Btrfs: bail out gracefully rather than BUG_ON

Btrfs: bail out gracefully rather than BUG_ON

[ Upstream commit 56a0e706fcf870270878d6d72b71092ae42d229c ]

If a file's DIR_ITEM key is invalid (due to memory errors) and gets
written to disk, a future lookup_path can end up with kernel panic due
to BUG_ON().

This gets rid of the BUG_ON(), meanwhile output the corrupted key and
return ENOENT if it's invalid.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reported-by: Guillaume Bouchard <bouchard@mercs-eng.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>