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/ramfs.h>
  29#include <linux/pagemap.h>
  30#include <linux/file.h>
  31#include <linux/mm.h>
  32#include <linux/export.h>
  33#include <linux/swap.h>
  34#include <linux/aio.h>
  35
  36static struct vfsmount *shm_mnt;
  37
  38#ifdef CONFIG_SHMEM
  39/*
  40 * This virtual memory filesystem is heavily based on the ramfs. It
  41 * extends ramfs by the ability to use swap and honor resource limits
  42 * which makes it a completely usable filesystem.
  43 */
  44
  45#include <linux/xattr.h>
  46#include <linux/exportfs.h>
  47#include <linux/posix_acl.h>
  48#include <linux/generic_acl.h>
  49#include <linux/mman.h>
  50#include <linux/string.h>
  51#include <linux/slab.h>
  52#include <linux/backing-dev.h>
  53#include <linux/shmem_fs.h>
  54#include <linux/writeback.h>
  55#include <linux/blkdev.h>
  56#include <linux/pagevec.h>
  57#include <linux/percpu_counter.h>
  58#include <linux/falloc.h>
  59#include <linux/splice.h>
  60#include <linux/security.h>
  61#include <linux/swapops.h>
  62#include <linux/mempolicy.h>
  63#include <linux/namei.h>
  64#include <linux/ctype.h>
  65#include <linux/migrate.h>
  66#include <linux/highmem.h>
  67#include <linux/seq_file.h>
  68#include <linux/magic.h>
  69
  70#include <asm/uaccess.h>
  71#include <asm/pgtable.h>
  72
  73#define BLOCKS_PER_PAGE  (PAGE_CACHE_SIZE/512)
  74#define VM_ACCT(size)    (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
  75
  76/* Pretend that each entry is of this size in directory's i_size */
  77#define BOGO_DIRENT_SIZE 20
  78
  79/* Symlink up to this size is kmalloc'ed instead of using a swappable page */
  80#define SHORT_SYMLINK_LEN 128
  81
  82/*
  83 * shmem_fallocate and shmem_writepage communicate via inode->i_private
  84 * (with i_mutex making sure that it has only one user at a time):
  85 * we would prefer not to enlarge the shmem inode just for that.
  86 */
  87struct shmem_falloc {
  88        pgoff_t start;          /* start of range currently being fallocated */
  89        pgoff_t next;           /* the next page offset to be fallocated */
  90        pgoff_t nr_falloced;    /* how many new pages have been fallocated */
  91        pgoff_t nr_unswapped;   /* how often writepage refused to swap out */
  92};
  93
  94/* Flag allocation requirements to shmem_getpage */
  95enum sgp_type {
  96        SGP_READ,       /* don't exceed i_size, don't allocate page */
  97        SGP_CACHE,      /* don't exceed i_size, may allocate page */
  98        SGP_DIRTY,      /* like SGP_CACHE, but set new page dirty */
  99        SGP_WRITE,      /* may exceed i_size, may allocate !Uptodate page */
 100        SGP_FALLOC,     /* like SGP_WRITE, but make existing page Uptodate */
 101};
 102
 103#ifdef CONFIG_TMPFS
 104static unsigned long shmem_default_max_blocks(void)
 105{
 106        return totalram_pages / 2;
 107}
 108
 109static unsigned long shmem_default_max_inodes(void)
 110{
 111        return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
 112}
 113#endif
 114
 115static bool shmem_should_replace_page(struct page *page, gfp_t gfp);
 116static int shmem_replace_page(struct page **pagep, gfp_t gfp,
 117                                struct shmem_inode_info *info, pgoff_t index);
 118static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
 119        struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type);
 120
 121static inline int shmem_getpage(struct inode *inode, pgoff_t index,
 122        struct page **pagep, enum sgp_type sgp, int *fault_type)
 123{
 124        return shmem_getpage_gfp(inode, index, pagep, sgp,
 125                        mapping_gfp_mask(inode->i_mapping), fault_type);
 126}
 127
 128static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
 129{
 130        return sb->s_fs_info;
 131}
 132
 133/*
 134 * shmem_file_setup pre-accounts the whole fixed size of a VM object,
 135 * for shared memory and for shared anonymous (/dev/zero) mappings
 136 * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
 137 * consistent with the pre-accounting of private mappings ...
 138 */
 139static inline int shmem_acct_size(unsigned long flags, loff_t size)
 140{
 141        return (flags & VM_NORESERVE) ?
 142                0 : security_vm_enough_memory_mm(current->mm, VM_ACCT(size));
 143}
 144
 145static inline void shmem_unacct_size(unsigned long flags, loff_t size)
 146{
 147        if (!(flags & VM_NORESERVE))
 148                vm_unacct_memory(VM_ACCT(size));
 149}
 150
 151/*
 152 * ... whereas tmpfs objects are accounted incrementally as
 153 * pages are allocated, in order to allow huge sparse files.
 154 * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
 155 * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
 156 */
 157static inline int shmem_acct_block(unsigned long flags)
 158{
 159        return (flags & VM_NORESERVE) ?
 160                security_vm_enough_memory_mm(current->mm, VM_ACCT(PAGE_CACHE_SIZE)) : 0;
 161}
 162
 163static inline void shmem_unacct_blocks(unsigned long flags, long pages)
 164{
 165        if (flags & VM_NORESERVE)
 166                vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
 167}
 168
 169static const struct super_operations shmem_ops;
 170static const struct address_space_operations shmem_aops;
 171static const struct file_operations shmem_file_operations;
 172static const struct inode_operations shmem_inode_operations;
 173static const struct inode_operations shmem_dir_inode_operations;
 174static const struct inode_operations shmem_special_inode_operations;
 175static const struct vm_operations_struct shmem_vm_ops;
 176
 177static struct backing_dev_info shmem_backing_dev_info  __read_mostly = {
 178        .ra_pages       = 0,    /* No readahead */
 179        .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
 180};
 181
 182static LIST_HEAD(shmem_swaplist);
 183static DEFINE_MUTEX(shmem_swaplist_mutex);
 184
 185static int shmem_reserve_inode(struct super_block *sb)
 186{
 187        struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
 188        if (sbinfo->max_inodes) {
 189                spin_lock(&sbinfo->stat_lock);
 190                if (!sbinfo->free_inodes) {
 191                        spin_unlock(&sbinfo->stat_lock);
 192                        return -ENOSPC;
 193                }
 194                sbinfo->free_inodes--;
 195                spin_unlock(&sbinfo->stat_lock);
 196        }
 197        return 0;
 198}
 199
 200static void shmem_free_inode(struct super_block *sb)
 201{
 202        struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
 203        if (sbinfo->max_inodes) {
 204                spin_lock(&sbinfo->stat_lock);
 205                sbinfo->free_inodes++;
 206                spin_unlock(&sbinfo->stat_lock);
 207        }
 208}
 209
 210/**
 211 * shmem_recalc_inode - recalculate the block usage of an inode
 212 * @inode: inode to recalc
 213 *
 214 * We have to calculate the free blocks since the mm can drop
 215 * undirtied hole pages behind our back.
 216 *
 217 * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
 218 * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
 219 *
 220 * It has to be called with the spinlock held.
 221 */
 222static void shmem_recalc_inode(struct inode *inode)
 223{
 224        struct shmem_inode_info *info = SHMEM_I(inode);
 225        long freed;
 226
 227        freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
 228        if (freed > 0) {
 229                struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 230                if (sbinfo->max_blocks)
 231                        percpu_counter_add(&sbinfo->used_blocks, -freed);
 232                info->alloced -= freed;
 233                inode->i_blocks -= freed * BLOCKS_PER_PAGE;
 234                shmem_unacct_blocks(info->flags, freed);
 235        }
 236}
 237
 238/*
 239 * Replace item expected in radix tree by a new item, while holding tree lock.
 240 */
 241static int shmem_radix_tree_replace(struct address_space *mapping,
 242                        pgoff_t index, void *expected, void *replacement)
 243{
 244        void **pslot;
 245        void *item = NULL;
 246
 247        VM_BUG_ON(!expected);
 248        pslot = radix_tree_lookup_slot(&mapping->page_tree, index);
 249        if (pslot)
 250                item = radix_tree_deref_slot_protected(pslot,
 251                                                        &mapping->tree_lock);
 252        if (item != expected)
 253                return -ENOENT;
 254        if (replacement)
 255                radix_tree_replace_slot(pslot, replacement);
 256        else
 257                radix_tree_delete(&mapping->page_tree, index);
 258        return 0;
 259}
 260
 261/*
 262 * Sometimes, before we decide whether to proceed or to fail, we must check
 263 * that an entry was not already brought back from swap by a racing thread.
 264 *
 265 * Checking page is not enough: by the time a SwapCache page is locked, it
 266 * might be reused, and again be SwapCache, using the same swap as before.
 267 */
 268static bool shmem_confirm_swap(struct address_space *mapping,
 269                               pgoff_t index, swp_entry_t swap)
 270{
 271        void *item;
 272
 273        rcu_read_lock();
 274        item = radix_tree_lookup(&mapping->page_tree, index);
 275        rcu_read_unlock();
 276        return item == swp_to_radix_entry(swap);
 277}
 278
 279/*
 280 * Like add_to_page_cache_locked, but error if expected item has gone.
 281 */
 282static int shmem_add_to_page_cache(struct page *page,
 283                                   struct address_space *mapping,
 284                                   pgoff_t index, gfp_t gfp, void *expected)
 285{
 286        int error;
 287
 288        VM_BUG_ON(!PageLocked(page));
 289        VM_BUG_ON(!PageSwapBacked(page));
 290
 291        page_cache_get(page);
 292        page->mapping = mapping;
 293        page->index = index;
 294
 295        spin_lock_irq(&mapping->tree_lock);
 296        if (!expected)
 297                error = radix_tree_insert(&mapping->page_tree, index, page);
 298        else
 299                error = shmem_radix_tree_replace(mapping, index, expected,
 300                                                                 page);
 301        if (!error) {
 302                mapping->nrpages++;
 303                __inc_zone_page_state(page, NR_FILE_PAGES);
 304                __inc_zone_page_state(page, NR_SHMEM);
 305                spin_unlock_irq(&mapping->tree_lock);
 306        } else {
 307                page->mapping = NULL;
 308                spin_unlock_irq(&mapping->tree_lock);
 309                page_cache_release(page);
 310        }
 311        return error;
 312}
 313
 314/*
 315 * Like delete_from_page_cache, but substitutes swap for page.
 316 */
 317static void shmem_delete_from_page_cache(struct page *page, void *radswap)
 318{
 319        struct address_space *mapping = page->mapping;
 320        int error;
 321
 322        spin_lock_irq(&mapping->tree_lock);
 323        error = shmem_radix_tree_replace(mapping, page->index, page, radswap);
 324        page->mapping = NULL;
 325        mapping->nrpages--;
 326        __dec_zone_page_state(page, NR_FILE_PAGES);
 327        __dec_zone_page_state(page, NR_SHMEM);
 328        spin_unlock_irq(&mapping->tree_lock);
 329        page_cache_release(page);
 330        BUG_ON(error);
 331}
 332
 333/*
 334 * Like find_get_pages, but collecting swap entries as well as pages.
 335 */
 336static unsigned shmem_find_get_pages_and_swap(struct address_space *mapping,
 337                                        pgoff_t start, unsigned int nr_pages,
 338                                        struct page **pages, pgoff_t *indices)
 339{
 340        void **slot;
 341        unsigned int ret = 0;
 342        struct radix_tree_iter iter;
 343
 344        if (!nr_pages)
 345                return 0;
 346
 347        rcu_read_lock();
 348restart:
 349        radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
 350                struct page *page;
 351repeat:
 352                page = radix_tree_deref_slot(slot);
 353                if (unlikely(!page))
 354                        continue;
 355                if (radix_tree_exception(page)) {
 356                        if (radix_tree_deref_retry(page))
 357                                goto restart;
 358                        /*
 359                         * Otherwise, we must be storing a swap entry
 360                         * here as an exceptional entry: so return it
 361                         * without attempting to raise page count.
 362                         */
 363                        goto export;
 364                }
 365                if (!page_cache_get_speculative(page))
 366                        goto repeat;
 367
 368                /* Has the page moved? */
 369                if (unlikely(page != *slot)) {
 370                        page_cache_release(page);
 371                        goto repeat;
 372                }
 373export:
 374                indices[ret] = iter.index;
 375                pages[ret] = page;
 376                if (++ret == nr_pages)
 377                        break;
 378        }
 379        rcu_read_unlock();
 380        return ret;
 381}
 382
 383/*
 384 * Remove swap entry from radix tree, free the swap and its page cache.
