[dm-devel] [PATCH 2/5] dm-multipath: push back requests instead of queueing
Hannes Reinecke
hare at suse.de
Fri Jan 31 09:10:41 UTC 2014
There is no reason why multipath needs to queue requests
internally for queue_if_no_path or pg_init; we should
rather push them back onto the request queue.
And while we're at it we can simplify the conditional
statement in map_io() to make it easier to read.
Cc: Mike Snitzer <snitzer at redhat.com>
Cc: Jun'ichi Nomura <j-nomura at ce.jp.nec.com>
Signed-off-by: Hannes Reinecke <hare at suse.de>
---
drivers/md/dm-mpath.c | 115 ++++++++++++++----------------------------
drivers/md/dm.c | 13 +++++
include/linux/device-mapper.h | 1 +
3 files changed, 52 insertions(+), 77 deletions(-)
diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index d45290a..39fd166 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -93,9 +93,7 @@ struct multipath {
unsigned pg_init_count; /* Number of times pg_init called */
unsigned pg_init_delay_msecs; /* Number of msecs before pg_init retry */
- unsigned queue_size;
struct work_struct process_queued_ios;
- struct list_head queued_ios;
struct work_struct trigger_event;
@@ -124,6 +122,7 @@ static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
static void process_queued_ios(struct work_struct *work);
static void trigger_event(struct work_struct *work);
static void activate_path(struct work_struct *work);
+static int __pgpath_busy(struct pgpath *pgpath);
/*-----------------------------------------------
@@ -195,7 +194,6 @@ static struct multipath *alloc_multipath(struct dm_target *ti)
m = kzalloc(sizeof(*m), GFP_KERNEL);
if (m) {
INIT_LIST_HEAD(&m->priority_groups);
- 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;
@@ -368,12 +366,15 @@ failed:
*/
static int __must_push_back(struct multipath *m)
{
- return (m->queue_if_no_path != m->saved_queue_if_no_path &&
- dm_noflush_suspending(m->ti));
+ return (m->queue_if_no_path ||
+ (m->queue_if_no_path != m->saved_queue_if_no_path &&
+ dm_noflush_suspending(m->ti)));
}
+#define pg_ready(m) (!(m)->queue_io && !(m)->pg_init_required)
+
static int map_io(struct multipath *m, struct request *clone,
- union map_info *map_context, unsigned was_queued)
+ union map_info *map_context)
{
int r = DM_MAPIO_REMAPPED;
size_t nr_bytes = blk_rq_bytes(clone);
@@ -391,37 +392,30 @@ static int map_io(struct multipath *m, struct request *clone,
pgpath = m->current_pgpath;
- if (was_queued)
- m->queue_size--;
-
- if (m->pg_init_required) {
- if (!m->pg_init_in_progress)
- queue_work(kmultipathd, &m->process_queued_ios);
- r = DM_MAPIO_REQUEUE;
- } else if ((pgpath && m->queue_io) ||
- (!pgpath && m->queue_if_no_path)) {
- /* Queue for the daemon to resubmit */
- list_add_tail(&clone->queuelist, &m->queued_ios);
- m->queue_size++;
- if (!m->queue_io)
- queue_work(kmultipathd, &m->process_queued_ios);
- pgpath = NULL;
- r = DM_MAPIO_SUBMITTED;
- } else if (pgpath) {
- bdev = pgpath->path.dev->bdev;
- clone->q = bdev_get_queue(bdev);
- clone->rq_disk = bdev->bd_disk;
- } else if (__must_push_back(m))
- r = DM_MAPIO_REQUEUE;
- else
- r = -EIO; /* Failed */
-
- mpio->pgpath = pgpath;
- mpio->nr_bytes = nr_bytes;
-
- if (r == DM_MAPIO_REMAPPED && pgpath->pg->ps.type->start_io)
- pgpath->pg->ps.type->start_io(&pgpath->pg->ps, &pgpath->path,
- nr_bytes);
+ if (pgpath) {
+ if (__pgpath_busy(pgpath))
+ r = DM_MAPIO_REQUEUE;
+ else if (pg_ready(m)) {
+ bdev = pgpath->path.dev->bdev;
+ clone->q = bdev_get_queue(bdev);
+ clone->rq_disk = bdev->bd_disk;
+ mpio->pgpath = pgpath;
+ mpio->nr_bytes = nr_bytes;
+ if (pgpath->pg->ps.type->start_io)
+ pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
+ &pgpath->path,
+ nr_bytes);
+ } else {
+ __pg_init_all_paths(m);
+ r = DM_MAPIO_REQUEUE;
+ }
+ } else {
+ /* No path */
+ if (__must_push_back(m))
+ r = DM_MAPIO_REQUEUE;
+ else
+ r = -EIO; /* Failed */
+ }
spin_unlock_irqrestore(&m->lock, flags);
@@ -443,7 +437,7 @@ static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
else
m->saved_queue_if_no_path = queue_if_no_path;
m->queue_if_no_path = queue_if_no_path;
- if (!m->queue_if_no_path && m->queue_size)
+ if (!m->queue_if_no_path)
queue_work(kmultipathd, &m->process_queued_ios);
spin_unlock_irqrestore(&m->lock, flags);
@@ -451,40 +445,6 @@ static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
return 0;
}
-/*-----------------------------------------------------------------
- * The multipath daemon is responsible for resubmitting queued ios.
