On Fri, 2009-02-20 at 10:33 +0530, Nikanth Karthikesan wrote:
> On Friday 20 February 2009 06:15:29 Chandra Seetharaman wrote:
> > On Thu, 2009-02-19 at 12:40 +0530, Nikanth Karthikesan wrote:
> >
> > <snip>
> >
> > > @@ -431,6 +432,7 @@ static void process_queued_ios(struct work_struct
> > > *work) struct pgpath *pgpath = NULL;
> > > unsigned init_required = 0, must_queue = 1;
> > > unsigned long flags;
> > > + unsigned long delay = 0;
> >
> > I do not see the reason for this variable, you can as well put the delay
> > in pg_init_delay and use it directly (and set it to zero after using
> > it) ?
> >
>
> I missed resetting pg_init_delay to zero after using it. I have attached the
> corrected patch with this. This variable keeps the code cleaner(avoids taking
> m->lock). Also having only a boolean in struct multipath keeps it a bit
> smaller.
Ok. I am fine with your justification.
>
> off-topic:
> I think struct multipath can be shrunk even further by making various flags
> like pg_init_required, pg_init_in_progress, queue_io, queue_if_no_path,
> saved_queue_if_no_path in to a single variable. Thoughts?
As Konrad mentioned, it is worth the cost of readability ?
<snip>
> SCSI Device Handlers return SCSI_DH_IMM_RETRY if we could retry
> immediately and SCSI_DH_RETRY in cases where it is better to retry
> after some delay.
>
> Currently we retry immediately irrespective of SCSI_DH_IMM_RETRY and
> SCSI_DH_RETRY. This patch adds a 2 second delay before retrying to
> activate a device, if it returns SCSI_DH_RETRY.
>
> Signed-off-by: Nikanth Karthikesan <knikanth@xxxxxxx>
Acked-by: Chandra Seetharaman <sekharan@xxxxxxxxxx>
>
> ---
>
> diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
> index 095f77b..7ddf775 100644
> --- a/drivers/md/dm-mpath.c
> +++ b/drivers/md/dm-mpath.c
> @@ -65,12 +65,13 @@ struct multipath {
> spinlock_t lock;
>
> const char *hw_handler_name;
> - struct work_struct activate_path;
> + struct delayed_work activate_path;
> struct pgpath *pgpath_to_activate;
> unsigned nr_priority_groups;
> struct list_head priority_groups;
> unsigned pg_init_required; /* pg_init needs calling? */
> unsigned pg_init_in_progress; /* Only one pg_init allowed at once */
> + unsigned pg_init_delay; /* delay required before retry? */
>
> unsigned nr_valid_paths; /* Total number of usable paths */
> struct pgpath *current_pgpath;
> @@ -203,7 +204,7 @@ static struct multipath *alloc_multipath(struct dm_target *ti)
> m->queue_io = 1;
> INIT_WORK(&m->process_queued_ios, process_queued_ios);
> INIT_WORK(&m->trigger_event, trigger_event);
> - INIT_WORK(&m->activate_path, activate_path);
> + INIT_DELAYED_WORK(&m->activate_path, activate_path);
> m->mpio_pool = mempool_create_slab_pool(MIN_IOS, _mpio_cache);
> if (!m->mpio_pool) {
> kfree(m);
> @@ -431,6 +432,7 @@ static void process_queued_ios(struct work_struct *work)
> struct pgpath *pgpath = NULL;
> unsigned init_required = 0, must_queue = 1;
> unsigned long flags;
> + unsigned long delay = 0;
>
> spin_lock_irqsave(&m->lock, flags);
>
> @@ -452,13 +454,17 @@ static void process_queued_ios(struct work_struct *work)
> m->pg_init_required = 0;
> m->pg_init_in_progress = 1;
> init_required = 1;
> + if (m->pg_init_delay) {
> + delay = SCSI_DH_RETRY_DELAY;
> + m->pg_init_delay = 0;
> + }
> }
>
> out:
> spin_unlock_irqrestore(&m->lock, flags);
>
> if (init_required)
> - queue_work(kmpath_handlerd, &m->activate_path);
> + queue_delayed_work(kmpath_handlerd, &m->activate_path, delay);
>
> if (!must_queue)
> dispatch_queued_ios(m);
> @@ -1060,6 +1066,7 @@ static void pg_init_done(struct dm_path *path, int errors)
> struct priority_group *pg = pgpath->pg;
> struct multipath *m = pg->m;
> unsigned long flags;
> + unsigned delay = 0;
>
> /* device or driver problems */
> switch (errors) {
> @@ -1084,8 +1091,11 @@ static void pg_init_done(struct dm_path *path, int errors)
> */
> bypass_pg(m, pg, 1);
> break;
> - /* TODO: For SCSI_DH_RETRY we should wait a couple seconds */
> + /*
> + * For SCSI_DH_RETRY we wait before retrying.
> + */
> case SCSI_DH_RETRY:
> + delay = 1;
> case SCSI_DH_IMM_RETRY:
> case SCSI_DH_RES_TEMP_UNAVAIL:
> if (pg_init_limit_reached(m, pgpath))
> @@ -1112,6 +1122,7 @@ static void pg_init_done(struct dm_path *path, int errors)
> }
>
> m->pg_init_in_progress = 0;
> + m->pg_init_delay = delay;
> queue_work(kmultipathd, &m->process_queued_ios);
> spin_unlock_irqrestore(&m->lock, flags);
> }
> @@ -1120,7 +1131,7 @@ static void activate_path(struct work_struct *work)
> {
> int ret;
> struct multipath *m =
> - container_of(work, struct multipath, activate_path);
> + container_of(work, struct multipath, activate_path.work);
> struct dm_path *path;
> unsigned long flags;
>
> diff --git a/include/scsi/scsi_dh.h b/include/scsi/scsi_dh.h
> index 33efce2..f099d86 100644
> --- a/include/scsi/scsi_dh.h
> +++ b/include/scsi/scsi_dh.h
> @@ -55,6 +55,10 @@ enum {
> SCSI_DH_NOSYS,
> SCSI_DH_DRIVER_MAX,
> };
> +
> +/* Time to wait before retry in case of SCSI_DH_RETRY */
> +#define SCSI_DH_RETRY_DELAY ((HZ * 2))
> +
> #if defined(CONFIG_SCSI_DH) || defined(CONFIG_SCSI_DH_MODULE)
> extern int scsi_dh_activate(struct request_queue *);
> extern int scsi_dh_handler_exist(const char *);
> �
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