[PATCH v13 03/10] drm/shmem-helper: Add pages_pin_count field

[Dmitry Osipenko]

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.osipe...@collabora.com>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c | 7 +++++++
 include/drm/drm_gem_shmem_helper.h     | 9 +++++++++
 2 files changed, 16 insertions(+)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c 
b/drivers/gpu/drm/drm_gem_shmem_helper.c
index 4da9c9c39b9a..81d61791f874 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -277,6 +277,8 @@ static int drm_gem_shmem_pin_locked(struct 
drm_gem_shmem_object *shmem)
        drm_WARN_ON(obj->dev, obj->import_attach);
 
        ret = drm_gem_shmem_get_pages(shmem);
+       if (!ret)
+               shmem->pages_pin_count++;
 
        return ret;
 }
@@ -289,7 +291,12 @@ static void drm_gem_shmem_unpin_locked(struct 
drm_gem_shmem_object *shmem)
 
        drm_WARN_ON(obj->dev, obj->import_attach);
 
+       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 20ddcd799df9..7d823c9fc480 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
         *
-- 
2.39.2