blk-mq: centralise related handling into blk_mq_get_driver_tag

Move .nr_active update and request assignment into blk_mq_get_driver_tag(),
all are good to do during getting driver tag.

Meantime blk-flush related code is simplified and flush request needn't
to update the request table manually any more.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-flush.c

@@ -236,12 +236,10 @@ static void flush_end_io(struct request *flush_rq, blk_status_t error)
 		error = fq->rq_status;
 
 	hctx = flush_rq->mq_hctx;
-	if (!q->elevator) {
-		blk_mq_tag_set_rq(hctx, flush_rq->tag, fq->orig_rq);
-		flush_rq->tag = -1;
-	} else {
-		flush_rq->internal_tag = -1;
-	}
+	if (!q->elevator)
+		flush_rq->tag = BLK_MQ_NO_TAG;
+	else
+		flush_rq->internal_tag = BLK_MQ_NO_TAG;
 
 	running = &fq->flush_queue[fq->flush_running_idx];
 	BUG_ON(fq->flush_pending_idx == fq->flush_running_idx);
@@ -315,13 +313,10 @@ static void blk_kick_flush(struct request_queue *q, struct blk_flush_queue *fq,
 	flush_rq->mq_ctx = first_rq->mq_ctx;
 	flush_rq->mq_hctx = first_rq->mq_hctx;
 
-	if (!q->elevator) {
-		fq->orig_rq = first_rq;
+	if (!q->elevator)
 		flush_rq->tag = first_rq->tag;
-		blk_mq_tag_set_rq(flush_rq->mq_hctx, first_rq->tag, flush_rq);
-	} else {
+	else
 		flush_rq->internal_tag = first_rq->internal_tag;
-	}
 
 	flush_rq->cmd_flags = REQ_OP_FLUSH | REQ_PREFLUSH;
 	flush_rq->cmd_flags |= (flags & REQ_DRV) | (flags & REQ_FAILFAST_MASK);

block/blk-mq-tag.h

@@ -101,18 +101,6 @@ static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
 	return atomic_read(&hctx->nr_active) < depth;
 }
 
-/*
- * This helper should only be used for flush request to share tag
- * with the request cloned from, and both the two requests can't be
- * in flight at the same time. The caller has to make sure the tag
- * can't be freed.
- */
-static inline void blk_mq_tag_set_rq(struct blk_mq_hw_ctx *hctx,
-		unsigned int tag, struct request *rq)
-{
-	hctx->tags->rqs[tag] = rq;
-}
-
 static inline bool blk_mq_tag_is_reserved(struct blk_mq_tags *tags,
 					  unsigned int tag)
 {

block/blk-mq.c

@@ -277,26 +277,20 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
 {
 	struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
 	struct request *rq = tags->static_rqs[tag];
-	req_flags_t rq_flags = 0;
 
 	if (data->q->elevator) {
 		rq->tag = BLK_MQ_NO_TAG;
 		rq->internal_tag = tag;
 	} else {
-		if (data->hctx->flags & BLK_MQ_F_TAG_SHARED) {
-			rq_flags = RQF_MQ_INFLIGHT;
-			atomic_inc(&data->hctx->nr_active);
-		}
 		rq->tag = tag;
 		rq->internal_tag = BLK_MQ_NO_TAG;
-		data->hctx->tags->rqs[rq->tag] = rq;
 	}
 
 	/* csd/requeue_work/fifo_time is initialized before use */
 	rq->q = data->q;
 	rq->mq_ctx = data->ctx;
 	rq->mq_hctx = data->hctx;
-	rq->rq_flags = rq_flags;
+	rq->rq_flags = 0;
 	rq->cmd_flags = data->cmd_flags;
 	if (data->flags & BLK_MQ_REQ_PREEMPT)
 		rq->rq_flags |= RQF_PREEMPT;
@@ -1127,9 +1121,10 @@ static bool __blk_mq_get_driver_tag(struct request *rq)
 {
 	struct sbitmap_queue *bt = &rq->mq_hctx->tags->bitmap_tags;
 	unsigned int tag_offset = rq->mq_hctx->tags->nr_reserved_tags;
-	bool shared = blk_mq_tag_busy(rq->mq_hctx);
 	int tag;
 
+	blk_mq_tag_busy(rq->mq_hctx);
+
 	if (blk_mq_tag_is_reserved(rq->mq_hctx->sched_tags, rq->internal_tag)) {
 		bt = &rq->mq_hctx->tags->breserved_tags;
 		tag_offset = 0;
@@ -1142,19 +1137,22 @@ static bool __blk_mq_get_driver_tag(struct request *rq)
 		return false;
 
 	rq->tag = tag + tag_offset;
-	if (shared) {
-		rq->rq_flags |= RQF_MQ_INFLIGHT;
-		atomic_inc(&rq->mq_hctx->nr_active);
-	}
-	rq->mq_hctx->tags->rqs[rq->tag] = rq;
 	return true;
 }
 
 static bool blk_mq_get_driver_tag(struct request *rq)
 {
-	if (rq->tag != BLK_MQ_NO_TAG)
-		return true;
-	return __blk_mq_get_driver_tag(rq);
+	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
+
+	if (rq->tag == BLK_MQ_NO_TAG && !__blk_mq_get_driver_tag(rq))
+		return false;
+
+	if (hctx->flags & BLK_MQ_F_TAG_SHARED) {
+		rq->rq_flags |= RQF_MQ_INFLIGHT;
+		atomic_inc(&hctx->nr_active);
+	}
+	hctx->tags->rqs[rq->tag] = rq;
+	return true;
 }
 
 static int blk_mq_dispatch_wake(wait_queue_entry_t *wait, unsigned mode,

block/blk.h

@@ -25,11 +25,6 @@ struct blk_flush_queue {
 	struct list_head	flush_data_in_flight;
 	struct request		*flush_rq;
 
-	/*
-	 * flush_rq shares tag with this rq, both can't be active
-	 * at the same time
-	 */
-	struct request		*orig_rq;
 	struct lock_class_key	key;
 	spinlock_t		mq_flush_lock;
 };