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/*
* Resizable virtual memory filesystem for Linux.
*
* Copyright (C) 2000 Linus Torvalds.
* 2000 Transmeta Corp.
* 2000-2001 Christoph Rohland
* 2000-2001 SAP AG
* 2002 Red Hat Inc.
* Copyright (C) 2002-2005 Hugh Dickins.
* Copyright (C) 2002-2005 VERITAS Software Corporation.
* Copyright (C) 2004 Andi Kleen, SuSE Labs
*
* Extended attribute support for tmpfs:
* Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@lkcl.net>
* Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
*
* tiny-shmem:
* Copyright (c) 2004, 2008 Matt Mackall <mpm@selenic.com>
*
* This file is released under the GPL.
*/

#include <linux/fs.h>
#include <linux/init.h>
#include <linux/vfs.h>
#include <linux/mount.h>
#include <linux/pagemap.h>
#include <linux/file.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/percpu_counter.h>
#include <linux/swap.h>

static struct vfsmount *shm_mnt;

#ifdef CONFIG_SHMEM
/*
* This virtual memory filesystem is heavily based on the ramfs. It
* extends ramfs by the ability to use swap and honor resource limits
* which makes it a completely usable filesystem.
*/

#include <linux/xattr.h>
#include <linux/exportfs.h>
#include <linux/posix_acl.h>
#include <linux/generic_acl.h>
#include <linux/mman.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/backing-dev.h>
#include <linux/shmem_fs.h>
#include <linux/writeback.h>
#include <linux/blkdev.h>
#include <linux/security.h>
#include <linux/swapops.h>
#include <linux/mempolicy.h>
#include <linux/namei.h>
#include <linux/ctype.h>
#include <linux/migrate.h>
#include <linux/highmem.h>
#include <linux/seq_file.h>
#include <linux/magic.h>

#include <asm/uaccess.h>
#include <asm/div64.h>
#include <asm/pgtable.h>

/*
* The maximum size of a shmem/tmpfs file is limited by the maximum size of
* its triple-indirect swap vector - see illustration at shmem_swp_entry().
*
* With 4kB page size, maximum file size is just over 2TB on a 32-bit kernel,
* but one eighth of that on a 64-bit kernel. With 8kB page size, maximum
* file size is just over 4TB on a 64-bit kernel, but 16TB on a 32-bit kernel,
* MAX_LFS_FILESIZE being then more restrictive than swap vector layout.
*
* We use / and * instead of shifts in the definitions below, so that the swap
* vector can be tested with small even values (e.g. 20) for ENTRIES_PER_PAGE.
*/
#define ENTRIES_PER_PAGE (PAGE_CACHE_SIZE/sizeof(unsigned long))
#define ENTRIES_PER_PAGEPAGE ((unsigned long long)ENTRIES_PER_PAGE*ENTRIES_PER_PAGE)

#define SHMSWP_MAX_INDEX (SHMEM_NR_DIRECT + (ENTRIES_PER_PAGEPAGE/2) * (ENTRIES_PER_PAGE+1))
#define SHMSWP_MAX_BYTES (SHMSWP_MAX_INDEX << PAGE_CACHE_SHIFT)

#define SHMEM_MAX_BYTES min_t(unsigned long long, SHMSWP_MAX_BYTES, MAX_LFS_FILESIZE)
#define SHMEM_MAX_INDEX ((unsigned long)((SHMEM_MAX_BYTES+1) >> PAGE_CACHE_SHIFT))

#define BLOCKS_PER_PAGE (PAGE_CACHE_SIZE/512)
#define VM_ACCT(size) (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)

/* info->flags needs VM_flags to handle pagein/truncate races efficiently */
#define SHMEM_PAGEIN VM_READ
#define SHMEM_TRUNCATE VM_WRITE

/* Definition to limit shmem_truncate's steps between cond_rescheds */
#define LATENCY_LIMIT 64

/* Pretend that each entry is of this size in directory's i_size */
#define BOGO_DIRENT_SIZE 20

/* Flag allocation requirements to shmem_getpage and shmem_swp_alloc */
enum sgp_type {
SGP_READ, /* don't exceed i_size, don't allocate page */
SGP_CACHE, /* don't exceed i_size, may allocate page */
SGP_DIRTY, /* like SGP_CACHE, but set new page dirty */
SGP_WRITE, /* may exceed i_size, may allocate page */
};

#ifdef CONFIG_TMPFS
static unsigned long shmem_default_max_blocks(void)
{
return totalram_pages / 2;
}

static unsigned long shmem_default_max_inodes(void)
{
return min(totalram_pages - totalhigh_pages, totalram_pages / 2);
}
#endif

static int shmem_getpage(struct inode *inode, unsigned long idx,
struct page **pagep, enum sgp_type sgp, int *type);

static inline struct page *shmem_dir_alloc(gfp_t gfp_mask)
{
/*
* The above definition of ENTRIES_PER_PAGE, and the use of
* BLOCKS_PER_PAGE on indirect pages, assume PAGE_CACHE_SIZE:
* might be reconsidered if it ever diverges from PAGE_SIZE.
*
* Mobility flags are masked out as swap vectors cannot move
*/
return alloc_pages((gfp_mask & ~GFP_MOVABLE_MASK) | __GFP_ZERO,
PAGE_CACHE_SHIFT-PAGE_SHIFT);
}

static inline void shmem_dir_free(struct page *page)
{
__free_pages(page, PAGE_CACHE_SHIFT-PAGE_SHIFT);
}

static struct page **shmem_dir_map(struct page *page)
{
return (struct page **)kmap_atomic(page, KM_USER0);
}

static inline void shmem_dir_unmap(struct page **dir)
{
kunmap_atomic(dir, KM_USER0);
}

static swp_entry_t *shmem_swp_map(struct page *page)
{
return (swp_entry_t *)kmap_atomic(page, KM_USER1);
}

static inline void shmem_swp_balance_unmap(void)
{
/*
* When passing a pointer to an i_direct entry, to code which
* also handles indirect entries and so will shmem_swp_unmap,
* we must arrange for the preempt count to remain in balance.
* What kmap_atomic of a lowmem page does depends on config
* and architecture, so pretend to kmap_atomic some lowmem page.
*/
(void) kmap_atomic(ZERO_PAGE(0), KM_USER1);
}

static inline void shmem_swp_unmap(swp_entry_t *entry)
{
kunmap_atomic(entry, KM_USER1);
}

static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
{
return sb->s_fs_info;
}

/*
* shmem_file_setup pre-accounts the whole fixed size of a VM object,
* for shared memory and for shared anonymous (/dev/zero) mappings
* (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
* consistent with the pre-accounting of private mappings ...
*/
static inline int shmem_acct_size(unsigned long flags, loff_t size)
{
return (flags & VM_NORESERVE) ?
0 : security_vm_enough_memory_kern(VM_ACCT(size));
}

static inline void shmem_unacct_size(unsigned long flags, loff_t size)
{
if (!(flags & VM_NORESERVE))
vm_unacct_memory(VM_ACCT(size));
}

/*
* ... whereas tmpfs objects are accounted incrementally as
* pages are allocated, in order to allow huge sparse files.
* shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
* so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
*/
static inline int shmem_acct_block(unsigned long flags)
{
return (flags & VM_NORESERVE) ?
security_vm_enough_memory_kern(VM_ACCT(PAGE_CACHE_SIZE)) : 0;
}

static inline void shmem_unacct_blocks(unsigned long flags, long pages)
{
if (flags & VM_NORESERVE)
vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
}

static const struct super_operations shmem_ops;
static const struct address_space_operations shmem_aops;
static const struct file_operations shmem_file_operations;
static const struct inode_operations shmem_inode_operations;
static const struct inode_operations shmem_dir_inode_operations;
static const struct inode_operations shmem_special_inode_operations;
static const struct vm_operations_struct shmem_vm_ops;

static struct backing_dev_info shmem_backing_dev_info __read_mostly = {
.ra_pages = 0, /* No readahead */
.capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
};

static LIST_HEAD(shmem_swaplist);
static DEFINE_MUTEX(shmem_swaplist_mutex);

static void shmem_free_blocks(struct inode *inode, long pages)
{
struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
if (sbinfo->max_blocks) {
percpu_counter_add(&sbinfo->used_blocks, -pages);
spin_lock(&inode->i_lock);
inode->i_blocks -= pages*BLOCKS_PER_PAGE;
spin_unlock(&inode->i_lock);
}
}

static int shmem_reserve_inode(struct super_block *sb)
{
struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
if (sbinfo->max_inodes) {
spin_lock(&sbinfo->stat_lock);
if (!sbinfo->free_inodes) {
spin_unlock(&sbinfo->stat_lock);
return -ENOSPC;
}
sbinfo->free_inodes--;
spin_unlock(&sbinfo->stat_lock);
}
return 0;
}

static void shmem_free_inode(struct super_block *sb)
{
struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
if (sbinfo->max_inodes) {
spin_lock(&sbinfo->stat_lock);
sbinfo->free_inodes++;
spin_unlock(&sbinfo->stat_lock);
}
}

/**
* shmem_recalc_inode - recalculate the size of an inode
* @inode: inode to recalc
*
* We have to calculate the free blocks since the mm can drop
* undirtied hole pages behind our back.
*
* But normally info->alloced == inode->i_mapping->nrpages + info->swapped
* So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
*
* It has to be called with the spinlock held.
*/
static void shmem_recalc_inode(struct inode *inode)
{
struct shmem_inode_info *info = SHMEM_I(inode);
long freed;

freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
if (freed > 0) {
info->alloced -= freed;
shmem_unacct_blocks(info->flags, freed);
shmem_free_blocks(inode, freed);
}
}

