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

[Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>]

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);
> >       }
> >   }