On Tue, Apr 17, 2018 at 09:53:02PM +0300, Kirill Tkhai wrote:
> The patch introduces shrinker::id number, which is used to enumerate
> memcg-aware shrinkers. The number start from 0, and the code tries
> to maintain it as small as possible.
>
> This will be used as to represent a memcg-aware shrinkers in memcg
> shrinkers map.
>
> Signed-off-by: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>
> ---
> include/linux/shrinker.h | 2 ++
> mm/vmscan.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 53 insertions(+)
>
> diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
> index a3894918a436..86b651fa2846 100644
> --- a/include/linux/shrinker.h
> +++ b/include/linux/shrinker.h
> @@ -66,6 +66,8 @@ struct shrinker {
>
> /* These are for internal use */
> struct list_head list;
> + /* ID in shrinkers_id_idr */
> + int id;
This should be under ifdef CONFIG_MEMCG && CONFIG_SLOB.
> /* objs pending delete, per node */
> atomic_long_t *nr_deferred;
> };
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 8b920ce3ae02..4f02fe83537e 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -169,6 +169,43 @@ unsigned long vm_total_pages;
> static LIST_HEAD(shrinker_list);
> static DECLARE_RWSEM(shrinker_rwsem);
>
> +#if defined(CONFIG_MEMCG) && !defined(CONFIG_SLOB)
> +static DEFINE_IDR(shrinkers_id_idr);
IMO shrinker_idr would be a better name.
> +
> +static int add_memcg_shrinker(struct shrinker *shrinker)
> +{
> + int id, ret;
> +
> + down_write(&shrinker_rwsem);
> + ret = id = idr_alloc(&shrinkers_id_idr, shrinker, 0, 0, GFP_KERNEL);
> + if (ret < 0)
> + goto unlock;
> + shrinker->id = id;
> + ret = 0;
> +unlock:
> + up_write(&shrinker_rwsem);
> + return ret;
> +}
> +
> +static void del_memcg_shrinker(struct shrinker *shrinker)
> +{
> + int id = shrinker->id;
> +
> + down_write(&shrinker_rwsem);
> + idr_remove(&shrinkers_id_idr, id);
> + up_write(&shrinker_rwsem);
> +}
> +#else /* CONFIG_MEMCG && !CONFIG_SLOB */
> +static int add_memcg_shrinker(struct shrinker *shrinker)
> +{
> + return 0;
> +}
> +
> +static void del_memcg_shrinker(struct shrinker *shrinker)
> +{
> +}
> +#endif /* CONFIG_MEMCG && !CONFIG_SLOB */
> +
> #ifdef CONFIG_MEMCG
> static bool global_reclaim(struct scan_control *sc)
> {
> @@ -306,6 +343,7 @@ unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru, int zone
> int register_shrinker(struct shrinker *shrinker)
> {
> size_t size = sizeof(*shrinker->nr_deferred);
> + int ret;
>
> if (shrinker->flags & SHRINKER_NUMA_AWARE)
> size *= nr_node_ids;
> @@ -314,10 +352,21 @@ int register_shrinker(struct shrinker *shrinker)
> if (!shrinker->nr_deferred)
> return -ENOMEM;
>
> + if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
> + ret = add_memcg_shrinker(shrinker);
> + if (ret)
> + goto free_deferred;
> + }
> +
This doesn't apply anymore, not after commit 8e04944f0ea8a ("mm,vmscan:
Allow preallocating memory for register_shrinker()"). Please rebase.
I guess now you have to allocate an id in prealloc_shrinker and set the
pointer (with idr_replace) in register_shrinker_prepared.
> down_write(&shrinker_rwsem);
> list_add_tail(&shrinker->list, &shrinker_list);
> up_write(&shrinker_rwsem);
> return 0;
> +
> +free_deferred:
> + kfree(shrinker->nr_deferred);
> + shrinker->nr_deferred = NULL;
> + return -ENOMEM;
> }
> EXPORT_SYMBOL(register_shrinker);
>
> @@ -328,6 +377,8 @@ void unregister_shrinker(struct shrinker *shrinker)
> {
> if (!shrinker->nr_deferred)
> return;
> + if (shrinker->flags & SHRINKER_MEMCG_AWARE)
> + del_memcg_shrinker(shrinker);
> down_write(&shrinker_rwsem);
> list_del(&shrinker->list);
> up_write(&shrinker_rwsem);
>
