[PATCHv8 00/23] ALUA device handler update, part II

[PATCHv8 00/23] ALUA device handler update, part II

[Hannes Reinecke]

As promised here is now the second part of my ALUA device handler update.
This contains a major rework of the ALUA device handler as execution is
moved onto a workqueue. This has the advantage that we avoid having to
do multiple calls to the same LUN (as happens frequently when failing
over a LUN with several paths) and finally retries are handled correctly.
As some arrays are only capable of handling one STPG at a time I've added
a blacklist flag which then uses a singlethreaded workqueue, thereby
effectively synchronize STPG handling.
Thanks to Bart for this suggestion.

The entire patchset can be found at:
git.kernel.org:/hare/scsi-devel/h/alua-2.v8

As usual, comments and reviews are welcome.

Changes to v7:
- Remove SCSI_ACCESS_STATE_UNKNOWN as suggested by Bart
- Fixup typo in pg->flags as suggested by Bart
- Return -EINVAL when reading from access_state and no
  device handler is attached.

Changes to v6:
- Fixup mutex lockdep issue noticed by Bart
- Reshuffle locks in alua_check_vpd

Changes to v5:
- Fixup lock imbalance noticed by Bart
- use #define instead of enum for access_state as suggested by Ewan
- Updated patch description as suggested by Ewan
- Changed occurrences to 'SET TARGET PORT GROUP' as suggested by Bart

Changes to v4:
- use kfree_rcu() as suggested by hch
- Use 'IS_ERR' instead of 'PTR_ERR' when checking for validity
  of a pointer
- Simplify pg assignment as suggested by hch
- Use separate WARN_ON statements a suggested by hch
- Fixes to avoid I/O stall on failover

Changes to v3:
- Use scsi_device flag for blacklisting as suggested by hch
- Add Arrays for synchronous ALUA handling
- Move synchronize_rcu() into release_port_group()
- Add remaining reviewed tags

Changes to v2:
- Use a SCSI blacklist flag instead of a hardware handler parameter
  for switching to synchronous ALUA handling
- Move scsi_get_device_flags{,_keyed} to scsi_devinfo.h
- Move flush_delayed_work() into release_port_group()
- Rename alua_lookup_pg() into alua_find_get_pg()
- Add __rcu annotations to keep sparse happy

Changes to v1:
- Include reviews from hch
- Switch to hardware handler parameter instead of module option

Hannes Reinecke (23):
  scsi_dh_alua: Pass buffer as function argument
  scsi_dh_alua: separate out alua_stpg()
  scsi_dh_alua: Make stpg synchronous
  scsi_dh_alua: call alua_rtpg() if stpg fails
  scsi_dh_alua: switch to scsi_execute_req_flags()
  scsi_dh_alua: allocate RTPG buffer separately
  scsi_dh_alua: Use separate alua_port_group structure
  scsi_dh_alua: use unique device id
  scsi_dh_alua: simplify alua_initialize()
  revert commit a8e5a2d593cb ("[SCSI] scsi_dh_alua: ALUA handler attach
    should succeed while TPG is transitioning")
  scsi_dh_alua: move optimize_stpg evaluation
  scsi_dh_alua: remove 'rel_port' from alua_dh_data structure
  scsi_dh_alua: Use workqueue for RTPG
  scsi_dh_alua: Allow workqueue to run synchronously
  scsi_dh_alua: Add new blacklist flag 'BLIST_SYNC_ALUA'
  scsi_dh_alua: Recheck state on unit attention
  scsi_dh_alua: update all port states
  scsi_dh_alua: Send TEST UNIT READY to poll for transitioning
  scsi_dh: add 'rescan' callback
  scsi: Add 'access_state' attribute
  scsi_dh_alua: use common definitions for ALUA state
  scsi_dh_alua: update 'access_state' field
  scsi_dh_alua: Update version to 2.0

 drivers/scsi/device_handler/scsi_dh_alua.c | 979 ++++++++++++++++++++---------
 drivers/scsi/scsi_devinfo.c                |   2 +
 drivers/scsi/scsi_lib.c                    |   1 +
 drivers/scsi/scsi_scan.c                   |  11 +-
 drivers/scsi/scsi_sysfs.c                  |  53 ++
 include/scsi/scsi_device.h                 |   2 +
 include/scsi/scsi_devinfo.h                |   1 +
 include/scsi/scsi_dh.h                     |   2 +
 include/scsi/scsi_proto.h                  |  12 +
 9 files changed, 756 insertions(+), 307 deletions(-)

-- 
1.8.5.6

[PATCHv8 01/23] scsi_dh_alua: Pass buffer as function argument

[Hannes Reinecke]

Pass in the buffer as a function argument for submit_rtpg().

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index 5a328bf..df71e85 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -135,12 +135,13 @@ static struct request *get_alua_req(struct scsi_device *sdev,
  * submit_rtpg - Issue a REPORT TARGET GROUP STATES command
  * @sdev: sdev the command should be sent to
  */
-static unsigned submit_rtpg(struct scsi_device *sdev, struct alua_dh_data *h)
+static unsigned submit_rtpg(struct scsi_device *sdev, unsigned char *buff,
+			    int bufflen, unsigned char *sense, int flags)
 {
 	struct request *rq;
 	int err = 0;
 
-	rq = get_alua_req(sdev, h->buff, h->bufflen, READ);
+	rq = get_alua_req(sdev, buff, bufflen, READ);
 	if (!rq) {
 		err = DRIVER_BUSY << 24;
 		goto done;
@@ -148,14 +149,14 @@ static unsigned submit_rtpg(struct scsi_device *sdev, struct alua_dh_data *h)
 
 	/* Prepare the command. */
 	rq->cmd[0] = MAINTENANCE_IN;
-	if (!(h->flags & ALUA_RTPG_EXT_HDR_UNSUPP))
+	if (!(flags & ALUA_RTPG_EXT_HDR_UNSUPP))
 		rq->cmd[1] = MI_REPORT_TARGET_PGS | MI_EXT_HDR_PARAM_FMT;
 	else
 		rq->cmd[1] = MI_REPORT_TARGET_PGS;
-	put_unaligned_be32(h->bufflen, &rq->cmd[6]);
+	put_unaligned_be32(bufflen, &rq->cmd[6]);
 	rq->cmd_len = COMMAND_SIZE(MAINTENANCE_IN);
 
-	rq->sense = h->sense;
+	rq->sense = sense;
 	memset(rq->sense, 0, SCSI_SENSE_BUFFERSIZE);
 	rq->sense_len = 0;
 
@@ -446,7 +447,7 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h, int wait_
 		expiry = round_jiffies_up(jiffies + h->transition_tmo * HZ);
 
  retry:
-	retval = submit_rtpg(sdev, h);
+	retval = submit_rtpg(sdev, h->buff, h->bufflen, h->sense, h->flags);
 	if (retval) {
 		if (!scsi_normalize_sense(h->sense, SCSI_SENSE_BUFFERSIZE,
 					  &sense_hdr)) {
-- 
1.8.5.6

[PATCHv8 02/23] scsi_dh_alua: separate out alua_stpg()

[Hannes Reinecke]

Separate out SET TARGET PORT GROUP functionality into a separate
function alua_stpg().

Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 95 +++++++++++++++++++-----------
 1 file changed, 61 insertions(+), 34 deletions(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index df71e85..136bc76 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -579,6 +579,65 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h, int wait_
 }
 
 /*
+ * alua_stpg - Issue a SET TARGET PORT GROUP command
+ *
+ * Issue a SET TARGET PORT GROUP command and evaluate the
+ * response. Returns SCSI_DH_RETRY if the target port group
+ * state is found to be in 'transitioning'.
+ * If SCSI_DH_OK is returned the passed-in 'fn' function
+ * this function will take care of executing 'fn'.
+ * Otherwise 'fn' should be executed by the caller with the
+ * returned error code.
+ */
+static unsigned alua_stpg(struct scsi_device *sdev, struct alua_dh_data *h,
+			  activate_complete fn, void *data)
+{
+	int err = SCSI_DH_OK;
+	int stpg = 0;
+
+	if (!(h->tpgs & TPGS_MODE_EXPLICIT))
+		/* Only implicit ALUA supported */
+		goto out;
+
+	switch (h->state) {
+	case TPGS_STATE_NONOPTIMIZED:
+		stpg = 1;
+		if ((h->flags & ALUA_OPTIMIZE_STPG) &&
+		    !h->pref &&
+		    (h->tpgs & TPGS_MODE_IMPLICIT))
+			stpg = 0;
+		break;
+	case TPGS_STATE_STANDBY:
+	case TPGS_STATE_UNAVAILABLE:
+		stpg = 1;
+		break;
+	case TPGS_STATE_OFFLINE:
+		err = SCSI_DH_IO;
+		break;
+	case TPGS_STATE_TRANSITIONING:
+		err = SCSI_DH_RETRY;
+		break;
+	default:
+		break;
+	}
+
+	if (stpg) {
+		h->callback_fn = fn;
+		h->callback_data = data;
+		err = submit_stpg(h);
+		if (err != SCSI_DH_OK)
+			h->callback_fn = h->callback_data = NULL;
+		else
+			fn = NULL;
+	}
+out:
+	if (fn)
+		fn(data, err);
+
+	return err;
+}
+
+/*
  * alua_initialize - Initialize ALUA state
  * @sdev: the device to be initialized
  *
@@ -655,7 +714,6 @@ static int alua_activate(struct scsi_device *sdev,
 {
 	struct alua_dh_data *h = sdev->handler_data;
 	int err = SCSI_DH_OK;
-	int stpg = 0;
 
 	err = alua_rtpg(sdev, h, 1);
 	if (err != SCSI_DH_OK)
@@ -664,41 +722,10 @@ static int alua_activate(struct scsi_device *sdev,
 	if (optimize_stpg)
 		h->flags |= ALUA_OPTIMIZE_STPG;
 
-	if (h->tpgs & TPGS_MODE_EXPLICIT) {
-		switch (h->state) {
-		case TPGS_STATE_NONOPTIMIZED:
-			stpg = 1;
-			if ((h->flags & ALUA_OPTIMIZE_STPG) &&
-			    (!h->pref) &&
-			    (h->tpgs & TPGS_MODE_IMPLICIT))
-				stpg = 0;
-			break;
-		case TPGS_STATE_STANDBY:
-		case TPGS_STATE_UNAVAILABLE:
-			stpg = 1;
-			break;
-		case TPGS_STATE_OFFLINE:
-			err = SCSI_DH_IO;
-			break;
-		case TPGS_STATE_TRANSITIONING:
-			err = SCSI_DH_RETRY;
-			break;
-		default:
-			break;
-		}
-	}
-
-	if (stpg) {
-		h->callback_fn = fn;
-		h->callback_data = data;
-		err = submit_stpg(h);
-		if (err == SCSI_DH_OK)
-			return 0;
-		h->callback_fn = h->callback_data = NULL;
-	}
+	err = alua_stpg(sdev, h, fn, data);
 
 out:
-	if (fn)
+	if (err != SCSI_DH_OK && fn)
 		fn(data, err);
 	return 0;
 }
-- 
1.8.5.6

[PATCHv8 03/23] scsi_dh_alua: Make stpg synchronous

[Hannes Reinecke]

The 'activate_complete' function needs to be executed after
stpg has finished, so we can as well execute stpg synchronously
and call the function directly.

Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 158 ++++++++++-------------------
 1 file changed, 54 insertions(+), 104 deletions(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index 136bc76..467c2cf 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -169,81 +169,28 @@ done:
 }
 
 /*
- * stpg_endio - Evaluate SET TARGET GROUP STATES
- * @sdev: the device to be evaluated
- * @state: the new target group state
- *
- * Evaluate a SET TARGET GROUP STATES command response.
- */
-static void stpg_endio(struct request *req, int error)
-{
-	struct alua_dh_data *h = req->end_io_data;
-	struct scsi_sense_hdr sense_hdr;
-	unsigned err = SCSI_DH_OK;
-
-	if (host_byte(req->errors) != DID_OK ||
-	    msg_byte(req->errors) != COMMAND_COMPLETE) {
-		err = SCSI_DH_IO;
-		goto done;
-	}
-
-	if (scsi_normalize_sense(h->sense, SCSI_SENSE_BUFFERSIZE,
-				 &sense_hdr)) {
-		if (sense_hdr.sense_key == NOT_READY &&
-		    sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a) {
-			/* ALUA state transition already in progress */
-			err = SCSI_DH_OK;
-			goto done;
-		}
-		if (sense_hdr.sense_key == UNIT_ATTENTION) {
-			err = SCSI_DH_RETRY;
-			goto done;
-		}
-		sdev_printk(KERN_INFO, h->sdev, "%s: stpg failed\n",
-			    ALUA_DH_NAME);
-		scsi_print_sense_hdr(h->sdev, ALUA_DH_NAME, &sense_hdr);
-		err = SCSI_DH_IO;
-	} else if (error)
-		err = SCSI_DH_IO;
-
-	if (err == SCSI_DH_OK) {
-		h->state = TPGS_STATE_OPTIMIZED;
-		sdev_printk(KERN_INFO, h->sdev,
-			    "%s: port group %02x switched to state %c\n",
-			    ALUA_DH_NAME, h->group_id,
-			    print_alua_state(h->state));
-	}
-done:
-	req->end_io_data = NULL;
-	__blk_put_request(req->q, req);
-	if (h->callback_fn) {
-		h->callback_fn(h->callback_data, err);
-		h->callback_fn = h->callback_data = NULL;
-	}
-	return;
-}
-
-/*
- * submit_stpg - Issue a SET TARGET GROUP STATES command
+ * submit_stpg - Issue a SET TARGET PORT GROUP command
  *
  * Currently we're only setting the current target port group state
  * to 'active/optimized' and let the array firmware figure out
  * the states of the remaining groups.
  */
-static unsigned submit_stpg(struct alua_dh_data *h)
+static unsigned submit_stpg(struct scsi_device *sdev, int group_id,
+			    unsigned char *sense)
 {
 	struct request *rq;
+	unsigned char stpg_data[8];
 	int stpg_len = 8;
-	struct scsi_device *sdev = h->sdev;
+	int err = 0;
 
 	/* Prepare the data buffer */
-	memset(h->buff, 0, stpg_len);
-	h->buff[4] = TPGS_STATE_OPTIMIZED & 0x0f;
-	put_unaligned_be16(h->group_id, &h->buff[6]);
+	memset(stpg_data, 0, stpg_len);
+	stpg_data[4] = TPGS_STATE_OPTIMIZED & 0x0f;
+	put_unaligned_be16(group_id, &stpg_data[6]);
 
-	rq = get_alua_req(sdev, h->buff, stpg_len, WRITE);
+	rq = get_alua_req(sdev, stpg_data, stpg_len, WRITE);
 	if (!rq)
-		return SCSI_DH_RES_TEMP_UNAVAIL;
+		return DRIVER_BUSY << 24;
 
 	/* Prepare the command. */
 	rq->cmd[0] = MAINTENANCE_OUT;
@@ -251,13 +198,17 @@ static unsigned submit_stpg(struct alua_dh_data *h)
 	put_unaligned_be32(stpg_len, &rq->cmd[6]);
 	rq->cmd_len = COMMAND_SIZE(MAINTENANCE_OUT);
 
-	rq->sense = h->sense;
+	rq->sense = sense;
 	memset(rq->sense, 0, SCSI_SENSE_BUFFERSIZE);
 	rq->sense_len = 0;
-	rq->end_io_data = h;
 
-	blk_execute_rq_nowait(rq->q, NULL, rq, 1, stpg_endio);
-	return SCSI_DH_OK;
+	blk_execute_rq(rq->q, NULL, rq, 1);
+	if (rq->errors)
+		err = rq->errors;
+
+	blk_put_request(rq);
+
+	return err;
 }
 
 /*
@@ -582,59 +533,59 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h, int wait_
  * alua_stpg - Issue a SET TARGET PORT GROUP command
  *
  * Issue a SET TARGET PORT GROUP command and evaluate the
- * response. Returns SCSI_DH_RETRY if the target port group
- * state is found to be in 'transitioning'.
- * If SCSI_DH_OK is returned the passed-in 'fn' function
- * this function will take care of executing 'fn'.
- * Otherwise 'fn' should be executed by the caller with the
- * returned error code.
+ * response. Returns SCSI_DH_RETRY per default to trigger
+ * a re-evaluation of the target group state or SCSI_DH_OK
+ * if no further action needs to be taken.
  */
-static unsigned alua_stpg(struct scsi_device *sdev, struct alua_dh_data *h,
-			  activate_complete fn, void *data)
+static unsigned alua_stpg(struct scsi_device *sdev, struct alua_dh_data *h)
 {
-	int err = SCSI_DH_OK;
-	int stpg = 0;
-
-	if (!(h->tpgs & TPGS_MODE_EXPLICIT))
-		/* Only implicit ALUA supported */
-		goto out;
+	int retval;
+	struct scsi_sense_hdr sense_hdr;
 
+	if (!(h->tpgs & TPGS_MODE_EXPLICIT)) {
+		/* Only implicit ALUA supported, retry */
+		return SCSI_DH_RETRY;
+	}
 	switch (h->state) {
+	case TPGS_STATE_OPTIMIZED:
+		return SCSI_DH_OK;
 	case TPGS_STATE_NONOPTIMIZED:
-		stpg = 1;
 		if ((h->flags & ALUA_OPTIMIZE_STPG) &&
 		    !h->pref &&
 		    (h->tpgs & TPGS_MODE_IMPLICIT))
-			stpg = 0;
+			return SCSI_DH_OK;
 		break;
 	case TPGS_STATE_STANDBY:
 	case TPGS_STATE_UNAVAILABLE:
-		stpg = 1;
 		break;
 	case TPGS_STATE_OFFLINE:
-		err = SCSI_DH_IO;
-		break;
+		return SCSI_DH_IO;
 	case TPGS_STATE_TRANSITIONING:
-		err = SCSI_DH_RETRY;
 		break;
 	default:
-		break;
+		sdev_printk(KERN_INFO, sdev,
+			    "%s: stpg failed, unhandled TPGS state %d",
+			    ALUA_DH_NAME, h->state);
+		return SCSI_DH_NOSYS;
 	}
+	retval = submit_stpg(sdev, h->group_id, h->sense);
 
-	if (stpg) {
-		h->callback_fn = fn;
-		h->callback_data = data;
-		err = submit_stpg(h);
-		if (err != SCSI_DH_OK)
-			h->callback_fn = h->callback_data = NULL;
-		else
-			fn = NULL;
+	if (retval) {
+		if (!scsi_normalize_sense(h->sense, SCSI_SENSE_BUFFERSIZE,
+					  &sense_hdr)) {
+			sdev_printk(KERN_INFO, sdev,
+				    "%s: stpg failed, result %d",
+				    ALUA_DH_NAME, retval);
+			if (driver_byte(retval) == DRIVER_BUSY)
+				return SCSI_DH_DEV_TEMP_BUSY;
+		} else {
+			sdev_printk(KERN_INFO, h->sdev, "%s: stpg failed\n",
+				    ALUA_DH_NAME);
+			scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
+		}
 	}
-out:
-	if (fn)
-		fn(data, err);
-
-	return err;
+	/* Retry RTPG */
+	return SCSI_DH_RETRY;
 }
 
 /*
@@ -722,10 +673,9 @@ static int alua_activate(struct scsi_device *sdev,
 	if (optimize_stpg)
 		h->flags |= ALUA_OPTIMIZE_STPG;
 
-	err = alua_stpg(sdev, h, fn, data);
-
+	err = alua_stpg(sdev, h);
 out:
-	if (err != SCSI_DH_OK && fn)
+	if (fn)
 		fn(data, err);
 	return 0;
 }
-- 
1.8.5.6

[PATCHv8 04/23] scsi_dh_alua: call alua_rtpg() if stpg fails

[Hannes Reinecke]

If the call to SET TARGET PORT GROUPS fails we have no idea what
state the array is left in, so we need to issue a call to
REPORT TARGET PORT GROUPS in these cases.

Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index 467c2cf..b2a2a77 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -674,6 +674,8 @@ static int alua_activate(struct scsi_device *sdev,
 		h->flags |= ALUA_OPTIMIZE_STPG;
 
 	err = alua_stpg(sdev, h);
+	if (err == SCSI_DH_RETRY)
+		err = alua_rtpg(sdev, h, 1);
 out:
 	if (fn)
 		fn(data, err);
-- 
1.8.5.6

[PATCHv8 05/23] scsi_dh_alua: switch to scsi_execute_req_flags()

[Hannes Reinecke]

All commands are issued synchronously, so no need to open-code
scsi_execute_req_flags() anymore. And we can get rid of the
static sense code structure element. scsi_execute_req_flags()
will be setting REQ_QUIET and REQ_PREEMPT, but that is
perfectly fine as we're evaluating and logging any errors
ourselves and we really need to send the command even if
the device is quiesced.

Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ewan Milne <emilne@redhat.com>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 125 +++++++++--------------------
 1 file changed, 36 insertions(+), 89 deletions(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index b2a2a77..73df60e 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -75,7 +75,6 @@ struct alua_dh_data {
 	unsigned char		*buff;
 	int			bufflen;
 	unsigned char		transition_tmo;
-	unsigned char		sense[SCSI_SENSE_BUFFERSIZE];
 	struct scsi_device	*sdev;
 	activate_complete	callback_fn;
 	void			*callback_data;
@@ -101,71 +100,30 @@ static int realloc_buffer(struct alua_dh_data *h, unsigned len)
 	return 0;
 }
 
-static struct request *get_alua_req(struct scsi_device *sdev,
-				    void *buffer, unsigned buflen, int rw)
-{
-	struct request *rq;
-	struct request_queue *q = sdev->request_queue;
-
-	rq = blk_get_request(q, rw, GFP_NOIO);
-
-	if (IS_ERR(rq)) {
-		sdev_printk(KERN_INFO, sdev,
-			    "%s: blk_get_request failed\n", __func__);
-		return NULL;
-	}
-	blk_rq_set_block_pc(rq);
-
-	if (buflen && blk_rq_map_kern(q, rq, buffer, buflen, GFP_NOIO)) {
-		blk_put_request(rq);
-		sdev_printk(KERN_INFO, sdev,
-			    "%s: blk_rq_map_kern failed\n", __func__);
-		return NULL;
-	}
-
-	rq->cmd_flags |= REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT |
-			 REQ_FAILFAST_DRIVER;
-	rq->retries = ALUA_FAILOVER_RETRIES;
-	rq->timeout = ALUA_FAILOVER_TIMEOUT * HZ;
-
-	return rq;
-}
-
 /*
  * submit_rtpg - Issue a REPORT TARGET GROUP STATES command
  * @sdev: sdev the command should be sent to
  */
-static unsigned submit_rtpg(struct scsi_device *sdev, unsigned char *buff,
-			    int bufflen, unsigned char *sense, int flags)
+static int submit_rtpg(struct scsi_device *sdev, unsigned char *buff,
+		       int bufflen, struct scsi_sense_hdr *sshdr, int flags)
 {
-	struct request *rq;
-	int err = 0;
-
-	rq = get_alua_req(sdev, buff, bufflen, READ);
-	if (!rq) {
-		err = DRIVER_BUSY << 24;
-		goto done;
-	}
+	u8 cdb[COMMAND_SIZE(MAINTENANCE_IN)];
+	int req_flags = REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT |
+		REQ_FAILFAST_DRIVER;
 
 	/* Prepare the command. */
-	rq->cmd[0] = MAINTENANCE_IN;
+	memset(cdb, 0x0, COMMAND_SIZE(MAINTENANCE_IN));
+	cdb[0] = MAINTENANCE_IN;
 	if (!(flags & ALUA_RTPG_EXT_HDR_UNSUPP))
-		rq->cmd[1] = MI_REPORT_TARGET_PGS | MI_EXT_HDR_PARAM_FMT;
+		cdb[1] = MI_REPORT_TARGET_PGS | MI_EXT_HDR_PARAM_FMT;
 	else
-		rq->cmd[1] = MI_REPORT_TARGET_PGS;
-	put_unaligned_be32(bufflen, &rq->cmd[6]);
-	rq->cmd_len = COMMAND_SIZE(MAINTENANCE_IN);
-
-	rq->sense = sense;
-	memset(rq->sense, 0, SCSI_SENSE_BUFFERSIZE);
-	rq->sense_len = 0;
-
-	blk_execute_rq(rq->q, NULL, rq, 1);
-	if (rq->errors)
-		err = rq->errors;
-	blk_put_request(rq);
-done:
-	return err;
+		cdb[1] = MI_REPORT_TARGET_PGS;
+	put_unaligned_be32(bufflen, &cdb[6]);
+
+	return scsi_execute_req_flags(sdev, cdb, DMA_FROM_DEVICE,
+				      buff, bufflen, sshdr,
+				      ALUA_FAILOVER_TIMEOUT * HZ,
+				      ALUA_FAILOVER_RETRIES, NULL, req_flags);
 }
 
 /*
@@ -175,40 +133,30 @@ done:
  * to 'active/optimized' and let the array firmware figure out
  * the states of the remaining groups.
  */
-static unsigned submit_stpg(struct scsi_device *sdev, int group_id,
-			    unsigned char *sense)
+static int submit_stpg(struct scsi_device *sdev, int group_id,
+		       struct scsi_sense_hdr *sshdr)
 {
-	struct request *rq;
+	u8 cdb[COMMAND_SIZE(MAINTENANCE_OUT)];
 	unsigned char stpg_data[8];
 	int stpg_len = 8;
-	int err = 0;
+	int req_flags = REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT |
+		REQ_FAILFAST_DRIVER;
 
 	/* Prepare the data buffer */
 	memset(stpg_data, 0, stpg_len);
 	stpg_data[4] = TPGS_STATE_OPTIMIZED & 0x0f;
 	put_unaligned_be16(group_id, &stpg_data[6]);
 
-	rq = get_alua_req(sdev, stpg_data, stpg_len, WRITE);
-	if (!rq)
-		return DRIVER_BUSY << 24;
-
 	/* Prepare the command. */
-	rq->cmd[0] = MAINTENANCE_OUT;
-	rq->cmd[1] = MO_SET_TARGET_PGS;
-	put_unaligned_be32(stpg_len, &rq->cmd[6]);
-	rq->cmd_len = COMMAND_SIZE(MAINTENANCE_OUT);
-
-	rq->sense = sense;
-	memset(rq->sense, 0, SCSI_SENSE_BUFFERSIZE);
-	rq->sense_len = 0;
-
-	blk_execute_rq(rq->q, NULL, rq, 1);
-	if (rq->errors)
-		err = rq->errors;
-
-	blk_put_request(rq);
-
-	return err;
+	memset(cdb, 0x0, COMMAND_SIZE(MAINTENANCE_OUT));
+	cdb[0] = MAINTENANCE_OUT;
+	cdb[1] = MO_SET_TARGET_PGS;
+	put_unaligned_be32(stpg_len, &cdb[6]);
+
+	return scsi_execute_req_flags(sdev, cdb, DMA_TO_DEVICE,
+				      stpg_data, stpg_len,
+				      sshdr, ALUA_FAILOVER_TIMEOUT * HZ,
+				      ALUA_FAILOVER_RETRIES, NULL, req_flags);
 }
 
 /*
@@ -398,14 +346,14 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h, int wait_
 		expiry = round_jiffies_up(jiffies + h->transition_tmo * HZ);
 
  retry:
-	retval = submit_rtpg(sdev, h->buff, h->bufflen, h->sense, h->flags);
+	retval = submit_rtpg(sdev, h->buff, h->bufflen, &sense_hdr, h->flags);
+
 	if (retval) {
-		if (!scsi_normalize_sense(h->sense, SCSI_SENSE_BUFFERSIZE,
-					  &sense_hdr)) {
+		if (!scsi_sense_valid(&sense_hdr)) {
 			sdev_printk(KERN_INFO, sdev,
 				    "%s: rtpg failed, result %d\n",
 				    ALUA_DH_NAME, retval);
-			if (driver_byte(retval) == DRIVER_BUSY)
+			if (driver_byte(retval) == DRIVER_ERROR)
 				return SCSI_DH_DEV_TEMP_BUSY;
 			return SCSI_DH_IO;
 		}
@@ -568,15 +516,14 @@ static unsigned alua_stpg(struct scsi_device *sdev, struct alua_dh_data *h)
 			    ALUA_DH_NAME, h->state);
 		return SCSI_DH_NOSYS;
 	}
-	retval = submit_stpg(sdev, h->group_id, h->sense);
+	retval = submit_stpg(sdev, h->group_id, &sense_hdr);
 
 	if (retval) {
-		if (!scsi_normalize_sense(h->sense, SCSI_SENSE_BUFFERSIZE,
-					  &sense_hdr)) {
+		if (!scsi_sense_valid(&sense_hdr)) {
 			sdev_printk(KERN_INFO, sdev,
 				    "%s: stpg failed, result %d",
 				    ALUA_DH_NAME, retval);
-			if (driver_byte(retval) == DRIVER_BUSY)
+			if (driver_byte(retval) == DRIVER_ERROR)
 				return SCSI_DH_DEV_TEMP_BUSY;
 		} else {
 			sdev_printk(KERN_INFO, h->sdev, "%s: stpg failed\n",
-- 
1.8.5.6

[PATCHv8 06/23] scsi_dh_alua: allocate RTPG buffer separately

[Hannes Reinecke]

The RTPG buffer will only evaluated within alua_rtpg(),
so we can allocate it locally there and avoid having to
put it into the global structure.

Reviewed-by: Ewan Milne <emilne@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 57 ++++++++++++------------------
 1 file changed, 23 insertions(+), 34 deletions(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index 73df60e..af5acc1 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -56,7 +56,7 @@
 #define TPGS_MODE_IMPLICIT		0x1
 #define TPGS_MODE_EXPLICIT		0x2
 
-#define ALUA_INQUIRY_SIZE		36
+#define ALUA_RTPG_SIZE			128
 #define ALUA_FAILOVER_TIMEOUT		60
 #define ALUA_FAILOVER_RETRIES		5
 
@@ -71,9 +71,6 @@ struct alua_dh_data {
 	int			state;
 	int			pref;
 	unsigned		flags; /* used for optimizing STPG */
-	unsigned char		inq[ALUA_INQUIRY_SIZE];
-	unsigned char		*buff;
-	int			bufflen;
 	unsigned char		transition_tmo;
 	struct scsi_device	*sdev;
 	activate_complete	callback_fn;
@@ -85,21 +82,6 @@ struct alua_dh_data {
 
 static char print_alua_state(int);
 
-static int realloc_buffer(struct alua_dh_data *h, unsigned len)
-{
-	if (h->buff && h->buff != h->inq)
-		kfree(h->buff);
-
-	h->buff = kmalloc(len, GFP_NOIO);
-	if (!h->buff) {
-		h->buff = h->inq;
-		h->bufflen = ALUA_INQUIRY_SIZE;
-		return 1;
-	}
-	h->bufflen = len;
-	return 0;
-}
-
 /*
  * submit_rtpg - Issue a REPORT TARGET GROUP STATES command
  * @sdev: sdev the command should be sent to
@@ -333,8 +315,8 @@ static int alua_check_sense(struct scsi_device *sdev,
 static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h, int wait_for_transition)
 {
 	struct scsi_sense_hdr sense_hdr;
-	int len, k, off, valid_states = 0;
-	unsigned char *ucp;
+	int len, k, off, valid_states = 0, bufflen = ALUA_RTPG_SIZE;
+	unsigned char *ucp, *buff;
 	unsigned err, retval;
 	unsigned long expiry, interval = 0;
 	unsigned int tpg_desc_tbl_off;
@@ -345,14 +327,19 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h, int wait_
 	else
 		expiry = round_jiffies_up(jiffies + h->transition_tmo * HZ);
 
+	buff = kzalloc(bufflen, GFP_KERNEL);
+	if (!buff)
+		return SCSI_DH_DEV_TEMP_BUSY;
+
  retry:
-	retval = submit_rtpg(sdev, h->buff, h->bufflen, &sense_hdr, h->flags);
+	retval = submit_rtpg(sdev, buff, bufflen, &sense_hdr, h->flags);
 
 	if (retval) {
 		if (!scsi_sense_valid(&sense_hdr)) {
 			sdev_printk(KERN_INFO, sdev,
 				    "%s: rtpg failed, result %d\n",
 				    ALUA_DH_NAME, retval);
+			kfree(buff);
 			if (driver_byte(retval) == DRIVER_ERROR)
 				return SCSI_DH_DEV_TEMP_BUSY;
 			return SCSI_DH_IO;
@@ -390,14 +377,18 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h, int wait_
 		sdev_printk(KERN_ERR, sdev, "%s: rtpg failed\n",
 			    ALUA_DH_NAME);
 		scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
+		kfree(buff);
 		return SCSI_DH_IO;
 	}
 
-	len = get_unaligned_be32(&h->buff[0]) + 4;
+	len = get_unaligned_be32(&buff[0]) + 4;
 
-	if (len > h->bufflen) {
+	if (len > bufflen) {
 		/* Resubmit with the correct length */
-		if (realloc_buffer(h, len)) {
+		kfree(buff);
+		bufflen = len;
+		buff = kmalloc(bufflen, GFP_KERNEL);
+		if (!buff) {
 			sdev_printk(KERN_WARNING, sdev,
 				    "%s: kmalloc buffer failed\n",__func__);
 			/* Temporary failure, bypass */
@@ -407,24 +398,25 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h, int wait_
 	}
 
 	orig_transition_tmo = h->transition_tmo;
-	if ((h->buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR && h->buff[5] != 0)
-		h->transition_tmo = h->buff[5];
+	if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR && buff[5] != 0)
+		h->transition_tmo = buff[5];
 	else
 		h->transition_tmo = ALUA_FAILOVER_TIMEOUT;
 
-	if (wait_for_transition && (orig_transition_tmo != h->transition_tmo)) {
+	if (wait_for_transition &&
+	    (orig_transition_tmo != h->transition_tmo)) {
 		sdev_printk(KERN_INFO, sdev,
 			    "%s: transition timeout set to %d seconds\n",
 			    ALUA_DH_NAME, h->transition_tmo);
 		expiry = jiffies + h->transition_tmo * HZ;
 	}
 
-	if ((h->buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR)
+	if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR)
 		tpg_desc_tbl_off = 8;
 	else
 		tpg_desc_tbl_off = 4;
 
-	for (k = tpg_desc_tbl_off, ucp = h->buff + tpg_desc_tbl_off;
+	for (k = tpg_desc_tbl_off, ucp = buff + tpg_desc_tbl_off;
 	     k < len;
 	     k += off, ucp += off) {
 
@@ -474,6 +466,7 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h, int wait_
 		err = SCSI_DH_OK;
 		break;
 	}
+	kfree(buff);
 	return err;
 }
 
@@ -668,8 +661,6 @@ static int alua_bus_attach(struct scsi_device *sdev)
 	h->state = TPGS_STATE_OPTIMIZED;
 	h->group_id = -1;
 	h->rel_port = -1;
-	h->buff = h->inq;
-	h->bufflen = ALUA_INQUIRY_SIZE;
 	h->sdev = sdev;
 
 	err = alua_initialize(sdev, h);
@@ -691,8 +682,6 @@ static void alua_bus_detach(struct scsi_device *sdev)
 {
 	struct alua_dh_data *h = sdev->handler_data;
 
-	if (h->buff && h->inq != h->buff)
-		kfree(h->buff);
 	sdev->handler_data = NULL;
 	kfree(h);
 }
-- 
1.8.5.6

[PATCHv8 07/23] scsi_dh_alua: Use separate alua_port_group structure

[Hannes Reinecke]

The port group needs to be a separate structure as several
LUNs might belong to the same group.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ewan Milne <emilne@redhat.com>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 181 ++++++++++++++++++++---------
 include/scsi/scsi_dh.h                     |   1 +
 2 files changed, 129 insertions(+), 53 deletions(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index af5acc1..e9fb760 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -64,14 +64,24 @@
 #define ALUA_OPTIMIZE_STPG		1
 #define ALUA_RTPG_EXT_HDR_UNSUPP	2
 
-struct alua_dh_data {
+static LIST_HEAD(port_group_list);
+static DEFINE_SPINLOCK(port_group_lock);
+
+struct alua_port_group {
+	struct kref		kref;
+	struct list_head	node;
 	int			group_id;
-	int			rel_port;
 	int			tpgs;
 	int			state;
 	int			pref;
 	unsigned		flags; /* used for optimizing STPG */
 	unsigned char		transition_tmo;
+};
+
+struct alua_dh_data {
+	struct alua_port_group	*pg;
+	int			group_id;
+	int			rel_port;
 	struct scsi_device	*sdev;
 	activate_complete	callback_fn;
 	void			*callback_data;
@@ -82,6 +92,17 @@ struct alua_dh_data {
 
 static char print_alua_state(int);
 
+static void release_port_group(struct kref *kref)
+{
+	struct alua_port_group *pg;
+
+	pg = container_of(kref, struct alua_port_group, kref);
+	spin_lock(&port_group_lock);
+	list_del(&pg->node);
+	spin_unlock(&port_group_lock);
+	kfree(pg);
+}
+
 /*
  * submit_rtpg - Issue a REPORT TARGET GROUP STATES command
  * @sdev: sdev the command should be sent to
@@ -142,6 +163,35 @@ static int submit_stpg(struct scsi_device *sdev, int group_id,
 }
 
 /*
+ * alua_alloc_pg - Allocate a new port_group structure
+ * @sdev: scsi device
+ * @h: alua device_handler data
+ * @group_id: port group id
+ *
+ * Allocate a new port_group structure for a given
+ * device.
+ */
+struct alua_port_group *alua_alloc_pg(struct scsi_device *sdev,
+				      int group_id, int tpgs)
+{
+	struct alua_port_group *pg;
+
+	pg = kzalloc(sizeof(struct alua_port_group), GFP_KERNEL);
+	if (!pg)
+		return NULL;
+
+	pg->group_id = group_id;
+	pg->tpgs = tpgs;
+	pg->state = TPGS_STATE_OPTIMIZED;
+	kref_init(&pg->kref);
+	spin_lock(&port_group_lock);
+	list_add(&pg->node, &port_group_list);
+	spin_unlock(&port_group_lock);
+
+	return pg;
+}
+
+/*
  * alua_check_tpgs - Evaluate TPGS setting
  * @sdev: device to be checked
  *
@@ -216,7 +266,6 @@ static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h)
 			    ALUA_DH_NAME);
 		return SCSI_DH_DEV_UNSUPP;
 	}
-	h->state = TPGS_STATE_OPTIMIZED;
 	h->group_id = group_id;
 
 	sdev_printk(KERN_INFO, sdev,
@@ -312,7 +361,7 @@ static int alua_check_sense(struct scsi_device *sdev,
  * Returns SCSI_DH_DEV_OFFLINED if the path is
  * found to be unusable.
  */
-static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h, int wait_for_transition)
+static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg, int wait_for_transition)
 {
 	struct scsi_sense_hdr sense_hdr;
 	int len, k, off, valid_states = 0, bufflen = ALUA_RTPG_SIZE;
@@ -322,17 +371,17 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h, int wait_
 	unsigned int tpg_desc_tbl_off;
 	unsigned char orig_transition_tmo;
 
