static inline int __vringh_get_head()

in vringh.c [38:76]

• 31 lines of code
• 5 McCabe index (conditional complexity)

static inline int __vringh_get_head(const struct vringh *vrh,
				    int (*getu16)(const struct vringh *vrh,
						  u16 *val, const __virtio16 *p),
				    u16 *last_avail_idx)
{
	u16 avail_idx, i, head;
	int err;

	err = getu16(vrh, &avail_idx, &vrh->vring.avail->idx);
	if (err) {
		vringh_bad("Failed to access avail idx at %p",
			   &vrh->vring.avail->idx);
		return err;
	}

	if (*last_avail_idx == avail_idx)
		return vrh->vring.num;

	/* Only get avail ring entries after they have been exposed by guest. */
	virtio_rmb(vrh->weak_barriers);

	i = *last_avail_idx & (vrh->vring.num - 1);

	err = getu16(vrh, &head, &vrh->vring.avail->ring[i]);
	if (err) {
		vringh_bad("Failed to read head: idx %d address %p",
			   *last_avail_idx, &vrh->vring.avail->ring[i]);
		return err;
	}

	if (head >= vrh->vring.num) {
		vringh_bad("Guest says index %u > %u is available",
			   head, vrh->vring.num);
		return -EINVAL;
	}

	(*last_avail_idx)++;
	return head;
}