ext4: Fix lockdep warning

We should not call ext4_mb_add_n_trim while holding alloc_semp.

    =============================================
    [ INFO: possible recursive locking detected ]
    2.6.29-rc4-git1-dirty #124
    ---------------------------------------------
    ffsb/3116 is trying to acquire lock:
     (&meta_group_info[i]->alloc_sem){----}, at: [<ffffffff8035a6e8>]
     ext4_mb_load_buddy+0xd2/0x343

    but task is already holding lock:
     (&meta_group_info[i]->alloc_sem){----}, at: [<ffffffff8035a6e8>]
     ext4_mb_load_buddy+0xd2/0x343

http://bugzilla.kernel.org/show_bug.cgi?id=12672

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 16 insertions, 13 deletions

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index deba54f6cbed..c962d0690505 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4476,23 +4476,26 @@ static int ext4_mb_release_context(struct ext4_allocation_context *ac)
                         pa->pa_free -= ac->ac_b_ex.fe_len;
                         pa->pa_len -= ac->ac_b_ex.fe_len;
                         spin_unlock(&pa->pa_lock);
-                        /*
-                         * We want to add the pa to the right bucket.
-                         * Remove it from the list and while adding
-                         * make sure the list to which we are adding
-                         * doesn't grow big.
-                         */
-                        if (likely(pa->pa_free)) {
-                                spin_lock(pa->pa_obj_lock);
-                                list_del_rcu(&pa->pa_inode_list);
-                                spin_unlock(pa->pa_obj_lock);
-                                ext4_mb_add_n_trim(ac);
-                        }
                 }
-                ext4_mb_put_pa(ac, ac->ac_sb, pa);
         }
         if (ac->alloc_semp)
                 up_read(ac->alloc_semp);
+        if (pa) {
+                /*
+                 * We want to add the pa to the right bucket.
+                 * Remove it from the list and while adding
+                 * make sure the list to which we are adding
+                 * doesn't grow big.  We need to release
+                 * alloc_semp before calling ext4_mb_add_n_trim()
+                 */
+                if (pa->pa_linear && likely(pa->pa_free)) {
+                        spin_lock(pa->pa_obj_lock);
+                        list_del_rcu(&pa->pa_inode_list);
+                        spin_unlock(pa->pa_obj_lock);
+                        ext4_mb_add_n_trim(ac);
+                }
+                ext4_mb_put_pa(ac, ac->ac_sb, pa);
+        }
         if (ac->ac_bitmap_page)
                 page_cache_release(ac->ac_bitmap_page);
         if (ac->ac_buddy_page)