From: Christoph Hellwig <hch@lst.de>
To: Hannes Reinecke <hare@suse.de>
Cc: lsf@lists.linux-foundation.org,
SCSI Mailing List <linux-scsi@vger.kernel.org>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>
Subject: Re: [LSF/MM TOPIC] block-mq issues with FC
Date: Fri, 8 Apr 2016 20:13:30 +0200 [thread overview]
Message-ID: <20160408181330.GA22406@lst.de> (raw)
In-Reply-To: <57079616.4000202@suse.de>
First: what is actually FC specific here?
> - timeout handling:
> Out of necessity the status of any timed out command is undefined.
> So to be absolutely safe HBAs will be using extended timeouts here
> (eg 70secs for lpfc). During that time we _could_ signal I/O timeout
> to the upper layers, but then the tag will be reused, despite the
> HBA still having a reference to it.
> I'd like to discuss how this could be solved best with blk-mq.
reusing a tag that the hardware hasn't returned is simply unsfafe,
nothing really blk-mq specific here.
> - Adaption on other HBAs to multiqueue:
> The current block-mq design assumes symmetric send and receive
> queues (in effect queue pairs). Any hardware _not_ providing this
> (like qla2xxx) can not be easily converted to scsi-mq. I'd like to
> discuss how one could approach converting these drivers.
Why do you think blk-mq assumes this?
prev parent reply other threads:[~2016-04-08 18:13 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-08 11:29 [LSF/MM TOPIC] block-mq issues with FC Hannes Reinecke
2016-04-08 15:11 ` James Bottomley
2016-04-08 15:51 ` [Lsf] " Ewan D. Milne
2016-04-08 16:06 ` James Bottomley
2016-04-08 17:26 ` Bart Van Assche
2016-04-08 17:40 ` Matthew Wilcox
2016-04-08 18:00 ` James Bottomley
2016-04-08 18:08 ` Christoph Hellwig
2016-04-08 18:24 ` James Bottomley
2016-04-08 18:06 ` Keith Busch
2016-04-12 19:16 ` Jens Axboe
2016-04-08 18:14 ` Bart Van Assche
2016-04-08 19:22 ` Waskiewicz, PJ
2016-04-10 19:02 ` Sagi Grimberg
2016-04-12 19:04 ` Quinn Tran
2016-04-08 18:13 ` Christoph Hellwig [this message]
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