Re: REGRESSION: 37f4a24c2469: blk-mq: centralise related handling into blk_mq_get_driver_tag

Ming Lei
2020-09-15T07:33:32Z

Hi Theodore,

On Tue, Sep 15, 2020 at 12:45:19AM -0400, Theodore Y. Ts'o wrote:
> On Thu, Sep 03, 2020 at 11:55:28PM -0400, Theodore Y. Ts'o wrote:
> > Worse, right now, -rc1 and -rc2 is causing random crashes in my
> > gce-xfstests framework. Sometimes it happens before we've run even a
> > single xfstests; sometimes it happens after we have successfully
> > completed all of the tests, and we're doing a shutdown of the VM under
> > test. Other times it happens in the middle of a test run. Given that
> > I'm seeing this at -rc1, which is before my late ext4 pull request to
> > Linus, it's probably not an ext4 related bug. But it also means that
> > I'm partially blind in terms of my kernel testing at the moment. So I
> > can't even tell Linus that I've run lots of tests and I'm 100%
> > confident your one-line change is 100% safe.
>
> I was finally able to bisect it down to the commit:
>
> 37f4a24c2469: blk-mq: centralise related handling into blk_mq_get_driver_tag

37f4a24c2469 has been reverted in:

4e2f62e566b5 Revert "blk-mq: put driver tag when this request is completed"

And later the patch is committed as the following after being fixed:

568f27006577 blk-mq: centralise related handling into blk_mq_get_driver_tag

So can you reproduce the issue by running kernel of commit 568f27006577?
If yes, can the issue be fixed by reverting 568f27006577?

>
> (See below for [1] Bisect log.)
>
> The previous commit allows the tests to run to completion. With
> commit 37f4a24c2469 and later all 11 test scenarios (4k blocks, 1k
> blocks, ext3 compat, ext4 w/ fscrypt, nojournal mode, data=journal,
> bigalloc, etc.) the VM will get stuck.

Can you share the exact mount command line for setup the environment?
and the exact xfstest item?

Thanks,
Ming