static int virtqueue_add_indirect_packed()

in virtio_ring.c [1052:1164]

• 85 lines of code
• 12 McCabe index (conditional complexity)

static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
					 struct scatterlist *sgs[],
					 unsigned int total_sg,
					 unsigned int out_sgs,
					 unsigned int in_sgs,
					 void *data,
					 gfp_t gfp)
{
	struct vring_packed_desc *desc;
	struct scatterlist *sg;
	unsigned int i, n, err_idx;
	u16 head, id;
	dma_addr_t addr;

	head = vq->packed.next_avail_idx;
	desc = alloc_indirect_packed(total_sg, gfp);
	if (!desc)
		return -ENOMEM;

	if (unlikely(vq->vq.num_free < 1)) {
		pr_debug("Can't add buf len 1 - avail = 0\n");
		kfree(desc);
		END_USE(vq);
		return -ENOSPC;
	}

	i = 0;
	id = vq->free_head;
	BUG_ON(id == vq->packed.vring.num);

	for (n = 0; n < out_sgs + in_sgs; n++) {
		for (sg = sgs[n]; sg; sg = sg_next(sg)) {
			addr = vring_map_one_sg(vq, sg, n < out_sgs ?
					DMA_TO_DEVICE : DMA_FROM_DEVICE);
			if (vring_mapping_error(vq, addr))
				goto unmap_release;

			desc[i].flags = cpu_to_le16(n < out_sgs ?
						0 : VRING_DESC_F_WRITE);
			desc[i].addr = cpu_to_le64(addr);
			desc[i].len = cpu_to_le32(sg->length);
			i++;
		}
	}

	/* Now that the indirect table is filled in, map it. */
	addr = vring_map_single(vq, desc,
			total_sg * sizeof(struct vring_packed_desc),
			DMA_TO_DEVICE);
	if (vring_mapping_error(vq, addr))
		goto unmap_release;

	vq->packed.vring.desc[head].addr = cpu_to_le64(addr);
	vq->packed.vring.desc[head].len = cpu_to_le32(total_sg *
				sizeof(struct vring_packed_desc));
	vq->packed.vring.desc[head].id = cpu_to_le16(id);

	if (vq->use_dma_api) {
		vq->packed.desc_extra[id].addr = addr;
		vq->packed.desc_extra[id].len = total_sg *
				sizeof(struct vring_packed_desc);
		vq->packed.desc_extra[id].flags = VRING_DESC_F_INDIRECT |
						  vq->packed.avail_used_flags;
	}

	/*
	 * A driver MUST NOT make the first descriptor in the list
	 * available before all subsequent descriptors comprising
	 * the list are made available.
	 */
	virtio_wmb(vq->weak_barriers);
	vq->packed.vring.desc[head].flags = cpu_to_le16(VRING_DESC_F_INDIRECT |
						vq->packed.avail_used_flags);

	/* We're using some buffers from the free list. */
	vq->vq.num_free -= 1;

	/* Update free pointer */
	n = head + 1;
	if (n >= vq->packed.vring.num) {
		n = 0;
		vq->packed.avail_wrap_counter ^= 1;
		vq->packed.avail_used_flags ^=
				1 << VRING_PACKED_DESC_F_AVAIL |
				1 << VRING_PACKED_DESC_F_USED;
	}
	vq->packed.next_avail_idx = n;
	vq->free_head = vq->packed.desc_extra[id].next;

	/* Store token and indirect buffer state. */
	vq->packed.desc_state[id].num = 1;
	vq->packed.desc_state[id].data = data;
	vq->packed.desc_state[id].indir_desc = desc;
	vq->packed.desc_state[id].last = id;

	vq->num_added += 1;

	pr_debug("Added buffer head %i to %p\n", head, vq);
	END_USE(vq);

	return 0;

unmap_release:
	err_idx = i;

	for (i = 0; i < err_idx; i++)
		vring_unmap_desc_packed(vq, &desc[i]);

	kfree(desc);

	END_USE(vq);
	return -ENOMEM;
}