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fs: symlink write_begin allocation context fix 

With the write_begin/write_end aops, page_symlink was broken because it
could no longer pass a GFP_NOFS type mask into the point where the
allocations happened.  They are done in write_begin, which would always
assume that the filesystem can be entered from reclaim.  This bug could
cause filesystem deadlocks.

The funny thing with having a gfp_t mask there is that it doesn't really
allow the caller to arbitrarily tinker with the context in which it can be
called.  It couldn't ever be GFP_ATOMIC, for example, because it needs to
take the page lock.  The only thing any callers care about is __GFP_FS
anyway, so turn that into a single flag.

Add a new flag for write_begin, AOP_FLAG_NOFS.  Filesystems can now act on
this flag in their write_begin function.  Change __grab_cache_page to
accept a nofs argument as well, to honour that flag (while we're there,
change the name to grab_cache_page_write_begin which is more instructive
and does away with random leading underscores).

This is really a more flexible way to go in the end anyway -- if a
filesystem happens to want any extra allocations aside from the pagecache
ones in ints write_begin function, it may now use GFP_KERNEL (rather than
GFP_NOFS) for common case allocations (eg.  ocfs2_alloc_write_ctxt, for a
random example).

[kosaki.motohiro@jp.fujitsu.com: fix ubifs]
[kosaki.motohiro@jp.fujitsu.com: fix fuse]
Signed-off-by: Nick Piggin <npiggin@suse.de>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: <stable@kernel.org>		[2.6.28.x]
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
[ Cleaned up the calling convention: just pass in the AOP flags
  untouched to the grab_cache_page_write_begin() function.  That
  just simplifies everybody, and may even allow future expansion of the
  logic.   - Linus ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Nick Piggin 2009-01-04 12:00:53 -08:00 committed by Linus Torvalds
parent e687d691cb
commit 54566b2c15
22 changed files with 49 additions and 36 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
fs/affs/file.c
View File

@ -628,7 +628,7 @@ static int affs_write_begin_ofs(struct file *file, struct address_space *mapping
}
index = pos >> PAGE_CACHE_SHIFT;
page = __grab_cache_page(mapping, index);
page = grab_cache_page_write_begin(mapping, index, flags);
if (!page)
return -ENOMEM;
*pagep = page;

2
fs/afs/write.c
View File

@ -144,7 +144,7 @@ int afs_write_begin(struct file *file, struct address_space *mapping,
candidate->state = AFS_WBACK_PENDING;
init_waitqueue_head(&candidate->waitq);
page = __grab_cache_page(mapping, index);
page = grab_cache_page_write_begin(mapping, index, flags);
if (!page) {
kfree(candidate);
return -ENOMEM;

4
fs/buffer.c
View File

@ -1996,7 +1996,7 @@ int block_write_begin(struct file *file, struct address_space *mapping,
page = *pagep;
if (page == NULL) {
ownpage = 1;
page = __grab_cache_page(mapping, index);
page = grab_cache_page_write_begin(mapping, index, flags);
if (!page) {
status = -ENOMEM;
goto out;
@ -2502,7 +2502,7 @@ int nobh_write_begin(struct file *file, struct address_space *mapping,
from = pos & (PAGE_CACHE_SIZE - 1);
to = from + len;
page = __grab_cache_page(mapping, index);
page = grab_cache_page_write_begin(mapping, index, flags);
if (!page)
return -ENOMEM;
*pagep = page;

2
fs/cifs/file.c
View File

@ -2074,7 +2074,7 @@ static int cifs_write_begin(struct file *file, struct address_space *mapping,
cFYI(1, ("write_begin from %lld len %d", (long long)pos, len));
page = __grab_cache_page(mapping, index);
page = grab_cache_page_write_begin(mapping, index, flags);
if (!page) {
rc = -ENOMEM;
goto out;

2
fs/ecryptfs/mmap.c
View File

@ -288,7 +288,7 @@ static int ecryptfs_write_begin(struct file *file,
loff_t prev_page_end_size;
int rc = 0;
page = __grab_cache_page(mapping, index);
page = grab_cache_page_write_begin(mapping, index, flags);
if (!page)
return -ENOMEM;
*pagep = page;

2
fs/ext3/inode.c
View File

@ -1161,7 +1161,7 @@ static int ext3_write_begin(struct file *file, struct address_space *mapping,
to = from + len;
retry:
page = __grab_cache_page(mapping, index);
page = grab_cache_page_write_begin(mapping, index, flags);
if (!page)
return -ENOMEM;
*pagep = page;

3
fs/ext3/namei.c
View File

@ -2175,8 +2175,7 @@ static int ext3_symlink (struct inode * dir,
* We have a transaction open. All is sweetness. It also sets
* i_size in generic_commit_write().
*/
err = __page_symlink(inode, symname, l,
mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS);
err = __page_symlink(inode, symname, l, 1);
if (err) {
drop_nlink(inode);
unlock_new_inode(inode);

