Unify spinlock

Remove "crypt_thread_spinlock" and use wait queue spinlock
"crypt_thread_wait.spinlock" instead.

This saves few atomic operations in the encryption thread.

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

---
 drivers/md/dm-crypt.c |   23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

Index: linux-3.2-fast/drivers/md/dm-crypt.c
===================================================================
--- linux-3.2-fast.orig/drivers/md/dm-crypt.c	2012-01-31 02:29:58.000000000 +0100
+++ linux-3.2-fast/drivers/md/dm-crypt.c	2012-01-31 02:30:30.000000000 +0100
@@ -130,7 +130,6 @@ struct crypt_config {
 	struct task_struct **crypt_threads;
 
 	wait_queue_head_t crypt_thread_wait;
-	spinlock_t crypt_thread_spinlock;
 	struct list_head crypt_thread_list;
 
 	char *cipher;
@@ -681,15 +680,16 @@ static int dmcrypt_thread(void *data)
 
 		DECLARE_WAITQUEUE(wait, current);
 
-		spin_lock(&cc->crypt_thread_spinlock);
+		spin_lock_irq(&cc->crypt_thread_wait.lock);
+continue_locked:
 
 		if (!list_empty(&cc->crypt_thread_list))
 			goto pop_from_list;
 
 		__set_current_state(TASK_INTERRUPTIBLE);
-		add_wait_queue(&cc->crypt_thread_wait, &wait);
+		__add_wait_queue(&cc->crypt_thread_wait, &wait);
 
-		spin_unlock(&cc->crypt_thread_spinlock);
+		spin_unlock_irq(&cc->crypt_thread_wait.lock);
 
 		if (unlikely(kthread_should_stop())) {
 			set_task_state(current, TASK_RUNNING);
@@ -700,8 +700,9 @@ static int dmcrypt_thread(void *data)
 		schedule();
 
 		set_task_state(current, TASK_RUNNING);
-		remove_wait_queue(&cc->crypt_thread_wait, &wait);
-		continue;
+		spin_lock_irq(&cc->crypt_thread_wait.lock);
+		__remove_wait_queue(&cc->crypt_thread_wait, &wait);
+		goto continue_locked;
 
 pop_from_list:
 		n_dmreqs = 0;
@@ -713,7 +714,8 @@ pop_from_list:
 			dmreqs[n_dmreqs++] = dmreq;
 		} while (n_dmreqs < DMREQ_PULL_BATCH &&
 			 !list_empty(&cc->crypt_thread_list));
-		spin_unlock(&cc->crypt_thread_spinlock);
+
+		spin_unlock_irq(&cc->crypt_thread_wait.lock);
 
 		i = 0;
 		do {
@@ -806,10 +808,10 @@ static struct ablkcipher_request *crypt_
 
 static void crypt_flush_batch(struct crypt_config *cc, struct list_head *batch)
 {
-	spin_lock(&cc->crypt_thread_spinlock);
+	spin_lock_irq(&cc->crypt_thread_wait.lock);
 	list_splice_tail(batch, &cc->crypt_thread_list);
-	spin_unlock(&cc->crypt_thread_spinlock);
-	wake_up_all(&cc->crypt_thread_wait);
+	wake_up_locked(&cc->crypt_thread_wait);
+	spin_unlock_irq(&cc->crypt_thread_wait.lock);
 	INIT_LIST_HEAD(batch);
 
 }
@@ -1754,7 +1756,6 @@ static int crypt_ctr(struct dm_target *t
 			cc->crypt_threads_size = i + 1;
 
 	init_waitqueue_head(&cc->crypt_thread_wait);
-	spin_lock_init(&cc->crypt_thread_spinlock);
 	INIT_LIST_HEAD(&cc->crypt_thread_list);
 
 	cc->crypt_threads = kzalloc(cc->crypt_threads_size *