Btrfs: Catch missed bios in the async bio submission thread

The async bio submission thread was missing some bios that were
added after it had decided there was no work left to do.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/async-thread.c

@@ -349,6 +349,7 @@ int btrfs_requeue_work(struct btrfs_work *work)
 {
 	struct btrfs_worker_thread *worker = work->worker;
 	unsigned long flags;
+	int wake = 0;
 
 	if (test_and_set_bit(WORK_QUEUED_BIT, &work->flags))
 		goto out;
@@ -367,10 +368,16 @@ int btrfs_requeue_work(struct btrfs_work *work)
 			       &worker->workers->worker_list);
 		spin_unlock_irqrestore(&worker->workers->lock, flags);
 	}
+	if (!worker->working) {
+		wake = 1;
+		worker->working = 1;
+	}
 
 	spin_unlock_irqrestore(&worker->lock, flags);
-
+	if (wake)
+		wake_up_process(worker->task);
 out:
+
 	return 0;
 }
 
@@ -397,6 +404,7 @@ int btrfs_queue_worker(struct btrfs_workers *workers, struct btrfs_work *work)
 	}
 
 	spin_lock_irqsave(&worker->lock, flags);
+
 	atomic_inc(&worker->num_pending);
 	check_busy_worker(worker);
 	list_add_tail(&work->list, &worker->pending);

fs/btrfs/volumes.c

@@ -154,6 +154,7 @@ static noinline int run_scheduled_bios(struct btrfs_device *device)
 loop:
 	spin_lock(&device->io_lock);
 
+loop_lock:
 	/* take all the bios off the list at once and process them
 	 * later on (without the lock held).  But, remember the
 	 * tail and other pointers so the bios can be properly reinserted
@@ -203,7 +204,7 @@ static noinline int run_scheduled_bios(struct btrfs_device *device)
 		 * is now congested.  Back off and let other work structs
 		 * run instead
 		 */
-		if (pending && bdi_write_congested(bdi) &&
+		if (pending && bdi_write_congested(bdi) && num_run > 16 &&
 		    fs_info->fs_devices->open_devices > 1) {
 			struct bio *old_head;
 
@@ -215,7 +216,8 @@ static noinline int run_scheduled_bios(struct btrfs_device *device)
 				tail->bi_next = old_head;
 			else
 				device->pending_bio_tail = tail;
-			device->running_pending = 0;
+
+			device->running_pending = 1;
 
 			spin_unlock(&device->io_lock);
 			btrfs_requeue_work(&device->work);
@@ -224,6 +226,11 @@ static noinline int run_scheduled_bios(struct btrfs_device *device)
 	}
 	if (again)
 		goto loop;
+
+	spin_lock(&device->io_lock);
+	if (device->pending_bios)
+		goto loop_lock;
+	spin_unlock(&device->io_lock);
 done:
 	return 0;
 }