4
fs/ext4/inode.c
View File

@ -1346,7 +1346,7 @@ static int ext4_write_begin(struct file *file, struct address_space *mapping,
goto out;
}
page = __grab_cache_page(mapping, index);
page = grab_cache_page_write_begin(mapping, index, flags);
if (!page) {
ext4_journal_stop(handle);
ret = -ENOMEM;
@ -2550,7 +2550,7 @@ static int ext4_da_write_begin(struct file *file, struct address_space *mapping,
goto out;
}
page = __grab_cache_page(mapping, index);
page = grab_cache_page_write_begin(mapping, index, flags);
if (!page) {
ext4_journal_stop(handle);
ret = -ENOMEM;

3
fs/ext4/namei.c
View File

@ -2212,8 +2212,7 @@ static int ext4_symlink(struct inode *dir,
* We have a transaction open. All is sweetness. It also sets
* i_size in generic_commit_write().
*/
err = __page_symlink(inode, symname, l,
mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS);
err = __page_symlink(inode, symname, l, 1);
if (err) {
clear_nlink(inode);
unlock_new_inode(inode);

4
fs/fuse/file.c
View File

@ -646,7 +646,7 @@ static int fuse_write_begin(struct file *file, struct address_space *mapping,
{
pgoff_t index = pos >> PAGE_CACHE_SHIFT;
*pagep = __grab_cache_page(mapping, index);
*pagep = grab_cache_page_write_begin(mapping, index, flags);
if (!*pagep)
return -ENOMEM;
return 0;
@ -779,7 +779,7 @@ static ssize_t fuse_fill_write_pages(struct fuse_req *req,
break;
err = -ENOMEM;
page = __grab_cache_page(mapping, index);
page = grab_cache_page_write_begin(mapping, index, 0);
if (!page)
break;

2
fs/gfs2/ops_address.c
View File

@ -675,7 +675,7 @@ static int gfs2_write_begin(struct file *file, struct address_space *mapping,
goto out_trans_fail;
error = -ENOMEM;
page = __grab_cache_page(mapping, index);
page = grab_cache_page_write_begin(mapping, index, flags);
*pagep = page;
if (unlikely(!page))
goto out_endtrans;

2
fs/hostfs/hostfs_kern.c
View File

@ -501,7 +501,7 @@ int hostfs_write_begin(struct file *file, struct address_space *mapping,
{
pgoff_t index = pos >> PAGE_CACHE_SHIFT;
*pagep = __grab_cache_page(mapping, index);
*pagep = grab_cache_page_write_begin(mapping, index, flags);
if (!*pagep)
return -ENOMEM;
return 0;

2
fs/jffs2/file.c
View File

@ -132,7 +132,7 @@ static int jffs2_write_begin(struct file *filp, struct address_space *mapping,
uint32_t pageofs = index << PAGE_CACHE_SHIFT;
int ret = 0;
pg = __grab_cache_page(mapping, index);
pg = grab_cache_page_write_begin(mapping, index, flags);
if (!pg)
return -ENOMEM;
*pagep = pg;

2
fs/libfs.c
View File

@ -360,7 +360,7 @@ int simple_write_begin(struct file *file, struct address_space *mapping,
index = pos >> PAGE_CACHE_SHIFT;
from = pos & (PAGE_CACHE_SIZE - 1);
page = __grab_cache_page(mapping, index);
page = grab_cache_page_write_begin(mapping, index, flags);
if (!page)
return -ENOMEM;

13
fs/namei.c
View File

@ -2817,18 +2817,23 @@ void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
}
}
int __page_symlink(struct inode *inode, const char *symname, int len,
gfp_t gfp_mask)
/*
* The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
*/
int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
{
struct address_space *mapping = inode->i_mapping;
struct page *page;
void *fsdata;
int err;
char *kaddr;
unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
if (nofs)
flags |= AOP_FLAG_NOFS;
retry:
err = pagecache_write_begin(NULL, mapping, 0, len-1,
AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
flags, &page, &fsdata);
if (err)
goto fail;
@ -2852,7 +2857,7 @@ int __page_symlink(struct inode *inode, const char *symname, int len,
int page_symlink(struct inode *inode, const char *symname, int len)
{
return __page_symlink(inode, symname, len,
mapping_gfp_mask(inode->i_mapping));
!(mapping_gfp_mask(inode->i_mapping) & __GFP_FS));
}
const struct inode_operations page_symlink_inode_operations = {

2
fs/nfs/file.c
View File

@ -354,7 +354,7 @@ static int nfs_write_begin(struct file *file, struct address_space *mapping,
file->f_path.dentry->d_name.name,
mapping->host->i_ino, len, (long long) pos);
page = __grab_cache_page(mapping, index);
page = grab_cache_page_write_begin(mapping, index, flags);
if (!page)
return -ENOMEM;
*pagep = page;

