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) 2002-2005 Hugh Dickins.
10 * Copyright (C) 2002-2005 VERITAS Software Corporation.
11 * Copyright (C) 2004 Andi Kleen, SuSE Labs
12 *
13 * Extended attribute support for tmpfs:
14 * Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@lkcl.net>
15 * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
16 *
17 * tiny-shmem:
18 * Copyright (c) 2004, 2008 Matt Mackall <mpm@selenic.com>
19 *
20 * This file is released under the GPL.
21 */
22
23#include <linux/fs.h>
24#include <linux/init.h>
25#include <linux/vfs.h>
26#include <linux/mount.h>
27#include <linux/pagemap.h>
28#include <linux/file.h>
29#include <linux/mm.h>
30#include <linux/module.h>
31#include <linux/percpu_counter.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/security.h>
55#include <linux/swapops.h>
56#include <linux/mempolicy.h>
57#include <linux/namei.h>
58#include <linux/ctype.h>
59#include <linux/migrate.h>
60#include <linux/highmem.h>
61#include <linux/seq_file.h>
62#include <linux/magic.h>
63
64#include <asm/uaccess.h>
65#include <asm/div64.h>
66#include <asm/pgtable.h>
67
68/*
69 * The maximum size of a shmem/tmpfs file is limited by the maximum size of
70 * its triple-indirect swap vector - see illustration at shmem_swp_entry().
71 *
72 * With 4kB page size, maximum file size is just over 2TB on a 32-bit kernel,
73 * but one eighth of that on a 64-bit kernel. With 8kB page size, maximum
74 * file size is just over 4TB on a 64-bit kernel, but 16TB on a 32-bit kernel,
75 * MAX_LFS_FILESIZE being then more restrictive than swap vector layout.
76 *
77 * We use / and * instead of shifts in the definitions below, so that the swap
78 * vector can be tested with small even values (e.g. 20) for ENTRIES_PER_PAGE.
79 */
80#define ENTRIES_PER_PAGE (PAGE_CACHE_SIZE/sizeof(unsigned long))
81#define ENTRIES_PER_PAGEPAGE ((unsigned long long)ENTRIES_PER_PAGE*ENTRIES_PER_PAGE)
82
83#define SHMSWP_MAX_INDEX (SHMEM_NR_DIRECT + (ENTRIES_PER_PAGEPAGE/2) * (ENTRIES_PER_PAGE+1))
84#define SHMSWP_MAX_BYTES (SHMSWP_MAX_INDEX << PAGE_CACHE_SHIFT)
85
86#define SHMEM_MAX_BYTES min_t(unsigned long long, SHMSWP_MAX_BYTES, MAX_LFS_FILESIZE)
87#define SHMEM_MAX_INDEX ((unsigned long)((SHMEM_MAX_BYTES+1) >> PAGE_CACHE_SHIFT))
88
89#define BLOCKS_PER_PAGE (PAGE_CACHE_SIZE/512)
90#define VM_ACCT(size) (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
91
92/* info->flags needs VM_flags to handle pagein/truncate races efficiently */
93#define SHMEM_PAGEIN VM_READ
94#define SHMEM_TRUNCATE VM_WRITE
95
96/* Definition to limit shmem_truncate's steps between cond_rescheds */
97#define LATENCY_LIMIT 64
98
99/* Pretend that each entry is of this size in directory's i_size */
100#define BOGO_DIRENT_SIZE 20
101
102/* Flag allocation requirements to shmem_getpage and shmem_swp_alloc */
103enum sgp_type {
104    SGP_READ, /* don't exceed i_size, don't allocate page */
105    SGP_CACHE, /* don't exceed i_size, may allocate page */
106    SGP_DIRTY, /* like SGP_CACHE, but set new page dirty */
107    SGP_WRITE, /* may exceed i_size, may allocate page */
108};
109
110#ifdef CONFIG_TMPFS
111static unsigned long shmem_default_max_blocks(void)
112{
113    return totalram_pages / 2;
114}
115
116static unsigned long shmem_default_max_inodes(void)
117{
118    return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
119}
120#endif
121
122static int shmem_getpage(struct inode *inode, unsigned long idx,
123             struct page **pagep, enum sgp_type sgp, int *type);
124
125static inline struct page *shmem_dir_alloc(gfp_t gfp_mask)
126{
127    /*
128     * The above definition of ENTRIES_PER_PAGE, and the use of
129     * BLOCKS_PER_PAGE on indirect pages, assume PAGE_CACHE_SIZE:
130     * might be reconsidered if it ever diverges from PAGE_SIZE.
131     *
132     * Mobility flags are masked out as swap vectors cannot move
133     */
134    return alloc_pages((gfp_mask & ~GFP_MOVABLE_MASK) | __GFP_ZERO,
135                PAGE_CACHE_SHIFT-PAGE_SHIFT);
136}
137
138static inline void shmem_dir_free(struct page *page)
139{
140    __free_pages(page, PAGE_CACHE_SHIFT-PAGE_SHIFT);
141}
142
143static struct page **shmem_dir_map(struct page *page)
144{
145    return (struct page **)kmap_atomic(page, KM_USER0);
146}
147
148static inline void shmem_dir_unmap(struct page **dir)
149{
150    kunmap_atomic(dir, KM_USER0);
151}
152
153static swp_entry_t *shmem_swp_map(struct page *page)
154{
155    return (swp_entry_t *)kmap_atomic(page, KM_USER1);
156}
157
158static inline void shmem_swp_balance_unmap(void)
159{
160    /*
161     * When passing a pointer to an i_direct entry, to code which
162     * also handles indirect entries and so will shmem_swp_unmap,
163     * we must arrange for the preempt count to remain in balance.
164     * What kmap_atomic of a lowmem page does depends on config
165     * and architecture, so pretend to kmap_atomic some lowmem page.
166     */
167    (void) kmap_atomic(ZERO_PAGE(0), KM_USER1);
168}
169
170static inline void shmem_swp_unmap(swp_entry_t *entry)
171{
172    kunmap_atomic(entry, KM_USER1);
173}
174
175static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
176{
177    return sb->s_fs_info;
178}
179
180/*
181 * shmem_file_setup pre-accounts the whole fixed size of a VM object,
182 * for shared memory and for shared anonymous (/dev/zero) mappings
183 * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
184 * consistent with the pre-accounting of private mappings ...
185 */
186static inline int shmem_acct_size(unsigned long flags, loff_t size)
187{
188    return (flags & VM_NORESERVE) ?
189        0 : security_vm_enough_memory_kern(VM_ACCT(size));
190}
191
192static inline void shmem_unacct_size(unsigned long flags, loff_t size)
193{
194    if (!(flags & VM_NORESERVE))
195        vm_unacct_memory(VM_ACCT(size));
196}
197
198/*
199 * ... whereas tmpfs objects are accounted incrementally as
200 * pages are allocated, in order to allow huge sparse files.
201 * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
202 * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
203 */
204static inline int shmem_acct_block(unsigned long flags)
205{
206    return (flags & VM_NORESERVE) ?
207        security_vm_enough_memory_kern(VM_ACCT(PAGE_CACHE_SIZE)) : 0;
208}
209
210static inline void shmem_unacct_blocks(unsigned long flags, long pages)
211{
212    if (flags & VM_NORESERVE)
213        vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
214}
215
216static const struct super_operations shmem_ops;
217static const struct address_space_operations shmem_aops;
218static const struct file_operations shmem_file_operations;
219static const struct inode_operations shmem_inode_operations;
220static const struct inode_operations shmem_dir_inode_operations;
221static const struct inode_operations shmem_special_inode_operations;
222static const struct vm_operations_struct shmem_vm_ops;
223
224static struct backing_dev_info shmem_backing_dev_info __read_mostly = {
225    .ra_pages = 0, /* No readahead */
226    .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
227    .unplug_io_fn = default_unplug_io_fn,
228};
229
230static LIST_HEAD(shmem_swaplist);
231static DEFINE_MUTEX(shmem_swaplist_mutex);
232
233static void shmem_free_blocks(struct inode *inode, long pages)
234{
235    struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
236    if (sbinfo->max_blocks) {
237        percpu_counter_add(&sbinfo->used_blocks, -pages);
238        spin_lock(&inode->i_lock);
239        inode->i_blocks -= pages*BLOCKS_PER_PAGE;
240        spin_unlock(&inode->i_lock);
241    }
242}
243
244static int shmem_reserve_inode(struct super_block *sb)
245{
246    struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
247    if (sbinfo->max_inodes) {
248        spin_lock(&sbinfo->stat_lock);
249        if (!sbinfo->free_inodes) {
250            spin_unlock(&sbinfo->stat_lock);
251            return -ENOSPC;
252        }
253        sbinfo->free_inodes--;
254        spin_unlock(&sbinfo->stat_lock);
255    }
256    return 0;
257}
258
259static void shmem_free_inode(struct super_block *sb)
260{
261    struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
262    if (sbinfo->max_inodes) {
263        spin_lock(&sbinfo->stat_lock);
264        sbinfo->free_inodes++;
265        spin_unlock(&sbinfo->stat_lock);
266    }
267}
268
269/**
270 * shmem_recalc_inode - recalculate the size of an inode
271 * @inode: inode to recalc
272 *
273 * We have to calculate the free blocks since the mm can drop
274 * undirtied hole pages behind our back.
275 *
276 * But normally info->alloced == inode->i_mapping->nrpages + info->swapped
277 * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
278 *
279 * It has to be called with the spinlock held.
280 */
281static void shmem_recalc_inode(struct inode *inode)
282{
283    struct shmem_inode_info *info = SHMEM_I(inode);
284    long freed;
285
286    freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
287    if (freed > 0) {
288        info->alloced -= freed;
289        shmem_unacct_blocks(info->flags, freed);
290        shmem_free_blocks(inode, freed);
291    }
292}
293
294/**
295 * shmem_swp_entry - find the swap vector position in the info structure
296 * @info: info structure for the inode
297 * @index: index of the page to find
298 * @page: optional page to add to the structure. Has to be preset to
299 * all zeros
300 *
301 * If there is no space allocated yet it will return NULL when
302 * page is NULL, else it will use the page for the needed block,
303 * setting it to NULL on return to indicate that it has been used.
304 *
305 * The swap vector is organized the following way:
306 *
307 * There are SHMEM_NR_DIRECT entries directly stored in the
308 * shmem_inode_info structure. So small files do not need an addional
309 * allocation.
310 *
311 * For pages with index > SHMEM_NR_DIRECT there is the pointer
312 * i_indirect which points to a page which holds in the first half
313 * doubly indirect blocks, in the second half triple indirect blocks:
314 *
315 * For an artificial ENTRIES_PER_PAGE = 4 this would lead to the
316 * following layout (for SHMEM_NR_DIRECT == 16):
317 *
318 * i_indirect -> dir --> 16-19
319 * | +-> 20-23
320 * |
321 * +-->dir2 --> 24-27
322 * | +-> 28-31
323 * | +-> 32-35
324 * | +-> 36-39
325 * |
326 * +-->dir3 --> 40-43
327 * +-> 44-47
328 * +-> 48-51
329 * +-> 52-55
330 */
331static swp_entry_t *shmem_swp_entry(struct shmem_inode_info *info, unsigned long index, struct page **page)
332{
333    unsigned long offset;
334    struct page **dir;
335    struct page *subdir;
336
337    if (index < SHMEM_NR_DIRECT) {
338        shmem_swp_balance_unmap();
339        return info->i_direct+index;
340    }
341    if (!info->i_indirect) {
342        if (page) {
343            info->i_indirect = *page;
344            *page = NULL;
345        }
346        return NULL; /* need another page */
347    }
348
349    index -= SHMEM_NR_DIRECT;
350    offset = index % ENTRIES_PER_PAGE;
351    index /= ENTRIES_PER_PAGE;
352    dir = shmem_dir_map(info->i_indirect);
353
354    if (index >= ENTRIES_PER_PAGE/2) {
355        index -= ENTRIES_PER_PAGE/2;
356        dir += ENTRIES_PER_PAGE/2 + index/ENTRIES_PER_PAGE;
357        index %= ENTRIES_PER_PAGE;
358        subdir = *dir;
359        if (!subdir) {
360            if (page) {
361                *dir = *page;
362                *page = NULL;
363            }
364            shmem_dir_unmap(dir);
365            return NULL; /* need another page */
366        }
367        shmem_dir_unmap(dir);
368        dir = shmem_dir_map(subdir);
369    }
370
371    dir += index;
372    subdir = *dir;
373    if (!subdir) {
374        if (!page || !(subdir = *page)) {
375            shmem_dir_unmap(dir);
376            return NULL; /* need a page */
377        }
378        *dir = subdir;
379        *page = NULL;
380    }
381    shmem_dir_unmap(dir);
382    return shmem_swp_map(subdir) + offset;
383}
384
385static void shmem_swp_set(struct shmem_inode_info *info, swp_entry_t *entry, unsigned long value)
386{
387    long incdec = value? 1: -1;
388
389    entry->val = value;
390    info->swapped += incdec;
391    if ((unsigned long)(entry - info->i_direct) >= SHMEM_NR_DIRECT) {
392        struct page *page = kmap_atomic_to_page(entry);
393        set_page_private(page, page_private(page) + incdec);
394    }
395}
396
397/**
398 * shmem_swp_alloc - get the position of the swap entry for the page.
