From: Chandra Seetharaman 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 Signed-off-by: Chandra Seetharaman Acked-by: Mike Christie Signed-off-by: Mike Snitzer Signed-off-by: Alasdair G Kergon --- drivers/md/dm-mpath.c | 48 ++++++++++++++++++++++++++++++++++++++---------- drivers/md/dm-mpath.c | 48 ++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 38 insertions(+), 10 deletions(-) Index: linux-2.6.37/drivers/md/dm-mpath.c =================================================================== --- linux-2.6.37.orig/drivers/md/dm-mpath.c +++ linux-2.6.37/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 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 multip 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 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 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 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 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 */ 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 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_ta 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,