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>

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index deba54f6cbed2af2d504224d2910829951e98d1c..c962d0690505b8a8202b293e31caaf984ce6aabc 100644 (file)
--- 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)