[RFC PATCH 3/7] virtio-ring: factor out desc_extra allocation

[Jason Wang <jasowang@xxxxxxxxxx>]

A helper is introduced for the logic of allocating the descriptor
extra data. This will be reused by split virtqueue.

Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
---
 drivers/virtio/virtio_ring.c | 30 ++++++++++++++++++++----------
 1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index c25ea5776687..0cdd965dba58 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -1550,6 +1550,25 @@ static void *virtqueue_detach_unused_buf_packed(struct virtqueue *_vq)
 	return NULL;
 }
 
+static struct vring_desc_extra *vring_alloc_desc_extra(struct vring_virtqueue *vq,
+						       unsigned int num)
+{
+	struct vring_desc_extra *desc_extra;
+	unsigned int i;
+
+	desc_extra = kmalloc_array(num, sizeof(struct vring_desc_extra),
+				   GFP_KERNEL);
+	if (!desc_extra)
+		return NULL;
+
+	memset(desc_extra, 0, num * sizeof(struct vring_desc_extra));
+
+	for (i = 0; i < num - 1; i++)
+		desc_extra[i].next = i + 1;
+
+	return desc_extra;
+}
+
 static struct virtqueue *vring_create_virtqueue_packed(
 	unsigned int index,
 	unsigned int num,
@@ -1567,7 +1586,6 @@ static struct virtqueue *vring_create_virtqueue_packed(
 	struct vring_packed_desc_event *driver, *device;
 	dma_addr_t ring_dma_addr, driver_event_dma_addr, device_event_dma_addr;
 	size_t ring_size_in_bytes, event_size_in_bytes;
-	unsigned int i;
 
 	ring_size_in_bytes = num * sizeof(struct vring_packed_desc);
 
@@ -1650,18 +1668,10 @@ static struct virtqueue *vring_create_virtqueue_packed(
 	/* Put everything in free lists. */
 	vq->free_head = 0;
 
-	vq->packed.desc_extra = kmalloc_array(num,
-			sizeof(struct vring_desc_extra),
-			GFP_KERNEL);
+	vq->packed.desc_extra = vring_alloc_desc_extra(vq, num);
 	if (!vq->packed.desc_extra)
 		goto err_desc_extra;
 
-	memset(vq->packed.desc_extra, 0,
-		num * sizeof(struct vring_desc_extra));
-
-	for (i = 0; i < num - 1; i++)
-		vq->packed.desc_extra[i].next = i + 1;
-
 	/* No callback?  Tell other side not to bother us. */
 	if (!callback) {
 		vq->packed.event_flags_shadow = VRING_PACKED_EVENT_FLAG_DISABLE;
-- 
2.25.1