399 * @info: info structure for the inode
400 * @index: index of the page to find
401 * @sgp: check and recheck i_size? skip allocation?
402 *
403 * If the entry does not exist, allocate it.
404 */
405static swp_entry_t *shmem_swp_alloc(struct shmem_inode_info *info, unsigned long index, enum sgp_type sgp)
406{
407    struct inode *inode = &info->vfs_inode;
408    struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
409    struct page *page = NULL;
410    swp_entry_t *entry;
411
412    if (sgp != SGP_WRITE &&
413        ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode))
414        return ERR_PTR(-EINVAL);
415
416    while (!(entry = shmem_swp_entry(info, index, &page))) {
417        if (sgp == SGP_READ)
418            return shmem_swp_map(ZERO_PAGE(0));
419        /*
420         * Test used_blocks against 1 less max_blocks, since we have 1 data
421         * page (and perhaps indirect index pages) yet to allocate:
422         * a waste to allocate index if we cannot allocate data.
423         */
424        if (sbinfo->max_blocks) {
425            if (percpu_counter_compare(&sbinfo->used_blocks, (sbinfo->max_blocks - 1)) > 0)
426                return ERR_PTR(-ENOSPC);
427            percpu_counter_inc(&sbinfo->used_blocks);
428            spin_lock(&inode->i_lock);
429            inode->i_blocks += BLOCKS_PER_PAGE;
430            spin_unlock(&inode->i_lock);
431        }
432
433        spin_unlock(&info->lock);
434        page = shmem_dir_alloc(mapping_gfp_mask(inode->i_mapping));
435        spin_lock(&info->lock);
436
437        if (!page) {
438            shmem_free_blocks(inode, 1);
439            return ERR_PTR(-ENOMEM);
440        }
441        if (sgp != SGP_WRITE &&
442            ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
443            entry = ERR_PTR(-EINVAL);
444            break;
445        }
446        if (info->next_index <= index)
447            info->next_index = index + 1;
448    }
449    if (page) {
450        /* another task gave its page, or truncated the file */
451        shmem_free_blocks(inode, 1);
452        shmem_dir_free(page);
453    }
454    if (info->next_index <= index && !IS_ERR(entry))
455        info->next_index = index + 1;
456    return entry;
457}
458
459/**
460 * shmem_free_swp - free some swap entries in a directory
461 * @dir: pointer to the directory
462 * @edir: pointer after last entry of the directory
463 * @punch_lock: pointer to spinlock when needed for the holepunch case
464 */
465static int shmem_free_swp(swp_entry_t *dir, swp_entry_t *edir,
466                        spinlock_t *punch_lock)
467{
468    spinlock_t *punch_unlock = NULL;
469    swp_entry_t *ptr;
470    int freed = 0;
471
472    for (ptr = dir; ptr < edir; ptr++) {
473        if (ptr->val) {
474            if (unlikely(punch_lock)) {
475                punch_unlock = punch_lock;
476                punch_lock = NULL;
477                spin_lock(punch_unlock);
478                if (!ptr->val)
479                    continue;
480            }
481            free_swap_and_cache(*ptr);
482            *ptr = (swp_entry_t){0};
483            freed++;
484        }
485    }
486    if (punch_unlock)
487        spin_unlock(punch_unlock);
488    return freed;
489}
490
491static int shmem_map_and_free_swp(struct page *subdir, int offset,
492        int limit, struct page ***dir, spinlock_t *punch_lock)
493{
494    swp_entry_t *ptr;
495    int freed = 0;
496
497    ptr = shmem_swp_map(subdir);
498    for (; offset < limit; offset += LATENCY_LIMIT) {
499        int size = limit - offset;
500        if (size > LATENCY_LIMIT)
501            size = LATENCY_LIMIT;
502        freed += shmem_free_swp(ptr+offset, ptr+offset+size,
503                            punch_lock);
504        if (need_resched()) {
505            shmem_swp_unmap(ptr);
506            if (*dir) {
507                shmem_dir_unmap(*dir);
508                *dir = NULL;
509            }
510            cond_resched();
511            ptr = shmem_swp_map(subdir);
512        }
513    }
514    shmem_swp_unmap(ptr);
515    return freed;
516}
517
518static void shmem_free_pages(struct list_head *next)
519{
520    struct page *page;
521    int freed = 0;
522
523    do {
524        page = container_of(next, struct page, lru);
525        next = next->next;
526        shmem_dir_free(page);
527        freed++;
528        if (freed >= LATENCY_LIMIT) {
529            cond_resched();
530            freed = 0;
531        }
532    } while (next);
533}
534
535static void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end)
536{
537    struct shmem_inode_info *info = SHMEM_I(inode);
538    unsigned long idx;
539    unsigned long size;
540    unsigned long limit;
541    unsigned long stage;
542    unsigned long diroff;
543    struct page **dir;
544    struct page *topdir;
545    struct page *middir;
546    struct page *subdir;
547    swp_entry_t *ptr;
548    LIST_HEAD(pages_to_free);
549    long nr_pages_to_free = 0;
550    long nr_swaps_freed = 0;
551    int offset;
552    int freed;
553    int punch_hole;
554    spinlock_t *needs_lock;
555    spinlock_t *punch_lock;
556    unsigned long upper_limit;
557
558    inode->i_ctime = inode->i_mtime = CURRENT_TIME;
559    idx = (start + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
560    if (idx >= info->next_index)
561        return;
562
563    spin_lock(&info->lock);
564    info->flags |= SHMEM_TRUNCATE;
565    if (likely(end == (loff_t) -1)) {
566        limit = info->next_index;
567        upper_limit = SHMEM_MAX_INDEX;
568        info->next_index = idx;
569        needs_lock = NULL;
570        punch_hole = 0;
571    } else {
572        if (end + 1 >= inode->i_size) { /* we may free a little more */
573            limit = (inode->i_size + PAGE_CACHE_SIZE - 1) >>
574                            PAGE_CACHE_SHIFT;
575            upper_limit = SHMEM_MAX_INDEX;
576        } else {
577            limit = (end + 1) >> PAGE_CACHE_SHIFT;
578            upper_limit = limit;
579        }
580        needs_lock = &info->lock;
581        punch_hole = 1;
582    }
583
584    topdir = info->i_indirect;
585    if (topdir && idx <= SHMEM_NR_DIRECT && !punch_hole) {
586        info->i_indirect = NULL;
587        nr_pages_to_free++;
588        list_add(&topdir->lru, &pages_to_free);
589    }
590    spin_unlock(&info->lock);
591
592    if (info->swapped && idx < SHMEM_NR_DIRECT) {
593        ptr = info->i_direct;
594        size = limit;
595        if (size > SHMEM_NR_DIRECT)
596            size = SHMEM_NR_DIRECT;
597        nr_swaps_freed = shmem_free_swp(ptr+idx, ptr+size, needs_lock);
598    }
599
600    /*
601     * If there are no indirect blocks or we are punching a hole
602     * below indirect blocks, nothing to be done.
603     */
604    if (!topdir || limit <= SHMEM_NR_DIRECT)
605        goto done2;
606
607    /*
608     * The truncation case has already dropped info->lock, and we're safe
609     * because i_size and next_index have already been lowered, preventing
610     * access beyond. But in the punch_hole case, we still need to take
611     * the lock when updating the swap directory, because there might be
612     * racing accesses by shmem_getpage(SGP_CACHE), shmem_unuse_inode or
613     * shmem_writepage. However, whenever we find we can remove a whole
614     * directory page (not at the misaligned start or end of the range),
615     * we first NULLify its pointer in the level above, and then have no
616     * need to take the lock when updating its contents: needs_lock and
617     * punch_lock (either pointing to info->lock or NULL) manage this.
618     */
619
620    upper_limit -= SHMEM_NR_DIRECT;
621    limit -= SHMEM_NR_DIRECT;
622    idx = (idx > SHMEM_NR_DIRECT)? (idx - SHMEM_NR_DIRECT): 0;
623    offset = idx % ENTRIES_PER_PAGE;
624    idx -= offset;
625
626    dir = shmem_dir_map(topdir);
627    stage = ENTRIES_PER_PAGEPAGE/2;
628    if (idx < ENTRIES_PER_PAGEPAGE/2) {
629        middir = topdir;
630        diroff = idx/ENTRIES_PER_PAGE;
631    } else {
632        dir += ENTRIES_PER_PAGE/2;
633        dir += (idx - ENTRIES_PER_PAGEPAGE/2)/ENTRIES_PER_PAGEPAGE;
634        while (stage <= idx)
635            stage += ENTRIES_PER_PAGEPAGE;
636        middir = *dir;
637        if (*dir) {
638            diroff = ((idx - ENTRIES_PER_PAGEPAGE/2) %
639                ENTRIES_PER_PAGEPAGE) / ENTRIES_PER_PAGE;
640            if (!diroff && !offset && upper_limit >= stage) {
641                if (needs_lock) {
642                    spin_lock(needs_lock);
643                    *dir = NULL;
644                    spin_unlock(needs_lock);
645                    needs_lock = NULL;
646                } else
647                    *dir = NULL;
648                nr_pages_to_free++;
649                list_add(&middir->lru, &pages_to_free);
650            }
651            shmem_dir_unmap(dir);
652            dir = shmem_dir_map(middir);
653        } else {
654            diroff = 0;
655            offset = 0;
656            idx = stage;
657        }
658    }
659
660    for (; idx < limit; idx += ENTRIES_PER_PAGE, diroff++) {
661        if (unlikely(idx == stage)) {
662            shmem_dir_unmap(dir);
663            dir = shmem_dir_map(topdir) +
664                ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
665            while (!*dir) {
666                dir++;
667                idx += ENTRIES_PER_PAGEPAGE;
668                if (idx >= limit)
669                    goto done1;
670            }
671            stage = idx + ENTRIES_PER_PAGEPAGE;
672            middir = *dir;
673            if (punch_hole)
674                needs_lock = &info->lock;
675            if (upper_limit >= stage) {
676                if (needs_lock) {
677                    spin_lock(needs_lock);
678                    *dir = NULL;
679                    spin_unlock(needs_lock);
680                    needs_lock = NULL;
681                } else
682                    *dir = NULL;
683                nr_pages_to_free++;
684                list_add(&middir->lru, &pages_to_free);
685            }
686            shmem_dir_unmap(dir);
687            cond_resched();
688            dir = shmem_dir_map(middir);
689            diroff = 0;
690        }
691        punch_lock = needs_lock;
692        subdir = dir[diroff];
693        if (subdir && !offset && upper_limit-idx >= ENTRIES_PER_PAGE) {
694            if (needs_lock) {
695                spin_lock(needs_lock);
696                dir[diroff] = NULL;
697                spin_unlock(needs_lock);
698                punch_lock = NULL;
699            } else
700                dir[diroff] = NULL;
701            nr_pages_to_free++;
702            list_add(&subdir->lru, &pages_to_free);
703        }
704        if (subdir && page_private(subdir) /* has swap entries */) {
705            size = limit - idx;
706            if (size > ENTRIES_PER_PAGE)
707                size = ENTRIES_PER_PAGE;
708            freed = shmem_map_and_free_swp(subdir,
709                    offset, size, &dir, punch_lock);
710            if (!dir)
711                dir = shmem_dir_map(middir);
712            nr_swaps_freed += freed;
713            if (offset || punch_lock) {
714                spin_lock(&info->lock);
715                set_page_private(subdir,
716                    page_private(subdir) - freed);
717                spin_unlock(&info->lock);
718            } else
719                BUG_ON(page_private(subdir) != freed);
720        }
721        offset = 0;
722    }
723done1:
724    shmem_dir_unmap(dir);
725done2:
726    if (inode->i_mapping->nrpages && (info->flags & SHMEM_PAGEIN)) {
727        /*
728         * Call truncate_inode_pages again: racing shmem_unuse_inode
729         * may have swizzled a page in from swap since
730         * truncate_pagecache or generic_delete_inode did it, before we
731         * lowered next_index. Also, though shmem_getpage checks
732         * i_size before adding to cache, no recheck after: so fix the
733         * narrow window there too.
