Linux-NVME Archive on lore.kernel.org
 help / color / Atom feed
From: Hannes Reinecke <hare@suse.de>
To: linux-nvme@lists.infradead.org
Subject: Re: [PATCH V2] nvme: Add support for ACRE Command Interrupted status
Date: Wed, 4 Dec 2019 14:26:06 +0100
Message-ID: <04835a2e-1769-36c9-63b8-173f247c862b@suse.de> (raw)
In-Reply-To: <20191203210015.GA2691@redsun51.ssa.fujisawa.hgst.com>

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
> BLK_STS_TARGET.
> 
I don't mind; whichever works for you.

Cheers,

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

_______________________________________________
linux-nvme mailing list
linux-nvme@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-nvme

  reply index

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

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=04835a2e-1769-36c9-63b8-173f247c862b@suse.de \
    --to=hare@suse.de \
    --cc=linux-nvme@lists.infradead.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-NVME Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-nvme/0 linux-nvme/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-nvme linux-nvme/ https://lore.kernel.org/linux-nvme \
		linux-nvme@lists.infradead.org
	public-inbox-index linux-nvme

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.infradead.lists.linux-nvme


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git