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From: Hannes Reinecke <>
Subject: Re: [PATCH V2] nvme: Add support for ACRE Command Interrupted status
Date: Wed, 4 Dec 2019 14:26:06 +0100
Message-ID: <> (raw)
In-Reply-To: <>

On 12/3/19 10:00 PM, Keith Busch wrote:
> On Tue, Dec 03, 2019 at 05:38:04PM +0000, Meneghini, John wrote:
>> This is an update to say that I've tested this patch and it works as expected. 
>> When the controller returns a Command Interrupted status the request is avoids nvme_failover_req()
>> and goes down the nvme_retry_req() path where the CRD is implemented and the command is 
>> retried after a delay.
>> If the controllers returns Command Interrupted too many times, and nvme_req(req)->retries
>> runs down, this results in a device resource error returned to the block layer.  But I think we'll
>> have this problem with any error.  
> Why is the controller returning the same error so many times? Are we
> not waiting the requested delay timed? If so, the controller told us
> retrying should be successful.
> It is possible we kick the requeue list early if one command error
> has a valid CRD, but a subsequent retryable command does not. Is that
> what's happening?
No. The problem is that CRD needs to be observed _in all cases_ whenever
we get a COMMAND INTERRUPTED status.
Currently we're only observing CRD when multipathing is _not_ active,
which is wrong.

And this is what the patch is trying to achieve.

> I'm just concerned because if we just skip counting the retry, a broken
> device could have the driver retry the same command indefinitely, which
> often leaves a task in an uninterruptible sleep state forever.
Oh, but we're not skipping the retries; in fact we do _enable_ retry
counting with this patch as we're skipping the nvme_failover_req()
branch and moving to nvme_retry_req().

>>     diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
>>     index 9696404a6182..24dc9ed1a11b 100644
>>     --- a/drivers/nvme/host/core.c
>>     +++ b/drivers/nvme/host/core.c
>>     @@ -230,6 +230,8 @@ static blk_status_t nvme_error_status(u16 status)
>>                     return BLK_STS_NEXUS;
>>             case NVME_SC_HOST_PATH_ERROR:
>>                     return BLK_STS_TRANSPORT;
>>     +       case NVME_SC_CMD_INTERRUPTED:
>>     +               return BLK_STS_DEV_RESOURCE;
> Just for the sake of keeping this change isloted to nvme, perhaps use an
> existing blk_status_t value that already maps to not path error, like
I don't mind; whichever works for you.


Dr. Hannes Reinecke		      Teamlead Storage & Networking			                  +49 911 74053 688
SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), GF: Felix Imendörffer

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Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-27 19:12 Meneghini, John
2019-12-03 17:38 ` Meneghini, John
2019-12-03 21:00   ` Keith Busch
2019-12-04 13:26     ` Hannes Reinecke [this message]
2019-12-04 14:48       ` Meneghini, John
2019-12-04 16:07       ` Keith Busch
2019-12-04 18:33         ` Meneghini, John

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