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>

diff --git a/drivers/vdpa/vdpa_user/iova_domain.c b/drivers/vdpa/vdpa_user/iova_domain.c
index 6daa397..bca1f0b 100644 (file)
--- a/drivers/vdpa/vdpa_user/iova_domain.c
+++ b/drivers/vdpa/vdpa_user/iova_domain.c
@@ -211,17 +211,14 @@ static struct page *
 vduse_domain_get_bounce_page(struct vduse_iova_domain *domain, u64 iova)
 {
        struct vduse_bounce_map *map;
-       struct page *page = NULL;
+       struct page *page;
 
-       spin_lock(&domain->iotlb_lock);
        map = &domain->bounce_maps[iova >> PAGE_SHIFT];
        if (!map->bounce_page)
-               goto out;
+               return NULL;
 
        page = map->bounce_page;
        get_page(page);
-out:
-       spin_unlock(&domain->iotlb_lock);
 
        return page;
 }