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Subject[patch 68/85] fs: symlink write_begin allocation context fix
2.6.27-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Nick Piggin <npiggin@suse.de>

commit 54566b2c1594c2326a645a3551f9d989f7ba3c5e upstream.

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>
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
fs/affs/file.c | 2 +-
fs/buffer.c | 4 ++--
fs/ext3/inode.c | 2 +-
fs/ext3/namei.c | 3 +--
fs/ext4/inode.c | 4 ++--
fs/ext4/namei.c | 3 +--
fs/fuse/file.c | 4 ++--
fs/gfs2/ops_address.c | 2 +-
fs/hostfs/hostfs_kern.c | 2 +-
fs/jffs2/file.c | 2 +-
fs/libfs.c | 2 +-
fs/namei.c | 13 +++++++++----
fs/nfs/file.c | 2 +-
fs/reiserfs/inode.c | 2 +-
fs/smbfs/file.c | 2 +-
fs/ubifs/file.c | 9 +++++----
include/linux/fs.h | 5 ++++-
include/linux/pagemap.h | 3 ++-
mm/filemap.c | 17 +++++++++++------
19 files changed, 48 insertions(+), 35 deletions(-)

--- a/fs/affs/file.c
+++ b/fs/affs/file.c
@@ -628,7 +628,7 @@ static int affs_write_begin_ofs(struct f
}

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;
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1988,7 +1988,7 @@ int block_write_begin(struct file *file,
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;
@@ -2494,7 +2494,7 @@ int nobh_write_begin(struct file *file,
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;
--- a/fs/ext3/inode.c
+++ b/fs/ext3/inode.c
@@ -1152,7 +1152,7 @@ static int ext3_write_begin(struct file
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;
--- a/fs/ext3/namei.c
+++ b/fs/ext3/namei.c
@@ -2187,8 +2187,7 @@ retry:
* 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);
ext3_mark_inode_dirty(handle, inode);
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1370,7 +1370,7 @@ retry:
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;
@@ -2421,7 +2421,7 @@ retry:
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;
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -2216,8 +2216,7 @@ retry:
* 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);
ext4_mark_inode_dirty(handle, inode);
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -644,7 +644,7 @@ static int fuse_write_begin(struct file
{
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;
@@ -777,7 +777,7 @@ static ssize_t fuse_fill_write_pages(str
break;

err = -ENOMEM;
- page = __grab_cache_page(mapping, index);
+ page = grab_cache_page_write_begin(mapping, index, 0);
if (!page)
break;

--- a/fs/gfs2/ops_address.c
+++ b/fs/gfs2/ops_address.c
@@ -675,7 +675,7 @@ static int gfs2_write_begin(struct file
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;
--- a/fs/hostfs/hostfs_kern.c
+++ b/fs/hostfs/hostfs_kern.c
@@ -500,7 +500,7 @@ int hostfs_write_begin(struct file *file
{
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;
--- a/fs/jffs2/file.c
+++ b/fs/jffs2/file.c
@@ -132,7 +132,7 @@ static int jffs2_write_begin(struct file
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;
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -360,7 +360,7 @@ int simple_write_begin(struct file *file
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;

--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2796,18 +2796,23 @@ void page_put_link(struct dentry *dentry
}
}

-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;

@@ -2831,7 +2836,7 @@ fail:
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 = {
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -351,7 +351,7 @@ static int nfs_write_begin(struct file *
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;
--- a/fs/reiserfs/inode.c
+++ b/fs/reiserfs/inode.c
@@ -2565,7 +2565,7 @@ static int reiserfs_write_begin(struct f
}

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;
--- a/fs/smbfs/file.c
+++ b/fs/smbfs/file.c
@@ -297,7 +297,7 @@ static int smb_write_begin(struct file *
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;
--- a/fs/ubifs/file.c
+++ b/fs/ubifs/file.c
@@ -213,7 +213,8 @@ static void release_existing_page_budget
}

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;
@@ -241,7 +242,7 @@ static int write_begin_slow(struct addre
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;
@@ -432,7 +433,7 @@ static int ubifs_write_begin(struct file
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;

@@ -477,7 +478,7 @@ static int ubifs_write_begin(struct file
unlock_page(page);
page_cache_release(page);

- return write_begin_slow(mapping, pos, len, pagep);
+ return write_begin_slow(mapping, pos, len, pagep, flags);
}

/*
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -403,6 +403,9 @@ 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.
@@ -1959,7 +1962,7 @@ extern int page_readlink(struct dentry *
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);
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -213,7 +213,8 @@ unsigned find_get_pages_contig(struct ad
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.
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2033,7 +2033,7 @@ int pagecache_write_begin(struct file *f
struct inode *inode = mapping->host;
struct page *page;
again:
- page = __grab_cache_page(mapping, index);
+ page = grab_cache_page_write_begin(mapping, index, flags);
*pagep = page;
if (!page)
return -ENOMEM;
@@ -2197,19 +2197,24 @@ 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)
@@ -2218,7 +2223,7 @@ repeat:
}
return page;
}
-EXPORT_SYMBOL(__grab_cache_page);
+EXPORT_SYMBOL(grab_cache_page_write_begin);

static ssize_t generic_perform_write_2copy(struct file *file,
struct iov_iter *i, loff_t pos)
@@ -2263,7 +2268,7 @@ static ssize_t generic_perform_write_2co
break;
}

- page = __grab_cache_page(mapping, index);
+ page = grab_cache_page_write_begin(mapping, index, GFP_KERNEL);
if (!page) {
status = -ENOMEM;
break;


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