linux-kernel - Re: [block] allow blk_flush_policy to return REQ_FSEQ

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Date:	Tue, 9 Aug 2011 20:29:27 +0200
From:	Jens Axboe <jaxboe@...ionio.com>
To:	Jeff Moyer <jmoyer@...hat.com>
CC:	Tejun Heo <tj@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [block] allow blk_flush_policy to return REQ_FSEQ_DATA independent
  of *FLUSH

On 2011-08-09 17:24, Jeff Moyer wrote:
> Hi,
> 
> blk_insert_flush has the following check:
> 
> 	/*
> 	 * If there's data but flush is not necessary, the request can be
> 	 * processed directly without going through flush machinery.  Queue
> 	 * for normal execution.
> 	 */
> 	if ((policy & REQ_FSEQ_DATA) &&
> 	    !(policy & (REQ_FSEQ_PREFLUSH | REQ_FSEQ_POSTFLUSH))) {
> 		list_add_tail(&rq->queuelist, &q->queue_head);
> 		return;
> 	}
> 
> However, blk_flush_policy will not return with policy set to only
> REQ_FSEQ_DATA:
> 
> static unsigned int blk_flush_policy(unsigned int fflags, struct request *rq)
> {
> 	unsigned int policy = 0;
> 
> 	if (fflags & REQ_FLUSH) {
> 		if (rq->cmd_flags & REQ_FLUSH)
> 			policy |= REQ_FSEQ_PREFLUSH;
> 		if (blk_rq_sectors(rq))
> 			policy |= REQ_FSEQ_DATA;
> 		if (!(fflags & REQ_FUA) && (rq->cmd_flags & REQ_FUA))
> 			policy |= REQ_FSEQ_POSTFLUSH;
> 	}
> 	return policy;
> }
> 
> Notice that REQ_FSEQ_DATA is only set if REQ_FLUSH is set.  Fix this
> mismatch by moving the setting of REQ_FSEQ_DATA outside of the REQ_FLUSH
> check.

Thanks Jeff, applied.

-- 
Jens Axboe

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