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: Nikanth Karthikesan <knikanth@suse.de>
Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Acked-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 38 insertions, 10 deletions

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index 35ab5781f88f..b82d28819e2a 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -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 @@ out:
 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 @@ out:
  *---------------------------------------------------------------*/
 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,