/**
* shmem_swp_entry - find the swap vector position in the info structure
* @info: info structure for the inode
* @index: index of the page to find
* @page: optional page to add to the structure. Has to be preset to
* all zeros
*
* If there is no space allocated yet it will return NULL when
* page is NULL, else it will use the page for the needed block,
* setting it to NULL on return to indicate that it has been used.
*
* The swap vector is organized the following way:
*
* There are SHMEM_NR_DIRECT entries directly stored in the
* shmem_inode_info structure. So small files do not need an addional
* allocation.
*
* For pages with index > SHMEM_NR_DIRECT there is the pointer
* i_indirect which points to a page which holds in the first half
* doubly indirect blocks, in the second half triple indirect blocks:
*
* For an artificial ENTRIES_PER_PAGE = 4 this would lead to the
* following layout (for SHMEM_NR_DIRECT == 16):
*
* i_indirect -> dir --> 16-19
* | +-> 20-23
* |
* +-->dir2 --> 24-27
* | +-> 28-31
* | +-> 32-35
* | +-> 36-39
* |
* +-->dir3 --> 40-43
* +-> 44-47
* +-> 48-51
* +-> 52-55
*/
static swp_entry_t *shmem_swp_entry(struct shmem_inode_info *info, unsigned long index, struct page **page)
{
unsigned long offset;
struct page **dir;
struct page *subdir;

if (index < SHMEM_NR_DIRECT) {
shmem_swp_balance_unmap();
return info->i_direct+index;
}
if (!info->i_indirect) {
if (page) {
info->i_indirect = *page;
*page = NULL;
}
return NULL; /* need another page */
}

index -= SHMEM_NR_DIRECT;
offset = index % ENTRIES_PER_PAGE;
index /= ENTRIES_PER_PAGE;
dir = shmem_dir_map(info->i_indirect);

if (index >= ENTRIES_PER_PAGE/2) {
index -= ENTRIES_PER_PAGE/2;
dir += ENTRIES_PER_PAGE/2 + index/ENTRIES_PER_PAGE;
index %= ENTRIES_PER_PAGE;
subdir = *dir;
if (!subdir) {
if (page) {
*dir = *page;
*page = NULL;
}
shmem_dir_unmap(dir);
return NULL; /* need another page */
}
shmem_dir_unmap(dir);
dir = shmem_dir_map(subdir);
}

dir += index;
subdir = *dir;
if (!subdir) {
if (!page || !(subdir = *page)) {
shmem_dir_unmap(dir);
return NULL; /* need a page */
}
*dir = subdir;
*page = NULL;
}
shmem_dir_unmap(dir);
return shmem_swp_map(subdir) + offset;
}

static void shmem_swp_set(struct shmem_inode_info *info, swp_entry_t *entry, unsigned long value)
{
long incdec = value? 1: -1;

entry->val = value;
info->swapped += incdec;
if ((unsigned long)(entry - info->i_direct) >= SHMEM_NR_DIRECT) {
struct page *page = kmap_atomic_to_page(entry);
set_page_private(page, page_private(page) + incdec);
}
}

/**
* shmem_swp_alloc - get the position of the swap entry for the page.
* @info: info structure for the inode
* @index: index of the page to find
* @sgp: check and recheck i_size? skip allocation?
*
* If the entry does not exist, allocate it.
*/
static swp_entry_t *shmem_swp_alloc(struct shmem_inode_info *info, unsigned long index, enum sgp_type sgp)
{
struct inode *inode = &info->vfs_inode;
struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
struct page *page = NULL;
swp_entry_t *entry;

if (sgp != SGP_WRITE &&
((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode))
return ERR_PTR(-EINVAL);

while (!(entry = shmem_swp_entry(info, index, &page))) {
if (sgp == SGP_READ)
return shmem_swp_map(ZERO_PAGE(0));
/*
* Test used_blocks against 1 less max_blocks, since we have 1 data
* page (and perhaps indirect index pages) yet to allocate:
* a waste to allocate index if we cannot allocate data.
*/
if (sbinfo->max_blocks) {
if (percpu_counter_compare(&sbinfo->used_blocks,
sbinfo->max_blocks - 1) >= 0)
return ERR_PTR(-ENOSPC);
percpu_counter_inc(&sbinfo->used_blocks);
spin_lock(&inode->i_lock);
inode->i_blocks += BLOCKS_PER_PAGE;
spin_unlock(&inode->i_lock);
}

spin_unlock(&info->lock);
page = shmem_dir_alloc(mapping_gfp_mask(inode->i_mapping));
spin_lock(&info->lock);

if (!page) {
shmem_free_blocks(inode, 1);
return ERR_PTR(-ENOMEM);
}
if (sgp != SGP_WRITE &&
((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
entry = ERR_PTR(-EINVAL);
break;
}
if (info->next_index <= index)
info->next_index = index + 1;
}
if (page) {
/* another task gave its page, or truncated the file */
shmem_free_blocks(inode, 1);
shmem_dir_free(page);
}
if (info->next_index <= index && !IS_ERR(entry))
info->next_index = index + 1;
return entry;
}

/**
* shmem_free_swp - free some swap entries in a directory
* @dir: pointer to the directory
* @edir: pointer after last entry of the directory
* @punch_lock: pointer to spinlock when needed for the holepunch case
*/
static int shmem_free_swp(swp_entry_t *dir, swp_entry_t *edir,
spinlock_t *punch_lock)
{
spinlock_t *punch_unlock = NULL;
swp_entry_t *ptr;
int freed = 0;

for (ptr = dir; ptr < edir; ptr++) {
if (ptr->val) {
if (unlikely(punch_lock)) {
punch_unlock = punch_lock;
punch_lock = NULL;
spin_lock(punch_unlock);
if (!ptr->val)
continue;
}
free_swap_and_cache(*ptr);
*ptr = (swp_entry_t){0};
freed++;
}
}
if (punch_unlock)
spin_unlock(punch_unlock);
return freed;
}

static int shmem_map_and_free_swp(struct page *subdir, int offset,
int limit, struct page ***dir, spinlock_t *punch_lock)
{
swp_entry_t *ptr;
int freed = 0;

ptr = shmem_swp_map(subdir);
for (; offset < limit; offset += LATENCY_LIMIT) {
int size = limit - offset;
if (size > LATENCY_LIMIT)
size = LATENCY_LIMIT;
freed += shmem_free_swp(ptr+offset, ptr+offset+size,
punch_lock);
if (need_resched()) {
shmem_swp_unmap(ptr);
if (*dir) {
shmem_dir_unmap(*dir);
*dir = NULL;
}
cond_resched();
ptr = shmem_swp_map(subdir);
}
}
shmem_swp_unmap(ptr);
return freed;
}

static void shmem_free_pages(struct list_head *next)
{
struct page *page;
int freed = 0;

do {
page = container_of(next, struct page, lru);
next = next->next;
shmem_dir_free(page);
freed++;
if (freed >= LATENCY_LIMIT) {
cond_resched();
freed = 0;
}
} while (next);
}

static void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end)
{
struct shmem_inode_info *info = SHMEM_I(inode);
unsigned long idx;
unsigned long size;
unsigned long limit;
unsigned long stage;
unsigned long diroff;
struct page **dir;
struct page *topdir;
struct page *middir;
struct page *subdir;
swp_entry_t *ptr;
LIST_HEAD(pages_to_free);
long nr_pages_to_free = 0;
long nr_swaps_freed = 0;
int offset;
int freed;
int punch_hole;
spinlock_t *needs_lock;
spinlock_t *punch_lock;
unsigned long upper_limit;

inode->i_ctime = inode->i_mtime = CURRENT_TIME;
idx = (start + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
if (idx >= info->next_index)
return;

spin_lock(&info->lock);
info->flags |= SHMEM_TRUNCATE;
if (likely(end == (loff_t) -1)) {
limit = info->next_index;
upper_limit = SHMEM_MAX_INDEX;
info->next_index = idx;
needs_lock = NULL;
punch_hole = 0;
} else {
if (end + 1 >= inode->i_size) { /* we may free a little more */
limit = (inode->i_size + PAGE_CACHE_SIZE - 1) >>
PAGE_CACHE_SHIFT;
upper_limit = SHMEM_MAX_INDEX;
} else {
limit = (end + 1) >> PAGE_CACHE_SHIFT;
upper_limit = limit;
}
needs_lock = &info->lock;
punch_hole = 1;
}

topdir = info->i_indirect;
if (topdir && idx <= SHMEM_NR_DIRECT && !punch_hole) {
info->i_indirect = NULL;
nr_pages_to_free++;
list_add(&topdir->lru, &pages_to_free);
}
spin_unlock(&info->lock);

if (info->swapped && idx < SHMEM_NR_DIRECT) {
ptr = info->i_direct;
size = limit;
if (size > SHMEM_NR_DIRECT)
size = SHMEM_NR_DIRECT;
nr_swaps_freed = shmem_free_swp(ptr+idx, ptr+size, needs_lock);
}

/*
* If there are no indirect blocks or we are punching a hole
* below indirect blocks, nothing to be done.
*/
if (!topdir || limit <= SHMEM_NR_DIRECT)
goto done2;

/*
* The truncation case has already dropped info->lock, and we're safe
* because i_size and next_index have already been lowered, preventing
* access beyond. But in the punch_hole case, we still need to take
* the lock when updating the swap directory, because there might be
* racing accesses by shmem_getpage(SGP_CACHE), shmem_unuse_inode or
* shmem_writepage. However, whenever we find we can remove a whole
* directory page (not at the misaligned start or end of the range),
* we first NULLify its pointer in the level above, and then have no
* need to take the lock when updating its contents: needs_lock and
* punch_lock (either pointing to info->lock or NULL) manage this.
*/

upper_limit -= SHMEM_NR_DIRECT;
limit -= SHMEM_NR_DIRECT;
idx = (idx > SHMEM_NR_DIRECT)? (idx - SHMEM_NR_DIRECT): 0;
offset = idx % ENTRIES_PER_PAGE;
idx -= offset;

dir = shmem_dir_map(topdir);
stage = ENTRIES_PER_PAGEPAGE/2;
if (idx < ENTRIES_PER_PAGEPAGE/2) {
middir = topdir;
diroff = idx/ENTRIES_PER_PAGE;
} else {
dir += ENTRIES_PER_PAGE/2;
dir += (idx - ENTRIES_PER_PAGEPAGE/2)/ENTRIES_PER_PAGEPAGE;
while (stage <= idx)
stage += ENTRIES_PER_PAGEPAGE;
middir = *dir;
if (*dir) {
diroff = ((idx - ENTRIES_PER_PAGEPAGE/2) %
ENTRIES_PER_PAGEPAGE) / ENTRIES_PER_PAGE;
if (!diroff && !offset && upper_limit >= stage) {
if (needs_lock) {
spin_lock(needs_lock);
*dir = NULL;
spin_unlock(needs_lock);
needs_lock = NULL;
} else
*dir = NULL;
nr_pages_to_free++;
list_add(&middir->lru, &pages_to_free);
}
shmem_dir_unmap(dir);
dir = shmem_dir_map(middir);
} else {
diroff = 0;
offset = 0;
idx = stage;
}
}

