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Commit 4e2d19e4 authored by Chandra Seetharaman's avatar Chandra Seetharaman Committed by Alasdair G Kergon
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dm mpath: delay activate_path retry on SCSI_DH_RETRY 



This patch adds a user-configurable 'pg_init_delay_msecs' feature.  Use
this feature to specify the number of milliseconds to delay before
retrying scsi_dh_activate, when SCSI_DH_RETRY is returned.

SCSI Device Handlers return SCSI_DH_IMM_RETRY if we could retry
activation immediately and SCSI_DH_RETRY in cases where it is better to
retry after some delay.

Currently we immediately retry scsi_dh_activate irrespective of
SCSI_DH_IMM_RETRY and SCSI_DH_RETRY.

The 'pg_init_delay_msecs' feature may be provided during table create or
load, e.g.:
    dmsetup create --table "0 20971520 multipath 3 queue_if_no_path \
	pg_init_delay_msecs 2500 ..." mpatha

The default for 'pg_init_delay_msecs' is 2000 milliseconds.
Maximum configurable delay is 60000 milliseconds.  Specifying a
'pg_init_delay_msecs' of 0 will cause immediate retry.

Signed-off-by: default avatarNikanth Karthikesan <knikanth@suse.de>
Signed-off-by: default avatarChandra Seetharaman <sekharan@us.ibm.com>
Acked-by: default avatarMike Christie <michaelc@cs.wisc.edu>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent 052189a2

drivers/md/dm-mpath.c

+38 −10
Original line number Diff line number Diff line
@@ -23,6 +23,8 @@ 


#define DM_MSG_PREFIX "multipath"

#define MESG_STR(x) x, sizeof(x)

#define DM_PG_INIT_DELAY_MSECS 2000

#define DM_PG_INIT_DELAY_DEFAULT ((unsigned) -1)



/* Path properties */

struct pgpath {
@@ -33,7 +35,7 @@ struct pgpath { 
	unsigned fail_count;		/* Cumulative failure count */



	struct dm_path path;

	struct work_struct activate_path;

	struct delayed_work activate_path;

};



#define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
@@ -64,11 +66,15 @@ struct multipath { 


	const char *hw_handler_name;

	char *hw_handler_params;



	unsigned nr_priority_groups;

	struct list_head priority_groups;



	wait_queue_head_t pg_init_wait;	/* Wait for pg_init completion */



	unsigned pg_init_required;	/* pg_init needs calling? */

	unsigned pg_init_in_progress;	/* Only one pg_init allowed at once */

	wait_queue_head_t pg_init_wait;	/* Wait for pg_init completion */

	unsigned pg_init_delay_retry;	/* Delay pg_init retry? */



	unsigned nr_valid_paths;	/* Total number of usable paths */

	struct pgpath *current_pgpath;
@@ -81,6 +87,7 @@ struct multipath { 
	unsigned saved_queue_if_no_path;/* Saved state during suspension */

	unsigned pg_init_retries;	/* Number of times to retry pg_init */

	unsigned pg_init_count;		/* Number of times pg_init called */

	unsigned pg_init_delay_msecs;	/* Number of msecs before pg_init retry */



	struct work_struct process_queued_ios;

	struct list_head queued_ios;
@@ -127,7 +134,7 @@ static struct pgpath *alloc_pgpath(void) 


	if (pgpath) {

		pgpath->is_active = 1;

		INIT_WORK(&pgpath->activate_path, activate_path);

		INIT_DELAYED_WORK(&pgpath->activate_path, activate_path);

	}



	return pgpath;
@@ -188,6 +195,7 @@ static struct multipath *alloc_multipath(struct dm_target *ti) 
		INIT_LIST_HEAD(&m->queued_ios);

		spin_lock_init(&m->lock);

		m->queue_io = 1;

		m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;

		INIT_WORK(&m->process_queued_ios, process_queued_ios);

		INIT_WORK(&m->trigger_event, trigger_event);

		init_waitqueue_head(&m->pg_init_wait);
@@ -227,14 +235,19 @@ static void free_multipath(struct multipath *m) 
static void __pg_init_all_paths(struct multipath *m)

