Root/mm/shmem.c

1/*
2 * Resizable virtual memory filesystem for Linux.
3 *
4 * Copyright (C) 2000 Linus Torvalds.
5 * 2000 Transmeta Corp.
6 * 2000-2001 Christoph Rohland
7 * 2000-2001 SAP AG
8 * 2002 Red Hat Inc.
9 * Copyright (C) 2002-2011 Hugh Dickins.
10 * Copyright (C) 2011 Google Inc.
11 * Copyright (C) 2002-2005 VERITAS Software Corporation.
12 * Copyright (C) 2004 Andi Kleen, SuSE Labs
13 *
14 * Extended attribute support for tmpfs:
15 * Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@lkcl.net>
16 * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
17 *
18 * tiny-shmem:
19 * Copyright (c) 2004, 2008 Matt Mackall <mpm@selenic.com>
20 *
21 * This file is released under the GPL.
22 */
23
24#include <linux/fs.h>
25#include <linux/init.h>
26#include <linux/vfs.h>
27#include <linux/mount.h>
28#include <linux/pagemap.h>
29#include <linux/file.h>
30#include <linux/mm.h>
31#include <linux/export.h>
32#include <linux/swap.h>
33
34static struct vfsmount *shm_mnt;
35
36#ifdef CONFIG_SHMEM
37/*
38 * This virtual memory filesystem is heavily based on the ramfs. It
39 * extends ramfs by the ability to use swap and honor resource limits
40 * which makes it a completely usable filesystem.
41 */
42
43#include <linux/xattr.h>
44#include <linux/exportfs.h>
45#include <linux/posix_acl.h>
46#include <linux/generic_acl.h>
47#include <linux/mman.h>
48#include <linux/string.h>
49#include <linux/slab.h>
50#include <linux/backing-dev.h>
51#include <linux/shmem_fs.h>
52#include <linux/writeback.h>
53#include <linux/blkdev.h>
54#include <linux/pagevec.h>
55#include <linux/percpu_counter.h>
56#include <linux/falloc.h>
57#include <linux/splice.h>
58#include <linux/security.h>
59#include <linux/swapops.h>
60#include <linux/mempolicy.h>
61#include <linux/namei.h>
62#include <linux/ctype.h>
63#include <linux/migrate.h>
64#include <linux/highmem.h>
65#include <linux/seq_file.h>
66#include <linux/magic.h>
67
68#include <asm/uaccess.h>
69#include <asm/pgtable.h>
70
71#define BLOCKS_PER_PAGE (PAGE_CACHE_SIZE/512)
72#define VM_ACCT(size) (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
73
74/* Pretend that each entry is of this size in directory's i_size */
75#define BOGO_DIRENT_SIZE 20
76
77/* Symlink up to this size is kmalloc'ed instead of using a swappable page */
78#define SHORT_SYMLINK_LEN 128
79
80/*
81 * shmem_fallocate and shmem_writepage communicate via inode->i_private
82 * (with i_mutex making sure that it has only one user at a time):
83 * we would prefer not to enlarge the shmem inode just for that.
84 */
85struct shmem_falloc {
86    pgoff_t start; /* start of range currently being fallocated */
87    pgoff_t next; /* the next page offset to be fallocated */
88    pgoff_t nr_falloced; /* how many new pages have been fallocated */
89    pgoff_t nr_unswapped; /* how often writepage refused to swap out */
90};
91
92/* Flag allocation requirements to shmem_getpage */
93enum sgp_type {
94    SGP_READ, /* don't exceed i_size, don't allocate page */
95    SGP_CACHE, /* don't exceed i_size, may allocate page */
96    SGP_DIRTY, /* like SGP_CACHE, but set new page dirty */
97    SGP_WRITE, /* may exceed i_size, may allocate !Uptodate page */
98    SGP_FALLOC, /* like SGP_WRITE, but make existing page Uptodate */
99};
100
101#ifdef CONFIG_TMPFS
102static unsigned long shmem_default_max_blocks(void)
103{
104    return totalram_pages / 2;
105}
106
107static unsigned long shmem_default_max_inodes(void)
108{
109    return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
110}
111#endif
112
113static bool shmem_should_replace_page(struct page *page, gfp_t gfp);
114static int shmem_replace_page(struct page **pagep, gfp_t gfp,
115                struct shmem_inode_info *info, pgoff_t index);
116static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
117    struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type);
118
119static inline int shmem_getpage(struct inode *inode, pgoff_t index,
120    struct page **pagep, enum sgp_type sgp, int *fault_type)
121{
122    return shmem_getpage_gfp(inode, index, pagep, sgp,
123            mapping_gfp_mask(inode->i_mapping), fault_type);
124}
125
126static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
127{
128    return sb->s_fs_info;
129}
130
131/*
132 * shmem_file_setup pre-accounts the whole fixed size of a VM object,
133 * for shared memory and for shared anonymous (/dev/zero) mappings
134 * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
135 * consistent with the pre-accounting of private mappings ...
136 */
137static inline int shmem_acct_size(unsigned long flags, loff_t size)
138{
139    return (flags & VM_NORESERVE) ?
140        0 : security_vm_enough_memory_mm(current->mm, VM_ACCT(size));
141}
142
143static inline void shmem_unacct_size(unsigned long flags, loff_t size)
144{
145    if (!(flags & VM_NORESERVE))
146        vm_unacct_memory(VM_ACCT(size));
147}
148
149/*
150 * ... whereas tmpfs objects are accounted incrementally as
151 * pages are allocated, in order to allow huge sparse files.
152 * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
153 * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
154 */
155static inline int shmem_acct_block(unsigned long flags)
156{
157    return (flags & VM_NORESERVE) ?
158        security_vm_enough_memory_mm(current->mm, VM_ACCT(PAGE_CACHE_SIZE)) : 0;
159}
160
161static inline void shmem_unacct_blocks(unsigned long flags, long pages)
162{
163    if (flags & VM_NORESERVE)
164        vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
165}
166
167static const struct super_operations shmem_ops;
168static const struct address_space_operations shmem_aops;
169static const struct file_operations shmem_file_operations;
170static const struct inode_operations shmem_inode_operations;
171static const struct inode_operations shmem_dir_inode_operations;
172static const struct inode_operations shmem_special_inode_operations;
173static const struct vm_operations_struct shmem_vm_ops;
174
175static struct backing_dev_info shmem_backing_dev_info __read_mostly = {
176    .ra_pages = 0, /* No readahead */
177    .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
178};
179
180static LIST_HEAD(shmem_swaplist);
181static DEFINE_MUTEX(shmem_swaplist_mutex);
182
183static int shmem_reserve_inode(struct super_block *sb)
184{
185    struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
186    if (sbinfo->max_inodes) {
187        spin_lock(&sbinfo->stat_lock);
188        if (!sbinfo->free_inodes) {
189            spin_unlock(&sbinfo->stat_lock);
190            return -ENOSPC;
191        }
192        sbinfo->free_inodes--;
193        spin_unlock(&sbinfo->stat_lock);
194    }
195    return 0;
196}
197
198static void shmem_free_inode(struct super_block *sb)
199{
200    struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
201    if (sbinfo->max_inodes) {
202        spin_lock(&sbinfo->stat_lock);
203        sbinfo->free_inodes++;
204        spin_unlock(&sbinfo->stat_lock);
205    }
206}
207
208/**
209 * shmem_recalc_inode - recalculate the block usage of an inode
210 * @inode: inode to recalc
211 *
212 * We have to calculate the free blocks since the mm can drop
213 * undirtied hole pages behind our back.
214 *
215 * But normally info->alloced == inode->i_mapping->nrpages + info->swapped
216 * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
217 *
218 * It has to be called with the spinlock held.
219 */
220static void shmem_recalc_inode(struct inode *inode)
221{
222    struct shmem_inode_info *info = SHMEM_I(inode);
223    long freed;
224
225    freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
226    if (freed > 0) {
227        struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
228        if (sbinfo->max_blocks)
229            percpu_counter_add(&sbinfo->used_blocks, -freed);
230        info->alloced -= freed;
231        inode->i_blocks -= freed * BLOCKS_PER_PAGE;
232        shmem_unacct_blocks(info->flags, freed);
233    }
234}
235
236/*
237 * Replace item expected in radix tree by a new item, while holding tree lock.
238 */
239static int shmem_radix_tree_replace(struct address_space *mapping,
240            pgoff_t index, void *expected, void *replacement)
241{
242    void **pslot;
243    void *item = NULL;
244
245    VM_BUG_ON(!expected);
246    pslot = radix_tree_lookup_slot(&mapping->page_tree, index);
247    if (pslot)
248        item = radix_tree_deref_slot_protected(pslot,
249                            &mapping->tree_lock);
250    if (item != expected)
251        return -ENOENT;
252    if (replacement)
253        radix_tree_replace_slot(pslot, replacement);
254    else
255        radix_tree_delete(&mapping->page_tree, index);
256    return 0;
257}
258
259/*
260 * Sometimes, before we decide whether to proceed or to fail, we must check
261 * that an entry was not already brought back from swap by a racing thread.
262 *
263 * Checking page is not enough: by the time a SwapCache page is locked, it
264 * might be reused, and again be SwapCache, using the same swap as before.
265 */
266static bool shmem_confirm_swap(struct address_space *mapping,
267                   pgoff_t index, swp_entry_t swap)
268{
269    void *item;
270
271    rcu_read_lock();
272    item = radix_tree_lookup(&mapping->page_tree, index);
273    rcu_read_unlock();
274    return item == swp_to_radix_entry(swap);
275}
276
277/*
278 * Like add_to_page_cache_locked, but error if expected item has gone.
279 */
280static int shmem_add_to_page_cache(struct page *page,
281                   struct address_space *mapping,
282                   pgoff_t index, gfp_t gfp, void *expected)
283{
284    int error;
285
286    VM_BUG_ON(!PageLocked(page));
287    VM_BUG_ON(!PageSwapBacked(page));
288
289    page_cache_get(page);
290    page->mapping = mapping;
291    page->index = index;
292
293    spin_lock_irq(&mapping->tree_lock);
294    if (!expected)
295        error = radix_tree_insert(&mapping->page_tree, index, page);
296    else
297        error = shmem_radix_tree_replace(mapping, index, expected,
298                                 page);
299    if (!error) {
300        mapping->nrpages++;
301        __inc_zone_page_state(page, NR_FILE_PAGES);
302        __inc_zone_page_state(page, NR_SHMEM);
303        spin_unlock_irq(&mapping->tree_lock);
304    } else {
305        page->mapping = NULL;
306        spin_unlock_irq(&mapping->tree_lock);
307        page_cache_release(page);
308    }
309    return error;
310}
311
312/*
313 * Like delete_from_page_cache, but substitutes swap for page.
314 */
315static void shmem_delete_from_page_cache(struct page *page, void *radswap)
316{
317    struct address_space *mapping = page->mapping;
318    int error;
319
320    spin_lock_irq(&mapping->tree_lock);
321    error = shmem_radix_tree_replace(mapping, page->index, page, radswap);
322    page->mapping = NULL;
323    mapping->nrpages--;
324    __dec_zone_page_state(page, NR_FILE_PAGES);
325    __dec_zone_page_state(page, NR_SHMEM);
326    spin_unlock_irq(&mapping->tree_lock);
327    page_cache_release(page);
328    BUG_ON(error);
329}
330
331/*
332 * Like find_get_pages, but collecting swap entries as well as pages.
333 */
334static unsigned shmem_find_get_pages_and_swap(struct address_space *mapping,
335                    pgoff_t start, unsigned int nr_pages,
336                    struct page **pages, pgoff_t *indices)
337{
338    void **slot;
339    unsigned int ret = 0;
340    struct radix_tree_iter iter;
341
342    if (!nr_pages)
343        return 0;
344
345    rcu_read_lock();
346restart:
347    radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
348        struct page *page;
349repeat:
350        page = radix_tree_deref_slot(slot);
351        if (unlikely(!page))
352            continue;
353        if (radix_tree_exception(page)) {
354            if (radix_tree_deref_retry(page))
355                goto restart;
356            /*
357             * Otherwise, we must be storing a swap entry
358             * here as an exceptional entry: so return it
359             * without attempting to raise page count.
360             */
361            goto export;
362        }
363        if (!page_cache_get_speculative(page))
364            goto repeat;
365
366        /* Has the page moved? */
367        if (unlikely(page != *slot)) {
368            page_cache_release(page);
369            goto repeat;
370        }
371export:
372        indices[ret] = iter.index;
373        pages[ret] = page;
374        if (++ret == nr_pages)
375            break;
376    }
377    rcu_read_unlock();
378    return ret;
379}
380
381/*
382 * Remove swap entry from radix tree, free the swap and its page cache.