for (; idx < limit; idx += ENTRIES_PER_PAGE, diroff++) {
if (unlikely(idx == stage)) {
shmem_dir_unmap(dir);
dir = shmem_dir_map(topdir) +
ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
while (!*dir) {
dir++;
idx += ENTRIES_PER_PAGEPAGE;
if (idx >= limit)
goto done1;
}
stage = idx + ENTRIES_PER_PAGEPAGE;
middir = *dir;
if (punch_hole)
needs_lock = &info->lock;
if (upper_limit >= stage) {
if (needs_lock) {
spin_lock(needs_lock);
*dir = NULL;
spin_unlock(needs_lock);
needs_lock = NULL;
} else
*dir = NULL;
nr_pages_to_free++;
list_add(&middir->lru, &pages_to_free);
}
shmem_dir_unmap(dir);
cond_resched();
dir = shmem_dir_map(middir);
diroff = 0;
}
punch_lock = needs_lock;
subdir = dir[diroff];
if (subdir && !offset && upper_limit-idx >= ENTRIES_PER_PAGE) {
if (needs_lock) {
spin_lock(needs_lock);
dir[diroff] = NULL;
spin_unlock(needs_lock);
punch_lock = NULL;
} else
dir[diroff] = NULL;
nr_pages_to_free++;
list_add(&subdir->lru, &pages_to_free);
}
if (subdir && page_private(subdir) /* has swap entries */) {
size = limit - idx;
if (size > ENTRIES_PER_PAGE)
size = ENTRIES_PER_PAGE;
freed = shmem_map_and_free_swp(subdir,
offset, size, &dir, punch_lock);
if (!dir)
dir = shmem_dir_map(middir);
nr_swaps_freed += freed;
if (offset || punch_lock) {
spin_lock(&info->lock);
set_page_private(subdir,
page_private(subdir) - freed);
spin_unlock(&info->lock);
} else
BUG_ON(page_private(subdir) != freed);
}
offset = 0;
}
done1:
shmem_dir_unmap(dir);
done2:
if (inode->i_mapping->nrpages && (info->flags & SHMEM_PAGEIN)) {
/*
* Call truncate_inode_pages again: racing shmem_unuse_inode
* may have swizzled a page in from swap since
* truncate_pagecache or generic_delete_inode did it, before we
* lowered next_index. Also, though shmem_getpage checks
* i_size before adding to cache, no recheck after: so fix the
* narrow window there too.
*
* Recalling truncate_inode_pages_range and unmap_mapping_range
* every time for punch_hole (which never got a chance to clear
* SHMEM_PAGEIN at the start of vmtruncate_range) is expensive,
* yet hardly ever necessary: try to optimize them out later.
*/
truncate_inode_pages_range(inode->i_mapping, start, end);
if (punch_hole)
unmap_mapping_range(inode->i_mapping, start,
end - start, 1);
}

spin_lock(&info->lock);
info->flags &= ~SHMEM_TRUNCATE;
info->swapped -= nr_swaps_freed;
if (nr_pages_to_free)
shmem_free_blocks(inode, nr_pages_to_free);
shmem_recalc_inode(inode);
spin_unlock(&info->lock);

/*
* Empty swap vector directory pages to be freed?
*/
if (!list_empty(&pages_to_free)) {
pages_to_free.prev->next = NULL;
shmem_free_pages(pages_to_free.next);
}
}

static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
{
struct inode *inode = dentry->d_inode;
loff_t newsize = attr->ia_size;
int error;

error = inode_change_ok(inode, attr);
if (error)
return error;

if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)
&& newsize != inode->i_size) {
struct page *page = NULL;

if (newsize < inode->i_size) {
/*
* If truncating down to a partial page, then
* if that page is already allocated, hold it
* in memory until the truncation is over, so
* truncate_partial_page cannot miss it were
* it assigned to swap.
*/
if (newsize & (PAGE_CACHE_SIZE-1)) {
(void) shmem_getpage(inode,
newsize >> PAGE_CACHE_SHIFT,
&page, SGP_READ, NULL);
if (page)
unlock_page(page);
}
/*
* Reset SHMEM_PAGEIN flag so that shmem_truncate can
* detect if any pages might have been added to cache
* after truncate_inode_pages. But we needn't bother
* if it's being fully truncated to zero-length: the
* nrpages check is efficient enough in that case.
*/
if (newsize) {
struct shmem_inode_info *info = SHMEM_I(inode);
spin_lock(&info->lock);
info->flags &= ~SHMEM_PAGEIN;
spin_unlock(&info->lock);
}
}

/* XXX(truncate): truncate_setsize should be called last */
truncate_setsize(inode, newsize);
if (page)
page_cache_release(page);
shmem_truncate_range(inode, newsize, (loff_t)-1);
}

setattr_copy(inode, attr);
#ifdef CONFIG_TMPFS_POSIX_ACL
if (attr->ia_valid & ATTR_MODE)
error = generic_acl_chmod(inode);
#endif
return error;
}

static void shmem_evict_inode(struct inode *inode)
{
struct shmem_inode_info *info = SHMEM_I(inode);

if (inode->i_mapping->a_ops == &shmem_aops) {
truncate_inode_pages(inode->i_mapping, 0);
shmem_unacct_size(info->flags, inode->i_size);
inode->i_size = 0;
shmem_truncate_range(inode, 0, (loff_t)-1);
if (!list_empty(&info->swaplist)) {
mutex_lock(&shmem_swaplist_mutex);
list_del_init(&info->swaplist);
mutex_unlock(&shmem_swaplist_mutex);
}
}
BUG_ON(inode->i_blocks);
shmem_free_inode(inode->i_sb);
end_writeback(inode);
}

static inline int shmem_find_swp(swp_entry_t entry, swp_entry_t *dir, swp_entry_t *edir)
{
swp_entry_t *ptr;

for (ptr = dir; ptr < edir; ptr++) {
if (ptr->val == entry.val)
return ptr - dir;
}
return -1;
}

static int shmem_unuse_inode(struct shmem_inode_info *info, swp_entry_t entry, struct page *page)
{
struct address_space *mapping;
unsigned long idx;
unsigned long size;
unsigned long limit;
unsigned long stage;
struct page **dir;
struct page *subdir;
swp_entry_t *ptr;
int offset;
int error;

idx = 0;
ptr = info->i_direct;
spin_lock(&info->lock);
if (!info->swapped) {
list_del_init(&info->swaplist);
goto lost2;
}
limit = info->next_index;
size = limit;
if (size > SHMEM_NR_DIRECT)
size = SHMEM_NR_DIRECT;
offset = shmem_find_swp(entry, ptr, ptr+size);
if (offset >= 0) {
shmem_swp_balance_unmap();
goto found;
}
if (!info->i_indirect)
goto lost2;

dir = shmem_dir_map(info->i_indirect);
stage = SHMEM_NR_DIRECT + ENTRIES_PER_PAGEPAGE/2;

for (idx = SHMEM_NR_DIRECT; idx < limit; idx += ENTRIES_PER_PAGE, dir++) {
if (unlikely(idx == stage)) {
shmem_dir_unmap(dir-1);
if (cond_resched_lock(&info->lock)) {
/* check it has not been truncated */
if (limit > info->next_index) {
limit = info->next_index;
if (idx >= limit)
goto lost2;
}
}
dir = shmem_dir_map(info->i_indirect) +
ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
while (!*dir) {
dir++;
idx += ENTRIES_PER_PAGEPAGE;
if (idx >= limit)
goto lost1;
}
stage = idx + ENTRIES_PER_PAGEPAGE;
subdir = *dir;
shmem_dir_unmap(dir);
dir = shmem_dir_map(subdir);
}
subdir = *dir;
if (subdir && page_private(subdir)) {
ptr = shmem_swp_map(subdir);
size = limit - idx;
if (size > ENTRIES_PER_PAGE)
size = ENTRIES_PER_PAGE;
offset = shmem_find_swp(entry, ptr, ptr+size);
shmem_swp_unmap(ptr);
if (offset >= 0) {
shmem_dir_unmap(dir);
ptr = shmem_swp_map(subdir);
goto found;
}
}
}
lost1:
shmem_dir_unmap(dir-1);
lost2:
spin_unlock(&info->lock);
return 0;
found:
idx += offset;
ptr += offset;

/*
* Move _head_ to start search for next from here.
* But be careful: shmem_evict_inode checks list_empty without taking
* mutex, and there's an instant in list_move_tail when info->swaplist
* would appear empty, if it were the only one on shmem_swaplist. We
* could avoid doing it if inode NULL; or use this minor optimization.
*/
if (shmem_swaplist.next != &info->swaplist)
list_move_tail(&shmem_swaplist, &info->swaplist);

/*
* We rely on shmem_swaplist_mutex, not only to protect the swaplist,
* but also to hold up shmem_evict_inode(): so inode cannot be freed
* beneath us (pagelock doesn't help until the page is in pagecache).
*/
mapping = info->vfs_inode.i_mapping;
error = add_to_page_cache_locked(page, mapping, idx, GFP_NOWAIT);
/* which does mem_cgroup_uncharge_cache_page on error */

if (error == -EEXIST) {
struct page *filepage = find_get_page(mapping, idx);
error = 1;
if (filepage) {
/*
* There might be a more uptodate page coming down
* from a stacked writepage: forget our swappage if so.
*/
if (PageUptodate(filepage))
error = 0;
page_cache_release(filepage);
}
}
if (!error) {
delete_from_swap_cache(page);
set_page_dirty(page);
info->flags |= SHMEM_PAGEIN;
shmem_swp_set(info, ptr, 0);
swap_free(entry);
error = 1; /* not an error, but entry was found */
}
shmem_swp_unmap(ptr);
spin_unlock(&info->lock);
return error;
}

