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Subject[PATCH v2 01/12] mm: Assign id to every memcg-aware shrinker
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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@virtuozzo.com>
---
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;
/* 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);
+
+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;
+ }
+
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);
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