734         *
735         * Recalling truncate_inode_pages_range and unmap_mapping_range
736         * every time for punch_hole (which never got a chance to clear
737         * SHMEM_PAGEIN at the start of vmtruncate_range) is expensive,
738         * yet hardly ever necessary: try to optimize them out later.
739         */
740        truncate_inode_pages_range(inode->i_mapping, start, end);
741        if (punch_hole)
742            unmap_mapping_range(inode->i_mapping, start,
743                            end - start, 1);
744    }
745
746    spin_lock(&info->lock);
747    info->flags &= ~SHMEM_TRUNCATE;
748    info->swapped -= nr_swaps_freed;
749    if (nr_pages_to_free)
750        shmem_free_blocks(inode, nr_pages_to_free);
751    shmem_recalc_inode(inode);
752    spin_unlock(&info->lock);
753
754    /*
755     * Empty swap vector directory pages to be freed?
756     */
757    if (!list_empty(&pages_to_free)) {
758        pages_to_free.prev->next = NULL;
759        shmem_free_pages(pages_to_free.next);
760    }
761}
762
763static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
764{
765    struct inode *inode = dentry->d_inode;
766    loff_t newsize = attr->ia_size;
767    int error;
768
769    error = inode_change_ok(inode, attr);
770    if (error)
771        return error;
772
773    if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)
774                    && newsize != inode->i_size) {
775        struct page *page = NULL;
776
777        if (newsize < inode->i_size) {
778            /*
779             * If truncating down to a partial page, then
780             * if that page is already allocated, hold it
781             * in memory until the truncation is over, so
782             * truncate_partial_page cannnot miss it were
783             * it assigned to swap.
784             */
785            if (newsize & (PAGE_CACHE_SIZE-1)) {
786                (void) shmem_getpage(inode,
787                    newsize >> PAGE_CACHE_SHIFT,
788                        &page, SGP_READ, NULL);
789                if (page)
790                    unlock_page(page);
791            }
792            /*
793             * Reset SHMEM_PAGEIN flag so that shmem_truncate can
794             * detect if any pages might have been added to cache
795             * after truncate_inode_pages. But we needn't bother
796             * if it's being fully truncated to zero-length: the
797             * nrpages check is efficient enough in that case.
798             */
799            if (newsize) {
800                struct shmem_inode_info *info = SHMEM_I(inode);
801                spin_lock(&info->lock);
802                info->flags &= ~SHMEM_PAGEIN;
803                spin_unlock(&info->lock);
804            }
805        }
806
807        /* XXX(truncate): truncate_setsize should be called last */
808        truncate_setsize(inode, newsize);
809        if (page)
810            page_cache_release(page);
811        shmem_truncate_range(inode, newsize, (loff_t)-1);
812    }
813
814    setattr_copy(inode, attr);
815#ifdef CONFIG_TMPFS_POSIX_ACL
816    if (attr->ia_valid & ATTR_MODE)
817        error = generic_acl_chmod(inode);
818#endif
819    return error;
820}
821
822static void shmem_evict_inode(struct inode *inode)
823{
824    struct shmem_inode_info *info = SHMEM_I(inode);
825
826    if (inode->i_mapping->a_ops == &shmem_aops) {
827        truncate_inode_pages(inode->i_mapping, 0);
828        shmem_unacct_size(info->flags, inode->i_size);
829        inode->i_size = 0;
830        shmem_truncate_range(inode, 0, (loff_t)-1);
831        if (!list_empty(&info->swaplist)) {
832            mutex_lock(&shmem_swaplist_mutex);
833            list_del_init(&info->swaplist);
834            mutex_unlock(&shmem_swaplist_mutex);
835        }
836    }
837    BUG_ON(inode->i_blocks);
838    shmem_free_inode(inode->i_sb);
839    end_writeback(inode);
840}
841
842static inline int shmem_find_swp(swp_entry_t entry, swp_entry_t *dir, swp_entry_t *edir)
843{
844    swp_entry_t *ptr;
845
846    for (ptr = dir; ptr < edir; ptr++) {
847        if (ptr->val == entry.val)
848            return ptr - dir;
849    }
850    return -1;
851}
852
853static int shmem_unuse_inode(struct shmem_inode_info *info, swp_entry_t entry, struct page *page)
854{
855    struct inode *inode;
856    unsigned long idx;
857    unsigned long size;
858    unsigned long limit;
859    unsigned long stage;
860    struct page **dir;
861    struct page *subdir;
862    swp_entry_t *ptr;
863    int offset;
864    int error;
865
866    idx = 0;
867    ptr = info->i_direct;
868    spin_lock(&info->lock);
869    if (!info->swapped) {
870        list_del_init(&info->swaplist);
871        goto lost2;
872    }
873    limit = info->next_index;
874    size = limit;
875    if (size > SHMEM_NR_DIRECT)
876        size = SHMEM_NR_DIRECT;
877    offset = shmem_find_swp(entry, ptr, ptr+size);
878    if (offset >= 0)
879        goto found;
880    if (!info->i_indirect)
881        goto lost2;
882
883    dir = shmem_dir_map(info->i_indirect);
884    stage = SHMEM_NR_DIRECT + ENTRIES_PER_PAGEPAGE/2;
885
886    for (idx = SHMEM_NR_DIRECT; idx < limit; idx += ENTRIES_PER_PAGE, dir++) {
887        if (unlikely(idx == stage)) {
888            shmem_dir_unmap(dir-1);
889            if (cond_resched_lock(&info->lock)) {
890                /* check it has not been truncated */
891                if (limit > info->next_index) {
892                    limit = info->next_index;
893                    if (idx >= limit)
894                        goto lost2;
895                }
896            }
897            dir = shmem_dir_map(info->i_indirect) +
898                ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
899            while (!*dir) {
900                dir++;
901                idx += ENTRIES_PER_PAGEPAGE;
902                if (idx >= limit)
903                    goto lost1;
904            }
905            stage = idx + ENTRIES_PER_PAGEPAGE;
906            subdir = *dir;
907            shmem_dir_unmap(dir);
908            dir = shmem_dir_map(subdir);
909        }
910        subdir = *dir;
911        if (subdir && page_private(subdir)) {
912            ptr = shmem_swp_map(subdir);
913            size = limit - idx;
914            if (size > ENTRIES_PER_PAGE)
915                size = ENTRIES_PER_PAGE;
916            offset = shmem_find_swp(entry, ptr, ptr+size);
917            shmem_swp_unmap(ptr);
918            if (offset >= 0) {
919                shmem_dir_unmap(dir);
920                goto found;
921            }
922        }
923    }
924lost1:
925    shmem_dir_unmap(dir-1);
926lost2:
927    spin_unlock(&info->lock);
928    return 0;
929found:
930    idx += offset;
931    inode = igrab(&info->vfs_inode);
932    spin_unlock(&info->lock);
933
934    /*
935     * Move _head_ to start search for next from here.
936     * But be careful: shmem_evict_inode checks list_empty without taking
937     * mutex, and there's an instant in list_move_tail when info->swaplist
938     * would appear empty, if it were the only one on shmem_swaplist. We
939     * could avoid doing it if inode NULL; or use this minor optimization.
940     */
941    if (shmem_swaplist.next != &info->swaplist)
942        list_move_tail(&shmem_swaplist, &info->swaplist);
943    mutex_unlock(&shmem_swaplist_mutex);
944
945    error = 1;
946    if (!inode)
947        goto out;
948    /*
949     * Charge page using GFP_KERNEL while we can wait.
950     * Charged back to the user(not to caller) when swap account is used.
951     * add_to_page_cache() will be called with GFP_NOWAIT.
952     */
953    error = mem_cgroup_cache_charge(page, current->mm, GFP_KERNEL);
954    if (error)
955        goto out;
956    error = radix_tree_preload(GFP_KERNEL);
957    if (error) {
958        mem_cgroup_uncharge_cache_page(page);
959        goto out;
960    }
961    error = 1;
962
963    spin_lock(&info->lock);
964    ptr = shmem_swp_entry(info, idx, NULL);
965    if (ptr && ptr->val == entry.val) {
966        error = add_to_page_cache_locked(page, inode->i_mapping,
967                        idx, GFP_NOWAIT);
968        /* does mem_cgroup_uncharge_cache_page on error */
969    } else /* we must compensate for our precharge above */
970        mem_cgroup_uncharge_cache_page(page);
971
972    if (error == -EEXIST) {
973        struct page *filepage = find_get_page(inode->i_mapping, idx);
974        error = 1;
975        if (filepage) {
976            /*
977             * There might be a more uptodate page coming down
978             * from a stacked writepage: forget our swappage if so.
979             */
980            if (PageUptodate(filepage))
981                error = 0;
982            page_cache_release(filepage);
983        }
984    }
985    if (!error) {
986        delete_from_swap_cache(page);
987        set_page_dirty(page);
988        info->flags |= SHMEM_PAGEIN;
989        shmem_swp_set(info, ptr, 0);
990        swap_free(entry);
991        error = 1; /* not an error, but entry was found */
992    }
993    if (ptr)
994        shmem_swp_unmap(ptr);
995    spin_unlock(&info->lock);
996    radix_tree_preload_end();
997out:
998    unlock_page(page);
999    page_cache_release(page);
1000    iput(inode); /* allows for NULL */
1001    return error;
1002}
1003
1004/*
1005 * shmem_unuse() search for an eventually swapped out shmem page.
1006 */
1007int shmem_unuse(swp_entry_t entry, struct page *page)
1008{
1009    struct list_head *p, *next;
1010    struct shmem_inode_info *info;
1011    int found = 0;
1012
1013    mutex_lock(&shmem_swaplist_mutex);
1014    list_for_each_safe(p, next, &shmem_swaplist) {
1015        info = list_entry(p, struct shmem_inode_info, swaplist);
1016        found = shmem_unuse_inode(info, entry, page);
1017        cond_resched();
1018        if (found)
1019            goto out;
1020    }
1021    mutex_unlock(&shmem_swaplist_mutex);
1022    /*
1023     * Can some race bring us here? We've been holding page lock,
1024     * so I think not; but would rather try again later than BUG()
1025     */
1026    unlock_page(page);
1027    page_cache_release(page);
1028out:
1029    return (found < 0) ? found : 0;
1030}
1031
1032/*
1033 * Move the page from the page cache to the swap cache.
