Btrfs: fix memory leak of empty filesystem after balance

After Josef's patch(commit 3c14874acc71180553fb5aba528e3cf57c5b958b),
btrfs will exclude super bytes when reading block groups(by marking a extent
state UPTODATE).  However, these bytes do not get freed while balance remove
unused block groups, and we won't process those removed ones any more, when
we do umount and unload the btrfs module,  btrfs hits a memory leak.

This patch add the missing free operation.

Reproduce steps:
$ mkfs.btrfs disk
$ mount disk /mnt/btrfs -o loop
$ btrfs filesystem balance /mnt/btrfs
$ umount /mnt/btrfs
$ rmmod btrfs

Signed-off-by: Liu Bo <liubo2009@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index cd0b69f57375a30eedda3ffd05ac44cf59660030..a561060f5ffb958667d02748220c1d3b7c946b67 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -8669,6 +8669,12 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
        BUG_ON(!block_group);
        BUG_ON(!block_group->ro);
 
+       /*
+        * Free the reserved super bytes from this block group before
+        * remove it.
+        */
+       free_excluded_extents(root, block_group);
+
        memcpy(&key, &block_group->key, sizeof(key));
        if (block_group->flags & (BTRFS_BLOCK_GROUP_DUP |
                                  BTRFS_BLOCK_GROUP_RAID1 |