Re: [PATCH 03/12] blk-mq: Explain when 'active_queues' is decremented

It is nontrivial to derive from the blk-mq source code when
blk_mq_tags.active_queues is decremented. Hence add a comment that
explains this.

Signed-off-by: Bart Van Assche <redacted>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Johannes Thumshirn <redacted>
---
 block/blk-mq.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index f84d145490bf..b86d2cafc355 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c

@@ -834,6 +834,10 @@ static void blk_mq_timeout_work(struct work_struct *work)
 	} else {
 		struct blk_mq_hw_ctx *hctx;
 
+		/*
+		 * All requests finished (latest request timeout) seconds ago,
+		 * so mark each hctx as idle.
+		 */
 		queue_for_each_hw_ctx(q, hctx, i) {
 			/* the hctx may be unmapped, so check it here */
 			if (blk_mq_hw_queue_mapped(hctx))