btrfs-progs: fsck-tests: Introduce test case with keyed data backref with shared tree blocks

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For snapshot shared tree blocks with source subvolume, the keyed backref
counter only counts the exclusive owned references.

In the following case, 258 is a snapshot of 257, which inherits all the
reference to this data extent.
------
        item 4 key (12582912 EXTENT_ITEM 524288) itemoff 3741 itemsize 140
                refs 179 gen 9 flags DATA
                extent data backref root 257 objectid 258 offset 0 count 49
                extent data backref root 257 objectid 257 offset 0 count 1
                extent data backref root 256 objectid 258 offset 0 count 128
                extent data backref root 256 objectid 257 offset 0 count 1
------

However lowmem mode used to iterate the whole inode to find all
references, and doesn't care if a reference is already counted by the
shared tree block.

Add the test case to check it.

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

master

Qu Wenruo 2017-11-22 17:03:25 +08:00 committed by David Sterba

parent ee147df75f

commit 263184c7d2

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