dm-buffered: rework spinlocks

Change spin_lock_irq to spin_lock because we don't lock the spinlock in an
irq.

Grab the spinlock when calling bio_list_empty.

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

---
 drivers/md/dm-buffered-target.c |   17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

Index: linux-2.6/drivers/md/dm-buffered-target.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-buffered-target.c
+++ linux-2.6/drivers/md/dm-buffered-target.c
@@ -271,12 +271,12 @@ static void _process_bio(struct work_str
 {
 	struct buffered_c *bc = container_of(work, struct buffered_c, buffered_ws);
 	struct bio *bio;
-	bool write;
+	bool write, queue;
 	sector_t blocks, start, end;
 
-	spin_lock_irq(&bc->lock);
+	spin_lock(&bc->lock);
 	bio = bio_list_pop(&bc->bios);
-	spin_unlock_irq(&bc->lock);
+	spin_unlock(&bc->lock);
 
 	if (!bio)
 		return;
@@ -309,11 +309,16 @@ static void _process_bio(struct work_str
 		write = true;
 		break;
 	default:
+		break;
 	}
 
 	__process_bio(bc, bio);
 
-	if (!bio_list_empty(&bc->bios))
+	spin_lock(&bc->lock);
+	queue = !bio_list_empty(&bc->bios);
+	spin_unlock(&bc->lock);
+
+	if (queue)
 		queue_work(bc->buffered_wq, &bc->buffered_ws);
 
 	/* Reschedule the flush thread in case of new write(s) */
@@ -479,10 +484,10 @@ static int buffered_map(struct dm_target
 
 	bio->bi_iter.bi_sector = dm_target_offset(ti, bio->bi_iter.bi_sector);
 
-	spin_lock_irq(&bc->lock);
+	spin_lock(&bc->lock);
 	queue = bio_list_empty(&bc->bios);
 	bio_list_add(&bc->bios, bio);
-	spin_unlock_irq(&bc->lock);
+	spin_unlock(&bc->lock);
 
 	if (queue)
 		queue_work(bc->buffered_wq, &bc->buffered_ws);