1034 */
1035static int shmem_writepage(struct page *page, struct writeback_control *wbc)
1036{
1037    struct shmem_inode_info *info;
1038    swp_entry_t *entry, swap;
1039    struct address_space *mapping;
1040    unsigned long index;
1041    struct inode *inode;
1042
1043    BUG_ON(!PageLocked(page));
1044    mapping = page->mapping;
1045    index = page->index;
1046    inode = mapping->host;
1047    info = SHMEM_I(inode);
1048    if (info->flags & VM_LOCKED)
1049        goto redirty;
1050    if (!total_swap_pages)
1051        goto redirty;
1052
1053    /*
1054     * shmem_backing_dev_info's capabilities prevent regular writeback or
1055     * sync from ever calling shmem_writepage; but a stacking filesystem
1056     * may use the ->writepage of its underlying filesystem, in which case
1057     * tmpfs should write out to swap only in response to memory pressure,
1058     * and not for the writeback threads or sync. However, in those cases,
1059     * we do still want to check if there's a redundant swappage to be
1060     * discarded.
1061     */
1062    if (wbc->for_reclaim)
1063        swap = get_swap_page();
1064    else
1065        swap.val = 0;
1066
1067    spin_lock(&info->lock);
1068    if (index >= info->next_index) {
1069        BUG_ON(!(info->flags & SHMEM_TRUNCATE));
1070        goto unlock;
1071    }
1072    entry = shmem_swp_entry(info, index, NULL);
1073    if (entry->val) {
1074        /*
1075         * The more uptodate page coming down from a stacked
1076         * writepage should replace our old swappage.
1077         */
1078        free_swap_and_cache(*entry);
1079        shmem_swp_set(info, entry, 0);
1080    }
1081    shmem_recalc_inode(inode);
1082
1083    if (swap.val && add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
1084        remove_from_page_cache(page);
1085        shmem_swp_set(info, entry, swap.val);
1086        shmem_swp_unmap(entry);
1087        if (list_empty(&info->swaplist))
1088            inode = igrab(inode);
1089        else
1090            inode = NULL;
1091        spin_unlock(&info->lock);
1092        swap_shmem_alloc(swap);
1093        BUG_ON(page_mapped(page));
1094        page_cache_release(page); /* pagecache ref */
1095        swap_writepage(page, wbc);
1096        if (inode) {
1097            mutex_lock(&shmem_swaplist_mutex);
1098            /* move instead of add in case we're racing */
1099            list_move_tail(&info->swaplist, &shmem_swaplist);
1100            mutex_unlock(&shmem_swaplist_mutex);
1101            iput(inode);
1102        }
1103        return 0;
1104    }
1105
1106    shmem_swp_unmap(entry);
1107unlock:
1108    spin_unlock(&info->lock);
1109    /*
1110     * add_to_swap_cache() doesn't return -EEXIST, so we can safely
1111     * clear SWAP_HAS_CACHE flag.
1112     */
1113    swapcache_free(swap, NULL);
1114redirty:
1115    set_page_dirty(page);
1116    if (wbc->for_reclaim)
1117        return AOP_WRITEPAGE_ACTIVATE; /* Return with page locked */
1118    unlock_page(page);
1119    return 0;
1120}
1121
1122#ifdef CONFIG_NUMA
1123#ifdef CONFIG_TMPFS
1124static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
1125{
1126    char buffer[64];
1127
1128    if (!mpol || mpol->mode == MPOL_DEFAULT)
1129        return; /* show nothing */
1130
1131    mpol_to_str(buffer, sizeof(buffer), mpol, 1);
1132
1133    seq_printf(seq, ",mpol=%s", buffer);
1134}
1135
1136static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1137{
1138    struct mempolicy *mpol = NULL;
1139    if (sbinfo->mpol) {
1140        spin_lock(&sbinfo->stat_lock); /* prevent replace/use races */
1141        mpol = sbinfo->mpol;
1142        mpol_get(mpol);
1143        spin_unlock(&sbinfo->stat_lock);
1144    }
1145    return mpol;
1146}
1147#endif /* CONFIG_TMPFS */
1148
1149static struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
1150            struct shmem_inode_info *info, unsigned long idx)
1151{
1152    struct mempolicy mpol, *spol;
1153    struct vm_area_struct pvma;
1154    struct page *page;
1155
1156    spol = mpol_cond_copy(&mpol,
1157                mpol_shared_policy_lookup(&info->policy, idx));
1158
1159    /* Create a pseudo vma that just contains the policy */
1160    pvma.vm_start = 0;
1161    pvma.vm_pgoff = idx;
1162    pvma.vm_ops = NULL;
1163    pvma.vm_policy = spol;
1164    page = swapin_readahead(entry, gfp, &pvma, 0);
1165    return page;
1166}
1167
1168static struct page *shmem_alloc_page(gfp_t gfp,
1169            struct shmem_inode_info *info, unsigned long idx)
1170{
1171    struct vm_area_struct pvma;
1172
1173    /* Create a pseudo vma that just contains the policy */
1174    pvma.vm_start = 0;
1175    pvma.vm_pgoff = idx;
1176    pvma.vm_ops = NULL;
1177    pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx);
1178
1179    /*
1180     * alloc_page_vma() will drop the shared policy reference
1181     */
1182    return alloc_page_vma(gfp, &pvma, 0);
1183}
1184#else /* !CONFIG_NUMA */
1185#ifdef CONFIG_TMPFS
1186static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *p)
1187{
1188}
1189#endif /* CONFIG_TMPFS */
1190
1191static inline struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
1192            struct shmem_inode_info *info, unsigned long idx)
1193{
1194    return swapin_readahead(entry, gfp, NULL, 0);
1195}
1196
1197static inline struct page *shmem_alloc_page(gfp_t gfp,
1198            struct shmem_inode_info *info, unsigned long idx)
1199{
1200    return alloc_page(gfp);
1201}
1202#endif /* CONFIG_NUMA */
1203
1204#if !defined(CONFIG_NUMA) || !defined(CONFIG_TMPFS)
1205static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
1206{
1207    return NULL;
1208}
1209#endif
1210
1211/*
1212 * shmem_getpage - either get the page from swap or allocate a new one
1213 *
1214 * If we allocate a new one we do not mark it dirty. That's up to the
1215 * vm. If we swap it in we mark it dirty since we also free the swap
1216 * entry since a page cannot live in both the swap and page cache
1217 */
1218static int shmem_getpage(struct inode *inode, unsigned long idx,
1219            struct page **pagep, enum sgp_type sgp, int *type)
1220{
1221    struct address_space *mapping = inode->i_mapping;
1222    struct shmem_inode_info *info = SHMEM_I(inode);
1223    struct shmem_sb_info *sbinfo;
1224    struct page *filepage = *pagep;
1225    struct page *swappage;
1226    struct page *prealloc_page = NULL;
1227    swp_entry_t *entry;
1228    swp_entry_t swap;
1229    gfp_t gfp;
1230    int error;
1231
1232    if (idx >= SHMEM_MAX_INDEX)
1233        return -EFBIG;
1234
1235    if (type)
1236        *type = 0;
1237
1238    /*
1239     * Normally, filepage is NULL on entry, and either found
1240     * uptodate immediately, or allocated and zeroed, or read
1241     * in under swappage, which is then assigned to filepage.
1242     * But shmem_readpage (required for splice) passes in a locked
1243     * filepage, which may be found not uptodate by other callers
1244     * too, and may need to be copied from the swappage read in.
1245     */
1246repeat:
1247    if (!filepage)
1248        filepage = find_lock_page(mapping, idx);
1249    if (filepage && PageUptodate(filepage))
1250        goto done;
1251    gfp = mapping_gfp_mask(mapping);
1252    if (!filepage) {
1253        /*
1254         * Try to preload while we can wait, to not make a habit of
1255         * draining atomic reserves; but don't latch on to this cpu.
1256         */
1257        error = radix_tree_preload(gfp & ~__GFP_HIGHMEM);
1258        if (error)
1259            goto failed;
1260        radix_tree_preload_end();
1261        if (sgp != SGP_READ && !prealloc_page) {
1262            /* We don't care if this fails */
1263            prealloc_page = shmem_alloc_page(gfp, info, idx);
1264            if (prealloc_page) {
1265                if (mem_cgroup_cache_charge(prealloc_page,
1266                        current->mm, GFP_KERNEL)) {
1267                    page_cache_release(prealloc_page);
1268                    prealloc_page = NULL;
1269                }
1270            }
1271        }
1272    }
1273    error = 0;
1274
1275    spin_lock(&info->lock);
1276    shmem_recalc_inode(inode);
1277    entry = shmem_swp_alloc(info, idx, sgp);
1278    if (IS_ERR(entry)) {
1279        spin_unlock(&info->lock);
1280        error = PTR_ERR(entry);
1281        goto failed;
1282    }
1283    swap = *entry;
1284
1285    if (swap.val) {
1286        /* Look it up and read it in.. */
1287        swappage = lookup_swap_cache(swap);
1288        if (!swappage) {
1289            shmem_swp_unmap(entry);
1290            /* here we actually do the io */
1291            if (type && !(*type & VM_FAULT_MAJOR)) {
1292                __count_vm_event(PGMAJFAULT);
1293                *type |= VM_FAULT_MAJOR;
1294            }
1295            spin_unlock(&info->lock);
1296            swappage = shmem_swapin(swap, gfp, info, idx);
1297            if (!swappage) {
1298                spin_lock(&info->lock);
1299                entry = shmem_swp_alloc(info, idx, sgp);
1300                if (IS_ERR(entry))
1301                    error = PTR_ERR(entry);
1302                else {
1303                    if (entry->val == swap.val)
1304                        error = -ENOMEM;
1305                    shmem_swp_unmap(entry);
1306                }
1307                spin_unlock(&info->lock);
1308                if (error)
1309                    goto failed;
1310                goto repeat;
1311            }
1312            wait_on_page_locked(swappage);
1313            page_cache_release(swappage);
1314            goto repeat;
1315        }
1316
1317        /* We have to do this with page locked to prevent races */
1318        if (!trylock_page(swappage)) {
1319            shmem_swp_unmap(entry);
1320            spin_unlock(&info->lock);
1321            wait_on_page_locked(swappage);
1322            page_cache_release(swappage);
1323            goto repeat;
1324        }
1325        if (PageWriteback(swappage)) {
1326            shmem_swp_unmap(entry);
1327            spin_unlock(&info->lock);
1328            wait_on_page_writeback(swappage);
1329            unlock_page(swappage);
1330            page_cache_release(swappage);
1331            goto repeat;
1332        }
1333        if (!PageUptodate(swappage)) {
1334            shmem_swp_unmap(entry);
1335            spin_unlock(&info->lock);
1336            unlock_page(swappage);
1337            page_cache_release(swappage);
1338            error = -EIO;
1339            goto failed;
1340        }
1341
1342        if (filepage) {
1343            shmem_swp_set(info, entry, 0);
1344            shmem_swp_unmap(entry);
1345            delete_from_swap_cache(swappage);
1346            spin_unlock(&info->lock);
1347            copy_highpage(filepage, swappage);
1348            unlock_page(swappage);
1349            page_cache_release(swappage);
1350            flush_dcache_page(filepage);
1351            SetPageUptodate(filepage);
1352            set_page_dirty(filepage);
1353            swap_free(swap);
1354        } else if (!(error = add_to_page_cache_locked(swappage, mapping,
1355                    idx, GFP_NOWAIT))) {
1356            info->flags |= SHMEM_PAGEIN;
1357            shmem_swp_set(info, entry, 0);
1358            shmem_swp_unmap(entry);
1359            delete_from_swap_cache(swappage);
1360            spin_unlock(&info->lock);
1361            filepage = swappage;
1362            set_page_dirty(filepage);
1363            swap_free(swap);
1364        } else {
1365            shmem_swp_unmap(entry);
1366            spin_unlock(&info->lock);
1367            if (error == -ENOMEM) {
1368                /*
1369                 * reclaim from proper memory cgroup and
1370                 * call memcg's OOM if needed.
