On 5/25/22 13:20, Martin Wilck wrote:
On Wed, 2022-05-25 at 10:11 +0200, Hannes Reinecke wrote:
When ALUA transitioning timeout triggers the path group state must
be considered invalid. So add a new flag ALUA_PG_FAILED to indicate
that the path state isn't necessarily valid, and keep the existing
path state until we get a valid response from a RTPG.
Cc: Brian Bunker <brian@xxxxxxxxxxxxxxx>
Cc: Martin Wilck <mwilck@xxxxxxx>
Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
---
drivers/scsi/device_handler/scsi_dh_alua.c | 24 +++++++-------------
--
1 file changed, 7 insertions(+), 17 deletions(-)
diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c
b/drivers/scsi/device_handler/scsi_dh_alua.c
index 1d9be771f3ee..6921490a5e65 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -49,6 +49,7 @@
#define ALUA_PG_RUN_RTPG 0x10
#define ALUA_PG_RUN_STPG 0x20
#define ALUA_PG_RUNNING 0x40
+#define ALUA_PG_FAILED 0x80
static uint optimize_stpg;
module_param(optimize_stpg, uint, S_IRUGO|S_IWUSR);
@@ -420,7 +421,7 @@ static enum scsi_disposition
alua_check_sense(struct scsi_device *sdev,
*/
rcu_read_lock();
pg = rcu_dereference(h->pg);
- if (pg)
+ if (pg && !(pg->flags & ALUA_PG_FAILED))
pg->state =
SCSI_ACCESS_STATE_TRANSITIONING;
rcu_read_unlock();
alua_check(sdev, false);
You still return NEEDS_RETRY from alua_check_sense(), even if
ALUA_PG_FAILED is set?
@@ -694,7 +695,7 @@ static int alua_rtpg(struct scsi_device *sdev,
struct alua_port_group *pg)
skip_rtpg:
spin_lock_irqsave(&pg->lock, flags);
- if (transitioning_sense)
+ if (transitioning_sense && !(pg->flags & ALUA_PG_FAILED))
pg->state = SCSI_ACCESS_STATE_TRANSITIONING;
if (group_id_old != pg->group_id || state_old != pg->state ||
@@ -718,23 +719,10 @@ static int alua_rtpg(struct scsi_device *sdev,
struct alua_port_group *pg)
pg->interval = ALUA_RTPG_RETRY_DELAY;
err = SCSI_DH_RETRY;
} else {
- struct alua_dh_data *h;
-
- /* Transitioning time exceeded, set port to
standby */
+ /* Transitioning time exceeded, mark pg as
failed */
err = SCSI_DH_IO;
- pg->state = SCSI_ACCESS_STATE_STANDBY;
+ pg->flags |= ALUA_PG_FAILED;
pg->expiry = 0;
- rcu_read_lock();
- list_for_each_entry_rcu(h, &pg->dh_list,
node) {
- if (!h->sdev)
- continue;
- h->sdev->access_state =
- (pg->state &
SCSI_ACCESS_STATE_MASK);
- if (pg->pref)
- h->sdev->access_state |=
-
SCSI_ACCESS_STATE_PREFE
RRED;
- }
- rcu_read_unlock();
}
break;
case SCSI_ACCESS_STATE_OFFLINE:
@@ -746,6 +734,8 @@ static int alua_rtpg(struct scsi_device *sdev,
struct alua_port_group *pg)
/* Useable path if active */
err = SCSI_DH_OK;
pg->expiry = 0;
+ /* RTPG succeeded, clear ALUA_PG_FAILED */
+ pg->flags &= ~ALUA_PG_FAILED;
Shouldn't this be done for any state except TRANSITIONING?
Why, but it does.
We're only entering this block if the state is not TRANSITIONING.
(It's part of a 'switch' statement)
Btw I've re-read SPC6 and found "The IMPLICIT TRANSITION TIME field
indicates the minimum amount of time in seconds the application client
should wait prior to timing out an implicit state transition (see
5.18.2.3)".
This is unclear to me. "minimum amount of time" suggests that the host
could decide to wait longer until it times out the transition. Worse,
the spec doesn't clearly define when the transition is supposed to have
started. From the host's PoV it makes sense to assume the start time is
when it first encounters either TRANSITIONING from an RTPG, or NOT
READY / 04 / 0a from a regular I/O, which is what we currently do. But
the spec is remarkably unclear about it. Finally, the spec explicitly
says that the timeout applies only to implicit transitions, without
saying what to do in the case of an explicit transition...
Why, but it does; "5.15.2.5 Transitions between target port asymmetric
access states" speaks at length what should happen when transitions
fail. Problem is, a timeout expiring is something outside the spec, so
one can't be sure that the array does what's expected here.
But the one key takeaway is that any port in transitioning is allowed to
ignore TMFs, so any SCSI EH is pointless anyway.
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@xxxxxxx +49 911 74053 688
SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), GF: Felix Imendörffer
