Mike Snitzer wrote:
>
> On Wed, Sep 22 2010 at 6:13am -0400,
> Hannes Reinecke <hare@xxxxxxx> wrote:
>
>> Mike Christie wrote:
>>> On 09/21/2010 02:33 PM, Mike Snitzer wrote:
>>>> 2) the patch also modified alua_rtpg() so implicit ALUA would retry
>>>> (just like explicit ALUA currently does) if TPGS_STATE_TRANSITIONING
>>>> - so why should we avoid retry for implicit but do it for explicit?
>>> Leaving that for Hannes. I cannot think of a reason. Probably just did
>>> not do it.
>> Finally I got around to answering this.
>>
>> I've attached a patch which I made the other day which seems to work
>> reasonably well.
>> Looks better from my side, so if you agree I'll be sending it
>> upstream properly.
>
> Looks good for covering this "2)" change above.
>
> But "1)" change you had concern with (in my previous patch) was that
> alua_prep_fn would return BLKPREP_DEFER if TPGS_STATE_TRANSITIONING.
> This was bad in that FS requests (like the directio path checker) would
> always call ->prep_fn and that if TPGS_STATE_TRANSITIONING the RTPG
> state would never be reevaluated.. leaving us stuck in BLKPREP_DEFER.
>
> Seems I'm missing a new flow that proves this is no longer a concern.
>
The device_handler will keep retrying any path in 'transitioning'.
After ALUA_FAILOVER_TIMEOUT the device handler will either have
updated the port state to something other than 'transitioning' or
returned with 'SCSI_DH_RETRY'.
But yes, you are right; we should be setting the port to something
else than 'transitioning' then. Probably 'standby' is a good choice
here.
New patch attached.
Thanks for the review.
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries & Storage
hare@xxxxxxx +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Markus Rex, HRB 16746 (AG Nürnberg)
>From db02ba3c33a4a1dbfcdc4de1b73e378f7b3d8925 Mon Sep 17 00:00:00 2001
From: Hannes Reinecke <hare@xxxxxxx>
Date: Wed, 22 Sep 2010 12:09:07 +0200
Subject: [PATCH] scsi_dh_alua: Handle all states correctly
For ALUA we should be handling all states, independent of whether
is explicit or implicit. For 'Transitioning' we should be retry
for a certain amount of time; after that we're setting the port
to 'Standby' and return SCSI_DH_RETRY to signal upper layers
a retry is in order here.
Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index 1a970a7..c7e11ed 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -31,6 +31,7 @@
#define TPGS_STATE_NONOPTIMIZED 0x1
#define TPGS_STATE_STANDBY 0x2
#define TPGS_STATE_UNAVAILABLE 0x3
+#define TPGS_STATE_LBA_DEPENDENT 0x4
#define TPGS_STATE_OFFLINE 0xe
#define TPGS_STATE_TRANSITIONING 0xf
@@ -39,6 +40,7 @@
#define TPGS_SUPPORT_NONOPTIMIZED 0x02
#define TPGS_SUPPORT_STANDBY 0x04
#define TPGS_SUPPORT_UNAVAILABLE 0x08
+#define TPGS_SUPPORT_LBA_DEPENDENT 0x10
#define TPGS_SUPPORT_OFFLINE 0x40
#define TPGS_SUPPORT_TRANSITION 0x80
@@ -460,6 +462,8 @@ static char print_alua_state(int state)
return 'S';
case TPGS_STATE_UNAVAILABLE:
return 'U';
+ case TPGS_STATE_LBA_DEPENDENT:
+ return 'L';
case TPGS_STATE_OFFLINE:
return 'O';
