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=12672Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

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);
+		}
+	}
+	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.
+		 * doesn't grow big.  We need to release
+		 * alloc_semp before calling ext4_mb_add_n_trim()
 		 */
-			if (likely(pa->pa_free)) {
+		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->alloc_semp)
-		up_read(ac->alloc_semp);
 	if (ac->ac_bitmap_page)
 		page_cache_release(ac->ac_bitmap_page);
 	if (ac->ac_buddy_page)