- *---------------------------------------------------------------*/
-
-static void dispatch_queued_ios(struct multipath *m)
-{
- int r;
- unsigned long flags;
- union map_info *info;
- struct request *clone, *n;
- LIST_HEAD(cl);
-
- spin_lock_irqsave(&m->lock, flags);
- list_splice_init(&m->queued_ios, &cl);
- spin_unlock_irqrestore(&m->lock, flags);
-
- list_for_each_entry_safe(clone, n, &cl, queuelist) {
- list_del_init(&clone->queuelist);
-
- info = dm_get_rq_mapinfo(clone);
-
- r = map_io(m, clone, info, 1);
- if (r < 0) {
- clear_mapinfo(m, info);
- dm_kill_unmapped_request(clone, r);
- } else if (r == DM_MAPIO_REMAPPED)
- dm_dispatch_request(clone);
- else if (r == DM_MAPIO_REQUEUE) {
- clear_mapinfo(m, info);
- dm_requeue_unmapped_request(clone);
- }
- }
-}
-
static void process_queued_ios(struct work_struct *work)
{
struct multipath *m =
@@ -510,7 +470,7 @@ static void process_queued_ios(struct work_struct *work)
spin_unlock_irqrestore(&m->lock, flags);
if (!must_queue)
- dispatch_queued_ios(m);
+ dm_table_run_queue(m->ti->table);
}
/*
@@ -988,7 +948,7 @@ static int multipath_map(struct dm_target *ti, struct request *clone,
return DM_MAPIO_REQUEUE;
clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
- r = map_io(m, clone, map_context, 0);
+ r = map_io(m, clone, map_context);
if (r < 0 || r == DM_MAPIO_REQUEUE)
clear_mapinfo(m, map_context);
@@ -1057,7 +1017,7 @@ static int reinstate_path(struct pgpath *pgpath)
pgpath->is_active = 1;
- if (!m->nr_valid_paths++ && m->queue_size) {
+ if (!m->nr_valid_paths++) {
m->current_pgpath = NULL;
queue_work(kmultipathd, &m->process_queued_ios);
} else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
@@ -1436,7 +1396,8 @@ static void multipath_status(struct dm_target *ti, status_type_t type,
/* Features */
if (type == STATUSTYPE_INFO)
- DMEMIT("2 %u %u ", m->queue_size, m->pg_init_count);
+ DMEMIT("2 %u %u ", (m->queue_io << 1) + m->queue_if_no_path,
+ m->pg_init_count);
else {
DMEMIT("%u ", m->queue_if_no_path +
(m->pg_init_retries > 0) * 2 +
@@ -1684,7 +1645,7 @@ static int multipath_busy(struct dm_target *ti)
spin_lock_irqsave(&m->lock, flags);
/* pg_init in progress, requeue until done */
- if (m->pg_init_in_progress) {
+ if (!pg_ready(m)) {
busy = 1;
goto out;
}
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 0704c52..291491b 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1912,6 +1912,19 @@ static int dm_any_congested(void *congested_data, int bdi_bits)
return r;
}
+void dm_table_run_queue(struct dm_table *t)
+{
+ struct mapped_device *md = dm_table_get_md(t);
+ unsigned long flags;
+
+ if (md->queue) {
+ spin_lock_irqsave(md->queue->queue_lock, flags);
+ blk_run_queue_async(md->queue);
+ spin_unlock_irqrestore(md->queue->queue_lock, flags);
+ }
+}
+EXPORT_SYMBOL_GPL(dm_table_run_queue);
+
/*-----------------------------------------------------------------
* An IDR is used to keep track of allocated minor numbers.
*---------------------------------------------------------------*/
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index ed419c6..a33653f 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -604,5 +604,6 @@ void dm_dispatch_request(struct request *rq);
void dm_requeue_unmapped_request(struct request *rq);
void dm_kill_unmapped_request(struct request *rq, int error);
int dm_underlying_device_busy(struct request_queue *q);
+void dm_table_run_queue(struct dm_table *t);
#endif /* _LINUX_DEVICE_MAPPER_H */
--
1.7.12.4
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