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>
Cc: <linux-ext4@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/fs/mbcache.c b/fs/mbcache.c
index eb31b73e7d69..ec88ff3d04a9 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);