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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