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>

5 files changed, 6 insertions, 6 deletions

diff --git a/fs/ext2/xattr.c b/fs/ext2/xattr.c
index 3e8683dbb13f..a99d46f3b26e 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 a6ea4d6a8bb2..42856541e9a5 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 d7962139c010..e9054c1c7d93 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 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);
diff --git a/include/linux/mbcache.h b/include/linux/mbcache.h
index 99e044b4efc6..a09b84e4fdb4 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 *);