On 07/08/14 02:55, Junichi Nomura wrote:
> pg_ready() checks the current state of the multipath and may return
> false even if a new IO is needed to change the state.
>
> OTOH, if multipath_busy() returns busy, a new IO will not be sent
> to multipath target and the state change won't happen. That results
> in lock up.
>
> The intent of multipath_busy() is to avoid unnecessary cycles of
> dequeue + request_fn + requeue if it is known that multipath device
> will requeue.
>
> Such situation would be:
> - path group is being activated
> - there is no path and the multipath is setup to requeue if no path
>
> This patch should fix the problem introduced as a part of this commit:
> commit e809917735ebf1b9a56c24e877ce0d320baee2ec
> dm mpath: push back requests instead of queueing
>
> diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
> index ebfa411..d58343e 100644
> --- a/drivers/md/dm-mpath.c
> +++ b/drivers/md/dm-mpath.c
> @@ -1620,8 +1620,9 @@ static int multipath_busy(struct dm_target *ti)
>
> spin_lock_irqsave(&m->lock, flags);
>
> - /* pg_init in progress, requeue until done */
> - if (!pg_ready(m)) {
> + /* pg_init in progress or no paths available */
> + if (m->pg_init_in_progress ||
> + (!m->nr_valid_paths && m->queue_if_no_path)) {
> busy = 1;
> goto out;
> }
>
This patch seems to fix the issue reported at the start of this thread -
with this patch applied my test passes.
Thanks !
Bart.
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