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Groups > linux.kernel > #1277113
| From | Hannes Reinecke <hare@suse.de> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! |
| Date | 2015-11-25 10:10 +0100 |
| Message-ID | <qyEfo-48i-13@gated-at.bofh.it> (permalink) |
| References | (3 earlier) <qwsLo-6Qc-9@gated-at.bofh.it> <qwztx-2Iv-35@gated-at.bofh.it> <qwV0Z-8qz-11@gated-at.bofh.it> <qwVu2-q6-25@gated-at.bofh.it> <qwVNn-xS-1@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On 11/20/2015 04:28 PM, Ewan Milne wrote:
> On Fri, 2015-11-20 at 15:55 +0100, Hannes Reinecke wrote:
>> Can't we have a joint effort here?
>> I've been spending a _LOT_ of time trying to debug things here, but
>> none of the ideas I've come up with have been able to fix anything.
>
> Yes. I'm not the one primarily looking at it, and we don't have a
> reproducer in-house. We just have the one dump right now.
>
>>
>> I'm almost tempted to increase the count from scsi_alloc_sgtable()
>> by one and be done with ...
>>
>
> That might not fix it if it is a problem with the merge code, though.
>
And indeed, it doesn't.
Seems I finally found the culprit.
What happens is this:
We have two paths, with these seg_boundary_masks:
path-1: seg_boundary_mask = 65535,
path-2: seg_boundary_mask = 4294967295,
consequently the DM request queue has this:
md-1: seg_boundary_mask = 65535,
What happens now is that a request is being formatted, and sent
to path 2. During submission req->nr_phys_segments is formatted
with the limits of path 2, arriving at a count of 3.
Now the request gets retried on path 1, but as the NOMERGE request
flag is set req->nr_phys_segments is never updated.
But blk_rq_map_sg() ignores all counters, and just uses the
bi_vec directly, resulting in a count of 4 -> boom.
So the culprit here is the NOMERGE flag, which is evaluated
via
->dm_dispatch_request()
->blk_insert_cloned_request()
->blk_rq_check_limits()
If the above assessment is correct, the following patch should
fix it:
diff --git a/block/blk-core.c b/block/blk-core.c
index 801ced7..12cccd6 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1928,7 +1928,7 @@ EXPORT_SYMBOL(submit_bio);
*/
int blk_rq_check_limits(struct request_queue *q, struct request *rq)
{
- if (!rq_mergeable(rq))
+ if (rq->cmd_type != REQ_TYPE_FS)
return 0;
if (blk_rq_sectors(rq) > blk_queue_get_max_sectors(q,
rq->cmd_flags)) {
Mike? Jens?
Can you comment on it?
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries & Storage
hare@suse.de +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)
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kernel BUG at drivers/scsi/scsi_lib.c:1096! Michael Ellerman <mpe@ellerman.id.au> - 2015-11-18 10:20 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Mark Salter <msalter@redhat.com> - 2015-11-18 15:10 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Michael Ellerman <mpe@ellerman.id.au> - 2015-11-19 02:10 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Christoph Hellwig <hch@infradead.org> - 2015-11-19 09:30 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Hannes Reinecke <hare@suse.de> - 2015-11-19 16:40 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Ewan Milne <emilne@redhat.com> - 2015-11-20 15:40 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Hannes Reinecke <hare@suse.de> - 2015-11-20 16:10 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Ewan Milne <emilne@redhat.com> - 2015-11-20 16:30 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Hannes Reinecke <hare@suse.de> - 2015-11-23 08:00 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Hannes Reinecke <hare@suse.de> - 2015-11-25 10:10 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Jens Axboe <axboe@fb.com> - 2015-11-25 19:00 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Hannes Reinecke <hare@suse.de> - 2015-11-25 20:20 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Jens Axboe <axboe@fb.com> - 2015-11-25 20:30 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Mike Snitzer <snitzer@redhat.com> - 2015-11-25 21:30 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Mike Snitzer <snitzer@redhat.com> - 2015-11-25 22:30 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Mike Snitzer <snitzer@redhat.com> - 2015-11-25 19:10 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Hannes Reinecke <hare@suse.de> - 2015-11-25 20:10 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Michael Ellerman <mpe@ellerman.id.au> - 2015-11-20 13:20 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Laurent Dufour <ldufour@linux.vnet.ibm.com> - 2015-11-20 14:00 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Mark Salter <msalter@redhat.com> - 2015-11-20 14:40 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Laurent Dufour <ldufour@linux.vnet.ibm.com> - 2015-11-21 12:40 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Ming Lei <ming.lei@canonical.com> - 2015-11-21 18:00 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Mark Salter <msalter@redhat.com> - 2015-11-23 00:30 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Ming Lei <ming.lei@canonical.com> - 2015-11-23 01:40 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Mark Salter <msalter@redhat.com> - 2015-11-23 03:00 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Ming Lei <ming.lei@canonical.com> - 2015-11-23 03:50 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Ming Lei <tom.leiming@gmail.com> - 2015-11-23 16:30 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Alan Ott <alan@softiron.co.uk> - 2015-11-24 20:40 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Laurent Dufour <ldufour@linux.vnet.ibm.com> - 2015-11-23 15:00 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Pratyush Anand <panand@redhat.com> - 2015-11-23 16:20 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Laurent Dufour <ldufour@linux.vnet.ibm.com> - 2015-11-23 16:30 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Ming Lei <ming.lei@canonical.com> - 2015-11-23 16:30 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Laurent Dufour <ldufour@linux.vnet.ibm.com> - 2015-11-23 17:30 +0100
Re: kernel BUG at drivers/scsi/scsi_lib.c:1096! Mark Salter <msalter@redhat.com> - 2015-11-24 02:40 +0100
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