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shmem.c
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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) 2002-2003 Hugh Dickins.
* Copyright (C) 2002-2003 VERITAS Software Corporation.
*
* This file is released under the GPL.
*/
/*
* 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/config.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/devfs_fs_kernel.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/file.h>
#include <linux/swap.h>
#include <linux/pagemap.h>
#include <linux/string.h>
#include <linux/locks.h>
#include <linux/smp_lock.h>
#include <asm/uaccess.h>
#include <asm/div64.h>
/* This magic number is used in glibc for posix shared memory */
#define TMPFS_MAGIC 0x01021994
#define ENTRIES_PER_PAGE (PAGE_CACHE_SIZE/sizeof(unsigned long))
#define ENTRIES_PER_PAGEPAGE (ENTRIES_PER_PAGE*ENTRIES_PER_PAGE)
#define BLOCKS_PER_PAGE (PAGE_CACHE_SIZE/512)
#define SHMEM_MAX_INDEX (SHMEM_NR_DIRECT + (ENTRIES_PER_PAGEPAGE/2) * (ENTRIES_PER_PAGE+1))
#define SHMEM_MAX_BYTES ((unsigned long long)SHMEM_MAX_INDEX << PAGE_CACHE_SHIFT)
#define VM_ACCT(size) (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
/* Pretend that each entry is of this size in directory's i_size */
#define BOGO_DIRENT_SIZE 20
#define SHMEM_SB(sb) (&sb->u.shmem_sb)
/* 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_WRITE, /* may exceed i_size, may allocate page */
};
static int shmem_getpage(struct inode *inode, unsigned long idx,
struct page **pagep, enum sgp_type sgp);
static struct super_operations shmem_ops;
static struct address_space_operations shmem_aops;
static struct file_operations shmem_file_operations;
static struct inode_operations shmem_inode_operations;
static struct inode_operations shmem_dir_inode_operations;
static struct vm_operations_struct shmem_vm_ops;
LIST_HEAD(shmem_inodes);
static spinlock_t shmem_ilock = SPIN_LOCK_UNLOCKED;
static void shmem_free_block(struct inode *inode)
{
struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
spin_lock(&sbinfo->stat_lock);
sbinfo->free_blocks++;
inode->i_blocks -= BLOCKS_PER_PAGE;
spin_unlock(&sbinfo->stat_lock);
}
static void shmem_removepage(struct page *page)
{
if (!PageLaunder(page))
shmem_free_block(page->mapping->host);
}
/*
* 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 0, else it will use the page for the needed block,
* setting it to 0 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, unsigned long *page)
{
unsigned long offset;
void **dir;
if (index < SHMEM_NR_DIRECT)
return info->i_direct+index;
if (!info->i_indirect) {
if (page) {
info->i_indirect = (void **) *page;
*page = 0;
}
return NULL; /* need another page */
}
index -= SHMEM_NR_DIRECT;
offset = index % ENTRIES_PER_PAGE;
index /= ENTRIES_PER_PAGE;
dir = 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;
if (!*dir) {
if (page) {
*dir = (void *) *page;
*page = 0;
}
return NULL; /* need another page */
}
dir = (void **) *dir;
}
dir += index;
if (!*dir) {
if (!page || !*page)
return NULL; /* need a page */
*dir = (void *) *page;
*page = 0;
}
return (swp_entry_t *) *dir + offset;
}
/*
* shmem_swp_alloc - get the position of the swap entry for the page.
* If it does not exist allocate the entry.
*
* @info: info structure for the inode
* @index: index of the page to find
* @sgp: check and recheck i_size? skip allocation?
*/
static swp_entry_t *shmem_swp_alloc(struct shmem_inode_info *info, unsigned long index, enum sgp_type sgp)
{
struct inode *inode = info->inode;
struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
unsigned long page = 0;
swp_entry_t *entry;
static const swp_entry_t unswapped = {0};
if (sgp != SGP_WRITE &&
((loff_t) index << PAGE_CACHE_SHIFT) >= inode->i_size)
return ERR_PTR(-EINVAL);
while (!(entry = shmem_swp_entry(info, index, &page))) {
if (sgp == SGP_READ)
return (swp_entry_t *) &unswapped;
/*
* Test free_blocks against 1 not 0, since we have 1 data
* page (and perhaps indirect index pages) yet to allocate:
* a waste to allocate index if we cannot allocate data.
