linux-kernel - [PATCH v14 02/12] drm/shmem-helper: Add pages_pin

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Message-ID: <20230722234746.205949-3-dmitry.osipenko@collabora.com>
Date:   Sun, 23 Jul 2023 02:47:36 +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 v14 02/12] drm/shmem-helper: Add pages_pin_count field

And new pages_pin_count field to struct drm_gem_shmem_object that will
determine whether pages are evictable by memory shrinker. The pages will
be evictable only when pages_pin_count=0. This patch prepares code for
addition of the memory shrinker that will utilize the new field.

Signed-off-by: Dmitry Osipenko <dmitry.osipenko@...labora.com>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c | 9 +++++++++
 include/drm/drm_gem_shmem_helper.h     | 9 +++++++++
 2 files changed, 18 insertions(+)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index 267153853e2c..42ba201dda50 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -274,15 +274,24 @@ static int drm_gem_shmem_pin_locked(struct drm_gem_shmem_object *shmem)
 	dma_resv_assert_held(shmem->base.resv);
 
 	ret = drm_gem_shmem_get_pages(shmem);
+	if (!ret)
+		shmem->pages_pin_count++;
 
 	return ret;
 }
 
 static void drm_gem_shmem_unpin_locked(struct drm_gem_shmem_object *shmem)
 {
+	struct drm_gem_object *obj = &shmem->base;
+
 	dma_resv_assert_held(shmem->base.resv);
 
+	if (drm_WARN_ON_ONCE(obj->dev, !shmem->pages_pin_count))
+		return;
+
 	drm_gem_shmem_put_pages(shmem);
+
+	shmem->pages_pin_count--;
 }
 
 /**
diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
index bf0c31aa8fbe..7111f5743006 100644
--- a/include/drm/drm_gem_shmem_helper.h
+++ b/include/drm/drm_gem_shmem_helper.h
@@ -39,6 +39,15 @@ struct drm_gem_shmem_object {
 	 */
 	unsigned int pages_use_count;
 
+	/**
+	 * @pages_pin_count:
+	 *
+	 * Reference count on the pinned pages table.
+	 * The pages allowed to be evicted by memory shrinker
+	 * only when the count is zero.
+	 */
+	unsigned int pages_pin_count;
+
 	/**
 	 * @madv: State for madvise
 	 *
-- 
2.41.0