static int backend_map()

in xen-front-pgdir-shbuf.c [256:330]

• 59 lines of code
• 10 McCabe index (conditional complexity)

static int backend_map(struct xen_front_pgdir_shbuf *buf)
{
	struct gnttab_map_grant_ref *map_ops = NULL;
	unsigned char *ptr;
	int ret, cur_gref, cur_dir_page, cur_page, grefs_left;

	map_ops = kcalloc(buf->num_pages, sizeof(*map_ops), GFP_KERNEL);
	if (!map_ops)
		return -ENOMEM;

	buf->backend_map_handles = kcalloc(buf->num_pages,
					   sizeof(*buf->backend_map_handles),
					   GFP_KERNEL);
	if (!buf->backend_map_handles) {
		kfree(map_ops);
		return -ENOMEM;
	}

	/*
	 * Read page directory to get grefs from the backend: for external
	 * buffer we only allocate buf->grefs for the page directory,
	 * so buf->num_grefs has number of pages in the page directory itself.
	 */
	ptr = buf->directory;
	grefs_left = buf->num_pages;
	cur_page = 0;
	for (cur_dir_page = 0; cur_dir_page < buf->num_grefs; cur_dir_page++) {
		struct xen_page_directory *page_dir =
			(struct xen_page_directory *)ptr;
		int to_copy = XEN_NUM_GREFS_PER_PAGE;

		if (to_copy > grefs_left)
			to_copy = grefs_left;

		for (cur_gref = 0; cur_gref < to_copy; cur_gref++) {
			phys_addr_t addr;

			addr = xen_page_to_vaddr(buf->pages[cur_page]);
			gnttab_set_map_op(&map_ops[cur_page], addr,
					  GNTMAP_host_map,
					  page_dir->gref[cur_gref],
					  buf->xb_dev->otherend_id);
			cur_page++;
		}

		grefs_left -= to_copy;
		ptr += PAGE_SIZE;
	}
	ret = gnttab_map_refs(map_ops, NULL, buf->pages, buf->num_pages);

	/* Save handles even if error, so we can unmap. */
	for (cur_page = 0; cur_page < buf->num_pages; cur_page++) {
		if (likely(map_ops[cur_page].status == GNTST_okay)) {
			buf->backend_map_handles[cur_page] =
				map_ops[cur_page].handle;
		} else {
			buf->backend_map_handles[cur_page] =
				INVALID_GRANT_HANDLE;
			if (!ret)
				ret = -ENXIO;
			dev_err(&buf->xb_dev->dev,
				"Failed to map page %d: %d\n",
				cur_page, map_ops[cur_page].status);
		}
	}

	if (ret) {
		dev_err(&buf->xb_dev->dev,
			"Failed to map grant references, ret %d", ret);
		backend_unmap(buf);
	}

	kfree(map_ops);
	return ret;
}