/*
* shmem_unuse() search for an eventually swapped out shmem page.
*/
int shmem_unuse(swp_entry_t entry, struct page *page)
{
struct list_head *p, *next;
struct shmem_inode_info *info;
int found = 0;
int error;

/*
* Charge page using GFP_KERNEL while we can wait, before taking
* the shmem_swaplist_mutex which might hold up shmem_writepage().
* Charged back to the user (not to caller) when swap account is used.
* add_to_page_cache() will be called with GFP_NOWAIT.
*/
error = mem_cgroup_cache_charge(page, current->mm, GFP_KERNEL);
if (error)
goto out;
/*
* Try to preload while we can wait, to not make a habit of
* draining atomic reserves; but don't latch on to this cpu,
* it's okay if sometimes we get rescheduled after this.
*/
error = radix_tree_preload(GFP_KERNEL);
if (error)
goto uncharge;
radix_tree_preload_end();

mutex_lock(&shmem_swaplist_mutex);
list_for_each_safe(p, next, &shmem_swaplist) {
info = list_entry(p, struct shmem_inode_info, swaplist);
found = shmem_unuse_inode(info, entry, page);
cond_resched();
if (found)
break;
}
mutex_unlock(&shmem_swaplist_mutex);

uncharge:
if (!found)
mem_cgroup_uncharge_cache_page(page);
if (found < 0)
error = found;
out:
unlock_page(page);
page_cache_release(page);
return error;
}

/*
* Move the page from the page cache to the swap cache.
*/
static int shmem_writepage(struct page *page, struct writeback_control *wbc)
{
struct shmem_inode_info *info;
swp_entry_t *entry, swap;
struct address_space *mapping;
unsigned long index;
struct inode *inode;

BUG_ON(!PageLocked(page));
mapping = page->mapping;
index = page->index;
inode = mapping->host;
info = SHMEM_I(inode);
if (info->flags & VM_LOCKED)
goto redirty;
if (!total_swap_pages)
goto redirty;

/*
* shmem_backing_dev_info's capabilities prevent regular writeback or
* sync from ever calling shmem_writepage; but a stacking filesystem
* may use the ->writepage of its underlying filesystem, in which case
* tmpfs should write out to swap only in response to memory pressure,
* and not for the writeback threads or sync. However, in those cases,
* we do still want to check if there's a redundant swappage to be
* discarded.
*/
if (wbc->for_reclaim)
swap = get_swap_page();
else
swap.val = 0;

/*
* Add inode to shmem_unuse()'s list of swapped-out inodes,
* if it's not already there. Do it now because we cannot take
* mutex while holding spinlock, and must do so before the page
* is moved to swap cache, when its pagelock no longer protects
* the inode from eviction. But don't unlock the mutex until
* we've taken the spinlock, because shmem_unuse_inode() will
* prune a !swapped inode from the swaplist under both locks.
*/
if (swap.val) {
mutex_lock(&shmem_swaplist_mutex);
if (list_empty(&info->swaplist))
list_add_tail(&info->swaplist, &shmem_swaplist);
}

spin_lock(&info->lock);
if (swap.val)
mutex_unlock(&shmem_swaplist_mutex);

if (index >= info->next_index) {
BUG_ON(!(info->flags & SHMEM_TRUNCATE));
goto unlock;
}
entry = shmem_swp_entry(info, index, NULL);
if (entry->val) {
/*
* The more uptodate page coming down from a stacked
* writepage should replace our old swappage.
*/
free_swap_and_cache(*entry);
shmem_swp_set(info, entry, 0);
}
shmem_recalc_inode(inode);

if (swap.val && add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
delete_from_page_cache(page);
shmem_swp_set(info, entry, swap.val);
shmem_swp_unmap(entry);
swap_shmem_alloc(swap);
spin_unlock(&info->lock);
BUG_ON(page_mapped(page));
swap_writepage(page, wbc);
return 0;
}

shmem_swp_unmap(entry);
unlock:
spin_unlock(&info->lock);
/*
* add_to_swap_cache() doesn't return -EEXIST, so we can safely
* clear SWAP_HAS_CACHE flag.
*/
swapcache_free(swap, NULL);
redirty:
set_page_dirty(page);
if (wbc->for_reclaim)
return AOP_WRITEPAGE_ACTIVATE; /* Return with page locked */
unlock_page(page);
return 0;
}

#ifdef CONFIG_NUMA
#ifdef CONFIG_TMPFS
static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
{
char buffer[64];

if (!mpol || mpol->mode == MPOL_DEFAULT)
return; /* show nothing */

mpol_to_str(buffer, sizeof(buffer), mpol, 1);

seq_printf(seq, ",mpol=%s", buffer);
}

static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
{
struct mempolicy *mpol = NULL;
if (sbinfo->mpol) {
spin_lock(&sbinfo->stat_lock); /* prevent replace/use races */
mpol = sbinfo->mpol;
mpol_get(mpol);
spin_unlock(&sbinfo->stat_lock);
}
return mpol;
}
#endif /* CONFIG_TMPFS */

static struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
struct shmem_inode_info *info, unsigned long idx)
{
struct mempolicy mpol, *spol;
struct vm_area_struct pvma;
struct page *page;

spol = mpol_cond_copy(&mpol,
mpol_shared_policy_lookup(&info->policy, idx));

/* Create a pseudo vma that just contains the policy */
pvma.vm_start = 0;
pvma.vm_pgoff = idx;
pvma.vm_ops = NULL;
pvma.vm_policy = spol;
page = swapin_readahead(entry, gfp, &pvma, 0);
return page;
}

static struct page *shmem_alloc_page(gfp_t gfp,
struct shmem_inode_info *info, unsigned long idx)
{
struct vm_area_struct pvma;

/* Create a pseudo vma that just contains the policy */
pvma.vm_start = 0;
pvma.vm_pgoff = idx;
pvma.vm_ops = NULL;
pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx);

/*
* alloc_page_vma() will drop the shared policy reference
*/
return alloc_page_vma(gfp, &pvma, 0);
}
#else /* !CONFIG_NUMA */
#ifdef CONFIG_TMPFS
static inline void shmem_show_mpol(struct seq_file *seq, struct mempolicy *p)
{
}
#endif /* CONFIG_TMPFS */

static inline struct page *shmem_swapin(swp_entry_t entry, gfp_t gfp,
struct shmem_inode_info *info, unsigned long idx)
{
return swapin_readahead(entry, gfp, NULL, 0);
}

static inline struct page *shmem_alloc_page(gfp_t gfp,
struct shmem_inode_info *info, unsigned long idx)
{
return alloc_page(gfp);
}
#endif /* CONFIG_NUMA */

#if !defined(CONFIG_NUMA) || !defined(CONFIG_TMPFS)
static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
{
return NULL;
}
#endif

/*
* shmem_getpage - either get the page from swap or allocate a new one
*
* If we allocate a new one we do not mark it dirty. That's up to the
* vm. If we swap it in we mark it dirty since we also free the swap
* entry since a page cannot live in both the swap and page cache
*/
static int shmem_getpage(struct inode *inode, unsigned long idx,
struct page **pagep, enum sgp_type sgp, int *type)
{
struct address_space *mapping = inode->i_mapping;
struct shmem_inode_info *info = SHMEM_I(inode);
struct shmem_sb_info *sbinfo;
struct page *filepage = *pagep;
struct page *swappage;
struct page *prealloc_page = NULL;
swp_entry_t *entry;
swp_entry_t swap;
gfp_t gfp;
int error;

if (idx >= SHMEM_MAX_INDEX)
return -EFBIG;

if (type)
*type = 0;

/*
* Normally, filepage is NULL on entry, and either found
* uptodate immediately, or allocated and zeroed, or read
* in under swappage, which is then assigned to filepage.
* But shmem_readpage (required for splice) passes in a locked
* filepage, which may be found not uptodate by other callers
* too, and may need to be copied from the swappage read in.
*/
repeat:
if (!filepage)
filepage = find_lock_page(mapping, idx);
if (filepage && PageUptodate(filepage))
goto done;
gfp = mapping_gfp_mask(mapping);
if (!filepage) {
/*
* Try to preload while we can wait, to not make a habit of
* draining atomic reserves; but don't latch on to this cpu.
*/
error = radix_tree_preload(gfp & ~__GFP_HIGHMEM);
if (error)
goto failed;
radix_tree_preload_end();
if (sgp != SGP_READ && !prealloc_page) {
/* We don't care if this fails */
prealloc_page = shmem_alloc_page(gfp, info, idx);
if (prealloc_page) {
if (mem_cgroup_cache_charge(prealloc_page,
current->mm, GFP_KERNEL)) {
page_cache_release(prealloc_page);
prealloc_page = NULL;
}
}
}
}
error = 0;

spin_lock(&info->lock);
shmem_recalc_inode(inode);
entry = shmem_swp_alloc(info, idx, sgp);
if (IS_ERR(entry)) {
spin_unlock(&info->lock);
error = PTR_ERR(entry);
goto failed;
}
swap = *entry;

if (swap.val) {
/* Look it up and read it in.. */
swappage = lookup_swap_cache(swap);
if (!swappage) {
shmem_swp_unmap(entry);
/* here we actually do the io */
if (type && !(*type & VM_FAULT_MAJOR)) {
__count_vm_event(PGMAJFAULT);
*type |= VM_FAULT_MAJOR;
}
spin_unlock(&info->lock);
swappage = shmem_swapin(swap, gfp, info, idx);
if (!swappage) {
spin_lock(&info->lock);
entry = shmem_swp_alloc(info, idx, sgp);
if (IS_ERR(entry))
error = PTR_ERR(entry);
else {
if (entry->val == swap.val)
error = -ENOMEM;
shmem_swp_unmap(entry);
}
spin_unlock(&info->lock);
if (error)
goto failed;
goto repeat;
}
wait_on_page_locked(swappage);
page_cache_release(swappage);
goto repeat;
}

