On 10/6/19 4:45 AM, Ming Lei wrote:
> When all CPUs in one hctx are offline, we shouldn't run this hw queue
> for completing request any more.
>
> So steal bios from the request, and resubmit them, and finally free
> the request in blk_mq_hctx_notify_dead().
>
> Cc: Bart Van Assche <bvanassche@xxxxxxx>
> Cc: Hannes Reinecke <hare@xxxxxxxx>
> Cc: Christoph Hellwig <hch@xxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Keith Busch <keith.busch@xxxxxxxxx>
> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
> ---
> block/blk-mq.c | 48 +++++++++++++++++++++++++++++++++++++++++-------
> 1 file changed, 41 insertions(+), 7 deletions(-)
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index d991c122abf2..0b35fdbd1f17 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -2280,10 +2280,30 @@ static int blk_mq_hctx_notify_online(unsigned int cpu, struct hlist_node *node)
> return 0;
> }
>
> +static void blk_mq_resubmit_io(struct request *rq)
> +{
> + struct bio_list list;
> + struct bio *bio;
> +
> + bio_list_init(&list);
> + blk_steal_bios(&list, rq);
> +
> + while (true) {
> + bio = bio_list_pop(&list);
> + if (!bio)
> + break;
> +
> + generic_make_request(bio);
> + }
> +
> + blk_mq_cleanup_rq(rq);
> + blk_mq_end_request(rq, 0);
> +}
> +
Hmm. Not sure if this is a good idea.
Shouldn't we call 'blk_mq_end_request()' before calling
generic_make_request()?
otherwise the cloned request might be completed before original one,
which looks a bit dodgy to me; and might lead to quite a recursion if we
have several dead cpus to content with ...
Cheers,
Hannes
--
Dr. Hannes Reinecke Teamlead Storage & Networking
hare@xxxxxxx +49 911 74053 688
SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 247165 (AG München), GF: Felix Imendörffer