*/
spin_lock(&sbinfo->stat_lock);
if (sbinfo->free_blocks <= 1) {
spin_unlock(&sbinfo->stat_lock);
return ERR_PTR(-ENOSPC);
}
sbinfo->free_blocks--;
inode->i_blocks += BLOCKS_PER_PAGE;
spin_unlock(&sbinfo->stat_lock);
spin_unlock(&info->lock);
page = get_zeroed_page(GFP_USER);
spin_lock(&info->lock);
if (!page) {
shmem_free_block(inode);
return ERR_PTR(-ENOMEM);
}
if (sgp != SGP_WRITE &&
((loff_t) index << PAGE_CACHE_SHIFT) >= inode->i_size) {
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_block(inode);
free_page(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
*/
static int shmem_free_swp(swp_entry_t *dir, swp_entry_t *edir)
{
swp_entry_t *ptr;
int freed = 0;
for (ptr = dir; ptr < edir; ptr++) {
if (ptr->val) {
free_swap_and_cache(*ptr);
*ptr = (swp_entry_t){0};
freed++;
}
}
return freed;
}
/*
* shmem_truncate_direct - free the swap entries of a whole doubly
* indirect block
*
* @info: the info structure of the inode
* @dir: pointer to the pointer to the block
* @start: offset to start from (in pages)
* @len: how many pages are stored in this block
*/
static inline unsigned long
shmem_truncate_direct(struct shmem_inode_info *info, swp_entry_t ***dir, unsigned long start, unsigned long len)
{
swp_entry_t **last, **ptr;
unsigned long off, freed_swp, freed = 0;
last = *dir + (len + ENTRIES_PER_PAGE - 1) / ENTRIES_PER_PAGE;
off = start % ENTRIES_PER_PAGE;
for (ptr = *dir + start/ENTRIES_PER_PAGE; ptr < last; ptr++, off = 0) {
if (!*ptr)
continue;
if (info->swapped) {
freed_swp = shmem_free_swp(*ptr + off,
*ptr + ENTRIES_PER_PAGE);
info->swapped -= freed_swp;
freed += freed_swp;
}
if (!off) {
freed++;
free_page((unsigned long) *ptr);
*ptr = 0;
}
}
if (!start) {
freed++;
free_page((unsigned long) *dir);
*dir = 0;
}
return freed;
}
/*
* shmem_truncate_indirect - truncate an inode
*
* @info: the info structure of the inode
* @index: the index to truncate
*
* This function locates the last doubly indirect block and calls
* then shmem_truncate_direct to do the real work
*/
static inline unsigned long
shmem_truncate_indirect(struct shmem_inode_info *info, unsigned long index)
{
swp_entry_t ***base;
unsigned long baseidx, start;
unsigned long len = info->next_index;
unsigned long freed;
if (len <= SHMEM_NR_DIRECT) {
info->next_index = index;
if (!info->swapped)
return 0;
freed = shmem_free_swp(info->i_direct + index,
info->i_direct + len);
info->swapped -= freed;
return freed;
}
if (len <= ENTRIES_PER_PAGEPAGE/2 + SHMEM_NR_DIRECT) {
len -= SHMEM_NR_DIRECT;
base = (swp_entry_t ***) &info->i_indirect;
baseidx = SHMEM_NR_DIRECT;
} else {
len -= ENTRIES_PER_PAGEPAGE/2 + SHMEM_NR_DIRECT;
BUG_ON(len > ENTRIES_PER_PAGEPAGE*ENTRIES_PER_PAGE/2);
baseidx = len - 1;
baseidx -= baseidx % ENTRIES_PER_PAGEPAGE;
base = (swp_entry_t ***) info->i_indirect +
ENTRIES_PER_PAGE/2 + baseidx/ENTRIES_PER_PAGEPAGE;
len -= baseidx;
baseidx += ENTRIES_PER_PAGEPAGE/2 + SHMEM_NR_DIRECT;
}
if (index > baseidx) {
info->next_index = index;
start = index - baseidx;
} else {
info->next_index = baseidx;
start = 0;
}