2
fs/reiserfs/inode.c
View File

@ -2561,7 +2561,7 @@ static int reiserfs_write_begin(struct file *file,
}
index = pos >> PAGE_CACHE_SHIFT;
page = __grab_cache_page(mapping, index);
page = grab_cache_page_write_begin(mapping, index, flags);
if (!page)
return -ENOMEM;
*pagep = page;

2
fs/smbfs/file.c
View File

@ -297,7 +297,7 @@ static int smb_write_begin(struct file *file, struct address_space *mapping,
struct page **pagep, void **fsdata)
{
pgoff_t index = pos >> PAGE_CACHE_SHIFT;
*pagep = __grab_cache_page(mapping, index);
*pagep = grab_cache_page_write_begin(mapping, index, flags);
if (!*pagep)
return -ENOMEM;
return 0;

9
fs/ubifs/file.c
View File

@ -219,7 +219,8 @@ static void release_existing_page_budget(struct ubifs_info *c)
}
static int write_begin_slow(struct address_space *mapping,
loff_t pos, unsigned len, struct page **pagep)
loff_t pos, unsigned len, struct page **pagep,
unsigned flags)
{
struct inode *inode = mapping->host;
struct ubifs_info *c = inode->i_sb->s_fs_info;
@ -247,7 +248,7 @@ static int write_begin_slow(struct address_space *mapping,
if (unlikely(err))
return err;
page = __grab_cache_page(mapping, index);
page = grab_cache_page_write_begin(mapping, index, flags);
if (unlikely(!page)) {
ubifs_release_budget(c, &req);
return -ENOMEM;
@ -438,7 +439,7 @@ static int ubifs_write_begin(struct file *file, struct address_space *mapping,
return -EROFS;
/* Try out the fast-path part first */
page = __grab_cache_page(mapping, index);
page = grab_cache_page_write_begin(mapping, index, flags);
if (unlikely(!page))
return -ENOMEM;
@ -483,7 +484,7 @@ static int ubifs_write_begin(struct file *file, struct address_space *mapping,
unlock_page(page);
page_cache_release(page);
return write_begin_slow(mapping, pos, len, pagep);
return write_begin_slow(mapping, pos, len, pagep, flags);
}
/*

5
include/linux/fs.h
View File

@ -423,6 +423,9 @@ enum positive_aop_returns {
#define AOP_FLAG_UNINTERRUPTIBLE 0x0001 /* will not do a short write */
#define AOP_FLAG_CONT_EXPAND 0x0002 /* called from cont_expand */
#define AOP_FLAG_NOFS 0x0004 /* used by filesystem to direct
* helper code (eg buffer layer)
* to clear GFP_FS from alloc */
/*
* oh the beauties of C type declarations.
@ -2035,7 +2038,7 @@ extern int page_readlink(struct dentry *, char __user *, int);
extern void *page_follow_link_light(struct dentry *, struct nameidata *);
extern void page_put_link(struct dentry *, struct nameidata *, void *);
extern int __page_symlink(struct inode *inode, const char *symname, int len,
gfp_t gfp_mask);
int nofs);
extern int page_symlink(struct inode *inode, const char *symname, int len);
extern const struct inode_operations page_symlink_inode_operations;
extern int generic_readlink(struct dentry *, char __user *, int);

3
include/linux/pagemap.h
View File

@ -241,7 +241,8 @@ unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t start,
unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
int tag, unsigned int nr_pages, struct page **pages);
struct page *__grab_cache_page(struct address_space *mapping, pgoff_t index);
struct page *grab_cache_page_write_begin(struct address_space *mapping,
pgoff_t index, unsigned flags);
/*
* Returns locked page at given index in given cache, creating it if needed.

13
mm/filemap.c
View File

@ -2140,19 +2140,24 @@ EXPORT_SYMBOL(generic_file_direct_write);
* Find or create a page at the given pagecache position. Return the locked
* page. This function is specifically for buffered writes.
*/
struct page *__grab_cache_page(struct address_space *mapping, pgoff_t index)
struct page *grab_cache_page_write_begin(struct address_space *mapping,
pgoff_t index, unsigned flags)
{
int status;
struct page *page;
gfp_t gfp_notmask = 0;
if (flags & AOP_FLAG_NOFS)
gfp_notmask = __GFP_FS;
repeat:
page = find_lock_page(mapping, index);
if (likely(page))
return page;
page = page_cache_alloc(mapping);
page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask);
if (!page)
return NULL;
status = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL);
status = add_to_page_cache_lru(page, mapping, index,
GFP_KERNEL & ~gfp_notmask);
if (unlikely(status)) {
page_cache_release(page);
if (status == -EEXIST)
@ -2161,7 +2166,7 @@ struct page *__grab_cache_page(struct address_space *mapping, pgoff_t index)
}
return page;
}
EXPORT_SYMBOL(__grab_cache_page);
EXPORT_SYMBOL(grab_cache_page_write_begin);
static ssize_t generic_perform_write(struct file *file,
struct iov_iter *i, loff_t pos)