Commit c32ee693 authored Aug 03, 2022 by Xie Yongji Committed by Michael S. Tsirkin Aug 11, 2022

vduse: Remove unnecessary spin lock protection



Now we use domain->iotlb_lock to protect two different
variables: domain->bounce_maps->bounce_page and
domain->iotlb. But for domain->bounce_maps->bounce_page,
we actually don't need any synchronization between
vduse_domain_get_bounce_page() and vduse_domain_free_bounce_pages()
since vduse_domain_get_bounce_page() will only be called in
page fault handler and vduse_domain_free_bounce_pages() will
be called during file release.

So let's remove the unnecessary spin lock protection in
vduse_domain_get_bounce_page(). Then the usage of
domain->iotlb_lock could be more clear: the lock will be
only used to protect the domain->iotlb.

Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20220803045523.23851-2-xieyongji@bytedance.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

parent 699b045a

drivers/vdpa/vdpa_user/iova_domain.c

+2 −5

Original line number	Original line	Diff line number	Diff line
	@@ -211,17 +211,14 @@ static struct page *
	vduse_domain_get_bounce_page(struct vduse_iova_domain *domain, u64 iova)		vduse_domain_get_bounce_page(struct vduse_iova_domain *domain, u64 iova)
	{		{
	struct vduse_bounce_map *map;		struct vduse_bounce_map *map;
	struct page *page = NULL;		struct page *page;

	spin_lock(&domain->iotlb_lock);
	map = &domain->bounce_maps[iova >> PAGE_SHIFT];		map = &domain->bounce_maps[iova >> PAGE_SHIFT];
	if (!map->bounce_page)		if (!map->bounce_page)
	goto out;		return NULL;

	page = map->bounce_page;		page = map->bounce_page;
	get_page(page);		get_page(page);
	out:
	spin_unlock(&domain->iotlb_lock);

	return page;		return page;
	}		}