return *base? shmem_truncate_direct(info, base, start, len): 0;
}
static void shmem_truncate(struct inode *inode)
{
struct shmem_inode_info *info = SHMEM_I(inode);
struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
unsigned long freed = 0;
unsigned long index;
inode->i_ctime = inode->i_mtime = CURRENT_TIME;
index = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
if (index >= info->next_index)
return;
spin_lock(&info->lock);
while (index < info->next_index)
freed += shmem_truncate_indirect(info, index);
BUG_ON(info->swapped > info->next_index);
spin_unlock(&info->lock);
spin_lock(&sbinfo->stat_lock);
sbinfo->free_blocks += freed;
inode->i_blocks -= freed*BLOCKS_PER_PAGE;
spin_unlock(&sbinfo->stat_lock);
}
static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
{
struct inode *inode = dentry->d_inode;
struct page *page = NULL;
int error;
if (attr->ia_valid & ATTR_SIZE) {
if (attr->ia_size < 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 cannnot miss it were
* it assigned to swap.
*/
if (attr->ia_size & (PAGE_CACHE_SIZE-1)) {
(void) shmem_getpage(inode,
attr->ia_size>>PAGE_CACHE_SHIFT,
&page, SGP_READ);
}
}
}
error = inode_change_ok(inode, attr);
if (!error)
error = inode_setattr(inode, attr);
if (page)
page_cache_release(page);
return error;
}
static void shmem_delete_inode(struct inode *inode)
{
struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
struct shmem_inode_info *info = SHMEM_I(inode);
if (inode->i_op->truncate == shmem_truncate) {
spin_lock(&shmem_ilock);
list_del(&info->list);
spin_unlock(&shmem_ilock);
inode->i_size = 0;
shmem_truncate(inode);
}
BUG_ON(inode->i_blocks);
spin_lock(&sbinfo->stat_lock);
sbinfo->free_inodes++;
spin_unlock(&sbinfo->stat_lock);
clear_inode(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 inode *inode;
struct address_space *mapping;
swp_entry_t *ptr;
unsigned long idx;
unsigned long limit;
int offset;
idx = 0;
ptr = info->i_direct;
spin_lock(&info->lock);
offset = info->next_index;
if (offset > SHMEM_NR_DIRECT)
offset = SHMEM_NR_DIRECT;
offset = shmem_find_swp(entry, ptr, ptr + offset);
if (offset >= 0)
goto found;
for (idx = SHMEM_NR_DIRECT; idx < info->next_index;
idx += ENTRIES_PER_PAGE) {
ptr = shmem_swp_entry(info, idx, NULL);
if (!ptr)
continue;
offset = info->next_index - idx;
if (offset > ENTRIES_PER_PAGE)
offset = ENTRIES_PER_PAGE;
offset = shmem_find_swp(entry, ptr, ptr + offset);
if (offset >= 0)
goto found;
}
spin_unlock(&info->lock);
return 0;
found:
idx += offset;
inode = info->inode;
mapping = inode->i_mapping;
delete_from_swap_cache(page);
/* Racing against delete or truncate? Must leave out of page cache */
limit = (inode->i_state & I_FREEING)? 0:
(inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
if (idx >= limit || add_to_page_cache_unique(page,
mapping, idx, page_hash(mapping, idx)) == 0) {
ptr[offset].val = 0;
info->swapped--;
} else if (add_to_swap_cache(page, entry) != 0)
BUG();
spin_unlock(&info->lock);
SetPageUptodate(page);
/*
* Decrement swap count even when the entry is left behind:
* try_to_unuse will skip over mms, then reincrement count.