1371                 */
1372                error = mem_cgroup_shmem_charge_fallback(
1373                                swappage,
1374                                current->mm,
1375                                gfp);
1376                if (error) {
1377                    unlock_page(swappage);
1378                    page_cache_release(swappage);
1379                    goto failed;
1380                }
1381            }
1382            unlock_page(swappage);
1383            page_cache_release(swappage);
1384            goto repeat;
1385        }
1386    } else if (sgp == SGP_READ && !filepage) {
1387        shmem_swp_unmap(entry);
1388        filepage = find_get_page(mapping, idx);
1389        if (filepage &&
1390            (!PageUptodate(filepage) || !trylock_page(filepage))) {
1391            spin_unlock(&info->lock);
1392            wait_on_page_locked(filepage);
1393            page_cache_release(filepage);
1394            filepage = NULL;
1395            goto repeat;
1396        }
1397        spin_unlock(&info->lock);
1398    } else {
1399        shmem_swp_unmap(entry);
1400        sbinfo = SHMEM_SB(inode->i_sb);
1401        if (sbinfo->max_blocks) {
1402            if ((percpu_counter_compare(&sbinfo->used_blocks, sbinfo->max_blocks) > 0) ||
1403                shmem_acct_block(info->flags)) {
1404                spin_unlock(&info->lock);
1405                error = -ENOSPC;
1406                goto failed;
1407            }
1408            percpu_counter_inc(&sbinfo->used_blocks);
1409            spin_lock(&inode->i_lock);
1410            inode->i_blocks += BLOCKS_PER_PAGE;
1411            spin_unlock(&inode->i_lock);
1412        } else if (shmem_acct_block(info->flags)) {
1413            spin_unlock(&info->lock);
1414            error = -ENOSPC;
1415            goto failed;
1416        }
1417
1418        if (!filepage) {
1419            int ret;
1420
1421            if (!prealloc_page) {
1422                spin_unlock(&info->lock);
1423                filepage = shmem_alloc_page(gfp, info, idx);
1424                if (!filepage) {
1425                    shmem_unacct_blocks(info->flags, 1);
1426                    shmem_free_blocks(inode, 1);
1427                    error = -ENOMEM;
1428                    goto failed;
1429                }
1430                SetPageSwapBacked(filepage);
1431
1432                /*
1433                 * Precharge page while we can wait, compensate
1434                 * after
1435                 */
1436                error = mem_cgroup_cache_charge(filepage,
1437                    current->mm, GFP_KERNEL);
1438                if (error) {
1439                    page_cache_release(filepage);
1440                    shmem_unacct_blocks(info->flags, 1);
1441                    shmem_free_blocks(inode, 1);
1442                    filepage = NULL;
1443                    goto failed;
1444                }
1445
1446                spin_lock(&info->lock);
1447            } else {
1448                filepage = prealloc_page;
1449                prealloc_page = NULL;
1450                SetPageSwapBacked(filepage);
1451            }
1452
1453            entry = shmem_swp_alloc(info, idx, sgp);
1454            if (IS_ERR(entry))
1455                error = PTR_ERR(entry);
1456            else {
1457                swap = *entry;
1458                shmem_swp_unmap(entry);
1459            }
1460            ret = error || swap.val;
1461            if (ret)
1462                mem_cgroup_uncharge_cache_page(filepage);
1463            else
1464                ret = add_to_page_cache_lru(filepage, mapping,
1465                        idx, GFP_NOWAIT);
1466            /*
1467             * At add_to_page_cache_lru() failure, uncharge will
1468             * be done automatically.
1469             */
1470            if (ret) {
1471                spin_unlock(&info->lock);
1472                page_cache_release(filepage);
1473                shmem_unacct_blocks(info->flags, 1);
1474                shmem_free_blocks(inode, 1);
1475                filepage = NULL;
1476                if (error)
1477                    goto failed;
1478                goto repeat;
1479            }
1480            info->flags |= SHMEM_PAGEIN;
1481        }
1482
1483        info->alloced++;
1484        spin_unlock(&info->lock);
1485        clear_highpage(filepage);
1486        flush_dcache_page(filepage);
1487        SetPageUptodate(filepage);
1488        if (sgp == SGP_DIRTY)
1489            set_page_dirty(filepage);
1490    }
1491done:
1492    *pagep = filepage;
1493    error = 0;
1494    goto out;
1495
1496failed:
1497    if (*pagep != filepage) {
1498        unlock_page(filepage);
1499        page_cache_release(filepage);
1500    }
1501out:
1502    if (prealloc_page) {
1503        mem_cgroup_uncharge_cache_page(prealloc_page);
1504        page_cache_release(prealloc_page);
1505    }
1506    return error;
1507}
1508
1509static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1510{
1511    struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1512    int error;
1513    int ret;
1514
1515    if (((loff_t)vmf->pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
1516        return VM_FAULT_SIGBUS;
1517
1518    error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret);
1519    if (error)
1520        return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
1521
1522    return ret | VM_FAULT_LOCKED;
1523}
1524
1525#ifdef CONFIG_NUMA
1526static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *new)
1527{
1528    struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1529    return mpol_set_shared_policy(&SHMEM_I(i)->policy, vma, new);
1530}
1531
1532static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
1533                      unsigned long addr)
1534{
1535    struct inode *i = vma->vm_file->f_path.dentry->d_inode;
1536    unsigned long idx;
1537
1538    idx = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
1539    return mpol_shared_policy_lookup(&SHMEM_I(i)->policy, idx);
1540}
1541#endif
1542
1543int shmem_lock(struct file *file, int lock, struct user_struct *user)
1544{
1545    struct inode *inode = file->f_path.dentry->d_inode;
1546    struct shmem_inode_info *info = SHMEM_I(inode);
1547    int retval = -ENOMEM;
1548
1549    spin_lock(&info->lock);
1550    if (lock && !(info->flags & VM_LOCKED)) {
1551        if (!user_shm_lock(inode->i_size, user))
1552            goto out_nomem;
1553        info->flags |= VM_LOCKED;
1554        mapping_set_unevictable(file->f_mapping);
1555    }
1556    if (!lock && (info->flags & VM_LOCKED) && user) {
1557        user_shm_unlock(inode->i_size, user);
1558        info->flags &= ~VM_LOCKED;
1559        mapping_clear_unevictable(file->f_mapping);
1560        scan_mapping_unevictable_pages(file->f_mapping);
1561    }
1562    retval = 0;
1563
1564out_nomem:
1565    spin_unlock(&info->lock);
1566    return retval;
1567}
1568
1569static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
1570{
1571    file_accessed(file);
1572    vma->vm_ops = &shmem_vm_ops;
1573    vma->vm_flags |= VM_CAN_NONLINEAR;
1574    return 0;
1575}
1576
1577static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir,
1578                     int mode, dev_t dev, unsigned long flags)
1579{
1580    struct inode *inode;
1581    struct shmem_inode_info *info;
1582    struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
1583
1584    if (shmem_reserve_inode(sb))
1585        return NULL;
1586
1587    inode = new_inode(sb);
1588    if (inode) {
1589        inode_init_owner(inode, dir, mode);
1590        inode->i_blocks = 0;
1591        inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
1592        inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1593        inode->i_generation = get_seconds();
1594        info = SHMEM_I(inode);
1595        memset(info, 0, (char *)inode - (char *)info);
1596        spin_lock_init(&info->lock);
1597        info->flags = flags & VM_NORESERVE;
1598        INIT_LIST_HEAD(&info->swaplist);
1599        cache_no_acl(inode);
1600
1601        switch (mode & S_IFMT) {
1602        default:
1603            inode->i_op = &shmem_special_inode_operations;
1604            init_special_inode(inode, mode, dev);
1605            break;
1606        case S_IFREG:
1607            inode->i_mapping->a_ops = &shmem_aops;
1608            inode->i_op = &shmem_inode_operations;
1609            inode->i_fop = &shmem_file_operations;
1610            mpol_shared_policy_init(&info->policy,
1611                         shmem_get_sbmpol(sbinfo));
1612            break;
1613        case S_IFDIR:
1614            inc_nlink(inode);
1615            /* Some things misbehave if size == 0 on a directory */
1616            inode->i_size = 2 * BOGO_DIRENT_SIZE;
1617            inode->i_op = &shmem_dir_inode_operations;
1618            inode->i_fop = &simple_dir_operations;
1619            break;
1620        case S_IFLNK:
1621            /*
1622             * Must not load anything in the rbtree,
1623             * mpol_free_shared_policy will not be called.
1624             */
1625            mpol_shared_policy_init(&info->policy, NULL);
1626            break;
1627        }
1628    } else
1629        shmem_free_inode(sb);
1630    return inode;
1631}
1632
1633#ifdef CONFIG_TMPFS
1634static const struct inode_operations shmem_symlink_inode_operations;
1635static const struct inode_operations shmem_symlink_inline_operations;
1636
1637/*
1638 * Normally tmpfs avoids the use of shmem_readpage and shmem_write_begin;
1639 * but providing them allows a tmpfs file to be used for splice, sendfile, and
1640 * below the loop driver, in the generic fashion that many filesystems support.
1641 */
1642static int shmem_readpage(struct file *file, struct page *page)
1643{
1644    struct inode *inode = page->mapping->host;
1645    int error = shmem_getpage(inode, page->index, &page, SGP_CACHE, NULL);
1646    unlock_page(page);
1647    return error;
1648}
1649
1650static int
1651shmem_write_begin(struct file *file, struct address_space *mapping,
1652            loff_t pos, unsigned len, unsigned flags,
1653            struct page **pagep, void **fsdata)
1654{
1655    struct inode *inode = mapping->host;
1656    pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1657    *pagep = NULL;
1658    return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
1659}
1660
1661static int
1662shmem_write_end(struct file *file, struct address_space *mapping,
1663            loff_t pos, unsigned len, unsigned copied,
1664            struct page *page, void *fsdata)
1665{
1666    struct inode *inode = mapping->host;
1667
1668    if (pos + copied > inode->i_size)
1669        i_size_write(inode, pos + copied);
1670
1671    set_page_dirty(page);
1672    unlock_page(page);
1673    page_cache_release(page);
1674
1675    return copied;
1676}
1677
1678static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
1679{
1680    struct inode *inode = filp->f_path.dentry->d_inode;
1681    struct address_space *mapping = inode->i_mapping;
1682    unsigned long index, offset;
1683    enum sgp_type sgp = SGP_READ;
1684
1685    /*
1686     * Might this read be for a stacking filesystem? Then when reading
1687     * holes of a sparse file, we actually need to allocate those pages,
1688     * and even mark them dirty, so it cannot exceed the max_blocks limit.
1689     */
1690    if (segment_eq(get_fs(), KERNEL_DS))
1691        sgp = SGP_DIRTY;
1692
1693    index = *ppos >> PAGE_CACHE_SHIFT;
1694    offset = *ppos & ~PAGE_CACHE_MASK;
1695
1696    for (;;) {
1697        struct page *page = NULL;
1698        unsigned long end_index, nr, ret;
1699        loff_t i_size = i_size_read(inode);
1700
1701        end_index = i_size >> PAGE_CACHE_SHIFT;
1702        if (index > end_index)
1703            break;
1704        if (index == end_index) {
1705            nr = i_size & ~PAGE_CACHE_MASK;
1706            if (nr <= offset)
1707                break;
1708        }
1709
1710        desc->error = shmem_getpage(inode, index, &page, sgp, NULL);
1711        if (desc->error) {
1712            if (desc->error == -EINVAL)
1713                desc->error = 0;
1714            break;
1715        }
1716        if (page)
1717            unlock_page(page);
1718
1719        /*
1720         * We must evaluate after, since reads (unlike writes)
1721         * are called without i_mutex protection against truncate
1722         */
1723        nr = PAGE_CACHE_SIZE;
1724        i_size = i_size_read(inode);
1725        end_index = i_size >> PAGE_CACHE_SHIFT;
1726        if (index == end_index) {
1727            nr = i_size & ~PAGE_CACHE_MASK;
1728            if (nr <= offset) {
1729                if (page)
1730                    page_cache_release(page);
1731                break;
1732            }
1733        }
1734        nr -= offset;
1735
1736        if (page) {
1737            /*
1738             * If users can be writing to this page using arbitrary
1739             * virtual addresses, take care about potential aliasing
1740             * before reading the page on the kernel side.
