On Mon, Apr 09 2018 at 11:51am -0400, Mike Snitzer <snitzer@xxxxxxxxxx> wrote: > On Sun, Apr 08 2018 at 12:00am -0400, > Ming Lei <ming.lei@xxxxxxxxxx> wrote: > > > Hi, > > > > The following kernel oops(divide error) is triggered when running > > xfstest(generic/347) on ext4. > > > > [ 442.632954] run fstests generic/347 at 2018-04-07 18:06:44 > > [ 443.839480] divide error: 0000 [#1] PREEMPT SMP PTI > > [ 443.840201] Dumping ftrace buffer: > > [ 443.840692] (ftrace buffer empty) ... > > [ 443.845756] CPU: 1 PID: 29607 Comm: dmsetup Not tainted 4.16.0_f605ba97fb80_master+ #1 > > [ 443.846968] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.10.2-2.fc27 04/01/2014 > > [ 443.848147] RIP: 0010:pool_io_hints+0x77/0x153 [dm_thin_pool] ... > I was able to reproduce (in my case RIP was pool_io_hints+0x45) > > Which on my kernel, is: > > crash> dis -l pool_io_hints+0x45 > /root/snitm/git/linux/drivers/md/dm-thin.c: 2748 > 0xffffffffc0765165 <pool_io_hints+69>: div %rdi > > Which is drivers/md/dm-thin.c:is_factor()'s return > !sector_div(block_size, n); > > SO looking at pool_io_hints() it would seem limits->max_sectors is 0 for > this xfstests device... why would that be!? > > Clearly pool_io_hints() could stand to be more defensive with a > !limits->max_sectors negative check but is it ever really valid for > max_sectors to be 0? > > Pretty sure the ultimate bug is outside DM (but not seeing an obvious > place where block core would set max_sectors to 0, all blk-settings.c > uses min_not_zero(), etc). I successfully ran this test against the linux-dm.git "for-4.17/dm-changes" tag that Linus merged after the block changes: git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git tags/for-4.17/dm-changes # ./check tests/generic/347 FSTYP -- ext4 PLATFORM -- Linux/x86_64 thegoat 4.16.0-rc5.snitm MKFS_OPTIONS -- /dev/mapper/test-xfstests_scratch MOUNT_OPTIONS -- -o acl,user_xattr /dev/mapper/test-xfstests_scratch /scratch generic/347 65s Ran: generic/347 Passed all 1 tests SO this would seem to implicate some regression in the 4.17 block layer changes.