383 */
384static int shmem_free_swap(struct address_space *mapping,
385               pgoff_t index, void *radswap)
386{
387    int error;
388
389    spin_lock_irq(&mapping->tree_lock);
390    error = shmem_radix_tree_replace(mapping, index, radswap, NULL);
391    spin_unlock_irq(&mapping->tree_lock);
392    if (!error)
393        free_swap_and_cache(radix_to_swp_entry(radswap));
394    return error;
395}
396
397/*
398 * Pagevec may contain swap entries, so shuffle up pages before releasing.
399 */
400static void shmem_deswap_pagevec(struct pagevec *pvec)
401{
402    int i, j;
403
404    for (i = 0, j = 0; i < pagevec_count(pvec); i++) {
405        struct page *page = pvec->pages[i];
406        if (!radix_tree_exceptional_entry(page))
407            pvec->pages[j++] = page;
408    }
409    pvec->nr = j;
410}
411
412/*
413 * SysV IPC SHM_UNLOCK restore Unevictable pages to their evictable lists.
414 */
415void shmem_unlock_mapping(struct address_space *mapping)
416{
417    struct pagevec pvec;
418    pgoff_t indices[PAGEVEC_SIZE];
419    pgoff_t index = 0;
420
421    pagevec_init(&pvec, 0);
422    /*
423     * Minor point, but we might as well stop if someone else SHM_LOCKs it.
424     */
425    while (!mapping_unevictable(mapping)) {
426        /*
427         * Avoid pagevec_lookup(): find_get_pages() returns 0 as if it
428         * has finished, if it hits a row of PAGEVEC_SIZE swap entries.
429         */
430        pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
431                    PAGEVEC_SIZE, pvec.pages, indices);
432        if (!pvec.nr)
433            break;
434        index = indices[pvec.nr - 1] + 1;
435        shmem_deswap_pagevec(&pvec);
436        check_move_unevictable_pages(pvec.pages, pvec.nr);
437        pagevec_release(&pvec);
438        cond_resched();
439    }
440}
441
442/*
443 * Remove range of pages and swap entries from radix tree, and free them.
444 * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate.
445 */
446static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
447                                 bool unfalloc)
448{
449    struct address_space *mapping = inode->i_mapping;
450    struct shmem_inode_info *info = SHMEM_I(inode);
451    pgoff_t start = (lstart + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
452    pgoff_t end = (lend + 1) >> PAGE_CACHE_SHIFT;
453    unsigned int partial_start = lstart & (PAGE_CACHE_SIZE - 1);
454    unsigned int partial_end = (lend + 1) & (PAGE_CACHE_SIZE - 1);
455    struct pagevec pvec;
456    pgoff_t indices[PAGEVEC_SIZE];
457    long nr_swaps_freed = 0;
458    pgoff_t index;
459    int i;
460
461    if (lend == -1)
462        end = -1; /* unsigned, so actually very big */
463
464    pagevec_init(&pvec, 0);
465    index = start;
466    while (index < end) {
467        pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
468                min(end - index, (pgoff_t)PAGEVEC_SIZE),
469                            pvec.pages, indices);
470        if (!pvec.nr)
471            break;
472        mem_cgroup_uncharge_start();
473        for (i = 0; i < pagevec_count(&pvec); i++) {
474            struct page *page = pvec.pages[i];
475
476            index = indices[i];
477            if (index >= end)
478                break;
479
480            if (radix_tree_exceptional_entry(page)) {
481                if (unfalloc)
482                    continue;
483                nr_swaps_freed += !shmem_free_swap(mapping,
484                                index, page);
485                continue;
486            }
487
488            if (!trylock_page(page))
489                continue;
490            if (!unfalloc || !PageUptodate(page)) {
491                if (page->mapping == mapping) {
492                    VM_BUG_ON(PageWriteback(page));
493                    truncate_inode_page(mapping, page);
494                }
495            }
496            unlock_page(page);
497        }
498        shmem_deswap_pagevec(&pvec);
499        pagevec_release(&pvec);
500        mem_cgroup_uncharge_end();
501        cond_resched();
502        index++;
503    }
504
505    if (partial_start) {
506        struct page *page = NULL;
507        shmem_getpage(inode, start - 1, &page, SGP_READ, NULL);
508        if (page) {
509            unsigned int top = PAGE_CACHE_SIZE;
510            if (start > end) {
511                top = partial_end;
512                partial_end = 0;
513            }
514            zero_user_segment(page, partial_start, top);
515            set_page_dirty(page);
516            unlock_page(page);
517            page_cache_release(page);
518        }
519    }
520    if (partial_end) {
521        struct page *page = NULL;
522        shmem_getpage(inode, end, &page, SGP_READ, NULL);
523        if (page) {
524            zero_user_segment(page, 0, partial_end);
525            set_page_dirty(page);
526            unlock_page(page);
527            page_cache_release(page);
528        }
529    }
530    if (start >= end)
531        return;
532
533    index = start;
534    for ( ; ; ) {
535        cond_resched();
536        pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
537                min(end - index, (pgoff_t)PAGEVEC_SIZE),
538                            pvec.pages, indices);
539        if (!pvec.nr) {
540            if (index == start || unfalloc)
541                break;
542            index = start;
543            continue;
544        }
545        if ((index == start || unfalloc) && indices[0] >= end) {
546            shmem_deswap_pagevec(&pvec);
547            pagevec_release(&pvec);
548            break;
549        }
550        mem_cgroup_uncharge_start();
551        for (i = 0; i < pagevec_count(&pvec); i++) {
552            struct page *page = pvec.pages[i];
553
554            index = indices[i];
555            if (index >= end)
556                break;
557
558            if (radix_tree_exceptional_entry(page)) {
559                if (unfalloc)
560                    continue;
561                nr_swaps_freed += !shmem_free_swap(mapping,
562                                index, page);
563                continue;
564            }
565
566            lock_page(page);
567            if (!unfalloc || !PageUptodate(page)) {
568                if (page->mapping == mapping) {
569                    VM_BUG_ON(PageWriteback(page));
570                    truncate_inode_page(mapping, page);
571                }
572            }
573            unlock_page(page);
574        }
575        shmem_deswap_pagevec(&pvec);
576        pagevec_release(&pvec);
577        mem_cgroup_uncharge_end();
578        index++;
579    }
580
581    spin_lock(&info->lock);
582    info->swapped -= nr_swaps_freed;
583    shmem_recalc_inode(inode);
584    spin_unlock(&info->lock);
585}
586
587void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
588{
589    shmem_undo_range(inode, lstart, lend, false);
590    inode->i_ctime = inode->i_mtime = CURRENT_TIME;
591}
592EXPORT_SYMBOL_GPL(shmem_truncate_range);
593
594static int shmem_setattr(struct dentry *dentry, struct iattr *attr)
595{
596    struct inode *inode = dentry->d_inode;
597    int error;
598
599    error = inode_change_ok(inode, attr);
600    if (error)
601        return error;
602
603    if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
604        loff_t oldsize = inode->i_size;
605        loff_t newsize = attr->ia_size;
606
607        if (newsize != oldsize) {
608            i_size_write(inode, newsize);
609            inode->i_ctime = inode->i_mtime = CURRENT_TIME;
610        }
611        if (newsize < oldsize) {
612            loff_t holebegin = round_up(newsize, PAGE_SIZE);
613            unmap_mapping_range(inode->i_mapping, holebegin, 0, 1);
614            shmem_truncate_range(inode, newsize, (loff_t)-1);
615            /* unmap again to remove racily COWed private pages */
616            unmap_mapping_range(inode->i_mapping, holebegin, 0, 1);
617        }
618    }
619
620    setattr_copy(inode, attr);
621#ifdef CONFIG_TMPFS_POSIX_ACL
622    if (attr->ia_valid & ATTR_MODE)
623        error = generic_acl_chmod(inode);
624#endif
625    return error;
626}
627
628static void shmem_evict_inode(struct inode *inode)
629{
630    struct shmem_inode_info *info = SHMEM_I(inode);
631
632    if (inode->i_mapping->a_ops == &shmem_aops) {
633        shmem_unacct_size(info->flags, inode->i_size);
634        inode->i_size = 0;
635        shmem_truncate_range(inode, 0, (loff_t)-1);
636        if (!list_empty(&info->swaplist)) {
637            mutex_lock(&shmem_swaplist_mutex);
638            list_del_init(&info->swaplist);
639            mutex_unlock(&shmem_swaplist_mutex);
640        }
641    } else
642        kfree(info->symlink);
643
644    simple_xattrs_free(&info->xattrs);
645    WARN_ON(inode->i_blocks);
646    shmem_free_inode(inode->i_sb);
647    clear_inode(inode);
648}
649
650/*
651 * If swap found in inode, free it and move page from swapcache to filecache.
652 */
653static int shmem_unuse_inode(struct shmem_inode_info *info,
654                 swp_entry_t swap, struct page **pagep)
655{
656    struct address_space *mapping = info->vfs_inode.i_mapping;
657    void *radswap;
658    pgoff_t index;
659    gfp_t gfp;
660    int error = 0;
661
662    radswap = swp_to_radix_entry(swap);
663    index = radix_tree_locate_item(&mapping->page_tree, radswap);
664    if (index == -1)
665        return 0;
666
667    /*
668     * Move _head_ to start search for next from here.
669     * But be careful: shmem_evict_inode checks list_empty without taking
670     * mutex, and there's an instant in list_move_tail when info->swaplist
671     * would appear empty, if it were the only one on shmem_swaplist.
672     */
673    if (shmem_swaplist.next != &info->swaplist)
674        list_move_tail(&shmem_swaplist, &info->swaplist);
675
676    gfp = mapping_gfp_mask(mapping);
677    if (shmem_should_replace_page(*pagep, gfp)) {
678        mutex_unlock(&shmem_swaplist_mutex);
679        error = shmem_replace_page(pagep, gfp, info, index);
680        mutex_lock(&shmem_swaplist_mutex);
681        /*
682         * We needed to drop mutex to make that restrictive page
683         * allocation, but the inode might have been freed while we
684         * dropped it: although a racing shmem_evict_inode() cannot
685         * complete without emptying the radix_tree, our page lock
686         * on this swapcache page is not enough to prevent that -
687         * free_swap_and_cache() of our swap entry will only
688         * trylock_page(), removing swap from radix_tree whatever.
689         *
690         * We must not proceed to shmem_add_to_page_cache() if the
691         * inode has been freed, but of course we cannot rely on
692         * inode or mapping or info to check that. However, we can
693         * safely check if our swap entry is still in use (and here
694         * it can't have got reused for another page): if it's still
695         * in use, then the inode cannot have been freed yet, and we
696         * can safely proceed (if it's no longer in use, that tells
697         * nothing about the inode, but we don't need to unuse swap).
698         */
699        if (!page_swapcount(*pagep))
700            error = -ENOENT;
701    }
702
703    /*
704     * We rely on shmem_swaplist_mutex, not only to protect the swaplist,
705     * but also to hold up shmem_evict_inode(): so inode cannot be freed
706     * beneath us (pagelock doesn't help until the page is in pagecache).
707     */
708    if (!error)
709        error = shmem_add_to_page_cache(*pagep, mapping, index,
710                        GFP_NOWAIT, radswap);
711    if (error != -ENOMEM) {
712        /*
713         * Truncation and eviction use free_swap_and_cache(), which
714         * only does trylock page: if we raced, best clean up here.
715         */
716        delete_from_swap_cache(*pagep);
717        set_page_dirty(*pagep);
718        if (!error) {
719            spin_lock(&info->lock);
720            info->swapped--;
721            spin_unlock(&info->lock);
722            swap_free(swap);
723        }
724        error = 1; /* not an error, but entry was found */
725    }
726    return error;
727}
728
729/*
730 * Search through swapped inodes to find and replace swap by page.
731 */
732int shmem_unuse(swp_entry_t swap, struct page *page)
733{
734    struct list_head *this, *next;
735    struct shmem_inode_info *info;
736    int found = 0;
737    int error = 0;
738
739    /*
740     * There's a faint possibility that swap page was replaced before
741     * caller locked it: caller will come back later with the right page.
742     */
743    if (unlikely(!PageSwapCache(page) || page_private(page) != swap.val))
744        goto out;
745
746    /*
747     * Charge page using GFP_KERNEL while we can wait, before taking
748     * the shmem_swaplist_mutex which might hold up shmem_writepage().
749     * Charged back to the user (not to caller) when swap account is used.