/* We have to do this with page locked to prevent races */
if (!trylock_page(swappage)) {
shmem_swp_unmap(entry);
spin_unlock(&info->lock);
wait_on_page_locked(swappage);
page_cache_release(swappage);
goto repeat;
}
if (PageWriteback(swappage)) {
shmem_swp_unmap(entry);
spin_unlock(&info->lock);
wait_on_page_writeback(swappage);
unlock_page(swappage);
page_cache_release(swappage);
goto repeat;
}
if (!PageUptodate(swappage)) {
shmem_swp_unmap(entry);
spin_unlock(&info->lock);
unlock_page(swappage);
page_cache_release(swappage);
error = -EIO;
goto failed;
}

if (filepage) {
shmem_swp_set(info, entry, 0);
shmem_swp_unmap(entry);
delete_from_swap_cache(swappage);
spin_unlock(&info->lock);
copy_highpage(filepage, swappage);
unlock_page(swappage);
page_cache_release(swappage);
flush_dcache_page(filepage);
SetPageUptodate(filepage);
set_page_dirty(filepage);
swap_free(swap);
} else if (!(error = add_to_page_cache_locked(swappage, mapping,
idx, GFP_NOWAIT))) {
info->flags |= SHMEM_PAGEIN;
shmem_swp_set(info, entry, 0);
shmem_swp_unmap(entry);
delete_from_swap_cache(swappage);
spin_unlock(&info->lock);
filepage = swappage;
set_page_dirty(filepage);
swap_free(swap);
} else {
shmem_swp_unmap(entry);
spin_unlock(&info->lock);
if (error == -ENOMEM) {
/*
* reclaim from proper memory cgroup and
* call memcg's OOM if needed.
*/
error = mem_cgroup_shmem_charge_fallback(
swappage,
current->mm,
gfp);
if (error) {
unlock_page(swappage);
page_cache_release(swappage);
goto failed;
}
}
unlock_page(swappage);
page_cache_release(swappage);
goto repeat;
}
} else if (sgp == SGP_READ && !filepage) {
shmem_swp_unmap(entry);
filepage = find_get_page(mapping, idx);
if (filepage &&
(!PageUptodate(filepage) || !trylock_page(filepage))) {
spin_unlock(&info->lock);
wait_on_page_locked(filepage);
page_cache_release(filepage);
filepage = NULL;
goto repeat;
}
spin_unlock(&info->lock);
} else {
shmem_swp_unmap(entry);
sbinfo = SHMEM_SB(inode->i_sb);
if (sbinfo->max_blocks) {
if (percpu_counter_compare(&sbinfo->used_blocks,
sbinfo->max_blocks) >= 0 ||
shmem_acct_block(info->flags))
goto nospace;
percpu_counter_inc(&sbinfo->used_blocks);
spin_lock(&inode->i_lock);
inode->i_blocks += BLOCKS_PER_PAGE;
spin_unlock(&inode->i_lock);
} else if (shmem_acct_block(info->flags))
goto nospace;

if (!filepage) {
int ret;

if (!prealloc_page) {
spin_unlock(&info->lock);
filepage = shmem_alloc_page(gfp, info, idx);
if (!filepage) {
shmem_unacct_blocks(info->flags, 1);
shmem_free_blocks(inode, 1);
error = -ENOMEM;
goto failed;
}
SetPageSwapBacked(filepage);

/*
* Precharge page while we can wait, compensate
* after
*/
error = mem_cgroup_cache_charge(filepage,
current->mm, GFP_KERNEL);
if (error) {
page_cache_release(filepage);
shmem_unacct_blocks(info->flags, 1);
shmem_free_blocks(inode, 1);
filepage = NULL;
goto failed;
}

spin_lock(&info->lock);
} else {
filepage = prealloc_page;
prealloc_page = NULL;
SetPageSwapBacked(filepage);
}

entry = shmem_swp_alloc(info, idx, sgp);
if (IS_ERR(entry))
error = PTR_ERR(entry);
else {
swap = *entry;
shmem_swp_unmap(entry);
}
ret = error || swap.val;
if (ret)
mem_cgroup_uncharge_cache_page(filepage);
else
ret = add_to_page_cache_lru(filepage, mapping,
idx, GFP_NOWAIT);
/*
* At add_to_page_cache_lru() failure, uncharge will
* be done automatically.
*/
if (ret) {
spin_unlock(&info->lock);
page_cache_release(filepage);
shmem_unacct_blocks(info->flags, 1);
shmem_free_blocks(inode, 1);
filepage = NULL;
if (error)
goto failed;
goto repeat;
}
info->flags |= SHMEM_PAGEIN;
}

info->alloced++;
spin_unlock(&info->lock);
clear_highpage(filepage);
flush_dcache_page(filepage);
SetPageUptodate(filepage);
if (sgp == SGP_DIRTY)
set_page_dirty(filepage);
}
done:
*pagep = filepage;
error = 0;
goto out;

nospace:
/*
* Perhaps the page was brought in from swap between find_lock_page
* and taking info->lock? We allow for that at add_to_page_cache_lru,
* but must also avoid reporting a spurious ENOSPC while working on a
* full tmpfs. (When filepage has been passed in to shmem_getpage, it
* is already in page cache, which prevents this race from occurring.)
*/
if (!filepage) {
struct page *page = find_get_page(mapping, idx);
if (page) {
spin_unlock(&info->lock);
page_cache_release(page);
goto repeat;
}
}
spin_unlock(&info->lock);
error = -ENOSPC;
failed:
if (*pagep != filepage) {
unlock_page(filepage);
page_cache_release(filepage);
}
out:
if (prealloc_page) {
mem_cgroup_uncharge_cache_page(prealloc_page);
page_cache_release(prealloc_page);
}
return error;
}

static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
int error;
int ret;

if (((loff_t)vmf->pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
return VM_FAULT_SIGBUS;

error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_CACHE, &ret);
if (error)
return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);

return ret | VM_FAULT_LOCKED;
}

#ifdef CONFIG_NUMA
static int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *new)
{
struct inode *i = vma->vm_file->f_path.dentry->d_inode;
return mpol_set_shared_policy(&SHMEM_I(i)->policy, vma, new);
}

static struct mempolicy *shmem_get_policy(struct vm_area_struct *vma,
unsigned long addr)
{
struct inode *i = vma->vm_file->f_path.dentry->d_inode;
unsigned long idx;

idx = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
return mpol_shared_policy_lookup(&SHMEM_I(i)->policy, idx);
}
#endif

int shmem_lock(struct file *file, int lock, struct user_struct *user)
{
struct inode *inode = file->f_path.dentry->d_inode;
struct shmem_inode_info *info = SHMEM_I(inode);
int retval = -ENOMEM;

spin_lock(&info->lock);
if (lock && !(info->flags & VM_LOCKED)) {
if (!user_shm_lock(inode->i_size, user))
goto out_nomem;
info->flags |= VM_LOCKED;
mapping_set_unevictable(file->f_mapping);
}
if (!lock && (info->flags & VM_LOCKED) && user) {
user_shm_unlock(inode->i_size, user);
info->flags &= ~VM_LOCKED;
mapping_clear_unevictable(file->f_mapping);
scan_mapping_unevictable_pages(file->f_mapping);
}
retval = 0;

out_nomem:
spin_unlock(&info->lock);
return retval;
}

static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
{
file_accessed(file);
vma->vm_ops = &shmem_vm_ops;
vma->vm_flags |= VM_CAN_NONLINEAR;
return 0;
}

static struct inode *shmem_get_inode(struct super_block *sb, const struct inode *dir,
int mode, dev_t dev, unsigned long flags)
{
struct inode *inode;
struct shmem_inode_info *info;
struct shmem_sb_info *sbinfo = SHMEM_SB(sb);

if (shmem_reserve_inode(sb))
return NULL;

inode = new_inode(sb);
if (inode) {
inode->i_ino = get_next_ino();
inode_init_owner(inode, dir, mode);
inode->i_blocks = 0;
inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
inode->i_generation = get_seconds();
info = SHMEM_I(inode);
memset(info, 0, (char *)inode - (char *)info);
spin_lock_init(&info->lock);
info->flags = flags & VM_NORESERVE;
INIT_LIST_HEAD(&info->swaplist);
cache_no_acl(inode);

switch (mode & S_IFMT) {
default:
inode->i_op = &shmem_special_inode_operations;
init_special_inode(inode, mode, dev);
break;
case S_IFREG:
inode->i_mapping->a_ops = &shmem_aops;
inode->i_op = &shmem_inode_operations;
inode->i_fop = &shmem_file_operations;
mpol_shared_policy_init(&info->policy,
shmem_get_sbmpol(sbinfo));
break;
case S_IFDIR:
inc_nlink(inode);
/* Some things misbehave if size == 0 on a directory */
inode->i_size = 2 * BOGO_DIRENT_SIZE;
inode->i_op = &shmem_dir_inode_operations;
inode->i_fop = &simple_dir_operations;
break;
case S_IFLNK:
/*
* Must not load anything in the rbtree,
* mpol_free_shared_policy will not be called.
*/
mpol_shared_policy_init(&info->policy, NULL);
break;
}
} else
shmem_free_inode(sb);
return inode;
}

#ifdef CONFIG_TMPFS
static const struct inode_operations shmem_symlink_inode_operations;
static const struct inode_operations shmem_symlink_inline_operations;

/*
* Normally tmpfs avoids the use of shmem_readpage and shmem_write_begin;
* but providing them allows a tmpfs file to be used for splice, sendfile, and
* below the loop driver, in the generic fashion that many filesystems support.
*/
static int shmem_readpage(struct file *file, struct page *page)
{
struct inode *inode = page->mapping->host;
int error = shmem_getpage(inode, page->index, &page, SGP_CACHE, NULL);
unlock_page(page);
return error;
}

static int
shmem_write_begin(struct file *file, struct address_space *mapping,
loff_t pos, unsigned len, unsigned flags,
struct page **pagep, void **fsdata)
{
struct inode *inode = mapping->host;
pgoff_t index = pos >> PAGE_CACHE_SHIFT;
*pagep = NULL;
return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
}

static int
shmem_write_end(struct file *file, struct address_space *mapping,
loff_t pos, unsigned len, unsigned copied,
struct page *page, void *fsdata)
{
struct inode *inode = mapping->host;

if (pos + copied > inode->i_size)
i_size_write(inode, pos + copied);

set_page_dirty(page);
unlock_page(page);
page_cache_release(page);

return copied;
}

static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
{
struct inode *inode = filp->f_path.dentry->d_inode;
struct address_space *mapping = inode->i_mapping;
unsigned long index, offset;
enum sgp_type sgp = SGP_READ;

