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Subject[PATCH 01/10] 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 | 1 +
mm/vmscan.c | 59 ++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 60 insertions(+)

diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
index a3894918a436..738de8ef5246 100644
--- a/include/linux/shrinker.h
+++ b/include/linux/shrinker.h
@@ -66,6 +66,7 @@ struct shrinker {

/* These are for internal use */
struct list_head list;
+ int id;
/* objs pending delete, per node */
atomic_long_t *nr_deferred;
};
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 8fcd9f8d7390..91b5120b924f 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -159,6 +159,56 @@ unsigned long vm_total_pages;
static LIST_HEAD(shrinker_list);
static DECLARE_RWSEM(shrinker_rwsem);

+#if defined(CONFIG_MEMCG) && !defined(CONFIG_SLOB)
+static DEFINE_IDA(bitmap_id_ida);
+static DECLARE_RWSEM(bitmap_rwsem);
+static int bitmap_id_start;
+
+static int alloc_shrinker_id(struct shrinker *shrinker)
+{
+ int id, ret;
+
+ if (!(shrinker->flags & SHRINKER_MEMCG_AWARE))
+ return 0;
+retry:
+ ida_pre_get(&bitmap_id_ida, GFP_KERNEL);
+ down_write(&bitmap_rwsem);
+ ret = ida_get_new_above(&bitmap_id_ida, bitmap_id_start, &id);
+ if (!ret) {
+ shrinker->id = id;
+ bitmap_id_start = shrinker->id + 1;
+ }
+ up_write(&bitmap_rwsem);
+ if (ret == -EAGAIN)
+ goto retry;
+
+ return ret;
+}
+
+static void free_shrinker_id(struct shrinker *shrinker)
+{
+ int id = shrinker->id;
+
+ if (!(shrinker->flags & SHRINKER_MEMCG_AWARE))
+ return;
+
+ down_write(&bitmap_rwsem);
+ ida_remove(&bitmap_id_ida, id);
+ if (bitmap_id_start > id)
+ bitmap_id_start = id;
+ up_write(&bitmap_rwsem);
+}
+#else /* CONFIG_MEMCG && !CONFIG_SLOB */
+static int alloc_shrinker_id(struct shrinker *shrinker)
+{
+ return 0;
+}
+
+static void free_shrinker_id(struct shrinker *shrinker)
+{
+}
+#endif /* CONFIG_MEMCG && !CONFIG_SLOB */
+
#ifdef CONFIG_MEMCG
static bool global_reclaim(struct scan_control *sc)
{
@@ -269,10 +319,18 @@ int register_shrinker(struct shrinker *shrinker)
if (!shrinker->nr_deferred)
return -ENOMEM;

+ if (alloc_shrinker_id(shrinker))
+ 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);

@@ -286,6 +344,7 @@ void unregister_shrinker(struct shrinker *shrinker)
down_write(&shrinker_rwsem);
list_del(&shrinker->list);
up_write(&shrinker_rwsem);
+ free_shrinker_id(shrinker);
kfree(shrinker->nr_deferred);
shrinker->nr_deferred = NULL;
}
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