi_destroy(&shmem_backing_dev_info);
2817out4:
2818        shm_mnt = ERR_PTR(error);
2819        return error;
2820}
2821
2822#else /* !CONFIG_SHMEM */
2823
2824/*
2825 * tiny-shmem: simple shmemfs and tmpfs using ramfs code
2826 *
2827 * This is intended for small system where the benefits of the full
2828 * shmem code (swap-backed and resource-limited) are outweighed by
2829 * their complexity. On systems without swap this code should be
2830 * effectively equivalent, but much lighter weight.
2831 */
2832
2833#include <linux/ramfs.h>
2834
2835static struct file_system_type shmem_fs_type = {
2836        .name           = "tmpfs",
2837        .mount          = ramfs_mount,
2838        .kill_sb        = kill_litter_super,
2839        .fs_flags       = FS_USERNS_MOUNT,
2840};
2841
2842int __init shmem_init(void)
2843{
2844        BUG_ON(register_filesystem(&shmem_fs_type) != 0);
2845
2846        shm_mnt = kern_mount(&shmem_fs_type);
2847        BUG_ON(IS_ERR(shm_mnt));
2848
2849        return 0;
2850}
2851
2852int shmem_unuse(swp_entry_t swap, struct page *page)
2853{
2854        return 0;
2855}
2856
2857int shmem_lock(struct file *file, int lock, struct user_struct *user)
2858{
2859        return 0;
2860}
2861
2862void shmem_unlock_mapping(struct address_space *mapping)
2863{
2864}
2865
2866void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
2867{
2868        truncate_inode_pages_range(inode->i_mapping, lstart, lend);
2869}
2870EXPORT_SYMBOL_GPL(shmem_truncate_range);
2871
2872#define shmem_vm_ops                            generic_file_vm_ops
2873#define shmem_file_operations                   ramfs_file_operations
2874#define shmem_get_inode(sb, dir, mode, dev, flags)      ramfs_get_inode(sb, dir, mode, dev)
2875#define shmem_acct_size(flags, size)            0
2876#define shmem_unacct_size(flags, size)          do {} while (0)
2877
2878#endif /* CONFIG_SHMEM */
2879
2880/* common code */
2881
2882static char *shmem_dname(struct dentry *dentry, char *buffer, int buflen)
2883{
2884        return dynamic_dname(dentry, buffer, buflen, "/%s (deleted)",
2885                                dentry->d_name.name);
2886}
2887
2888static struct dentry_operations anon_ops = {
2889        .d_dname = shmem_dname
2890};
2891
2892/**
2893 * shmem_file_setup - get an unlinked file living in tmpfs
2894 * @name: name for dentry (to be seen in /proc/<pid>/maps
2895 * @size: size to be set for the file
2896 * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
2897 */
2898struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
2899{
2900        struct file *res;
2901        struct inode *inode;
2902        struct path path;
2903        struct super_block *sb;
2904        struct qstr this;
2905
2906        if (IS_ERR(shm_mnt))
2907                return ERR_CAST(shm_mnt);
2908
2909        if (size < 0 || size > MAX_LFS_FILESIZE)
2910                return ERR_PTR(-EINVAL);
2911
2912        if (shmem_acct_size(flags, size))
2913                return ERR_PTR(-ENOMEM);
2914
2915        res = ERR_PTR(-ENOMEM);
2916        this.name = name;
2917        this.len = strlen(name);
2918        this.hash = 0; /* will go */
2919        sb = shm_mnt->mnt_sb;
2920        path.dentry = d_alloc_pseudo(sb, &this);
2921        if (!path.dentry)
2922                goto put_memory;
2923        d_set_d_op(path.dentry, &anon_ops);
2924        path.mnt = mntget(shm_mnt);
2925
2926        res = ERR_PTR(-ENOSPC);
2927        inode = shmem_get_inode(sb, NULL, S_IFREG | S_IRWXUGO, 0, flags);
2928        if (!inode)
2929                goto put_dentry;
2930
2931        d_instantiate(path.dentry, inode);
2932        inode->i_size = size;
2933        clear_nlink(inode);     /* It is unlinked */
2934#ifndef CONFIG_MMU
2935        res = ERR_PTR(ramfs_nommu_expand_for_mapping(inode, size));
2936        if (IS_ERR(res))
2937                goto put_dentry;
2938#endif
2939
2940        res = alloc_file(&path, FMODE_WRITE | FMODE_READ,
2941                  &shmem_file_operations);
2942        if (IS_ERR(res))
2943                goto put_dentry;
2944
2945        return res;
2946
2947put_dentry:
2948        path_put(&path);
2949put_memory:
2950        shmem_unacct_size(flags, size);
2951        return res;
2952}
2953EXPORT_SYMBOL_GPL(shmem_file_setup);
2954
2955/**
2956 * shmem_zero_setup - setup a shared anonymous mapping
2957 * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
2958 */
2959int shmem_zero_setup(struct vm_area_struct *vma)
2960{
2961        struct file *file;
2962        loff_t size = vma->vm_end - vma->vm_start;
2963
2964        file = shmem_file_setup("dev/zero", size, vma->vm_flags);
2965        if (IS_ERR(file))
2966                return PTR_ERR(file);
2967
2968        if (vma->vm_file)
2969                fput(vma->vm_file);
2970        vma->vm_file = file;
2971        vma->vm_ops = &shmem_vm_ops;
2972        return 0;
2973}
2974
2975/**
2976 * shmem_read_mapping_page_gfp - read into page cache, using specified page allocation flags.
2977 * @mapping:    the page's address_space
2978 * @index:      the page index
2979 * @gfp:        the page allocator flags to use if allocating
2980 *
2981 * This behaves as a tmpfs "read_cache_page_gfp(mapping, index, gfp)",
2982 * with any new page allocations done using the specified allocation flags.
2983 * But read_cache_page_gfp() uses the ->readpage() method: which does not
2984 * suit tmpfs, since it may have pages in swapcache, and needs to find those
2985 * for itself; although drivers/gpu/drm i915 and ttm rely upon this support.
2986 *
2987 * i915_gem_object_get_pages_gtt() mixes __GFP_NORETRY | __GFP_NOWARN in
2988 * with the mapping_gfp_mask(), to avoid OOMing the machine unnecessarily.
2989 */
2990struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
2991                                         pgoff_t index, gfp_t gfp)
2992{
2993#ifdef CONFIG_SHMEM
2994        struct inode *inode = mapping->host;
2995        struct page *page;
2996        int error;
2997
2998        BUG_ON(mapping->a_ops != &shmem_aops);
2999        error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE, gfp, NULL);
3000        if (error)
3001                page = ERR_PTR(error);
3002        else
3003                unlock_page(page);
3004        return page;
3005#else
3006        /*
3007         * The tiny !SHMEM case uses ramfs without swap
3008         */
3009        return read_cache_page_gfp(mapping, index, gfp);
3010#endif
3011}
3012EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);
3013
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