750     */
751    error = mem_cgroup_cache_charge(page, current->mm, GFP_KERNEL);
752    if (error)
753        goto out;
754    /* No radix_tree_preload: swap entry keeps a place for page in tree */
755
756    mutex_lock(&shmem_swaplist_mutex);
757    list_for_each_safe(this, next, &shmem_swaplist) {
758        info = list_entry(this, struct shmem_inode_info, swaplist);
759        if (info->swapped)
760            found = shmem_unuse_inode(info, swap, &page);
761        else
762            list_del_init(&info->swaplist);
763        cond_resched();
764        if (found)
765            break;
766    }
767    mutex_unlock(&shmem_swaplist_mutex);
768
769    if (found < 0)
770        error = found;
771out:
772    unlock_page(page);
773    page_cache_release(page);
774    return error;
775}
776
777/*
778 * Move the page from the page cache to the swap cache.
779 */
780static int shmem_writepage(struct page *page, struct writeback_control *wbc)
781{
782    struct shmem_inode_info *info;
783    struct address_space *mapping;
784    struct inode *inode;
785    swp_entry_t swap;
786    pgoff_t index;
787
788    BUG_ON(!PageLocked(page));
789    mapping = page->mapping;
790    index = page->index;
791    inode = mapping->host;
792    info = SHMEM_I(inode);
793    if (info->flags & VM_LOCKED)
794        goto redirty;
795    if (!total_swap_pages)
796        goto redirty;
797
798    /*
799     * shmem_backing_dev_info's capabilities prevent regular writeback or
800     * sync from ever calling shmem_writepage; but a stacking filesystem
801     * might use ->writepage of its underlying filesystem, in which case
802     * tmpfs should write out to swap only in response to memory pressure,
803     * and not for the writeback threads or sync.
804     */
805    if (!wbc->for_reclaim) {
806        WARN_ON_ONCE(1); /* Still happens? Tell us about it! */
807        goto redirty;
808    }
809
810    /*
811     * This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC
812     * value into swapfile.c, the only way we can correctly account for a
813     * fallocated page arriving here is now to initialize it and write it.
814     *
815     * That's okay for a page already fallocated earlier, but if we have
816     * not yet completed the fallocation, then (a) we want to keep track
817     * of this page in case we have to undo it, and (b) it may not be a
818     * good idea to continue anyway, once we're pushing into swap. So
819     * reactivate the page, and let shmem_fallocate() quit when too many.
820     */
821    if (!PageUptodate(page)) {
822        if (inode->i_private) {
823            struct shmem_falloc *shmem_falloc;
824            spin_lock(&inode->i_lock);
825            shmem_falloc = inode->i_private;
826            if (shmem_falloc &&
827                index >= shmem_falloc->start &&
828                index < shmem_falloc->next)
829                shmem_falloc->nr_unswapped++;
830            else
831                shmem_falloc = NULL;
832            spin_unlock(&inode->i_lock);
833            if (shmem_falloc)
834                goto redirty;
835        }
836        clear_highpage(page);
837        flush_dcache_page(page);
838        SetPageUptodate(page);
839    }
840
841    swap = get_swap_page();
842    if (!swap.val)
843        goto redirty;
844
845    /*
846     * Add inode to shmem_unuse()'s list of swapped-out inodes,
847     * if it's not already there. Do it now before the page is
848     * moved to swap cache, when its pagelock no longer protects
849     * the inode from eviction. But don't unlock the mutex until
850     * we've incremented swapped, because shmem_unuse_inode() will
851     * prune a !swapped inode from the swaplist under this mutex.
852     */
853    mutex_lock(&shmem_swaplist_mutex);
854    if (list_empty(&info->swaplist))
855        list_add_tail(&info->swaplist, &shmem_swaplist);
856
857    if (add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
858        swap_shmem_alloc(swap);
859        shmem_delete_from_page_cache(page, swp_to_radix_entry(swap));
860
861        spin_lock(&info->lock);
862        info->swapped++;
863        shmem_recalc_inode(inode);
864        spin_unlock(&info->lock);
865
866        mutex_unlock(&shmem_swaplist_mutex);
867        BUG_ON(page_mapped(page));
868        swap_writepage(page, wbc);
869        return 0;
870    }
871
872    mutex_unlock(&shmem_swaplist_mutex);
873    swapcache_free(swap, NULL);
874redirty:
875    set_page_dirty(page);
876    if (wbc->for_reclaim)
877        return AOP_WRITEPAGE_ACTIVATE; /* Return with page locked */
878    unlock_page(page);
879    return 0;
880}
881
882#ifdef CONFIG_NUMA
883#ifdef CONFIG_TMPFS
884static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
885{
886    char buffer[64];
887
888    if (!mpol || mpol->mode == MPOL_DEFAULT)
889        return; /* show nothing */
890
891    mpol_to_str(buffer, sizeof(buffer), mpol);
892
893    seq_printf(seq, ",mpol=%s", buffer);
894}
895
896static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
897{
898    struct mempolicy *mpol = NULL;
899    if (sbinfo->mpol) {
900        spin_lock(&sbinfo->stat_lock); /* prevent replace/use races */
901        mpol = sbinfo->mpol;
902        mpol_get(mpol);
903        spin_unlock(&sbinfo->stat_lock);
904    }
905    return mpol;
906}
907#endif /* CONFIG_TMPFS */
908
909static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
910            struct shmem_inode_info *info, pgoff_t index)
911{
912    struct vm_area_struct pvma;
913    struct page *page;
914
915    /* Create a pseudo vma that just contains the policy */
916    pvma.vm_start = 0;
917    /* Bias interleave by inode number to distribute better across nodes */
918    pvma.vm_pgoff = index + info->vfs_inode.i_ino;
919    pvma.vm_ops = NULL;
920    pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
921
922    page = swapin_readahead(swap, gfp, &pvma, 0);
923
924    /* Drop reference taken by mpol_shared_policy_lookup() */
925    mpol_cond_put(pvma.vm_policy);
926
927    return page;
928}
929
930static struct page *shmem_alloc_page(gfp_t gfp,
931            struct shmem_inode_info *info, pgoff_t index)
932{
933    struct vm_area_struct pvma;
934    struct page *page;
935
936    /* Create a pseudo vma that just contains the policy */
937    pvma.vm_start = 0;
938    /* Bias interleave by inode number to distribute better across nodes */
939    pvma.vm_pgoff = index + info->vfs_inode.i_ino;
940    pvma.vm_ops = NULL;
941    pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
942
943    page = alloc_page_vma(gfp, &pvma, 0);
944
945    /* Drop reference taken by mpol_shared_policy_lookup() */
946    mpol_cond_put(pvma.vm_policy);
947
948    return page;
949}
950#else /* !CONFIG_NUMA */
951#ifdef CONFIG_TMPFS
952static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
953{
954}
955#endif /* CONFIG_TMPFS */
956
957static inline struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
958            struct shmem_inode_info *info, pgoff_t index)
959{
960    return swapin_readahead(swap, gfp, NULL, 0);
961}
962
963static inline struct page *shmem_alloc_page(gfp_t gfp,
964            struct shmem_inode_info *info, pgoff_t index)
965{
966    return alloc_page(gfp);
967}
968#endif /* CONFIG_NUMA */
969
970#if !defined(CONFIG_NUMA) || !defined(CONFIG_TMPFS)
971static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
972{
973    return NULL;
974}
975#endif
976
977/*
978 * When a page is moved from swapcache to shmem filecache (either by the
979 * usual swapin of shmem_getpage_gfp(), or by the less common swapoff of
980 * shmem_unuse_inode()), it may have been read in earlier from swap, in
981 * ignorance of the mapping it belongs to. If that mapping has special
982 * constraints (like the gma500 GEM driver, which requires RAM below 4GB),
983 * we may need to copy to a suitable page before moving to filecache.
984 *
985 * In a future release, this may well be extended to respect cpuset and
986 * NUMA mempolicy, and applied also to anonymous pages in do_swap_page();
987 * but for now it is a simple matter of zone.
988 */
989static bool shmem_should_replace_page(struct page *page, gfp_t gfp)
990{
991    return page_zonenum(page) > gfp_zone(gfp);
992}
993
994static int shmem_replace_page(struct page **pagep, gfp_t gfp,
995                struct shmem_inode_info *info, pgoff_t index)
996{
997    struct page *oldpage, *newpage;
998    struct address_space *swap_mapping;
999    pgoff_t swap_index;
1000    int error;
1001
1002    oldpage = *pagep;
1003    swap_index = page_private(oldpage);
1004    swap_mapping = page_mapping(oldpage);
1005
1006    /*
1007     * We have arrived here because our zones are constrained, so don't
1008     * limit chance of success by further cpuset and node constraints.
1009     */
1010    gfp &= ~GFP_CONSTRAINT_MASK;
1011    newpage = shmem_alloc_page(gfp, info, index);
1012    if (!newpage)
1013        return -ENOMEM;
1014
1015    page_cache_get(newpage);
1016    copy_highpage(newpage, oldpage);
1017    flush_dcache_page(newpage);
1018
1019    __set_page_locked(newpage);
1020    SetPageUptodate(newpage);
1021    SetPageSwapBacked(newpage);
1022    set_page_private(newpage, swap_index);
1023    SetPageSwapCache(newpage);
1024
1025    /*
1026     * Our caller will very soon move newpage out of swapcache, but it's
1027     * a nice clean interface for us to replace oldpage by newpage there.
1028     */
1029    spin_lock_irq(&swap_mapping->tree_lock);
1030    error = shmem_radix_tree_replace(swap_mapping, swap_index, oldpage,
1031                                   newpage);
1032    if (!error) {
1033        __inc_zone_page_state(newpage, NR_FILE_PAGES);
1034        __dec_zone_page_state(oldpage, NR_FILE_PAGES);
1035    }
1036    spin_unlock_irq(&swap_mapping->tree_lock);
1037
1038    if (unlikely(error)) {
1039        /*
1040         * Is this possible? I think not, now that our callers check
1041         * both PageSwapCache and page_private after getting page lock;
1042         * but be defensive. Reverse old to newpage for clear and free.
1043         */
1044        oldpage = newpage;
1045    } else {
1046        mem_cgroup_replace_page_cache(oldpage, newpage);
1047        lru_cache_add_anon(newpage);
1048        *pagep = newpage;
1049    }
1050
1051    ClearPageSwapCache(oldpage);
1052    set_page_private(oldpage, 0);
1053
1054    unlock_page(oldpage);
1055    page_cache_release(oldpage);
1056    page_cache_release(oldpage);
1057    return error;
1058}
1059
1060/*
1061 * shmem_getpage_gfp - find page in cache, or get from swap, or allocate
1062 *
1063 * If we allocate a new one we do not mark it dirty. That's up to the
1064 * vm. If we swap it in we mark it dirty since we also free the swap
1065 * entry since a page cannot live in both the swap and page cache
1066 */
1067static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
1068    struct page **pagep, enum sgp_type sgp, gfp_t gfp, int *fault_type)
1069{
1070    struct address_space *mapping = inode->i_mapping;
1071    struct shmem_inode_info *info;
1072    struct shmem_sb_info *sbinfo;
1073    struct page *page;
1074    swp_entry_t swap;
1075    int error;
1076    int once = 0;
1077    int alloced = 0;
1078
1079    if (index > (MAX_LFS_FILESIZE >> PAGE_CACHE_SHIFT))
1080        return -EFBIG;
1081repeat:
1082    swap.val = 0;
1083    page = find_lock_page(mapping, index);
1084    if (radix_tree_exceptional_entry(page)) {
1085        swap = radix_to_swp_entry(page);
1086        page = NULL;
1087    }
1088
1089    if (sgp != SGP_WRITE && sgp != SGP_FALLOC &&
1090        ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
1091        error = -EINVAL;
1092        goto failed;
1093    }
1094
1095    /* fallocated page? */
1096    if (page && !PageUptodate(page)) {
1097        if (sgp != SGP_READ)
1098            goto clear;
1099        unlock_page(page);
1100        page_cache_release(page);
1101        page = NULL;
1102    }
1103    if (page || (sgp == SGP_READ && !swap.val)) {
1104        *pagep = page;
1105        return 0;
1106    }
1107
1108    /*
1109     * Fast cache lookup did not find it:
1110     * bring it back from swap or allocate.