 385 */
 386static int shmem_free_swap(struct address_space *mapping,
 387                           pgoff_t index, void *radswap)
 388{
 389        int error;
 390
 391        spin_lock_irq(&mapping->tree_lock);
 392        error = shmem_radix_tree_replace(mapping, index, radswap, NULL);
 393        spin_unlock_irq(&mapping->tree_lock);
 394        if (!error)
 395                free_swap_and_cache(radix_to_swp_entry(radswap));
 396        return error;
 397}
 398
 399/*
 400 * Pagevec may contain swap entries, so shuffle up pages before releasing.
 401 */
 402static void shmem_deswap_pagevec(struct pagevec *pvec)
 403{
 404        int i, j;
 405
 406        for (i = 0, j = 0; i < pagevec_count(pvec); i++) {
 407                struct page *page = pvec->pages[i];
 408                if (!radix_tree_exceptional_entry(page))
 409                        pvec->pages[j++] = page;
 410        }
 411        pvec->nr = j;
 412}
 413
 414/*
 415 * SysV IPC SHM_UNLOCK restore Unevictable pages to their evictable lists.
 416 */
 417void shmem_unlock_mapping(struct address_space *mapping)
 418{
 419        struct pagevec pvec;
 420        pgoff_t indices[PAGEVEC_SIZE];
 421        pgoff_t index = 0;
 422
 423        pagevec_init(&pvec, 0);
 424        /*
 425         * Minor point, but we might as well stop if someone else SHM_LOCKs it.
 426         */
 427        while (!mapping_unevictable(mapping)) {
 428                /*
 429                 * Avoid pagevec_lookup(): find_get_pages() returns 0 as if it
 430                 * has finished, if it hits a row of PAGEVEC_SIZE swap entries.
 431                 */
 432                pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
 433                                        PAGEVEC_SIZE, pvec.pages, indices);
 434                if (!pvec.nr)
 435                        break;
 436                index = indices[pvec.nr - 1] + 1;
 437                shmem_deswap_pagevec(&pvec);
 438                check_move_unevictable_pages(pvec.pages, pvec.nr);
 439                pagevec_release(&pvec);
 440                cond_resched();
 441        }
 442}
 443
 444/*
 445 * Remove range of pages and swap entries from radix tree, and free them.
 446 * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate.
 447 */
 448static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
 449                                                                 bool unfalloc)
 450{
 451        struct address_space *mapping = inode->i_mapping;
 452        struct shmem_inode_info *info = SHMEM_I(inode);
 453        pgoff_t start = (lstart + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 454        pgoff_t end = (lend + 1) >> PAGE_CACHE_SHIFT;
 455        unsigned int partial_start = lstart & (PAGE_CACHE_SIZE - 1);
 456        unsigned int partial_end = (lend + 1) & (PAGE_CACHE_SIZE - 1);
 457        struct pagevec pvec;
 458        pgoff_t indices[PAGEVEC_SIZE];
 459        long nr_swaps_freed = 0;
 460        pgoff_t index;
 461        int i;
 462
 463        if (lend == -1)
 464                end = -1;       /* unsigned, so actually very big */
 465
 466        pagevec_init(&pvec, 0);
 467        index = start;
 468        while (index < end) {
 469                pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
 470                                min(end - index, (pgoff_t)PAGEVEC_SIZE),
 471                                                        pvec.pages, indices);
 472                if (!pvec.nr)
 473                        break;
 474                mem_cgroup_uncharge_start();
 475                for (i = 0; i < pagevec_count(&pvec); i++) {
 476                        struct page *page = pvec.pages[i];
 477
 478                        index = indices[i];
 479                        if (index >= end)
 480                                break;
 481
 482                        if (radix_tree_exceptional_entry(page)) {
 483                                if (unfalloc)
 484                                        continue;
 485                                nr_swaps_freed += !shmem_free_swap(mapping,
 486                                                                index, page);
 487                                continue;
 488                        }
 489
 490                        if (!trylock_page(page))
 491                                continue;
 492                        if (!unfalloc || !PageUptodate(page)) {
 493                                if (page->mapping == mapping) {
 494                                        VM_BUG_ON(PageWriteback(page));
 495                                        truncate_inode_page(mapping, page);
 496                                }
 497                        }
 498                        unlock_page(page);
 499                }
 500                shmem_deswap_pagevec(&pvec);
 501                pagevec_release(&pvec);
 502                mem_cgroup_uncharge_end();
 503                cond_resched();
 504                index++;
 505        }
 506
 507        if (partial_start) {
 508                struct page *page = NULL;
 509                shmem_getpage(inode, start - 1, &page, SGP_READ, NULL);
 510                if (page) {
 511                        unsigned int top = PAGE_CACHE_SIZE;
 512                        if (start > end) {
 513                                top = partial_end;
 514                                partial_end = 0;
 515                        }
 516                        zero_user_segment(page, partial_start, top);
 517                        set_page_dirty(page);
 518                        unlock_page(page);
 519                        page_cache_release(page);
 520                }
 521        }
 522        if (partial_end) {
 523                struct page *page = NULL;
 524                shmem_getpage(inode, end, &page, SGP_READ, NULL);
 525                if (page) {
 526                        zero_user_segment(page, 0, partial_end);
 527                        set_page_dirty(page);
 528                        unlock_page(page);
 529                        page_cache_release(page);
 530                }
 531        }
 532        if (start >= end)
 533                return;
 534
 535        index = start;
 536        for ( ; ; ) {
 537                cond_resched();
 538                pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
 539                                min(end - index, (pgoff_t)PAGEVEC_SIZE),
 540                                                        pvec.pages, indices);
 541                if (!pvec.nr) {
 542                        if (index == start || unfalloc)
 543                                break;
 544                        index = start;
 545                        continue;
 546                }
 547                if ((index == start || unfalloc) && indices[0] >= end) {
 548                        shmem_deswap_pagevec(&pvec);
 549                        pagevec_release(&pvec);
 550                        break;
 551                }
 552                mem_cgroup_uncharge_start();
 553                for (i = 0; i < pagevec_count(&pvec); i++) {
 554                        struct page *page = pvec.pages[i];
 555
 556                        index = indices[i];
 557                        if (index >= end)
 558                                break;
 559
 560                        if (radix_tree_exceptional_entry(page)) {
 561                                if (unfalloc)
 562                                        continue;
 563                                nr_swaps_freed += !shmem_free_swap(mapping,
 564                                                                index, page);
 565                                continue;
 566                        }
 567
 568                        lock_page(page);
 569                        if (!unfalloc || !PageUptodate(page)) {
 570                                if (page->mapping == mapping) {
 571                                        VM_BUG_ON(PageWriteback(page));
 572                                        truncate_inode_page(mapping, page);
 573                                }
 574                        }
 575                        unlock_page(page);
 576                }
 577                shmem_deswap_pagevec(&pvec);
 578                pagevec_release(&pvec);
 579                mem_cgroup_uncharge_end();
 580                index++;
 581        }
 582
 583        spin_lock(&info->lock);
 584        info->swapped -= nr_swaps_freed;
 585        shmem_recalc_inode(inode);
 586        spin_unlock(&info->lock);
 587}
 588
 589void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
 590{
 591        shmem_undo_range(inode, lstart, lend, false);
 592        inode->i_ctime = inode->i_mtime = CURRENT_TIME;
 593}
 594EXPORT_SYMBOL_GPL(shmem_truncate_range);
 595
 596static int shmem_setattr(struct dentry *dentry, struct iattr *attr)
 597{
 598        struct inode *inode = dentry->d_inode;
 599        int error;
 600
 601        error = inode_change_ok(inode, attr);
 602        if (error)
 603                return error;
 604
 605        if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
 606                loff_t oldsize = inode->i_size;
 607                loff_t newsize = attr->ia_size;
 608
 609                if (newsize != oldsize) {
 610                        i_size_write(inode, newsize);
 611                        inode->i_ctime = inode->i_mtime = CURRENT_TIME;
 612                }
 613                if (newsize < oldsize) {
 614                        loff_t holebegin = round_up(newsize, PAGE_SIZE);
 615                        unmap_mapping_range(inode->i_mapping, holebegin, 0, 1);
 616                        shmem_truncate_range(inode, newsize, (loff_t)-1);
 617                        /* unmap again to remove racily COWed private pages */
 618                        unmap_mapping_range(inode->i_mapping, holebegin, 0, 1);
 619                }
 620        }
 621
 622        setattr_copy(inode, attr);
 623#ifdef CONFIG_TMPFS_POSIX_ACL
 624        if (attr->ia_valid & ATTR_MODE)
 625                error = generic_acl_chmod(inode);
 626#endif
 627        return error;
 628}
 629
 630static void shmem_evict_inode(struct inode *inode)
 631{
 632        struct shmem_inode_info *info = SHMEM_I(inode);
 633
 634        if (inode->i_mapping->a_ops == &shmem_aops) {
 635                shmem_unacct_size(info->flags, inode->i_size);
 636                inode->i_size = 0;
 637                shmem_truncate_range(inode, 0, (loff_t)-1);
 638                if (!list_empty(&info->swaplist)) {
 639                        mutex_lock(&shmem_swaplist_mutex);
 640                        list_del_init(&info->swaplist);
 641                        mutex_unlock(&shmem_swaplist_mutex);
 642                }
 643        } else
 644                kfree(info->symlink);
 645
 646        simple_xattrs_free(&info->xattrs);
 647        WARN_ON(inode->i_blocks);
 648        shmem_free_inode(inode->i_sb);
 649        clear_inode(inode);
 650}
 651
 652/*
 653 * If swap found in inode, free it and move page from swapcache to filecache.
 654 */
 655static int shmem_unuse_inode(struct shmem_inode_info *info,
 656                             swp_entry_t swap, struct page **pagep)
 657{
 658        struct address_space *mapping = info->vfs_inode.i_mapping;
 659        void *radswap;
 660        pgoff_t index;
 661        gfp_t gfp;
 662        int error = 0;
 663
 664        radswap = swp_to_radix_entry(swap);
 665        index = radix_tree_locate_item(&mapping->page_tree, radswap);
 666        if (index == -1)
 667                return 0;
 668
 669        /*
 670         * Move _head_ to start search for next from here.
 671         * But be careful: shmem_evict_inode checks list_empty without taking
 672         * mutex, and there's an instant in list_move_tail when info->swaplist
 673         * would appear empty, if it were the only one on shmem_swaplist.
 674         */
 675        if (shmem_swaplist.next != &info->swaplist)
 676                list_move_tail(&shmem_swaplist, &info->swaplist);
 677
 678        gfp = mapping_gfp_mask(mapping);
 679        if (shmem_should_replace_page(*pagep, gfp)) {
 680                mutex_unlock(&shmem_swaplist_mutex);
 681                error = shmem_replace_page(pagep, gfp, info, index);
 682                mutex_lock(&shmem_swaplist_mutex);
 683                /*
 684                 * We needed to drop mutex to make that restrictive page
 685                 * allocation, but the inode might have been freed while we
 686                 * dropped it: although a racing shmem_evict_inode() cannot
 687                 * complete without emptying the radix_tree, our page lock
 688                 * on this swapcache page is not enough to prevent that -
 689                 * free_swap_and_cache() of our swap entry will only
 690                 * trylock_page(), removing swap from radix_tree whatever.
 691                 *
 692                 * We must not proceed to shmem_add_to_page_cache() if the
 693                 * inode has been freed, but of course we cannot rely on
 694                 * inode or mapping or info to check that.  However, we can
 695                 * safely check if our swap entry is still in use (and here
 696                 * it can't have got reused for another page): if it's still
 697                 * in use, then the inode cannot have been freed yet, and we
 698                 * can safely proceed (if it's no longer in use, that tells
 699                 * nothing about the inode, but we don't need to unuse swap).
 700                 */
 701                if (!page_swapcount(*pagep))
 702                        error = -ENOENT;
 703        }
 704
 705        /*
 706         * We rely on shmem_swaplist_mutex, not only to protect the swaplist,
 707         * but also to hold up shmem_evict_inode(): so inode cannot be freed
 708         * beneath us (pagelock doesn't help until the page is in pagecache).
