On Fri, Sep 25, 2020 at 09:47:43AM -0700, Shakeel Butt wrote:

On Fri, Sep 25, 2020 at 9:32 AM Shakeel Butt [off-list ref] wrote:

quoted

On Fri, Sep 25, 2020 at 9:19 AM Ming Lei [off-list ref] wrote:

quoted

On Fri, Sep 25, 2020 at 03:31:45PM +0800, Ming Lei wrote:

quoted

On Thu, Sep 24, 2020 at 09:13:11PM -0400, Theodore Y. Ts'o wrote:

quoted

On Thu, Sep 24, 2020 at 10:33:45AM -0400, Theodore Y. Ts'o wrote:

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HOWEVER, thanks to a hint from a colleague at $WORK, and realizing
that one of the stack traces had virtio balloon in the trace, I
realized that when I switched the GCE VM type from e1-standard-2 to
n1-standard-2 (where e1 VM's are cheaper because they use
virtio-balloon to better manage host OS memory utilization), problem
has become, much, *much* rarer (and possibly has gone away, although
I'm going to want to run a lot more tests before I say that
conclusively) on my test setup.  At the very least, using an n1 VM
(which doesn't have virtio-balloon enabled in the hypervisor) is
enough to unblock ext4 development.

.... and I spoke too soon.  A number of runs using -rc6 are now
failing even with the n1-standard-2 VM, so virtio-ballon may not be an
indicator.

This is why debugging this is frustrating; it is very much a heisenbug

--- although 5.8 seems to work completely reliably, as does commits

before 37f4a24c2469.  Anything after that point will show random
failures.  :-(

It does not make sense to mention 37f4a24c2469, which is reverted in
4e2f62e566b5. Later the patch in 37f4a24c2469 is fixed and re-commited
as 568f27006577.

However, I can _not_ reproduce the issue by running the same test on
kernel built from 568f27006577 directly.

Also you have confirmed that the issue can't be fixed after reverting
568f27006577 against v5.9-rc4.

Looks the real issue(slab list corruption) should be introduced between
568f27006577 and v5.9-rc4.

git bisect shows the first bad commit:

        [10befea91b61c4e2c2d1df06a2e978d182fcf792] mm: memcg/slab: use a single set of
                kmem_caches for all allocations

And I have double checked that the above commit is really the first bad
commit for the list corruption issue of 'list_del corruption, ffffe1c241b00408->next
is LIST_POISON1 (dead000000000100)', see the detailed stack trace and
kernel oops log in the following link:

        https://lore.kernel.org/lkml/20200916202026.GC38283@mit.edu/ (local)

The failure signature is similar to
https://lore.kernel.org/lkml/20200901075321.GL4299@shao2-debian/ (local)

quoted

And the kernel config is the one(without KASAN) used by Theodore in GCE VM, see
the following link:

        https://lore.kernel.org/lkml/20200917143012.GF38283@mit.edu/ (local)

The reproducer is xfstests generic/038. In my setting, test device is virtio-scsi, and
scratch device is virtio-blk.

Is it possible to check SLUB as well to confirm that the issue is only
happening on SLAB?

Can you also, please, check if passing cgroup.memory=nokmem as a boot argument
is fixing the issue?

Thanks!