From: Chandra Seetharaman <sekharan@xxxxxxxxxx>
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.
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.
The 'pg_init_delay_msecs' feature may be provided during table create or
load, e.g.:
echo "0 20971520 multipath 3 queue_if_no_path pg_init_delay_msecs 2500
..." | dmsetup create 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@xxxxxxx>
Signed-off-by: Chandra Seetharaman <sekharan@xxxxxxxxxx>
Acked-by: Mike Christie <michaelc@xxxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
---
drivers/md/dm-mpath.c | 48 ++++++++++++++++++++++++++++++++++++++----------
1 file changed, 38 insertions(+), 10 deletions(-)
v4:
. bumped target version from 1.1.1 to 1.2.0 (user visible change)
. default 'pg_init_delay_msecs' to -1 so we know if user feature arg
was provided
. allow user to specify a pg_init_delay_msecs of 0 (to disable delay)
v3:
. renamed 'pg_init_delay' to 'pg_init_delay_retry'
. switched 'pg_init_delay_secs' to 'pg_init_delay_msecs' and use
msecs_to_jiffies() -- DM targets expect time in milliseconds
. moved 'pg_init_wait' in 'struct multipath' to avoid creating 2 new
4-byte holes when introducing new members
Index: linux-2.6/drivers/md/dm-mpath.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-mpath.c
+++ linux-2.6/drivers/md/dm-mpath.c
@@ -23,6 +23,7 @@
#define DM_MSG_PREFIX "multipath"
#define MESG_STR(x) x, sizeof(x)
+#define DM_PG_INIT_DELAY_MSECS 2000
/* Path properties */
struct pgpath {
@@ -33,7 +34,7 @@ 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 +65,15 @@ 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 +86,7 @@ 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 */
+ int pg_init_delay_msecs; /* Number of msecs before pg_init retry */
struct work_struct process_queued_ios;
struct list_head queued_ios;
@@ -127,7 +133,7 @@ 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 +194,7 @@ 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 = -1;
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 +234,20 @@ 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 != -1 ?
+ 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 + 1, 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 != -1) * 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 != -1)
+ 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,
--
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