*/
swap_free(entry);
return 1;
}
/*
* shmem_unuse() search for an eventually swapped out shmem page.
*/
int shmem_unuse(swp_entry_t entry, struct page *page)
{
struct list_head *p;
struct shmem_inode_info *info;
int found = 0;
spin_lock(&shmem_ilock);
list_for_each(p, &shmem_inodes) {
info = list_entry(p, struct shmem_inode_info, list);
if (info->swapped && shmem_unuse_inode(info, entry, page)) {
/* move head to start search for next from here */
list_move_tail(&shmem_inodes, &info->list);
found = 1;
break;
}
}
spin_unlock(&shmem_ilock);
return found;
}
/*
* Move the page from the page cache to the swap cache.
*/
static int shmem_writepage(struct page *page)
{
struct shmem_inode_info *info;
swp_entry_t *entry, swap;
struct address_space *mapping;
unsigned long index;
struct inode *inode;
BUG_ON(!PageLocked(page));
if (!PageLaunder(page))
return fail_writepage(page);
mapping = page->mapping;
index = page->index;
inode = mapping->host;
info = SHMEM_I(inode);
if (info->flags & VM_LOCKED)
return fail_writepage(page);
getswap:
swap = get_swap_page();
if (!swap.val)
return fail_writepage(page);
spin_lock(&info->lock);
BUG_ON(index >= info->next_index);
entry = shmem_swp_entry(info, index, NULL);
BUG_ON(!entry);
BUG_ON(entry->val);
/* Remove it from the page cache */
remove_inode_page(page);
page_cache_release(page);
/* Add it to the swap cache */
if (add_to_swap_cache(page, swap) != 0) {
/*
* Raced with "speculative" read_swap_cache_async.
* Add page back to page cache, unref swap, try again.
*/
add_to_page_cache_locked(page, mapping, index);
spin_unlock(&info->lock);
swap_free(swap);
goto getswap;
}
*entry = swap;
info->swapped++;
spin_unlock(&info->lock);
SetPageUptodate(page);
set_page_dirty(page);
UnlockPage(page);
return 0;
}
/*
* 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)
{
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;
swp_entry_t *entry;
swp_entry_t swap;
int error = 0;
if (idx >= SHMEM_MAX_INDEX)
return -EFBIG;
/*
* 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 and shmem_prepare_write pass 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 && Page_Uptodate(filepage))
goto done;
spin_lock(&info->lock);
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) {
spin_unlock(&info->lock);
swapin_readahead(swap);
swappage = read_swap_cache_async(swap);
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;
spin_unlock(&info->lock);
if (error)
goto failed;
goto repeat;
}
wait_on_page(swappage);
page_cache_release(swappage);
goto repeat;
}
/* We have to do this with page locked to prevent races */
if (TryLockPage(swappage)) {
spin_unlock(&info->lock);
wait_on_page(swappage);
page_cache_release(swappage);
goto repeat;
}
if (!Page_Uptodate(swappage)) {
spin_unlock(&info->lock);
UnlockPage(swappage);
page_cache_release(swappage);
error = -EIO;
goto failed;
}
delete_from_swap_cache(swappage);
if (filepage) {
entry->val = 0;
info->swapped--;
spin_unlock(&info->lock);
flush_page_to_ram(swappage);
copy_highpage(filepage, swappage);
UnlockPage(swappage);
page_cache_release(swappage);
flush_dcache_page(filepage);
SetPageUptodate(filepage);
SetPageDirty(filepage);
swap_free(swap);
} else if (add_to_page_cache_unique(swappage,
mapping, idx, page_hash(mapping, idx)) == 0) {
entry->val = 0;
info->swapped--;
spin_unlock(&info->lock);
filepage = swappage;
SetPageUptodate(filepage);
SetPageDirty(filepage);
