btrfs-progs: lowmem check: Fix false alerts for image with shared block ref only backref
[BUG]
For image with shared block ref only metadata item like:
------
item 66 key (
21573632 METADATA_ITEM 0) itemoff 3971 itemsize 24
refs 66 gen 9 flags TREE_BLOCK|FULL_BACKREF
tree block skinny level 0
item 0 key (
21573632 SHARED_BLOCK_REF
21676032) itemoff 3995 itemsize 0
shared block backref
item 1 key (
21573632 SHARED_BLOCK_REF
21921792) itemoff 3995 itemsize 0
shared block backref
item 2 key (
21573632 SHARED_BLOCK_REF
21995520) itemoff 3995 itemsize 0
shared block backref
item 3 key (
21573632 SHARED_BLOCK_REF
22077440) itemoff 3995 itemsize 0
shared block backref
...
------
Lowmem mode check will report false alerts like:
------
ERROR: extent[
21573632 4096] backref lost (owner: 256, level: 0)
------
[CAUSE]
In fact, the false alerts are not even from extent tree verfication, but
a fs tree helper which is designed to make sure there is some tree block
referring to the fs tree block.
The idea is to find inlined tree backref then keyed TREE_BLOCK_REF_KEY.
However it missed SHARED_BLOCK_REF_KEY, and caused such false alert.
[FIX]
Add SHARED_BLOCK_REF_KEY to make the warning shut up.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>