Prepare drm_gem_shmem_free() to addition of memory shrinker support to drm-shmem by adding and using variant of put_pages() that doesn't touch reservation lock. Reservation shouldn't be touched because lockdep will trigger a bogus warning about locking contention with fs_reclaim code paths that can't happen during the time when GEM is freed and lockdep doesn't know about that.
Signed-off-by: Dmitry Osipenko <[email protected]> --- drivers/gpu/drm/drm_gem_shmem_helper.c | 55 +++++++++++++++++--------- 1 file changed, 37 insertions(+), 18 deletions(-) diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c index 8a8eab4d0332..4959f51b647a 100644 --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -128,6 +128,41 @@ struct drm_gem_shmem_object *drm_gem_shmem_create(struct drm_device *dev, size_t } EXPORT_SYMBOL_GPL(drm_gem_shmem_create); +static void +__drm_gem_shmem_release_pages(struct drm_gem_shmem_object *shmem) +{ + struct drm_gem_object *obj = &shmem->base; + +#ifdef CONFIG_X86 + if (shmem->map_wc) + set_pages_array_wb(shmem->pages, obj->size >> PAGE_SHIFT); +#endif + + drm_gem_put_pages(obj, shmem->pages, + shmem->pages_mark_dirty_on_put, + shmem->pages_mark_accessed_on_put); + shmem->pages = NULL; +} + +static void +__drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem) +{ + /* + * Destroying the object is a special case. Acquiring the obj + * lock in drm_gem_shmem_put_pages_locked() can cause a locking + * order inversion between reservation_ww_class_mutex and fs_reclaim + * when called from drm_gem_shmem_free(). + * + * This deadlock is not actually possible, because no one should + * be already holding the lock when drm_gem_shmem_free() is called. + * Unfortunately lockdep is not aware of this detail. So when the + * refcount drops to zero, make sure that the reservation lock + * isn't touched here. + */ + if (refcount_dec_and_test(&shmem->pages_use_count)) + __drm_gem_shmem_release_pages(shmem); +} + /** * drm_gem_shmem_free - Free resources associated with a shmem GEM object * @shmem: shmem GEM object to free @@ -142,8 +177,6 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem) if (obj->import_attach) { drm_prime_gem_destroy(obj, shmem->sgt); } else { - dma_resv_lock(shmem->base.resv, NULL); - drm_WARN_ON(obj->dev, refcount_read(&shmem->vmap_use_count)); if (shmem->sgt) { @@ -153,11 +186,9 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem) kfree(shmem->sgt); } if (shmem->pages) - drm_gem_shmem_put_pages_locked(shmem); + __drm_gem_shmem_put_pages(shmem); drm_WARN_ON(obj->dev, refcount_read(&shmem->pages_use_count)); - - dma_resv_unlock(shmem->base.resv); } drm_gem_object_release(obj); @@ -207,21 +238,9 @@ static int drm_gem_shmem_get_pages_locked(struct drm_gem_shmem_object *shmem) */ void drm_gem_shmem_put_pages_locked(struct drm_gem_shmem_object *shmem) { - struct drm_gem_object *obj = &shmem->base; - dma_resv_assert_held(shmem->base.resv); - if (refcount_dec_and_test(&shmem->pages_use_count)) { -#ifdef CONFIG_X86 - if (shmem->map_wc) - set_pages_array_wb(shmem->pages, obj->size >> PAGE_SHIFT); -#endif - - drm_gem_put_pages(obj, shmem->pages, - shmem->pages_mark_dirty_on_put, - shmem->pages_mark_accessed_on_put); - shmem->pages = NULL; - } + __drm_gem_shmem_put_pages(shmem); } EXPORT_SYMBOL_GPL(drm_gem_shmem_put_pages_locked); -- 2.41.0
