7cbc45dd927cf1220ff2dfc8f4e15dd17
parent e18e4809b10e6c9efb5fe10c1ddcb4ebb690d517
author Yan <yanzheng@21cn.com> 1201024016 -0500
committer Chris Mason <chris.mason@oracle.com> 1222355039 -0400

Fix for btrfs_find_free_objectid

btrfs_find_free_objectid may return a used objectid due to arithmetic
underflow. This bug may happen when parameter 'root' is tree root,  so
it may cause serious problems when creating snapshot or sub-volume.

Signed-off-by: Chris Mason <chris.mason@oracle.com>