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Subject: Re: General protection fault with use_blk_mq=1.
To:     Jens Axboe <axboe@kernel.dk>,
        "Zephaniah E. Loss-Cutler-Hull" <warp-spam_kernel@aehallh.com>,
        linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
        linux-scsi@vger.kernel.org
References: <7d8a9c62-7d3e-879c-5b5b-30707f04553e@aehallh.com>
 <ae71cc99-02f1-2b42-bb76-d6e28d61ca21@kernel.dk>
From:   "Zephaniah E. Loss-Cutler-Hull" <warp@aehallh.com>
Message-ID: <b347896e-f770-8987-ad90-a595a5fa926a@aehallh.com>
Date:   Wed, 28 Mar 2018 20:13:08 -0700
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From: "Zephaniah E. Loss-Cutler-Hull" <warp@aehallh.com>
To: Jens Axboe <axboe@kernel.dk>,
 "Zephaniah E. Loss-Cutler-Hull" <warp-spam_kernel@aehallh.com>,
 linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
 linux-scsi@vger.kernel.org
Message-ID: <b347896e-f770-8987-ad90-a595a5fa926a@aehallh.com>
Subject: Re: General protection fault with use_blk_mq=1.
References: <7d8a9c62-7d3e-879c-5b5b-30707f04553e@aehallh.com>
 <ae71cc99-02f1-2b42-bb76-d6e28d61ca21@kernel.dk>
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On 03/28/2018 06:02 PM, Jens Axboe wrote:
> On 3/28/18 5:03 PM, Zephaniah E. Loss-Cutler-Hull wrote:
>> I am not subscribed to any of the lists on the To list here, please CC=

>> me on any replies.
>>
>> I am encountering a fairly consistent crash anywhere from 15 minutes t=
o
>> 12 hours after boot with scsi_mod.use_blk_mq=3D1 dm_mod.use_blk_mq=3D1=
>=20
>> The crash looks like:
>>

>>
>> Looking through the code, I'd guess that this is dying inside
>> blkg_rwstat_add, which calls percpu_counter_add_batch, which is what R=
IP
>> is pointing at.
>=20
> Leaving the whole thing here for Paolo - it's crashing off insertion of=

> a request coming out of SG_IO. Don't think we've seen this BFQ failure
> case before.
>=20
> You can mitigate this by switching the scsi-mq devices to mq-deadline
> instead.
>=20

I'm thinking that I should also be able to mitigate it by disabling
CONFIG_DEBUG_BLK_CGROUP.

That should remove that entire chunk of code.

Of course, that won't help if this is actually a symptom of a bigger
problem.

Regards,
Zephaniah E. Loss-Cutler-Hull.


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