 709         */
 710        if (!error)
 711                error = shmem_add_to_page_cache(*pagep, mapping, index,
 712                                                GFP_NOWAIT, radswap);
 713        if (error != -ENOMEM) {
 714                /*
 715                 * Truncation and eviction use free_swap_and_cache(), which
 716                 * only does trylock page: if we raced, best clean up here.
 717                 */
 718                delete_from_swap_cache(*pagep);
 719                set_page_dirty(*pagep);
 720                if (!error) {
 721                        spin_lock(&info->lock);
 722                        info->swapped--;
 723                        spin_unlock(&info->lock);
 724                        swap_free(swap);
 725                }
 726                error = 1;      /* not an error, but entry was found */
 727        }
 728        return error;
 729}
 730
 731/*
 732 * Search through swapped inodes to find and replace swap by page.
 733 */
 734int shmem_unuse(swp_entry_t swap, struct page *page)
 735{
 736        struct list_head *this, *next;
 737        struct shmem_inode_info *info;
 738        int found = 0;
 739        int error = 0;
 740
 741        /*
 742         * There's a faint possibility that swap page was replaced before
 743         * caller locked it: caller will come back later with the right page.
 744         */
 745        if (unlikely(!PageSwapCache(page) || page_private(page) != swap.val))
 746                goto out;
 747
 748        /*
 749         * Charge page using GFP_KERNEL while we can wait, before taking
 750         * the shmem_swaplist_mutex which might hold up shmem_writepage().
 751         * Charged back to the user (not to caller) when swap account is used.
 752         */
 753        error = mem_cgroup_cache_charge(page, current->mm, GFP_KERNEL);
 754        if (error)
 755                goto out;
 756        /* No radix_tree_preload: swap entry keeps a place for page in tree */
 757
 758        mutex_lock(&shmem_swaplist_mutex);
 759        list_for_each_safe(this, next, &shmem_swaplist) {
 760                info = list_entry(this, struct shmem_inode_info, swaplist);
 761                if (info->swapped)
 762                        found = shmem_unuse_inode(info, swap, &page);
 763                else
 764                        list_del_init(&info->swaplist);
 765                cond_resched();
 766                if (found)
 767                        break;
 768        }
 769        mutex_unlock(&shmem_swaplist_mutex);
 770
 771        if (found < 0)
 772                error = found;
 773out:
 774        unlock_page(page);
 775        page_cache_release(page);
 776        return error;
 777}
 778
 779/*
 780 * Move the page from the page cache to the swap cache.
 781 */
 782static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 783{
 784        struct shmem_inode_info *info;
 785        struct address_space *mapping;
 786        struct inode *inode;
 787        swp_entry_t swap;
 788        pgoff_t index;
 789
 790        BUG_ON(!PageLocked(page));
 791        mapping = page->mapping;
 792        index = page->index;
 793        inode = mapping->host;
 794        info = SHMEM_I(inode);
 795        if (info->flags & VM_LOCKED)
 796                goto redirty;
 797        if (!total_swap_pages)
 798                goto redirty;
 799
 800        /*
 801         * shmem_backing_dev_info's capabilities prevent regular writeback or
 802         * sync from ever calling shmem_writepage; but a stacking filesystem
 803         * might use ->writepage of its underlying filesystem, in which case
 804         * tmpfs should write out to swap only in response to memory pressure,
 805         * and not for the writeback threads or sync.
 806         */
 807        if (!wbc->for_reclaim) {
 808                WARN_ON_ONCE(1);        /* Still happens? Tell us about it! */
 809                goto redirty;
 810        }
 811
 812        /*
 813         * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC
 814         * value into swapfile.c, the only way we can correctly account for a
 815         * fallocated page arriving here is now to initialize it and write it.
 816         *
 817         * That's okay for a page already fallocated earlier, but if we have
 818         * not yet completed the fallocation, then (a) we want to keep track
 819         * of this page in case we have to undo it, and (b) it may not be a
 820         * good idea to continue anyway, once we're pushing into swap.  So
 821         * reactivate the page, and let shmem_fallocate() quit when too many.
 822         */
 823        if (!PageUptodate(page)) {
 824                if (inode->i_private) {
 825                        struct shmem_falloc *shmem_falloc;
 826                        spin_lock(&inode->i_lock);
 827                        shmem_falloc = inode->i_private;
 828                        if (shmem_falloc &&
 829                            index >= shmem_falloc->start &&
 830                            index < shmem_falloc->next)
 831                                shmem_falloc->nr_unswapped++;
 832                        else
 833                                shmem_falloc = NULL;
 834                        spin_unlock(&inode->i_lock);
 835                        if (shmem_falloc)
 836                                goto redirty;
 837                }
 838                clear_highpage(page);
 839                flush_dcache_page(page);
 840                SetPageUptodate(page);
 841        }
 842
 843        swap = get_swap_page();
 844        if (!swap.val)
 845                goto redirty;
 846
 847        /*
 848         * Add inode to shmem_unuse()'s list of swapped-out inodes,
 849         * if it's not already there.  Do it now before the page is
 850         * moved to swap cache, when its pagelock no longer protects
 851         * the inode from eviction.  But don't unlock the mutex until
 852         * we've incremented swapped, because shmem_unuse_inode() will
 853         * prune a !swapped inode from the swaplist under this mutex.
 854         */
 855        mutex_lock(&shmem_swaplist_mutex);
 856        if (list_empty(&info->swaplist))
 857                list_add_tail(&info->swaplist, &shmem_swaplist);
 858
 859        if (add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
 860                swap_shmem_alloc(swap);
 861                shmem_delete_from_page_cache(page, swp_to_radix_entry(swap));
 862
 863                spin_lock(&info->lock);
 864                info->swapped++;
 865                shmem_recalc_inode(inode);
 866                spin_unlock(&info->lock);
 867
 868                mutex_unlock(&shmem_swaplist_mutex);
 869                BUG_ON(page_mapped(page));
 870                swap_writepage(page, wbc);
 871                return 0;
 872        }
 873
 874        mutex_unlock(&shmem_swaplist_mutex);
 875        swapcache_free(swap, NULL);
 876redirty:
 877        set_page_dirty(page);
 878        if (wbc->for_reclaim)
 879                return AOP_WRITEPAGE_ACTIVATE;  /* Return with page locked */
 880        unlock_page(page);
 881        return 0;
 882}
 883
 884#ifdef CONFIG_NUMA
 885#ifdef CONFIG_TMPFS
 886static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
 887{
 888        char buffer[64];
 889
 890        if (!mpol || mpol->mode == MPOL_DEFAULT)
 891                return;         /* show nothing */
 892
 893        mpol_to_str(buffer, sizeof(buffer), mpol);
 894
 895        seq_printf(seq, ",mpol=%s", buffer);
 896}
 897
 898static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
 899{
 900        struct mempolicy *mpol = NULL;
 901        if (sbinfo->mpol) {
 902                spin_lock(&sbinfo->stat_lock);  /* prevent replace/use races */
 903                mpol = sbinfo->mpol;
 904                mpol_get(mpol);
 905                spin_unlock(&sbinfo->stat_lock);
 906        }
 907        return mpol;
 908}
 909#endif /* CONFIG_TMPFS */
 910
 911static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
 912                        struct shmem_inode_info *info, pgoff_t index)
 913{
 914        struct vm_area_struct pvma;
 915        struct page *page;
 916
 917        /* Create a pseudo vma that just contains the policy */
 918        pvma.vm_start = 0;
 919        /* Bias interleave by inode number to distribute better across nodes */
 920        pvma.vm_pgoff = index + info->vfs_inode.i_ino;
 921        pvma.vm_ops = NULL;
 922        pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
 923
 924        page = swapin_readahead(swap, gfp, &pvma, 0);
 925
 926        /* Drop reference taken by mpol_shared_policy_lookup() */
 927        mpol_cond_put(pvma.vm_policy);
 928
 929        return page;
 930}
 931
 932static struct page *shmem_alloc_page(gfp_t gfp,
 933                        struct shmem_inode_info *info, pgoff_t index)
 934{
 935        struct vm_area_struct pvma;
 936        struct page *page;
 937
 938        /* Create a pseudo vma that just contains the policy */
 939        pvma.vm_start = 0;
 940        /* Bias interleave by inode number to distribute better across nodes */
 941        pvma.vm_pgoff = index + info->vfs_inode.i_ino;
 942        pvma.vm_ops = NULL;
 943        pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
 944
 945        page = alloc_page_vma(gfp, &pvma, 0);
 946
 947        /* Drop reference taken by mpol_shared_policy_lookup() */
 948        mpol_cond_put(pvma.vm_policy);
 949
 950        return page;
 951}
 952#else /* !CONFIG_NUMA */
 953#ifdef CONFIG_TMPFS
 954static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
 955{
 956}
 957#endif /* CONFIG_TMPFS */
 958
 959static inline struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
 960                        struct shmem_inode_info *info, pgoff_t index)
 961{
 962        return swapin_readahead(swap, gfp, NULL, 0);
 963}
 964
 965static inline struct page *shmem_alloc_page(gfp_t gfp,
 966                        struct shmem_inode_info *info, pgoff_t index)
 967{
 968        return alloc_page(gfp);
 969}
 970#endif /* CONFIG_NUMA */
 971
 972#if !defined(CONFIG_NUMA) || !defined(CONFIG_TMPFS)
 973static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
 974{
 975        return NULL;
 976}
 977#endif
 978
 979/*
 980 * When a page is moved from swapcache to shmem filecache (either by the
 981 * usual swapin of shmem_getpage_gfp(), or by the less common swapoff of
 982 * shmem_unuse_inode()), it may have been read in earlier from swap, in
 983 * ignorance of the mapping it belongs to.  If that mapping has special
 984 * constraints (like the gma500 GEM driver, which requires RAM below 4GB),
 985 * we may need to copy to a suitable page before moving to filecache.
 986 *
 987 * In a future release, this may well be extended to respect cpuset and
 988 * NUMA mempolicy, and applied also to anonymous pages in do_swap_page();
 989 * but for now it is a simple matter of zone.
 990 */
 991static bool shmem_should_replace_page(struct page *page, gfp_t gfp)
 992{
 993        return page_zonenum(page) > gfp_zone(gfp);
 994}
 995
 996static int shmem_replace_page(struct page **pagep, gfp_t gfp,
 997                                struct shmem_inode_info *info, pgoff_t index)
 998{
 999        struct page *oldpage, *newpage;
1000        struct address_space *swap_mapping;
1001        pgoff_t swap_index;
1002        int error;
1003
1004        oldpage = *pagep;
1005        swap_index = page_private(oldpage);
1006        swap_mapping = page_mapping(oldpage);
1007
1008        /*
1009         * We have arrived here because our zones are constrained, so don't
1010         * limit chance of success by further cpuset and node constraints.
1011         */
1012        gfp &= ~GFP_CONSTRAINT_MASK;
1013        newpage = shmem_alloc_page(gfp, info, index);
1014        if (!newpage)
1015                return -ENOMEM;
1016
1017        page_cache_get(newpage);
1018        copy_highpage(newpage, oldpage);
1019        flush_dcache_page(newpage);
1020
1021        __set_page_locked(newpage);
1022        SetPageUptodate(newpage);
1023        SetPageSwapBacked(newpage);
1024        set_page_private(newpage, swap_index);
1025        SetPageSwapCache(newpage);
1026
1027        /*
1028         * Our caller will very soon move newpage out of swapcache, but it's
1029         * a nice clean interface for us to replace oldpage by newpage there.
1030         */
1031        spin_lock_irq(&swap_mapping->tree_lock);
1032        error = shmem_radix_tree_replace(swap_mapping, swap_index, oldpage,
1033                                                                   newpage);
1034        if (!error) {
1035                __inc_zone_page_state(newpage, NR_FILE_PAGES);
1036                __dec_zone_page_state(oldpage, NR_FILE_PAGES);
1037        }
1038        spin_unlock_irq(&swap_mapping->tree_lock);
1039
1040        if (unlikely(error)) {
1041                /*
1042                 * Is this possible?  I think not, now that our callers check
1043                 * both PageSwapCache and page_private after getting page lock;
1044                 * but be defensive.  Reverse old to newpage for clear and free.
