On 9/5/23 10:20, Boris Brezillon wrote: > On Sun, 3 Sep 2023 20:07:22 +0300 > Dmitry Osipenko <dmitry.osipe...@collabora.com> wrote: > >> Prepare virtio_gpu_object_create() to addition of memory shrinker support >> by replacing open-coded drm_gem_shmem_free() with drm_gem_object_put() that >> decrements GEM refcount to 0, which becomes important for drm-shmem because >> it will start to use GEM's refcount during the shmem's BO freeing time in >> order to prevent spurious lockdep warning about resv lock ordering vs >> fs_reclaim code paths. > > I think I'm okay with the change (assuming virtio_gpu_free_object() > can deal with partially initialized objects), not with the explanation > :-). I don't really see why we need to take the resv lock in > drm_gem_shmem_free(). As said in my v15 review, I think we should > replace the drm_gem_shmem_put_pages() call we have in > drm_gem_shmem_free() by a call to a new drm_gem_shmem_free_pages() > helper that does exactly what drm_gem_shmem_put_pages() does without > the refcounting/locking, because all that should remain at the time > drm_gem_shmem_free() is called is the implicit pages ref owned by > shmem->sgt, and there's no risk of other threads accessing the GEM > object at that point.
Apparently I forgot to drop these drm_gem_object_put() patches by accident in v16, the drm_gem_shmem_free() doesn't touch resv lock anymore. Will re-check for v17. -- Best regards, Dmitry
