btrfs-progs: fsck-test: Introduce test case for false data extent backref lost

Introduce a new test image, which has an extent item with no inlined
extent data ref, but all keyed extent data ref.

Only in this case we can trigger fase data extent backref lost bug in
lowmem mode.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/tests/fsck-tests/020-extent-ref-cases/keyed_data_ref_only.img b/tests/fsck-tests/020-extent-ref-cases/keyed_data_ref_only.img
new file mode 100644 (file)
index 0000000..668589f
Binary files /dev/null and b/tests/fsck-tests/020-extent-ref-cases/keyed_data_ref_only.img differ