* RE: [PATCH v2] blk-mq: Fix blk_mq_tagset_busy_iter() for shared tags
[not found] ` <163482611742.37241.15630114014516067630.b4-ty@kernel.dk>
@ 2021-12-09 13:52 ` Kashyap Desai
2021-12-09 14:42 ` John Garry
0 siblings, 1 reply; 3+ messages in thread
From: Kashyap Desai @ 2021-12-09 13:52 UTC (permalink / raw)
To: Jens Axboe, John Garry
Cc: linux-block, linux-kernel, hare, ming.lei, linux-scsi
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+ scsi mailing list
> On Mon, 18 Oct 2021 17:41:23 +0800, John Garry wrote:
> > Since it is now possible for a tagset to share a single set of tags,
> > the iter function should not re-iter the tags for the count of #hw
> > queues in that case. Rather it should just iter once.
John - Recently we found issue of error hander thread never kicked off and
this patch fix the issue.
Without this patch, scsi error hander will not find correct host_busy
counter.
Take one simple case. There is one IO outstanding and that is getting
timedout.
Now SML wants to wake up EH thread only if, below condition met
"scsi_host_busy(shost) == shost->host_failed"
Without this patch, shared host tag enabled meagaraid_sas driver will find
host_busy = actual outstanding * nr_hw_queues.
Error handler thread will never be kicked-off.
This patch is mandatory for fixing shared host tag feature and require to be
part of stable kernel.
Do you need more data for posting to stable kernel ?
Kashyap
> >
> >
>
> Applied, thanks!
>
> [1/1] blk-mq: Fix blk_mq_tagset_busy_iter() for shared tags
> commit: 0994c64eb4159ba019e7fedc7ba0dd6a69235b40
>
> Best regards,
> --
> Jens Axboe
>
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] blk-mq: Fix blk_mq_tagset_busy_iter() for shared tags
2021-12-09 13:52 ` [PATCH v2] blk-mq: Fix blk_mq_tagset_busy_iter() for shared tags Kashyap Desai
@ 2021-12-09 14:42 ` John Garry
2021-12-13 13:15 ` Kashyap Desai
0 siblings, 1 reply; 3+ messages in thread
From: John Garry @ 2021-12-09 14:42 UTC (permalink / raw)
To: Kashyap Desai, Jens Axboe
Cc: linux-block, linux-kernel, hare, ming.lei, linux-scsi
On 09/12/2021 13:52, Kashyap Desai wrote:
> + scsi mailing list
>
>> On Mon, 18 Oct 2021 17:41:23 +0800, John Garry wrote:
>>> Since it is now possible for a tagset to share a single set of tags,
>>> the iter function should not re-iter the tags for the count of #hw
>>> queues in that case. Rather it should just iter once.
> John - Recently we found issue of error hander thread never kicked off and
> this patch fix the issue.
> Without this patch, scsi error hander will not find correct host_busy
> counter.
>
> Take one simple case. There is one IO outstanding and that is getting
> timedout.
> Now SML wants to wake up EH thread only if, below condition met
> "scsi_host_busy(shost) == shost->host_failed"
>
> Without this patch, shared host tag enabled meagaraid_sas driver will find
> host_busy = actual outstanding * nr_hw_queues.
> Error handler thread will never be kicked-off.
>
> This patch is mandatory for fixing shared host tag feature and require to be
> part of stable kernel.
>
> Do you need more data for posting to stable kernel ?
To be clear, are you saying that you see the issue which patch "blk-mq:
Fix blk_mq_tagset_busy_iter() for shared tags" fixes before v5.16-rc?
This patch (now commit 0994c64eb415) and the commit which it is supposed
to fix, e155b0c238b2, will only be in v5.16, so I don't see anything
which is needed in stable.
Thanks,
John
^ permalink raw reply [flat|nested] 3+ messages in thread
* RE: [PATCH v2] blk-mq: Fix blk_mq_tagset_busy_iter() for shared tags
2021-12-09 14:42 ` John Garry
@ 2021-12-13 13:15 ` Kashyap Desai
0 siblings, 0 replies; 3+ messages in thread
From: Kashyap Desai @ 2021-12-13 13:15 UTC (permalink / raw)
To: John Garry, Jens Axboe
Cc: linux-block, linux-kernel, hare, ming.lei, linux-scsi
[-- Attachment #1: Type: text/plain, Size: 2091 bytes --]
> On 09/12/2021 13:52, Kashyap Desai wrote:
> > + scsi mailing list
> >
> >> On Mon, 18 Oct 2021 17:41:23 +0800, John Garry wrote:
> >>> Since it is now possible for a tagset to share a single set of tags,
> >>> the iter function should not re-iter the tags for the count of #hw
> >>> queues in that case. Rather it should just iter once.
> > John - Recently we found issue of error hander thread never kicked off
> > and this patch fix the issue.
> > Without this patch, scsi error hander will not find correct host_busy
> > counter.
> >
> > Take one simple case. There is one IO outstanding and that is getting
> > timedout.
> > Now SML wants to wake up EH thread only if, below condition met
> > "scsi_host_busy(shost) == shost->host_failed"
> >
> > Without this patch, shared host tag enabled meagaraid_sas driver will
> > find host_busy = actual outstanding * nr_hw_queues.
> > Error handler thread will never be kicked-off.
> >
> > This patch is mandatory for fixing shared host tag feature and require
> > to be part of stable kernel.
> >
> > Do you need more data for posting to stable kernel ?
>
> To be clear, are you saying that you see the issue which patch "blk-mq:
> Fix blk_mq_tagset_busy_iter() for shared tags" fixes before v5.16-rc?
>
> This patch (now commit 0994c64eb415) and the commit which it is supposed
> to fix, e155b0c238b2, will only be in v5.16, so I don't see anything which
> is
> needed in stable.
Hi John
Yes. No need of posting this to stable. There is still an issue which we
are tracking. It is not always reproducible. I am injecting artificial Task
abort on my setup to reproduce it.
It happens on rhel8.5 most of the time. It is a timing issue so thinking of
reproducing on other kernel as well.
I am suspecting issue might be due to missing commit -
67f3b2f822b7e71cfc9b42dbd9f3144fa2933e0b of [PATCH] blk-mq: avoid to
iterate over stale request
Whenever I notice the issue, there was a symptoms that host_busy is getting
counted for each hctx individually. Let me collect more data and I will
start another thread.
Kashyap
>
> Thanks,
> John
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2021-12-09 13:52 ` [PATCH v2] blk-mq: Fix blk_mq_tagset_busy_iter() for shared tags Kashyap Desai
2021-12-09 14:42 ` John Garry
2021-12-13 13:15 ` Kashyap Desai
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