static int gntdev_mmap()

in gntdev.c [968:1071]

• 79 lines of code
• 20 McCabe index (conditional complexity)

static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)
{
	struct gntdev_priv *priv = flip->private_data;
	int index = vma->vm_pgoff;
	int count = vma_pages(vma);
	struct gntdev_grant_map *map;
	int err = -EINVAL;

	if ((vma->vm_flags & VM_WRITE) && !(vma->vm_flags & VM_SHARED))
		return -EINVAL;

	pr_debug("map %d+%d at %lx (pgoff %lx)\n",
			index, count, vma->vm_start, vma->vm_pgoff);

	mutex_lock(&priv->lock);
	map = gntdev_find_map_index(priv, index, count);
	if (!map)
		goto unlock_out;
	if (use_ptemod && map->vma)
		goto unlock_out;
	refcount_inc(&map->users);

	vma->vm_ops = &gntdev_vmops;

	vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP | VM_MIXEDMAP;

	if (use_ptemod)
		vma->vm_flags |= VM_DONTCOPY;

	vma->vm_private_data = map;
	if (map->flags) {
		if ((vma->vm_flags & VM_WRITE) &&
				(map->flags & GNTMAP_readonly))
			goto out_unlock_put;
	} else {
		map->flags = GNTMAP_host_map;
		if (!(vma->vm_flags & VM_WRITE))
			map->flags |= GNTMAP_readonly;
	}

	if (use_ptemod) {
		map->vma = vma;
		err = mmu_interval_notifier_insert_locked(
			&map->notifier, vma->vm_mm, vma->vm_start,
			vma->vm_end - vma->vm_start, &gntdev_mmu_ops);
		if (err) {
			map->vma = NULL;
			goto out_unlock_put;
		}
	}
	mutex_unlock(&priv->lock);

	if (use_ptemod) {
		/*
		 * gntdev takes the address of the PTE in find_grant_ptes() and
		 * passes it to the hypervisor in gntdev_map_grant_pages(). The
		 * purpose of the notifier is to prevent the hypervisor pointer
		 * to the PTE from going stale.
		 *
		 * Since this vma's mappings can't be touched without the
		 * mmap_lock, and we are holding it now, there is no need for
		 * the notifier_range locking pattern.
		 */
		mmu_interval_read_begin(&map->notifier);

		map->pages_vm_start = vma->vm_start;
		err = apply_to_page_range(vma->vm_mm, vma->vm_start,
					  vma->vm_end - vma->vm_start,
					  find_grant_ptes, map);
		if (err) {
			pr_warn("find_grant_ptes() failure.\n");
			goto out_put_map;
		}
	}

	err = gntdev_map_grant_pages(map);
	if (err)
		goto out_put_map;

	if (!use_ptemod) {
		err = vm_map_pages_zero(vma, map->pages, map->count);
		if (err)
			goto out_put_map;
	}

	return 0;

unlock_out:
	mutex_unlock(&priv->lock);
	return err;

out_unlock_put:
	mutex_unlock(&priv->lock);
out_put_map:
	if (use_ptemod) {
		unmap_grant_pages(map, 0, map->count);
		if (map->vma) {
			mmu_interval_notifier_remove(&map->notifier);
			map->vma = NULL;
		}
	}
	gntdev_put_map(priv, map);
	return err;
}