1111     */
1112    info = SHMEM_I(inode);
1113    sbinfo = SHMEM_SB(inode->i_sb);
1114
1115    if (swap.val) {
1116        /* Look it up and read it in.. */
1117        page = lookup_swap_cache(swap);
1118        if (!page) {
1119            /* here we actually do the io */
1120            if (fault_type)
1121                *fault_type |= VM_FAULT_MAJOR;
1122            page = shmem_swapin(swap, gfp, info, index);
1123            if (!page) {
1124                error = -ENOMEM;
1125                goto failed;
1126            }
1127        }
1128
1129        /* We have to do this with page locked to prevent races */
1130        lock_page(page);
1131        if (!PageSwapCache(page) || page_private(page) != swap.val ||
1132            !shmem_confirm_swap(mapping, index, swap)) {
1133            error = -EEXIST; /* try again */
1134            goto unlock;
1135        }
1136        if (!PageUptodate(page)) {
1137            error = -EIO;
1138            goto failed;
1139        }
1140        wait_on_page_writeback(page);
1141
1142        if (shmem_should_replace_page(page, gfp)) {
1143            error = shmem_replace_page(&page, gfp, info, index);
1144            if (error)
1145                goto failed;
1146        }
1147
1148        error = mem_cgroup_cache_charge(page, current->mm,
1149                        gfp & GFP_RECLAIM_MASK);
1150        if (!error) {
1151            error = shmem_add_to_page_cache(page, mapping, index,
1152                        gfp, swp_to_radix_entry(swap));
1153            /*
1154             * We already confirmed swap under page lock, and make
1155             * no memory allocation here, so usually no possibility
1156             * of error; but free_swap_and_cache() only trylocks a
1157             * page, so it is just possible that the entry has been
1158             * truncated or holepunched since swap was confirmed.
1159             * shmem_undo_range() will have done some of the
1160             * unaccounting, now delete_from_swap_cache() will do
1161             * the rest (including mem_cgroup_uncharge_swapcache).
1162             * Reset swap.val? No, leave it so "failed" goes back to
1163             * "repeat": reading a hole and writing should succeed.
1164             */
1165            if (error)
1166                delete_from_swap_cache(page);
1167        }
1168        if (error)
1169            goto failed;
1170
1171        spin_lock(&info->lock);
1172        info->swapped--;
1173        shmem_recalc_inode(inode);
1174        spin_unlock(&info->lock);
1175
1176        delete_from_swap_cache(page);
1177        set_page_dirty(page);
1178        swap_free(swap);
1179
1180    } else {
1181        if (shmem_acct_block(info->flags)) {
1182            error = -ENOSPC;
1183            goto failed;
1184        }
1185        if (sbinfo->max_blocks) {
1186            if (percpu_counter_compare(&sbinfo->used_blocks,
1187                        sbinfo->max_blocks) >= 0) {
1188                error = -ENOSPC;
1189                goto unacct;
1190            }
1191            percpu_counter_inc(&sbinfo->used_blocks);
1192        }
1193
1194        page = shmem_alloc_page(gfp, info, index);
1195        if (!page) {
1196            error = -ENOMEM;
1197            goto decused;
1198        }
1199
1200        SetPageSwapBacked(page);
1201        __set_page_locked(page);
1202        error = mem_cgroup_cache_charge(page, current->mm,
1203                        gfp & GFP_RECLAIM_MASK);
1204        if (error)
1205            goto decused;
1206        error = radix_tree_preload(gfp & GFP_RECLAIM_MASK);
1207        if (!error) {
1208            error = shmem_add_to_page_cache(page, mapping, index,
1209                            gfp, NULL);
1210            radix_tree_preload_end();
1211        }
1212        if (error) {
1213            mem_cgroup_uncharge_cache_page(page);
1214            goto decused;
1215        }
1216        lru_cache_add_anon(page);
1217
1218        spin_lock(&info->lock);
1219        info->alloced++;
1220        inode->i_blocks += BLOCKS_PER_PAGE;
1221        shmem_recalc_inode(inode);
1222        spin_unlock(&info->lock);
1223        alloced = true;
1224
1225        /*
1226         * Let SGP_FALLOC use the SGP_WRITE optimization on a new page.
1227         */
1228        if (sgp == SGP_FALLOC)
1229            sgp = SGP_WRITE;
1230clear:
1231        /*
1232         * Let SGP_WRITE caller clear ends if write does not fill page;
1233         * but SGP_FALLOC on a page fallocated earlier must initialize
1234         * it now, lest undo on failure cancel our earlier guarantee.
1235         */
1236        if (sgp != SGP_WRITE) {
1237            clear_highpage(page);
1238            flush_dcache_page(page);
1239            SetPageUptodate(page);
1240        }
1241        if (sgp == SGP_DIRTY)
1242            set_page_dirty(page);
1243    }
1244
1245    /* Perhaps the file has been truncated since we checked */
1246    if (sgp != SGP_WRITE && sgp != SGP_FALLOC &&
1247        ((loff_t)index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
1248        error = -EINVAL;
1249        if (alloced)
1250            goto trunc;
1251        else
1252            goto failed;
1253    }
1254    *pagep = page;
1255    return 0;
1256
1257    /*
1258     * Error recovery.
1259     */
1260trunc:
1261    info = SHMEM_I(inode);
1262    ClearPageDirty(page);
1263    delete_from_page_cache(page);
1264    spin_lock(&info->lock);
1265    info->alloced--;
1266    inode->i_blocks -= BLOCKS_PER_PAGE;
1267    spin_unlock(&info->lock);
1268decused:
1269    sbinfo = SHMEM_SB(inode->i_sb);
1270    if (sbinfo->max_blocks)
1271        percpu_counter_add(&sbinfo->used_blocks, -1);
1272unacct:
1273    shmem_unacct_blocks(info->flags, 1);
1274failed:
1275    if (swap.val && error != -EINVAL &&
1276        !shmem_confirm_swap(mapping, index, swap))
1277        error = -EEXIST;
1278unlock:
1279    if (page) {
1280        unlock_page(page);
1281        page_cache_release(page);
1282    }
1283    if (error == -ENOSPC && !once++) {
1284        info = SHMEM_I(inode);
1285        spin_lock(&info->lock);
1286        shmem_recalc_inode(inode);
1287        spin_unlock(&info->lock);
1288        goto repeat;
1289    }
1290    if (error == -EEXIST) /* from above or from radix_tree_insert */
1291        goto repeat;
1292    return error;
1293}
1294
1295static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1296{
1297    struct inode *inode = file_inode(vma->vm_file);
1298    int error;
1299    int ret = VM_FAULT_LOCKED;
1300
1301    error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret);
1302    if (error)
1303        return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1304
1305    if (ret & VM_FAULT_MAJOR) {
1306        count_vm_event(PGMAJFAULT);
1307        mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1308    }
1309    return ret;
1310}
1311
1312#ifdef CONFIG_NUMA
1313static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *mpol)
1314{
1315    struct inode *inode = file_inode(vma->vm_file);
1316    return mpol_set_shared_policy(&SHMEM_I(inode)->policy, vma, mpol);
1317}
1318
1319static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
1320                      unsigned long addr)
1321{
1322    struct inode *inode = file_inode(vma->vm_file);
1323    pgoff_t index;
1324
1325    index = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1326    return mpol_shared_policy_lookup(&SHMEM_I(inode)->policy, index);
1327}
1328#endif
1329
1330int shmem_lock(struct file *file, int lock, struct user_struct *user)
1331{
1332    struct inode *inode = file_inode(file);
1333    struct shmem_inode_info *info = SHMEM_I(inode);
1334    int retval = -ENOMEM;
1335
1336    spin_lock(&info->lock);
1337    if (lock && !(info->flags & VM_LOCKED)) {
1338        if (!user_shm_lock(inode->i_size, user))
1339            goto out_nomem;
1340        info->flags |= VM_LOCKED;
1341        mapping_set_unevictable(file->f_mapping);
1342    }
1343    if (!lock && (info->flags & VM_LOCKED) && user) {
1344        user_shm_unlock(inode->i_size, user);
1345        info->flags &= ~VM_LOCKED;
1346        mapping_clear_unevictable(file->f_mapping);
1347    }
1348    retval = 0;
1349
1350out_nomem:
1351    spin_unlock(&info->lock);
1352    return retval;
1353}
1354
1355static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1356{
1357    file_accessed(file);
1358    vma->vm_ops = &shmem_vm_ops;
1359    return 0;
1360}
1361
1362static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir,
1363                     umode_t mode, dev_t dev, unsigned long flags)
1364{
1365    struct inode *inode;
1366    struct shmem_inode_info *info;
1367    struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1368
1369    if (shmem_reserve_inode(sb))
1370        return NULL;
1371
1372    inode = new_inode(sb);
1373    if (inode) {
1374        inode->i_ino = get_next_ino();
1375        inode_init_owner(inode, dir, mode);
1376        inode->i_blocks = 0;
1377        inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1378        inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1379        inode->i_generation = get_seconds();
1380        info = SHMEM_I(inode);
1381        memset(info, 0, (char *)inode - (char *)info);
1382        spin_lock_init(&info->lock);
1383        info->flags = flags & VM_NORESERVE;
1384        INIT_LIST_HEAD(&info->swaplist);
1385        simple_xattrs_init(&info->xattrs);
1386        cache_no_acl(inode);
1387
1388        switch (mode & S_IFMT) {
1389        default:
1390            inode->i_op = &shmem_special_inode_operations;
1391            init_special_inode(inode, mode, dev);
1392            break;
1393        case S_IFREG:
1394            inode->i_mapping->a_ops = &shmem_aops;
1395            inode->i_op = &shmem_inode_operations;
1396            inode->i_fop = &shmem_file_operations;
1397            mpol_shared_policy_init(&info->policy,
1398                         shmem_get_sbmpol(sbinfo));
1399            break;
1400        case S_IFDIR:
1401            inc_nlink(inode);
1402            /* Some things misbehave if size == 0 on a directory */
1403            inode->i_size = 2 * BOGO_DIRENT_SIZE;
1404            inode->i_op = &shmem_dir_inode_operations;
1405            inode->i_fop = &simple_dir_operations;
1406            break;
1407        case S_IFLNK:
1408            /*
1409             * Must not load anything in the rbtree,
1410             * mpol_free_shared_policy will not be called.
1411             */
1412            mpol_shared_policy_init(&info->policy, NULL);
1413            break;
1414        }
1415    } else
1416        shmem_free_inode(sb);
1417    return inode;
1418}
1419
1420#ifdef CONFIG_TMPFS
1421static const struct inode_operations shmem_symlink_inode_operations;
1422static const struct inode_operations shmem_short_symlink_operations;
1423
1424#ifdef CONFIG_TMPFS_XATTR
1425static int shmem_initxattrs(struct inode *, const struct xattr *, void *);
1426#else
1427#define shmem_initxattrs NULL
1428#endif
1429
1430static int
1431shmem_write_begin(struct file *file, struct address_space *mapping,
1432            loff_t pos, unsigned len, unsigned flags,
1433            struct page **pagep, void **fsdata)
1434{
1435    struct inode *inode = mapping->host;
1436    pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1437    return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
1438}
1439
1440static int
1441shmem_write_end(struct file *file, struct address_space *mapping,
1442            loff_t pos, unsigned len, unsigned copied,
1443            struct page *page, void *fsdata)
1444{
1445    struct inode *inode = mapping->host;
1446
1447    if (pos + copied > inode->i_size)
1448        i_size_write(inode, pos + copied);
1449
1450    if (!PageUptodate(page)) {
1451        if (copied < PAGE_CACHE_SIZE) {
1452            unsigned from = pos & (PAGE_CACHE_SIZE - 1);
1453            zero_user_segments(page, 0, from,
1454                    from + copied, PAGE_CACHE_SIZE);
1455        }
1456        SetPageUptodate(page);
1457    }
1458    set_page_dirty(page);
1459    unlock_page(page);
1460    page_cache_release(page);
1461
1462    return copied;
1463}
1464
1465static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
1466{
1467    struct inode *inode = file_inode(filp);
1468    struct address_space *mapping = inode->i_mapping;
1469    pgoff_t index;
1470    unsigned long offset;
1471    enum sgp_type sgp = SGP_READ;
1472
1473    /*
1474     * Might this read be for a stacking filesystem? Then when reading
1475     * holes of a sparse file, we actually need to allocate those pages,
1476     * and even mark them dirty, so it cannot exceed the max_blocks limit.
