virtio-ring: factor out desc_extra allocation

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@redhat.com>
Link: https://lore.kernel.org/r/20210604055350.58753-4-jasowang@redhat.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 03caa19..f2f4a3b 100644 (file)
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -1556,6 +1556,25 @@ 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,
@@ -1573,7 +1592,6 @@ 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);
 
@@ -1657,18 +1675,10 @@ 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;