This test case simulates the racy situation of buffered write vs dio
read, and see if btrfs_get_extent() would return -EEXIST.
Signed-off-by: NLiu Bo <bo.li.liu@oracle.com>
Reviewed-by: NJosef Bacik <jbacik@fb.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>