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Commit 6c5121b7 authored by Kiyoshi Ueda's avatar Kiyoshi Ueda Committed by James Bottomley
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[SCSI] export busy state via q->lld_busy_fn() 



This patch implements q->lld_busy_fn() for scsi mid layer to export
its busy state for request stacking drivers.

For efficiency, no lock is taken to check the busy state of
shost/starget/sdev, since the returned value is not guaranteed and
may be changed after request stacking drivers call the function,
regardless of taking lock or not.

When scsi can't dispatch I/Os anymore and needs to kill I/Os
(e.g. !sdev), scsi needs to return 'not busy'.
Otherwise, request stacking drivers may hold requests forever.

Signed-off-by: default avatarKiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: default avatarJun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: default avatarJames Bottomley <James.Bottomley@HansenPartnership.com>
parent 9d112517

drivers/scsi/scsi_lib.c

+32 −0
Original line number Diff line number Diff line
@@ -1464,6 +1464,37 @@ static inline int scsi_host_queue_ready(struct request_queue *q, 
	return 1;

}



/*

 * Busy state exporting function for request stacking drivers.

 *

 * For efficiency, no lock is taken to check the busy state of

 * shost/starget/sdev, since the returned value is not guaranteed and

 * may be changed after request stacking drivers call the function,

 * regardless of taking lock or not.

 *

 * When scsi can't dispatch I/Os anymore and needs to kill I/Os

 * (e.g. !sdev), scsi needs to return 'not busy'.

 * Otherwise, request stacking drivers may hold requests forever.

 */

static int scsi_lld_busy(struct request_queue *q)

{

	struct scsi_device *sdev = q->queuedata;

	struct Scsi_Host *shost;

	struct scsi_target *starget;



	if (!sdev)

		return 0;



	shost = sdev->host;

	starget = scsi_target(sdev);



	if (scsi_host_in_recovery(shost) || scsi_host_is_busy(shost) ||

	    scsi_target_is_busy(starget) || scsi_device_is_busy(sdev))

		return 1;



	return 0;

}



/*

 * Kill a request for a dead device

 */
@@ -1767,6 +1798,7 @@ struct request_queue *scsi_alloc_queue(struct scsi_device *sdev) 
	blk_queue_prep_rq(q, scsi_prep_fn);

	blk_queue_softirq_done(q, scsi_softirq_done);

	blk_queue_rq_timed_out(q, scsi_times_out);

	blk_queue_lld_busy(q, scsi_lld_busy);

	return q;

}