1 files changed, 34 insertions, 7 deletions

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index e54ff372d711..9b16788118d2 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -63,6 +63,7 @@ struct multipath {
         spinlock_t lock;
 
         const char *hw_handler_name;
+        struct work_struct activate_path;
         unsigned nr_priority_groups;
         struct list_head priority_groups;
         unsigned pg_init_required;      /* pg_init needs calling? */
@@ -107,10 +108,10 @@ typedef int (*action_fn) (struct pgpath *pgpath);
 
 static struct kmem_cache *_mpio_cache;
 
-static struct workqueue_struct *kmultipathd;
+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 pg_init_done(struct dm_path *, int);
+static void activate_path(struct work_struct *work);
 
 
 /*-----------------------------------------------
@@ -180,6 +181,7 @@ static struct multipath *alloc_multipath(struct dm_target *ti)
                 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);
@@ -432,11 +434,8 @@ static void process_queued_ios(struct work_struct *work)
 out:
         spin_unlock_irqrestore(&m->lock, flags);
 
-        if (init_required) {
-                struct dm_path *path = &pgpath->path;
-                int ret = scsi_dh_activate(bdev_get_queue(path->dev->bdev));
-                pg_init_done(path, ret);
-        }
+        if (init_required)
+                queue_work(kmpath_handlerd, &m->activate_path);
 
         if (!must_queue)
                 dispatch_queued_ios(m);
@@ -791,6 +790,7 @@ static void multipath_dtr(struct dm_target *ti)
 {
         struct multipath *m = (struct multipath *) ti->private;
 
+        flush_workqueue(kmpath_handlerd);
         flush_workqueue(kmultipathd);
         free_multipath(m);
 }
@@ -1108,6 +1108,17 @@ static void pg_init_done(struct dm_path *path, int errors)
         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 = &m->current_pgpath->path;
+
+        ret = scsi_dh_activate(bdev_get_queue(path->dev->bdev));
+        pg_init_done(path, ret);
+}
+
 /*
  * end_io handling
  */
@@ -1451,6 +1462,21 @@ 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]);
@@ -1462,6 +1488,7 @@ static void __exit dm_multipath_exit(void)
 {
         int r;
 
+        destroy_workqueue(kmpath_handlerd);
         destroy_workqueue(kmultipathd);
 
         r = dm_unregister_target(&multipath_target);