virtio_blk: remove virtblk_update_cache_mode

virtblk_update_cache_mode boils down to a single call to
blk_queue_write_cache.  Remove it in preparation for moving the cache
control flags into the queue_limits.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20240617060532.127975-10-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/virtio_blk.c

@@ -1089,14 +1089,6 @@ static int virtblk_get_cache_mode(struct virtio_device *vdev)
 	return writeback;
 }
 
-static void virtblk_update_cache_mode(struct virtio_device *vdev)
-{
-	u8 writeback = virtblk_get_cache_mode(vdev);
-	struct virtio_blk *vblk = vdev->priv;
-
-	blk_queue_write_cache(vblk->disk->queue, writeback, false);
-}
-
 static const char *const virtblk_cache_types[] = {
 	"write through", "write back"
 };
@@ -1116,7 +1108,7 @@ cache_type_store(struct device *dev, struct device_attribute *attr,
 		return i;
 
 	virtio_cwrite8(vdev, offsetof(struct virtio_blk_config, wce), i);
-	virtblk_update_cache_mode(vdev);
+	blk_queue_write_cache(disk->queue, virtblk_get_cache_mode(vdev), false);
 	return count;
 }
 
@@ -1528,7 +1520,8 @@ static int virtblk_probe(struct virtio_device *vdev)
 	vblk->index = index;
 
 	/* configure queue flush support */
-	virtblk_update_cache_mode(vdev);
+	blk_queue_write_cache(vblk->disk->queue, virtblk_get_cache_mode(vdev),
+			false);
 
 	/* If disk is read-only in the host, the guest should obey */
 	if (virtio_has_feature(vdev, VIRTIO_BLK_F_RO))