On 04/26/2017 08:37 PM, Bart Van Assche wrote:
> Requeuing a request immediately while path initialization is ongoing
> causes high CPU usage, something that is undesired. Hence delay
> requeuing while path initialization is in progress.
>
> Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
> Cc: Hannes Reinecke <hare@xxxxxxxx>
> Cc: Christoph Hellwig <hch@xxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx>
> ---
> drivers/md/dm-mpath.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
> index 6d4333fdddf5..e38c92178746 100644
> --- a/drivers/md/dm-mpath.c
> +++ b/drivers/md/dm-mpath.c
> @@ -322,13 +322,16 @@ static int __pg_init_all_paths(struct multipath *m)
> return atomic_read(&m->pg_init_in_progress);
> }
>
> -static void pg_init_all_paths(struct multipath *m)
> +static int pg_init_all_paths(struct multipath *m)
> {
> unsigned long flags;
> + int ret;
>
> spin_lock_irqsave(&m->lock, flags);
> - __pg_init_all_paths(m);
> + ret = __pg_init_all_paths(m);
> spin_unlock_irqrestore(&m->lock, flags);
> +
> + return ret;
> }
>
> static void __switch_pg(struct multipath *m, struct priority_group *pg)
> @@ -485,7 +488,6 @@ static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
> struct request **__clone)
> {
> struct multipath *m = ti->private;
> - int r = DM_MAPIO_REQUEUE;
> size_t nr_bytes = blk_rq_bytes(rq);
> struct pgpath *pgpath;
> struct block_device *bdev;
> @@ -504,8 +506,8 @@ static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
> return -EIO; /* Failed */
> } else if (test_bit(MPATHF_QUEUE_IO, &m->flags) ||
> test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
> - pg_init_all_paths(m);
> - return r;
> + return pg_init_all_paths(m) == 0 ? DM_MAPIO_REQUEUE :
> + DM_MAPIO_DELAY_REQUEUE;
> }
>
> memset(mpio, 0, sizeof(*mpio));
>
Reviewed-by: Hannes Reinecke <hare@xxxxxxxx>
Cheers,
Hannes
--
Dr. Hannes Reinecke Teamlead Storage & Networking
hare@xxxxxxx +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)
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