1741             */
1742            if (mapping_writably_mapped(mapping))
1743                flush_dcache_page(page);
1744            /*
1745             * Mark the page accessed if we read the beginning.
1746             */
1747            if (!offset)
1748                mark_page_accessed(page);
1749        } else {
1750            page = ZERO_PAGE(0);
1751            page_cache_get(page);
1752        }
1753
1754        /*
1755         * Ok, we have the page, and it's up-to-date, so
1756         * now we can copy it to user space...
1757         *
1758         * The actor routine returns how many bytes were actually used..
1759         * NOTE! This may not be the same as how much of a user buffer
1760         * we filled up (we may be padding etc), so we can only update
1761         * "pos" here (the actor routine has to update the user buffer
1762         * pointers and the remaining count).
1763         */
1764        ret = actor(desc, page, offset, nr);
1765        offset += ret;
1766        index += offset >> PAGE_CACHE_SHIFT;
1767        offset &= ~PAGE_CACHE_MASK;
1768
1769        page_cache_release(page);
1770        if (ret != nr || !desc->count)
1771            break;
1772
1773        cond_resched();
1774    }
1775
1776    *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
1777    file_accessed(filp);
1778}
1779
1780static ssize_t shmem_file_aio_read(struct kiocb *iocb,
1781        const struct iovec *iov, unsigned long nr_segs, loff_t pos)
1782{
1783    struct file *filp = iocb->ki_filp;
1784    ssize_t retval;
1785    unsigned long seg;
1786    size_t count;
1787    loff_t *ppos = &iocb->ki_pos;
1788
1789    retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1790    if (retval)
1791        return retval;
1792
1793    for (seg = 0; seg < nr_segs; seg++) {
1794        read_descriptor_t desc;
1795
1796        desc.written = 0;
1797        desc.arg.buf = iov[seg].iov_base;
1798        desc.count = iov[seg].iov_len;
1799        if (desc.count == 0)
1800            continue;
1801        desc.error = 0;
1802        do_shmem_file_read(filp, ppos, &desc, file_read_actor);
1803        retval += desc.written;
1804        if (desc.error) {
1805            retval = retval ?: desc.error;
1806            break;
1807        }
1808        if (desc.count > 0)
1809            break;
1810    }
1811    return retval;
1812}
1813
1814static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
1815{
1816    struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
1817
1818    buf->f_type = TMPFS_MAGIC;
1819    buf->f_bsize = PAGE_CACHE_SIZE;
1820    buf->f_namelen = NAME_MAX;
1821    if (sbinfo->max_blocks) {
1822        buf->f_blocks = sbinfo->max_blocks;
1823        buf->f_bavail = buf->f_bfree =
1824                sbinfo->max_blocks - percpu_counter_sum(&sbinfo->used_blocks);
1825    }
1826    if (sbinfo->max_inodes) {
1827        buf->f_files = sbinfo->max_inodes;
1828        buf->f_ffree = sbinfo->free_inodes;
1829    }
1830    /* else leave those fields 0 like simple_statfs */
1831    return 0;
1832}
1833
1834/*
1835 * File creation. Allocate an inode, and we're done..
1836 */
1837static int
1838shmem_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
1839{
1840    struct inode *inode;
1841    int error = -ENOSPC;
1842
1843    inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
1844    if (inode) {
1845        error = security_inode_init_security(inode, dir, NULL, NULL,
1846                             NULL);
1847        if (error) {
1848            if (error != -EOPNOTSUPP) {
1849                iput(inode);
1850                return error;
1851            }
1852        }
1853#ifdef CONFIG_TMPFS_POSIX_ACL
1854        error = generic_acl_init(inode, dir);
1855        if (error) {
1856            iput(inode);
1857            return error;
1858        }
1859#else
1860        error = 0;
1861#endif
1862        dir->i_size += BOGO_DIRENT_SIZE;
1863        dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1864        d_instantiate(dentry, inode);
1865        dget(dentry); /* Extra count - pin the dentry in core */
1866    }
1867    return error;
1868}
1869
1870static int shmem_mkdir(struct inode *dir, struct dentry *dentry, int mode)
1871{
1872    int error;
1873
1874    if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
1875        return error;
1876    inc_nlink(dir);
1877    return 0;
1878}
1879
1880static int shmem_create(struct inode *dir, struct dentry *dentry, int mode,
1881        struct nameidata *nd)
1882{
1883    return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
1884}
1885
1886/*
1887 * Link a file..
1888 */
1889static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
1890{
1891    struct inode *inode = old_dentry->d_inode;
1892    int ret;
1893
1894    /*
1895     * No ordinary (disk based) filesystem counts links as inodes;
1896     * but each new link needs a new dentry, pinning lowmem, and
1897     * tmpfs dentries cannot be pruned until they are unlinked.
1898     */
1899    ret = shmem_reserve_inode(inode->i_sb);
1900    if (ret)
1901        goto out;
1902
1903    dir->i_size += BOGO_DIRENT_SIZE;
1904    inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1905    inc_nlink(inode);
1906    atomic_inc(&inode->i_count); /* New dentry reference */
1907    dget(dentry); /* Extra pinning count for the created dentry */
1908    d_instantiate(dentry, inode);
1909out:
1910    return ret;
1911}
1912
1913static int shmem_unlink(struct inode *dir, struct dentry *dentry)
1914{
1915    struct inode *inode = dentry->d_inode;
1916
1917    if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
1918        shmem_free_inode(inode->i_sb);
1919
1920    dir->i_size -= BOGO_DIRENT_SIZE;
1921    inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
1922    drop_nlink(inode);
1923    dput(dentry); /* Undo the count from "create" - this does all the work */
1924    return 0;
1925}
1926
1927static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
1928{
1929    if (!simple_empty(dentry))
1930        return -ENOTEMPTY;
1931
1932    drop_nlink(dentry->d_inode);
1933    drop_nlink(dir);
1934    return shmem_unlink(dir, dentry);
1935}
1936
1937/*
1938 * The VFS layer already does all the dentry stuff for rename,
1939 * we just have to decrement the usage count for the target if
1940 * it exists so that the VFS layer correctly free's it when it
1941 * gets overwritten.
1942 */
1943static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
1944{
1945    struct inode *inode = old_dentry->d_inode;
1946    int they_are_dirs = S_ISDIR(inode->i_mode);
1947
1948    if (!simple_empty(new_dentry))
1949        return -ENOTEMPTY;
1950
1951    if (new_dentry->d_inode) {
1952        (void) shmem_unlink(new_dir, new_dentry);
1953        if (they_are_dirs)
1954            drop_nlink(old_dir);
1955    } else if (they_are_dirs) {
1956        drop_nlink(old_dir);
1957        inc_nlink(new_dir);
1958    }
1959
1960    old_dir->i_size -= BOGO_DIRENT_SIZE;
1961    new_dir->i_size += BOGO_DIRENT_SIZE;
1962    old_dir->i_ctime = old_dir->i_mtime =
1963    new_dir->i_ctime = new_dir->i_mtime =
1964    inode->i_ctime = CURRENT_TIME;
1965    return 0;
1966}
1967
1968static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
1969{
1970    int error;
1971    int len;
1972    struct inode *inode;
1973    struct page *page = NULL;
1974    char *kaddr;
1975    struct shmem_inode_info *info;
1976
1977    len = strlen(symname) + 1;
1978    if (len > PAGE_CACHE_SIZE)
1979        return -ENAMETOOLONG;
1980
1981    inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0, VM_NORESERVE);
1982    if (!inode)
1983        return -ENOSPC;
1984
1985    error = security_inode_init_security(inode, dir, NULL, NULL,
1986                         NULL);
1987    if (error) {
1988        if (error != -EOPNOTSUPP) {
1989            iput(inode);
1990            return error;
1991        }
1992        error = 0;
1993    }
1994
1995    info = SHMEM_I(inode);
1996    inode->i_size = len-1;
1997    if (len <= (char *)inode - (char *)info) {
1998        /* do it inline */
1999        memcpy(info, symname, len);
2000        inode->i_op = &shmem_symlink_inline_operations;
2001    } else {
2002        error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
2003        if (error) {
2004            iput(inode);
2005            return error;
2006        }
2007        inode->i_mapping->a_ops = &shmem_aops;
2008        inode->i_op = &shmem_symlink_inode_operations;
2009        kaddr = kmap_atomic(page, KM_USER0);
2010        memcpy(kaddr, symname, len);
2011        kunmap_atomic(kaddr, KM_USER0);
2012        set_page_dirty(page);
2013        unlock_page(page);
2014        page_cache_release(page);
2015    }
2016    dir->i_size += BOGO_DIRENT_SIZE;
2017    dir->i_ctime = dir->i_mtime = CURRENT_TIME;
2018    d_instantiate(dentry, inode);
2019    dget(dentry);
2020    return 0;
2021}
2022
2023static void *shmem_follow_link_inline(struct dentry *dentry, struct nameidata *nd)
2024{
2025    nd_set_link(nd, (char *)SHMEM_I(dentry->d_inode));
2026    return NULL;
2027}
2028
2029static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
2030{
2031    struct page *page = NULL;
2032    int res = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
2033    nd_set_link(nd, res ? ERR_PTR(res) : kmap(page));
2034    if (page)
2035        unlock_page(page);
2036    return page;
2037}
2038
2039static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
2040{
2041    if (!IS_ERR(nd_get_link(nd))) {
2042        struct page *page = cookie;
2043        kunmap(page);
2044        mark_page_accessed(page);
2045        page_cache_release(page);
2046    }
2047}
2048
2049static const struct inode_operations shmem_symlink_inline_operations = {
2050    .readlink = generic_readlink,
2051    .follow_link = shmem_follow_link_inline,
2052};
2053
2054static const struct inode_operations shmem_symlink_inode_operations = {
2055    .readlink = generic_readlink,
2056    .follow_link = shmem_follow_link,
2057    .put_link = shmem_put_link,
2058};
2059
2060#ifdef CONFIG_TMPFS_POSIX_ACL
2061/*
2062 * Superblocks without xattr inode operations will get security.* xattr
2063 * support from the VFS "for free". As soon as we have any other xattrs
2064 * like ACLs, we also need to implement the security.* handlers at
2065 * filesystem level, though.