/*
* Might this read be for a stacking filesystem? Then when reading
* holes of a sparse file, we actually need to allocate those pages,
* and even mark them dirty, so it cannot exceed the max_blocks limit.
*/
if (segment_eq(get_fs(), KERNEL_DS))
sgp = SGP_DIRTY;

index = *ppos >> PAGE_CACHE_SHIFT;
offset = *ppos & ~PAGE_CACHE_MASK;

for (;;) {
struct page *page = NULL;
unsigned long end_index, nr, ret;
loff_t i_size = i_size_read(inode);

end_index = i_size >> PAGE_CACHE_SHIFT;
if (index > end_index)
break;
if (index == end_index) {
nr = i_size & ~PAGE_CACHE_MASK;
if (nr <= offset)
break;
}

desc->error = shmem_getpage(inode, index, &page, sgp, NULL);
if (desc->error) {
if (desc->error == -EINVAL)
desc->error = 0;
break;
}
if (page)
unlock_page(page);

/*
* We must evaluate after, since reads (unlike writes)
* are called without i_mutex protection against truncate
*/
nr = PAGE_CACHE_SIZE;
i_size = i_size_read(inode);
end_index = i_size >> PAGE_CACHE_SHIFT;
if (index == end_index) {
nr = i_size & ~PAGE_CACHE_MASK;
if (nr <= offset) {
if (page)
page_cache_release(page);
break;
}
}
nr -= offset;

if (page) {
/*
* If users can be writing to this page using arbitrary
* virtual addresses, take care about potential aliasing
* before reading the page on the kernel side.
*/
if (mapping_writably_mapped(mapping))
flush_dcache_page(page);
/*
* Mark the page accessed if we read the beginning.
*/
if (!offset)
mark_page_accessed(page);
} else {
page = ZERO_PAGE(0);
page_cache_get(page);
}

/*
* Ok, we have the page, and it's up-to-date, so
* now we can copy it to user space...
*
* The actor routine returns how many bytes were actually used..
* NOTE! This may not be the same as how much of a user buffer
* we filled up (we may be padding etc), so we can only update
* "pos" here (the actor routine has to update the user buffer
* pointers and the remaining count).
*/
ret = actor(desc, page, offset, nr);
offset += ret;
index += offset >> PAGE_CACHE_SHIFT;
offset &= ~PAGE_CACHE_MASK;

page_cache_release(page);
if (ret != nr || !desc->count)
break;

cond_resched();
}

*ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
file_accessed(filp);
}

static ssize_t shmem_file_aio_read(struct kiocb *iocb,
const struct iovec *iov, unsigned long nr_segs, loff_t pos)
{
struct file *filp = iocb->ki_filp;
ssize_t retval;
unsigned long seg;
size_t count;
loff_t *ppos = &iocb->ki_pos;

retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
if (retval)
return retval;

for (seg = 0; seg < nr_segs; seg++) {
read_descriptor_t desc;

desc.written = 0;
desc.arg.buf = iov[seg].iov_base;
desc.count = iov[seg].iov_len;
if (desc.count == 0)
continue;
desc.error = 0;
do_shmem_file_read(filp, ppos, &desc, file_read_actor);
retval += desc.written;
if (desc.error) {
retval = retval ?: desc.error;
break;
}
if (desc.count > 0)
break;
}
return retval;
}

static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
{
struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);

buf->f_type = TMPFS_MAGIC;
buf->f_bsize = PAGE_CACHE_SIZE;
buf->f_namelen = NAME_MAX;
if (sbinfo->max_blocks) {
buf->f_blocks = sbinfo->max_blocks;
buf->f_bavail = buf->f_bfree =
sbinfo->max_blocks - percpu_counter_sum(&sbinfo->used_blocks);
}
if (sbinfo->max_inodes) {
buf->f_files = sbinfo->max_inodes;
buf->f_ffree = sbinfo->free_inodes;
}
/* else leave those fields 0 like simple_statfs */
return 0;
}

/*
* File creation. Allocate an inode, and we're done..
*/
static int
shmem_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
{
struct inode *inode;
int error = -ENOSPC;

inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
if (inode) {
error = security_inode_init_security(inode, dir,
&dentry->d_name, NULL,
NULL, NULL);
if (error) {
if (error != -EOPNOTSUPP) {
iput(inode);
return error;
}
}
#ifdef CONFIG_TMPFS_POSIX_ACL
error = generic_acl_init(inode, dir);
if (error) {
iput(inode);
return error;
}
#else
error = 0;
#endif
dir->i_size += BOGO_DIRENT_SIZE;
dir->i_ctime = dir->i_mtime = CURRENT_TIME;
d_instantiate(dentry, inode);
dget(dentry); /* Extra count - pin the dentry in core */
}
return error;
}

static int shmem_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
int error;

if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
return error;
inc_nlink(dir);
return 0;
}

static int shmem_create(struct inode *dir, struct dentry *dentry, int mode,
struct nameidata *nd)
{
return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
}

/*
* Link a file..
*/
static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
{
struct inode *inode = old_dentry->d_inode;
int ret;

/*
* No ordinary (disk based) filesystem counts links as inodes;
* but each new link needs a new dentry, pinning lowmem, and
* tmpfs dentries cannot be pruned until they are unlinked.
*/
ret = shmem_reserve_inode(inode->i_sb);
if (ret)
goto out;

dir->i_size += BOGO_DIRENT_SIZE;
inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
inc_nlink(inode);
ihold(inode); /* New dentry reference */
dget(dentry); /* Extra pinning count for the created dentry */
d_instantiate(dentry, inode);
out:
return ret;
}

static int shmem_unlink(struct inode *dir, struct dentry *dentry)
{
struct inode *inode = dentry->d_inode;

if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
shmem_free_inode(inode->i_sb);

dir->i_size -= BOGO_DIRENT_SIZE;
inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
drop_nlink(inode);
dput(dentry); /* Undo the count from "create" - this does all the work */
return 0;
}

static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
{
if (!simple_empty(dentry))
return -ENOTEMPTY;

drop_nlink(dentry->d_inode);
drop_nlink(dir);
return shmem_unlink(dir, dentry);
}

/*
* The VFS layer already does all the dentry stuff for rename,
* we just have to decrement the usage count for the target if
* it exists so that the VFS layer correctly free's it when it
* gets overwritten.
*/
static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
{
struct inode *inode = old_dentry->d_inode;
int they_are_dirs = S_ISDIR(inode->i_mode);

if (!simple_empty(new_dentry))
return -ENOTEMPTY;

if (new_dentry->d_inode) {
(void) shmem_unlink(new_dir, new_dentry);
if (they_are_dirs)
drop_nlink(old_dir);
} else if (they_are_dirs) {
drop_nlink(old_dir);
inc_nlink(new_dir);
}

old_dir->i_size -= BOGO_DIRENT_SIZE;
new_dir->i_size += BOGO_DIRENT_SIZE;
old_dir->i_ctime = old_dir->i_mtime =
new_dir->i_ctime = new_dir->i_mtime =
inode->i_ctime = CURRENT_TIME;
return 0;
}

static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
{
int error;
int len;
struct inode *inode;
struct page *page = NULL;
char *kaddr;
struct shmem_inode_info *info;

len = strlen(symname) + 1;
if (len > PAGE_CACHE_SIZE)
return -ENAMETOOLONG;

inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0, VM_NORESERVE);
if (!inode)
return -ENOSPC;

error = security_inode_init_security(inode, dir, &dentry->d_name, NULL,
NULL, NULL);
if (error) {
if (error != -EOPNOTSUPP) {
iput(inode);
return error;
}
error = 0;
}

info = SHMEM_I(inode);
inode->i_size = len-1;
if (len <= (char *)inode - (char *)info) {
/* do it inline */
memcpy(info, symname, len);
inode->i_op = &shmem_symlink_inline_operations;
} else {
error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
if (error) {
iput(inode);
return error;
}
inode->i_mapping->a_ops = &shmem_aops;
inode->i_op = &shmem_symlink_inode_operations;
kaddr = kmap_atomic(page, KM_USER0);
memcpy(kaddr, symname, len);
kunmap_atomic(kaddr, KM_USER0);
set_page_dirty(page);
unlock_page(page);
page_cache_release(page);
}
dir->i_size += BOGO_DIRENT_SIZE;
dir->i_ctime = dir->i_mtime = CURRENT_TIME;
d_instantiate(dentry, inode);
dget(dentry);
return 0;
}

static void *shmem_follow_link_inline(struct dentry *dentry, struct nameidata *nd)
{
nd_set_link(nd, (char *)SHMEM_I(dentry->d_inode));
return NULL;
}

static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)
{
struct page *page = NULL;
int res = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
nd_set_link(nd, res ? ERR_PTR(res) : kmap(page));
if (page)
unlock_page(page);
return page;
}

static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
{
if (!IS_ERR(nd_get_link(nd))) {
struct page *page = cookie;
kunmap(page);
mark_page_accessed(page);
page_cache_release(page);
}
}

static const struct inode_operations shmem_symlink_inline_operations = {
.readlink = generic_readlink,
.follow_link = shmem_follow_link_inline,
};

static const struct inode_operations shmem_symlink_inode_operations = {
.readlink = generic_readlink,
.follow_link = shmem_follow_link,
.put_link = shmem_put_link,
};

