linux-ext4 - Re: REGRESSION: 37f4a24c2469: blk-mq: centralise related handling into blk_mq_get_driver

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Date:   Fri, 18 Sep 2020 07:08:42 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     "Theodore Y. Ts'o" <tytso@....edu>
Cc:     Jens Axboe <axboe@...nel.dk>, linux-ext4@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-block@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: REGRESSION: 37f4a24c2469: blk-mq: centralise related handling
 into blk_mq_get_driver_tag

On Thu, Sep 17, 2020 at 10:30:12AM -0400, Theodore Y. Ts'o wrote:
> On Thu, Sep 17, 2020 at 10:20:51AM +0800, Ming Lei wrote:
> > 
> > Obviously there is other more serious issue, since 568f27006577 is
> > completely reverted in your test, and you still see list corruption
> > issue.
> > 
> > So I'd suggest to find the big issue first. Once it is fixed, maybe
> > everything becomes fine.
> > ...
> > Looks it is more like a memory corruption issue, is there any helpful log
> > dumped when running kernel with kasan?
> 
> Last night, I ran six VM's using -rc4 with and without KASAN; without
> Kasan, half of them hung.  With KASAN enabled, all of the test VM's
> ran to completion.

>From your last email, when you run -rc4 with revert of 568f27006577, you
can observe list corruption easily.

So can you enable KASAN on -rc4 with revert of 568f27006577 and see if
it makes a difference?

> 
> This strongly suggests whatever the problem is, it's timing related.
> I'll run a larger set of test runs to see if this pattern is confirmed
> today.

Looks you enable lots of other debug options, such a lockdep, which has
much much heavy runtime load. Maybe you can disable all non-KASAN debug
option(non-KASAN memory debug options, lockdep, ...) and keep KASAN
debug only and see if you are lucky.


Thanks, 
Ming