1045                 */
1046                oldpage = newpage;
1047        } else {
1048                mem_cgroup_replace_page_cache(oldpage, newpage);
1049                lru_cache_add_anon(newpage);
1050                *pagep = newpage;
1051        }
1052
1053        ClearPageSwapCache(oldpage);
1054        set_page_private(oldpage, 0);
1055
1056        unlock_page(oldpage);
1057        page_cache_release(oldpage);
1058        page_cache_release(oldpage);
1059        return error;
1060}
1061
1062/*
1063 * shmem_getpage_gfp - find page in cache, or get from swap, or allocate
1064 *
1065 * If we allocate a new one we do not mark it dirty. That's up to the
1066 * vm. If we swap it in we mark it dirty since we also free the swap
1067 * entry since a page cannot live in both the swap and page cache
1068 */
1069static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
1070        struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type)
1071{
1072        struct address_space *mapping = inode->i_mapping;
1073        struct shmem_inode_info *info;
1074        struct shmem_sb_info *sbinfo;
1075        struct page *page;
1076        swp_entry_t swap;
1077        int error;
1078        int once = 0;
1079        int alloced = 0;
1080
1081        if (index > (MAX_LFS_FILESIZE >> PAGE_CACHE_SHIFT))
1082                return -EFBIG;
1083repeat:
1084        swap.val = 0;
1085        page = find_lock_page(mapping, index);
1086        if (radix_tree_exceptional_entry(page)) {
1087                swap = radix_to_swp_entry(page);
1088                page = NULL;
1089        }
1090
1091        if (sgp != SGP_WRITE && sgp != SGP_FALLOC &&
1092            ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
1093                error = -EINVAL;
1094                goto failed;
1095        }
1096
1097        /* fallocated page? */
1098        if (page && !PageUptodate(page)) {
1099                if (sgp != SGP_READ)
1100                        goto clear;
1101                unlock_page(page);
1102                page_cache_release(page);
1103                page = NULL;
1104        }
1105        if (page || (sgp == SGP_READ && !swap.val)) {
1106                *pagep = page;
1107                return 0;
1108        }
1109
1110        /*
1111         * Fast cache lookup did not find it:
1112         * bring it back from swap or allocate.
1113         */
1114        info = SHMEM_I(inode);
1115        sbinfo = SHMEM_SB(inode->i_sb);
1116
1117        if (swap.val) {
1118                /* Look it up and read it in.. */
1119                page = lookup_swap_cache(swap);
1120                if (!page) {
1121                        /* here we actually do the io */
1122                        if (fault_type)
1123                                *fault_type |= VM_FAULT_MAJOR;
1124                        page = shmem_swapin(swap, gfp, info, index);
1125                        if (!page) {
1126                                error = -ENOMEM;
1127                                goto failed;
1128                        }
1129                }
1130
1131                /* We have to do this with page locked to prevent races */
1132                lock_page(page);
1133                if (!PageSwapCache(page) || page_private(page) != swap.val ||
1134                    !shmem_confirm_swap(mapping, index, swap)) {
1135                        error = -EEXIST;        /* try again */
1136                        goto unlock;
1137                }
1138                if (!PageUptodate(page)) {
1139                        error = -EIO;
1140                        goto failed;
1141                }
1142                wait_on_page_writeback(page);
1143
1144                if (shmem_should_replace_page(page, gfp)) {
1145                        error = shmem_replace_page(&page, gfp, info, index);
1146                        if (error)
1147                                goto failed;
1148                }
1149
1150                error = mem_cgroup_cache_charge(page, current->mm,
1151                                                gfp & GFP_RECLAIM_MASK);
1152                if (!error) {
1153                        error = shmem_add_to_page_cache(page, mapping, index,
1154                                                gfp, swp_to_radix_entry(swap));
1155                        /*
1156                         * We already confirmed swap under page lock, and make
1157                         * no memory allocation here, so usually no possibility
1158                         * of error; but free_swap_and_cache() only trylocks a
1159                         * page, so it is just possible that the entry has been
1160                         * truncated or holepunched since swap was confirmed.
1161                         * shmem_undo_range() will have done some of the
1162                         * unaccounting, now delete_from_swap_cache() will do
1163                         * the rest (including mem_cgroup_uncharge_swapcache).
1164                         * Reset swap.val? No, leave it so "failed" goes back to
1165                         * "repeat": reading a hole and writing should succeed.
1166                         */
1167                        if (error)
1168                                delete_from_swap_cache(page);
1169                }
1170                if (error)
1171                        goto failed;
1172
1173                spin_lock(&info->lock);
1174                info->swapped--;
1175                shmem_recalc_inode(inode);
1176                spin_unlock(&info->lock);
1177
1178                delete_from_swap_cache(page);
1179                set_page_dirty(page);
1180                swap_free(swap);
1181
1182        } else {
1183                if (shmem_acct_block(info->flags)) {
1184                        error = -ENOSPC;
1185                        goto failed;
1186                }
1187                if (sbinfo->max_blocks) {
1188                        if (percpu_counter_compare(&sbinfo->used_blocks,
1189                                                sbinfo->max_blocks) >= 0) {
1190                                error = -ENOSPC;
1191                                goto unacct;
1192                        }
1193                        percpu_counter_inc(&sbinfo->used_blocks);
1194                }
1195
1196                page = shmem_alloc_page(gfp, info, index);
1197                if (!page) {
1198                        error = -ENOMEM;
1199                        goto decused;
1200                }
1201
1202                SetPageSwapBacked(page);
1203                __set_page_locked(page);
1204                error = mem_cgroup_cache_charge(page, current->mm,
1205                                                gfp & GFP_RECLAIM_MASK);
1206                if (error)
1207                        goto decused;
1208                error = radix_tree_preload(gfp & GFP_RECLAIM_MASK);
1209                if (!error) {
1210                        error = shmem_add_to_page_cache(page, mapping, index,
1211                                                        gfp, NULL);
1212                        radix_tree_preload_end();
1213                }
1214                if (error) {
1215                        mem_cgroup_uncharge_cache_page(page);
1216                        goto decused;
1217                }
1218                lru_cache_add_anon(page);
1219
1220                spin_lock(&info->lock);
1221                info->alloced++;
1222                inode->i_blocks += BLOCKS_PER_PAGE;
1223                shmem_recalc_inode(inode);
1224                spin_unlock(&info->lock);
1225                alloced = true;
1226
1227                /*
1228                 * Let SGP_FALLOC use the SGP_WRITE optimization on a new page.
1229                 */
1230                if (sgp == SGP_FALLOC)
1231                        sgp = SGP_WRITE;
1232clear:
1233                /*
1234                 * Let SGP_WRITE caller clear ends if write does not fill page;
1235                 * but SGP_FALLOC on a page fallocated earlier must initialize
1236                 * it now, lest undo on failure cancel our earlier guarantee.
1237                 */
1238                if (sgp != SGP_WRITE) {
1239                        clear_highpage(page);
1240                        flush_dcache_page(page);
1241                        SetPageUptodate(page);
1242                }
1243                if (sgp == SGP_DIRTY)
1244                        set_page_dirty(page);
1245        }
1246
1247        /* Perhaps the file has been truncated since we checked */
1248        if (sgp != SGP_WRITE && sgp != SGP_FALLOC &&
1249            ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
1250                error = -EINVAL;
1251                if (alloced)
1252                        goto trunc;
1253                else
1254                        goto failed;
1255        }
1256        *pagep = page;
1257        return 0;
1258
1259        /*
1260         * Error recovery.
1261         */
1262trunc:
1263        info = SHMEM_I(inode);
1264        ClearPageDirty(page);
1265        delete_from_page_cache(page);
1266        spin_lock(&info->lock);
1267        info->alloced--;
1268        inode->i_blocks -= BLOCKS_PER_PAGE;
1269        spin_unlock(&info->lock);
1270decused:
1271        sbinfo = SHMEM_SB(inode->i_sb);
1272        if (sbinfo->max_blocks)
1273                percpu_counter_add(&sbinfo->used_blocks, -1);
1274unacct:
1275        shmem_unacct_blocks(info->flags, 1);
1276failed:
1277        if (swap.val && error != -EINVAL &&
1278            !shmem_confirm_swap(mapping, index, swap))
1279                error = -EEXIST;
1280unlock:
1281        if (page) {
1282                unlock_page(page);
1283                page_cache_release(page);
1284        }
1285        if (error == -ENOSPC && !once++) {
1286                info = SHMEM_I(inode);
1287                spin_lock(&info->lock);
1288                shmem_recalc_inode(inode);
1289                spin_unlock(&info->lock);
1290                goto repeat;
1291        }
1292        if (error == -EEXIST)   /* from above or from radix_tree_insert */
1293                goto repeat;
1294        return error;
1295}
1296
1297static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1298{
1299        struct inode *inode = file_inode(vma->vm_file);
1300        int error;
1301        int ret = VM_FAULT_LOCKED;
1302
1303        error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret);
1304        if (error)
1305                return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1306
1307        if (ret & VM_FAULT_MAJOR) {
1308                count_vm_event(PGMAJFAULT);
1309                mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1310        }
1311        return ret;
1312}
1313
1314#ifdef CONFIG_NUMA
1315static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *mpol)
1316{
1317        struct inode *inode = file_inode(vma->vm_file);
1318        return mpol_set_shared_policy(&SHMEM_I(inode)->policy, vma, mpol);
1319}
1320
1321static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
1322                                          unsigned long addr)
1323{
1324        struct inode *inode = file_inode(vma->vm_file);
1325        pgoff_t index;
1326
1327        index = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1328        return mpol_shared_policy_lookup(&SHMEM_I(inode)->policy, index);
1329}
1330#endif
1331
1332int shmem_lock(struct file *file, int lock, struct user_struct *user)
1333{
1334        struct inode *inode = file_inode(file);
1335        struct shmem_inode_info *info = SHMEM_I(inode);
1336        int retval = -ENOMEM;
1337
1338        spin_lock(&info->lock);
1339        if (lock && !(info->flags & VM_LOCKED)) {
1340                if (!user_shm_lock(inode->i_size, user))
1341                        goto out_nomem;
1342                info->flags |= VM_LOCKED;
1343                mapping_set_unevictable(file->f_mapping);
1344        }
1345        if (!lock && (info->flags & VM_LOCKED) && user) {
1346                user_shm_unlock(inode->i_size, user);
1347                info->flags &= ~VM_LOCKED;
1348                mapping_clear_unevictable(file->f_mapping);
1349        }
1350        retval = 0;
1351
1352out_nomem:
1353        spin_unlock(&info->lock);
1354        return retval;
1355}
1356
1357static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1358{
1359        file_accessed(file);
1360        vma->vm_ops = &shmem_vm_ops;
1361        return 0;
1362}
1363
1364static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir,
1365                                     umode_t mode, dev_t dev, unsigned long flags)
1366{
1367        struct inode *inode;
1368        struct shmem_inode_info *info;
1369        struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1370
1371        if (shmem_reserve_inode(sb))
1372                return NULL;
1373
1374        inode = new_inode(sb);
1375        if (inode) {
1376                inode->i_ino = get_next_ino();
1377                inode_init_owner(inode, dir, mode);
1378                inode->i_blocks = 0;
1379                inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1380                inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1381                inode->i_generation = get_seconds();
1382                info = SHMEM_I(inode);
1383                memset(info, 0, (char *)inode - (char *)info);
1384                spin_lock_init(&info->lock);
1385                info->flags = flags & VM_NORESERVE;
1386                INIT_LIST_HEAD(&info->swaplist);
1387                simple_xattrs_init(&info->xattrs);
1388                cache_no_acl(inode);
1389
1390                switch (mode & S_IFMT) {
1391                default:
1392                        inode->i_op = &shmem_special_inode_operations;
1393                        init_special_inode(inode, mode, dev);
1394                        break;
1395                case S_IFREG:
1396                        inode->i_mapping->a_ops = &shmem_aops;
1397                        inode->i_op = &shmem_inode_operations;
1398                        inode->i_fop = &shmem_file_operations;
1399                        mpol_shared_policy_init(&info->policy,
1400                                                 shmem_get_sbmpol(sbinfo));
1401                        break;
1402                case S_IFDIR:
1403                        inc_nlink(inode);
1404                        /* Some things misbehave if size == 0 on a directory */
1405                        inode->i_size = 2 * BOGO_DIRENT_SIZE;
1406                        inode->i_op = &shmem_dir_inode_operations;
1407                        inode->i_fop = &simple_dir_operations;
1408                        break;
1409                case S_IFLNK:
1410                        /*
1411                         * Must not load anything in the rbtree,
1412                         * mpol_free_shared_policy will not be called.
