scsi: implement .get_budget and .put_budget for blk-mq

We need to tell blk-mq to reserve resources before queuing one request,
so implement these two callbacks. Then blk-mq can avoid to dequeue
request too early, and IO merging can be improved a lot.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index d159bb085714483c5efb93d07d1633e63f959429..6f10afaca25b2eb03c4088b28f1d53221dc62d88 100644 (file)
--- 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,