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Subject[PATCH V10 8/8] SCSI: implement .get_budget and .put_budget for blk-mq
Date
We need to tell blk-mq for reserving resource before queuing
one request, so implement these two callbacks. Then blk-mq
can avoid to dequeue request earlier, and IO merge can
be improved a lot.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
drivers/scsi/scsi_lib.c | 75 ++++++++++++++++++++++++++++++++++---------------
1 file changed, 52 insertions(+), 23 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index d159bb085714..6f10afaca25b 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1946,25 +1946,32 @@ static void scsi_mq_done(struct scsi_cmnd *cmd)
blk_mq_complete_request(cmd->request);
}

-static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
- const struct blk_mq_queue_data *bd)
+static void scsi_mq_put_budget(struct blk_mq_hw_ctx *hctx)
{
- struct request *req = bd->rq;
- struct request_queue *q = req->q;
+ struct request_queue *q = hctx->queue;
+ struct scsi_device *sdev = q->queuedata;
+ struct Scsi_Host *shost = sdev->host;
+
+ atomic_dec(&shost->host_busy);
+ if (scsi_target(sdev)->can_queue > 0)
+ atomic_dec(&scsi_target(sdev)->target_busy);
+ atomic_dec(&sdev->device_busy);
+ put_device(&sdev->sdev_gendev);
+}
+
+static blk_status_t scsi_mq_get_budget(struct blk_mq_hw_ctx *hctx)
+{
+ struct request_queue *q = hctx->queue;
struct scsi_device *sdev = q->queuedata;
struct Scsi_Host *shost = sdev->host;
- struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
blk_status_t ret;
- int reason;

- ret = prep_to_mq(scsi_prep_state_check(sdev, req));
- if (ret != BLK_STS_OK)
- goto out;
+ ret = prep_to_mq(scsi_prep_state_check(sdev, NULL));
+ if (ret == BLK_STS_RESOURCE || ret != BLK_STS_OK)
+ return ret;

- ret = BLK_STS_RESOURCE;
if (!get_device(&sdev->sdev_gendev))
goto out;
-
if (!scsi_dev_queue_ready(q, sdev))
goto out_put_device;
if (!scsi_target_queue_ready(shost, sdev))
@@ -1972,10 +1979,38 @@ static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
if (!scsi_host_queue_ready(q, shost, sdev))
goto out_dec_target_busy;

+ return BLK_STS_OK;
+
+out_dec_target_busy:
+ if (scsi_target(sdev)->can_queue > 0)
+ atomic_dec(&scsi_target(sdev)->target_busy);
+out_dec_device_busy:
+ atomic_dec(&sdev->device_busy);
+out_put_device:
+ put_device(&sdev->sdev_gendev);
+out:
+ return BLK_STS_RESOURCE;
+}
+
+static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
+ const struct blk_mq_queue_data *bd)
+{
+ struct request *req = bd->rq;
+ struct request_queue *q = req->q;
+ struct scsi_device *sdev = q->queuedata;
+ struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
+ blk_status_t ret;
+ int reason;
+
+ ret = prep_to_mq(scsi_prep_state_check(sdev, req));
+ if (ret != BLK_STS_OK)
+ goto out_put_budget;
+
+ ret = BLK_STS_RESOURCE;
if (!(req->rq_flags & RQF_DONTPREP)) {
ret = prep_to_mq(scsi_mq_prep_fn(req));
if (ret != BLK_STS_OK)
- goto out_dec_host_busy;
+ goto out_put_budget;
req->rq_flags |= RQF_DONTPREP;
} else {
blk_mq_start_request(req);
@@ -1993,21 +2028,13 @@ static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
if (reason) {
scsi_set_blocked(cmd, reason);
ret = BLK_STS_RESOURCE;
- goto out_dec_host_busy;
+ goto out_put_budget;
}

return BLK_STS_OK;

-out_dec_host_busy:
- atomic_dec(&shost->host_busy);
-out_dec_target_busy:
- if (scsi_target(sdev)->can_queue > 0)
- atomic_dec(&scsi_target(sdev)->target_busy);
-out_dec_device_busy:
- atomic_dec(&sdev->device_busy);
-out_put_device:
- put_device(&sdev->sdev_gendev);
-out:
+out_put_budget:
+ scsi_mq_put_budget(hctx);
switch (ret) {
case BLK_STS_OK:
break;
@@ -2211,6 +2238,8 @@ struct request_queue *scsi_old_alloc_queue(struct scsi_device *sdev)
}

static const struct blk_mq_ops scsi_mq_ops = {
+ .get_budget = scsi_mq_get_budget,
+ .put_budget = scsi_mq_put_budget,
.queue_rq = scsi_queue_rq,
.complete = scsi_softirq_done,
.timeout = scsi_timeout,
--
2.9.5
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