From: Ming Lei ming.lei@redhat.com
commit 7e70aa789d4a0c89dbfbd2c8a974a4df717475ec upstream
Before commit 0df21c86bdbf ("scsi: implement .get_budget and .put_budget for blk-mq"), we run queue after 3ms if queue is idle and SCSI device queue isn't ready, which is done in handling BLK_STS_RESOURCE. After commit 0df21c86bdbf is introduced, queue won't be run any more under this situation.
IO hang is observed when timeout happened, and this patch fixes the IO hang issue by running queue after delay in scsi_dev_queue_ready, just like non-mq. This issue can be triggered by the following script[1].
There is another issue which can be covered by running idle queue: when .get_budget() is called on request coming from hctx->dispatch_list, if one request just completes during .get_budget(), we can't depend on SCSI's restart to make progress any more. This patch fixes the race too.
With this patch, we basically recover to previous behaviour (before commit 0df21c86bdbf) of handling idle queue when running out of resource.
[1] script for test/verify SCSI timeout rmmod scsi_debug modprobe scsi_debug max_queue=1
DEVICE=`ls -d /sys/bus/pseudo/drivers/scsi_debug/adapter*/host*/target*/*/block/* | head -1 | xargs basename` DISK_DIR=`ls -d /sys/block/$DEVICE/device/scsi_disk/*`
echo "using scsi device $DEVICE" echo "-1" >/sys/bus/pseudo/drivers/scsi_debug/every_nth echo "temporary write through" >$DISK_DIR/cache_type echo "128" >/sys/bus/pseudo/drivers/scsi_debug/opts echo none > /sys/block/$DEVICE/queue/scheduler dd if=/dev/$DEVICE of=/dev/null bs=1M iflag=direct count=1 & sleep 5 echo "0" >/sys/bus/pseudo/drivers/scsi_debug/opts wait echo "SUCCESS"
Fixes: 0df21c86bdbf ("scsi: implement .get_budget and .put_budget for blk-mq") Signed-off-by: Ming Lei ming.lei@redhat.com Tested-by: Holger Hoffstätte holger@applied-asynchrony.com Reviewed-by: Bart Van Assche bart.vanassche@wdc.com Signed-off-by: Martin K. Petersen martin.petersen@oracle.com Signed-off-by: Jack Wang jinpu.wang@profitbricks.com --- drivers/scsi/scsi_lib.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index 9e242583ab83..175981058396 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -1994,6 +1994,8 @@ static bool scsi_mq_get_budget(struct blk_mq_hw_ctx *hctx) out_put_device: put_device(&sdev->sdev_gendev); out: + if (atomic_read(&sdev->device_busy) == 0 && !scsi_device_blocked(sdev)) + blk_mq_delay_run_hw_queue(hctx, SCSI_QUEUE_DELAY); return false; }