1413                         */
1414                        mpol_shared_policy_init(&info->policy, NULL);
1415                        break;
1416                }
1417        } else
1418                shmem_free_inode(sb);
1419        return inode;
1420}
1421
1422#ifdef CONFIG_TMPFS
1423static const struct inode_operations shmem_symlink_inode_operations;
1424static const struct inode_operations shmem_short_symlink_operations;
1425
1426#ifdef CONFIG_TMPFS_XATTR
1427static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
1428#else
1429#define shmem_initxattrs NULL
1430#endif
1431
1432static int
1433shmem_write_begin(struct file *file, struct address_space *mapping,
1434                        loff_t pos, unsigned len, unsigned flags,
1435                        struct page **pagep, void **fsdata)
1436{
1437        struct inode *inode = mapping->host;
1438        pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1439        return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
1440}
1441
1442static int
1443shmem_write_end(struct file *file, struct address_space *mapping,
1444                        loff_t pos, unsigned len, unsigned copied,
1445                        struct page *page, void *fsdata)
1446{
1447        struct inode *inode = mapping->host;
1448
1449        if (pos + copied > inode->i_size)
1450                i_size_write(inode, pos + copied);
1451
1452        if (!PageUptodate(page)) {
1453                if (copied < PAGE_CACHE_SIZE) {
1454                        unsigned from = pos & (PAGE_CACHE_SIZE - 1);
1455                        zero_user_segments(page, 0, from,
1456                                        from + copied, PAGE_CACHE_SIZE);
1457                }
1458                SetPageUptodate(page);
1459        }
1460        set_page_dirty(page);
1461        unlock_page(page);
1462        page_cache_release(page);
1463
1464        return copied;
1465}
1466
1467static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
1468{
1469        struct inode *inode = file_inode(filp);
1470        struct address_space *mapping = inode->i_mapping;
1471        pgoff_t index;
1472        unsigned long offset;
1473        enum sgp_type sgp = SGP_READ;
1474
1475        /*
1476         * Might this read be for a stacking filesystem?  Then when reading
1477         * holes of a sparse file, we actually need to allocate those pages,
1478         * and even mark them dirty, so it cannot exceed the max_blocks limit.
1479         */
1480        if (segment_eq(get_fs(), KERNEL_DS))
1481                sgp = SGP_DIRTY;
1482
1483        index = *ppos >> PAGE_CACHE_SHIFT;
1484        offset = *ppos & ~PAGE_CACHE_MASK;
1485
1486        for (;;) {
1487                struct page *page = NULL;
1488                pgoff_t end_index;
1489                unsigned long nr, ret;
1490                loff_t i_size = i_size_read(inode);
1491
1492                end_index = i_size >> PAGE_CACHE_SHIFT;
1493                if (index > end_index)
1494                        break;
1495                if (index == end_index) {
1496                        nr = i_size & ~PAGE_CACHE_MASK;
1497                        if (nr <= offset)
1498                                break;
1499                }
1500
1501                desc->error = shmem_getpage(inode, index, &page, sgp, NULL);
1502                if (desc->error) {
1503                        if (desc->error == -EINVAL)
1504                                desc->error = 0;
1505                        break;
1506                }
1507                if (page)
1508                        unlock_page(page);
1509
1510                /*
1511                 * We must evaluate after, since reads (unlike writes)
1512                 * are called without i_mutex protection against truncate
1513                 */
1514                nr = PAGE_CACHE_SIZE;
1515                i_size = i_size_read(inode);
1516                end_index = i_size >> PAGE_CACHE_SHIFT;
1517                if (index == end_index) {
1518                        nr = i_size & ~PAGE_CACHE_MASK;
1519                        if (nr <= offset) {
1520                                if (page)
1521                                        page_cache_release(page);
1522                                break;
1523                        }
1524                }
1525                nr -= offset;
1526
1527                if (page) {
1528                        /*
1529                         * If users can be writing to this page using arbitrary
1530                         * virtual addresses, take care about potential aliasing
1531                         * before reading the page on the kernel side.
1532                         */
1533                        if (mapping_writably_mapped(mapping))
1534                                flush_dcache_page(page);
1535                        /*
1536                         * Mark the page accessed if we read the beginning.
1537                         */
1538                        if (!offset)
1539                                mark_page_accessed(page);
1540                } else {
1541                        page = ZERO_PAGE(0);
1542                        page_cache_get(page);
1543                }
1544
1545                /*
1546                 * Ok, we have the page, and it's up-to-date, so
1547                 * now we can copy it to user space...
1548                 *
1549                 * The actor routine returns how many bytes were actually used..
1550                 * NOTE! This may not be the same as how much of a user buffer
1551                 * we filled up (we may be padding etc), so we can only update
1552                 * "pos" here (the actor routine has to update the user buffer
1553                 * pointers and the remaining count).
1554                 */
1555                ret = actor(desc, page, offset, nr);
1556                offset += ret;
1557                index += offset >> PAGE_CACHE_SHIFT;
1558                offset &= ~PAGE_CACHE_MASK;
1559
1560                page_cache_release(page);
1561                if (ret != nr || !desc->count)
1562                        break;
1563
1564                cond_resched();
1565        }
1566
1567        *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1568        file_accessed(filp);
1569}
1570
1571static ssize_t shmem_file_aio_read(struct kiocb *iocb,
1572                const struct iovec *iov, unsigned long nr_segs, loff_t pos)
1573{
1574        struct file *filp = iocb->ki_filp;
1575        ssize_t retval;
1576        unsigned long seg;
1577        size_t count;
1578        loff_t *ppos = &iocb->ki_pos;
1579
1580        retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1581        if (retval)
1582                return retval;
1583
1584        for (seg = 0; seg < nr_segs; seg++) {
1585                read_descriptor_t desc;
1586
1587                desc.written = 0;
1588                desc.arg.buf = iov[seg].iov_base;
1589                desc.count = iov[seg].iov_len;
1590                if (desc.count == 0)
1591                        continue;
1592                desc.error = 0;
1593                do_shmem_file_read(filp, ppos, &desc, file_read_actor);
1594                retval += desc.written;
1595                if (desc.error) {
1596                        retval = retval ?: desc.error;
1597                        break;
1598                }
1599                if (desc.count > 0)
1600                        break;
1601        }
1602        return retval;
1603}
1604
1605static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
1606                                struct pipe_inode_info *pipe, size_t len,
1607                                unsigned int flags)
1608{
1609        struct address_space *mapping = in->f_mapping;
1610        struct inode *inode = mapping->host;
1611        unsigned int loff, nr_pages, req_pages;
1612        struct page *pages[PIPE_DEF_BUFFERS];
1613        struct partial_page partial[PIPE_DEF_BUFFERS];
1614        struct page *page;
1615        pgoff_t index, end_index;
1616        loff_t isize, left;
1617        int error, page_nr;
1618        struct splice_pipe_desc spd = {
1619                .pages = pages,
1620                .partial = partial,
1621                .nr_pages_max = PIPE_DEF_BUFFERS,
1622                .flags = flags,
1623                .ops = &page_cache_pipe_buf_ops,
1624                .spd_release = spd_release_page,
1625        };
1626
1627        isize = i_size_read(inode);
1628        if (unlikely(*ppos >= isize))
1629                return 0;
1630
1631        left = isize - *ppos;
1632        if (unlikely(left < len))
1633                len = left;
1634
1635        if (splice_grow_spd(pipe, &spd))
1636                return -ENOMEM;
1637
1638        index = *ppos >> PAGE_CACHE_SHIFT;
1639        loff = *ppos & ~PAGE_CACHE_MASK;
1640        req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1641        nr_pages = min(req_pages, pipe->buffers);
1642
1643        spd.nr_pages = find_get_pages_contig(mapping, index,
1644                                                nr_pages, spd.pages);
1645        index += spd.nr_pages;
1646        error = 0;
1647
1648        while (spd.nr_pages < nr_pages) {
1649                error = shmem_getpage(inode, index, &page, SGP_CACHE, NULL);
1650                if (error)
1651                        break;
1652                unlock_page(page);
1653                spd.pages[spd.nr_pages++] = page;
1654                index++;
1655        }
1656
1657        index = *ppos >> PAGE_CACHE_SHIFT;
1658        nr_pages = spd.nr_pages;
1659        spd.nr_pages = 0;
1660
1661        for (page_nr = 0; page_nr < nr_pages; page_nr++) {
1662                unsigned int this_len;
1663
1664                if (!len)
1665                        break;
1666
1667                this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
1668                page = spd.pages[page_nr];
1669
1670                if (!PageUptodate(page) || page->mapping != mapping) {
1671                        error = shmem_getpage(inode, index, &page,
1672                                                        SGP_CACHE, NULL);
1673                        if (error)
1674                                break;
1675                        unlock_page(page);
1676                        page_cache_release(spd.pages[page_nr]);
1677                        spd.pages[page_nr] = page;
1678                }
1679
1680                isize = i_size_read(inode);
1681                end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1682                if (unlikely(!isize || index > end_index))
1683                        break;
1684
1685                if (end_index == index) {
1686                        unsigned int plen;
1687
1688                        plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1689                        if (plen <= loff)
1690                                break;
1691
1692                        this_len = min(this_len, plen - loff);
1693                        len = this_len;
1694                }
1695
1696                spd.partial[page_nr].offset = loff;
1697                spd.partial[page_nr].len = this_len;
1698                len -= this_len;
1699                loff = 0;
1700                spd.nr_pages++;
1701                index++;
1702        }
1703
1704        while (page_nr < nr_pages)
1705                page_cache_release(spd.pages[page_nr++]);
1706
1707        if (spd.nr_pages)
1708                error = splice_to_pipe(pipe, &spd);
1709
1710        splice_shrink_spd(&spd);
1711
1712        if (error > 0) {
1713                *ppos += error;
1714                file_accessed(in);
1715        }
1716        return error;
1717}
1718
1719/*
1720 * llseek SEEK_DATA or SEEK_HOLE through the radix_tree.
1721 */
1722static pgoff_t shmem_seek_hole_data(struct address_space *mapping,
1723                                    pgoff_t index, pgoff_t end, int whence)
1724{
1725        struct page *page;
1726        struct pagevec pvec;
1727        pgoff_t indices[PAGEVEC_SIZE];
1728        bool done = false;
1729        int i;
1730
1731        pagevec_init(&pvec, 0);
1732        pvec.nr = 1;            /* start small: we may be there already */
1733        while (!done) {
1734                pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
1735                                        pvec.nr, pvec.pages, indices);
1736                if (!pvec.nr) {
1737                        if (whence == SEEK_DATA)
1738                                index = end;
1739                        break;
1740                }
1741                for (i = 0; i < pvec.nr; i++, index++) {
1742                        if (index < indices[i]) {
1743                                if (whence == SEEK_HOLE) {
1744                                        done = true;
1745                                        break;
1746                                }
1747                                index = indices[i];
1748                        }
1749                        page = pvec.pages[i];
1750                        if (page && !radix_tree_exceptional_entry(page)) {
1751                                if (!PageUptodate(page))
1752                                        page = NULL;
1753                        }
1754                        if (index >= end ||
1755                            (page && whence == SEEK_DATA) ||
1756                            (!page && whence == SEEK_HOLE)) {
1757                                done = true;
1758                                break;
1759                        }
1760                }
1761                shmem_deswap_pagevec(&pvec);
1762                pagevec_release(&pvec);
1763                pvec.nr = PAGEVEC_SIZE;
1764                cond_resched();
1765        }
1766        return index;
1767}
1768
1769static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence)
1770{
1771        struct address_space *mapping = file->f_mapping;
1772        struct inode *inode = mapping->host;
1773        pgoff_t start, end;
1774        loff_t new_offset;
1775
1776        if (whence != SEEK_DATA && whence != SEEK_HOLE)
1777                return generic_file_llseek_size(file, offset, whence,
1778                                        MAX_LFS_FILESIZE, i_size_read(inode));
1779        mutex_lock(&inode->i_mutex);
1780        /* We're holding i_mutex so we can access i_size directly */
1781
1782        if (offset < 0)
1783                offset = -EINVAL;
1784        else if (offset >= inode->i_size)
1785                offset = -ENXIO;
1786        else {
1787                start = offset >> PAGE_CACHE_SHIFT;
1788                end = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1789                new_offset = shmem_seek_hole_data(mapping, start, end, whence);
1790                new_offset <<= PAGE_CACHE_SHIFT;
1791                if (new_offset > offset) {
1792                        if (new_offset < inode->i_size)
1793                                offset = new_offset;
1794                        else if (whence == SEEK_DATA)
1795                                offset = -ENXIO;
1796                        else
1797                                offset = inode->i_size;
1798                }
1799        }
1800
1801        if (offset >= 0 && offset != file->f_pos) {
1802                file->f_pos = offset;
1803                file->f_version = 0;
1804        }
1805        mutex_unlock(&inode->i_mutex);
1806        return offset;
1807}
1808
1809static long shmem_fallocate(struct file *file, int mode, loff_t offset,
1810                                                         loff_t len)
1811{
1812        struct inode *inode = file_inode(file);
1813        struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1814        struct shmem_falloc shmem_falloc;
1815        pgoff_t start, index, end;
1816        int error;
1817
1818        mutex_lock(&inode->i_mutex);
1819
1820        if (mode & FALLOC_FL_PUNCH_HOLE) {
1821                struct address_space *mapping = file->f_mapping;
1822                loff_t unmap_start = round_up(offset, PAGE_SIZE);
1823                loff_t unmap_end = round_down(offset + len, PAGE_SIZE) - 1;
1824
1825                if ((u64)unmap_end > (u64)unmap_start)
1826                        unmap_mapping_range(mapping, unmap_start,
1827                                            1 + unmap_end - unmap_start, 0);
1828                shmem_truncate_range(inode, offset, offset + len - 1);
1829                /* No need to unmap again: hole-punching leaves COWed pages */
1830                error = 0;
1831                goto out;
1832        }
1833
1834        /* We need to check rlimit even when FALLOC_FL_KEEP_SIZE */
1835        error = inode_newsize_ok(inode, offset + len);
1836        if (error)
1837                goto out;
1838
1839        start = offset >> PAGE_CACHE_SHIFT;
1840        end = (offset + len + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1841        /* Try to avoid a swapstorm if len is impossible to satisfy */
1842        if (sbinfo->max_blocks && end - start > sbinfo->max_blocks) {
1843                error = -ENOSPC;
1844                goto out;
1845        }
1846
1847        shmem_falloc.start = start;
1848        shmem_falloc.next  = start;
1849        shmem_falloc.nr_falloced = 0;
1850        shmem_falloc.nr_unswapped = 0;
1851        spin_lock(&inode->i_lock);
1852        inode->i_private = &shmem_falloc;
1853        spin_unlock(&inode->i_lock);
1854
1855        for (index = start; index < end; index++) {
1856                struct page *page;
1857
1858                /*
1859                 * Good, the fallocate(2) manpage permits EINTR: we may have
1860                 * been interrupted because we are using up too much memory.