-	if (!h->transition_tmo)
+	if (!pg->transition_tmo)
 		expiry = round_jiffies_up(jiffies + ALUA_FAILOVER_TIMEOUT * HZ);
 	else
-		expiry = round_jiffies_up(jiffies + h->transition_tmo * HZ);
+		expiry = round_jiffies_up(jiffies + pg->transition_tmo * HZ);
 
 	buff = kzalloc(bufflen, GFP_KERNEL);
 	if (!buff)
 		return SCSI_DH_DEV_TEMP_BUSY;
 
  retry:
-	retval = submit_rtpg(sdev, buff, bufflen, &sense_hdr, h->flags);
+	retval = submit_rtpg(sdev, buff, bufflen, &sense_hdr, pg->flags);
 
 	if (retval) {
 		if (!scsi_sense_valid(&sense_hdr)) {
@@ -353,10 +402,10 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h, int wait_
 		 * The retry without rtpg_ext_hdr_req set
 		 * handles this.
 		 */
-		if (!(h->flags & ALUA_RTPG_EXT_HDR_UNSUPP) &&
+		if (!(pg->flags & ALUA_RTPG_EXT_HDR_UNSUPP) &&
 		    sense_hdr.sense_key == ILLEGAL_REQUEST &&
 		    sense_hdr.asc == 0x24 && sense_hdr.ascq == 0) {
-			h->flags |= ALUA_RTPG_EXT_HDR_UNSUPP;
+			pg->flags |= ALUA_RTPG_EXT_HDR_UNSUPP;
 			goto retry;
 		}
 		/*
@@ -397,18 +446,18 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h, int wait_
 		goto retry;
 	}
 
-	orig_transition_tmo = h->transition_tmo;
+	orig_transition_tmo = pg->transition_tmo;
 	if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR && buff[5] != 0)
-		h->transition_tmo = buff[5];
+		pg->transition_tmo = buff[5];
 	else
-		h->transition_tmo = ALUA_FAILOVER_TIMEOUT;
+		pg->transition_tmo = ALUA_FAILOVER_TIMEOUT;
 
 	if (wait_for_transition &&
-	    (orig_transition_tmo != h->transition_tmo)) {
+	    (orig_transition_tmo != pg->transition_tmo)) {
 		sdev_printk(KERN_INFO, sdev,
 			    "%s: transition timeout set to %d seconds\n",
-			    ALUA_DH_NAME, h->transition_tmo);
-		expiry = jiffies + h->transition_tmo * HZ;
+			    ALUA_DH_NAME, pg->transition_tmo);
+		expiry = jiffies + pg->transition_tmo * HZ;
 	}
 
 	if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR)
@@ -420,9 +469,9 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h, int wait_
 	     k < len;
 	     k += off, ucp += off) {
 
-		if (h->group_id == get_unaligned_be16(&ucp[2])) {
-			h->state = ucp[0] & 0x0f;
-			h->pref = ucp[0] >> 7;
+		if (pg->group_id == get_unaligned_be16(&ucp[2])) {
+			pg->state = ucp[0] & 0x0f;
+			pg->pref = ucp[0] >> 7;
 			valid_states = ucp[1];
 		}
 		off = 8 + (ucp[7] * 4);
@@ -430,8 +479,8 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h, int wait_
 
 	sdev_printk(KERN_INFO, sdev,
 		    "%s: port group %02x state %c %s supports %c%c%c%c%c%c%c\n",
-		    ALUA_DH_NAME, h->group_id, print_alua_state(h->state),
-		    h->pref ? "preferred" : "non-preferred",
+		    ALUA_DH_NAME, pg->group_id, print_alua_state(pg->state),
+		    pg->pref ? "preferred" : "non-preferred",
 		    valid_states&TPGS_SUPPORT_TRANSITION?'T':'t',
 		    valid_states&TPGS_SUPPORT_OFFLINE?'O':'o',
 		    valid_states&TPGS_SUPPORT_LBA_DEPENDENT?'L':'l',
@@ -440,7 +489,7 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h, int wait_
 		    valid_states&TPGS_SUPPORT_NONOPTIMIZED?'N':'n',
 		    valid_states&TPGS_SUPPORT_OPTIMIZED?'A':'a');
 
-	switch (h->state) {
+	switch (pg->state) {
 	case TPGS_STATE_TRANSITIONING:
 		if (wait_for_transition) {
 			if (time_before(jiffies, expiry)) {
@@ -455,7 +504,7 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h, int wait_
 		}
 
 		/* Transitioning time exceeded, set port to standby */
-		h->state = TPGS_STATE_STANDBY;
+		pg->state = TPGS_STATE_STANDBY;
 		break;
 	case TPGS_STATE_OFFLINE:
 		/* Path unusable */
@@ -478,22 +527,22 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h, int wait_
  * a re-evaluation of the target group state or SCSI_DH_OK
  * if no further action needs to be taken.
  */
-static unsigned alua_stpg(struct scsi_device *sdev, struct alua_dh_data *h)
+static unsigned alua_stpg(struct scsi_device *sdev, struct alua_port_group *pg)
 {
 	int retval;
 	struct scsi_sense_hdr sense_hdr;
 
-	if (!(h->tpgs & TPGS_MODE_EXPLICIT)) {
+	if (!(pg->tpgs & TPGS_MODE_EXPLICIT)) {
 		/* Only implicit ALUA supported, retry */
 		return SCSI_DH_RETRY;
 	}
-	switch (h->state) {
+	switch (pg->state) {
 	case TPGS_STATE_OPTIMIZED:
 		return SCSI_DH_OK;
 	case TPGS_STATE_NONOPTIMIZED:
-		if ((h->flags & ALUA_OPTIMIZE_STPG) &&
-		    !h->pref &&
-		    (h->tpgs & TPGS_MODE_IMPLICIT))
+		if ((pg->flags & ALUA_OPTIMIZE_STPG) &&
+		    !pg->pref &&
+		    (pg->tpgs & TPGS_MODE_IMPLICIT))
 			return SCSI_DH_OK;
 		break;
 	case TPGS_STATE_STANDBY:
@@ -506,10 +555,10 @@ static unsigned alua_stpg(struct scsi_device *sdev, struct alua_dh_data *h)
 	default:
 		sdev_printk(KERN_INFO, sdev,
 			    "%s: stpg failed, unhandled TPGS state %d",
-			    ALUA_DH_NAME, h->state);
+			    ALUA_DH_NAME, pg->state);
 		return SCSI_DH_NOSYS;
 	}
-	retval = submit_stpg(sdev, h->group_id, &sense_hdr);
+	retval = submit_stpg(sdev, pg->group_id, &sense_hdr);
 
 	if (retval) {
 		if (!scsi_sense_valid(&sense_hdr)) {
@@ -519,7 +568,7 @@ static unsigned alua_stpg(struct scsi_device *sdev, struct alua_dh_data *h)
 			if (driver_byte(retval) == DRIVER_ERROR)
 				return SCSI_DH_DEV_TEMP_BUSY;
 		} else {
-			sdev_printk(KERN_INFO, h->sdev, "%s: stpg failed\n",
+			sdev_printk(KERN_INFO, sdev, "%s: stpg failed\n",
 				    ALUA_DH_NAME);
 			scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
 		}
@@ -537,20 +586,24 @@ static unsigned alua_stpg(struct scsi_device *sdev, struct alua_dh_data *h)
  */
 static int alua_initialize(struct scsi_device *sdev, struct alua_dh_data *h)
 {
-	int err = SCSI_DH_DEV_UNSUPP;
+	int err = SCSI_DH_DEV_UNSUPP, tpgs;
 
-	h->tpgs = alua_check_tpgs(sdev);
-	if (h->tpgs == TPGS_MODE_NONE)
+	tpgs = alua_check_tpgs(sdev);
+	if (tpgs == TPGS_MODE_NONE)
 		goto out;
 
 	err = alua_check_vpd(sdev, h);
 	if (err != SCSI_DH_OK)
 		goto out;
 
-	err = alua_rtpg(sdev, h, 0);
-	if (err != SCSI_DH_OK)
+	h->pg = alua_alloc_pg(sdev, h->group_id, tpgs);
+	if (!h->pg) {
+		err = SCSI_DH_NOMEM;
 		goto out;
-
+	}
+	kref_get(&h->pg->kref);
+	err = alua_rtpg(sdev, h->pg, 0);
+	kref_put(&h->pg->kref, release_port_group);
 out:
 	return err;
 }
@@ -566,6 +619,7 @@ out:
 static int alua_set_params(struct scsi_device *sdev, const char *params)
 {
 	struct alua_dh_data *h = sdev->handler_data;
+	struct alua_port_group *pg = NULL;
 	unsigned int optimize = 0, argc;
 	const char *p = params;
 	int result = SCSI_DH_OK;
@@ -578,10 +632,14 @@ static int alua_set_params(struct scsi_device *sdev, const char *params)
 	if ((sscanf(p, "%u", &optimize) != 1) || (optimize > 1))
 		return -EINVAL;
 
+	pg = h->pg;
+	if (!pg)
+		return -ENXIO;
+
 	if (optimize)
-		h->flags |= ALUA_OPTIMIZE_STPG;
+		pg->flags |= ALUA_OPTIMIZE_STPG;
 	else
-		h->flags &= ~ALUA_OPTIMIZE_STPG;
+		pg->flags &= ~ALUA_OPTIMIZE_STPG;
 
 	return result;
 }
@@ -606,16 +664,23 @@ static int alua_activate(struct scsi_device *sdev,
 	struct alua_dh_data *h = sdev->handler_data;
 	int err = SCSI_DH_OK;
 
-	err = alua_rtpg(sdev, h, 1);
-	if (err != SCSI_DH_OK)
+	if (!h->pg)
 		goto out;
 
+	kref_get(&h->pg->kref);
+
 	if (optimize_stpg)
-		h->flags |= ALUA_OPTIMIZE_STPG;
+		h->pg->flags |= ALUA_OPTIMIZE_STPG;
 
-	err = alua_stpg(sdev, h);
+	err = alua_rtpg(sdev, h->pg, 1);
+	if (err != SCSI_DH_OK) {
+		kref_put(&h->pg->kref, release_port_group);
+		goto out;
+	}
+	err = alua_stpg(sdev, h->pg);
 	if (err == SCSI_DH_RETRY)
-		err = alua_rtpg(sdev, h, 1);
+		err = alua_rtpg(sdev, h->pg, 1);
+	kref_put(&h->pg->kref, release_port_group);
 out:
 	if (fn)
 		fn(data, err);
@@ -631,13 +696,19 @@ out:
 static int alua_prep_fn(struct scsi_device *sdev, struct request *req)
 {
 	struct alua_dh_data *h = sdev->handler_data;
+	int state;
 	int ret = BLKPREP_OK;
 
-	if (h->state == TPGS_STATE_TRANSITIONING)
+	if (!h->pg)
+		return ret;
+	kref_get(&h->pg->kref);
+	state = h->pg->state;
+	kref_put(&h->pg->kref, release_port_group);
+	if (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) {
+	else if (state != TPGS_STATE_OPTIMIZED &&
+		 state != TPGS_STATE_NONOPTIMIZED &&
+		 state != TPGS_STATE_LBA_DEPENDENT) {
 		ret = BLKPREP_KILL;
 		req->cmd_flags |= REQ_QUIET;
 	}
@@ -652,18 +723,18 @@ static int alua_prep_fn(struct scsi_device *sdev, struct request *req)
 static int alua_bus_attach(struct scsi_device *sdev)
 {
 	struct alua_dh_data *h;
-	int err;
+	int err, ret = -EINVAL;
 
 	h = kzalloc(sizeof(*h) , GFP_KERNEL);
 	if (!h)
 		return -ENOMEM;
-	h->tpgs = TPGS_MODE_UNINITIALIZED;
-	h->state = TPGS_STATE_OPTIMIZED;
-	h->group_id = -1;
+	h->pg = NULL;
 	h->rel_port = -1;
 	h->sdev = sdev;
 
 	err = alua_initialize(sdev, h);
+	if (err == SCSI_DH_NOMEM)
+		ret = -ENOMEM;
 	if (err != SCSI_DH_OK && err != SCSI_DH_DEV_OFFLINED)
 		goto failed;
 
@@ -671,7 +742,7 @@ static int alua_bus_attach(struct scsi_device *sdev)
 	return 0;
 failed:
 	kfree(h);
-	return -EINVAL;
+	return ret;
 }
 
 /*
@@ -682,6 +753,10 @@ static void alua_bus_detach(struct scsi_device *sdev)
 {
 	struct alua_dh_data *h = sdev->handler_data;
 
+	if (h->pg) {
+		kref_put(&h->pg->kref, release_port_group);
+		h->pg = NULL;
+	}
 	sdev->handler_data = NULL;
 	kfree(h);
 }
diff --git a/include/scsi/scsi_dh.h b/include/scsi/scsi_dh.h
index 85d7317..7e184c6 100644
--- a/include/scsi/scsi_dh.h
+++ b/include/scsi/scsi_dh.h
@@ -52,6 +52,7 @@ enum {
 	SCSI_DH_TIMED_OUT,
 	SCSI_DH_RES_TEMP_UNAVAIL,
 	SCSI_DH_DEV_OFFLINED,
+	SCSI_DH_NOMEM,
 	SCSI_DH_NOSYS,
 	SCSI_DH_DRIVER_MAX,
 };
-- 
1.8.5.6

[PATCHv8 08/23] scsi_dh_alua: use unique device id

[Hannes Reinecke]

Use scsi_vpd_lun_id() to assign a unique device identification
to the alua port group structure.

Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 55 +++++++++++++++++++++++++++---
 1 file changed, 50 insertions(+), 5 deletions(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index e9fb760..0bcd901 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -70,6 +70,8 @@ static DEFINE_SPINLOCK(port_group_lock);
 struct alua_port_group {
 	struct kref		kref;
 	struct list_head	node;
+	unsigned char		device_id_str[256];
+	int			device_id_len;
 	int			group_id;
 	int			tpgs;
 	int			state;
@@ -162,6 +164,26 @@ static int submit_stpg(struct scsi_device *sdev, int group_id,
 				      ALUA_FAILOVER_RETRIES, NULL, req_flags);
 }
 
+struct alua_port_group *alua_find_get_pg(char *id_str, size_t id_size,
+					 int group_id)
+{
+	struct alua_port_group *pg;
+
+	list_for_each_entry(pg, &port_group_list, node) {
+		if (pg->group_id != group_id)
+			continue;
+		if (pg->device_id_len != id_size)
+			continue;
+		if (strncmp(pg->device_id_str, id_str, id_size))
+			continue;
+		if (!kref_get_unless_zero(&pg->kref))
+			continue;
+		return pg;
+	}
+
+	return NULL;
+}
+
 /*
  * alua_alloc_pg - Allocate a new port_group structure
  * @sdev: scsi device
@@ -174,17 +196,39 @@ static int submit_stpg(struct scsi_device *sdev, int group_id,
 struct alua_port_group *alua_alloc_pg(struct scsi_device *sdev,
 				      int group_id, int tpgs)
 {
-	struct alua_port_group *pg;
+	struct alua_port_group *pg, *tmp_pg;
 
 	pg = kzalloc(sizeof(struct alua_port_group), GFP_KERNEL);
 	if (!pg)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
+	pg->device_id_len = scsi_vpd_lun_id(sdev, pg->device_id_str,
+					    sizeof(pg->device_id_str));
+	if (pg->device_id_len <= 0) {
+		/*
+		 * Internal error: TPGS supported but no device
+		 * identifcation found. Disable ALUA support.
+		 */
+		kfree(pg);
+		sdev_printk(KERN_INFO, sdev,
+			    "%s: No device descriptors found\n",
+			    ALUA_DH_NAME);
+		return ERR_PTR(-ENXIO);
+	}
 	pg->group_id = group_id;
 	pg->tpgs = tpgs;
 	pg->state = TPGS_STATE_OPTIMIZED;
 	kref_init(&pg->kref);
+
 	spin_lock(&port_group_lock);
+	tmp_pg = alua_find_get_pg(pg->device_id_str, pg->device_id_len,
+				  group_id);
+	if (tmp_pg) {
+		spin_unlock(&port_group_lock);
+		kfree(pg);
+		return tmp_pg;
+	}
+
 	list_add(&pg->node, &port_group_list);
 	spin_unlock(&port_group_lock);
 
@@ -269,7 +313,7 @@ static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h)
 	h->group_id = group_id;
 
 	sdev_printk(KERN_INFO, sdev,
-		    "%s: port group %02x rel port %02x\n",
+		    "%s: port group %x rel port %x\n",
 		    ALUA_DH_NAME, h->group_id, h->rel_port);
 
 	return 0;
@@ -597,8 +641,9 @@ static int alua_initialize(struct scsi_device *sdev, struct alua_dh_data *h)
 		goto out;
 
 	h->pg = alua_alloc_pg(sdev, h->group_id, tpgs);
-	if (!h->pg) {
-		err = SCSI_DH_NOMEM;
+	if (IS_ERR(h->pg)) {
+		if (PTR_ERR(h->pg) == -ENOMEM)
+			err = SCSI_DH_NOMEM;
 		goto out;
 	}
 	kref_get(&h->pg->kref);
-- 
1.8.5.6

[PATCHv8 09/23] scsi_dh_alua: simplify alua_initialize()

[Hannes Reinecke]

Rework alua_check_vpd() to use scsi_vpd_get_tpg()
and move the port group selection into the function, too.
With that we can simplify alua_initialize() to just
call alua_check_tpgs() and alua_check_vpd();

Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 38 +++++++++++++-----------------
 1 file changed, 17 insertions(+), 21 deletions(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index 0bcd901..a6fe3ae 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -92,6 +92,7 @@ struct alua_dh_data {
 #define ALUA_POLICY_SWITCH_CURRENT	0
 #define ALUA_POLICY_SWITCH_ALL		1
 
+static int alua_rtpg(struct scsi_device *, struct alua_port_group *, int);
 static char print_alua_state(int);
 
 static void release_port_group(struct kref *kref)
@@ -294,7 +295,8 @@ static int alua_check_tpgs(struct scsi_device *sdev)
  * Extract the relative target port and the target port group
  * descriptor from the list of identificators.
  */
-static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h)
+static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h,
+			  int tpgs)
 {
 	int rel_port = -1, group_id;
 
@@ -310,13 +312,21 @@ static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h)
 			    ALUA_DH_NAME);
 		return SCSI_DH_DEV_UNSUPP;
 	}
-	h->group_id = group_id;
+
+	h->pg = alua_alloc_pg(sdev, group_id, tpgs);
+	if (IS_ERR(h->pg)) {
+		if (PTR_ERR(h->pg) == -ENOMEM)
+			return SCSI_DH_NOMEM;
+		return SCSI_DH_DEV_UNSUPP;
+	}
+	h->rel_port = rel_port;
 
 	sdev_printk(KERN_INFO, sdev,
-		    "%s: port group %x rel port %x\n",
-		    ALUA_DH_NAME, h->group_id, h->rel_port);
+		    "%s: device %s port group %x rel port %x\n",
+		    ALUA_DH_NAME, h->pg->device_id_str,
+		    h->group_id, h->rel_port);
 
-	return 0;
+	return alua_rtpg(sdev, h->pg, 0);
 }
 
 static char print_alua_state(int state)
@@ -633,23 +643,9 @@ static int alua_initialize(struct scsi_device *sdev, struct alua_dh_data *h)
 	int err = SCSI_DH_DEV_UNSUPP, tpgs;
 
 	tpgs = alua_check_tpgs(sdev);
-	if (tpgs == TPGS_MODE_NONE)
-		goto out;
-
-	err = alua_check_vpd(sdev, h);
-	if (err != SCSI_DH_OK)
-		goto out;
+	if (tpgs != TPGS_MODE_NONE)
+		err = alua_check_vpd(sdev, h, tpgs);
 
-	h->pg = alua_alloc_pg(sdev, h->group_id, tpgs);
-	if (IS_ERR(h->pg)) {
-		if (PTR_ERR(h->pg) == -ENOMEM)
-			err = SCSI_DH_NOMEM;
-		goto out;
-	}
-	kref_get(&h->pg->kref);
-	err = alua_rtpg(sdev, h->pg, 0);
-	kref_put(&h->pg->kref, release_port_group);
-out:
 	return err;
 }
 /*
-- 
1.8.5.6

[PATCHv8 10/23] revert commit a8e5a2d593cb ("[SCSI] scsi_dh_alua: ALUA handler attach should succeed while TPG is transitioning")

[Hannes Reinecke]

This reverts commit a8e5a2d593cbfccf530c3382c2c328d2edaa7b66

Obsoleted by the next patch.

Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ewan Milne <emilne@redhat.com>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 31 ++++++++++++------------------
 1 file changed, 12 insertions(+), 19 deletions(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index a6fe3ae..0ae2536 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -92,7 +92,7 @@ struct alua_dh_data {
 #define ALUA_POLICY_SWITCH_CURRENT	0
 #define ALUA_POLICY_SWITCH_ALL		1
 
-static int alua_rtpg(struct scsi_device *, struct alua_port_group *, int);
+static int alua_rtpg(struct scsi_device *, struct alua_port_group *);
 static char print_alua_state(int);
 
 static void release_port_group(struct kref *kref)
@@ -326,7 +326,7 @@ static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h,
 		    ALUA_DH_NAME, h->pg->device_id_str,
 		    h->group_id, h->rel_port);
 
-	return alua_rtpg(sdev, h->pg, 0);
+	return alua_rtpg(sdev, h->pg);
 }
 
 static char print_alua_state(int state)
@@ -409,13 +409,12 @@ static int alua_check_sense(struct scsi_device *sdev,
 /*
  * alua_rtpg - Evaluate REPORT TARGET GROUP STATES
  * @sdev: the device to be evaluated.
- * @wait_for_transition: if nonzero, wait ALUA_FAILOVER_TIMEOUT seconds for device to exit transitioning state
  *
  * Evaluate the Target Port Group State.
  * Returns SCSI_DH_DEV_OFFLINED if the path is
  * found to be unusable.
  */
-static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg, int wait_for_transition)
+static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
 {
 	struct scsi_sense_hdr sense_hdr;
 	int len, k, off, valid_states = 0, bufflen = ALUA_RTPG_SIZE;
@@ -506,8 +505,7 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg, int w
 	else
 		pg->transition_tmo = ALUA_FAILOVER_TIMEOUT;
 
-	if (wait_for_transition &&
-	    (orig_transition_tmo != pg->transition_tmo)) {
+	if (orig_transition_tmo != pg->transition_tmo) {
 		sdev_printk(KERN_INFO, sdev,
 			    "%s: transition timeout set to %d seconds\n",
 			    ALUA_DH_NAME, pg->transition_tmo);
@@ -545,19 +543,14 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg, int w
 
 	switch (pg->state) {
 	case TPGS_STATE_TRANSITIONING:
-		if (wait_for_transition) {
-			if (time_before(jiffies, expiry)) {
-				/* State transition, retry */
-				interval += 2000;
-				msleep(interval);
-				goto retry;
-			}
-			err = SCSI_DH_RETRY;
-		} else {
-			err = SCSI_DH_OK;
+		if (time_before(jiffies, expiry)) {
+			/* State transition, retry */
+			interval += 2000;
+			msleep(interval);
+			goto retry;
 		}
-
 		/* Transitioning time exceeded, set port to standby */
+		err = SCSI_DH_RETRY;
 		pg->state = TPGS_STATE_STANDBY;
 		break;
 	case TPGS_STATE_OFFLINE:
@@ -713,14 +706,14 @@ static int alua_activate(struct scsi_device *sdev,
 	if (optimize_stpg)
 		h->pg->flags |= ALUA_OPTIMIZE_STPG;
 
-	err = alua_rtpg(sdev, h->pg, 1);
+	err = alua_rtpg(sdev, h->pg);
 	if (err != SCSI_DH_OK) {
 		kref_put(&h->pg->kref, release_port_group);
 		goto out;
 	}
 	err = alua_stpg(sdev, h->pg);
 	if (err == SCSI_DH_RETRY)
-		err = alua_rtpg(sdev, h->pg, 1);
+		err = alua_rtpg(sdev, h->pg);
 	kref_put(&h->pg->kref, release_port_group);
 out:
 	if (fn)
-- 
1.8.5.6

[PATCHv8 11/23] scsi_dh_alua: move optimize_stpg evaluation

[Hannes Reinecke]

When the optimize_stpg module option is set we should just set it
once during port_group allocation. Doing so allows us to override
it later with device specific settings.

Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.com>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index 0ae2536..d02894d 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -64,6 +64,10 @@
 #define ALUA_OPTIMIZE_STPG		1
 #define ALUA_RTPG_EXT_HDR_UNSUPP	2
 
+static uint optimize_stpg;
+module_param(optimize_stpg, uint, S_IRUGO|S_IWUSR);
+MODULE_PARM_DESC(optimize_stpg, "Allow use of a non-optimized path, rather than sending a STPG, when implicit TPGS is supported (0=No,1=Yes). Default is 0.");
+
 static LIST_HEAD(port_group_list);
 static DEFINE_SPINLOCK(port_group_lock);
 
@@ -219,6 +223,8 @@ struct alua_port_group *alua_alloc_pg(struct scsi_device *sdev,
 	pg->group_id = group_id;
 	pg->tpgs = tpgs;
 	pg->state = TPGS_STATE_OPTIMIZED;
+	if (optimize_stpg)
+		pg->flags |= ALUA_OPTIMIZE_STPG;
 	kref_init(&pg->kref);
 
 	spin_lock(&port_group_lock);
@@ -678,10 +684,6 @@ static int alua_set_params(struct scsi_device *sdev, const char *params)
 	return result;
 }
 
-static uint optimize_stpg;
-module_param(optimize_stpg, uint, S_IRUGO|S_IWUSR);
-MODULE_PARM_DESC(optimize_stpg, "Allow use of a non-optimized path, rather than sending a STPG, when implicit TPGS is supported (0=No,1=Yes). Default is 0.");
-
 /*
  * alua_activate - activate a path
  * @sdev: device on the path to be activated
@@ -703,9 +705,6 @@ static int alua_activate(struct scsi_device *sdev,
 
 	kref_get(&h->pg->kref);
 
-	if (optimize_stpg)
-		h->pg->flags |= ALUA_OPTIMIZE_STPG;
-
 	err = alua_rtpg(sdev, h->pg);
 	if (err != SCSI_DH_OK) {
 		kref_put(&h->pg->kref, release_port_group);
-- 
1.8.5.6

[PATCHv8 12/23] scsi_dh_alua: remove 'rel_port' from alua_dh_data structure

[Hannes Reinecke]

The 'relative port' field is not used, and might get stale when
the port group changes. So remove the field altogether.

Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.com>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index d02894d..7a351cf 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -87,7 +87,6 @@ struct alua_port_group {
 struct alua_dh_data {
 	struct alua_port_group	*pg;
 	int			group_id;
-	int			rel_port;
 	struct scsi_device	*sdev;
 	activate_complete	callback_fn;
 	void			*callback_data;
@@ -325,12 +324,10 @@ static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h,
 			return SCSI_DH_NOMEM;
 		return SCSI_DH_DEV_UNSUPP;
 	}
-	h->rel_port = rel_port;
-
 	sdev_printk(KERN_INFO, sdev,
 		    "%s: device %s port group %x rel port %x\n",
 		    ALUA_DH_NAME, h->pg->device_id_str,
-		    h->group_id, h->rel_port);
+		    h->group_id, rel_port);
 
 	return alua_rtpg(sdev, h->pg);
 }
@@ -762,7 +759,6 @@ static int alua_bus_attach(struct scsi_device *sdev)
 	if (!h)
 		return -ENOMEM;
 	h->pg = NULL;
-	h->rel_port = -1;
 	h->sdev = sdev;
 
 	err = alua_initialize(sdev, h);
-- 
1.8.5.6

[PATCHv8 13/23] scsi_dh_alua: Use workqueue for RTPG

[Hannes Reinecke]

The current ALUA device_handler has two drawbacks:
- We're sending a 'SET TARGET PORT GROUP' command to every LUN,
  disregarding the fact that several LUNs might be in a port group
  and will be automatically switched whenever _any_ LUN within
  that port group receives the command.
- Whenever a LUN is in 'transitioning' mode we cannot block I/O
  to that LUN, instead the controller has to abort the command.
  This leads to increased traffic across the wire and heavy load
  on the controller during switchover.

With this patch the RTPG handling is moved to a per-portgroup
workqueue. This reduces the number of 'REPORT TARGET PORT GROUP'
and 'SET TARGET PORT GROUPS' sent to the controller as we're sending
them now per port group, and not per device as previously.
It also allows us to block I/O to any LUN / port group found to be
in 'transitioning' ALUA mode, as the workqueue item will be requeued
until the controller moves out of transitioning.

Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 296 +++++++++++++++++++++++------
 1 file changed, 242 insertions(+), 54 deletions(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index 7a351cf..8318852 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -59,10 +59,15 @@
 #define ALUA_RTPG_SIZE			128
 #define ALUA_FAILOVER_TIMEOUT		60
 #define ALUA_FAILOVER_RETRIES		5
+#define ALUA_RTPG_DELAY_MSECS		5
 
 /* device handler flags */
-#define ALUA_OPTIMIZE_STPG		1
-#define ALUA_RTPG_EXT_HDR_UNSUPP	2
+#define ALUA_OPTIMIZE_STPG		0x01
+#define ALUA_RTPG_EXT_HDR_UNSUPP	0x02
+/* State machine flags */
+#define ALUA_PG_RUN_RTPG		0x10
+#define ALUA_PG_RUN_STPG		0x20
+#define ALUA_PG_RUNNING			0x40
 
 static uint optimize_stpg;
 module_param(optimize_stpg, uint, S_IRUGO|S_IWUSR);
@@ -70,9 +75,11 @@ MODULE_PARM_DESC(optimize_stpg, "Allow use of a non-optimized path, rather than
 
 static LIST_HEAD(port_group_list);
 static DEFINE_SPINLOCK(port_group_lock);
+static struct workqueue_struct *kaluad_wq;
 
 struct alua_port_group {
 	struct kref		kref;
+	struct rcu_head		rcu;
 	struct list_head	node;
 	unsigned char		device_id_str[256];
 	int			device_id_len;
@@ -82,12 +89,25 @@ struct alua_port_group {
 	int			pref;
 	unsigned		flags; /* used for optimizing STPG */
 	unsigned char		transition_tmo;
+	unsigned long		expiry;
+	unsigned long		interval;
+	struct delayed_work	rtpg_work;
+	spinlock_t		lock;
+	struct list_head	rtpg_list;
+	struct scsi_device	*rtpg_sdev;
 };
 
 struct alua_dh_data {
 	struct alua_port_group	*pg;
 	int			group_id;
+	spinlock_t		pg_lock;
 	struct scsi_device	*sdev;
+	int			init_error;
+	struct mutex		init_mutex;
+};
+
+struct alua_queue_data {
+	struct list_head	entry;
 	activate_complete	callback_fn;
 	void			*callback_data;
 };
@@ -95,18 +115,22 @@ struct alua_dh_data {
 #define ALUA_POLICY_SWITCH_CURRENT	0
 #define ALUA_POLICY_SWITCH_ALL		1
 
-static int alua_rtpg(struct scsi_device *, struct alua_port_group *);
-static char print_alua_state(int);
+static void alua_rtpg_work(struct work_struct *work);
+static void alua_rtpg_queue(struct alua_port_group *pg,
+			    struct scsi_device *sdev,
+			    struct alua_queue_data *qdata);
 
 static void release_port_group(struct kref *kref)
 {
 	struct alua_port_group *pg;
 
 	pg = container_of(kref, struct alua_port_group, kref);
+	if (pg->rtpg_sdev)
+		flush_delayed_work(&pg->rtpg_work);
 	spin_lock(&port_group_lock);
 	list_del(&pg->node);
 	spin_unlock(&port_group_lock);
-	kfree(pg);
+	kfree_rcu(pg, rcu);
 }
 
 /*
@@ -225,6 +249,10 @@ struct alua_port_group *alua_alloc_pg(struct scsi_device *sdev,
 	if (optimize_stpg)
 		pg->flags |= ALUA_OPTIMIZE_STPG;
 	kref_init(&pg->kref);
+	INIT_DELAYED_WORK(&pg->rtpg_work, alua_rtpg_work);
+	INIT_LIST_HEAD(&pg->rtpg_list);
+	INIT_LIST_HEAD(&pg->node);
+	spin_lock_init(&pg->lock);
 
 	spin_lock(&port_group_lock);
 	tmp_pg = alua_find_get_pg(pg->device_id_str, pg->device_id_len,
@@ -304,6 +332,7 @@ static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h,
 			  int tpgs)
 {
 	int rel_port = -1, group_id;
+	struct alua_port_group *pg, *old_pg = NULL;
 
 	group_id = scsi_vpd_tpg_id(sdev, &rel_port);
 	if (group_id < 0) {
@@ -318,18 +347,30 @@ static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h,
 		return SCSI_DH_DEV_UNSUPP;
 	}
 
-	h->pg = alua_alloc_pg(sdev, group_id, tpgs);
-	if (IS_ERR(h->pg)) {
-		if (PTR_ERR(h->pg) == -ENOMEM)
+	pg = alua_alloc_pg(sdev, group_id, tpgs);
+	if (IS_ERR(pg)) {
+		if (PTR_ERR(pg) == -ENOMEM)
 			return SCSI_DH_NOMEM;
 		return SCSI_DH_DEV_UNSUPP;
 	}
 	sdev_printk(KERN_INFO, sdev,
 		    "%s: device %s port group %x rel port %x\n",
-		    ALUA_DH_NAME, h->pg->device_id_str,
-		    h->group_id, rel_port);
+		    ALUA_DH_NAME, pg->device_id_str, group_id, rel_port);
+
+	/* Check for existing port group references */
+	spin_lock(&h->pg_lock);
+	old_pg = h->pg;
+	if (old_pg != pg) {
+		/* port group has changed. Update to new port group */
+		rcu_assign_pointer(h->pg, pg);
+	}
+	alua_rtpg_queue(h->pg, sdev, NULL);
+	spin_unlock(&h->pg_lock);
+
+	if (old_pg)
+		kref_put(&old_pg->kref, release_port_group);
 
-	return alua_rtpg(sdev, h->pg);
+	return SCSI_DH_OK;
 }
 
 static char print_alua_state(int state)
@@ -423,14 +464,17 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
 	int len, k, off, valid_states = 0, bufflen = ALUA_RTPG_SIZE;
 	unsigned char *ucp, *buff;
 	unsigned err, retval;
-	unsigned long expiry, interval = 0;
 	unsigned int tpg_desc_tbl_off;
 	unsigned char orig_transition_tmo;
 
-	if (!pg->transition_tmo)
-		expiry = round_jiffies_up(jiffies + ALUA_FAILOVER_TIMEOUT * HZ);
-	else
-		expiry = round_jiffies_up(jiffies + pg->transition_tmo * HZ);
+	if (!pg->expiry) {
+		unsigned long transition_tmo = ALUA_FAILOVER_TIMEOUT * HZ;
+
+		if (pg->transition_tmo)
+			transition_tmo = pg->transition_tmo * HZ;
+
+		pg->expiry = round_jiffies_up(jiffies + transition_tmo);
+	}
 
 	buff = kzalloc(bufflen, GFP_KERNEL);
 	if (!buff)
@@ -473,16 +517,18 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
 			err = SCSI_DH_RETRY;
 		else if (sense_hdr.sense_key == UNIT_ATTENTION)
 			err = SCSI_DH_RETRY;
-		if (err == SCSI_DH_RETRY && time_before(jiffies, expiry)) {
+		if (err == SCSI_DH_RETRY &&
+		    pg->expiry != 0 && time_before(jiffies, pg->expiry)) {
 			sdev_printk(KERN_ERR, sdev, "%s: rtpg retry\n",
 				    ALUA_DH_NAME);
 			scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
-			goto retry;
+			return err;
 		}
 		sdev_printk(KERN_ERR, sdev, "%s: rtpg failed\n",
 			    ALUA_DH_NAME);
 		scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
 		kfree(buff);
+		pg->expiry = 0;
 		return SCSI_DH_IO;
 	}
 
@@ -497,6 +543,7 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
 			sdev_printk(KERN_WARNING, sdev,
 				    "%s: kmalloc buffer failed\n",__func__);
 			/* Temporary failure, bypass */
+			pg->expiry = 0;
 			return SCSI_DH_DEV_TEMP_BUSY;
 		}
 		goto retry;
@@ -512,7 +559,7 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
 		sdev_printk(KERN_INFO, sdev,
 			    "%s: transition timeout set to %d seconds\n",
 			    ALUA_DH_NAME, pg->transition_tmo);
-		expiry = jiffies + pg->transition_tmo * HZ;
+		pg->expiry = jiffies + pg->transition_tmo * HZ;
 	}
 
 	if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR)
@@ -546,23 +593,26 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
 
 	switch (pg->state) {
 	case TPGS_STATE_TRANSITIONING:
-		if (time_before(jiffies, expiry)) {
+		if (time_before(jiffies, pg->expiry)) {
 			/* State transition, retry */
-			interval += 2000;
-			msleep(interval);
-			goto retry;
+			pg->interval = 2;
+			err = SCSI_DH_RETRY;
+		} else {
+			/* Transitioning time exceeded, set port to standby */
+			err = SCSI_DH_IO;
+			pg->state = TPGS_STATE_STANDBY;
+			pg->expiry = 0;
 		}
-		/* Transitioning time exceeded, set port to standby */
-		err = SCSI_DH_RETRY;
-		pg->state = TPGS_STATE_STANDBY;
 		break;
 	case TPGS_STATE_OFFLINE:
 		/* Path unusable */
 		err = SCSI_DH_DEV_OFFLINED;
+		pg->expiry = 0;
 		break;
 	default:
 		/* Useable path if active */
 		err = SCSI_DH_OK;
+		pg->expiry = 0;
 		break;
 	}
 	kfree(buff);
@@ -627,6 +677,107 @@ static unsigned alua_stpg(struct scsi_device *sdev, struct alua_port_group *pg)
 	return SCSI_DH_RETRY;
 }
 
