blk-mq: provide internal in-flight variant

We don't have to inc/dec some counter, since we can just
iterate the tags. That makes inc/dec a noop, but means we
have to iterate busy tags to get an in-flight count.

Reviewed-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 31 insertions, 0 deletions

diff --git a/block/blk-mq.c b/block/blk-mq.c
index a5d369dc7622..0dfc7a9984b6 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -83,6 +83,37 @@ static void blk_mq_hctx_clear_pending(struct blk_mq_hw_ctx *hctx,
 	sbitmap_clear_bit(&hctx->ctx_map, ctx->index_hw);
 }
 
+struct mq_inflight {
+	struct hd_struct *part;
+	unsigned int *inflight;
+};
+
+static void blk_mq_check_inflight(struct blk_mq_hw_ctx *hctx,
+				  struct request *rq, void *priv,
+				  bool reserved)
+{
+	struct mq_inflight *mi = priv;
+
+	if (test_bit(REQ_ATOM_STARTED, &rq->atomic_flags) &&
+	    !test_bit(REQ_ATOM_COMPLETE, &rq->atomic_flags)) {
+		/*
+		 * Count as inflight if it either matches the partition we
+		 * asked for, or if it's the root
+		 */
+		if (rq->part == mi->part || mi->part->partno)
+			mi->inflight[0]++;
+	}
+}
+
+void blk_mq_in_flight(struct request_queue *q, struct hd_struct *part,
+		      unsigned int inflight[2])
+{
+	struct mq_inflight mi = { .part = part, .inflight = inflight, };
+
+	inflight[0] = 0;
+	blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi);
+}
+
 void blk_freeze_queue_start(struct request_queue *q)
 {
 	int freeze_depth;