swap_free(swap);
} else {
if (add_to_swap_cache(swappage, swap) != 0)
BUG();
spin_unlock(&info->lock);
SetPageUptodate(swappage);
SetPageDirty(swappage);
UnlockPage(swappage);
page_cache_release(swappage);
goto repeat;
}
} else if (sgp == SGP_READ && !filepage) {
filepage = find_get_page(mapping, idx);
if (filepage &&
(!Page_Uptodate(filepage) || TryLockPage(filepage))) {
spin_unlock(&info->lock);
wait_on_page(filepage);
page_cache_release(filepage);
filepage = NULL;
goto repeat;
}
spin_unlock(&info->lock);
} else {
sbinfo = SHMEM_SB(inode->i_sb);
spin_lock(&sbinfo->stat_lock);
if (sbinfo->free_blocks == 0) {
spin_unlock(&sbinfo->stat_lock);
spin_unlock(&info->lock);
error = -ENOSPC;
goto failed;
}
sbinfo->free_blocks--;
inode->i_blocks += BLOCKS_PER_PAGE;
spin_unlock(&sbinfo->stat_lock);
if (!filepage) {
spin_unlock(&info->lock);
filepage = page_cache_alloc(mapping);
if (!filepage) {
shmem_free_block(inode);
error = -ENOMEM;
goto failed;
}
spin_lock(&info->lock);
entry = shmem_swp_alloc(info, idx, sgp);
if (IS_ERR(entry))
error = PTR_ERR(entry);
if (error || entry->val ||
add_to_page_cache_unique(filepage,
mapping, idx, page_hash(mapping, idx)) != 0) {
spin_unlock(&info->lock);
page_cache_release(filepage);
shmem_free_block(inode);
filepage = NULL;
if (error)
goto failed;
goto repeat;
}
}
spin_unlock(&info->lock);
clear_highpage(filepage);
flush_dcache_page(filepage);
SetPageUptodate(filepage);
}
done:
if (!*pagep) {
if (filepage) {
UnlockPage(filepage);
*pagep = filepage;
} else
*pagep = ZERO_PAGE(0);
}
return 0;
failed:
if (*pagep != filepage) {
UnlockPage(filepage);
page_cache_release(filepage);
}
return error;
}
struct page *shmem_nopage(struct vm_area_struct *vma, unsigned long address, int unused)
{
struct inode *inode = vma->vm_file->f_dentry->d_inode;
struct page *page = NULL;
unsigned long idx;
int error;
idx = (address - vma->vm_start) >> PAGE_SHIFT;
idx += vma->vm_pgoff;
idx >>= PAGE_CACHE_SHIFT - PAGE_SHIFT;
error = shmem_getpage(inode, idx, &page, SGP_CACHE);
if (error)
return (error == -ENOMEM)? NOPAGE_OOM: NOPAGE_SIGBUS;
mark_page_accessed(page);
flush_page_to_ram(page);
return page;
}
void shmem_lock(struct file *file, int lock)
{
struct inode *inode = file->f_dentry->d_inode;
struct shmem_inode_info *info = SHMEM_I(inode);
spin_lock(&info->lock);
if (lock)
info->flags |= VM_LOCKED;
else
info->flags &= ~VM_LOCKED;
spin_unlock(&info->lock);
}
static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
{
struct vm_operations_struct *ops;
struct inode *inode = file->f_dentry->d_inode;
ops = &shmem_vm_ops;
if (!S_ISREG(inode->i_mode))
return -EACCES;
UPDATE_ATIME(inode);
vma->vm_ops = ops;
return 0;
}
static struct inode *shmem_get_inode(struct super_block *sb, int mode, int dev)
{
struct inode *inode;
struct shmem_inode_info *info;
struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
spin_lock(&sbinfo->stat_lock);
if (!sbinfo->free_inodes) {
spin_unlock(&sbinfo->stat_lock);
return NULL;
}
sbinfo->free_inodes--;
spin_unlock(&sbinfo->stat_lock);
inode = new_inode(sb);
if (inode) {
inode->i_mode = mode;
inode->i_uid = current->fsuid;
inode->i_gid = current->fsgid;
inode->i_blksize = PAGE_CACHE_SIZE;
inode->i_blocks = 0;
inode->i_rdev = NODEV;
inode->i_mapping->a_ops = &shmem_aops;
inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
info = SHMEM_I(inode);
info->inode = inode;
