blk-mq: don't handle failure in .get_budget

It is enough to just check if we can get the budget via .get_budget().
And we don't need to deal with device state change in .get_budget().

For SCSI, one issue to be fixed is that we have to call
scsi_mq_uninit_cmd() to free allocated ressources if SCSI device fails
to handle the request. And it isn't enough to simply call
blk_mq_end_request() to do that if this request is marked as
RQF_DONTPREP.

Fixes: 0df21c86bdbf(scsi: implement .get_budget and .put_budget for blk-mq)
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 7775f6b12fa94936b3944d899b4aaf147880a5db..13a27d4d1671df4ae32346e40b1e470e28eee413 100644 (file)
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -94,23 +94,18 @@ static void blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)
 
        do {
                struct request *rq;
-               blk_status_t ret;
 
                if (e->type->ops.mq.has_work &&
                                !e->type->ops.mq.has_work(hctx))
                        break;
 
-               ret = blk_mq_get_dispatch_budget(hctx);
-               if (ret == BLK_STS_RESOURCE)
+               if (!blk_mq_get_dispatch_budget(hctx))
                        break;
 
                rq = e->type->ops.mq.dispatch_request(hctx);
                if (!rq) {
                        blk_mq_put_dispatch_budget(hctx);
                        break;
-               } else if (ret != BLK_STS_OK) {
-                       blk_mq_end_request(rq, ret);
-                       continue;
                }
 
                /*
@@ -146,22 +141,17 @@ static void blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx)
 
        do {
                struct request *rq;
-               blk_status_t ret;
 
                if (!sbitmap_any_bit_set(&hctx->ctx_map))
                        break;
 
-               ret = blk_mq_get_dispatch_budget(hctx);
-               if (ret == BLK_STS_RESOURCE)
+               if (!blk_mq_get_dispatch_budget(hctx))
                        break;
 
                rq = blk_mq_dequeue_from_ctx(hctx, ctx);
                if (!rq) {
                        blk_mq_put_dispatch_budget(hctx);
                        break;
-               } else if (ret != BLK_STS_OK) {
-                       blk_mq_end_request(rq, ret);
-                       continue;
                }
 
                /*

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 13cdccef543ceed95e1af6901a65540deee8e2e1..c9fa4b294664afdbd9914399032350e7d0d9f46a 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1137,13 +1137,8 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list,
                        }
                }
 
-               if (!got_budget) {
-                       ret = blk_mq_get_dispatch_budget(hctx);
-                       if (ret == BLK_STS_RESOURCE)
-                               break;
-                       if (ret != BLK_STS_OK)
-                               goto fail_rq;
-               }
+               if (!got_budget && !blk_mq_get_dispatch_budget(hctx))
+                       break;
 
                list_del_init(&rq->queuelist);
 
@@ -1170,7 +1165,6 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list,
                        break;
                }
 
- fail_rq:
                if (unlikely(ret != BLK_STS_OK)) {
                        errors++;
                        blk_mq_end_request(rq, BLK_STS_IOERR);
@@ -1642,12 +1636,10 @@ static void __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
        if (!blk_mq_get_driver_tag(rq, NULL, false))
                goto insert;
 
-       ret = blk_mq_get_dispatch_budget(hctx);
-       if (ret == BLK_STS_RESOURCE) {
+       if (!blk_mq_get_dispatch_budget(hctx)) {
                blk_mq_put_driver_tag(rq);
                goto insert;
-       } else if (ret != BLK_STS_OK)
-               goto fail_rq;
+       }
 
        new_cookie = request_to_qc_t(hctx, rq);
 
@@ -1665,7 +1657,6 @@ static void __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
                __blk_mq_requeue_request(rq);
                goto insert;
        default:
- fail_rq:
                *cookie = BLK_QC_T_NONE;
                blk_mq_end_request(rq, ret);
                return;

diff --git a/block/blk-mq.h b/block/blk-mq.h
index 522b420dedc07ad8bd32cce618935087b81b4a8b..f97aceff76e91af732315a0ee4cc2be1ad48bb90 100644 (file)
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -147,14 +147,13 @@ static inline void blk_mq_put_dispatch_budget(struct blk_mq_hw_ctx *hctx)
                q->mq_ops->put_budget(hctx);
 }
 
-static inline blk_status_t blk_mq_get_dispatch_budget(
-               struct blk_mq_hw_ctx *hctx)
+static inline bool blk_mq_get_dispatch_budget(struct blk_mq_hw_ctx *hctx)
 {
        struct request_queue *q = hctx->queue;
 
        if (q->mq_ops->get_budget)
                return q->mq_ops->get_budget(hctx);
-       return BLK_STS_OK;
+       return true;
 }
 
 #endif

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 22a7e4c47207a722b3a1b554cbeaafd7b68fc39a..286ea983c9e3560db7d1a8099a9c5c942b0ea675 100644 (file)
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1955,27 +1955,22 @@ static void scsi_mq_put_budget(struct blk_mq_hw_ctx *hctx)
        put_device(&sdev->sdev_gendev);
 }
 
-static blk_status_t scsi_mq_get_budget(struct blk_mq_hw_ctx *hctx)
+static bool scsi_mq_get_budget(struct blk_mq_hw_ctx *hctx)
 {
        struct request_queue *q = hctx->queue;
        struct scsi_device *sdev = q->queuedata;
-       blk_status_t ret;
-
-       ret = prep_to_mq(scsi_prep_state_check(sdev, NULL));
-       if (ret == BLK_STS_RESOURCE || ret != BLK_STS_OK)
-               return ret;
 
        if (!get_device(&sdev->sdev_gendev))
                goto out;
        if (!scsi_dev_queue_ready(q, sdev))
                goto out_put_device;
 
-       return BLK_STS_OK;
+       return true;
 
 out_put_device:
        put_device(&sdev->sdev_gendev);
 out:
-       return BLK_STS_RESOURCE;
+       return false;
 }
 
 static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx,

diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index f2e3079eecdd8607edf561fbbd179fbba33e8981..674641527da79c9c86be42b0a2397bf2898625b5 100644 (file)
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -92,7 +92,7 @@ struct blk_mq_queue_data {
 
 typedef blk_status_t (queue_rq_fn)(struct blk_mq_hw_ctx *,
                const struct blk_mq_queue_data *);
-typedef blk_status_t (get_budget_fn)(struct blk_mq_hw_ctx *);
+typedef bool (get_budget_fn)(struct blk_mq_hw_ctx *);
 typedef void (put_budget_fn)(struct blk_mq_hw_ctx *);
 typedef enum blk_eh_timer_return (timeout_fn)(struct request *, bool);
 typedef int (init_hctx_fn)(struct blk_mq_hw_ctx *, void *, unsigned int);