Remove an unused workqueue and associated kernel thread.

The "ksnapd" thread is never used in this snapshot implementation (data copies
are done with kcopyd), so it can be removed.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

---
 drivers/md/dm-snap.c |   34 ----------------------------------
 drivers/md/dm-snap.h |   10 ----------
 2 files changed, 44 deletions(-)

Index: linux-2.6.28-rc5-devel/drivers/md/dm-snap.c
===================================================================
--- linux-2.6.28-rc5-devel.orig/drivers/md/dm-snap.c	2008-11-25 16:08:59.000000000 +0100
+++ linux-2.6.28-rc5-devel/drivers/md/dm-snap.c	2008-11-25 16:10:10.000000000 +0100
@@ -46,9 +46,6 @@
  */
 #define MIN_IOS 256
 
-static struct workqueue_struct *ksnapd;
-static void flush_queued_bios(struct work_struct *work);
-
 struct dm_snap_pending_exception {
 	struct dm_snap_exception e;
 
@@ -610,7 +607,6 @@ static int snapshot_ctr(struct dm_target
 	s->active = 0;
 	atomic_set(&s->pending_exceptions_count, 0);
 	init_rwsem(&s->lock);
-	spin_lock_init(&s->pe_lock);
 	s->ti = ti;
 
 	/* Allocate hash table for COW data */
@@ -668,9 +664,6 @@ static int snapshot_ctr(struct dm_target
 		DMWARN("Snapshot is marked invalid.");
 	}
 
-	bio_list_init(&s->queued_bios);
-	INIT_WORK(&s->queued_bios_work, flush_queued_bios);
-
 	/* Add snapshot to the list of snapshots for this origin */
 	/* Exceptions aren't triggered till snapshot_resume() is called */
 	if (register_snapshot(s)) {
@@ -729,8 +722,6 @@ static void snapshot_dtr(struct dm_targe
 #endif
 	struct dm_snapshot *s = ti->private;
 
-	flush_workqueue(ksnapd);
-
 	/* Prevent further origin writes from using this snapshot. */
 	/* After this returns there can be no new kcopyd jobs. */
 	unregister_snapshot(s);
@@ -775,20 +766,6 @@ static void flush_bios(struct bio *bio)
 	}
 }
 
-static void flush_queued_bios(struct work_struct *work)
-{
-	struct dm_snapshot *s =
-		container_of(work, struct dm_snapshot, queued_bios_work);
-	struct bio *queued_bios;
-	unsigned long flags;
-
-	spin_lock_irqsave(&s->pe_lock, flags);
-	queued_bios = bio_list_get(&s->queued_bios);
-	spin_unlock_irqrestore(&s->pe_lock, flags);
-
-	flush_bios(queued_bios);
-}
-
 /*
  * Error a list of buffers.
  */
@@ -1444,17 +1421,8 @@ static int __init dm_snapshot_init(void)
 		goto bad5;
 	}
 
-	ksnapd = create_singlethread_workqueue("ksnapd");
-	if (!ksnapd) {
-		DMERR("Failed to create ksnapd workqueue.");
-		r = -ENOMEM;
-		goto bad_pending_pool;
-	}
-
 	return 0;
 
-      bad_pending_pool:
-	kmem_cache_destroy(tracked_chunk_cache);
       bad5:
 	kmem_cache_destroy(pending_cache);
       bad4:
@@ -1470,8 +1438,6 @@ static int __init dm_snapshot_init(void)
 
 static void __exit dm_snapshot_exit(void)
 {
-	destroy_workqueue(ksnapd);
-
 	dm_unregister_target(&snapshot_target);
 	dm_unregister_target(&origin_target);
 
Index: linux-2.6.28-rc5-devel/drivers/md/dm-snap.h
===================================================================
--- linux-2.6.28-rc5-devel.orig/drivers/md/dm-snap.h	2008-11-25 15:08:51.000000000 +0100
+++ linux-2.6.28-rc5-devel/drivers/md/dm-snap.h	2008-11-25 16:10:10.000000000 +0100
@@ -165,21 +165,11 @@ struct dm_snapshot {
 	struct exception_table pending;
 	struct exception_table complete;
 
-	/*
-	 * pe_lock protects all pending_exception operations and access
-	 * as well as the snapshot_bios list.
-	 */
-	spinlock_t pe_lock;
-
 	/* The on disk metadata handler */
 	struct exception_store store;
 
 	struct dm_kcopyd_client *kcopyd_client;
 
-	/* Queue of snapshot writes for ksnapd to flush */
-	struct bio_list queued_bios;
-	struct work_struct queued_bios_work;
-
 	/* Chunks with outstanding reads */
 	mempool_t *tracked_chunk_pool;
 	spinlock_t tracked_chunk_lock;