1477     */
1478    if (segment_eq(get_fs(), KERNEL_DS))
1479        sgp = SGP_DIRTY;
1480
1481    index = *ppos >> PAGE_CACHE_SHIFT;
1482    offset = *ppos & ~PAGE_CACHE_MASK;
1483
1484    for (;;) {
1485        struct page *page = NULL;
1486        pgoff_t end_index;
1487        unsigned long nr, ret;
1488        loff_t i_size = i_size_read(inode);
1489
1490        end_index = i_size >> PAGE_CACHE_SHIFT;
1491        if (index > end_index)
1492            break;
1493        if (index == end_index) {
1494            nr = i_size & ~PAGE_CACHE_MASK;
1495            if (nr <= offset)
1496                break;
1497        }
1498
1499        desc->error = shmem_getpage(inode, index, &page, sgp, NULL);
1500        if (desc->error) {
1501            if (desc->error == -EINVAL)
1502                desc->error = 0;
1503            break;
1504        }
1505        if (page)
1506            unlock_page(page);
1507
1508        /*
1509         * We must evaluate after, since reads (unlike writes)
1510         * are called without i_mutex protection against truncate
1511         */
1512        nr = PAGE_CACHE_SIZE;
1513        i_size = i_size_read(inode);
1514        end_index = i_size >> PAGE_CACHE_SHIFT;
1515        if (index == end_index) {
1516            nr = i_size & ~PAGE_CACHE_MASK;
1517            if (nr <= offset) {
1518                if (page)
1519                    page_cache_release(page);
1520                break;
1521            }
1522        }
1523        nr -= offset;
1524
1525        if (page) {
1526            /*
1527             * If users can be writing to this page using arbitrary
1528             * virtual addresses, take care about potential aliasing
1529             * before reading the page on the kernel side.
1530             */
1531            if (mapping_writably_mapped(mapping))
1532                flush_dcache_page(page);
1533            /*
1534             * Mark the page accessed if we read the beginning.
1535             */
1536            if (!offset)
1537                mark_page_accessed(page);
1538        } else {
1539            page = ZERO_PAGE(0);
1540            page_cache_get(page);
1541        }
1542
1543        /*
1544         * Ok, we have the page, and it's up-to-date, so
1545         * now we can copy it to user space...
1546         *
1547         * The actor routine returns how many bytes were actually used..
1548         * NOTE! This may not be the same as how much of a user buffer
1549         * we filled up (we may be padding etc), so we can only update
1550         * "pos" here (the actor routine has to update the user buffer
1551         * pointers and the remaining count).
1552         */
1553        ret = actor(desc, page, offset, nr);
1554        offset += ret;
1555        index += offset >> PAGE_CACHE_SHIFT;
1556        offset &= ~PAGE_CACHE_MASK;
1557
1558        page_cache_release(page);
1559        if (ret != nr || !desc->count)
1560            break;
1561
1562        cond_resched();
1563    }
1564
1565    *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1566    file_accessed(filp);
1567}
1568
1569static ssize_t shmem_file_aio_read(struct kiocb *iocb,
1570        const struct iovec *iov, unsigned long nr_segs, loff_t pos)
1571{
1572    struct file *filp = iocb->ki_filp;
1573    ssize_t retval;
1574    unsigned long seg;
1575    size_t count;
1576    loff_t *ppos = &iocb->ki_pos;
1577
1578    retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1579    if (retval)
1580        return retval;
1581
1582    for (seg = 0; seg < nr_segs; seg++) {
1583        read_descriptor_t desc;
1584
1585        desc.written = 0;
1586        desc.arg.buf = iov[seg].iov_base;
1587        desc.count = iov[seg].iov_len;
1588        if (desc.count == 0)
1589            continue;
1590        desc.error = 0;
1591        do_shmem_file_read(filp, ppos, &desc, file_read_actor);
1592        retval += desc.written;
1593        if (desc.error) {
1594            retval = retval ?: desc.error;
1595            break;
1596        }
1597        if (desc.count > 0)
1598            break;
1599    }
1600    return retval;
1601}
1602
1603static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
1604                struct pipe_inode_info *pipe, size_t len,
1605                unsigned int flags)
1606{
1607    struct address_space *mapping = in->f_mapping;
1608    struct inode *inode = mapping->host;
1609    unsigned int loff, nr_pages, req_pages;
1610    struct page *pages[PIPE_DEF_BUFFERS];
1611    struct partial_page partial[PIPE_DEF_BUFFERS];
1612    struct page *page;
1613    pgoff_t index, end_index;
1614    loff_t isize, left;
1615    int error, page_nr;
1616    struct splice_pipe_desc spd = {
1617        .pages = pages,
1618        .partial = partial,
1619        .nr_pages_max = PIPE_DEF_BUFFERS,
1620        .flags = flags,
1621        .ops = &page_cache_pipe_buf_ops,
1622        .spd_release = spd_release_page,
1623    };
1624
1625    isize = i_size_read(inode);
1626    if (unlikely(*ppos >= isize))
1627        return 0;
1628
1629    left = isize - *ppos;
1630    if (unlikely(left < len))
1631        len = left;
1632
1633    if (splice_grow_spd(pipe, &spd))
1634        return -ENOMEM;
1635
1636    index = *ppos >> PAGE_CACHE_SHIFT;
1637    loff = *ppos & ~PAGE_CACHE_MASK;
1638    req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1639    nr_pages = min(req_pages, pipe->buffers);
1640
1641    spd.nr_pages = find_get_pages_contig(mapping, index,
1642                        nr_pages, spd.pages);
1643    index += spd.nr_pages;
1644    error = 0;
1645
1646    while (spd.nr_pages < nr_pages) {
1647        error = shmem_getpage(inode, index, &page, SGP_CACHE, NULL);
1648        if (error)
1649            break;
1650        unlock_page(page);
1651        spd.pages[spd.nr_pages++] = page;
1652        index++;
1653    }
1654
1655    index = *ppos >> PAGE_CACHE_SHIFT;
1656    nr_pages = spd.nr_pages;
1657    spd.nr_pages = 0;
1658
1659    for (page_nr = 0; page_nr < nr_pages; page_nr++) {
1660        unsigned int this_len;
1661
1662        if (!len)
1663            break;
1664
1665        this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
1666        page = spd.pages[page_nr];
1667
1668        if (!PageUptodate(page) || page->mapping != mapping) {
1669            error = shmem_getpage(inode, index, &page,
1670                            SGP_CACHE, NULL);
1671            if (error)
1672                break;
1673            unlock_page(page);
1674            page_cache_release(spd.pages[page_nr]);
1675            spd.pages[page_nr] = page;
1676        }
1677
1678        isize = i_size_read(inode);
1679        end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1680        if (unlikely(!isize || index > end_index))
1681            break;
1682
1683        if (end_index == index) {
1684            unsigned int plen;
1685
1686            plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1687            if (plen <= loff)
1688                break;
1689
1690            this_len = min(this_len, plen - loff);
1691            len = this_len;
1692        }
1693
1694        spd.partial[page_nr].offset = loff;
1695        spd.partial[page_nr].len = this_len;
1696        len -= this_len;
1697        loff = 0;
1698        spd.nr_pages++;
1699        index++;
1700    }
1701
1702    while (page_nr < nr_pages)
1703        page_cache_release(spd.pages[page_nr++]);
1704
1705    if (spd.nr_pages)
1706        error = splice_to_pipe(pipe, &spd);
1707
1708    splice_shrink_spd(&spd);
1709
1710    if (error > 0) {
1711        *ppos += error;
1712        file_accessed(in);
1713    }
1714    return error;
1715}
1716
1717/*
1718 * llseek SEEK_DATA or SEEK_HOLE through the radix_tree.
1719 */
1720static pgoff_t shmem_seek_hole_data(struct address_space *mapping,
1721                    pgoff_t index, pgoff_t end, int whence)
1722{
1723    struct page *page;
1724    struct pagevec pvec;
1725    pgoff_t indices[PAGEVEC_SIZE];
1726    bool done = false;
1727    int i;
1728
1729    pagevec_init(&pvec, 0);
1730    pvec.nr = 1; /* start small: we may be there already */
1731    while (!done) {
1732        pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
1733                    pvec.nr, pvec.pages, indices);
1734        if (!pvec.nr) {
1735            if (whence == SEEK_DATA)
1736                index = end;
1737            break;
1738        }
1739        for (i = 0; i < pvec.nr; i++, index++) {
1740            if (index < indices[i]) {
1741                if (whence == SEEK_HOLE) {
1742                    done = true;
1743                    break;
1744                }
1745                index = indices[i];
1746            }
1747            page = pvec.pages[i];
1748            if (page && !radix_tree_exceptional_entry(page)) {
1749                if (!PageUptodate(page))
1750                    page = NULL;
1751            }
1752            if (index >= end ||
1753                (page && whence == SEEK_DATA) ||
1754                (!page && whence == SEEK_HOLE)) {
1755                done = true;
1756                break;
1757            }
1758        }
1759        shmem_deswap_pagevec(&pvec);
1760        pagevec_release(&pvec);
1761        pvec.nr = PAGEVEC_SIZE;
1762        cond_resched();
1763    }
1764    return index;
1765}
1766
1767static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence)
1768{
1769    struct address_space *mapping = file->f_mapping;
1770    struct inode *inode = mapping->host;
1771    pgoff_t start, end;
1772    loff_t new_offset;
1773
1774    if (whence != SEEK_DATA && whence != SEEK_HOLE)
1775        return generic_file_llseek_size(file, offset, whence,
1776                    MAX_LFS_FILESIZE, i_size_read(inode));
1777    mutex_lock(&inode->i_mutex);
1778    /* We're holding i_mutex so we can access i_size directly */
1779
1780    if (offset < 0)
1781        offset = -EINVAL;
1782    else if (offset >= inode->i_size)
1783        offset = -ENXIO;
1784    else {
1785        start = offset >> PAGE_CACHE_SHIFT;
1786        end = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1787        new_offset = shmem_seek_hole_data(mapping, start, end, whence);
1788        new_offset <<= PAGE_CACHE_SHIFT;
1789        if (new_offset > offset) {
1790            if (new_offset < inode->i_size)
1791                offset = new_offset;
1792            else if (whence == SEEK_DATA)
1793                offset = -ENXIO;
1794            else
1795                offset = inode->i_size;
1796        }
1797    }
1798
1799    if (offset >= 0 && offset != file->f_pos) {
1800        file->f_pos = offset;
1801        file->f_version = 0;
1802    }
1803    mutex_unlock(&inode->i_mutex);
1804    return offset;
1805}
1806
1807static long shmem_fallocate(struct file *file, int mode, loff_t offset,
1808                             loff_t len)
1809{
1810    struct inode *inode = file_inode(file);
1811    struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
1812    struct shmem_falloc shmem_falloc;
1813    pgoff_t start, index, end;
1814    int error;
1815
1816    mutex_lock(&inode->i_mutex);
1817
1818    if (mode & FALLOC_FL_PUNCH_HOLE) {
1819        struct address_space *mapping = file->f_mapping;
1820        loff_t unmap_start = round_up(offset, PAGE_SIZE);
1821        loff_t unmap_end = round_down(offset + len, PAGE_SIZE) - 1;
1822
1823        if ((u64)unmap_end > (u64)unmap_start)
1824            unmap_mapping_range(mapping, unmap_start,
1825                        1 + unmap_end - unmap_start, 0);
1826        shmem_truncate_range(inode, offset, offset + len - 1);
1827        /* No need to unmap again: hole-punching leaves COWed pages */
1828        error = 0;
1829        goto out;
1830    }
1831
1832    /* We need to check rlimit even when FALLOC_FL_KEEP_SIZE */
1833    error = inode_newsize_ok(inode, offset + len);
1834    if (error)
1835        goto out;
1836
1837    start = offset >> PAGE_CACHE_SHIFT;
1838    end = (offset + len + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1839    /* Try to avoid a swapstorm if len is impossible to satisfy */
1840    if (sbinfo->max_blocks && end - start > sbinfo->max_blocks) {
1841        error = -ENOSPC;
1842        goto out;
1843    }
1844
1845    shmem_falloc.start = start;
1846    shmem_falloc.next = start;
1847    shmem_falloc.nr_falloced = 0;
1848    shmem_falloc.nr_unswapped = 0;
1849    spin_lock(&inode->i_lock);
1850    inode->i_private = &shmem_falloc;
1851    spin_unlock(&inode->i_lock);
1852
1853    for (index = start; index < end; index++) {
1854        struct page *page;
1855
1856        /*
1857         * Good, the fallocate(2) manpage permits EINTR: we may have
1858         * been interrupted because we are using up too much memory.
1859         */
1860        if (signal_pending(current))
1861            error = -EINTR;
1862        else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
1863            error = -ENOMEM;
1864        else
1865            error = shmem_getpage(inode, index, &page, SGP_FALLOC,
1866                                    NULL);
1867        if (error) {
1868            /* Remove the !PageUptodate pages we added */
1869            shmem_undo_range(inode,
1870                (loff_t)start << PAGE_CACHE_SHIFT,
1871                (loff_t)index << PAGE_CACHE_SHIFT, true);
1872            goto undone;
1873        }
1874
1875        /*
1876         * Inform shmem_writepage() how far we have reached.
