linux-kernel - [PATCH v19 12/30] drm/shmem-helper: Prepare drm_gem_shmem

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Date: Fri,  5 Jan 2024 21:46:06 +0300
From: Dmitry Osipenko <dmitry.osipenko@...labora.com>
To: David Airlie <airlied@...il.com>,
	Gerd Hoffmann <kraxel@...hat.com>,
	Gurchetan Singh <gurchetansingh@...omium.org>,
	Chia-I Wu <olvaffe@...il.com>,
	Daniel Vetter <daniel@...ll.ch>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	Christian König <christian.koenig@....com>,
	Qiang Yu <yuq825@...il.com>,
	Steven Price <steven.price@....com>,
	Boris Brezillon <boris.brezillon@...labora.com>,
	Emma Anholt <emma@...olt.net>,
	Melissa Wen <mwen@...lia.com>
Cc: dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	kernel@...labora.com,
	virtualization@...ts.linux-foundation.org
Subject: [PATCH v19 12/30] drm/shmem-helper: Prepare drm_gem_shmem_free() to shrinker addition

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 <dmitry.osipenko@...labora.com>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c | 40 ++++++++++++++------------
 1 file changed, 21 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index 3403700780c3..799a3c5015ad 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -128,6 +128,22 @@ 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_free_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;
+}
+
 /**
  * drm_gem_shmem_free - Free resources associated with a shmem GEM object
  * @shmem: shmem GEM object to free
@@ -142,8 +158,6 @@ 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) {
@@ -152,13 +166,12 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
 			sg_free_table(shmem->sgt);
 			kfree(shmem->sgt);
 		}
-		if (shmem->pages)
-			drm_gem_shmem_put_pages_locked(shmem);
+		if (shmem->pages &&
+		    refcount_dec_and_test(&shmem->pages_use_count))
+			drm_gem_shmem_free_pages(shmem);
 
 		drm_WARN_ON(obj->dev, refcount_read(&shmem->pages_use_count));
 		drm_WARN_ON(obj->dev, refcount_read(&shmem->pages_pin_count));
-
-		dma_resv_unlock(shmem->base.resv);
 	}
 
 	drm_gem_object_release(obj);
@@ -208,21 +221,10 @@ 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;
-	}
+	if (refcount_dec_and_test(&shmem->pages_use_count))
+		drm_gem_shmem_free_pages(shmem);
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_put_pages_locked);
 
-- 
2.43.0