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Subject[PATCH] vfs: Fix possible deadlock in ext2, ext3, ext4 when using xattrs
mb_cache_entry_alloc() was allocating cache entries with GFP_KERNEL. But filesystems
are calling this function while holding xattr_sem so possible recursion into the fs
violates locking ordering of xattr_sem and transaction start / i_mutex for ext2-4.
Change mb_cache_entry_alloc() so that filesystems can specify desired gfp mask and
use GFP_NOFS from all of them.

Signed-off-by: Jan Kara <jack@suse.cz>
Reported-by: Dave Jones <davej@redhat.com>
---
I've bundled changes for ext2-4 together because they are oneliners and
not likely to conflict with anything and a partial change would make other
filesystems not compilable...

fs/ext2/xattr.c | 2 +-
fs/ext3/xattr.c | 2 +-
fs/ext4/xattr.c | 2 +-
fs/mbcache.c | 4 ++--
include/linux/mbcache.h | 2 +-
5 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/fs/ext2/xattr.c b/fs/ext2/xattr.c
index 3e8683d..a99d46f 100644
--- a/fs/ext2/xattr.c
+++ b/fs/ext2/xattr.c
@@ -835,7 +835,7 @@ ext2_xattr_cache_insert(struct buffer_head *bh)
struct mb_cache_entry *ce;
int error;

- ce = mb_cache_entry_alloc(ext2_xattr_cache);
+ ce = mb_cache_entry_alloc(ext2_xattr_cache, GFP_NOFS);
if (!ce)
return -ENOMEM;
error = mb_cache_entry_insert(ce, bh->b_bdev, bh->b_blocknr, &hash);
diff --git a/fs/ext3/xattr.c b/fs/ext3/xattr.c
index a6ea4d6..4285654 100644
--- a/fs/ext3/xattr.c
+++ b/fs/ext3/xattr.c
@@ -1126,7 +1126,7 @@ ext3_xattr_cache_insert(struct buffer_head *bh)
struct mb_cache_entry *ce;
int error;

- ce = mb_cache_entry_alloc(ext3_xattr_cache);
+ ce = mb_cache_entry_alloc(ext3_xattr_cache, GFP_NOFS);
if (!ce) {
ea_bdebug(bh, "out of memory");
return;
diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index d796213..e9054c1 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -1386,7 +1386,7 @@ ext4_xattr_cache_insert(struct buffer_head *bh)
struct mb_cache_entry *ce;
int error;

- ce = mb_cache_entry_alloc(ext4_xattr_cache);
+ ce = mb_cache_entry_alloc(ext4_xattr_cache, GFP_NOFS);
if (!ce) {
ea_bdebug(bh, "out of memory");
return;
diff --git a/fs/mbcache.c b/fs/mbcache.c
index eb31b73..ec88ff3 100644
--- a/fs/mbcache.c
+++ b/fs/mbcache.c
@@ -399,11 +399,11 @@ mb_cache_destroy(struct mb_cache *cache)
* if no more memory was available.
*/
struct mb_cache_entry *
-mb_cache_entry_alloc(struct mb_cache *cache)
+mb_cache_entry_alloc(struct mb_cache *cache, gfp_t gfp_flags)
{
struct mb_cache_entry *ce;

- ce = kmem_cache_alloc(cache->c_entry_cache, GFP_KERNEL);
+ ce = kmem_cache_alloc(cache->c_entry_cache, gfp_flags);
if (ce) {
atomic_inc(&cache->c_entry_count);
INIT_LIST_HEAD(&ce->e_lru_list);
diff --git a/include/linux/mbcache.h b/include/linux/mbcache.h
index 99e044b..a09b84e 100644
--- a/include/linux/mbcache.h
+++ b/include/linux/mbcache.h
@@ -34,7 +34,7 @@ void mb_cache_destroy(struct mb_cache *);

/* Functions on cache entries */

-struct mb_cache_entry *mb_cache_entry_alloc(struct mb_cache *);
+struct mb_cache_entry *mb_cache_entry_alloc(struct mb_cache *, gfp_t);
int mb_cache_entry_insert(struct mb_cache_entry *, struct block_device *,
sector_t, unsigned int[]);
void mb_cache_entry_release(struct mb_cache_entry *);
--
1.5.2.4


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