static int gntdev_grant_copy_seg()

in gntdev.c [793:886]

• 72 lines of code
• 14 McCabe index (conditional complexity)

static int gntdev_grant_copy_seg(struct gntdev_copy_batch *batch,
				 struct gntdev_grant_copy_segment *seg,
				 s16 __user *status)
{
	uint16_t copied = 0;

	/*
	 * Disallow local -> local copies since there is only space in
	 * batch->pages for one page per-op and this would be a very
	 * expensive memcpy().
	 */
	if (!(seg->flags & (GNTCOPY_source_gref | GNTCOPY_dest_gref)))
		return -EINVAL;

	/* Can't cross page if source/dest is a grant ref. */
	if (seg->flags & GNTCOPY_source_gref) {
		if (seg->source.foreign.offset + seg->len > XEN_PAGE_SIZE)
			return -EINVAL;
	}
	if (seg->flags & GNTCOPY_dest_gref) {
		if (seg->dest.foreign.offset + seg->len > XEN_PAGE_SIZE)
			return -EINVAL;
	}

	if (put_user(GNTST_okay, status))
		return -EFAULT;

	while (copied < seg->len) {
		struct gnttab_copy *op;
		void __user *virt;
		size_t len, off;
		unsigned long gfn;
		int ret;

		if (batch->nr_ops >= GNTDEV_COPY_BATCH) {
			ret = gntdev_copy(batch);
			if (ret < 0)
				return ret;
		}

		len = seg->len - copied;

		op = &batch->ops[batch->nr_ops];
		op->flags = 0;

		if (seg->flags & GNTCOPY_source_gref) {
			op->source.u.ref = seg->source.foreign.ref;
			op->source.domid = seg->source.foreign.domid;
			op->source.offset = seg->source.foreign.offset + copied;
			op->flags |= GNTCOPY_source_gref;
		} else {
			virt = seg->source.virt + copied;
			off = (unsigned long)virt & ~XEN_PAGE_MASK;
			len = min(len, (size_t)XEN_PAGE_SIZE - off);
			batch->writeable = false;

			ret = gntdev_get_page(batch, virt, &gfn);
			if (ret < 0)
				return ret;

			op->source.u.gmfn = gfn;
			op->source.domid = DOMID_SELF;
			op->source.offset = off;
		}

		if (seg->flags & GNTCOPY_dest_gref) {
			op->dest.u.ref = seg->dest.foreign.ref;
			op->dest.domid = seg->dest.foreign.domid;
			op->dest.offset = seg->dest.foreign.offset + copied;
			op->flags |= GNTCOPY_dest_gref;
		} else {
			virt = seg->dest.virt + copied;
			off = (unsigned long)virt & ~XEN_PAGE_MASK;
			len = min(len, (size_t)XEN_PAGE_SIZE - off);
			batch->writeable = true;

			ret = gntdev_get_page(batch, virt, &gfn);
			if (ret < 0)
				return ret;

			op->dest.u.gmfn = gfn;
			op->dest.domid = DOMID_SELF;
			op->dest.offset = off;
		}

		op->len = len;
		copied += len;

		batch->status[batch->nr_ops] = status;
		batch->nr_ops++;
	}

	return 0;
}