On Tue, Dec 08, 2015 at 08:37:39AM +0100, Hannes Reinecke wrote:
> Track attached SCSI devices and update the 'access_state' field
> whenever an ALUA state change has been detected.
>
> Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
> ---
> drivers/scsi/device_handler/scsi_dh_alua.c | 29 +++++++++++++++++++++++++++++
> 1 file changed, 29 insertions(+)
>
> diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
> index 6c6ff0b..d01c86407 100644
> --- a/drivers/scsi/device_handler/scsi_dh_alua.c
> +++ b/drivers/scsi/device_handler/scsi_dh_alua.c
> @@ -24,6 +24,7 @@
> #include <linux/module.h>
> #include <asm/unaligned.h>
> #include <scsi/scsi.h>
> +#include <scsi/scsi_proto.h>
> #include <scsi/scsi_dbg.h>
> #include <scsi/scsi_eh.h>
> #include <scsi/scsi_dh.h>
> @@ -76,6 +77,7 @@ static struct workqueue_struct *kaluad_wq;
> struct alua_port_group {
> struct kref kref;
> struct list_head node;
> + struct list_head dh_list;
> unsigned char device_id_str[256];
> int device_id_len;
> int group_id;
> @@ -93,6 +95,7 @@ struct alua_port_group {
> };
>
> struct alua_dh_data {
> + struct list_head node;
> struct alua_port_group *pg;
> int rel_port;
> spinlock_t pg_lock;
> @@ -243,6 +246,7 @@ struct alua_port_group *alua_get_pg(struct scsi_device *sdev,
> INIT_DELAYED_WORK(&pg->rtpg_work, alua_rtpg_work);
> INIT_LIST_HEAD(&pg->rtpg_list);
> INIT_LIST_HEAD(&pg->node);
> + INIT_LIST_HEAD(&pg->dh_list);
> spin_lock_init(&pg->lock);
>
> /* Re-check list again to catch concurrent updates */
> @@ -370,13 +374,26 @@ static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h,
> old_pg = pg;
> /* port_group has changed. Update to new port group */
> if (h->pg != pg) {
> + unsigned long flags;
> +
> old_pg = h->pg;
> rcu_assign_pointer(h->pg, pg);
> + spin_lock_irqsave(&old_pg->lock, flags);
> + list_del_rcu(&h->node);
> + spin_unlock_irqrestore(&old_pg->lock, flags);
> + spin_lock_irqsave(&pg->lock, flags);
> + list_add_rcu(&h->node, &pg->dh_list);
> + spin_unlock_irqrestore(&pg->lock, flags);
I think it makes more sense to remove it from the old list
before assining the new h->pg pointer to stay consistant.
Also the add code is not common with the other half of the outer
branch, it would be nice to find a way to share the code between
those two branches.
> list_for_each_entry(tmp_pg, &port_group_list, node) {
> + struct alua_dh_data *h;
> +
> if (tmp_pg->group_id != group_id)
> continue;
> if (tmp_pg->device_id_len != pg->device_id_len)
> @@ -639,6 +658,12 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
> continue;
> tmp_pg->state = desc[0] & 0x0f;
> tmp_pg->pref = desc[0] >> 7;
> + rcu_read_lock();
> + list_for_each_entry_rcu(h, &tmp_pg->dh_list, node) {
> + if (h->sdev)
> + h->sdev->access_state = desc[0];
> + }
> + rcu_read_unlock();
І'd expect h->ѕdev to always be non-NULL. With a little tweak (see below)
that should indeed be the case.
> @@ -1086,6 +1112,9 @@ static void alua_bus_detach(struct scsi_device *sdev)
> h->sdev = NULL;
> spin_unlock(&h->pg_lock);
> if (pg) {
> + spin_lock(&pg->lock);
> + list_del_rcu(&h->node);
> + spin_unlock(&pg->lock);
> synchronize_rcu();
> if (pg->rtpg_sdev)
> flush_delayed_work(&pg->rtpg_work);
Here we'd just need to make sure to do the list_del before setting
h->sdev to NULL.
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