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

[Muchun Song <muchun.song@xxxxxxxxx>]

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))"

> +               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);
>         }
>   }