2066 */
2067
2068static size_t shmem_xattr_security_list(struct dentry *dentry, char *list,
2069                    size_t list_len, const char *name,
2070                    size_t name_len, int handler_flags)
2071{
2072    return security_inode_listsecurity(dentry->d_inode, list, list_len);
2073}
2074
2075static int shmem_xattr_security_get(struct dentry *dentry, const char *name,
2076        void *buffer, size_t size, int handler_flags)
2077{
2078    if (strcmp(name, "") == 0)
2079        return -EINVAL;
2080    return xattr_getsecurity(dentry->d_inode, name, buffer, size);
2081}
2082
2083static int shmem_xattr_security_set(struct dentry *dentry, const char *name,
2084        const void *value, size_t size, int flags, int handler_flags)
2085{
2086    if (strcmp(name, "") == 0)
2087        return -EINVAL;
2088    return security_inode_setsecurity(dentry->d_inode, name, value,
2089                      size, flags);
2090}
2091
2092static const struct xattr_handler shmem_xattr_security_handler = {
2093    .prefix = XATTR_SECURITY_PREFIX,
2094    .list = shmem_xattr_security_list,
2095    .get = shmem_xattr_security_get,
2096    .set = shmem_xattr_security_set,
2097};
2098
2099static const struct xattr_handler *shmem_xattr_handlers[] = {
2100    &generic_acl_access_handler,
2101    &generic_acl_default_handler,
2102    &shmem_xattr_security_handler,
2103    NULL
2104};
2105#endif
2106
2107static struct dentry *shmem_get_parent(struct dentry *child)
2108{
2109    return ERR_PTR(-ESTALE);
2110}
2111
2112static int shmem_match(struct inode *ino, void *vfh)
2113{
2114    __u32 *fh = vfh;
2115    __u64 inum = fh[2];
2116    inum = (inum << 32) | fh[1];
2117    return ino->i_ino == inum && fh[0] == ino->i_generation;
2118}
2119
2120static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
2121        struct fid *fid, int fh_len, int fh_type)
2122{
2123    struct inode *inode;
2124    struct dentry *dentry = NULL;
2125    u64 inum = fid->raw[2];
2126    inum = (inum << 32) | fid->raw[1];
2127
2128    if (fh_len < 3)
2129        return NULL;
2130
2131    inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
2132            shmem_match, fid->raw);
2133    if (inode) {
2134        dentry = d_find_alias(inode);
2135        iput(inode);
2136    }
2137
2138    return dentry;
2139}
2140
2141static int shmem_encode_fh(struct dentry *dentry, __u32 *fh, int *len,
2142                int connectable)
2143{
2144    struct inode *inode = dentry->d_inode;
2145
2146    if (*len < 3)
2147        return 255;
2148
2149    if (hlist_unhashed(&inode->i_hash)) {
2150        /* Unfortunately insert_inode_hash is not idempotent,
2151         * so as we hash inodes here rather than at creation
2152         * time, we need a lock to ensure we only try
2153         * to do it once
2154         */
2155        static DEFINE_SPINLOCK(lock);
2156        spin_lock(&lock);
2157        if (hlist_unhashed(&inode->i_hash))
2158            __insert_inode_hash(inode,
2159                        inode->i_ino + inode->i_generation);
2160        spin_unlock(&lock);
2161    }
2162
2163    fh[0] = inode->i_generation;
2164    fh[1] = inode->i_ino;
2165    fh[2] = ((__u64)inode->i_ino) >> 32;
2166
2167    *len = 3;
2168    return 1;
2169}
2170
2171static const struct export_operations shmem_export_ops = {
2172    .get_parent = shmem_get_parent,
2173    .encode_fh = shmem_encode_fh,
2174    .fh_to_dentry = shmem_fh_to_dentry,
2175};
2176
2177static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
2178                   bool remount)
2179{
2180    char *this_char, *value, *rest;
2181
2182    while (options != NULL) {
2183        this_char = options;
2184        for (;;) {
2185            /*
2186             * NUL-terminate this option: unfortunately,
2187             * mount options form a comma-separated list,
2188             * but mpol's nodelist may also contain commas.
2189             */
2190            options = strchr(options, ',');
2191            if (options == NULL)
2192                break;
2193            options++;
2194            if (!isdigit(*options)) {
2195                options[-1] = '\0';
2196                break;
2197            }
2198        }
2199        if (!*this_char)
2200            continue;
2201        if ((value = strchr(this_char,'=')) != NULL) {
2202            *value++ = 0;
2203        } else {
2204            printk(KERN_ERR
2205                "tmpfs: No value for mount option '%s'\n",
2206                this_char);
2207            return 1;
2208        }
2209
2210        if (!strcmp(this_char,"size")) {
2211            unsigned long long size;
2212            size = memparse(value,&rest);
2213            if (*rest == '%') {
2214                size <<= PAGE_SHIFT;
2215                size *= totalram_pages;
2216                do_div(size, 100);
2217                rest++;
2218            }
2219            if (*rest)
2220                goto bad_val;
2221            sbinfo->max_blocks =
2222                DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
2223        } else if (!strcmp(this_char,"nr_blocks")) {
2224            sbinfo->max_blocks = memparse(value, &rest);
2225            if (*rest)
2226                goto bad_val;
2227        } else if (!strcmp(this_char,"nr_inodes")) {
2228            sbinfo->max_inodes = memparse(value, &rest);
2229            if (*rest)
2230                goto bad_val;
2231        } else if (!strcmp(this_char,"mode")) {
2232            if (remount)
2233                continue;
2234            sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
2235            if (*rest)
2236                goto bad_val;
2237        } else if (!strcmp(this_char,"uid")) {
2238            if (remount)
2239                continue;
2240            sbinfo->uid = simple_strtoul(value, &rest, 0);
2241            if (*rest)
2242                goto bad_val;
2243        } else if (!strcmp(this_char,"gid")) {
2244            if (remount)
2245                continue;
2246            sbinfo->gid = simple_strtoul(value, &rest, 0);
2247            if (*rest)
2248                goto bad_val;
2249        } else if (!strcmp(this_char,"mpol")) {
2250            if (mpol_parse_str(value, &sbinfo->mpol, 1))
2251                goto bad_val;
2252        } else {
2253            printk(KERN_ERR "tmpfs: Bad mount option %s\n",
2254                   this_char);
2255            return 1;
2256        }
2257    }
2258    return 0;
2259
2260bad_val:
2261    printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
2262           value, this_char);
2263    return 1;
2264
2265}
2266
2267static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
2268{
2269    struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2270    struct shmem_sb_info config = *sbinfo;
2271    unsigned long inodes;
2272    int error = -EINVAL;
2273
2274    if (shmem_parse_options(data, &config, true))
2275        return error;
2276
2277    spin_lock(&sbinfo->stat_lock);
2278    inodes = sbinfo->max_inodes - sbinfo->free_inodes;
2279    if (percpu_counter_compare(&sbinfo->used_blocks, config.max_blocks) > 0)
2280        goto out;
2281    if (config.max_inodes < inodes)
2282        goto out;
2283    /*
2284     * Those tests also disallow limited->unlimited while any are in
2285     * use, so i_blocks will always be zero when max_blocks is zero;
2286     * but we must separately disallow unlimited->limited, because
2287     * in that case we have no record of how much is already in use.
2288     */
2289    if (config.max_blocks && !sbinfo->max_blocks)
2290        goto out;
2291    if (config.max_inodes && !sbinfo->max_inodes)
2292        goto out;
2293
2294    error = 0;
2295    sbinfo->max_blocks = config.max_blocks;
2296    sbinfo->max_inodes = config.max_inodes;
2297    sbinfo->free_inodes = config.max_inodes - inodes;
2298
2299    mpol_put(sbinfo->mpol);
2300    sbinfo->mpol = config.mpol; /* transfers initial ref */
2301out:
2302    spin_unlock(&sbinfo->stat_lock);
2303    return error;
2304}
2305
2306static int shmem_show_options(struct seq_file *seq, struct vfsmount *vfs)
2307{
2308    struct shmem_sb_info *sbinfo = SHMEM_SB(vfs->mnt_sb);
2309
2310    if (sbinfo->max_blocks != shmem_default_max_blocks())
2311        seq_printf(seq, ",size=%luk",
2312            sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10));
2313    if (sbinfo->max_inodes != shmem_default_max_inodes())
2314        seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
2315    if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
2316        seq_printf(seq, ",mode=%03o", sbinfo->mode);
2317    if (sbinfo->uid != 0)
2318        seq_printf(seq, ",uid=%u", sbinfo->uid);
2319    if (sbinfo->gid != 0)
2320        seq_printf(seq, ",gid=%u", sbinfo->gid);
2321    shmem_show_mpol(seq, sbinfo->mpol);
2322    return 0;
2323}
2324#endif /* CONFIG_TMPFS */
2325
2326static void shmem_put_super(struct super_block *sb)
2327{
2328    struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
2329
2330    percpu_counter_destroy(&sbinfo->used_blocks);
2331    kfree(sbinfo);
2332    sb->s_fs_info = NULL;
2333}
2334
2335int shmem_fill_super(struct super_block *sb, void *data, int silent)
2336{
2337    struct inode *inode;
2338    struct dentry *root;
2339    struct shmem_sb_info *sbinfo;
2340    int err = -ENOMEM;
2341
2342    /* Round up to L1_CACHE_BYTES to resist false sharing */
2343    sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
2344                L1_CACHE_BYTES), GFP_KERNEL);
2345    if (!sbinfo)
2346        return -ENOMEM;
2347
2348    sbinfo->mode = S_IRWXUGO | S_ISVTX;
2349    sbinfo->uid = current_fsuid();
2350    sbinfo->gid = current_fsgid();
2351    sb->s_fs_info = sbinfo;
2352
2353#ifdef CONFIG_TMPFS
2354    /*
2355     * Per default we only allow half of the physical ram per
2356     * tmpfs instance, limiting inodes to one per page of lowmem;
2357     * but the internal instance is left unlimited.