1877         * No need for lock or barrier: we have the page lock.
1878         */
1879        shmem_falloc.next++;
1880        if (!PageUptodate(page))
1881            shmem_falloc.nr_falloced++;
1882
1883        /*
1884         * If !PageUptodate, leave it that way so that freeable pages
1885         * can be recognized if we need to rollback on error later.
1886         * But set_page_dirty so that memory pressure will swap rather
1887         * than free the pages we are allocating (and SGP_CACHE pages
1888         * might still be clean: we now need to mark those dirty too).
1889         */
1890        set_page_dirty(page);
1891        unlock_page(page);
1892        page_cache_release(page);
1893        cond_resched();
1894    }
1895
1896    if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
1897        i_size_write(inode, offset + len);
1898    inode->i_ctime = CURRENT_TIME;
1899undone:
1900    spin_lock(&inode->i_lock);
1901    inode->i_private = NULL;
1902    spin_unlock(&inode->i_lock);
1903out:
1904    mutex_unlock(&inode->i_mutex);
1905    return error;
1906}
1907
1908static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
1909{
1910    struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
1911
1912    buf->f_type = TMPFS_MAGIC;
1913    buf->f_bsize = PAGE_CACHE_SIZE;
1914    buf->f_namelen = NAME_MAX;
1915    if (sbinfo->max_blocks) {
1916        buf->f_blocks = sbinfo->max_blocks;
1917        buf->f_bavail =
1918        buf->f_bfree = sbinfo->max_blocks -
1919                percpu_counter_sum(&sbinfo->used_blocks);
1920    }
1921    if (sbinfo->max_inodes) {
1922        buf->f_files = sbinfo->max_inodes;
1923        buf->f_ffree = sbinfo->free_inodes;
1924    }
1925    /* else leave those fields 0 like simple_statfs */
1926    return 0;
1927}
1928
1929/*
1930 * File creation. Allocate an inode, and we're done..
1931 */
1932static int
1933shmem_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
1934{
1935    struct inode *inode;
1936    int error = -ENOSPC;
1937
1938    inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
1939    if (inode) {
1940        error = security_inode_init_security(inode, dir,
1941                             &dentry->d_name,
1942                             shmem_initxattrs, NULL);
1943        if (error) {
1944            if (error != -EOPNOTSUPP) {
1945                iput(inode);
1946                return error;
1947            }
1948        }
1949#ifdef CONFIG_TMPFS_POSIX_ACL
1950        error = generic_acl_init(inode, dir);
1951        if (error) {
1952            iput(inode);
1953            return error;
1954        }
1955#else
1956        error = 0;
1957#endif
1958        dir->i_size += BOGO_DIRENT_SIZE;
1959        dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1960        d_instantiate(dentry, inode);
1961        dget(dentry); /* Extra count - pin the dentry in core */
1962    }
1963    return error;
1964}
1965
1966static int shmem_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
1967{
1968    int error;
1969
1970    if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
1971        return error;
1972    inc_nlink(dir);
1973    return 0;
1974}
1975
1976static int shmem_create(struct inode *dir, struct dentry *dentry, umode_t mode,
1977        bool excl)
1978{
1979    return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
1980}
1981
1982/*
1983 * Link a file..
1984 */
1985static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
1986{
1987    struct inode *inode = old_dentry->d_inode;
1988    int ret;
1989
1990    /*
1991     * No ordinary (disk based) filesystem counts links as inodes;
1992     * but each new link needs a new dentry, pinning lowmem, and
1993     * tmpfs dentries cannot be pruned until they are unlinked.
1994     */
1995    ret = shmem_reserve_inode(inode->i_sb);
1996    if (ret)
1997        goto out;
1998
1999    dir->i_size += BOGO_DIRENT_SIZE;
2000    inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2001    inc_nlink(inode);
2002    ihold(inode); /* New dentry reference */
2003    dget(dentry); /* Extra pinning count for the created dentry */
2004    d_instantiate(dentry, inode);
2005out:
2006    return ret;
2007}
2008
2009static int shmem_unlink(struct inode *dir, struct dentry *dentry)
2010{
2011    struct inode *inode = dentry->d_inode;
2012
2013    if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
2014        shmem_free_inode(inode->i_sb);
2015
2016    dir->i_size -= BOGO_DIRENT_SIZE;
2017    inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2018    drop_nlink(inode);
2019    dput(dentry); /* Undo the count from "create" - this does all the work */
2020    return 0;
2021}
2022
2023static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
2024{
2025    if (!simple_empty(dentry))
2026        return -ENOTEMPTY;
2027
2028    drop_nlink(dentry->d_inode);
2029    drop_nlink(dir);
2030    return shmem_unlink(dir, dentry);
2031}
2032
2033/*
2034 * The VFS layer already does all the dentry stuff for rename,
2035 * we just have to decrement the usage count for the target if
2036 * it exists so that the VFS layer correctly free's it when it
2037 * gets overwritten.
2038 */
2039static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
2040{
2041    struct inode *inode = old_dentry->d_inode;
2042    int they_are_dirs = S_ISDIR(inode->i_mode);
2043
2044    if (!simple_empty(new_dentry))
2045        return -ENOTEMPTY;
2046
2047    if (new_dentry->d_inode) {
2048        (void) shmem_unlink(new_dir, new_dentry);
2049        if (they_are_dirs)
2050            drop_nlink(old_dir);
2051    } else if (they_are_dirs) {
2052        drop_nlink(old_dir);
2053        inc_nlink(new_dir);
2054    }
2055
2056    old_dir->i_size -= BOGO_DIRENT_SIZE;
2057    new_dir->i_size += BOGO_DIRENT_SIZE;
2058    old_dir->i_ctime = old_dir->i_mtime =
2059    new_dir->i_ctime = new_dir->i_mtime =
2060    inode->i_ctime = CURRENT_TIME;
2061    return 0;
2062}
2063
2064static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
2065{
2066    int error;
2067    int len;
2068    struct inode *inode;
2069    struct page *page;
2070    char *kaddr;
2071    struct shmem_inode_info *info;
2072
2073    len = strlen(symname) + 1;
2074    if (len > PAGE_CACHE_SIZE)
2075        return -ENAMETOOLONG;
2076
2077    inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0, VM_NORESERVE);
2078    if (!inode)
2079        return -ENOSPC;
2080
2081    error = security_inode_init_security(inode, dir, &dentry->d_name,
2082                         shmem_initxattrs, NULL);
2083    if (error) {
2084        if (error != -EOPNOTSUPP) {
2085            iput(inode);
2086            return error;
2087        }
2088        error = 0;
2089    }
2090
2091    info = SHMEM_I(inode);
2092    inode->i_size = len-1;
2093    if (len <= SHORT_SYMLINK_LEN) {
2094        info->symlink = kmemdup(symname, len, GFP_KERNEL);
2095        if (!info->symlink) {
2096            iput(inode);
2097            return -ENOMEM;
2098        }
2099        inode->i_op = &shmem_short_symlink_operations;
2100    } else {
2101        error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
2102        if (error) {
2103            iput(inode);
2104            return error;
2105        }
2106        inode->i_mapping->a_ops = &shmem_aops;
2107        inode->i_op = &shmem_symlink_inode_operations;
2108        kaddr = kmap_atomic(page);
2109        memcpy(kaddr, symname, len);
2110        kunmap_atomic(kaddr);
2111        SetPageUptodate(page);
2112        set_page_dirty(page);
2113        unlock_page(page);
2114        page_cache_release(page);
2115    }
2116    dir->i_size += BOGO_DIRENT_SIZE;
2117    dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2118    d_instantiate(dentry, inode);
2119    dget(dentry);
2120    return 0;
2121}
2122
2123static void *shmem_follow_short_symlink(struct dentry *dentry, struct nameidata *nd)
2124{
2125    nd_set_link(nd, SHMEM_I(dentry->d_inode)->symlink);
2126    return NULL;
2127}
2128
2129static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
2130{
2131    struct page *page = NULL;
2132    int error = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
2133    nd_set_link(nd, error ? ERR_PTR(error) : kmap(page));
2134    if (page)
2135        unlock_page(page);
2136    return page;
2137}
2138
2139static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
2140{
2141    if (!IS_ERR(nd_get_link(nd))) {
2142        struct page *page = cookie;
2143        kunmap(page);
2144        mark_page_accessed(page);
2145        page_cache_release(page);
2146    }
2147}
2148
2149#ifdef CONFIG_TMPFS_XATTR
2150/*
2151 * Superblocks without xattr inode operations may get some security.* xattr
2152 * support from the LSM "for free". As soon as we have any other xattrs
2153 * like ACLs, we also need to implement the security.* handlers at
2154 * filesystem level, though.
2155 */
2156
2157/*
2158 * Callback for security_inode_init_security() for acquiring xattrs.
2159 */
2160static int shmem_initxattrs(struct inode *inode,
2161                const struct xattr *xattr_array,
2162                void *fs_info)
2163{
2164    struct shmem_inode_info *info = SHMEM_I(inode);
2165    const struct xattr *xattr;
2166    struct simple_xattr *new_xattr;
2167    size_t len;
2168
2169    for (xattr = xattr_array; xattr->name != NULL; xattr++) {
2170        new_xattr = simple_xattr_alloc(xattr->value, xattr->value_len);
2171        if (!new_xattr)
2172            return -ENOMEM;
2173
2174        len = strlen(xattr->name) + 1;
2175        new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
2176                      GFP_KERNEL);
2177        if (!new_xattr->name) {
2178            kfree(new_xattr);
2179            return -ENOMEM;
2180        }
2181
2182        memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
2183               XATTR_SECURITY_PREFIX_LEN);
2184        memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
2185               xattr->name, len);
2186
2187        simple_xattr_list_add(&info->xattrs, new_xattr);
2188    }
2189
2190    return 0;
2191}
2192
2193static const struct xattr_handler *shmem_xattr_handlers[] = {
2194#ifdef CONFIG_TMPFS_POSIX_ACL
2195    &generic_acl_access_handler,
2196    &generic_acl_default_handler,
2197#endif
2198    NULL
2199};
2200
2201static int shmem_xattr_validate(const char *name)
2202{
2203    struct { const char *prefix; size_t len; } arr[] = {
2204        { XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN },
2205        { XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN }
2206    };
2207    int i;
2208
2209    for (i = 0; i < ARRAY_SIZE(arr); i++) {
2210        size_t preflen = arr[i].len;
2211        if (strncmp(name, arr[i].prefix, preflen) == 0) {
2212            if (!name[preflen])
2213                return -EINVAL;
2214            return 0;
2215        }
2216    }
2217    return -EOPNOTSUPP;
2218}
2219
2220static ssize_t shmem_getxattr(struct dentry *dentry, const char *name,
2221                  void *buffer, size_t size)
2222{
2223    struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2224    int err;
2225
2226    /*
2227     * If this is a request for a synthetic attribute in the system.*
2228     * namespace use the generic infrastructure to resolve a handler
2229     * for it via sb->s_xattr.
2230     */
2231    if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2232        return generic_getxattr(dentry, name, buffer, size);
2233
2234    err = shmem_xattr_validate(name);
2235    if (err)
2236        return err;
2237
2238    return simple_xattr_get(&info->xattrs, name, buffer, size);
2239}
2240
2241static int shmem_setxattr(struct dentry *dentry, const char *name,
2242              const void *value, size_t size, int flags)
2243{
2244    struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2245    int err;
2246
2247    /*
2248     * If this is a request for a synthetic attribute in the system.*
2249     * namespace use the generic infrastructure to resolve a handler
2250     * for it via sb->s_xattr.
2251     */
2252    if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2253        return generic_setxattr(dentry, name, value, size, flags);
2254
2255    err = shmem_xattr_validate(name);
2256    if (err)
2257        return err;
2258
2259    return simple_xattr_set(&info->xattrs, name, value, size, flags);
2260}
2261
2262static int shmem_removexattr(struct dentry *dentry, const char *name)
2263{
2264    struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2265    int err;
2266
2267    /*
2268     * If this is a request for a synthetic attribute in the system.*
2269     * namespace use the generic infrastructure to resolve a handler
2270     * for it via sb->s_xattr.