+static void alua_rtpg_work(struct work_struct *work)
+{
+	struct alua_port_group *pg =
+		container_of(work, struct alua_port_group, rtpg_work.work);
+	struct scsi_device *sdev;
+	LIST_HEAD(qdata_list);
+	int err = SCSI_DH_OK;
+	struct alua_queue_data *qdata, *tmp;
+	unsigned long flags;
+
+	spin_lock_irqsave(&pg->lock, flags);
+	sdev = pg->rtpg_sdev;
+	if (!sdev) {
+		WARN_ON(pg->flags & ALUA_PG_RUN_RTPG);
+		WARN_ON(pg->flags & ALUA_PG_RUN_STPG);
+		spin_unlock_irqrestore(&pg->lock, flags);
+		return;
+	}
+	pg->flags |= ALUA_PG_RUNNING;
+	if (pg->flags & ALUA_PG_RUN_RTPG) {
+		pg->flags &= ~ALUA_PG_RUN_RTPG;
+		spin_unlock_irqrestore(&pg->lock, flags);
+		err = alua_rtpg(sdev, pg);
+		spin_lock_irqsave(&pg->lock, flags);
+		if (err == SCSI_DH_RETRY) {
+			pg->flags &= ~ALUA_PG_RUNNING;
+			pg->flags |= ALUA_PG_RUN_RTPG;
+			spin_unlock_irqrestore(&pg->lock, flags);
+			queue_delayed_work(kaluad_wq, &pg->rtpg_work,
+					   pg->interval * HZ);
+			return;
+		}
+		if (err != SCSI_DH_OK)
+			pg->flags &= ~ALUA_PG_RUN_STPG;
+	}
+	if (pg->flags & ALUA_PG_RUN_STPG) {
+		pg->flags &= ~ALUA_PG_RUN_STPG;
+		spin_unlock_irqrestore(&pg->lock, flags);
+		err = alua_stpg(sdev, pg);
+		spin_lock_irqsave(&pg->lock, flags);
+		if (err == SCSI_DH_RETRY) {
+			pg->flags |= ALUA_PG_RUN_RTPG;
+			pg->interval = 0;
+			pg->flags &= ~ALUA_PG_RUNNING;
+			spin_unlock_irqrestore(&pg->lock, flags);
+			queue_delayed_work(kaluad_wq, &pg->rtpg_work,
+					   pg->interval * HZ);
+			return;
+		}
+	}
+
+	list_splice_init(&pg->rtpg_list, &qdata_list);
+	pg->rtpg_sdev = NULL;
+	spin_unlock_irqrestore(&pg->lock, flags);
+
+	list_for_each_entry_safe(qdata, tmp, &qdata_list, entry) {
+		list_del(&qdata->entry);
+		if (qdata->callback_fn)
+			qdata->callback_fn(qdata->callback_data, err);
+		kfree(qdata);
+	}
+	spin_lock_irqsave(&pg->lock, flags);
+	pg->flags &= ~ALUA_PG_RUNNING;
+	spin_unlock_irqrestore(&pg->lock, flags);
+	scsi_device_put(sdev);
+	kref_put(&pg->kref, release_port_group);
+}
+
+static void alua_rtpg_queue(struct alua_port_group *pg,
+			    struct scsi_device *sdev,
+			    struct alua_queue_data *qdata)
+{
+	int start_queue = 0;
+	unsigned long flags;
+
+	if (!pg)
+		return;
+
+	spin_lock_irqsave(&pg->lock, flags);
+	if (qdata) {
+		list_add_tail(&qdata->entry, &pg->rtpg_list);
+		pg->flags |= ALUA_PG_RUN_STPG;
+	}
+	if (pg->rtpg_sdev == NULL) {
+		pg->interval = 0;
+		pg->flags |= ALUA_PG_RUN_RTPG;
+		kref_get(&pg->kref);
+		pg->rtpg_sdev = sdev;
+		scsi_device_get(sdev);
+		start_queue = 1;
+	}
+	spin_unlock_irqrestore(&pg->lock, flags);
+
+	if (start_queue &&
+	    !queue_delayed_work(kaluad_wq, &pg->rtpg_work,
+				msecs_to_jiffies(ALUA_RTPG_DELAY_MSECS))) {
+		scsi_device_put(sdev);
+		kref_put(&pg->kref, release_port_group);
+	}
+}
+
 /*
  * alua_initialize - Initialize ALUA state
  * @sdev: the device to be initialized
@@ -638,10 +789,12 @@ static int alua_initialize(struct scsi_device *sdev, struct alua_dh_data *h)
 {
 	int err = SCSI_DH_DEV_UNSUPP, tpgs;
 
+	mutex_lock(&h->init_mutex);
 	tpgs = alua_check_tpgs(sdev);
 	if (tpgs != TPGS_MODE_NONE)
 		err = alua_check_vpd(sdev, h, tpgs);
-
+	h->init_error = err;
+	mutex_unlock(&h->init_mutex);
 	return err;
 }
 /*
@@ -656,10 +809,11 @@ static int alua_initialize(struct scsi_device *sdev, struct alua_dh_data *h)
 static int alua_set_params(struct scsi_device *sdev, const char *params)
 {
 	struct alua_dh_data *h = sdev->handler_data;
-	struct alua_port_group *pg = NULL;
+	struct alua_port_group __rcu *pg = NULL;
 	unsigned int optimize = 0, argc;
 	const char *p = params;
 	int result = SCSI_DH_OK;
+	unsigned long flags;
 
 	if ((sscanf(params, "%u", &argc) != 1) || (argc != 1))
 		return -EINVAL;
@@ -669,14 +823,19 @@ static int alua_set_params(struct scsi_device *sdev, const char *params)
 	if ((sscanf(p, "%u", &optimize) != 1) || (optimize > 1))
 		return -EINVAL;
 
-	pg = h->pg;
-	if (!pg)
+	rcu_read_lock();
+	pg = rcu_dereference(h->pg);
+	if (!pg) {
+		rcu_read_unlock();
 		return -ENXIO;
-
+	}
+	spin_lock_irqsave(&pg->lock, flags);
 	if (optimize)
 		pg->flags |= ALUA_OPTIMIZE_STPG;
 	else
 		pg->flags &= ~ALUA_OPTIMIZE_STPG;
+	spin_unlock_irqrestore(&pg->lock, flags);
+	rcu_read_unlock();
 
 	return result;
 }
@@ -696,21 +855,33 @@ static int alua_activate(struct scsi_device *sdev,
 {
 	struct alua_dh_data *h = sdev->handler_data;
 	int err = SCSI_DH_OK;
+	struct alua_queue_data *qdata;
+	struct alua_port_group __rcu *pg;
 
-	if (!h->pg)
+	qdata = kzalloc(sizeof(*qdata), GFP_KERNEL);
+	if (!qdata) {
+		err = SCSI_DH_RES_TEMP_UNAVAIL;
 		goto out;
-
-	kref_get(&h->pg->kref);
-
-	err = alua_rtpg(sdev, h->pg);
-	if (err != SCSI_DH_OK) {
-		kref_put(&h->pg->kref, release_port_group);
+	}
+	qdata->callback_fn = fn;
+	qdata->callback_data = data;
+
+	mutex_lock(&h->init_mutex);
+	rcu_read_lock();
+	pg = rcu_dereference(h->pg);
+	if (!pg || !kref_get_unless_zero(&pg->kref)) {
+		rcu_read_unlock();
+		kfree(qdata);
+		err = h->init_error;
+		mutex_unlock(&h->init_mutex);
 		goto out;
 	}
-	err = alua_stpg(sdev, h->pg);
-	if (err == SCSI_DH_RETRY)
-		err = alua_rtpg(sdev, h->pg);
-	kref_put(&h->pg->kref, release_port_group);
+	fn = NULL;
+	rcu_read_unlock();
+	mutex_unlock(&h->init_mutex);
+
+	alua_rtpg_queue(pg, sdev, qdata);
+	kref_put(&pg->kref, release_port_group);
 out:
 	if (fn)
 		fn(data, err);
@@ -726,14 +897,15 @@ out:
 static int alua_prep_fn(struct scsi_device *sdev, struct request *req)
 {
 	struct alua_dh_data *h = sdev->handler_data;
-	int state;
+	struct alua_port_group __rcu *pg;
+	int state = TPGS_STATE_OPTIMIZED;
 	int ret = BLKPREP_OK;
 
-	if (!h->pg)
-		return ret;
-	kref_get(&h->pg->kref);
-	state = h->pg->state;
-	kref_put(&h->pg->kref, release_port_group);
+	rcu_read_lock();
+	pg = rcu_dereference(h->pg);
+	if (pg)
+		state = pg->state;
+	rcu_read_unlock();
 	if (state == TPGS_STATE_TRANSITIONING)
 		ret = BLKPREP_DEFER;
 	else if (state != TPGS_STATE_OPTIMIZED &&
@@ -758,9 +930,12 @@ static int alua_bus_attach(struct scsi_device *sdev)
 	h = kzalloc(sizeof(*h) , GFP_KERNEL);
 	if (!h)
 		return -ENOMEM;
-	h->pg = NULL;
+	spin_lock_init(&h->pg_lock);
+	rcu_assign_pointer(h->pg, NULL);
+	h->init_error = SCSI_DH_OK;
 	h->sdev = sdev;
 
+	mutex_init(&h->init_mutex);
 	err = alua_initialize(sdev, h);
 	if (err == SCSI_DH_NOMEM)
 		ret = -ENOMEM;
@@ -781,11 +956,16 @@ failed:
 static void alua_bus_detach(struct scsi_device *sdev)
 {
 	struct alua_dh_data *h = sdev->handler_data;
+	struct alua_port_group *pg;
+
+	spin_lock(&h->pg_lock);
+	pg = h->pg;
+	rcu_assign_pointer(h->pg, NULL);
+	h->sdev = NULL;
+	spin_unlock(&h->pg_lock);
+	if (pg)
+		kref_put(&pg->kref, release_port_group);
 
-	if (h->pg) {
-		kref_put(&h->pg->kref, release_port_group);
-		h->pg = NULL;
-	}
 	sdev->handler_data = NULL;
 	kfree(h);
 }
@@ -805,16 +985,24 @@ static int __init alua_init(void)
 {
 	int r;
 
+	kaluad_wq = alloc_workqueue("kaluad", WQ_MEM_RECLAIM, 0);
+	if (!kaluad_wq) {
+		/* Temporary failure, bypass */
+		return SCSI_DH_DEV_TEMP_BUSY;
+	}
 	r = scsi_register_device_handler(&alua_dh);
-	if (r != 0)
+	if (r != 0) {
 		printk(KERN_ERR "%s: Failed to register scsi device handler",
 			ALUA_DH_NAME);
+		destroy_workqueue(kaluad_wq);
+	}
 	return r;
 }
 
 static void __exit alua_exit(void)
 {
 	scsi_unregister_device_handler(&alua_dh);
+	destroy_workqueue(kaluad_wq);
 }
 
 module_init(alua_init);
-- 
1.8.5.6

[PATCHv8 14/23] scsi_dh_alua: Allow workqueue to run synchronously

[Hannes Reinecke]

Some arrays may only capable of handling one STPG at a time,
so this patch adds a singlethreaded workqueue for STPGs to be
submitted synchronously.

Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index 8318852..a3cb069 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -64,6 +64,7 @@
 /* device handler flags */
 #define ALUA_OPTIMIZE_STPG		0x01
 #define ALUA_RTPG_EXT_HDR_UNSUPP	0x02
+#define ALUA_SYNC_STPG			0x04
 /* State machine flags */
 #define ALUA_PG_RUN_RTPG		0x10
 #define ALUA_PG_RUN_STPG		0x20
@@ -76,6 +77,7 @@ MODULE_PARM_DESC(optimize_stpg, "Allow use of a non-optimized path, rather than
 static LIST_HEAD(port_group_list);
 static DEFINE_SPINLOCK(port_group_lock);
 static struct workqueue_struct *kaluad_wq;
+static struct workqueue_struct *kaluad_sync_wq;
 
 struct alua_port_group {
 	struct kref		kref;
@@ -686,6 +688,7 @@ static void alua_rtpg_work(struct work_struct *work)
 	int err = SCSI_DH_OK;
 	struct alua_queue_data *qdata, *tmp;
 	unsigned long flags;
+	struct workqueue_struct *alua_wq = kaluad_wq;
 
 	spin_lock_irqsave(&pg->lock, flags);
 	sdev = pg->rtpg_sdev;
@@ -695,6 +698,8 @@ static void alua_rtpg_work(struct work_struct *work)
 		spin_unlock_irqrestore(&pg->lock, flags);
 		return;
 	}
+	if (pg->flags & ALUA_SYNC_STPG)
+		alua_wq = kaluad_sync_wq;
 	pg->flags |= ALUA_PG_RUNNING;
 	if (pg->flags & ALUA_PG_RUN_RTPG) {
 		pg->flags &= ~ALUA_PG_RUN_RTPG;
@@ -705,7 +710,7 @@ static void alua_rtpg_work(struct work_struct *work)
 			pg->flags &= ~ALUA_PG_RUNNING;
 			pg->flags |= ALUA_PG_RUN_RTPG;
 			spin_unlock_irqrestore(&pg->lock, flags);
-			queue_delayed_work(kaluad_wq, &pg->rtpg_work,
+			queue_delayed_work(alua_wq, &pg->rtpg_work,
 					   pg->interval * HZ);
 			return;
 		}
@@ -722,7 +727,7 @@ static void alua_rtpg_work(struct work_struct *work)
 			pg->interval = 0;
 			pg->flags &= ~ALUA_PG_RUNNING;
 			spin_unlock_irqrestore(&pg->lock, flags);
-			queue_delayed_work(kaluad_wq, &pg->rtpg_work,
+			queue_delayed_work(alua_wq, &pg->rtpg_work,
 					   pg->interval * HZ);
 			return;
 		}
@@ -751,6 +756,7 @@ static void alua_rtpg_queue(struct alua_port_group *pg,
 {
 	int start_queue = 0;
 	unsigned long flags;
+	struct workqueue_struct *alua_wq = kaluad_wq;
 
 	if (!pg)
 		return;
@@ -768,10 +774,12 @@ static void alua_rtpg_queue(struct alua_port_group *pg,
 		scsi_device_get(sdev);
 		start_queue = 1;
 	}
+	if (pg->flags & ALUA_SYNC_STPG)
+		alua_wq = kaluad_sync_wq;
 	spin_unlock_irqrestore(&pg->lock, flags);
 
 	if (start_queue &&
-	    !queue_delayed_work(kaluad_wq, &pg->rtpg_work,
+	    !queue_delayed_work(alua_wq, &pg->rtpg_work,
 				msecs_to_jiffies(ALUA_RTPG_DELAY_MSECS))) {
 		scsi_device_put(sdev);
 		kref_put(&pg->kref, release_port_group);
@@ -990,10 +998,16 @@ static int __init alua_init(void)
 		/* Temporary failure, bypass */
 		return SCSI_DH_DEV_TEMP_BUSY;
 	}
+	kaluad_sync_wq = create_workqueue("kaluad_sync");
+	if (!kaluad_sync_wq) {
+		destroy_workqueue(kaluad_wq);
+		return SCSI_DH_DEV_TEMP_BUSY;
+	}
 	r = scsi_register_device_handler(&alua_dh);
 	if (r != 0) {
 		printk(KERN_ERR "%s: Failed to register scsi device handler",
 			ALUA_DH_NAME);
+		destroy_workqueue(kaluad_sync_wq);
 		destroy_workqueue(kaluad_wq);
 	}
 	return r;
@@ -1002,6 +1016,7 @@ static int __init alua_init(void)
 static void __exit alua_exit(void)
 {
 	scsi_unregister_device_handler(&alua_dh);
+	destroy_workqueue(kaluad_sync_wq);
 	destroy_workqueue(kaluad_wq);
 }
 
-- 
1.8.5.6

[PATCHv8 15/23] scsi_dh_alua: Add new blacklist flag 'BLIST_SYNC_ALUA'

[Hannes Reinecke]

Add a new blacklist flag BLIST_SYNC_ALUA to instruct the
alua device handler to use synchronous command submission
for ALUA commands.

Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.com>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 2 ++
 drivers/scsi/scsi_devinfo.c                | 2 ++
 drivers/scsi/scsi_scan.c                   | 3 +++
 include/scsi/scsi_device.h                 | 1 +
 include/scsi/scsi_devinfo.h                | 1 +
 5 files changed, 9 insertions(+)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index a3cb069..fbbe85e 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -366,6 +366,8 @@ static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h,
 		/* port group has changed. Update to new port group */
 		rcu_assign_pointer(h->pg, pg);
 	}
+	if (sdev->synchronous_alua)
+		pg->flags |= ALUA_SYNC_STPG;
 	alua_rtpg_queue(h->pg, sdev, NULL);
 	spin_unlock(&h->pg_lock);
 
diff --git a/drivers/scsi/scsi_devinfo.c b/drivers/scsi/scsi_devinfo.c
index 47b9d13..b4ef0c6 100644
--- a/drivers/scsi/scsi_devinfo.c
+++ b/drivers/scsi/scsi_devinfo.c
@@ -218,6 +218,8 @@ static struct {
 	{"NAKAMICH", "MJ-5.16S", NULL, BLIST_FORCELUN | BLIST_SINGLELUN},
 	{"NEC", "PD-1 ODX654P", NULL, BLIST_FORCELUN | BLIST_SINGLELUN},
 	{"NEC", "iStorage", NULL, BLIST_REPORTLUN2},
+	{"NETAPP", "LUN C-Mode", NULL, BLIST_SYNC_ALUA},
+	{"NETAPP", "INF-01-00", NULL, BLIST_SYNC_ALUA},
 	{"NRC", "MBR-7", NULL, BLIST_FORCELUN | BLIST_SINGLELUN},
 	{"NRC", "MBR-7.4", NULL, BLIST_FORCELUN | BLIST_SINGLELUN},
 	{"PIONEER", "CD-ROM DRM-600", NULL, BLIST_FORCELUN | BLIST_SINGLELUN},
diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 1f02e84..420239c 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -964,6 +964,9 @@ static int scsi_add_lun(struct scsi_device *sdev, unsigned char *inq_result,
 	if (*bflags & BLIST_NO_DIF)
 		sdev->no_dif = 1;
 
+	if (*bflags & BLIST_SYNC_ALUA)
+		sdev->synchronous_alua = 1;
+
 	sdev->eh_timeout = SCSI_DEFAULT_EH_TIMEOUT;
 
 	if (*bflags & BLIST_TRY_VPD_PAGES)
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index 9173ab5a..4af2b24 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -176,6 +176,7 @@ struct scsi_device {
 	unsigned no_dif:1;	/* T10 PI (DIF) should be disabled */
 	unsigned broken_fua:1;		/* Don't set FUA bit */
 	unsigned lun_in_cdb:1;		/* Store LUN bits in CDB[1] */
+	unsigned synchronous_alua:1;	/* Synchronous ALUA commands */
 
 	atomic_t disk_events_disable_depth; /* disable depth for disk events */
 
diff --git a/include/scsi/scsi_devinfo.h b/include/scsi/scsi_devinfo.h
index 96e3f56..9f750cb 100644
--- a/include/scsi/scsi_devinfo.h
+++ b/include/scsi/scsi_devinfo.h
@@ -37,5 +37,6 @@
 #define BLIST_TRY_VPD_PAGES	0x10000000 /* Attempt to read VPD pages */
 #define BLIST_NO_RSOC		0x20000000 /* don't try to issue RSOC */
 #define BLIST_MAX_1024		0x40000000 /* maximum 1024 sector cdb length */
+#define BLIST_SYNC_ALUA		0x80000000 /* Synchronous ALUA commands */
 
 #endif
-- 
1.8.5.6

[PATCHv8 16/23] scsi_dh_alua: Recheck state on unit attention

[Hannes Reinecke]

When we receive a unit attention code of 'ALUA state changed'
we should recheck the state, as it might be due to an implicit
ALUA state transition. This allows us to return NEEDS_RETRY
instead of ADD_TO_MLQUEUE, allowing to terminate the retries
after a certain time.
At the same time a workqueue item might already be queued, which
should be started immediately to avoid any delays.

Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.com>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 67 ++++++++++++++++++++++++------
 1 file changed, 55 insertions(+), 12 deletions(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index fbbe85e..ef5d6c3 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -120,7 +120,8 @@ struct alua_queue_data {
 static void alua_rtpg_work(struct work_struct *work);
 static void alua_rtpg_queue(struct alua_port_group *pg,
 			    struct scsi_device *sdev,
-			    struct alua_queue_data *qdata);
+			    struct alua_queue_data *qdata, bool force);
+static void alua_check(struct scsi_device *sdev, bool force);
 
 static void release_port_group(struct kref *kref)
 {
@@ -368,7 +369,7 @@ static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h,
 	}
 	if (sdev->synchronous_alua)
 		pg->flags |= ALUA_SYNC_STPG;
-	alua_rtpg_queue(h->pg, sdev, NULL);
+	alua_rtpg_queue(h->pg, sdev, NULL, true);
 	spin_unlock(&h->pg_lock);
 
 	if (old_pg)
@@ -404,18 +405,24 @@ static int alua_check_sense(struct scsi_device *sdev,
 {
 	switch (sense_hdr->sense_key) {
 	case NOT_READY:
-		if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x0a)
+		if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x0a) {
 			/*
 			 * LUN Not Accessible - ALUA state transition
 			 */
-			return ADD_TO_MLQUEUE;
+			alua_check(sdev, false);
+			return NEEDS_RETRY;
+		}
 		break;
 	case UNIT_ATTENTION:
-		if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x00)
+		if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x00) {
 			/*
-			 * Power On, Reset, or Bus Device Reset, just retry.
+			 * Power On, Reset, or Bus Device Reset.
+			 * Might have obscured a state transition,
+			 * so schedule a recheck.
 			 */
+			alua_check(sdev, true);
 			return ADD_TO_MLQUEUE;
+		}
 		if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x04)
 			/*
 			 * Device internal reset
@@ -426,16 +433,20 @@ static int alua_check_sense(struct scsi_device *sdev,
 			 * Mode Parameters Changed
 			 */
 			return ADD_TO_MLQUEUE;
-		if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x06)
+		if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x06) {
 			/*
 			 * ALUA state changed
 			 */
+			alua_check(sdev, true);
 			return ADD_TO_MLQUEUE;
-		if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x07)
+		}
+		if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x07) {
 			/*
 			 * Implicit ALUA state transition failed
 			 */
+			alua_check(sdev, true);
 			return ADD_TO_MLQUEUE;
+		}
 		if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x03)
 			/*
 			 * Inquiry data has changed
@@ -708,7 +719,7 @@ static void alua_rtpg_work(struct work_struct *work)
 		spin_unlock_irqrestore(&pg->lock, flags);
 		err = alua_rtpg(sdev, pg);
 		spin_lock_irqsave(&pg->lock, flags);
-		if (err == SCSI_DH_RETRY) {
+		if (err == SCSI_DH_RETRY || pg->flags & ALUA_PG_RUN_RTPG) {
 			pg->flags &= ~ALUA_PG_RUNNING;
 			pg->flags |= ALUA_PG_RUN_RTPG;
 			spin_unlock_irqrestore(&pg->lock, flags);
@@ -724,7 +735,7 @@ static void alua_rtpg_work(struct work_struct *work)
 		spin_unlock_irqrestore(&pg->lock, flags);
 		err = alua_stpg(sdev, pg);
 		spin_lock_irqsave(&pg->lock, flags);
-		if (err == SCSI_DH_RETRY) {
+		if (err == SCSI_DH_RETRY || pg->flags & ALUA_PG_RUN_RTPG) {
 			pg->flags |= ALUA_PG_RUN_RTPG;
 			pg->interval = 0;
 			pg->flags &= ~ALUA_PG_RUNNING;
@@ -754,7 +765,7 @@ static void alua_rtpg_work(struct work_struct *work)
 
 static void alua_rtpg_queue(struct alua_port_group *pg,
 			    struct scsi_device *sdev,
-			    struct alua_queue_data *qdata)
+			    struct alua_queue_data *qdata, bool force)
 {
 	int start_queue = 0;
 	unsigned long flags;
@@ -767,6 +778,7 @@ static void alua_rtpg_queue(struct alua_port_group *pg,
 	if (qdata) {
 		list_add_tail(&qdata->entry, &pg->rtpg_list);
 		pg->flags |= ALUA_PG_RUN_STPG;
+		force = true;
 	}
 	if (pg->rtpg_sdev == NULL) {
 		pg->interval = 0;
@@ -775,7 +787,15 @@ static void alua_rtpg_queue(struct alua_port_group *pg,
 		pg->rtpg_sdev = sdev;
 		scsi_device_get(sdev);
 		start_queue = 1;
+	} else if (!(pg->flags & ALUA_PG_RUN_RTPG) && force) {
+		pg->flags |= ALUA_PG_RUN_RTPG;
+		/* Do not queue if the worker is already running */
+		if (!(pg->flags & ALUA_PG_RUNNING)) {
+			kref_get(&pg->kref);
+			start_queue = 1;
+		}
 	}
+
 	if (pg->flags & ALUA_SYNC_STPG)
 		alua_wq = kaluad_sync_wq;
 	spin_unlock_irqrestore(&pg->lock, flags);
@@ -890,7 +910,7 @@ static int alua_activate(struct scsi_device *sdev,
 	rcu_read_unlock();
 	mutex_unlock(&h->init_mutex);
 
-	alua_rtpg_queue(pg, sdev, qdata);
+	alua_rtpg_queue(pg, sdev, qdata, true);
 	kref_put(&pg->kref, release_port_group);
 out:
 	if (fn)
@@ -899,6 +919,29 @@ out:
 }
 
 /*
+ * alua_check - check path status
+ * @sdev: device on the path to be checked
+ *
+ * Check the device status
+ */
+static void alua_check(struct scsi_device *sdev, bool force)
+{
+	struct alua_dh_data *h = sdev->handler_data;
+	struct alua_port_group *pg;
+
+	rcu_read_lock();
+	pg = rcu_dereference(h->pg);
+	if (!pg || !kref_get_unless_zero(&pg->kref)) {
+		rcu_read_unlock();
+		return;
+	}
+	rcu_read_unlock();
+
+	alua_rtpg_queue(pg, sdev, NULL, force);
+	kref_put(&pg->kref, release_port_group);
+}
+
+/*
  * alua_prep_fn - request callback
  *
  * Fail I/O to all paths not in state
-- 
1.8.5.6

[PATCHv8 17/23] scsi_dh_alua: update all port states

[Hannes Reinecke]

When we read in the target port group state we should be
updating all affected port groups, otherwise we risk
running out of sync.

Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 35 ++++++++++++++++++++++--------
 1 file changed, 26 insertions(+), 9 deletions(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index ef5d6c3..98d87d9 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -476,11 +476,13 @@ static int alua_check_sense(struct scsi_device *sdev,
 static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
 {
 	struct scsi_sense_hdr sense_hdr;
+	struct alua_port_group *tmp_pg;
 	int len, k, off, valid_states = 0, bufflen = ALUA_RTPG_SIZE;
-	unsigned char *ucp, *buff;
+	unsigned char *desc, *buff;
 	unsigned err, retval;
 	unsigned int tpg_desc_tbl_off;
 	unsigned char orig_transition_tmo;
+	unsigned long flags;
 
 	if (!pg->expiry) {
 		unsigned long transition_tmo = ALUA_FAILOVER_TIMEOUT * HZ;
@@ -582,18 +584,32 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
 	else
 		tpg_desc_tbl_off = 4;
 
-	for (k = tpg_desc_tbl_off, ucp = buff + tpg_desc_tbl_off;
+	for (k = tpg_desc_tbl_off, desc = buff + tpg_desc_tbl_off;
 	     k < len;
-	     k += off, ucp += off) {
-
-		if (pg->group_id == get_unaligned_be16(&ucp[2])) {
-			pg->state = ucp[0] & 0x0f;
-			pg->pref = ucp[0] >> 7;
-			valid_states = ucp[1];
+	     k += off, desc += off) {
+		u16 group_id = get_unaligned_be16(&desc[2]);
+
+		spin_lock_irqsave(&port_group_lock, flags);
+		tmp_pg = alua_find_get_pg(pg->device_id_str, pg->device_id_len,
+					  group_id);
+		spin_unlock_irqrestore(&port_group_lock, flags);
+		if (tmp_pg) {
+			if (spin_trylock_irqsave(&tmp_pg->lock, flags)) {
+				if ((tmp_pg == pg) ||
+				    !(tmp_pg->flags & ALUA_PG_RUNNING)) {
+					tmp_pg->state = desc[0] & 0x0f;
+					tmp_pg->pref = desc[0] >> 7;
+				}
+				if (tmp_pg == pg)
+					valid_states = desc[1];
+				spin_unlock_irqrestore(&tmp_pg->lock, flags);
+			}
+			kref_put(&tmp_pg->kref, release_port_group);
 		}
-		off = 8 + (ucp[7] * 4);
+		off = 8 + (desc[7] * 4);
 	}
 
+	spin_lock_irqsave(&pg->lock, flags);
 	sdev_printk(KERN_INFO, sdev,
 		    "%s: port group %02x state %c %s supports %c%c%c%c%c%c%c\n",
 		    ALUA_DH_NAME, pg->group_id, print_alua_state(pg->state),
@@ -630,6 +646,7 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
 		pg->expiry = 0;
 		break;
 	}
+	spin_unlock_irqrestore(&pg->lock, flags);
 	kfree(buff);
 	return err;
 }
-- 
1.8.5.6

[PATCHv8 18/23] scsi_dh_alua: Send TEST UNIT READY to poll for transitioning

[Hannes Reinecke]

Sending a 'REPORT TARGET PORT GROUP' command is a costly operation,
as the array has to gather information about all ports.
So instead of using RTPG to poll for a status update when a port
is in transitioning we should be sending a TEST UNIT READY, and
wait for the sense code to report success.

Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Ewan Milne <emilne@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 38 ++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index 98d87d9..3d8a254 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -466,6 +466,30 @@ static int alua_check_sense(struct scsi_device *sdev,
 }
 
 /*
+ * alua_tur - Send a TEST UNIT READY
+ * @sdev: device to which the TEST UNIT READY command should be send
+ *
+ * Send a TEST UNIT READY to @sdev to figure out the device state
+ * Returns SCSI_DH_RETRY if the sense code is NOT READY/ALUA TRANSITIONING,
+ * SCSI_DH_OK if no error occurred, and SCSI_DH_IO otherwise.
+ */
+static int alua_tur(struct scsi_device *sdev)
+{
+	struct scsi_sense_hdr sense_hdr;
+	int retval;
+
+	retval = scsi_test_unit_ready(sdev, ALUA_FAILOVER_TIMEOUT * HZ,
+				      ALUA_FAILOVER_RETRIES, &sense_hdr);
+	if (sense_hdr.sense_key == NOT_READY &&
+	    sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a)
+		return SCSI_DH_RETRY;
+	else if (retval)
+		return SCSI_DH_IO;
+	else
+		return SCSI_DH_OK;
+}
+
+/*
  * alua_rtpg - Evaluate REPORT TARGET GROUP STATES
  * @sdev: the device to be evaluated.
  *
@@ -732,8 +756,22 @@ static void alua_rtpg_work(struct work_struct *work)
 		alua_wq = kaluad_sync_wq;
 	pg->flags |= ALUA_PG_RUNNING;
 	if (pg->flags & ALUA_PG_RUN_RTPG) {
+		int state = pg->state;
+
 		pg->flags &= ~ALUA_PG_RUN_RTPG;
 		spin_unlock_irqrestore(&pg->lock, flags);
+		if (state == TPGS_STATE_TRANSITIONING) {
+			if (alua_tur(sdev) == SCSI_DH_RETRY) {
+				spin_lock_irqsave(&pg->lock, flags);
+				pg->flags &= ~ALUA_PG_RUNNING;
+				pg->flags |= ALUA_PG_RUN_RTPG;
+				spin_unlock_irqrestore(&pg->lock, flags);
+				queue_delayed_work(alua_wq, &pg->rtpg_work,
+						   pg->interval * HZ);
+				return;
+			}
+			/* Send RTPG on failure or if TUR indicates SUCCESS */
+		}
 		err = alua_rtpg(sdev, pg);
 		spin_lock_irqsave(&pg->lock, flags);
 		if (err == SCSI_DH_RETRY || pg->flags & ALUA_PG_RUN_RTPG) {
-- 
1.8.5.6

[PATCHv8 19/23] scsi_dh: add 'rescan' callback

[Hannes Reinecke]

If a device needs to be rescanned the device_handler might need
to be rechecked, too.
So add a 'rescan' callback to the device handler and call it
upon scsi_rescan_device(). The rescan callback will be invoked
from the Unit Attention handling of ASC/ASCQ 3F 03
(INQUIRY DATA HAS CHANGED).

Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 8 ++++++++
 drivers/scsi/scsi_lib.c                    | 1 +
 drivers/scsi/scsi_scan.c                   | 8 +++++++-
 include/scsi/scsi_dh.h                     | 1 +
 4 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index 3d8a254..3d994aa 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -1026,6 +1026,13 @@ static int alua_prep_fn(struct scsi_device *sdev, struct request *req)
 
 }
 
+static void alua_rescan(struct scsi_device *sdev)
+{
+	struct alua_dh_data *h = sdev->handler_data;
+
+	alua_initialize(sdev, h);
+}
+
 /*
  * alua_bus_attach - Attach device handler
  * @sdev: device to be attached to
@@ -1086,6 +1093,7 @@ static struct scsi_device_handler alua_dh = {
 	.prep_fn = alua_prep_fn,
 	.check_sense = alua_check_sense,
 	.activate = alua_activate,
+	.rescan = alua_rescan,
 	.set_params = alua_set_params,
 };
 
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index fa6b2c4..d46193a 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2699,6 +2699,7 @@ static void scsi_evt_emit(struct scsi_device *sdev, struct scsi_event *evt)
 		envp[idx++] = "SDEV_MEDIA_CHANGE=1";
 		break;
 	case SDEV_EVT_INQUIRY_CHANGE_REPORTED:
+		scsi_rescan_device(&sdev->sdev_gendev);
 		envp[idx++] = "SDEV_UA=INQUIRY_DATA_HAS_CHANGED";
 		break;
 	case SDEV_EVT_CAPACITY_CHANGE_REPORTED:
diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 420239c..97074c9 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -43,6 +43,7 @@
 #include <scsi/scsi_devinfo.h>
 #include <scsi/scsi_host.h>
 #include <scsi/scsi_transport.h>
+#include <scsi/scsi_dh.h>
 #include <scsi/scsi_eh.h>
 
 #include "scsi_priv.h"
@@ -1524,9 +1525,14 @@ EXPORT_SYMBOL(scsi_add_device);
 
 void scsi_rescan_device(struct device *dev)
 {
+	struct scsi_device *sdev = to_scsi_device(dev);
+
 	device_lock(dev);
 
-	scsi_attach_vpd(to_scsi_device(dev));
+	scsi_attach_vpd(sdev);
+
+	if (sdev->handler && sdev->handler->rescan)
+		sdev->handler->rescan(sdev);
 
 	if (dev->driver && try_module_get(dev->driver->owner)) {
 		struct scsi_driver *drv = to_scsi_driver(dev->driver);
diff --git a/include/scsi/scsi_dh.h b/include/scsi/scsi_dh.h
index 7e184c6..c7bba2b 100644
--- a/include/scsi/scsi_dh.h
+++ b/include/scsi/scsi_dh.h
@@ -71,6 +71,7 @@ struct scsi_device_handler {
 	int (*activate)(struct scsi_device *, activate_complete, void *);
 	int (*prep_fn)(struct scsi_device *, struct request *);
 	int (*set_params)(struct scsi_device *, const char *);
+	void (*rescan)(struct scsi_device *);
 };
 
 #ifdef CONFIG_SCSI_DH
-- 
1.8.5.6

[PATCHv8 20/23] scsi: Add 'access_state' attribute

[Hannes Reinecke]

Add an 'access_state' attribute to struct scsi_device to
display the asymmetric LUN access state.

