[dm-devel] [PATCH 2/3] scsi_dh: Remove the workqueue used for activate

[Chandra Seetharaman]

Since scsi_dh_activate() has become an asynchronous function,
we do not need a workqueue for submitting scsi_dh_activate().

This patch just removes the workqueue that submits scsi_dh_activate().

---------
Signed-off-by: Chandra Seetharaman <sekharan at us.ibm.com>
---
 drivers/md/dm-mpath.c |   51 ++++----------------------------------------------
 1 file changed, 4 insertions(+), 47 deletions(-)

Index: linux-2.6.29/drivers/md/dm-mpath.c
===================================================================
--- linux-2.6.29.orig/drivers/md/dm-mpath.c
+++ linux-2.6.29/drivers/md/dm-mpath.c
@@ -64,8 +64,6 @@ struct multipath {
 	spinlock_t lock;
 
 	const char *hw_handler_name;
-	struct work_struct activate_path;
-	struct pgpath *pgpath_to_activate;
 	unsigned nr_priority_groups;
 	struct list_head priority_groups;
 	unsigned pg_init_required;	/* pg_init needs calling? */
@@ -110,11 +108,11 @@ typedef int (*action_fn) (struct pgpath
 
 static struct kmem_cache *_mpio_cache;
 
-static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
+static struct workqueue_struct *kmultipathd;
 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 void deactivate_path(struct work_struct *work);
+static void pg_init_done(void *path, int errors);
 
 
 /*-----------------------------------------------
@@ -160,7 +158,6 @@ static struct priority_group *alloc_prio
 
 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 {
-	unsigned long flags;
 	struct pgpath *pgpath, *tmp;
 	struct multipath *m = ti->private;
 
@@ -169,10 +166,6 @@ static void free_pgpaths(struct list_hea
 		if (m->hw_handler_name)
 			scsi_dh_detach(bdev_get_queue(pgpath->path.dev->bdev));
 		dm_put_device(ti, pgpath->path.dev);
-		spin_lock_irqsave(&m->lock, flags);
-		if (m->pgpath_to_activate == pgpath)
-			m->pgpath_to_activate = NULL;
-		spin_unlock_irqrestore(&m->lock, flags);
 		free_pgpath(pgpath);
 	}
 }
@@ -202,7 +195,6 @@ static struct multipath *alloc_multipath
 		m->queue_io = 1;
 		INIT_WORK(&m->process_queued_ios, process_queued_ios);
 		INIT_WORK(&m->trigger_event, trigger_event);
-		INIT_WORK(&m->activate_path, activate_path);
 		m->mpio_pool = mempool_create_slab_pool(MIN_IOS, _mpio_cache);
 		if (!m->mpio_pool) {
 			kfree(m);
@@ -446,7 +438,6 @@ static void process_queued_ios(struct wo
 		must_queue = 0;
 
 	if (m->pg_init_required && !m->pg_init_in_progress && pgpath) {
-		m->pgpath_to_activate = pgpath;
 		m->pg_init_count++;
 		m->pg_init_required = 0;
 		m->pg_init_in_progress = 1;
@@ -457,7 +448,8 @@ out:
 	spin_unlock_irqrestore(&m->lock, flags);
 
 	if (init_required)
-		queue_work(kmpath_handlerd, &m->activate_path);
+		scsi_dh_activate(bdev_get_queue(pgpath->path.dev->bdev),
+						 pg_init_done, &pgpath->path);
 
 	if (!must_queue)
 		dispatch_queued_ios(m);
@@ -834,7 +826,6 @@ static void multipath_dtr(struct dm_targ
 {
 	struct multipath *m = (struct multipath *) ti->private;
 
-	flush_workqueue(kmpath_handlerd);
 	flush_workqueue(kmultipathd);
 	free_multipath(m);
 }
@@ -1116,24 +1107,6 @@ static void pg_init_done(void *data, int
 	spin_unlock_irqrestore(&m->lock, flags);
 }
 
-static void activate_path(struct work_struct *work)
-{
-	int ret;
-	struct multipath *m =
-		container_of(work, struct multipath, activate_path);
-	struct dm_path *path;
-	unsigned long flags;
-
-	spin_lock_irqsave(&m->lock, flags);
-	path = &m->pgpath_to_activate->path;
-	m->pgpath_to_activate = NULL;
-	spin_unlock_irqrestore(&m->lock, flags);
-	if (!path)
-		return;
-	ret = scsi_dh_activate(bdev_get_queue(path->dev->bdev),
-				pg_init_done, path);
-}
-
 /*
  * end_io handling
  */
@@ -1471,21 +1444,6 @@ static int __init dm_multipath_init(void
 		return -ENOMEM;
 	}
 
-	/*
-	 * A separate workqueue is used to handle the device handlers
-	 * to avoid overloading existing workqueue. Overloading the
-	 * old workqueue would also create a bottleneck in the
-	 * path of the storage hardware device activation.
-	 */
-	kmpath_handlerd = create_singlethread_workqueue("kmpath_handlerd");
-	if (!kmpath_handlerd) {
-		DMERR("failed to create workqueue kmpath_handlerd");
-		destroy_workqueue(kmultipathd);
-		dm_unregister_target(&multipath_target);
-		kmem_cache_destroy(_mpio_cache);
-		return -ENOMEM;
-	}
-
 	DMINFO("version %u.%u.%u loaded",
 	       multipath_target.version[0], multipath_target.version[1],
 	       multipath_target.version[2]);
@@ -1495,7 +1453,6 @@ static int __init dm_multipath_init(void
 
 static void __exit dm_multipath_exit(void)
 {
-	destroy_workqueue(kmpath_handlerd);
 	destroy_workqueue(kmultipathd);
 
 	dm_unregister_target(&multipath_target);