Re: regression caused by block: freeze the queue earlier in del_gendisk

[Dusty Mabe <dusty@dustymabe.com>]

On 9/1/22 03:06, Ming Lei wrote:
> Hi Dusty,

Hi Ming,

> 
> On Fri, Aug 26, 2022 at 12:15:22PM -0400, Dusty Mabe wrote:
>> Hey All,
>>
>> I think I've found a regression introduced by:
>>
>> a09b314 o block: freeze the queue earlier in del_gendisk
>>
>> In Fedora CoreOS we have tests that set up RAID1 on the /boot/ and /root/ partitions
>> and then subsequently removes one of the disks to simulate a failure. Sometime recently
> 
> Do you have test case which doesn't need raid1 over /boot or /root? such
> as by create raid1 over two disks, then mount & remove one of device, ...
> 
> It isn't easy to setup/observe such test case and observe what is wrong.

I don't have such a test case. For Fedora CoreOS we have a very
specific partition layout [1] so it's not easy to change that
and continue to run our test framework.

That being said there are plenty of people in the bug report [2]
that are reporint seeing this as well, so they might have other
test cases they can share.

[1] https://github.com/coreos/fedora-coreos-tracker/blob/main/Design.md#disk-layout
[2] https://bugzilla.redhat.com/show_bug.cgi?id=2121791

> 
>> this test started timing out occasionally. Looking a bit closer it appears instances are
>> getting stuck during reboot with a bunch of looping messages:
>>
>> ```
>> [   17.978854] block device autoloading is deprecated and will be removed.
>> [   17.982555] block device autoloading is deprecated and will be removed.
>> [   17.985537] block device autoloading is deprecated and will be removed.
>> [   17.987546] block device autoloading is deprecated and will be removed.
>> [   17.989540] block device autoloading is deprecated and will be removed.
>> [   17.991547] block device autoloading is deprecated and will be removed.
>> [   17.993555] block device autoloading is deprecated and will be removed.
>> [   17.995539] block device autoloading is deprecated and will be removed.
>> [   17.997577] block device autoloading is deprecated and will be removed.
>> [   17.999544] block device autoloading is deprecated and will be removed.
>> [   22.979465] blkdev_get_no_open: 1666 callbacks suppressed
>> ...
>> ...
>> ...
>> [  618.221270] blkdev_get_no_open: 1664 callbacks suppressed
>> [  618.221273] block device autoloading is deprecated and will be removed.
>> [  618.224274] block device autoloading is deprecated and will be removed.
>> [  618.227267] block device autoloading is deprecated and will be removed.
>> [  618.229274] block device autoloading is deprecated and will be removed.
>> [  618.231277] block device autoloading is deprecated and will be removed.
>> [  618.233277] block device autoloading is deprecated and will be removed.
>> [  618.235282] block device autoloading is deprecated and will be removed.
>> [  618.237370] block device autoloading is deprecated and will be removed.
>> [  618.239356] block device autoloading is deprecated and will be removed.
>> [  618.241290] block device autoloading is deprecated and will be removed.
>> ```
>>
>> Using the Fedora kernels I narrowed it down to being introduced between 
>> `kernel-5.19.0-0.rc3.27.fc37` (good) and `kernel-5.19.0-0.rc4.33.fc37` (bad).
>>
>> I then did a bisect and found:
>>
>> ```
>> $ git bisect bad
>> a09b314005f3a0956ebf56e01b3b80339df577cc is the first bad commit
>> commit a09b314005f3a0956ebf56e01b3b80339df577cc
>> Author: Christoph Hellwig <hch@lst.de>
>> Date:   Tue Jun 14 09:48:27 2022 +0200
>>
>>     block: freeze the queue earlier in del_gendisk
> 
> It is a bit hard to associate the above commit with reported issue.

Indeed, though I think now there is enough emperical evidence that
points directly at this commit. It may ultimately end up as not the
root cause, but it's definitely related.

Dusty