1861                 */
1862                if (signal_pending(current))
1863                        error = -EINTR;
1864                else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
1865                        error = -ENOMEM;
1866                else
1867                        error = shmem_getpage(inode, index, &page, SGP_FALLOC,
1868                                                                        NULL);
1869                if (error) {
1870                        /* Remove the !PageUptodate pages we added */
1871                        shmem_undo_range(inode,
1872                                (loff_t)start << PAGE_CACHE_SHIFT,
1873                                (loff_t)index << PAGE_CACHE_SHIFT, true);
1874                        goto undone;
1875                }
1876
1877                /*
1878                 * Inform shmem_writepage() how far we have reached.
1879                 * No need for lock or barrier: we have the page lock.
1880                 */
1881                shmem_falloc.next++;
1882                if (!PageUptodate(page))
1883                        shmem_falloc.nr_falloced++;
1884
1885                /*
1886                 * If !PageUptodate, leave it that way so that freeable pages
1887                 * can be recognized if we need to rollback on error later.
1888                 * But set_page_dirty so that memory pressure will swap rather
1889                 * than free the pages we are allocating (and SGP_CACHE pages
1890                 * might still be clean: we now need to mark those dirty too).
1891                 */
1892                set_page_dirty(page);
1893                unlock_page(page);
1894                page_cache_release(page);
1895                cond_resched();
1896        }
1897
1898        if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
1899                i_size_write(inode, offset + len);
1900        inode->i_ctime = CURRENT_TIME;
1901undone:
1902        spin_lock(&inode->i_lock);
1903        inode->i_private = NULL;
1904        spin_unlock(&inode->i_lock);
1905out:
1906        mutex_unlock(&inode->i_mutex);
1907        return error;
1908}
1909
1910static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
1911{
1912        struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
1913
1914        buf->f_type = TMPFS_MAGIC;
1915        buf->f_bsize = PAGE_CACHE_SIZE;
1916        buf->f_namelen = NAME_MAX;
1917        if (sbinfo->max_blocks) {
1918                buf->f_blocks = sbinfo->max_blocks;
1919                buf->f_bavail =
1920                buf->f_bfree  = sbinfo->max_blocks -
1921                                percpu_counter_sum(&sbinfo->used_blocks);
1922        }
1923        if (sbinfo->max_inodes) {
1924                buf->f_files = sbinfo->max_inodes;
1925                buf->f_ffree = sbinfo->free_inodes;
1926        }
1927        /* else leave those fields 0 like simple_statfs */
1928        return 0;
1929}
1930
1931/*
1932 * File creation. Allocate an inode, and we're done..
1933 */
1934static int
1935shmem_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
1936{
1937        struct inode *inode;
1938        int error = -ENOSPC;
1939
1940        inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
1941        if (inode) {
1942                error = security_inode_init_security(inode, dir,
1943                                                     &dentry->d_name,
1944                                                     shmem_initxattrs, NULL);
1945                if (error) {
1946                        if (error != -EOPNOTSUPP) {
1947                                iput(inode);
1948                                return error;
1949                        }
1950                }
1951#ifdef CONFIG_TMPFS_POSIX_ACL
1952                error = generic_acl_init(inode, dir);
1953                if (error) {
1954                        iput(inode);
1955                        return error;
1956                }
1957#else
1958                error = 0;
1959#endif
1960                dir->i_size += BOGO_DIRENT_SIZE;
1961                dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1962                d_instantiate(dentry, inode);
1963                dget(dentry); /* Extra count - pin the dentry in core */
1964        }
1965        return error;
1966}
1967
1968static int shmem_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
1969{
1970        int error;
1971
1972        if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
1973                return error;
1974        inc_nlink(dir);
1975        return 0;
1976}
1977
1978static int shmem_create(struct inode *dir, struct dentry *dentry, umode_t mode,
1979                bool excl)
1980{
1981        return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
1982}
1983
1984/*
1985 * Link a file..
1986 */
1987static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
1988{
1989        struct inode *inode = old_dentry->d_inode;
1990        int ret;
1991
1992        /*
1993         * No ordinary (disk based) filesystem counts links as inodes;
1994         * but each new link needs a new dentry, pinning lowmem, and
1995         * tmpfs dentries cannot be pruned until they are unlinked.
1996         */
1997        ret = shmem_reserve_inode(inode->i_sb);
1998        if (ret)
1999                goto out;
2000
2001        dir->i_size += BOGO_DIRENT_SIZE;
2002        inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2003        inc_nlink(inode);
2004        ihold(inode);   /* New dentry reference */
2005        dget(dentry);           /* Extra pinning count for the created dentry */
2006        d_instantiate(dentry, inode);
2007out:
2008        return ret;
2009}
2010
2011static int shmem_unlink(struct inode *dir, struct dentry *dentry)
2012{
2013        struct inode *inode = dentry->d_inode;
2014
2015        if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
2016                shmem_free_inode(inode->i_sb);
2017
2018        dir->i_size -= BOGO_DIRENT_SIZE;
2019        inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2020        drop_nlink(inode);
2021        dput(dentry);   /* Undo the count from "create" - this does all the work */
2022        return 0;
2023}
2024
2025static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
2026{
2027        if (!simple_empty(dentry))
2028                return -ENOTEMPTY;
2029
2030        drop_nlink(dentry->d_inode);
2031        drop_nlink(dir);
2032        return shmem_unlink(dir, dentry);
2033}
2034
2035/*
2036 * The VFS layer already does all the dentry stuff for rename,
2037 * we just have to decrement the usage count for the target if
2038 * it exists so that the VFS layer correctly free's it when it
2039 * gets overwritten.
2040 */
2041static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
2042{
2043        struct inode *inode = old_dentry->d_inode;
2044        int they_are_dirs = S_ISDIR(inode->i_mode);
2045
2046        if (!simple_empty(new_dentry))
2047                return -ENOTEMPTY;
2048
2049        if (new_dentry->d_inode) {
2050                (void) shmem_unlink(new_dir, new_dentry);
2051                if (they_are_dirs)
2052                        drop_nlink(old_dir);
2053        } else if (they_are_dirs) {
2054                drop_nlink(old_dir);
2055                inc_nlink(new_dir);
2056        }
2057
2058        old_dir->i_size -= BOGO_DIRENT_SIZE;
2059        new_dir->i_size += BOGO_DIRENT_SIZE;
2060        old_dir->i_ctime = old_dir->i_mtime =
2061        new_dir->i_ctime = new_dir->i_mtime =
2062        inode->i_ctime = CURRENT_TIME;
2063        return 0;
2064}
2065
2066static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
2067{
2068        int error;
2069        int len;
2070        struct inode *inode;
2071        struct page *page;
2072        char *kaddr;
2073        struct shmem_inode_info *info;
2074
2075        len = strlen(symname) + 1;
2076        if (len > PAGE_CACHE_SIZE)
2077                return -ENAMETOOLONG;
2078
2079        inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0, VM_NORESERVE);
2080        if (!inode)
2081                return -ENOSPC;
2082
2083        error = security_inode_init_security(inode, dir, &dentry->d_name,
2084                                             shmem_initxattrs, NULL);
2085        if (error) {
2086                if (error != -EOPNOTSUPP) {
2087                        iput(inode);
2088                        return error;
2089                }
2090                error = 0;
2091        }
2092
2093        info = SHMEM_I(inode);
2094        inode->i_size = len-1;
2095        if (len <= SHORT_SYMLINK_LEN) {
2096                info->symlink = kmemdup(symname, len, GFP_KERNEL);
2097                if (!info->symlink) {
2098                        iput(inode);
2099                        return -ENOMEM;
2100                }
2101                inode->i_op = &shmem_short_symlink_operations;
2102        } else {
2103                error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
2104                if (error) {
2105                        iput(inode);
2106                        return error;
2107                }
2108                inode->i_mapping->a_ops = &shmem_aops;
2109                inode->i_op = &shmem_symlink_inode_operations;
2110                kaddr = kmap_atomic(page);
2111                memcpy(kaddr, symname, len);
2112                kunmap_atomic(kaddr);
2113                SetPageUptodate(page);
2114                set_page_dirty(page);
2115                unlock_page(page);
2116                page_cache_release(page);
2117        }
2118        dir->i_size += BOGO_DIRENT_SIZE;
2119        dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2120        d_instantiate(dentry, inode);
2121        dget(dentry);
2122        return 0;
2123}
2124
2125static void *shmem_follow_short_symlink(struct dentry *dentry, struct nameidata *nd)
2126{
2127        nd_set_link(nd, SHMEM_I(dentry->d_inode)->symlink);
2128        return NULL;
2129}
2130
2131static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
2132{
2133        struct page *page = NULL;
2134        int error = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
2135        nd_set_link(nd, error ? ERR_PTR(error) : kmap(page));
2136        if (page)
2137                unlock_page(page);
2138        return page;
2139}
2140
2141static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
2142{
2143        if (!IS_ERR(nd_get_link(nd))) {
2144                struct page *page = cookie;
2145                kunmap(page);
2146                mark_page_accessed(page);
2147                page_cache_release(page);
2148        }
2149}
2150
2151#ifdef CONFIG_TMPFS_XATTR
2152/*
2153 * Superblocks without xattr inode operations may get some security.* xattr
2154 * support from the LSM "for free". As soon as we have any other xattrs
2155 * like ACLs, we also need to implement the security.* handlers at
2156 * filesystem level, though.
2157 */
2158
2159/*
2160 * Callback for security_inode_init_security() for acquiring xattrs.
