btrfs-progs: check: check extent_inline_ref in lowmem

btrfs-progs: check: check extent_inline_ref in lowmem

Lowmem check does not skip invalid type in extent_inline_ref and then
calls btrfs_extent_inline_ref_size(type) which causes a crash.

Error:

$ btrfs check --mode=lowmem  /tmp/data_small
Checking filesystem on /tmp/data_small
UUID: ee205d69-8724-4aa2-a4f5-bc8558a62169
checking extents
ERROR: extent[20971520 16384] backref type mismatch, missing bit: 2
ERROR: extent[20971520 16384] backref generation mismatch,
wanted: 7, have: 0
ERROR: extent[20971520 16384] is referred by other roots than 3
ctree.h:1754: btrfs_extent_inline_ref_size: BUG_ON `1` triggered,
value 1
btrfs(+0x543db)[0x55fabc2ab3db]
btrfs(+0x587f7)[0x55fabc2af7f7]
btrfs(+0x5fa44)[0x55fabc2b6a44]
btrfs(cmd_check+0x194a)[0x55fabc2bd717]
btrfs(main+0x88)[0x55fabc2682e0]
/usr/lib/libc.so.6(__libc_start_main+0xea)[0x7f021c3824ca]
btrfs(_start+0x2a)[0x55fabc267e7a]
[1] 5188 abort (core dumped)  btrfs check --mode=lowmem /tmp/data_small

Fix it by introducing check_extent_inline_ref() to check the type.
If the checker returns a non-zero value, we should not try to check the
corrupted extent item anymore.

Suggested-by: Qu Wenruo <quwenruo.btrfs@gmx.com>
Signed-off-by: Su Yue <suy.fnst@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>