2271     */
2272    if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
2273        return generic_removexattr(dentry, name);
2274
2275    err = shmem_xattr_validate(name);
2276    if (err)
2277        return err;
2278
2279    return simple_xattr_remove(&info->xattrs, name);
2280}
2281
2282static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
2283{
2284    struct shmem_inode_info *info = SHMEM_I(dentry->d_inode);
2285    return simple_xattr_list(&info->xattrs, buffer, size);
2286}
2287#endif /* CONFIG_TMPFS_XATTR */
2288
2289static const struct inode_operations shmem_short_symlink_operations = {
2290    .readlink = generic_readlink,
2291    .follow_link = shmem_follow_short_symlink,
2292#ifdef CONFIG_TMPFS_XATTR
2293    .setxattr = shmem_setxattr,
2294    .getxattr = shmem_getxattr,
2295    .listxattr = shmem_listxattr,
2296    .removexattr = shmem_removexattr,
2297#endif
2298};
2299
2300static const struct inode_operations shmem_symlink_inode_operations = {
2301    .readlink = generic_readlink,
2302    .follow_link = shmem_follow_link,
2303    .put_link = shmem_put_link,
2304#ifdef CONFIG_TMPFS_XATTR
2305    .setxattr = shmem_setxattr,
2306    .getxattr = shmem_getxattr,
2307    .listxattr = shmem_listxattr,
2308    .removexattr = shmem_removexattr,
2309#endif
2310};
2311
2312static struct dentry *shmem_get_parent(struct dentry *child)
2313{
2314    return ERR_PTR(-ESTALE);
2315}
2316
2317static int shmem_match(struct inode *ino, void *vfh)
2318{
2319    __u32 *fh = vfh;
2320    __u64 inum = fh[2];
2321    inum = (inum << 32) | fh[1];
2322    return ino->i_ino == inum && fh[0] == ino->i_generation;
2323}
2324
2325static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
2326        struct fid *fid, int fh_len, int fh_type)
2327{
2328    struct inode *inode;
2329    struct dentry *dentry = NULL;
2330    u64 inum;
2331
2332    if (fh_len < 3)
2333        return NULL;
2334
2335    inum = fid->raw[2];
2336    inum = (inum << 32) | fid->raw[1];
2337
2338    inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
2339            shmem_match, fid->raw);
2340    if (inode) {
2341        dentry = d_find_alias(inode);
2342        iput(inode);
2343    }
2344
2345    return dentry;
2346}
2347
2348static int shmem_encode_fh(struct inode *inode, __u32 *fh, int *len,
2349                struct inode *parent)
2350{
2351    if (*len < 3) {
2352        *len = 3;
2353        return FILEID_INVALID;
2354    }
2355
2356    if (inode_unhashed(inode)) {
2357        /* Unfortunately insert_inode_hash is not idempotent,
2358         * so as we hash inodes here rather than at creation
2359         * time, we need a lock to ensure we only try
2360         * to do it once
2361         */
2362        static DEFINE_SPINLOCK(lock);
2363        spin_lock(&lock);
2364        if (inode_unhashed(inode))
2365            __insert_inode_hash(inode,
2366                        inode->i_ino + inode->i_generation);
2367        spin_unlock(&lock);
2368    }
2369
2370    fh[0] = inode->i_generation;
2371    fh[1] = inode->i_ino;
2372    fh[2] = ((__u64)inode->i_ino) >> 32;
2373
2374    *len = 3;
2375    return 1;
2376}
2377
2378static const struct export_operations shmem_export_ops = {
2379    .get_parent = shmem_get_parent,
2380    .encode_fh = shmem_encode_fh,
2381    .fh_to_dentry = shmem_fh_to_dentry,
2382};
2383
2384static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
2385                   bool remount)
2386{
2387    char *this_char, *value, *rest;
2388    struct mempolicy *mpol = NULL;
2389    uid_t uid;
2390    gid_t gid;
2391
2392    while (options != NULL) {
2393        this_char = options;
2394        for (;;) {
2395            /*
2396             * NUL-terminate this option: unfortunately,
2397             * mount options form a comma-separated list,
2398             * but mpol's nodelist may also contain commas.
2399             */
2400            options = strchr(options, ',');
2401            if (options == NULL)
2402                break;
2403            options++;
2404            if (!isdigit(*options)) {
2405                options[-1] = '\0';
2406                break;
2407            }
2408        }
2409        if (!*this_char)
2410            continue;
2411        if ((value = strchr(this_char,'=')) != NULL) {
2412            *value++ = 0;
2413        } else {
2414            printk(KERN_ERR
2415                "tmpfs: No value for mount option '%s'\n",
2416                this_char);
2417            goto error;
2418        }
2419
2420        if (!strcmp(this_char,"size")) {
2421            unsigned long long size;
2422            size = memparse(value,&rest);
2423            if (*rest == '%') {
2424                size <<= PAGE_SHIFT;
2425                size *= totalram_pages;
2426                do_div(size, 100);
2427                rest++;
2428            }
2429            if (*rest)
2430                goto bad_val;
2431            sbinfo->max_blocks =
2432                DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
2433        } else if (!strcmp(this_char,"nr_blocks")) {
2434            sbinfo->max_blocks = memparse(value, &rest);
2435            if (*rest)
2436                goto bad_val;
2437        } else if (!strcmp(this_char,"nr_inodes")) {
2438            sbinfo->max_inodes = memparse(value, &rest);
2439            if (*rest)
2440                goto bad_val;
2441        } else if (!strcmp(this_char,"mode")) {
2442            if (remount)
2443                continue;
2444            sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
2445            if (*rest)
2446                goto bad_val;
2447        } else if (!strcmp(this_char,"uid")) {
2448            if (remount)
2449                continue;
2450            uid = simple_strtoul(value, &rest, 0);
2451            if (*rest)
2452                goto bad_val;
2453            sbinfo->uid = make_kuid(current_user_ns(), uid);
2454            if (!uid_valid(sbinfo->uid))
2455                goto bad_val;
2456        } else if (!strcmp(this_char,"gid")) {
2457            if (remount)
2458                continue;
2459            gid = simple_strtoul(value, &rest, 0);
2460            if (*rest)
2461                goto bad_val;
2462            sbinfo->gid = make_kgid(current_user_ns(), gid);
2463            if (!gid_valid(sbinfo->gid))
2464                goto bad_val;
2465        } else if (!strcmp(this_char,"mpol")) {
2466            mpol_put(mpol);
2467            mpol = NULL;
2468            if (mpol_parse_str(value, &mpol))
2469                goto bad_val;
2470        } else {
2471            printk(KERN_ERR "tmpfs: Bad mount option %s\n",
2472                   this_char);
2473            goto error;
2474        }
2475    }
2476    sbinfo->mpol = mpol;
2477    return 0;
2478
2479bad_val:
2480    printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
2481           value, this_char);
2482error:
2483    mpol_put(mpol);
2484    return 1;
2485
2486}
2487
2488static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2489{
2490    struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2491    struct shmem_sb_info config = *sbinfo;
2492    unsigned long inodes;
2493    int error = -EINVAL;
2494
2495    config.mpol = NULL;
2496    if (shmem_parse_options(data, &config, true))
2497        return error;
2498
2499    spin_lock(&sbinfo->stat_lock);
2500    inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2501    if (percpu_counter_compare(&sbinfo->used_blocks, config.max_blocks) > 0)
2502        goto out;
2503    if (config.max_inodes < inodes)
2504        goto out;
2505    /*
2506     * Those tests disallow limited->unlimited while any are in use;
2507     * but we must separately disallow unlimited->limited, because
2508     * in that case we have no record of how much is already in use.
2509     */
2510    if (config.max_blocks && !sbinfo->max_blocks)
2511        goto out;
2512    if (config.max_inodes && !sbinfo->max_inodes)
2513        goto out;
2514
2515    error = 0;
2516    sbinfo->max_blocks = config.max_blocks;
2517    sbinfo->max_inodes = config.max_inodes;
2518    sbinfo->free_inodes = config.max_inodes - inodes;
2519
2520    /*
2521     * Preserve previous mempolicy unless mpol remount option was specified.
2522     */
2523    if (config.mpol) {
2524        mpol_put(sbinfo->mpol);
2525        sbinfo->mpol = config.mpol; /* transfers initial ref */
2526    }
2527out:
2528    spin_unlock(&sbinfo->stat_lock);
2529    return error;
2530}
2531
2532static int shmem_show_options(struct seq_file *seq, struct dentry *root)
2533{
2534    struct shmem_sb_info *sbinfo = SHMEM_SB(root->d_sb);
2535
2536    if (sbinfo->max_blocks != shmem_default_max_blocks())
2537        seq_printf(seq, ",size=%luk",
2538            sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10));
2539    if (sbinfo->max_inodes != shmem_default_max_inodes())
2540        seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
2541    if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
2542        seq_printf(seq, ",mode=%03ho", sbinfo->mode);
2543    if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID))
2544        seq_printf(seq, ",uid=%u",
2545                from_kuid_munged(&init_user_ns, sbinfo->uid));
2546    if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
2547        seq_printf(seq, ",gid=%u",
2548                from_kgid_munged(&init_user_ns, sbinfo->gid));
2549    shmem_show_mpol(seq, sbinfo->mpol);
2550    return 0;
2551}
2552#endif /* CONFIG_TMPFS */
2553
2554static void shmem_put_super(struct super_block *sb)
2555{
2556    struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2557
2558    percpu_counter_destroy(&sbinfo->used_blocks);
2559    mpol_put(sbinfo->mpol);
2560    kfree(sbinfo);
2561    sb->s_fs_info = NULL;
2562}
2563
2564int shmem_fill_super(struct super_block *sb, void *data, int silent)
2565{
2566    struct inode *inode;
2567    struct shmem_sb_info *sbinfo;
2568    int err = -ENOMEM;
2569
2570    /* Round up to L1_CACHE_BYTES to resist false sharing */
2571    sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
2572                L1_CACHE_BYTES), GFP_KERNEL);
2573    if (!sbinfo)
2574        return -ENOMEM;
2575
2576    sbinfo->mode = S_IRWXUGO | S_ISVTX;
2577    sbinfo->uid = current_fsuid();
2578    sbinfo->gid = current_fsgid();
2579    sb->s_fs_info = sbinfo;
2580
2581#ifdef CONFIG_TMPFS
2582    /*
2583     * Per default we only allow half of the physical ram per
2584     * tmpfs instance, limiting inodes to one per page of lowmem;
2585     * but the internal instance is left unlimited.
