On Wed, 2022-11-16 at 13:22 -0800, Bart Van Assche wrote:
> On 11/16/22 02:32, Martin Wilck wrote:
>
>
> [...]
>
> Although I like the approach of this patch, how about the
> implementation below?
> I think the implementation below is a little cleaner but that might
> be subjective ...
>
Fine with me, absolutely, and indeed better than mine. I don't quite
understand the last hook - sdev->handler_data isn't protected by rcu in
any way, is it? But that doesn't matter much.
Regards,
Martin
> Thanks,
>
> Bart.
>
>
> diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c
> b/drivers/scsi/device_handler/scsi_dh_alua.c
> index bd4ee294f5c7..d5a7d6ed5c63 100644
> --- a/drivers/scsi/device_handler/scsi_dh_alua.c
> +++ b/drivers/scsi/device_handler/scsi_dh_alua.c
> @@ -354,6 +354,8 @@ static int alua_check_vpd(struct scsi_device
> *sdev, struct alua_dh_data *h,
> "%s: port group %x rel port %x\n",
> ALUA_DH_NAME, group_id, rel_port);
>
> + kref_get(&pg->kref);
> +
> /* Check for existing port group references */
> spin_lock(&h->pg_lock);
> old_pg = rcu_dereference_protected(h->pg, lockdep_is_held(&h-
> >pg_lock));
> @@ -373,11 +375,11 @@ static int alua_check_vpd(struct scsi_device
> *sdev, struct alua_dh_data *h,
> list_add_rcu(&h->node, &pg->dh_list);
> spin_unlock_irqrestore(&pg->lock, flags);
>
> - alua_rtpg_queue(rcu_dereference_protected(h->pg,
> - lockdep_is_held(&h-
> >pg_lock)),
> - sdev, NULL, true);
> spin_unlock(&h->pg_lock);
>
> + alua_rtpg_queue(pg, sdev, NULL, true);
> + kref_put(&pg->kref, release_port_group);
> +
> if (old_pg)
> kref_put(&old_pg->kref, release_port_group);
>
> @@ -986,6 +988,9 @@ static bool alua_rtpg_queue(struct
> alua_port_group *pg,
> {
> int start_queue = 0;
> unsigned long flags;
> +
> + might_sleep();
> +
> if (WARN_ON_ONCE(!pg) || scsi_device_get(sdev))
> return false;
>
> @@ -996,11 +1001,17 @@ static bool alua_rtpg_queue(struct
> alua_port_group *pg,
> force = true;
> }
> if (pg->rtpg_sdev == NULL) {
> - pg->interval = 0;
> - pg->flags |= ALUA_PG_RUN_RTPG;
> - kref_get(&pg->kref);
> - pg->rtpg_sdev = sdev;
> - start_queue = 1;
> + struct alua_dh_data *h = sdev->handler_data;
> +
> + rcu_read_lock();
> + if (rcu_dereference(h->pg) == pg) {
> + pg->interval = 0;
> + pg->flags |= ALUA_PG_RUN_RTPG;
> + kref_get(&pg->kref);
> + pg->rtpg_sdev = sdev;
> + start_queue = 1;
> + }
> + rcu_read_unlock();
> } else if (!(pg->flags & ALUA_PG_RUN_RTPG) && force) {
> pg->flags |= ALUA_PG_RUN_RTPG;
> /* Do not queue if the worker is already running */
> @@ -1246,8 +1257,8 @@ static void alua_bus_detach(struct scsi_device
> *sdev)
> spin_unlock_irq(&pg->lock);
> kref_put(&pg->kref, release_port_group);
> }
> - sdev->handler_data = NULL;
> synchronize_rcu();
> + sdev->handler_data = NULL;
> kfree(h);
> }
>
