[PATCH v4 24/48] drm/msm: dynamically allocate the drm-msm_gem shrinker

[Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>]

In preparation for implementing lockless slab shrink, use new APIs to
dynamically allocate the drm-msm_gem shrinker, so that it can be freed
asynchronously using kfree_rcu(). Then it doesn't need to wait for RCU
read-side critical section when releasing the struct msm_drm_private.

Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
---
 drivers/gpu/drm/msm/msm_drv.c          |  4 ++-
 drivers/gpu/drm/msm/msm_drv.h          |  4 +--
 drivers/gpu/drm/msm/msm_gem_shrinker.c | 34 ++++++++++++++++----------
 3 files changed, 26 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
index 4bd028fa7500..7f20249d6071 100644
--- a/drivers/gpu/drm/msm/msm_drv.c
+++ b/drivers/gpu/drm/msm/msm_drv.c
@@ -462,7 +462,9 @@ static int msm_drm_init(struct device *dev, const struct drm_driver *drv)
 	if (ret)
 		goto err_msm_uninit;
 
-	msm_gem_shrinker_init(ddev);
+	ret = msm_gem_shrinker_init(ddev);
+	if (ret)
+		goto err_msm_uninit;
 
 	if (priv->kms_init) {
 		ret = priv->kms_init(ddev);
diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
index 02fd6c7d0bb7..e2fc56f161b5 100644
--- a/drivers/gpu/drm/msm/msm_drv.h
+++ b/drivers/gpu/drm/msm/msm_drv.h
@@ -221,7 +221,7 @@ struct msm_drm_private {
 	} vram;
 
 	struct notifier_block vmap_notifier;
-	struct shrinker shrinker;
+	struct shrinker *shrinker;
 
 	struct drm_atomic_state *pm_state;
 
@@ -283,7 +283,7 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data,
 unsigned long msm_gem_shrinker_shrink(struct drm_device *dev, unsigned long nr_to_scan);
 #endif
 
-void msm_gem_shrinker_init(struct drm_device *dev);
+int msm_gem_shrinker_init(struct drm_device *dev);
 void msm_gem_shrinker_cleanup(struct drm_device *dev);
 
 struct sg_table *msm_gem_prime_get_sg_table(struct drm_gem_object *obj);
diff --git a/drivers/gpu/drm/msm/msm_gem_shrinker.c b/drivers/gpu/drm/msm/msm_gem_shrinker.c
index f38296ad8743..20699993e4f8 100644
--- a/drivers/gpu/drm/msm/msm_gem_shrinker.c
+++ b/drivers/gpu/drm/msm/msm_gem_shrinker.c
@@ -34,8 +34,7 @@ static bool can_block(struct shrink_control *sc)
 static unsigned long
 msm_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
 {
-	struct msm_drm_private *priv =
-		container_of(shrinker, struct msm_drm_private, shrinker);
+	struct msm_drm_private *priv = shrinker->private_data;
 	unsigned count = priv->lru.dontneed.count;
 
 	if (can_swap())
@@ -100,8 +99,7 @@ active_evict(struct drm_gem_object *obj)
 static unsigned long
 msm_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
 {
-	struct msm_drm_private *priv =
-		container_of(shrinker, struct msm_drm_private, shrinker);
+	struct msm_drm_private *priv = shrinker->private_data;
 	struct {
 		struct drm_gem_lru *lru;
 		bool (*shrink)(struct drm_gem_object *obj);
@@ -148,10 +146,11 @@ msm_gem_shrinker_shrink(struct drm_device *dev, unsigned long nr_to_scan)
 	struct shrink_control sc = {
 		.nr_to_scan = nr_to_scan,
 	};
-	int ret;
+	unsigned long ret = SHRINK_STOP;
 
 	fs_reclaim_acquire(GFP_KERNEL);
-	ret = msm_gem_shrinker_scan(&priv->shrinker, &sc);
+	if (priv->shrinker)
+		ret = msm_gem_shrinker_scan(priv->shrinker, &sc);
 	fs_reclaim_release(GFP_KERNEL);
 
 	return ret;
@@ -210,16 +209,25 @@ msm_gem_shrinker_vmap(struct notifier_block *nb, unsigned long event, void *ptr)
  *
  * This function registers and sets up the msm shrinker.
  */
-void msm_gem_shrinker_init(struct drm_device *dev)
+int msm_gem_shrinker_init(struct drm_device *dev)
 {
 	struct msm_drm_private *priv = dev->dev_private;
-	priv->shrinker.count_objects = msm_gem_shrinker_count;
-	priv->shrinker.scan_objects = msm_gem_shrinker_scan;
-	priv->shrinker.seeks = DEFAULT_SEEKS;
-	WARN_ON(register_shrinker(&priv->shrinker, "drm-msm_gem"));
+
+	priv->shrinker = shrinker_alloc(0, "drm-msm_gem");
+	if (!priv->shrinker)
+		return -ENOMEM;
+
+	priv->shrinker->count_objects = msm_gem_shrinker_count;
+	priv->shrinker->scan_objects = msm_gem_shrinker_scan;
+	priv->shrinker->seeks = DEFAULT_SEEKS;
+	priv->shrinker->private_data = priv;
+
+	shrinker_register(priv->shrinker);
 
 	priv->vmap_notifier.notifier_call = msm_gem_shrinker_vmap;
 	WARN_ON(register_vmap_purge_notifier(&priv->vmap_notifier));
+
+	return 0;
 }
 
 /**
@@ -232,8 +240,8 @@ void msm_gem_shrinker_cleanup(struct drm_device *dev)
 {
 	struct msm_drm_private *priv = dev->dev_private;
 
-	if (priv->shrinker.nr_deferred) {
+	if (priv->shrinker) {
 		WARN_ON(unregister_vmap_purge_notifier(&priv->vmap_notifier));
-		unregister_shrinker(&priv->shrinker);
+		shrinker_free(priv->shrinker);
 	}
 }
-- 
2.30.2