Re: [PATCH v2 23/47] drm/msm: dynamically allocate the drm-msm_gem shrinker

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On 2023/7/26 15:24, Muchun Song wrote:


On 2023/7/24 17:43, Qi Zheng wrote:
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>

A nit bellow.

---
  drivers/gpu/drm/msm/msm_drv.c          |  4 ++-
  drivers/gpu/drm/msm/msm_drv.h          |  4 +--
  drivers/gpu/drm/msm/msm_gem_shrinker.c | 36 ++++++++++++++++----------
  3 files changed, 28 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
index 891eff8433a9..7f6933be703f 100644
--- a/drivers/gpu/drm/msm/msm_drv.c
+++ b/drivers/gpu/drm/msm/msm_drv.c
@@ -461,7 +461,9 @@ 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 e13a8cbd61c9..84523d4a1e58 100644
--- a/drivers/gpu/drm/msm/msm_drv.h
+++ b/drivers/gpu/drm/msm/msm_drv.h
@@ -217,7 +217,7 @@ struct msm_drm_private {
      } vram;
      struct notifier_block vmap_notifier;
-    struct shrinker shrinker;
+    struct shrinker *shrinker;
      struct drm_atomic_state *pm_state;
@@ -279,7 +279,7 @@ 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);
  int msm_gem_prime_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma); diff --git a/drivers/gpu/drm/msm/msm_gem_shrinker.c b/drivers/gpu/drm/msm/msm_gem_shrinker.c
index f38296ad8743..7daab1298c11 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 +209,27 @@ 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) {

Just "if (WARN_ON(!priv->shrinker))"

As suggested by Steven Pric in patch #24, this warning is
unnecessary, so I will remove it in the next version.


+        WARN_ON(1);
+        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 +242,8 @@ 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_unregister(priv->shrinker);
      }
  }


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