From: James Bottomley <James.Bottomley@steeleye.com>
To: Patrick Mansfield <patmans@us.ibm.com>
Cc: SCSI Mailing List <linux-scsi@vger.kernel.org>
Subject: Re: 2.5.x why a conditional call to blkdev_dequeue_request?
Date: 07 Apr 2003 23:13:06 -0500 [thread overview]
Message-ID: <1049775188.1749.82.camel@mulgrave> (raw)
In-Reply-To: <20030407204005.A4219@beaverton.ibm.com>
On Mon, 2003-04-07 at 22:40, Patrick Mansfield wrote:
> Why do we conditionally call blkdev_dequeue_request, and yet run the same
> code even if a request is not dequeued?
>
> Should we always call blkdev_dequeue_request, and handle
> blk_queue_start_tag() returning != 0 as a bug or a resource limitation?
>
> In 2.5 scsi_lib.c scsi_request_fn right now we have:
>
> if (!(blk_queue_tagged(q) && (blk_queue_start_tag(q, req) == 0)))
> blkdev_dequeue_request(req);
>
> /* then handle the request whether it was dequeued or not */
>
blk_queue_start_tag dequeues for you. It's for IDE and other block code
where the request is left in the queue while being processed. In SCSI
we dequeue regardless of whether we're tagged or not.
James
prev parent reply other threads:[~2003-04-08 4:01 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-04-08 3:40 2.5.x why a conditional call to blkdev_dequeue_request? Patrick Mansfield
2003-04-08 4:13 ` James Bottomley [this message]
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