#ifdef CONFIG_TMPFS_POSIX_ACL
/*
* Superblocks without xattr inode operations will get security.* xattr
* support from the VFS "for free". As soon as we have any other xattrs
* like ACLs, we also need to implement the security.* handlers at
* filesystem level, though.
*/

static size_t shmem_xattr_security_list(struct dentry *dentry, char *list,
size_t list_len, const char *name,
size_t name_len, int handler_flags)
{
return security_inode_listsecurity(dentry->d_inode, list, list_len);
}

static int shmem_xattr_security_get(struct dentry *dentry, const char *name,
void *buffer, size_t size, int handler_flags)
{
if (strcmp(name, "") == 0)
return -EINVAL;
return xattr_getsecurity(dentry->d_inode, name, buffer, size);
}

static int shmem_xattr_security_set(struct dentry *dentry, const char *name,
const void *value, size_t size, int flags, int handler_flags)
{
if (strcmp(name, "") == 0)
return -EINVAL;
return security_inode_setsecurity(dentry->d_inode, name, value,
size, flags);
}

static const struct xattr_handler shmem_xattr_security_handler = {
.prefix = XATTR_SECURITY_PREFIX,
.list = shmem_xattr_security_list,
.get = shmem_xattr_security_get,
.set = shmem_xattr_security_set,
};

static const struct xattr_handler *shmem_xattr_handlers[] = {
&generic_acl_access_handler,
&generic_acl_default_handler,
&shmem_xattr_security_handler,
NULL
};
#endif

static struct dentry *shmem_get_parent(struct dentry *child)
{
return ERR_PTR(-ESTALE);
}

static int shmem_match(struct inode *ino, void *vfh)
{
__u32 *fh = vfh;
__u64 inum = fh[2];
inum = (inum << 32) | fh[1];
return ino->i_ino == inum && fh[0] == ino->i_generation;
}

static struct dentry *shmem_fh_to_dentry(struct super_block *sb,
struct fid *fid, int fh_len, int fh_type)
{
struct inode *inode;
struct dentry *dentry = NULL;
u64 inum = fid->raw[2];
inum = (inum << 32) | fid->raw[1];

if (fh_len < 3)
return NULL;

inode = ilookup5(sb, (unsigned long)(inum + fid->raw[0]),
shmem_match, fid->raw);
if (inode) {
dentry = d_find_alias(inode);
iput(inode);
}

return dentry;
}

static int shmem_encode_fh(struct dentry *dentry, __u32 *fh, int *len,
int connectable)
{
struct inode *inode = dentry->d_inode;

if (*len < 3) {
*len = 3;
return 255;
}

if (inode_unhashed(inode)) {
/* Unfortunately insert_inode_hash is not idempotent,
* so as we hash inodes here rather than at creation
* time, we need a lock to ensure we only try
* to do it once
*/
static DEFINE_SPINLOCK(lock);
spin_lock(&lock);
if (inode_unhashed(inode))
__insert_inode_hash(inode,
inode->i_ino + inode->i_generation);
spin_unlock(&lock);
}

fh[0] = inode->i_generation;
fh[1] = inode->i_ino;
fh[2] = ((__u64)inode->i_ino) >> 32;

*len = 3;
return 1;
}

static const struct export_operations shmem_export_ops = {
.get_parent = shmem_get_parent,
.encode_fh = shmem_encode_fh,
.fh_to_dentry = shmem_fh_to_dentry,
};

static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
bool remount)
{
char *this_char, *value, *rest;

while (options != NULL) {
this_char = options;
for (;;) {
/*
* NUL-terminate this option: unfortunately,
* mount options form a comma-separated list,
* but mpol's nodelist may also contain commas.
*/
options = strchr(options, ',');
if (options == NULL)
break;
options++;
if (!isdigit(*options)) {
options[-1] = '\0';
break;
}
}
if (!*this_char)
continue;
if ((value = strchr(this_char,'=')) != NULL) {
*value++ = 0;
} else {
printk(KERN_ERR
"tmpfs: No value for mount option '%s'\n",
this_char);
return 1;
}

if (!strcmp(this_char,"size")) {
unsigned long long size;
size = memparse(value,&rest);
if (*rest == '%') {
size <<= PAGE_SHIFT;
size *= totalram_pages;
do_div(size, 100);
rest++;
}
if (*rest)
goto bad_val;
sbinfo->max_blocks =
DIV_ROUND_UP(size, PAGE_CACHE_SIZE);
} else if (!strcmp(this_char,"nr_blocks")) {
sbinfo->max_blocks = memparse(value, &rest);
if (*rest)
goto bad_val;
} else if (!strcmp(this_char,"nr_inodes")) {
sbinfo->max_inodes = memparse(value, &rest);
if (*rest)
goto bad_val;
} else if (!strcmp(this_char,"mode")) {
if (remount)
continue;
sbinfo->mode = simple_strtoul(value, &rest, 8) & 07777;
if (*rest)
goto bad_val;
} else if (!strcmp(this_char,"uid")) {
if (remount)
continue;
sbinfo->uid = simple_strtoul(value, &rest, 0);
if (*rest)
goto bad_val;
} else if (!strcmp(this_char,"gid")) {
if (remount)
continue;
sbinfo->gid = simple_strtoul(value, &rest, 0);
if (*rest)
goto bad_val;
} else if (!strcmp(this_char,"mpol")) {
if (mpol_parse_str(value, &sbinfo->mpol, 1))
goto bad_val;
} else {
printk(KERN_ERR "tmpfs: Bad mount option %s\n",
this_char);
return 1;
}
}
return 0;

bad_val:
printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'\n",
value, this_char);
return 1;

}

static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
{
struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
struct shmem_sb_info config = *sbinfo;
unsigned long inodes;
int error = -EINVAL;

if (shmem_parse_options(data, &config, true))
return error;

spin_lock(&sbinfo->stat_lock);
inodes = sbinfo->max_inodes - sbinfo->free_inodes;
if (percpu_counter_compare(&sbinfo->used_blocks, config.max_blocks) > 0)
goto out;
if (config.max_inodes < inodes)
goto out;
/*
* Those tests also disallow limited->unlimited while any are in
* use, so i_blocks will always be zero when max_blocks is zero;
* but we must separately disallow unlimited->limited, because
* in that case we have no record of how much is already in use.
*/
if (config.max_blocks && !sbinfo->max_blocks)
goto out;
if (config.max_inodes && !sbinfo->max_inodes)
goto out;

error = 0;
sbinfo->max_blocks = config.max_blocks;
sbinfo->max_inodes = config.max_inodes;
sbinfo->free_inodes = config.max_inodes - inodes;

mpol_put(sbinfo->mpol);
sbinfo->mpol = config.mpol; /* transfers initial ref */
out:
spin_unlock(&sbinfo->stat_lock);
return error;
}

static int shmem_show_options(struct seq_file *seq, struct vfsmount *vfs)
{
struct shmem_sb_info *sbinfo = SHMEM_SB(vfs->mnt_sb);

if (sbinfo->max_blocks != shmem_default_max_blocks())
seq_printf(seq, ",size=%luk",
sbinfo->max_blocks << (PAGE_CACHE_SHIFT - 10));
if (sbinfo->max_inodes != shmem_default_max_inodes())
seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
seq_printf(seq, ",mode=%03o", sbinfo->mode);
if (sbinfo->uid != 0)
seq_printf(seq, ",uid=%u", sbinfo->uid);
if (sbinfo->gid != 0)
seq_printf(seq, ",gid=%u", sbinfo->gid);
shmem_show_mpol(seq, sbinfo->mpol);
return 0;
}
#endif /* CONFIG_TMPFS */

static void shmem_put_super(struct super_block *sb)
{
struct shmem_sb_info *sbinfo = SHMEM_SB(sb);

percpu_counter_destroy(&sbinfo->used_blocks);
kfree(sbinfo);
sb->s_fs_info = NULL;
}

int shmem_fill_super(struct super_block *sb, void *data, int silent)
{
struct inode *inode;
struct dentry *root;
struct shmem_sb_info *sbinfo;
int err = -ENOMEM;

/* Round up to L1_CACHE_BYTES to resist false sharing */
sbinfo = kzalloc(max((int)sizeof(struct shmem_sb_info),
L1_CACHE_BYTES), GFP_KERNEL);
if (!sbinfo)
return -ENOMEM;

sbinfo->mode = S_IRWXUGO | S_ISVTX;
sbinfo->uid = current_fsuid();
sbinfo->gid = current_fsgid();
sb->s_fs_info = sbinfo;

#ifdef CONFIG_TMPFS
/*
* Per default we only allow half of the physical ram per
* tmpfs instance, limiting inodes to one per page of lowmem;
* but the internal instance is left unlimited.
*/
if (!(sb->s_flags & MS_NOUSER)) {
sbinfo->max_blocks = shmem_default_max_blocks();
sbinfo->max_inodes = shmem_default_max_inodes();
if (shmem_parse_options(data, sbinfo, false)) {
err = -EINVAL;
goto failed;
}
}
sb->s_export_op = &shmem_export_ops;
#else
sb->s_flags |= MS_NOUSER;
#endif

spin_lock_init(&sbinfo->stat_lock);
if (percpu_counter_init(&sbinfo->used_blocks, 0))
goto failed;
sbinfo->free_inodes = sbinfo->max_inodes;

sb->s_maxbytes = SHMEM_MAX_BYTES;
sb->s_blocksize = PAGE_CACHE_SIZE;
sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
sb->s_magic = TMPFS_MAGIC;
sb->s_op = &shmem_ops;
sb->s_time_gran = 1;
#ifdef CONFIG_TMPFS_POSIX_ACL
sb->s_xattr = shmem_xattr_handlers;
sb->s_flags |= MS_POSIXACL;
#endif

inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
if (!inode)
goto failed;
inode->i_uid = sbinfo->uid;
inode->i_gid = sbinfo->gid;
root = d_alloc_root(inode);
if (!root)
goto failed_iput;
sb->s_root = root;
return 0;

failed_iput:
iput(inode);
failed:
shmem_put_super(sb);
return err;
}

static struct kmem_cache *shmem_inode_cachep;

static struct inode *shmem_alloc_inode(struct super_block *sb)
{
struct shmem_inode_info *p;
p = (struct shmem_inode_info *)kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);
if (!p)
return NULL;
return &p->vfs_inode;
}

static void shmem_i_callback(struct rcu_head *head)
{
struct inode *inode = container_of(head, struct inode, i_rcu);
INIT_LIST_HEAD(&inode->i_dentry);
kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
}

static void shmem_destroy_inode(struct inode *inode)
{
if ((inode->i_mode & S_IFMT) == S_IFREG) {
/* only struct inode is valid if it's an inline symlink */
mpol_free_shared_policy(&SHMEM_I(inode)->policy);
}
call_rcu(&inode->i_rcu, shmem_i_callback);
}

static void init_once(void *foo)
{
struct shmem_inode_info *p = (struct shmem_inode_info *) foo;

inode_init_once(&p->vfs_inode);
}

static int init_inodecache(void)
{
shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
sizeof(struct shmem_inode_info),
0, SLAB_PANIC, init_once);
return 0;
}

static void destroy_inodecache(void)
{
kmem_cache_destroy(shmem_inode_cachep);
}

static const struct address_space_operations shmem_aops = {
.writepage = shmem_writepage,
.set_page_dirty = __set_page_dirty_no_writeback,
#ifdef CONFIG_TMPFS
.readpage = shmem_readpage,
.write_begin = shmem_write_begin,
.write_end = shmem_write_end,
#endif
.migratepage = migrate_page,
.error_remove_page = generic_error_remove_page,
};

static const struct file_operations shmem_file_operations = {
.mmap = shmem_mmap,
#ifdef CONFIG_TMPFS
.llseek = generic_file_llseek,
.read = do_sync_read,
.write = do_sync_write,
.aio_read = shmem_file_aio_read,
.aio_write = generic_file_aio_write,
.fsync = noop_fsync,
.splice_read = generic_file_splice_read,
.splice_write = generic_file_splice_write,
#endif
};

static const struct inode_operations shmem_inode_operations = {
.setattr = shmem_notify_change,
.truncate_range = shmem_truncate_range,
#ifdef CONFIG_TMPFS_POSIX_ACL
.setxattr = generic_setxattr,
.getxattr = generic_getxattr,
.listxattr = generic_listxattr,
.removexattr = generic_removexattr,
.check_acl = generic_check_acl,
#endif

