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>

5 files changed, 12 insertions, 37 deletions

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 7775f6b12fa9..13a27d4d1671 100644
--- 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 13cdccef543c..c9fa4b294664 100644
--- 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 522b420dedc0..f97aceff76e9 100644
--- 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 22a7e4c47207..286ea983c9e3 100644
--- 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 f2e3079eecdd..674641527da7 100644
--- 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);