2161 */
2162static int shmem_initxattrs(struct inode *inode,
2163                            const struct xattr *xattr_array,
2164                            void *fs_info)
2165{
2166        struct shmem_inode_info *info = SHMEM_I(inode);
2167        const struct xattr *xattr;
2168        struct simple_xattr *new_xattr;
2169        size_t len;
2170
2171        for (xattr = xattr_array; xattr->name != NULL; xattr++) {
2172                new_xattr = simple_xattr_alloc(xattr->value, xattr->value_len);
2173                if (!new_xattr)
2174                        return -ENOMEM;
2175
2176                len = strlen(xattr->name) + 1;
2177                new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
2178                                          GFP_KERNEL);
2179                if (!new_xattr->name) {
2180                        kfree(new_xattr);
2181                        return -ENOMEM;
2182                }
2183
2184                memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
2185                       XATTR_SECURITY_PREFIX_LEN);
2186                memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
2187                       xattr->name, len);
2188
2189                simple_xattr_list_add(&info->xattrs, new_xattr);
2190        }
2191
2192        return 0;
2193}
2194
2195static const struct xattr_handler *shmem_xattr_handlers[] = {
2196#ifdef CONFIG_TMPFS_POSIX_ACL
2197        &generic_acl_access_handler,
2198        &generic_acl_default_handler,
2199#endif
2200        NULL
2201};
2202
2203static int shmem_xattr_validate(const char *name)
2204{
2205        struct { const char *prefix; size_t len; } arr[] = {
2206                { XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN },
2207                { XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN }
2208        };
2209        int i;
2210
2211        for (i = 0; i < ARRAY_SIZE(arr); i++) {
2212                size_t preflen = arr[i].len;
2213                if (strncmp(name, arr[i].prefix, preflen) == 0) {
2214                        if (!name[preflen])
2215                                return -EINVAL;
2216                        return 0;
2217                }
2218        }
2219        return -EOPNOTSUPP;
2220}
2221
2222static ssize_t shmem_getxattr(struct dentry *dentry, const char *name,
2223                              void *buffer, size_t size)
2224{
2225        struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2226        int err;
2227
2228        /*
2229         * If this is a request for a synthetic attribute in the system.*
2230         * namespace use the generic infrastructure to resolve a handler
2231         * for it via sb->s_xattr.
2232         */
2233        if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2234                return generic_getxattr(dentry, name, buffer, size);
2235
2236        err = shmem_xattr_validate(name);
2237        if (err)
2238                return err;
2239
2240        return simple_xattr_get(&info->xattrs, name, buffer, size);
2241}
2242
2243static int shmem_setxattr(struct dentry *dentry, const char *name,
2244                          const void *value, size_t size, int flags)
2245{
2246        struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2247        int err;
2248
2249        /*
2250         * If this is a request for a synthetic attribute in the system.*
2251         * namespace use the generic infrastructure to resolve a handler
2252         * for it via sb->s_xattr.
2253         */
2254        if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2255                return generic_setxattr(dentry, name, value, size, flags);
2256
2257        err = shmem_xattr_validate(name);
2258        if (err)
2259                return err;
2260
2261        return simple_xattr_set(&info->xattrs, name, value, size, flags);
2262}
2263
2264static int shmem_removexattr(struct dentry *dentry, const char *name)
2265{
2266        struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2267        int err;
2268
2269        /*
2270         * If this is a request for a synthetic attribute in the system.*
2271         * namespace use the generic infrastructure to resolve a handler
2272         * for it via sb->s_xattr.
2273         */
2274        if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2275                return generic_removexattr(dentry, name);
2276
2277        err = shmem_xattr_validate(name);
2278        if (err)
2279                return err;
2280
2281        return simple_xattr_remove(&info->xattrs, name);
2282}
2283
2284static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
2285{
2286        struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2287        return simple_xattr_list(&info->xattrs, buffer, size);
2288}
2289#endif /* CONFIG_TMPFS_XATTR */
2290
2291static const struct inode_operations shmem_short_symlink_operations = {
2292        .readlink       = generic_readlink,
2293        .follow_link    = shmem_follow_short_symlink,
2294#ifdef CONFIG_TMPFS_XATTR
2295        .setxattr       = shmem_setxattr,
2296        .getxattr       = shmem_getxattr,
2297        .listxattr      = shmem_listxattr,
2298        .removexattr    = shmem_removexattr,
2299#endif
2300};
2301
2302static const struct inode_operations shmem_symlink_inode_operations = {
2303        .readlink       = generic_readlink,
2304        .follow_link    = shmem_follow_link,
2305        .put_link       = shmem_put_link,
2306#ifdef CONFIG_TMPFS_XATTR
2307        .setxattr       = shmem_setxattr,
2308        .getxattr       = shmem_getxattr,
2309        .listxattr      = shmem_listxattr,
2310        .removexattr    = shmem_removexattr,
2311#endif
2312};
2313
2314static struct dentry *shmem_get_parent(struct dentry *child)
2315{
2316        return ERR_PTR(-ESTALE);
2317}
2318
2319static int shmem_match(struct inode *ino, void *vfh)
2320{
2321        __u32 *fh = vfh;
2322        __u64 inum = fh[2];
2323        inum = (inum << 32) | fh[1];
2324        return ino->i_ino == inum && fh[0] == ino->i_generation;
2325}
2326
2327static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
2328                struct fid *fid, int fh_len, int fh_type)
2329{
2330        struct inode *inode;
2331        struct dentry *dentry = NULL;
2332        u64 inum;
2333
2334        if (fh_len < 3)
2335                return NULL;
2336
2337        inum = fid->raw[2];
2338        inum = (inum << 32) | fid->raw[1];
2339
2340        inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
2341                        shmem_match, fid->raw);
2342        if (inode) {
2343                dentry = d_find_alias(inode);
2344                iput(inode);
2345        }
2346
2347        return dentry;
2348}
2349
2350static int shmem_encode_fh(struct inode *inode, __u32 *fh, int *len,
2351                                struct inode *parent)
2352{
2353        if (*len < 3) {
2354                *len = 3;
2355                return FILEID_INVALID;
2356        }
2357
2358        if (inode_unhashed(inode)) {
2359                /* Unfortunately insert_inode_hash is not idempotent,
2360                 * so as we hash inodes here rather than at creation
2361                 * time, we need a lock to ensure we only try
2362                 * to do it once
2363                 */
2364                static DEFINE_SPINLOCK(lock);
2365                spin_lock(&lock);
2366                if (inode_unhashed(inode))
2367                        __insert_inode_hash(inode,
2368                                            inode->i_ino + inode->i_generation);
2369                spin_unlock(&lock);
2370        }
2371
2372        fh[0] = inode->i_generation;
2373        fh[1] = inode->i_ino;
2374        fh[2] = ((__u64)inode->i_ino) >> 32;
2375
2376        *len = 3;
2377        return 1;
2378}
2379
2380static const struct export_operations shmem_export_ops = {
2381        .get_parent     = shmem_get_parent,
2382        .encode_fh      = shmem_encode_fh,
2383        .fh_to_dentry   = shmem_fh_to_dentry,
2384};
2385
2386static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
2387                               bool remount)
2388{
2389        char *this_char, *value, *rest;
2390        struct mempolicy *mpol = NULL;
2391        uid_t uid;
2392        gid_t gid;
2393
2394        while (options != NULL) {
2395                this_char = options;
2396                for (;;) {
2397                        /*
2398                         * NUL-terminate this option: unfortunately,
2399                         * mount options form a comma-separated list,
2400                         * but mpol's nodelist may also contain commas.
2401                         */
2402                        options = strchr(options, ',');
2403                        if (options == NULL)
2404                                break;
2405                        options++;
2406                        if (!isdigit(*options)) {
2407                                options[-1] = '\0';
2408                                break;
2409                        }
2410                }
2411                if (!*this_char)
2412                        continue;
2413                if ((value = strchr(this_char,'=')) != NULL) {
2414                        *value++ = 0;
2415                } else {
2416                        printk(KERN_ERR
2417                            "tmpfs: No value for mount option '%s'\n",
2418                            this_char);
2419                        goto error;
2420                }
2421
2422                if (!strcmp(this_char,"size")) {
2423                        unsigned long long size;
2424                        size = memparse(value,&rest);
2425                        if (*rest == '%') {
2426                                size <<= PAGE_SHIFT;
2427                                size *= totalram_pages;
2428                                do_div(size, 100);
2429                                rest++;
2430                        }
2431                        if (*rest)
2432                                goto bad_val;
2433                        sbinfo->max_blocks =
2434                                DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
2435                } else if (!strcmp(this_char,"nr_blocks")) {
2436                        sbinfo->max_blocks = memparse(value, &rest);
2437                        if (*rest)
2438                                goto bad_val;
2439                } else if (!strcmp(this_char,"nr_inodes")) {
2440                        sbinfo->max_inodes = memparse(value, &rest);
2441                        if (*rest)
2442                                goto bad_val;
2443                } else if (!strcmp(this_char,"mode")) {
2444                        if (remount)
2445                                continue;
2446                        sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
2447                        if (*rest)
2448                                goto bad_val;
2449                } else if (!strcmp(this_char,"uid")) {
2450                        if (remount)
2451                                continue;
2452                        uid = simple_strtoul(value, &rest, 0);
2453                        if (*rest)
2454                                goto bad_val;
2455                        sbinfo->uid = make_kuid(current_user_ns(), uid);
2456                        if (!uid_valid(sbinfo->uid))
2457                                goto bad_val;
2458                } else if (!strcmp(this_char,"gid")) {
2459                        if (remount)
2460                                continue;
2461                        gid = simple_strtoul(value, &rest, 0);
2462                        if (*rest)
2463                                goto bad_val;
2464                        sbinfo->gid = make_kgid(current_user_ns(), gid);
2465                        if (!gid_valid(sbinfo->gid))
2466                                goto bad_val;
2467                } else if (!strcmp(this_char,"mpol")) {
2468                        mpol_put(mpol);
2469                        mpol = NULL;
2470                        if (mpol_parse_str(value, &mpol))
2471                                goto bad_val;
2472                } else {
2473                        printk(KERN_ERR "tmpfs: Bad mount option %s\n",
2474                               this_char);
2475                        goto error;
2476                }
2477        }
2478        sbinfo->mpol = mpol;
2479        return 0;
2480
2481bad_val:
2482        printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
2483               value, this_char);
2484error:
2485        mpol_put(mpol);
2486        return 1;
2487
2488}
2489
2490static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2491{
2492        struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2493        struct shmem_sb_info config = *sbinfo;
2494        unsigned long inodes;
2495        int error = -EINVAL;
2496
2497        config.mpol = NULL;
2498        if (shmem_parse_options(data, &config, true))
2499                return error;
2500
2501        spin_lock(&sbinfo->stat_lock);
2502        inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2503        if (percpu_counter_compare(&sbinfo->used_blocks, config.max_blocks) > 0)
2504                goto out;
2505        if (config.max_inodes < inodes)
2506                goto out;
2507        /*
2508         * Those tests disallow limited->unlimited while any are in use;
2509         * but we must separately disallow unlimited->limited, because
2510         * in that case we have no record of how much is already in use.
2511         */
2512        if (config.max_blocks && !sbinfo->max_blocks)
2513                goto out;
2514        if (config.max_inodes && !sbinfo->max_inodes)
2515                goto out;
2516
2517        error = 0;
2518        sbinfo->max_blocks  = config.max_blocks;
2519        sbinfo->max_inodes  = config.max_inodes;
2520        sbinfo->free_inodes = config.max_inodes - inodes;
2521
2522        /*
2523         * Preserve previous mempolicy unless mpol remount option was specified.
2524         */
2525        if (config.mpol) {
2526                mpol_put(sbinfo->mpol);
2527                sbinfo->mpol = config.mpol;     /* transfers initial ref */
2528        }
2529out:
2530        spin_unlock(&sbinfo->stat_lock);
2531        return error;
2532}
2533
2534static int shmem_show_options(struct seq_file *seq, struct dentry *root)
2535{
2536        struct shmem_sb_info *sbinfo = SHMEM_SB(root->d_sb);
2537
2538        if (sbinfo->max_blocks != shmem_default_max_blocks())
2539                seq_printf(seq, ",size=%luk",
2540                        sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10));
2541        if (sbinfo->max_inodes != shmem_default_max_inodes())
2542                seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
2543        if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
2544                seq_printf(seq, ",mode=%03ho", sbinfo->mode);
2545        if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID))
2546                seq_printf(seq, ",uid=%u",
2547                                from_kuid_munged(&init_user_ns, sbinfo->uid));
2548        if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
2549                seq_printf(seq, ",gid=%u",
2550                                from_kgid_munged(&init_user_ns, sbinfo->gid));
2551        shmem_show_mpol(seq, sbinfo->mpol);
2552        return 0;
2553}
2554#endif /* CONFIG_TMPFS */
2555
2556static void shmem_put_super(struct super_block *sb)
2557{
2558        struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2559
2560        percpu_counter_destroy(&sbinfo->used_blocks);
2561        mpol_put(sbinfo->mpol);
2562        kfree(sbinfo);
2563        sb->s_fs_info = NULL;
2564}
2565
2566int shmem_fill_super(struct super_block *sb, void *data, int silent)
2567{
2568        struct inode *inode;
2569        struct shmem_sb_info *sbinfo;
2570        int err = -ENOMEM;
2571
2572        /* Round up to L1_CACHE_BYTES to resist false sharing */
2573        sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
2574                                L1_CACHE_BYTES), GFP_KERNEL);
2575        if (!sbinfo)
2576                return -ENOMEM;
2577
2578        sbinfo->mode = S_IRWXUGO | S_ISVTX;
2579        sbinfo->uid = current_fsuid();
2580        sbinfo->gid = current_fsgid();
2581        sb->s_fs_info = sbinfo;
2582
2583#ifdef CONFIG_TMPFS
2584        /*
2585         * Per default we only allow half of the physical ram per
2586         * tmpfs instance, limiting inodes to one per page of lowmem;
2587         * but the internal instance is left unlimited.
