On Thu, Mar 14, 2019 at 08:56:28AM +0100, Andrea Righi wrote: > Parity page is incorrectly unmapped in finish_parity_scrub(), triggering > a reference counter bug on i386, i.e.: > > [ 157.662401] kernel BUG at mm/highmem.c:349! > [ 157.666725] invalid opcode: 0000 [#1] SMP PTI > > The reason is that kunmap(p_page) was completely left out, so we never > did an unmap for the p_page and the loop unmapping the rbio page was > iterating over the wrong number of stripes: unmapping should be done > with nr_data instead of rbio->real_stripes. > > Test case to reproduce the bug: > > - create a raid5 btrfs filesystem: > # mkfs.btrfs -m raid5 -d raid5 /dev/sdb /dev/sdc /dev/sdd /dev/sde > > - mount it: > # mount /dev/sdb /mnt > > - run btrfs scrub in a loop: > # while :; do btrfs scrub start -BR /mnt; done > > BugLink: https://bugs.launchpad.net/bugs/1812845 > Reviewed-by: Johannes Thumshirn <jthumshirn@xxxxxxx> > Signed-off-by: Andrea Righi <andrea.righi@xxxxxxxxxxxxx> Reviewed-by: David Sterba <dsterba@xxxxxxxx> Thanks.