Reviewed-by: Ewan Milne <emilne@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/scsi_sysfs.c  | 53 ++++++++++++++++++++++++++++++++++++++++++++++
 include/scsi/scsi_device.h |  1 +
 include/scsi/scsi_proto.h  | 12 +++++++++++
 3 files changed, 66 insertions(+)

diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 4f18a85..33ef68d 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -81,6 +81,33 @@ const char *scsi_host_state_name(enum scsi_host_state state)
 	return name;
 }
 
+static const struct {
+	unsigned char	value;
+	char		*name;
+} sdev_access_states[] = {
+	{ SCSI_ACCESS_STATE_OPTIMAL, "active/optimized" },
+	{ SCSI_ACCESS_STATE_ACTIVE, "active/non-optimized" },
+	{ SCSI_ACCESS_STATE_STANDBY, "standby" },
+	{ SCSI_ACCESS_STATE_UNAVAILABLE, "unavailable" },
+	{ SCSI_ACCESS_STATE_LBA, "lba-dependent" },
+	{ SCSI_ACCESS_STATE_OFFLINE, "offline" },
+	{ SCSI_ACCESS_STATE_TRANSITIONING, "transitioning" },
+};
+
+const char *scsi_access_state_name(unsigned char state)
+{
+	int i;
+	char *name = NULL;
+
+	for (i = 0; i < ARRAY_SIZE(sdev_access_states); i++) {
+		if (sdev_access_states[i].value == state) {
+			name = sdev_access_states[i].name;
+			break;
+		}
+	}
+	return name;
+}
+
 static int check_set(unsigned long long *val, char *src)
 {
 	char *last;
@@ -973,6 +1000,31 @@ sdev_store_dh_state(struct device *dev, struct device_attribute *attr,
 
 static DEVICE_ATTR(dh_state, S_IRUGO | S_IWUSR, sdev_show_dh_state,
 		   sdev_store_dh_state);
+
+static ssize_t
+sdev_show_access_state(struct device *dev,
+		       struct device_attribute *attr,
+		       char *buf)
+{
+	struct scsi_device *sdev = to_scsi_device(dev);
+	unsigned char access_state;
+	const char *access_state_name;
+	bool pref = false;
+
+	if (!sdev->handler)
+		return -EINVAL;
+
+	if (sdev->access_state & SCSI_ACCESS_STATE_PREFERRED)
+		pref = true;
+
+	access_state = (sdev->access_state & SCSI_ACCESS_STATE_MASK);
+	access_state_name = scsi_access_state_name(access_state);
+
+	return snprintf(buf, 32, "%s%s\n",
+			access_state_name ? access_state_name : "unknown",
+			pref ? " preferred" : "");
+}
+static DEVICE_ATTR(access_state, S_IRUGO, sdev_show_access_state, NULL);
 #endif
 
 static ssize_t
@@ -1047,6 +1099,7 @@ static struct attribute *scsi_sdev_attrs[] = {
 	&dev_attr_wwid.attr,
 #ifdef CONFIG_SCSI_DH
 	&dev_attr_dh_state.attr,
+	&dev_attr_access_state.attr,
 #endif
 	&dev_attr_queue_ramp_up_period.attr,
 	REF_EVT(media_change),
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index 4af2b24..c067019 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -201,6 +201,7 @@ struct scsi_device {
 	struct scsi_device_handler *handler;
 	void			*handler_data;
 
+	unsigned char		access_state;
 	enum scsi_device_state sdev_state;
 	unsigned long		sdev_data[0];
 } __attribute__((aligned(sizeof(unsigned long))));
diff --git a/include/scsi/scsi_proto.h b/include/scsi/scsi_proto.h
index a9fbf1b..c2ae21c 100644
--- a/include/scsi/scsi_proto.h
+++ b/include/scsi/scsi_proto.h
@@ -277,5 +277,17 @@ struct scsi_lun {
 	__u8 scsi_lun[8];
 };
 
+/* SPC asymmetric access states */
+#define SCSI_ACCESS_STATE_OPTIMAL     0x00
+#define SCSI_ACCESS_STATE_ACTIVE      0x01
+#define SCSI_ACCESS_STATE_STANDBY     0x02
+#define SCSI_ACCESS_STATE_UNAVAILABLE 0x03
+#define SCSI_ACCESS_STATE_LBA         0x04
+#define SCSI_ACCESS_STATE_OFFLINE     0x0e
+#define SCSI_ACCESS_STATE_TRANSITIONING 0x0f
+
+/* Values for REPORT TARGET GROUP STATES */
+#define SCSI_ACCESS_STATE_MASK        0x0f
+#define SCSI_ACCESS_STATE_PREFERRED   0x80
 
 #endif /* _SCSI_PROTO_H_ */
-- 
1.8.5.6

[PATCHv8 21/23] scsi_dh_alua: use common definitions for ALUA state

[Hannes Reinecke]

scsi_proto.h now contains definitions for the ALUA state,
so we don't have to carry them in the device handler.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 58 +++++++++++++-----------------
 1 file changed, 25 insertions(+), 33 deletions(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index 3d994aa..daa4d59 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -31,14 +31,6 @@
 #define ALUA_DH_NAME "alua"
 #define ALUA_DH_VER "1.3"
 
-#define TPGS_STATE_OPTIMIZED		0x0
-#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
-
 #define TPGS_SUPPORT_NONE		0x00
 #define TPGS_SUPPORT_OPTIMIZED		0x01
 #define TPGS_SUPPORT_NONOPTIMIZED	0x02
@@ -180,7 +172,7 @@ static int submit_stpg(struct scsi_device *sdev, int group_id,
 
 	/* Prepare the data buffer */
 	memset(stpg_data, 0, stpg_len);
-	stpg_data[4] = TPGS_STATE_OPTIMIZED & 0x0f;
+	stpg_data[4] = SCSI_ACCESS_STATE_OPTIMAL;
 	put_unaligned_be16(group_id, &stpg_data[6]);
 
 	/* Prepare the command. */
@@ -248,7 +240,7 @@ struct alua_port_group *alua_alloc_pg(struct scsi_device *sdev,
 	}
 	pg->group_id = group_id;
 	pg->tpgs = tpgs;
-	pg->state = TPGS_STATE_OPTIMIZED;
+	pg->state = SCSI_ACCESS_STATE_OPTIMAL;
 	if (optimize_stpg)
 		pg->flags |= ALUA_OPTIMIZE_STPG;
 	kref_init(&pg->kref);
@@ -378,22 +370,22 @@ static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h,
 	return SCSI_DH_OK;
 }
 
-static char print_alua_state(int state)
+static char print_alua_state(unsigned char state)
 {
 	switch (state) {
-	case TPGS_STATE_OPTIMIZED:
+	case SCSI_ACCESS_STATE_OPTIMAL:
 		return 'A';
-	case TPGS_STATE_NONOPTIMIZED:
+	case SCSI_ACCESS_STATE_ACTIVE:
 		return 'N';
-	case TPGS_STATE_STANDBY:
+	case SCSI_ACCESS_STATE_STANDBY:
 		return 'S';
-	case TPGS_STATE_UNAVAILABLE:
+	case SCSI_ACCESS_STATE_UNAVAILABLE:
 		return 'U';
-	case TPGS_STATE_LBA_DEPENDENT:
+	case SCSI_ACCESS_STATE_LBA:
 		return 'L';
-	case TPGS_STATE_OFFLINE:
+	case SCSI_ACCESS_STATE_OFFLINE:
 		return 'O';
-	case TPGS_STATE_TRANSITIONING:
+	case SCSI_ACCESS_STATE_TRANSITIONING:
 		return 'T';
 	default:
 		return 'X';
@@ -647,7 +639,7 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
 		    valid_states&TPGS_SUPPORT_OPTIMIZED?'A':'a');
 
 	switch (pg->state) {
-	case TPGS_STATE_TRANSITIONING:
+	case SCSI_ACCESS_STATE_TRANSITIONING:
 		if (time_before(jiffies, pg->expiry)) {
 			/* State transition, retry */
 			pg->interval = 2;
@@ -655,11 +647,11 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
 		} else {
 			/* Transitioning time exceeded, set port to standby */
 			err = SCSI_DH_IO;
-			pg->state = TPGS_STATE_STANDBY;
+			pg->state = SCSI_ACCESS_STATE_STANDBY;
 			pg->expiry = 0;
 		}
 		break;
-	case TPGS_STATE_OFFLINE:
+	case SCSI_ACCESS_STATE_OFFLINE:
 		/* Path unusable */
 		err = SCSI_DH_DEV_OFFLINED;
 		pg->expiry = 0;
@@ -693,20 +685,20 @@ static unsigned alua_stpg(struct scsi_device *sdev, struct alua_port_group *pg)
 		return SCSI_DH_RETRY;
 	}
 	switch (pg->state) {
-	case TPGS_STATE_OPTIMIZED:
+	case SCSI_ACCESS_STATE_OPTIMAL:
 		return SCSI_DH_OK;
-	case TPGS_STATE_NONOPTIMIZED:
+	case SCSI_ACCESS_STATE_ACTIVE:
 		if ((pg->flags & ALUA_OPTIMIZE_STPG) &&
 		    !pg->pref &&
 		    (pg->tpgs & TPGS_MODE_IMPLICIT))
 			return SCSI_DH_OK;
 		break;
-	case TPGS_STATE_STANDBY:
-	case TPGS_STATE_UNAVAILABLE:
+	case SCSI_ACCESS_STATE_STANDBY:
+	case SCSI_ACCESS_STATE_UNAVAILABLE:
 		break;
-	case TPGS_STATE_OFFLINE:
+	case SCSI_ACCESS_STATE_OFFLINE:
 		return SCSI_DH_IO;
-	case TPGS_STATE_TRANSITIONING:
+	case SCSI_ACCESS_STATE_TRANSITIONING:
 		break;
 	default:
 		sdev_printk(KERN_INFO, sdev,
@@ -760,7 +752,7 @@ static void alua_rtpg_work(struct work_struct *work)
 
 		pg->flags &= ~ALUA_PG_RUN_RTPG;
 		spin_unlock_irqrestore(&pg->lock, flags);
-		if (state == TPGS_STATE_TRANSITIONING) {
+		if (state == SCSI_ACCESS_STATE_TRANSITIONING) {
 			if (alua_tur(sdev) == SCSI_DH_RETRY) {
 				spin_lock_irqsave(&pg->lock, flags);
 				pg->flags &= ~ALUA_PG_RUNNING;
@@ -1006,7 +998,7 @@ static int alua_prep_fn(struct scsi_device *sdev, struct request *req)
 {
 	struct alua_dh_data *h = sdev->handler_data;
 	struct alua_port_group __rcu *pg;
-	int state = TPGS_STATE_OPTIMIZED;
+	unsigned char state = SCSI_ACCESS_STATE_OPTIMAL;
 	int ret = BLKPREP_OK;
 
 	rcu_read_lock();
@@ -1014,11 +1006,11 @@ static int alua_prep_fn(struct scsi_device *sdev, struct request *req)
 	if (pg)
 		state = pg->state;
 	rcu_read_unlock();
-	if (state == TPGS_STATE_TRANSITIONING)
+	if (state == SCSI_ACCESS_STATE_TRANSITIONING)
 		ret = BLKPREP_DEFER;
-	else if (state != TPGS_STATE_OPTIMIZED &&
-		 state != TPGS_STATE_NONOPTIMIZED &&
-		 state != TPGS_STATE_LBA_DEPENDENT) {
+	else if (state != SCSI_ACCESS_STATE_OPTIMAL &&
+		 state != SCSI_ACCESS_STATE_ACTIVE &&
+		 state != SCSI_ACCESS_STATE_LBA) {
 		ret = BLKPREP_KILL;
 		req->cmd_flags |= REQ_QUIET;
 	}
-- 
1.8.5.6

[PATCHv8 22/23] scsi_dh_alua: update 'access_state' field

[Hannes Reinecke]

Track attached SCSI devices and update the 'access_state' field
whenever an ALUA state change has been detected.

Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Ewan Milne <emilne@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 48 ++++++++++++++++++++++++++++--
 1 file changed, 46 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index daa4d59..fc77765 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>
@@ -75,6 +76,7 @@ struct alua_port_group {
 	struct kref		kref;
 	struct rcu_head		rcu;
 	struct list_head	node;
+	struct list_head	dh_list;
 	unsigned char		device_id_str[256];
 	int			device_id_len;
 	int			group_id;
@@ -92,6 +94,7 @@ struct alua_port_group {
 };
 
 struct alua_dh_data {
+	struct list_head	node;
 	struct alua_port_group	*pg;
 	int			group_id;
 	spinlock_t		pg_lock;
@@ -247,6 +250,7 @@ struct alua_port_group *alua_alloc_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);
 
 	spin_lock(&port_group_lock);
@@ -328,6 +332,8 @@ static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h,
 {
 	int rel_port = -1, group_id;
 	struct alua_port_group *pg, *old_pg = NULL;
+	bool pg_updated;
+	unsigned long flags;
 
 	group_id = scsi_vpd_tpg_id(sdev, &rel_port);
 	if (group_id < 0) {
@@ -357,10 +363,22 @@ static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h,
 	old_pg = h->pg;
 	if (old_pg != pg) {
 		/* port group has changed. Update to new port group */
+		if (h->pg) {
+			spin_lock_irqsave(&old_pg->lock, flags);
+			list_del_rcu(&h->node);
+			spin_unlock_irqrestore(&old_pg->lock, flags);
+		}
 		rcu_assign_pointer(h->pg, pg);
+		pg_updated = true;
 	}
+
+	spin_lock_irqsave(&pg->lock, flags);
 	if (sdev->synchronous_alua)
 		pg->flags |= ALUA_SYNC_STPG;
+	if (pg_updated)
+		list_add_rcu(&h->node, &pg->dh_list);
+	spin_unlock_irqrestore(&pg->lock, flags);
+
 	alua_rtpg_queue(h->pg, sdev, NULL, true);
 	spin_unlock(&h->pg_lock);
 
@@ -613,8 +631,18 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
 			if (spin_trylock_irqsave(&tmp_pg->lock, flags)) {
 				if ((tmp_pg == pg) ||
 				    !(tmp_pg->flags & ALUA_PG_RUNNING)) {
+					struct alua_dh_data *h;
+
 					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) {
+						/* h->sdev should always be valid */
+						BUG_ON(!h->sdev);
+						h->sdev->access_state = desc[0];
+					}
+					rcu_read_unlock();
 				}
 				if (tmp_pg == pg)
 					valid_states = desc[1];
@@ -645,10 +673,22 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
 			pg->interval = 2;
 			err = SCSI_DH_RETRY;
 		} else {
+			struct alua_dh_data *h;
+
 			/* Transitioning time exceeded, set port to standby */
 			err = SCSI_DH_IO;
 			pg->state = SCSI_ACCESS_STATE_STANDBY;
 			pg->expiry = 0;
+			rcu_read_lock();
+			list_for_each_entry_rcu(h, &pg->dh_list, node) {
+				BUG_ON(!h->sdev);
+				h->sdev->access_state =
+					(pg->state & SCSI_ACCESS_STATE_MASK);
+				if (pg->pref)
+					h->sdev->access_state |=
+						SCSI_ACCESS_STATE_PREFERRED;
+			}
+			rcu_read_unlock();
 		}
 		break;
 	case SCSI_ACCESS_STATE_OFFLINE:
@@ -1041,6 +1081,7 @@ static int alua_bus_attach(struct scsi_device *sdev)
 	rcu_assign_pointer(h->pg, NULL);
 	h->init_error = SCSI_DH_OK;
 	h->sdev = sdev;
+	INIT_LIST_HEAD(&h->node);
 
 	mutex_init(&h->init_mutex);
 	err = alua_initialize(sdev, h);
@@ -1070,9 +1111,12 @@ static void alua_bus_detach(struct scsi_device *sdev)
 	rcu_assign_pointer(h->pg, NULL);
 	h->sdev = NULL;
 	spin_unlock(&h->pg_lock);
-	if (pg)
+	if (pg) {
+		spin_lock(&pg->lock);
+		list_del_rcu(&h->node);
+		spin_unlock(&pg->lock);
 		kref_put(&pg->kref, release_port_group);
-
+	}
 	sdev->handler_data = NULL;
 	kfree(h);
 }
-- 
1.8.5.6

[PATCHv8 23/23] scsi_dh_alua: Update version to 2.0

[Hannes Reinecke]

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index fc77765..5bcdf8d 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -30,7 +30,7 @@
 #include <scsi/scsi_dh.h>
 
 #define ALUA_DH_NAME "alua"
-#define ALUA_DH_VER "1.3"
+#define ALUA_DH_VER "2.0"
 
 #define TPGS_SUPPORT_NONE		0x00
 #define TPGS_SUPPORT_OPTIMIZED		0x01
-- 
1.8.5.6

Re: [PATCHv8 20/23] scsi: Add 'access_state' attribute

[Bart Van Assche]

On 02/19/2016 12:17 AM, Hannes Reinecke wrote:
> +static ssize_t
> +sdev_show_access_state(struct device *dev,
> +		       struct device_attribute *attr,
> +		       char *buf)
> +{
> +	struct scsi_device *sdev = to_scsi_device(dev);
> +	unsigned char access_state;
> +	const char *access_state_name;
> +	bool pref = false;
> +
> +	if (!sdev->handler)
> +		return -EINVAL;
> +
> +	if (sdev->access_state & SCSI_ACCESS_STATE_PREFERRED)
> +		pref = true;
> +
> +	access_state = (sdev->access_state & SCSI_ACCESS_STATE_MASK);
> +	access_state_name = scsi_access_state_name(access_state);
> +
> +	return snprintf(buf, 32, "%s%s\n",
> +			access_state_name ? access_state_name : "unknown",
> +			pref ? " preferred" : "");
> +}

Hello Hannes,

What is inelegant about the above approach is that the access_state attribute
is added to all SCSI devices, whether or not a device handler has been attached,
and that reading that attribute doesn't fail for devices to which another handler
than the ALUA handler has been attached. How about the patch below, which moves
the access_state show handler to the scsi_dh_alua.c source file, where it belongs?

