Btrfs: change wait_dev_flush() return type to bool

The flush error code is maintained in btrfs_device::last_flush_error, so
there is no point in returning it in wait_dev_flush() when it is not being
used. Instead, we can return a boolean value.

Note that even though btrfs_device::last_flush_error may not be used, we
will keep it for now.

Signed-off-by: Anand Jain <anand.jain@oracle.com>

fs/btrfs/disk-io.c

@@ -4110,23 +4110,25 @@ static void write_dev_flush(struct btrfs_device *device)
 
 /*
  * If the flush bio has been submitted by write_dev_flush, wait for it.
+ * Return false for any error, and true otherwise.
  */
-static blk_status_t wait_dev_flush(struct btrfs_device *device)
+static bool wait_dev_flush(struct btrfs_device *device)
 {
 	struct bio *bio = &device->flush_bio;
 
 	if (!test_bit(BTRFS_DEV_STATE_FLUSH_SENT, &device->dev_state))
-		return BLK_STS_OK;
+		return true;
 
 	clear_bit(BTRFS_DEV_STATE_FLUSH_SENT, &device->dev_state);
 	wait_for_completion_io(&device->flush_wait);
 
 	if (bio->bi_status) {
 		device->last_flush_error = bio->bi_status;
 		btrfs_dev_stat_inc_and_print(device, BTRFS_DEV_STAT_FLUSH_ERRS);
+		return false;
 	}
 
-	return bio->bi_status;
+	return true;
 }
 
 /*