btrfs-progs: check: lowmem, fix false alert about backref lost for SHARED_DATA_REF
In check_extent_data_item(), after checking extent item of one data
extent, we search inlined data backref, then EXTENT_DATA_REF_KEY.
But we didn't search SHARED_DATA_REF, so if the backref is
SHARED_DATA_REF, then we will raise a false alert about backref lost.
Fix by also checking SHARED_DATA_REF_KEY in check_extent_data_item().
Reported-by: Chris Murphy <chris@colorremedies.com>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>