Obviously, csum_type and incompat_flags get some garbage, but its csum
still matches, which means kernel calculates the csum based on corrupted
super block memory.
And after manually fixing these values, the filesystem is completely
healthy without any problem exposed by btrfs check.
Although the cause is still unknown, at least detect it and prevent further
corruption.
Both reports have same symptoms, there's an overwrite on offset 192 of
the superblock, by 4 bytes. The superblock structure is not allocated or
freed and stays in the memory for the whole filesystem lifetime, so it's
not a use-after-free kind of error on someone else's leaked page.
As a vague point for the problable cause is mentioning of other system
freezing related to graphic card drivers.
Reported-by: Ken Swenson <flat@imo.uto.moe> Reported-by: Ben Parsons <9parsonsb@gmail.com> Signed-off-by: Qu Wenruo <wqu@suse.com> Reviewed-by: David Sterba <dsterba@suse.com>
[ add brief analysis of the reports ] Signed-off-by: David Sterba <dsterba@suse.com>