case TPGS_STATE_TRANSITIONING:
@@ -542,7 +546,9 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h)
int len, k, off, valid_states = 0;
char *ucp;
unsigned err;
+ unsigned long expiry, interval = 10;
+ expiry = round_jiffies_up(jiffies + ALUA_FAILOVER_TIMEOUT);
retry:
err = submit_rtpg(sdev, h);
@@ -553,7 +559,7 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h)
return SCSI_DH_IO;
err = alua_check_sense(sdev, &sense_hdr);
- if (err == ADD_TO_MLQUEUE)
+ if (err == ADD_TO_MLQUEUE && time_before(jiffies, expiry))
goto retry;
sdev_printk(KERN_INFO, sdev,
"%s: rtpg sense code %02x/%02x/%02x\n",
@@ -587,38 +593,37 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h)
}
sdev_printk(KERN_INFO, sdev,
- "%s: port group %02x state %c supports %c%c%c%c%c%c\n",
+ "%s: port group %02x state %c supports %c%c%c%c%c%c%c\n",
ALUA_DH_NAME, h->group_id, print_alua_state(h->state),
valid_states&TPGS_SUPPORT_TRANSITION?'T':'t',
valid_states&TPGS_SUPPORT_OFFLINE?'O':'o',
+ valid_states&TPGS_SUPPORT_LBA_DEPENDENT?'L':'l',
valid_states&TPGS_SUPPORT_UNAVAILABLE?'U':'u',
valid_states&TPGS_SUPPORT_STANDBY?'S':'s',
valid_states&TPGS_SUPPORT_NONOPTIMIZED?'N':'n',
valid_states&TPGS_SUPPORT_OPTIMIZED?'A':'a');
- if (h->tpgs & TPGS_MODE_EXPLICIT) {
- switch (h->state) {
- case TPGS_STATE_TRANSITIONING:
+ switch (h->state) {
+ case TPGS_STATE_TRANSITIONING:
+ if (time_before(jiffies, expiry)) {
/* State transition, retry */
+ interval *= 10;
+ msleep(interval);
goto retry;
- break;
- case TPGS_STATE_OFFLINE:
- /* Path is offline, fail */
- err = SCSI_DH_DEV_OFFLINED;
- break;
- default:
- break;
}
- } else {
- /* Only Implicit ALUA support */
- if (h->state == TPGS_STATE_OPTIMIZED ||
- h->state == TPGS_STATE_NONOPTIMIZED ||
- h->state == TPGS_STATE_STANDBY)
- /* Useable path if active */
- err = SCSI_DH_OK;
- else
- /* Path unuseable for unavailable/offline */
- err = SCSI_DH_DEV_OFFLINED;
+ /* Transitioning time exceeded, set port to standby */
+ err = SCSI_DH_RETRY;
+ h->state = TPGS_STATE_STANDBY;
+ break;
+ case TPGS_STATE_OFFLINE:
+ case TPGS_STATE_UNAVAILABLE:
+ /* Path unuseable for unavailable/offline */
+ err = SCSI_DH_DEV_OFFLINED;
+ break;
+ default:
+ /* Useable path if active */
+ err = SCSI_DH_OK;
+ break;
}
return err;
}
@@ -672,7 +677,9 @@ static int alua_activate(struct scsi_device *sdev,
goto out;
}
- if (h->tpgs & TPGS_MODE_EXPLICIT && h->state != TPGS_STATE_OPTIMIZED) {
+ if (h->tpgs & TPGS_MODE_EXPLICIT &&
+ h->state != TPGS_STATE_OPTIMIZED &&
+ h->state != TPGS_STATE_LBA_DEPENDENT) {
h->callback_fn = fn;
h->callback_data = data;
err = submit_stpg(h);
@@ -698,8 +705,11 @@ static int alua_prep_fn(struct scsi_device *sdev, struct request *req)
struct alua_dh_data *h = get_alua_data(sdev);
int ret = BLKPREP_OK;
- if (h->state != TPGS_STATE_OPTIMIZED &&
- h->state != TPGS_STATE_NONOPTIMIZED) {
+ if (h->state == TPGS_STATE_TRANSITIONING)
+ ret = BLKPREP_DEFER;
+ else if (h->state != TPGS_STATE_OPTIMIZED &&
+ h->state != TPGS_STATE_NONOPTIMIZED &&
+ h->state != TPGS_STATE_LBA_DEPENDENT) {
ret = BLKPREP_KILL;
req->cmd_flags |= REQ_QUIET;
}
