[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]

Re: [dm-devel] [PATCH 2/2] scsi: exports busy status via bdi_lld_congested



Kiyoshi Ueda wrote:
This patch change scsi mid layer to export its busy status.
Not set the busy flag, when scsi can't dispatch I/Os anymore and
needs to kill I/Os.  Otherwise, request stacking drivers may hold
requests forever.


Signed-off-by: Kiyoshi Ueda <k-ueda ct jp nec com>
Signed-off-by: Jun'ichi Nomura <j-nomura ce jp nec com>
Cc: James Bottomley <James Bottomley HansenPartnership com>
---
 drivers/scsi/scsi.c     |    4 ++--
 drivers/scsi/scsi_lib.c |   23 ++++++++++++++++++++++-
 2 files changed, 24 insertions(+), 3 deletions(-)

Index: scsi-misc-2.6/drivers/scsi/scsi_lib.c
===================================================================
--- scsi-misc-2.6.orig/drivers/scsi/scsi_lib.c
+++ scsi-misc-2.6/drivers/scsi/scsi_lib.c
@@ -459,17 +459,30 @@ static void scsi_init_cmd_errh(struct sc
void scsi_device_unbusy(struct scsi_device *sdev)
 {
+	int host_congested;
 	struct Scsi_Host *shost = sdev->host;
 	unsigned long flags;
spin_lock_irqsave(shost->host_lock, flags);
 	shost->host_busy--;
+	if ((shost->can_queue > 0 && shost->host_busy >= shost->can_queue) ||
+	    shost->host_blocked || shost->host_self_blocked ||
+	    scsi_host_in_recovery(shost))
+		host_congested = 1;
+	else
+		host_congested = 0;
+

You might want to check if the starget busy too (scsi-misc has this but Jens's tree and linus do not)? The code below that I snipped from scsi_request_fn will set the congested bits if scsi_target_queue_ready returns 0, so above here you would want to clear it if it not congested anymore.

 	if (unlikely(scsi_host_in_recovery(shost) &&
 		     (shost->host_failed || shost->host_eh_scheduled)))
 		scsi_eh_wakeup(shost);
 	spin_unlock(shost->host_lock);
+
 	spin_lock(sdev->request_queue->queue_lock);
 	sdev->device_busy--;
+	if (bdi_lld_congested(&sdev->request_queue->backing_dev_info) &&
+	    !host_congested && sdev->device_busy < sdev->queue_depth &&
+	    !sdev->device_blocked)
+		clear_bdi_lld_congested(&sdev->request_queue->backing_dev_info);
 	spin_unlock_irqrestore(sdev->request_queue->queue_lock, flags);
 }



@@ -1593,6 +1613,7 @@ static void scsi_request_fn(struct reque
 	 * later time.
 	 */
 	spin_lock_irq(q->queue_lock);
+	set_bdi_lld_congested(&q->backing_dev_info);
 	blk_requeue_request(q, req);
 	sdev->device_busy--;
 	if(sdev->device_busy == 0)


[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]