{

	struct pgpath *pgpath;

	unsigned long pg_init_delay = 0;



	m->pg_init_count++;

	m->pg_init_required = 0;

	if (m->pg_init_delay_retry)

		pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?

						 m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);

	list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {

		/* Skip failed paths */

		if (!pgpath->is_active)

			continue;

		if (queue_work(kmpath_handlerd, &pgpath->activate_path))

		if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,

				       pg_init_delay))

			m->pg_init_in_progress++;

	}

}
@@ -782,8 +795,9 @@ static int parse_features(struct arg_set *as, struct multipath *m) 
	const char *param_name;



	static struct param _params[] = {

		{0, 3, "invalid number of feature args"},

		{0, 5, "invalid number of feature args"},

		{1, 50, "pg_init_retries must be between 1 and 50"},

		{0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},

	};



	r = read_param(_params, shift(as), &argc, &ti->error);
@@ -810,6 +824,14 @@ static int parse_features(struct arg_set *as, struct multipath *m) 
			continue;

		}



		if (!strnicmp(param_name, MESG_STR("pg_init_delay_msecs")) &&

		    (argc >= 1)) {

			r = read_param(_params + 2, shift(as),

				       &m->pg_init_delay_msecs, &ti->error);

			argc--;

			continue;

		}



		ti->error = "Unrecognised multipath feature request";

		r = -EINVAL;

	} while (argc && !r);
@@ -1022,7 +1044,7 @@ static int reinstate_path(struct pgpath *pgpath) 
		m->current_pgpath = NULL;

		queue_work(kmultipathd, &m->process_queued_ios);

	} else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {

		if (queue_work(kmpath_handlerd, &pgpath->activate_path))

		if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))

			m->pg_init_in_progress++;

	}
@@ -1157,6 +1179,7 @@ static void pg_init_done(void *data, int errors) 
	struct priority_group *pg = pgpath->pg;

	struct multipath *m = pg->m;

	unsigned long flags;

	unsigned delay_retry = 0;



	/* device or driver problems */

	switch (errors) {
@@ -1181,8 +1204,9 @@ static void pg_init_done(void *data, int errors) 
		 */

		bypass_pg(m, pg, 1);

		break;

	/* TODO: For SCSI_DH_RETRY we should wait a couple seconds */

	case SCSI_DH_RETRY:

		/* Wait before retrying. */

		delay_retry = 1;

	case SCSI_DH_IMM_RETRY:

	case SCSI_DH_RES_TEMP_UNAVAIL:

		if (pg_init_limit_reached(m, pgpath))
@@ -1215,6 +1239,7 @@ static void pg_init_done(void *data, int errors) 
	if (!m->pg_init_required)

		m->queue_io = 0;



	m->pg_init_delay_retry = delay_retry;

	queue_work(kmultipathd, &m->process_queued_ios);



	/*
@@ -1229,7 +1254,7 @@ static void pg_init_done(void *data, int errors) 
static void activate_path(struct work_struct *work)

{

	struct pgpath *pgpath =

		container_of(work, struct pgpath, activate_path);

		container_of(work, struct pgpath, activate_path.work);



	scsi_dh_activate(bdev_get_queue(pgpath->path.dev->bdev),

				pg_init_done, pgpath);
@@ -1370,11 +1395,14 @@ static int multipath_status(struct dm_target *ti, status_type_t type, 
		DMEMIT("2 %u %u ", m->queue_size, m->pg_init_count);

	else {

		DMEMIT("%u ", m->queue_if_no_path +

			      (m->pg_init_retries > 0) * 2);

			      (m->pg_init_retries > 0) * 2 +

			      (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2);

		if (m->queue_if_no_path)

			DMEMIT("queue_if_no_path ");

		if (m->pg_init_retries)

			DMEMIT("pg_init_retries %u ", m->pg_init_retries);

		if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)

			DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);

	}



	if (!m->hw_handler_name || type == STATUSTYPE_INFO)
@@ -1643,7 +1671,7 @@ static int multipath_busy(struct dm_target *ti) 
 *---------------------------------------------------------------*/

static struct target_type multipath_target = {

	.name = "multipath",

	.version = {1, 1, 1},

	.version = {1, 2, 0},

	.module = THIS_MODULE,

	.ctr = multipath_ctr,

	.dtr = multipath_dtr,