2588         */
2589        if (!(sb->s_flags & MS_NOUSER)) {
2590                sbinfo->max_blocks = shmem_default_max_blocks();
2591                sbinfo->max_inodes = shmem_default_max_inodes();
2592                if (shmem_parse_options(data, sbinfo, false)) {
2593                        err = -EINVAL;
2594                        goto failed;
2595                }
2596        }
2597        sb->s_export_op = &shmem_export_ops;
2598        sb->s_flags |= MS_NOSEC;
2599#else
2600        sb->s_flags |= MS_NOUSER;
2601#endif
2602
2603        spin_lock_init(&sbinfo->stat_lock);
2604        if (percpu_counter_init(&sbinfo->used_blocks, 0))
2605                goto failed;
2606        sbinfo->free_inodes = sbinfo->max_inodes;
2607
2608        sb->s_maxbytes = MAX_LFS_FILESIZE;
2609        sb->s_blocksize = PAGE_CACHE_SIZE;
2610        sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
2611        sb->s_magic = TMPFS_MAGIC;
2612        sb->s_op = &shmem_ops;
2613        sb->s_time_gran = 1;
2614#ifdef CONFIG_TMPFS_XATTR
2615        sb->s_xattr = shmem_xattr_handlers;
2616#endif
2617#ifdef CONFIG_TMPFS_POSIX_ACL
2618        sb->s_flags |= MS_POSIXACL;
2619#endif
2620
2621        inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
2622        if (!inode)
2623                goto failed;
2624        inode->i_uid = sbinfo->uid;
2625        inode->i_gid = sbinfo->gid;
2626        sb->s_root = d_make_root(inode);
2627        if (!sb->s_root)
2628                goto failed;
2629        return 0;
2630
2631failed:
2632        shmem_put_super(sb);
2633        return err;
2634}
2635
2636static struct kmem_cache *shmem_inode_cachep;
2637
2638static struct inode *shmem_alloc_inode(struct super_block *sb)
2639{
2640        struct shmem_inode_info *info;
2641        info = kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
2642        if (!info)
2643                return NULL;
2644        return &info->vfs_inode;
2645}
2646
2647static void shmem_destroy_callback(struct rcu_head *head)
2648{
2649        struct inode *inode = container_of(head, struct inode, i_rcu);
2650        kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2651}
2652
2653static void shmem_destroy_inode(struct inode *inode)
2654{
2655        if (S_ISREG(inode->i_mode))
2656                mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2657        call_rcu(&inode->i_rcu, shmem_destroy_callback);
2658}
2659
2660static void shmem_init_inode(void *foo)
2661{
2662        struct shmem_inode_info *info = foo;
2663        inode_init_once(&info->vfs_inode);
2664}
2665
2666static int shmem_init_inodecache(void)
2667{
2668        shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
2669                                sizeof(struct shmem_inode_info),
2670                                0, SLAB_PANIC, shmem_init_inode);
2671        return 0;
2672}
2673
2674static void shmem_destroy_inodecache(void)
2675{
2676        kmem_cache_destroy(shmem_inode_cachep);
2677}
2678
2679static const struct address_space_operations shmem_aops = {
2680        .writepage      = shmem_writepage,
2681        .set_page_dirty = __set_page_dirty_no_writeback,
2682#ifdef CONFIG_TMPFS
2683        .write_begin    = shmem_write_begin,
2684        .write_end      = shmem_write_end,
2685#endif
2686        .migratepage    = migrate_page,
2687        .error_remove_page = generic_error_remove_page,
2688};
2689
2690static const struct file_operations shmem_file_operations = {
2691        .mmap           = shmem_mmap,
2692#ifdef CONFIG_TMPFS
2693        .llseek         = shmem_file_llseek,
2694        .read           = do_sync_read,
2695        .write          = do_sync_write,
2696        .aio_read       = shmem_file_aio_read,
2697        .aio_write      = generic_file_aio_write,
2698        .fsync          = noop_fsync,
2699        .splice_read    = shmem_file_splice_read,
2700        .splice_write   = generic_file_splice_write,
2701        .fallocate      = shmem_fallocate,
2702#endif
2703};
2704
2705static const struct inode_operations shmem_inode_operations = {
2706        .setattr        = shmem_setattr,
2707#ifdef CONFIG_TMPFS_XATTR
2708        .setxattr       = shmem_setxattr,
2709        .getxattr       = shmem_getxattr,
2710        .listxattr      = shmem_listxattr,
2711        .removexattr    = shmem_removexattr,
2712#endif
2713};
2714
2715static const struct inode_operations shmem_dir_inode_operations = {
2716#ifdef CONFIG_TMPFS
2717        .create         = shmem_create,
2718        .lookup         = simple_lookup,
2719        .link           = shmem_link,
2720        .unlink         = shmem_unlink,
2721        .symlink        = shmem_symlink,
2722        .mkdir          = shmem_mkdir,
2723        .rmdir          = shmem_rmdir,
2724        .mknod          = shmem_mknod,
2725        .rename         = shmem_rename,
2726#endif
2727#ifdef CONFIG_TMPFS_XATTR
2728        .setxattr       = shmem_setxattr,
2729        .getxattr       = shmem_getxattr,
2730        .listxattr      = shmem_listxattr,
2731        .removexattr    = shmem_removexattr,
2732#endif
2733#ifdef CONFIG_TMPFS_POSIX_ACL
2734        .setattr        = shmem_setattr,
2735#endif
2736};
2737
2738static const struct inode_operations shmem_special_inode_operations = {
2739#ifdef CONFIG_TMPFS_XATTR
2740        .setxattr       = shmem_setxattr,
2741        .getxattr       = shmem_getxattr,
2742        .listxattr      = shmem_listxattr,
2743        .removexattr    = shmem_removexattr,
2744#endif
2745#ifdef CONFIG_TMPFS_POSIX_ACL
2746        .setattr        = shmem_setattr,
2747#endif
2748};
2749
2750static const struct super_operations shmem_ops = {
2751        .alloc_inode    = shmem_alloc_inode,
2752        .destroy_inode  = shmem_destroy_inode,
2753#ifdef CONFIG_TMPFS
2754        .statfs         = shmem_statfs,
2755        .remount_fs     = shmem_remount_fs,
2756        .show_options   = shmem_show_options,
2757#endif
2758        .evict_inode    = shmem_evict_inode,
2759        .drop_inode     = generic_delete_inode,
2760        .put_super      = shmem_put_super,
2761};
2762
2763static const struct vm_operations_struct shmem_vm_ops = {
2764        .fault          = shmem_fault,
2765#ifdef CONFIG_NUMA
2766        .set_policy     = shmem_set_policy,
2767        .get_policy     = shmem_get_policy,
2768#endif
2769        .remap_pages    = generic_file_remap_pages,
2770};
2771
2772static struct dentry *shmem_mount(struct file_system_type *fs_type,
2773        int flags, const char *dev_name, void *data)
2774{
2775        return mount_nodev(fs_type, flags, data, shmem_fill_super);
2776}
2777
2778static struct file_system_type shmem_fs_type = {
2779        .owner          = THIS_MODULE,
2780        .name           = "tmpfs",
2781        .mount          = shmem_mount,
2782        .kill_sb        = kill_litter_super,
2783        .fs_flags       = FS_USERNS_MOUNT,
2784};
2785
2786int __init shmem_init(void)
2787{
2788        int error;
2789
2790        error = bdi_init(&shmem_backing_dev_info);
2791        if (error)
2792                goto out4;
2793
2794        error = shmem_init_inodecache();
2795        if (error)
2796                goto out3;
2797
2798        error = register_filesystem(&shmem_fs_type);
2799        if (error) {
2800                printk(KERN_ERR "Could not register tmpfs\n");
2801                goto out2;
2802        }
2803
2804        shm_mnt = vfs_kern_mount(&shmem_fs_type, MS_NOUSER,
2805                                 shmem_fs_type.name, NULL);
2806        if (IS_ERR(shm_mnt)) {
2807                error = PTR_ERR(shm_mnt);
2808                printk(KERN_ERR "Could not kern_mount tmpfs\n");
2809                goto out1;
2810        }
2811        return 0;
2812
2813out1:
2814        unregister_filesystem(&shmem_fs_type);
2815out2:
2816        shmem_destroy_inodecache();
2817out3:
2818        bdi_destroy(&shmem_backing_dev_info);
2819out4:
2820        shm_mnt = ERR_PTR(error);
2821        return error;
2822}
2823
2824#else /* !CONFIG_SHMEM */
2825
2826/*
2827 * tiny-shmem: simple shmemfs and tmpfs using ramfs code
2828 *
2829 * This is intended for small system where the benefits of the full
2830 * shmem code (swap-backed and resource-limited) are outweighed by
2831 * their complexity. On systems without swap this code should be
2832 * effectively equivalent, but much lighter weight.
2833 */
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        res = ERR_PTR(ramfs_nommu_expand_for_mapping(inode, size));
2935        if (IS_ERR(res))
2936                goto put_dentry;
2937
2938        res = alloc_file(&path, FMODE_WRITE | FMODE_READ,
2939                  &shmem_file_operations);
2940        if (IS_ERR(res))
2941                goto put_dentry;
2942
2943        return res;
2944
2945put_dentry:
2946        path_put(&path);
2947put_memory:
2948        shmem_unacct_size(flags, size);
2949        return res;
2950}
2951EXPORT_SYMBOL_GPL(shmem_file_setup);
2952
2953/**
2954 * shmem_zero_setup - setup a shared anonymous mapping
2955 * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
2956 */
2957int shmem_zero_setup(struct vm_area_struct *vma)
2958{
2959        struct file *file;
2960        loff_t size = vma->vm_end - vma->vm_start;
2961
2962        file = shmem_file_setup("dev/zero", size, vma->vm_flags);
2963        if (IS_ERR(file))
2964                return PTR_ERR(file);
2965
2966        if (vma->vm_file)
2967                fput(vma->vm_file);
2968        vma->vm_file = file;
2969        vma->vm_ops = &shmem_vm_ops;
2970        return 0;
2971}
2972
2973/**
2974 * shmem_read_mapping_page_gfp - read into page cache, using specified page allocation flags.
2975 * @mapping:    the page's address_space
2976 * @index:      the page index
2977 * @gfp:        the page allocator flags to use if allocating
2978 *
2979 * This behaves as a tmpfs "read_cache_page_gfp(mapping, index, gfp)",
2980 * with any new page allocations done using the specified allocation flags.
2981 * But read_cache_page_gfp() uses the ->readpage() method: which does not
2982 * suit tmpfs, since it may have pages in swapcache, and needs to find those
2983 * for itself; although drivers/gpu/drm i915 and ttm rely upon this support.
2984 *
2985 * i915_gem_object_get_pages_gtt() mixes __GFP_NORETRY | __GFP_NOWARN in
2986 * with the mapping_gfp_mask(), to avoid OOMing the machine unnecessarily.
2987 */
2988struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
2989                                         pgoff_t index, gfp_t gfp)
2990{
2991#ifdef CONFIG_SHMEM
2992        struct inode *inode = mapping->host;
2993        struct page *page;
2994        int error;
2995
2996        BUG_ON(mapping->a_ops != &shmem_aops);
2997        error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE, gfp, NULL);
2998        if (error)
2999                page = ERR_PTR(error);
3000        else
3001                unlock_page(page);
3002        return page;
3003#else
3004        /*
3005         * The tiny !SHMEM case uses ramfs without swap
3006         */
3007        return read_cache_page_gfp(mapping, index, gfp);
3008#endif
3009}
3010EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);
3011
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