};

static const struct inode_operations shmem_dir_inode_operations = {
#ifdef CONFIG_TMPFS
.create = shmem_create,
.lookup = simple_lookup,
.link = shmem_link,
.unlink = shmem_unlink,
.symlink = shmem_symlink,
.mkdir = shmem_mkdir,
.rmdir = shmem_rmdir,
.mknod = shmem_mknod,
.rename = shmem_rename,
#endif
#ifdef CONFIG_TMPFS_POSIX_ACL
.setattr = shmem_notify_change,
.setxattr = generic_setxattr,
.getxattr = generic_getxattr,
.listxattr = generic_listxattr,
.removexattr = generic_removexattr,
.check_acl = generic_check_acl,
#endif
};

static const struct inode_operations shmem_special_inode_operations = {
#ifdef CONFIG_TMPFS_POSIX_ACL
.setattr = shmem_notify_change,
.setxattr = generic_setxattr,
.getxattr = generic_getxattr,
.listxattr = generic_listxattr,
.removexattr = generic_removexattr,
.check_acl = generic_check_acl,
#endif
};

static const struct super_operations shmem_ops = {
.alloc_inode = shmem_alloc_inode,
.destroy_inode = shmem_destroy_inode,
#ifdef CONFIG_TMPFS
.statfs = shmem_statfs,
.remount_fs = shmem_remount_fs,
.show_options = shmem_show_options,
#endif
.evict_inode = shmem_evict_inode,
.drop_inode = generic_delete_inode,
.put_super = shmem_put_super,
};

static const struct vm_operations_struct shmem_vm_ops = {
.fault = shmem_fault,
#ifdef CONFIG_NUMA
.set_policy = shmem_set_policy,
.get_policy = shmem_get_policy,
#endif
};


static struct dentry *shmem_mount(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data)
{
return mount_nodev(fs_type, flags, data, shmem_fill_super);
}

static struct file_system_type tmpfs_fs_type = {
.owner = THIS_MODULE,
.name = "tmpfs",
.mount = shmem_mount,
.kill_sb = kill_litter_super,
};

int __init init_tmpfs(void)
{
int error;

error = bdi_init(&shmem_backing_dev_info);
if (error)
goto out4;

error = init_inodecache();
if (error)
goto out3;

error = register_filesystem(&tmpfs_fs_type);
if (error) {
printk(KERN_ERR "Could not register tmpfs\n");
goto out2;
}

shm_mnt = vfs_kern_mount(&tmpfs_fs_type, MS_NOUSER,
tmpfs_fs_type.name, NULL);
if (IS_ERR(shm_mnt)) {
error = PTR_ERR(shm_mnt);
printk(KERN_ERR "Could not kern_mount tmpfs\n");
goto out1;
}
return 0;

out1:
unregister_filesystem(&tmpfs_fs_type);
out2:
destroy_inodecache();
out3:
bdi_destroy(&shmem_backing_dev_info);
out4:
shm_mnt = ERR_PTR(error);
return error;
}

#ifdef CONFIG_CGROUP_MEM_RES_CTLR
/**
* mem_cgroup_get_shmem_target - find a page or entry assigned to the shmem file
* @inode: the inode to be searched
* @pgoff: the offset to be searched
* @pagep: the pointer for the found page to be stored
* @ent: the pointer for the found swap entry to be stored
*
* If a page is found, refcount of it is incremented. Callers should handle
* these refcount.
*/
void mem_cgroup_get_shmem_target(struct inode *inode, pgoff_t pgoff,
struct page **pagep, swp_entry_t *ent)
{
swp_entry_t entry = { .val = 0 }, *ptr;
struct page *page = NULL;
struct shmem_inode_info *info = SHMEM_I(inode);

if ((pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
goto out;

spin_lock(&info->lock);
ptr = shmem_swp_entry(info, pgoff, NULL);
#ifdef CONFIG_SWAP
if (ptr && ptr->val) {
entry.val = ptr->val;
page = find_get_page(&swapper_space, entry.val);
} else
#endif
page = find_get_page(inode->i_mapping, pgoff);
if (ptr)
shmem_swp_unmap(ptr);
spin_unlock(&info->lock);
out:
*pagep = page;
*ent = entry;
}
#endif

#else /* !CONFIG_SHMEM */

/*
* tiny-shmem: simple shmemfs and tmpfs using ramfs code
*
* This is intended for small system where the benefits of the full
* shmem code (swap-backed and resource-limited) are outweighed by
* their complexity. On systems without swap this code should be
* effectively equivalent, but much lighter weight.
*/

#include <linux/ramfs.h>

static struct file_system_type tmpfs_fs_type = {
.name = "tmpfs",
.mount = ramfs_mount,
.kill_sb = kill_litter_super,
};

int __init init_tmpfs(void)
{
BUG_ON(register_filesystem(&tmpfs_fs_type) != 0);

shm_mnt = kern_mount(&tmpfs_fs_type);
BUG_ON(IS_ERR(shm_mnt));

return 0;
}

int shmem_unuse(swp_entry_t entry, struct page *page)
{
return 0;
}

int shmem_lock(struct file *file, int lock, struct user_struct *user)
{
return 0;
}

#ifdef CONFIG_CGROUP_MEM_RES_CTLR
/**
* mem_cgroup_get_shmem_target - find a page or entry assigned to the shmem file
* @inode: the inode to be searched
* @pgoff: the offset to be searched
* @pagep: the pointer for the found page to be stored
* @ent: the pointer for the found swap entry to be stored
*
* If a page is found, refcount of it is incremented. Callers should handle
* these refcount.
*/
void mem_cgroup_get_shmem_target(struct inode *inode, pgoff_t pgoff,
struct page **pagep, swp_entry_t *ent)
{
struct page *page = NULL;

if ((pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
goto out;
page = find_get_page(inode->i_mapping, pgoff);
out:
*pagep = page;
*ent = (swp_entry_t){ .val = 0 };
}
#endif

#define shmem_vm_ops generic_file_vm_ops
#define shmem_file_operations ramfs_file_operations
#define shmem_get_inode(sb, dir, mode, dev, flags) ramfs_get_inode(sb, dir, mode, dev)
#define shmem_acct_size(flags, size) 0
#define shmem_unacct_size(flags, size) do {} while (0)
#define SHMEM_MAX_BYTES MAX_LFS_FILESIZE

#endif /* CONFIG_SHMEM */

/* common code */

/**
* shmem_file_setup - get an unlinked file living in tmpfs
* @name: name for dentry (to be seen in /proc/<pid>/maps
* @size: size to be set for the file
* @flags: VM_NORESERVE suppresses pre-accounting of the entire object size
*/
struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags)
{
int error;
struct file *file;
struct inode *inode;
struct path path;
struct dentry *root;
struct qstr this;

if (IS_ERR(shm_mnt))
return (void *)shm_mnt;

if (size < 0 || size > SHMEM_MAX_BYTES)
return ERR_PTR(-EINVAL);

if (shmem_acct_size(flags, size))
return ERR_PTR(-ENOMEM);

error = -ENOMEM;
this.name = name;
this.len = strlen(name);
this.hash = 0; /* will go */
root = shm_mnt->mnt_root;
path.dentry = d_alloc(root, &this);
if (!path.dentry)
goto put_memory;
path.mnt = mntget(shm_mnt);

error = -ENOSPC;
inode = shmem_get_inode(root->d_sb, NULL, S_IFREG | S_IRWXUGO, 0, flags);
if (!inode)
goto put_dentry;

d_instantiate(path.dentry, inode);
inode->i_size = size;
inode->i_nlink = 0; /* It is unlinked */
#ifndef CONFIG_MMU
error = ramfs_nommu_expand_for_mapping(inode, size);
if (error)
goto put_dentry;
#endif

error = -ENFILE;
file = alloc_file(&path, FMODE_WRITE | FMODE_READ,
&shmem_file_operations);
if (!file)
goto put_dentry;

return file;

put_dentry:
path_put(&path);
put_memory:
shmem_unacct_size(flags, size);
return ERR_PTR(error);
}
EXPORT_SYMBOL_GPL(shmem_file_setup);

/**
* shmem_zero_setup - setup a shared anonymous mapping
* @vma: the vma to be mmapped is prepared by do_mmap_pgoff
*/
int shmem_zero_setup(struct vm_area_struct *vma)
{
struct file *file;
loff_t size = vma->vm_end - vma->vm_start;

file = shmem_file_setup("dev/zero", size, vma->vm_flags);
if (IS_ERR(file))
return PTR_ERR(file);

if (vma->vm_file)
fput(vma->vm_file);
vma->vm_file = file;
vma->vm_ops = &shmem_vm_ops;
vma->vm_flags |= VM_CAN_NONLINEAR;
return 0;
}
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