Messages in this thread | | | Date | Fri, 19 Sep 2008 11:06:04 -0500 | From | Mike Christie <> | Subject | Re: [dm-devel] [PATCH 2/2] scsi: exports busy status via bdi_lld_congested |
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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)
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