On 4/9/18 12:38 PM, Mike Snitzer wrote: > 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. No immediate ideas come to mind, we didn't have a lot of changes and I don't see anything that looks problematic. Maybe you can try and bisect it and see what you come up with? -- Jens Axboe
