On Thu, Aug 17 2017, Bart Van Assche wrote:
> 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 <bart.vanassche@xxxxxxx>
> Cc: Christoph Hellwig <hch@xxxxxx>
> Cc: Hannes Reinecke <hare@xxxxxxx>
> Cc: Johannes Thumshirn <jthumshirn@xxxxxxx>
> ---
> 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) {
I don't think that's a great comment, what does 'latest request timeout'
refer to? We hit this case when the device has gone idle, I think a more
useful comment would be something about how blk-mq implements timeouts.
How about something ala:
/*
* Request timeouts are handled as a forward rolling timer. If we
* end up here, there are no more requests pending, and there hasn't
* been for a while. Mark each hctx as idle.
*/
--
Jens Axboe
