On Fri, Jun 02, 2017 at 01:33:19PM +0800, Eryu Guan wrote: > Hi all, > > I occasionally hit generic/344 and generic/346 failures when testing > 4.12-rc[1-3] kernels on ext4 DAX mount. > > FSTYP -- ext4 > PLATFORM -- Linux/x86_64 hp-xl420gen9-01 4.12.0-rc3 > MKFS_OPTIONS -- /dev/pmem2 > MOUNT_OPTIONS -- -o dax -o context=system_u:object_r:root_t:s0 /dev/pmem2 /mnt/testarea/scratch > > generic/344 1s ... 1s > generic/346 1s ... - output mismatch (see /var/lib/xfstests/results//generic/346.out.bad) > --- tests/generic/346.out 2017-05-24 10:13:38.592436565 -0400 > +++ /var/lib/xfstests/results//generic/346.out.bad 2017-06-01 12:46:50.122007818 -0400 > @@ -10,7 +10,8 @@ > INFO: sz = 1048576 > INFO: thread 0 created > INFO: thread 1 created > -INFO: 0 error(s) detected > +ERROR: thread 0, offset 000ff400, 00000000 != 7f1068063700 > +INFO: 1 error(s) detected > > INFO: ftruncate test... > INFO: sz = 1048576 > > And it seems generic/346 is easer to hit, usually it can be reproduced > within 20 iterations on 4.12-rc kernels. > > At first I thought it was a regression introduced in 4.12-rc1, but after > two failed bisects (pointed first bad to unrelated networking patch), I > enlarged the iteration count to 5000 and found that generic/346 failure > can also be seen on 4.11 and 4.10 kernel. I haven't tried other old > kernels yet. It's just much harder to hit on 4.10/4.11 kernels (need > hundreds of iterations). > > But the failure could only be reproduced with ext4 DAX mount, XFS DAX > mount survived 5000 runs of generic/346 on 4.12-rc3 kernel. > > I was testing with pmem device created by memmap kernel param > "memmap=10G!5G memmap=15G!15G", but it can be reproduced with brd > ramdisk too. > > If more info is needed please let me know. > > Thanks, > Eryu It turns out that this has already been fixed by Jan, with this commit: https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git/commit/?h=dev&id=4f8caa60a5a13a78f26198618f21774bd6aa6498 I have a test setup that was failing with this error very constantly within 100 iterations using v4.12-rc4. I was able to run 10,000+ iterations without issue with v4.12-rc4 + that one patch. That patch clearly isn't upstream yet, but I think it's headed for v4.12? (Ted, Jan?) It's marked for stable as well. It's currently in the ext4/dev tree: https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git/log/?h=dev - Ross