[PATCH] Restrict access_state attribute to devices that support ALUA

---
 drivers/scsi/device_handler/scsi_dh_alua.c | 52 +++++++++++++++++++++++++++++
 drivers/scsi/scsi_dh.c                     | 14 ++++++++
 drivers/scsi/scsi_sysfs.c                  | 53 ------------------------------
 include/scsi/scsi_dh.h                     |  1 +
 4 files changed, 67 insertions(+), 53 deletions(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index 5bcdf8d..e64f6f6 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -1121,6 +1121,57 @@ static void alua_bus_detach(struct scsi_device *sdev)
 	kfree(h);
 }
 
+static const struct {
+	unsigned char	value;
+	const char	*name;
+} sdev_access_states[] = {
+	{ SCSI_ACCESS_STATE_OPTIMAL,		"active/optimized" },
+	{ SCSI_ACCESS_STATE_ACTIVE,		"active/non-optimized" },
+	{ SCSI_ACCESS_STATE_STANDBY,		"standby" },
+	{ SCSI_ACCESS_STATE_UNAVAILABLE,	"unavailable" },
+	{ SCSI_ACCESS_STATE_LBA,		"lba-dependent" },
+	{ SCSI_ACCESS_STATE_OFFLINE,		"offline" },
+	{ SCSI_ACCESS_STATE_TRANSITIONING,	"transitioning" },
+};
+
+const char *scsi_access_state_name(unsigned char state)
+{
+	int i;
+	const char *name = NULL;
+
+	for (i = 0; i < ARRAY_SIZE(sdev_access_states); i++) {
+		if (sdev_access_states[i].value == state) {
+			name = sdev_access_states[i].name;
+			break;
+		}
+	}
+	return name;
+}
+
+static ssize_t
+sdev_show_access_state(struct device *dev,
+		       struct device_attribute *attr,
+		       char *buf)
+{
+	struct scsi_device *sdev = to_scsi_device(dev);
+	unsigned char access_state;
+	const char *access_state_name;
+	bool pref = sdev->access_state & SCSI_ACCESS_STATE_PREFERRED;
+
+	access_state = sdev->access_state & SCSI_ACCESS_STATE_MASK;
+	access_state_name = scsi_access_state_name(access_state);
+
+	return snprintf(buf, 32, "%s%s\n",
+			access_state_name ? access_state_name : "unknown",
+			pref ? " preferred" : "");
+}
+static DEVICE_ATTR(access_state, S_IRUGO, sdev_show_access_state, NULL);
+
+static const struct attribute *alua_attrs[] = {
+	&dev_attr_access_state.attr,
+	NULL
+};
+
 static struct scsi_device_handler alua_dh = {
 	.name = ALUA_DH_NAME,
 	.module = THIS_MODULE,
@@ -1131,6 +1182,7 @@ static struct scsi_device_handler alua_dh = {
 	.activate = alua_activate,
 	.rescan = alua_rescan,
 	.set_params = alua_set_params,
+	.attrs = alua_attrs,
 };
 
 static int __init alua_init(void)
diff --git a/drivers/scsi/scsi_dh.c b/drivers/scsi/scsi_dh.c
index 54d446c..73cab23 100644
--- a/drivers/scsi/scsi_dh.c
+++ b/drivers/scsi/scsi_dh.c
@@ -164,6 +167,17 @@ int scsi_dh_add_device(struct scsi_device *sdev)
 		devinfo = __scsi_dh_lookup(drv);
 	if (devinfo)
 		err = scsi_dh_handler_attach(sdev, devinfo);
+	if (err == 0 && sdev->handler && sdev->handler->attrs) {
+		err = sysfs_create_files(&sdev->sdev_gendev.kobj,
+					 sdev->handler->attrs);
+		if (err) {
+			sdev_printk(KERN_INFO, sdev,
+			"failed to add device handler sysfs attributes: %d\n",
+				    err);
+			scsi_dh_handler_detach(sdev);
+		}
+	}
+
 	return err;
 }
 
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 8551707..00bc721 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -81,33 +81,6 @@ const char *scsi_host_state_name(enum scsi_host_state state)
 	return name;
 }
 
-static const struct {
-	unsigned char	value;
-	char		*name;
-} sdev_access_states[] = {
-	{ SCSI_ACCESS_STATE_OPTIMAL, "active/optimized" },
-	{ SCSI_ACCESS_STATE_ACTIVE, "active/non-optimized" },
-	{ SCSI_ACCESS_STATE_STANDBY, "standby" },
-	{ SCSI_ACCESS_STATE_UNAVAILABLE, "unavailable" },
-	{ SCSI_ACCESS_STATE_LBA, "lba-dependent" },
-	{ SCSI_ACCESS_STATE_OFFLINE, "offline" },
-	{ SCSI_ACCESS_STATE_TRANSITIONING, "transitioning" },
-};
-
-const char *scsi_access_state_name(unsigned char state)
-{
-	int i;
-	char *name = NULL;
-
-	for (i = 0; i < ARRAY_SIZE(sdev_access_states); i++) {
-		if (sdev_access_states[i].value == state) {
-			name = sdev_access_states[i].name;
-			break;
-		}
-	}
-	return name;
-}
-
 static int check_set(unsigned long long *val, char *src)
 {
 	char *last;
@@ -1000,31 +973,6 @@ sdev_store_dh_state(struct device *dev, struct device_attribute *attr,
 
 static DEVICE_ATTR(dh_state, S_IRUGO | S_IWUSR, sdev_show_dh_state,
 		   sdev_store_dh_state);
-
-static ssize_t
-sdev_show_access_state(struct device *dev,
-		       struct device_attribute *attr,
-		       char *buf)
-{
-	struct scsi_device *sdev = to_scsi_device(dev);
-	unsigned char access_state;
-	const char *access_state_name;
-	bool pref = false;
-
-	if (!sdev->handler)
-		return -EINVAL;
-
-	if (sdev->access_state & SCSI_ACCESS_STATE_PREFERRED)
-		pref = true;
-
-	access_state = (sdev->access_state & SCSI_ACCESS_STATE_MASK);
-	access_state_name = scsi_access_state_name(access_state);
-
-	return snprintf(buf, 32, "%s%s\n",
-			access_state_name ? access_state_name : "unknown",
-			pref ? " preferred" : "");
-}
-static DEVICE_ATTR(access_state, S_IRUGO, sdev_show_access_state, NULL);
 #endif
 
 static ssize_t
@@ -1099,7 +1047,6 @@ static struct attribute *scsi_sdev_attrs[] = {
 	&dev_attr_wwid.attr,
 #ifdef CONFIG_SCSI_DH
 	&dev_attr_dh_state.attr,
-	&dev_attr_access_state.attr,
 #endif
 	&dev_attr_queue_ramp_up_period.attr,
 	REF_EVT(media_change),
diff --git a/include/scsi/scsi_dh.h b/include/scsi/scsi_dh.h
index c7bba2b..4a600c6 100644
--- a/include/scsi/scsi_dh.h
+++ b/include/scsi/scsi_dh.h
@@ -72,6 +72,7 @@ struct scsi_device_handler {
 	int (*prep_fn)(struct scsi_device *, struct request *);
 	int (*set_params)(struct scsi_device *, const char *);
 	void (*rescan)(struct scsi_device *);
+	const struct attribute **attrs;
 };
 
 #ifdef CONFIG_SCSI_DH
-- 
2.7.1

Re: [PATCHv8 20/23] scsi: Add 'access_state' attribute

[Hannes Reinecke]

On 02/19/2016 08:10 PM, Bart Van Assche wrote:
> On 02/19/2016 12:17 AM, Hannes Reinecke wrote:
>> +static ssize_t
>> +sdev_show_access_state(struct device *dev,
>> +		       struct device_attribute *attr,
>> +		       char *buf)
>> +{
>> +	struct scsi_device *sdev = to_scsi_device(dev);
>> +	unsigned char access_state;
>> +	const char *access_state_name;
>> +	bool pref = false;
>> +
>> +	if (!sdev->handler)
>> +		return -EINVAL;
>> +
>> +	if (sdev->access_state & SCSI_ACCESS_STATE_PREFERRED)
>> +		pref = true;
>> +
>> +	access_state = (sdev->access_state & SCSI_ACCESS_STATE_MASK);
>> +	access_state_name = scsi_access_state_name(access_state);
>> +
>> +	return snprintf(buf, 32, "%s%s\n",
>> +			access_state_name ? access_state_name : "unknown",
>> +			pref ? " preferred" : "");
>> +}
>
> Hello Hannes,
>
> What is inelegant about the above approach is that the access_state attribute
> is added to all SCSI devices, whether or not a device handler has been attached,
> and that reading that attribute doesn't fail for devices to which another handler
> than the ALUA handler has been attached. How about the patch below, which moves
> the access_state show handler to the scsi_dh_alua.c source file, where it belongs?
>
Actually, this was my first approach, but hch suggested moving it to
the generic code :-(

Also when using your suggestion the 'access_state' attribute will only 
be created _after_ the 'ADD' uevent, making it impossible to use it from 
udev events.

However, I'm currently working on using the 'is_visible' callback for 
SCSI sysfs attributes for this; in theory it should be possible to
use 'sysfs_update_groups()' during scsi_add_lun() to blank out the
unsupported attributes.

Which I think might be the best approach here.

But probably not for this patch series; I'd rather have the alua update 
in first as it took long enough.

If you're absolutely against it we can drop the 'access_state' patches
(ie patch 20-22) and have them folded into a separate patchset.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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Re: [PATCHv8 20/23] scsi: Add 'access_state' attribute

[Bart Van Assche]

On 02/20/16 00:03, Hannes Reinecke wrote:
> Also when using your suggestion the 'access_state' attribute will only
> be created _after_ the 'ADD' uevent, making it impossible to use it from
> udev events.

Can you give an example in which it would be useful to read the ALUA 
state from a udev handler ? I'm not sure such an example exists.

> If you're absolutely against it we can drop the 'access_state' patches
> (ie patch 20-22) and have them folded into a separate patchset.

That sounds like a good idea to me.

Thanks,

Bart.

Re: [PATCHv8 20/23] scsi: Add 'access_state' attribute

[Hannes Reinecke]

On 02/20/2016 04:16 PM, Bart Van Assche wrote:
> On 02/20/16 00:03, Hannes Reinecke wrote:
>> Also when using your suggestion the 'access_state' attribute will only
>> be created _after_ the 'ADD' uevent, making it impossible to use it from
>> udev events.
>
> Can you give an example in which it would be useful to read the ALUA
> state from a udev handler ? I'm not sure such an example exists.
>
When evaluating the 'access_state' from an uevent we can avoid sending 
I/O if the path is unavailable; eg if the path is in 'transitioning' I/O 
will be queued until that path becomes available again.
Which means that the uevent will be delayed during udev processing, so 
that the event will never be read by multipathing (as it's being invoked
only after udev event processing has finished).
And in extreme cases (like OnTap takeover/giveback) it will even drop 
the event completely due to a timeout.

>> If you're absolutely against it we can drop the 'access_state' patches
>> (ie patch 20-22) and have them folded into a separate patchset.
>
> That sounds like a good idea to me.
>
Ok, let's do this.

Martin, can you please ignore patches 20-22 when pulling the patchset?
I'll be resubmitting a new patchset with them once these issues are 
sorted out.
Or do you need a new patch submission?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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Re: [PATCHv8 20/23] scsi: Add 'access_state' attribute

[Martin K. Petersen]

>>>>> "Hannes" == Hannes Reinecke <hare@suse.de> writes:

Hannes> Martin, can you please ignore patches 20-22 when pulling the
Hannes> patchset?  I'll be resubmitting a new patchset with them once
Hannes> these issues are sorted out.  Or do you need a new patch
Hannes> submission?

No, it's OK. I'll merge the first part of the series in the morning.

-- 
Martin K. Petersen	Oracle Linux Engineering

Re: [PATCHv8 20/23] scsi: Add 'access_state' attribute

[Bart Van Assche]

On 02/21/16 00:27, Hannes Reinecke wrote:
> On 02/20/2016 04:16 PM, Bart Van Assche wrote:
>> On 02/20/16 00:03, Hannes Reinecke wrote:
>>> Also when using your suggestion the 'access_state' attribute will only
>>> be created _after_ the 'ADD' uevent, making it impossible to use it from
>>> udev events.
>>
>> Can you give an example in which it would be useful to read the ALUA
>> state from a udev handler ? I'm not sure such an example exists.
>>
> When evaluating the 'access_state' from an uevent we can avoid sending
> I/O if the path is unavailable; eg if the path is in 'transitioning' I/O
> will be queued until that path becomes available again.
> Which means that the uevent will be delayed during udev processing, so
> that the event will never be read by multipathing (as it's being invoked
> only after udev event processing has finished).
> And in extreme cases (like OnTap takeover/giveback) it will even drop
> the event completely due to a timeout.

Hello Hannes,

Thanks for the feedback.

Please split the access_state attribute in two sysfs attributes - one 
for the ALUA state and one for the "preferred" state. This will make it 
easier for shell scripts to process these sysfs attributes.

I agree with using the 'is_visible' callback. But since using that 
callback will cause the ALUA sysfs attributes to become only visible 
after the ALUA handler has been attached I don't see why not to move the 
implementation of the ALUA sysfs attributes into the ALUA device handler 
source file.

BTW, since the ALUA state can change at any time after the access_state 
sysfs attribute has been read and before I/O is submitted my preference 
is to avoid triggering any SCSI commands from a udev rule that depend on 
the ALUA state.

Bart.

Re: [PATCHv8 20/23] scsi: Add 'access_state' attribute

[Hannes Reinecke]

On 02/22/2016 05:45 AM, Bart Van Assche wrote:
> On 02/21/16 00:27, Hannes Reinecke wrote:
>> On 02/20/2016 04:16 PM, Bart Van Assche wrote:
>>> On 02/20/16 00:03, Hannes Reinecke wrote:
>>>> Also when using your suggestion the 'access_state' attribute will only
>>>> be created _after_ the 'ADD' uevent, making it impossible to use it
>>>> from
>>>> udev events.
>>>
>>> Can you give an example in which it would be useful to read the ALUA
>>> state from a udev handler ? I'm not sure such an example exists.
>>>
>> When evaluating the 'access_state' from an uevent we can avoid sending
>> I/O if the path is unavailable; eg if the path is in 'transitioning' I/O
>> will be queued until that path becomes available again.
>> Which means that the uevent will be delayed during udev processing, so
>> that the event will never be read by multipathing (as it's being invoked
>> only after udev event processing has finished).
>> And in extreme cases (like OnTap takeover/giveback) it will even drop
>> the event completely due to a timeout.
> 
> Hello Hannes,
> 
> Thanks for the feedback.
> 
> Please split the access_state attribute in two sysfs attributes - one
> for the ALUA state and one for the "preferred" state. This will make it
> easier for shell scripts to process these sysfs attributes.
> 
Okay, agreed.

> I agree with using the 'is_visible' callback. But since using that
> callback will cause the ALUA sysfs attributes to become only visible
> after the ALUA handler has been attached I don't see why not to move the
> implementation of the ALUA sysfs attributes into the ALUA device handler
> source file.
> 
Thing is, there are others (like the vpg_pg attributes) which will
benefit from using the 'is_visible' callback. And move the
'access_state' attribute into the generic functions makes the footprint
smaller, as the required infrastructure is already present.
Plus I would really like to have the 'access_state' variable part of the
scsi_device, to avoid the intrinsics of having to look it up from the
device_handler data.

> BTW, since the ALUA state can change at any time after the access_state
> sysfs attribute has been read and before I/O is submitted my preference
> is to avoid triggering any SCSI commands from a udev rule that depend on
> the ALUA state.
> 
Yes, I thought about it some more, too.
The main reason why I need the 'access_state' attribute is to decouple
the multipath daemon; at the moment the multipath daemon has to issue
REPORT TARGET PORT GROUPS frequently to figure out the status, which is
causing quite some load on the target. When using the 'access_state'
attribute we would avoid doing I/O for that and have a consistent view,
both on the kernel and the multipath daemon side.

But it's actually a good thing to have the 'access_state' patch in a
different series; I've got some more patches converting the remaining
device_handler to also supply the 'access_state' values.
Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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Re: [PATCHv8 20/23] scsi: Add 'access_state' attribute

[Bart Van Assche]

On 02/21/16 22:59, Hannes Reinecke wrote:
> The main reason why I need the 'access_state' attribute is to decouple
> the multipath daemon; at the moment the multipath daemon has to issue
> REPORT TARGET PORT GROUPS frequently to figure out the status, which is
> causing quite some load on the target. When using the 'access_state'
> attribute we would avoid doing I/O for that and have a consistent view,
> both on the kernel and the multipath daemon side.
>
> But it's actually a good thing to have the 'access_state' patch in a
> different series; I've got some more patches converting the remaining
> device_handler to also supply the 'access_state' values.

Hello Hannes,

The above sounds very interesting to me. Will multipathd recognize at 
run-time whether or not the kernel supports the sysfs ALUA state 
attribute ? Will ALUA state changes be reported through udev or will 
multipathd poll the sysfs ALUA state attributes ? And if the netlink 
buffer that is used in multipathd to receive udev events overflows 
(ENOBUFS), will multipathd resynchronize its state ? As far as I can see 
in source file libmultipath/uevent.c today multipathd ignores netlink 
buffer overflows.

Thanks,

Bart.

Re: [PATCHv8 20/23] scsi: Add 'access_state' attribute

[Hannes Reinecke]

On 02/22/2016 11:34 PM, Bart Van Assche wrote:
> On 02/21/16 22:59, Hannes Reinecke wrote:
>> The main reason why I need the 'access_state' attribute is to decouple
>> the multipath daemon; at the moment the multipath daemon has to issue
>> REPORT TARGET PORT GROUPS frequently to figure out the status, which is
>> causing quite some load on the target. When using the 'access_state'
>> attribute we would avoid doing I/O for that and have a consistent view,
>> both on the kernel and the multipath daemon side.
>>
>> But it's actually a good thing to have the 'access_state' patch in a
>> different series; I've got some more patches converting the remaining
>> device_handler to also supply the 'access_state' values.
> 
> Hello Hannes,
> 
> The above sounds very interesting to me. Will multipathd recognize at
> run-time whether or not the kernel supports the sysfs ALUA state
> attribute ?
That was the plan.
(Not that I've got any idea _how_ to do this ATM :-)

> Will ALUA state changes be reported through udev or will
> multipathd poll the sysfs ALUA state attributes ? 
Polling. udev events will be too unreliable here, as each uevent
potentially causes I/O during uevent processing which might stall as the
path might be down.
So we might never get events for failed/transitioning paths, however,
these are precisely the cases which we're interested in ...

> And if the netlink
> buffer that is used in multipathd to receive udev events overflows
> (ENOBUFS), will multipathd resynchronize its state ? As far as I can see
> in source file libmultipath/uevent.c today multipathd ignores netlink
> buffer overflows.
> 
Which, thankfully, doesn't apply as multipathd will be polling the sysfs
attribute directly :-)

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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Re: [PATCHv8 20/23] scsi: Add 'access_state' attribute

[Ewan Milne]

On Tue, 2016-02-23 at 18:27 +0800, Hannes Reinecke wrote:
> On 02/22/2016 11:34 PM, Bart Van Assche wrote:
> > On 02/21/16 22:59, Hannes Reinecke wrote:
> >> The main reason why I need the 'access_state' attribute is to decouple
> >> the multipath daemon; at the moment the multipath daemon has to issue
> >> REPORT TARGET PORT GROUPS frequently to figure out the status, which is
> >> causing quite some load on the target. When using the 'access_state'
> >> attribute we would avoid doing I/O for that and have a consistent view,
> >> both on the kernel and the multipath daemon side.
> >>
> >> But it's actually a good thing to have the 'access_state' patch in a
> >> different series; I've got some more patches converting the remaining
> >> device_handler to also supply the 'access_state' values.
> > 
> > Hello Hannes,
> > 
> > The above sounds very interesting to me. Will multipathd recognize at
> > run-time whether or not the kernel supports the sysfs ALUA state
> > attribute ?
> That was the plan.
> (Not that I've got any idea _how_ to do this ATM :-)
> 
> > Will ALUA state changes be reported through udev or will
> > multipathd poll the sysfs ALUA state attributes ? 
> Polling. udev events will be too unreliable here, as each uevent
> potentially causes I/O during uevent processing which might stall as the
> path might be down.
> So we might never get events for failed/transitioning paths, however,
> these are precisely the cases which we're interested in ...

And, in fact, if paths go down due to e.g. an FC switch failure, it is
common for a large number of paths to go down at once, causing a large
number of uevents to be queued.

> 
> > And if the netlink
> > buffer that is used in multipathd to receive udev events overflows
> > (ENOBUFS), will multipathd resynchronize its state ? As far as I can see
> > in source file libmultipath/uevent.c today multipathd ignores netlink
> > buffer overflows.
> > 
> Which, thankfully, doesn't apply as multipathd will be polling the sysfs
> attribute directly :-)
> 
> Cheers,
> 
> Hannes

Re: [PATCHv8 00/23] ALUA device handler update, part II

[Martin K. Petersen]

>>>>> "Hannes" == Hannes Reinecke <hare@suse.de> writes:

Hannes> As promised here is now the second part of my ALUA device
Hannes> handler update.  This contains a major rework of the ALUA device
Hannes> handler as execution is moved onto a workqueue. This has the
Hannes> advantage that we avoid having to do multiple calls to the same
Hannes> LUN (as happens frequently when failing over a LUN with several
Hannes> paths) and finally retries are handled correctly.  As some
Hannes> arrays are only capable of handling one STPG at a time I've
Hannes> added a blacklist flag which then uses a singlethreaded
Hannes> workqueue, thereby effectively synchronize STPG handling.
Hannes> Thanks to Bart for this suggestion.

Applied 1-19 and 23 to 4.6/scsi-queue.

-- 
Martin K. Petersen	Oracle Linux Engineering