2358     */
2359    if (!(sb->s_flags & MS_NOUSER)) {
2360        sbinfo->max_blocks = shmem_default_max_blocks();
2361        sbinfo->max_inodes = shmem_default_max_inodes();
2362        if (shmem_parse_options(data, sbinfo, false)) {
2363            err = -EINVAL;
2364            goto failed;
2365        }
2366    }
2367    sb->s_export_op = &shmem_export_ops;
2368#else
2369    sb->s_flags |= MS_NOUSER;
2370#endif
2371
2372    spin_lock_init(&sbinfo->stat_lock);
2373    if (percpu_counter_init(&sbinfo->used_blocks, 0))
2374        goto failed;
2375    sbinfo->free_inodes = sbinfo->max_inodes;
2376
2377    sb->s_maxbytes = SHMEM_MAX_BYTES;
2378    sb->s_blocksize = PAGE_CACHE_SIZE;
2379    sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
2380    sb->s_magic = TMPFS_MAGIC;
2381    sb->s_op = &shmem_ops;
2382    sb->s_time_gran = 1;
2383#ifdef CONFIG_TMPFS_POSIX_ACL
2384    sb->s_xattr = shmem_xattr_handlers;
2385    sb->s_flags |= MS_POSIXACL;
2386#endif
2387
2388    inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
2389    if (!inode)
2390        goto failed;
2391    inode->i_uid = sbinfo->uid;
2392    inode->i_gid = sbinfo->gid;
2393    root = d_alloc_root(inode);
2394    if (!root)
2395        goto failed_iput;
2396    sb->s_root = root;
2397    return 0;
2398
2399failed_iput:
2400    iput(inode);
2401failed:
2402    shmem_put_super(sb);
2403    return err;
2404}
2405
2406static struct kmem_cache *shmem_inode_cachep;
2407
2408static struct inode *shmem_alloc_inode(struct super_block *sb)
2409{
2410    struct shmem_inode_info *p;
2411    p = (struct shmem_inode_info *)kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
2412    if (!p)
2413        return NULL;
2414    return &p->vfs_inode;
2415}
2416
2417static void shmem_destroy_inode(struct inode *inode)
2418{
2419    if ((inode->i_mode & S_IFMT) == S_IFREG) {
2420        /* only struct inode is valid if it's an inline symlink */
2421        mpol_free_shared_policy(&SHMEM_I(inode)->policy);
2422    }
2423    kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
2424}
2425
2426static void init_once(void *foo)
2427{
2428    struct shmem_inode_info *p = (struct shmem_inode_info *) foo;
2429
2430    inode_init_once(&p->vfs_inode);
2431}
2432
2433static int init_inodecache(void)
2434{
2435    shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
2436                sizeof(struct shmem_inode_info),
2437                0, SLAB_PANIC, init_once);
2438    return 0;
2439}
2440
2441static void destroy_inodecache(void)
2442{
2443    kmem_cache_destroy(shmem_inode_cachep);
2444}
2445
2446static const struct address_space_operations shmem_aops = {
2447    .writepage = shmem_writepage,
2448    .set_page_dirty = __set_page_dirty_no_writeback,
2449#ifdef CONFIG_TMPFS
2450    .readpage = shmem_readpage,
2451    .write_begin = shmem_write_begin,
2452    .write_end = shmem_write_end,
2453#endif
2454    .migratepage = migrate_page,
2455    .error_remove_page = generic_error_remove_page,
2456};
2457
2458static const struct file_operations shmem_file_operations = {
2459    .mmap = shmem_mmap,
2460#ifdef CONFIG_TMPFS
2461    .llseek = generic_file_llseek,
2462    .read = do_sync_read,
2463    .write = do_sync_write,
2464    .aio_read = shmem_file_aio_read,
2465    .aio_write = generic_file_aio_write,
2466    .fsync = noop_fsync,
2467    .splice_read = generic_file_splice_read,
2468    .splice_write = generic_file_splice_write,
2469#endif
2470};
2471
2472static const struct inode_operations shmem_inode_operations = {
2473    .setattr = shmem_notify_change,
2474    .truncate_range = shmem_truncate_range,
2475#ifdef CONFIG_TMPFS_POSIX_ACL
2476    .setxattr = generic_setxattr,
2477    .getxattr = generic_getxattr,
2478    .listxattr = generic_listxattr,
2479    .removexattr = generic_removexattr,
2480    .check_acl = generic_check_acl,
2481#endif
2482
2483};
2484
2485static const struct inode_operations shmem_dir_inode_operations = {
2486#ifdef CONFIG_TMPFS
2487    .create = shmem_create,
2488    .lookup = simple_lookup,
2489    .link = shmem_link,
2490    .unlink = shmem_unlink,
2491    .symlink = shmem_symlink,
2492    .mkdir = shmem_mkdir,
2493    .rmdir = shmem_rmdir,
2494    .mknod = shmem_mknod,
2495    .rename = shmem_rename,
2496#endif
2497#ifdef CONFIG_TMPFS_POSIX_ACL
2498    .setattr = shmem_notify_change,
2499    .setxattr = generic_setxattr,
2500    .getxattr = generic_getxattr,
2501    .listxattr = generic_listxattr,
2502    .removexattr = generic_removexattr,
2503    .check_acl = generic_check_acl,
2504#endif
2505};
2506
2507static const struct inode_operations shmem_special_inode_operations = {
2508#ifdef CONFIG_TMPFS_POSIX_ACL
2509    .setattr = shmem_notify_change,
2510    .setxattr = generic_setxattr,
2511    .getxattr = generic_getxattr,
2512    .listxattr = generic_listxattr,
2513    .removexattr = generic_removexattr,
2514    .check_acl = generic_check_acl,
2515#endif
2516};
2517
2518static const struct super_operations shmem_ops = {
2519    .alloc_inode = shmem_alloc_inode,
2520    .destroy_inode = shmem_destroy_inode,
2521#ifdef CONFIG_TMPFS
2522    .statfs = shmem_statfs,
2523    .remount_fs = shmem_remount_fs,
2524    .show_options = shmem_show_options,
2525#endif
2526    .evict_inode = shmem_evict_inode,
2527    .drop_inode = generic_delete_inode,
2528    .put_super = shmem_put_super,
2529};
2530
2531static const struct vm_operations_struct shmem_vm_ops = {
2532    .fault = shmem_fault,
2533#ifdef CONFIG_NUMA
2534    .set_policy = shmem_set_policy,
2535    .get_policy = shmem_get_policy,
2536#endif
2537};
2538
2539
2540static int shmem_get_sb(struct file_system_type *fs_type,
2541    int flags, const char *dev_name, void *data, struct vfsmount *mnt)
2542{
2543    return get_sb_nodev(fs_type, flags, data, shmem_fill_super, mnt);
2544}
2545
2546static struct file_system_type tmpfs_fs_type = {
2547    .owner = THIS_MODULE,
2548    .name = "tmpfs",
2549    .get_sb = shmem_get_sb,
2550    .kill_sb = kill_litter_super,
2551};
2552
2553int __init init_tmpfs(void)
2554{
2555    int error;
2556
2557    error = bdi_init(&shmem_backing_dev_info);
2558    if (error)
2559        goto out4;
2560
2561    error = init_inodecache();
2562    if (error)
2563        goto out3;
2564
2565    error = register_filesystem(&tmpfs_fs_type);
2566    if (error) {
2567        printk(KERN_ERR "Could not register tmpfs\n");
2568        goto out2;
2569    }
2570
2571    shm_mnt = vfs_kern_mount(&tmpfs_fs_type, MS_NOUSER,
2572                tmpfs_fs_type.name, NULL);
2573    if (IS_ERR(shm_mnt)) {
2574        error = PTR_ERR(shm_mnt);
2575        printk(KERN_ERR "Could not kern_mount tmpfs\n");
2576        goto out1;
2577    }
2578    return 0;
2579
2580out1:
2581    unregister_filesystem(&tmpfs_fs_type);
2582out2:
2583    destroy_inodecache();
2584out3:
2585    bdi_destroy(&shmem_backing_dev_info);
2586out4:
2587    shm_mnt = ERR_PTR(error);
2588    return error;
2589}
2590
2591#ifdef CONFIG_CGROUP_MEM_RES_CTLR
2592/**
2593 * mem_cgroup_get_shmem_target - find a page or entry assigned to the shmem file
2594 * @inode: the inode to be searched
2595 * @pgoff: the offset to be searched
2596 * @pagep: the pointer for the found page to be stored
2597 * @ent: the pointer for the found swap entry to be stored
2598 *
2599 * If a page is found, refcount of it is incremented. Callers should handle
2600 * these refcount.
2601 */
2602void mem_cgroup_get_shmem_target(struct inode *inode, pgoff_t pgoff,
2603                    struct page **pagep, swp_entry_t *ent)
2604{
2605    swp_entry_t entry = { .val = 0 }, *ptr;
2606    struct page *page = NULL;
2607    struct shmem_inode_info *info = SHMEM_I(inode);
2608
2609    if ((pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
2610        goto out;
2611
2612    spin_lock(&info->lock);
2613    ptr = shmem_swp_entry(info, pgoff, NULL);
2614#ifdef CONFIG_SWAP
2615    if (ptr && ptr->val) {
2616        entry.val = ptr->val;
2617        page = find_get_page(&swapper_space, entry.val);
2618    } else
2619#endif
2620        page = find_get_page(inode->i_mapping, pgoff);
2621    if (ptr)
2622        shmem_swp_unmap(ptr);
2623    spin_unlock(&info->lock);
2624out:
2625    *pagep = page;
2626    *ent = entry;
2627}
2628#endif
2629
2630#else /* !CONFIG_SHMEM */
2631
2632/*
2633 * tiny-shmem: simple shmemfs and tmpfs using ramfs code
2634 *
2635 * This is intended for small system where the benefits of the full
2636 * shmem code (swap-backed and resource-limited) are outweighed by
2637 * their complexity. On systems without swap this code should be
2638 * effectively equivalent, but much lighter weight.
2639 */
2640
2641#include <linux/ramfs.h>
2642
2643static struct file_system_type tmpfs_fs_type = {
2644    .name = "tmpfs",
2645    .get_sb = ramfs_get_sb,
2646    .kill_sb = kill_litter_super,
2647};
2648
2649int __init init_tmpfs(void)
2650{
2651    BUG_ON(register_filesystem(&tmpfs_fs_type) != 0);
2652
2653    shm_mnt = kern_mount(&tmpfs_fs_type);
2654    BUG_ON(IS_ERR(shm_mnt));
2655
2656    return 0;
2657}
2658
2659int shmem_unuse(swp_entry_t entry, struct page *page)
2660{
2661    return 0;
2662}
2663
2664int shmem_lock(struct file *file, int lock, struct user_struct *user)
2665{
2666    return 0;
2667}
2668
2669#ifdef CONFIG_CGROUP_MEM_RES_CTLR
2670/**
2671 * mem_cgroup_get_shmem_target - find a page or entry assigned to the shmem file
2672 * @inode: the inode to be searched
2673 * @pgoff: the offset to be searched
2674 * @pagep: the pointer for the found page to be stored
2675 * @ent: the pointer for the found swap entry to be stored
2676 *
2677 * If a page is found, refcount of it is incremented. Callers should handle
2678 * these refcount.
2679 */
2680void mem_cgroup_get_shmem_target(struct inode *inode, pgoff_t pgoff,
2681                    struct page **pagep, swp_entry_t *ent)
2682{
2683    struct page *page = NULL;
2684
2685    if ((pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
2686        goto out;
2687    page = find_get_page(inode->i_mapping, pgoff);
2688out:
2689    *pagep = page;
2690    *ent = (swp_entry_t){ .val = 0 };
2691}
2692#endif
2693
2694#define shmem_vm_ops generic_file_vm_ops
2695#define shmem_file_operations ramfs_file_operations
2696#define shmem_get_inode(sb, dir, mode, dev, flags) ramfs_get_inode(sb, dir, mode, dev)
2697#define shmem_acct_size(flags, size) 0
2698#define shmem_unacct_size(flags, size) do {} while (0)
2699#define SHMEM_MAX_BYTES MAX_LFS_FILESIZE
2700
2701#endif /* CONFIG_SHMEM */
2702
2703/* common code */
2704
2705/**
2706 * shmem_file_setup - get an unlinked file living in tmpfs
2707 * @name: name for dentry (to be seen in /proc/<pid>/maps
2708 * @size: size to be set for the file
2709 * @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
2710 */
2711struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
2712{
2713    int error;
2714    struct file *file;
2715    struct inode *inode;
2716    struct path path;
2717    struct dentry *root;
2718    struct qstr this;
2719
2720    if (IS_ERR(shm_mnt))
2721        return (void *)shm_mnt;
2722
2723    if (size < 0 || size > SHMEM_MAX_BYTES)
2724        return ERR_PTR(-EINVAL);
2725
2726    if (shmem_acct_size(flags, size))
2727        return ERR_PTR(-ENOMEM);
2728
2729    error = -ENOMEM;
2730    this.name = name;
2731    this.len = strlen(name);
2732    this.hash = 0; /* will go */
2733    root = shm_mnt->mnt_root;
2734    path.dentry = d_alloc(root, &this);
2735    if (!path.dentry)
2736        goto put_memory;
2737    path.mnt = mntget(shm_mnt);
2738
2739    error = -ENOSPC;
2740    inode = shmem_get_inode(root->d_sb, NULL, S_IFREG | S_IRWXUGO, 0, flags);
2741    if (!inode)
2742        goto put_dentry;
2743
2744    d_instantiate(path.dentry, inode);
2745    inode->i_size = size;
2746    inode->i_nlink = 0; /* It is unlinked */
2747#ifndef CONFIG_MMU
2748    error = ramfs_nommu_expand_for_mapping(inode, size);
2749    if (error)
2750        goto put_dentry;
2751#endif
2752
2753    error = -ENFILE;
2754    file = alloc_file(&path, FMODE_WRITE | FMODE_READ,
2755          &shmem_file_operations);
2756    if (!file)
2757        goto put_dentry;
2758
2759    return file;
2760
2761put_dentry:
2762    path_put(&path);
2763put_memory:
2764    shmem_unacct_size(flags, size);
2765    return ERR_PTR(error);
2766}
2767EXPORT_SYMBOL_GPL(shmem_file_setup);
2768
2769/**
2770 * shmem_zero_setup - setup a shared anonymous mapping
2771 * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
2772 */
2773int shmem_zero_setup(struct vm_area_struct *vma)
2774{
2775    struct file *file;
2776    loff_t size = vma->vm_end - vma->vm_start;
2777
2778    file = shmem_file_setup("dev/zero", size, vma->vm_flags);
2779    if (IS_ERR(file))
2780        return PTR_ERR(file);
2781
2782    if (vma->vm_file)
2783        fput(vma->vm_file);
2784    vma->vm_file = file;
2785    vma->vm_ops = &shmem_vm_ops;
2786    return 0;
2787}
2788

Archive Download this file



interactive