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Date: Wed, 26 Jul 2023 15:24:02 +0800
From: Muchun Song <muchun.song@...ux.dev>
To: Qi Zheng <zhengqi.arch@...edance.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org,
kvm@...r.kernel.org, xen-devel@...ts.xenproject.org,
linux-erofs@...ts.ozlabs.org,
linux-f2fs-devel@...ts.sourceforge.net, cluster-devel@...hat.com,
linux-nfs@...r.kernel.org, linux-mtd@...ts.infradead.org,
rcu@...r.kernel.org, netdev@...r.kernel.org,
dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
dm-devel@...hat.com, linux-raid@...r.kernel.org,
linux-bcache@...r.kernel.org,
virtualization@...ts.linux-foundation.org,
linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
linux-xfs@...r.kernel.org, linux-btrfs@...r.kernel.org,
akpm@...ux-foundation.org, david@...morbit.com, tkhai@...ru,
vbabka@...e.cz, roman.gushchin@...ux.dev, djwong@...nel.org,
brauner@...nel.org, paulmck@...nel.org, tytso@....edu,
steven.price@....com, cel@...nel.org, senozhatsky@...omium.org,
yujie.liu@...el.com, gregkh@...uxfoundation.org
Subject: Re: [PATCH v2 23/47] drm/msm: dynamically allocate the drm-msm_gem
shrinker
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@...edance.com>
Reviewed-by: Muchun Song <songmuchun@...edance.com>
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);
> }
> }
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