spin_lock_init(&info->lock);
switch (mode & S_IFMT) {
default:
init_special_inode(inode, mode, dev);
break;
case S_IFREG:
inode->i_op = &shmem_inode_operations;
inode->i_fop = &shmem_file_operations;
spin_lock(&shmem_ilock);
list_add_tail(&info->list, &shmem_inodes);
spin_unlock(&shmem_ilock);
break;
case S_IFDIR:
inode->i_nlink++;
/* 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 = &dcache_dir_ops;
break;
case S_IFLNK:
break;
}
}
return inode;
}
static int shmem_set_size(struct shmem_sb_info *info,
unsigned long max_blocks, unsigned long max_inodes)
{
int error;
unsigned long blocks, inodes;
spin_lock(&info->stat_lock);
blocks = info->max_blocks - info->free_blocks;
inodes = info->max_inodes - info->free_inodes;
error = -EINVAL;
if (max_blocks < blocks)
goto out;
if (max_inodes < inodes)
goto out;
error = 0;
info->max_blocks = max_blocks;
info->free_blocks = max_blocks - blocks;
info->max_inodes = max_inodes;
info->free_inodes = max_inodes - inodes;
out:
spin_unlock(&info->stat_lock);
return error;
}
#ifdef CONFIG_TMPFS
static struct inode_operations shmem_symlink_inode_operations;
static struct inode_operations shmem_symlink_inline_operations;
/*
* tmpfs itself makes no use of generic_file_read, generic_file_mmap
* or generic_file_write; but shmem_readpage, shmem_prepare_write and
* shmem_commit_write let a tmpfs file be used below the loop driver,
* and shmem_readpage lets a tmpfs file be used by sendfile.
*/
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);
UnlockPage(page);
return error;
}
static int
shmem_prepare_write(struct file *file, struct page *page, unsigned offset, unsigned to)
{
struct inode *inode = page->mapping->host;
return shmem_getpage(inode, page->index, &page, SGP_WRITE);
}
static int
shmem_commit_write(struct file *file, struct page *page, unsigned offset, unsigned to)
{
struct inode *inode = page->mapping->host;
loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
if (pos > inode->i_size)
inode->i_size = pos;
SetPageDirty(page);
return 0;
}
static ssize_t
shmem_file_write(struct file *file, const char *buf, size_t count, loff_t *ppos)
{
struct inode *inode = file->f_dentry->d_inode;
loff_t pos;
unsigned long written;
int err;
if ((ssize_t) count < 0)
return -EINVAL;
if (!access_ok(VERIFY_READ, buf, count))
return -EFAULT;
down(&inode->i_sem);
pos = *ppos;
written = 0;
err = precheck_file_write(file, inode, &count, &pos);
if (err || !count)
goto out;
remove_suid(inode);
inode->i_ctime = inode->i_mtime = CURRENT_TIME;
do {
struct page *page = NULL;
unsigned long bytes, index, offset;
char *kaddr;
int left;
offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
index = pos >> PAGE_CACHE_SHIFT;
bytes = PAGE_CACHE_SIZE - offset;
if (bytes > count)
bytes = count;
/*
* We don't hold page lock across copy from user -
* what would it guard against? - so no deadlock here.
*/
err = shmem_getpage(inode, index, &page, SGP_WRITE);
if (err)
break;
kaddr = kmap(page);
left = __copy_from_user(kaddr + offset, buf, bytes);
kunmap(page);
written += bytes;
count -= bytes;
pos += bytes;
buf += bytes;
if (pos > inode->i_size)
inode->i_size = pos;
flush_dcache_page(page);
SetPageDirty(page);
SetPageReferenced(page);
page_cache_release(page);
if (left) {
pos -= left;
written -= left;
err = -EFAULT;
break;
}
} while (count);
*ppos = pos;
if (written)
err = written;
out:
up(&inode->i_sem);
return err;