Commit c9e45581 authored by Dave Wysochanski's avatar Dave Wysochanski Committed by Alasdair G Kergon
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dm mpath: add retry pg init 



This patch allows a failed path group initialisation command to be retried.

It adds a generic MP_RETRY flag and a "pg_init_retries" feature to
device-mapper multipath which limits the number of retries.

1. A hw handler sends a path initialization command to the storage and
the command completes with an error code indicating the command
should be retried.

2. The hardware handler calls dm_pg_init_complete() with MP_RETRY
set in err_flags to ask the dm multipath core to retry.

3. If the retry limit has not been exceeded, pg_init() is retried.
Otherwise fail_path() is called.

If you are using the userspace multipath-tools or device-mapper-multipath
package, you can set pg_init_retries in the 'device' section of your
/etc/multipath.conf file. For example:

features                "2 pg_init_retries 7"

The number of PG retries attempted is reported in the 'dmsetup status' output.

Signed-off-by: default avatarDave Wysochanski <dwysocha@redhat.com>
Acked-by: default avatarMike Christie <michaelc@cs.wisc.edu>
Acked-by: default avatarChandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent 636d5786

drivers/md/dm-hw-handler.h

+1 −0
Original line number Diff line number Diff line
@@ -58,5 +58,6 @@ unsigned dm_scsi_err_handler(struct hw_handler *hwh, struct bio *bio); 
#define MP_FAIL_PATH 1

#define MP_BYPASS_PG 2

#define MP_ERROR_IO  4	/* Don't retry this I/O */

#define MP_RETRY 8



#endif

drivers/md/dm-mpath.c

+67 −14
Original line number Diff line number Diff line
@@ -75,6 +75,8 @@ struct multipath { 
	unsigned queue_io;		/* Must we queue all I/O? */

	unsigned queue_if_no_path;	/* Queue I/O if last path fails? */

	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 */



	struct work_struct process_queued_ios;

	struct bio_list queued_ios;
@@ -225,6 +227,8 @@ static void __switch_pg(struct multipath *m, struct pgpath *pgpath) 
		m->pg_init_required = 0;

		m->queue_io = 0;

	}



	m->pg_init_count = 0;

}



static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg)
@@ -424,6 +428,7 @@ static void process_queued_ios(struct work_struct *work) 
		must_queue = 0;



	if (m->pg_init_required && !m->pg_init_in_progress) {

		m->pg_init_count++;

		m->pg_init_required = 0;

		m->pg_init_in_progress = 1;

		init_required = 1;
@@ -689,9 +694,11 @@ static int parse_features(struct arg_set *as, struct multipath *m) 
	int r;

	unsigned argc;

	struct dm_target *ti = m->ti;

	const char *param_name;



	static struct param _params[] = {

		{0, 1, "invalid number of feature args"},

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

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

	};



	r = read_param(_params, shift(as), &argc, &ti->error);
@@ -701,12 +708,28 @@ static int parse_features(struct arg_set *as, struct multipath *m) 
	if (!argc)

		return 0;



	if (!strnicmp(shift(as), MESG_STR("queue_if_no_path")))

		return queue_if_no_path(m, 1, 0);

	else {

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

		return -EINVAL;

	do {

		param_name = shift(as);

		argc--;



		if (!strnicmp(param_name, MESG_STR("queue_if_no_path"))) {

			r = queue_if_no_path(m, 1, 0);

			continue;

		}



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

		    (argc >= 1)) {

			r = read_param(_params + 1, shift(as),

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

			argc--;

			continue;

		}



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

		r = -EINVAL;

	} while (argc && !r);



	return r;

}



static int multipath_ctr(struct dm_target *ti, unsigned int argc,
@@ -975,6 +998,26 @@ static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed) 
	return 0;

}



/*

 * Should we retry pg_init immediately?

 */

static int pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)

{

	unsigned long flags;

	int limit_reached = 0;



	spin_lock_irqsave(&m->lock, flags);



	if (m->pg_init_count <= m->pg_init_retries)

		m->pg_init_required = 1;

	else

		limit_reached = 1;



	spin_unlock_irqrestore(&m->lock, flags);



	return limit_reached;

}



/*

 * pg_init must call this when it has completed its initialisation

 */
@@ -985,8 +1028,14 @@ void dm_pg_init_complete(struct dm_path *path, unsigned err_flags) 
	struct multipath *m = pg->m;

	unsigned long flags;



	/* We insist on failing the path if the PG is already bypassed. */

	if (err_flags && pg->bypassed)

	/*

	 * If requested, retry pg_init until maximum number of retries exceeded.

	 * If retry not requested and PG already bypassed, always fail the path.

	 */

	if (err_flags & MP_RETRY) {

		if (pg_init_limit_reached(m, pgpath))

			err_flags |= MP_FAIL_PATH;

	} else if (err_flags && pg->bypassed)

		err_flags |= MP_FAIL_PATH;



	if (err_flags & MP_FAIL_PATH)
@@ -996,7 +1045,7 @@ void dm_pg_init_complete(struct dm_path *path, unsigned err_flags) 
		bypass_pg(m, pg, 1);



	spin_lock_irqsave(&m->lock, flags);

	if (err_flags) {

	if (err_flags & ~MP_RETRY) {

		m->current_pgpath = NULL;

		m->current_pg = NULL;

	} else if (!m->pg_init_required)
@@ -1148,11 +1197,15 @@ static int multipath_status(struct dm_target *ti, status_type_t type, 


	/* Features */

	if (type == STATUSTYPE_INFO)

		DMEMIT("1 %u ", m->queue_size);

	else if (m->queue_if_no_path)

		DMEMIT("1 queue_if_no_path ");

	else

		DMEMIT("0 ");

		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);

		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 (hwh->type && hwh->type->status)

		sz += hwh->type->status(hwh, type, result + sz, maxlen - sz);

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