2586     */
2587    if (!(sb->s_flags & MS_NOUSER)) {
2588        sbinfo->max_blocks = shmem_default_max_blocks();
2589        sbinfo->max_inodes = shmem_default_max_inodes();
2590        if (shmem_parse_options(data, sbinfo, false)) {
2591            err = -EINVAL;
2592            goto failed;
2593        }
2594    }
2595    sb->s_export_op = &shmem_export_ops;
2596    sb->s_flags |= MS_NOSEC;
2597#else
2598    sb->s_flags |= MS_NOUSER;
2599#endif
2600
2601    spin_lock_init(&sbinfo->stat_lock);
2602    if (percpu_counter_init(&sbinfo->used_blocks, 0))
2603        goto failed;
2604    sbinfo->free_inodes = sbinfo->max_inodes;
2605
2606    sb->s_maxbytes = MAX_LFS_FILESIZE;
2607    sb->s_blocksize = PAGE_CACHE_SIZE;
2608    sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
2609    sb->s_magic = TMPFS_MAGIC;
2610    sb->s_op = &shmem_ops;
2611    sb->s_time_gran = 1;
2612#ifdef CONFIG_TMPFS_XATTR
2613    sb->s_xattr = shmem_xattr_handlers;
2614#endif
2615#ifdef CONFIG_TMPFS_POSIX_ACL
2616    sb->s_flags |= MS_POSIXACL;
2617#endif
2618
2619    inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
2620    if (!inode)
2621        goto failed;
2622    inode->i_uid = sbinfo->uid;
2623    inode->i_gid = sbinfo->gid;
2624    sb->s_root = d_make_root(inode);
2625    if (!sb->s_root)
2626        goto failed;
2627    return 0;
2628
2629failed:
2630    shmem_put_super(sb);
2631    return err;
2632}
2633
2634static struct kmem_cache *shmem_inode_cachep;
2635
2636static struct inode *shmem_alloc_inode(struct super_block *sb)
2637{
2638    struct shmem_inode_info *info;
2639    info = kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
2640    if (!info)
2641        return NULL;
2642    return &info->vfs_inode;
2643}
2644
2645static void shmem_destroy_callback(struct rcu_head *head)
2646{
2647    struct inode *inode = container_of(head, struct inode, i_rcu);
2648    kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2649}
2650
2651static void shmem_destroy_inode(struct inode *inode)
2652{
2653    if (S_ISREG(inode->i_mode))
2654        mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2655    call_rcu(&inode->i_rcu, shmem_destroy_callback);
2656}
2657
2658static void shmem_init_inode(void *foo)
2659{
2660    struct shmem_inode_info *info = foo;
2661    inode_init_once(&info->vfs_inode);
2662}
2663
2664static int shmem_init_inodecache(void)
2665{
2666    shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
2667                sizeof(struct shmem_inode_info),
2668                0, SLAB_PANIC, shmem_init_inode);
2669    return 0;
2670}
2671
2672static void shmem_destroy_inodecache(void)
2673{
2674    kmem_cache_destroy(shmem_inode_cachep);
2675}
2676
2677static const struct address_space_operations shmem_aops = {
2678    .writepage = shmem_writepage,
2679    .set_page_dirty = __set_page_dirty_no_writeback,
2680#ifdef CONFIG_TMPFS
2681    .write_begin = shmem_write_begin,
2682    .write_end = shmem_write_end,
2683#endif
2684    .migratepage = migrate_page,
2685    .error_remove_page = generic_error_remove_page,
2686};
2687
2688static const struct file_operations shmem_file_operations = {
2689    .mmap = shmem_mmap,
2690#ifdef CONFIG_TMPFS
2691    .llseek = shmem_file_llseek,
2692    .read = do_sync_read,
2693    .write = do_sync_write,
2694    .aio_read = shmem_file_aio_read,
2695    .aio_write = generic_file_aio_write,
2696    .fsync = noop_fsync,
2697    .splice_read = shmem_file_splice_read,
2698    .splice_write = generic_file_splice_write,
2699    .fallocate = shmem_fallocate,
2700#endif
2701};
2702
2703static const struct inode_operations shmem_inode_operations = {
2704    .setattr = shmem_setattr,
2705#ifdef CONFIG_TMPFS_XATTR
2706    .setxattr = shmem_setxattr,
2707    .getxattr = shmem_getxattr,
2708    .listxattr = shmem_listxattr,
2709    .removexattr = shmem_removexattr,
2710#endif
2711};
2712
2713static const struct inode_operations shmem_dir_inode_operations = {
2714#ifdef CONFIG_TMPFS
2715    .create = shmem_create,
2716    .lookup = simple_lookup,
2717    .link = shmem_link,
2718    .unlink = shmem_unlink,
2719    .symlink = shmem_symlink,
2720    .mkdir = shmem_mkdir,
2721    .rmdir = shmem_rmdir,
2722    .mknod = shmem_mknod,
2723    .rename = shmem_rename,
2724#endif
2725#ifdef CONFIG_TMPFS_XATTR
2726    .setxattr = shmem_setxattr,
2727    .getxattr = shmem_getxattr,
2728    .listxattr = shmem_listxattr,
2729    .removexattr = shmem_removexattr,
2730#endif
2731#ifdef CONFIG_TMPFS_POSIX_ACL
2732    .setattr = shmem_setattr,
2733#endif
2734};
2735
2736static const struct inode_operations shmem_special_inode_operations = {
2737#ifdef CONFIG_TMPFS_XATTR
2738    .setxattr = shmem_setxattr,
2739    .getxattr = shmem_getxattr,
2740    .listxattr = shmem_listxattr,
2741    .removexattr = shmem_removexattr,
2742#endif
2743#ifdef CONFIG_TMPFS_POSIX_ACL
2744    .setattr = shmem_setattr,
2745#endif
2746};
2747
2748static const struct super_operations shmem_ops = {
2749    .alloc_inode = shmem_alloc_inode,
2750    .destroy_inode = shmem_destroy_inode,
2751#ifdef CONFIG_TMPFS
2752    .statfs = shmem_statfs,
2753    .remount_fs = shmem_remount_fs,
2754    .show_options = shmem_show_options,
2755#endif
2756    .evict_inode = shmem_evict_inode,
2757    .drop_inode = generic_delete_inode,
2758    .put_super = shmem_put_super,
2759};
2760
2761static const struct vm_operations_struct shmem_vm_ops = {
2762    .fault = shmem_fault,
2763#ifdef CONFIG_NUMA
2764    .set_policy = shmem_set_policy,
2765    .get_policy = shmem_get_policy,
2766#endif
2767    .remap_pages = generic_file_remap_pages,
2768};
2769
2770static struct dentry *shmem_mount(struct file_system_type *fs_type,
2771    int flags, const char *dev_name, void *data)
2772{
2773    return mount_nodev(fs_type, flags, data, shmem_fill_super);
2774}
2775
2776static struct file_system_type shmem_fs_type = {
2777    .owner = THIS_MODULE,
2778    .name = "tmpfs",
2779    .mount = shmem_mount,
2780    .kill_sb = kill_litter_super,
2781    .fs_flags = FS_USERNS_MOUNT,
2782};
2783
2784int __init shmem_init(void)
2785{
2786    int error;
2787
2788    error = bdi_init(&shmem_backing_dev_info);
2789    if (error)
2790        goto out4;
2791
2792    error = shmem_init_inodecache();
2793    if (error)
2794        goto out3;
2795
2796    error = register_filesystem(&shmem_fs_type);
2797    if (error) {
2798        printk(KERN_ERR "Could not register tmpfs\n");
2799        goto out2;
2800    }
2801
2802    shm_mnt = vfs_kern_mount(&shmem_fs_type, MS_NOUSER,
2803                 shmem_fs_type.name, NULL);
2804    if (IS_ERR(shm_mnt)) {
2805        error = PTR_ERR(shm_mnt);
2806        printk(KERN_ERR "Could not kern_mount tmpfs\n");
2807        goto out1;
2808    }
2809    return 0;
2810
2811out1:
2812    unregister_filesystem(&shmem_fs_type);
2813out2:
2814    shmem_destroy_inodecache();
2815out3:
2816    bdi_destroy(&shmem_backing_dev_info);
2817out4:
2818    shm_mnt = ERR_PTR(error);
2819    return error;
2820}
2821
2822#else /* !CONFIG_SHMEM */
2823
2824/*
2825 * tiny-shmem: simple shmemfs and tmpfs using ramfs code
2826 *
2827 * This is intended for small system where the benefits of the full
2828 * shmem code (swap-backed and resource-limited) are outweighed by
2829 * their complexity. On systems without swap this code should be
2830 * effectively equivalent, but much lighter weight.
2831 */
2832
2833#include <linux/ramfs.h>
2834
2835static struct file_system_type shmem_fs_type = {
2836    .name = "tmpfs",
2837    .mount = ramfs_mount,
2838    .kill_sb = kill_litter_super,
2839    .fs_flags = FS_USERNS_MOUNT,
2840};
2841
2842int __init shmem_init(void)
2843{
2844    BUG_ON(register_filesystem(&shmem_fs_type) != 0);
2845
2846    shm_mnt = kern_mount(&shmem_fs_type);
2847    BUG_ON(IS_ERR(shm_mnt));
2848
2849    return 0;
2850}
2851
2852int shmem_unuse(swp_entry_t swap, struct page *page)
2853{
2854    return 0;
2855}
2856
2857int shmem_lock(struct file *file, int lock, struct user_struct *user)
2858{
2859    return 0;
2860}
2861
2862void shmem_unlock_mapping(struct address_space *mapping)
2863{
2864}
2865
2866void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
2867{
2868    truncate_inode_pages_range(inode->i_mapping, lstart, lend);
2869}
2870EXPORT_SYMBOL_GPL(shmem_truncate_range);
2871
2872#define shmem_vm_ops generic_file_vm_ops
2873#define shmem_file_operations ramfs_file_operations
2874#define shmem_get_inode(sb, dir, mode, dev, flags) ramfs_get_inode(sb, dir, mode, dev)
2875#define shmem_acct_size(flags, size) 0
2876#define shmem_unacct_size(flags, size) do {} while (0)
2877
2878#endif /* CONFIG_SHMEM */
2879
2880/* common code */
2881
2882static char *shmem_dname(struct dentry *dentry, char *buffer, int buflen)
2883{
2884    return dynamic_dname(dentry, buffer, buflen, "/%s (deleted)",
2885                dentry->d_name.name);
2886}
2887
2888static struct dentry_operations anon_ops = {
2889    .d_dname = shmem_dname
2890};
2891
2892/**
2893 * shmem_file_setup - get an unlinked file living in tmpfs
2894 * @name: name for dentry (to be seen in /proc/<pid>/maps
2895 * @size: size to be set for the file
2896 * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
2897 */
2898struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
2899{
2900    struct file *res;
2901    struct inode *inode;
2902    struct path path;
2903    struct super_block *sb;
2904    struct qstr this;
2905
2906    if (IS_ERR(shm_mnt))
2907        return ERR_CAST(shm_mnt);
2908
2909    if (size < 0 || size > MAX_LFS_FILESIZE)
2910        return ERR_PTR(-EINVAL);
2911
2912    if (shmem_acct_size(flags, size))
2913        return ERR_PTR(-ENOMEM);
2914
2915    res = ERR_PTR(-ENOMEM);
2916    this.name = name;
2917    this.len = strlen(name);
2918    this.hash = 0; /* will go */
2919    sb = shm_mnt->mnt_sb;
2920    path.dentry = d_alloc_pseudo(sb, &this);
2921    if (!path.dentry)
2922        goto put_memory;
2923    d_set_d_op(path.dentry, &anon_ops);
2924    path.mnt = mntget(shm_mnt);
2925
2926    res = ERR_PTR(-ENOSPC);
2927    inode = shmem_get_inode(sb, NULL, S_IFREG | S_IRWXUGO, 0, flags);
2928    if (!inode)
2929        goto put_dentry;
2930
2931    d_instantiate(path.dentry, inode);
2932    inode->i_size = size;
2933    clear_nlink(inode); /* It is unlinked */
2934#ifndef CONFIG_MMU
2935    res = ERR_PTR(ramfs_nommu_expand_for_mapping(inode, size));
2936    if (IS_ERR(res))
2937        goto put_dentry;
2938#endif
2939
2940    res = alloc_file(&path, FMODE_WRITE | FMODE_READ,
2941          &shmem_file_operations);
2942    if (IS_ERR(res))
2943        goto put_dentry;
2944
2945    return res;
2946
2947put_dentry:
2948    path_put(&path);
2949put_memory:
2950    shmem_unacct_size(flags, size);
2951    return res;
2952}
2953EXPORT_SYMBOL_GPL(shmem_file_setup);
2954
2955/**
2956 * shmem_zero_setup - setup a shared anonymous mapping
2957 * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
2958 */
2959int shmem_zero_setup(struct vm_area_struct *vma)
2960{
2961    struct file *file;
2962    loff_t size = vma->vm_end - vma->vm_start;
2963
2964    file = shmem_file_setup("dev/zero", size, vma->vm_flags);
2965    if (IS_ERR(file))
2966        return PTR_ERR(file);
2967
2968    if (vma->vm_file)
2969        fput(vma->vm_file);
2970    vma->vm_file = file;
2971    vma->vm_ops = &shmem_vm_ops;
2972    return 0;
2973}
2974
2975/**
2976 * shmem_read_mapping_page_gfp - read into page cache, using specified page allocation flags.
2977 * @mapping: the page's address_space
2978 * @index: the page index
2979 * @gfp: the page allocator flags to use if allocating
2980 *
2981 * This behaves as a tmpfs "read_cache_page_gfp(mapping, index, gfp)",
2982 * with any new page allocations done using the specified allocation flags.
2983 * But read_cache_page_gfp() uses the ->readpage() method: which does not
2984 * suit tmpfs, since it may have pages in swapcache, and needs to find those
2985 * for itself; although drivers/gpu/drm i915 and ttm rely upon this support.
2986 *
2987 * i915_gem_object_get_pages_gtt() mixes __GFP_NORETRY | __GFP_NOWARN in
2988 * with the mapping_gfp_mask(), to avoid OOMing the machine unnecessarily.
2989 */
2990struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
2991                     pgoff_t index, gfp_t gfp)
2992{
2993#ifdef CONFIG_SHMEM
2994    struct inode *inode = mapping->host;
2995    struct page *page;
2996    int error;
2997
2998    BUG_ON(mapping->a_ops != &shmem_aops);
2999    error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE, gfp, NULL);
3000    if (error)
3001        page = ERR_PTR(error);
3002    else
3003        unlock_page(page);
3004    return page;
3005#else
3006    /*
3007     * The tiny !SHMEM case uses ramfs without swap
3008     */
3009    return read_cache_page_gfp(mapping, index, gfp);
3010#endif
3011}
3012EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);
3013

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