mm: assign id to every memcg-aware shrinker

Introduce 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 to represent a memcg-aware shrinkers in memcg
shrinkers map.

Since all memcg-aware shrinkers are based on list_lru, which is
per-memcg in case of !CONFIG_MEMCG_KMEM only, the new functionality will
be under this config option.

[ktkhai@virtuozzo.com: v9]
Link: http://lkml.kernel.org/r/153112546435.4097.10607140323811756557.stgit@localhost.localdomain
Link: http://lkml.kernel.org/r/153063054586.1818.6041047871606697364.stgit@localhost.localdomain
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Acked-by: Vladimir Davydov <vdavydov.dev@gmail.com>
Tested-by: Shakeel Butt <shakeelb@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Josef Bacik <jbacik@fb.com>
Cc: Li RongQing <lirongqing@baidu.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Sahitya Tummala <stummala@codeaurora.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <longman@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
index 6794490f25b2bd80cfb6fc4c8dec7067e824e100..7ca9c18cf130a64059285e40d8723990511a51c4 100644 (file)
--- a/include/linux/shrinker.h
+++ b/include/linux/shrinker.h
@@ -66,6 +66,10 @@ struct shrinker {
 
        /* These are for internal use */
        struct list_head list;
+#ifdef CONFIG_MEMCG_KMEM
+       /* ID in shrinker_idr */
+       int id;
+#endif
        /* objs pending delete, per node */
        atomic_long_t *nr_deferred;
 };

diff --git a/mm/vmscan.c b/mm/vmscan.c
index a00d94530e5793cbc50736573228a83eead2d068..5cb4f779ea4a95169fbdf8c510de5848da4aa1ef 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -169,6 +169,50 @@ unsigned long vm_total_pages;
 static LIST_HEAD(shrinker_list);
 static DECLARE_RWSEM(shrinker_rwsem);
 
+#ifdef CONFIG_MEMCG_KMEM
+static DEFINE_IDR(shrinker_idr);
+static int shrinker_nr_max;
+
+static int prealloc_memcg_shrinker(struct shrinker *shrinker)
+{
+       int id, ret = -ENOMEM;
+
+       down_write(&shrinker_rwsem);
+       /* This may call shrinker, so it must use down_read_trylock() */
+       id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL);
+       if (id < 0)
+               goto unlock;
+
+       if (id >= shrinker_nr_max)
+               shrinker_nr_max = id + 1;
+       shrinker->id = id;
+       ret = 0;
+unlock:
+       up_write(&shrinker_rwsem);
+       return ret;
+}
+
+static void unregister_memcg_shrinker(struct shrinker *shrinker)
+{
+       int id = shrinker->id;
+
+       BUG_ON(id < 0);
+
+       down_write(&shrinker_rwsem);
+       idr_remove(&shrinker_idr, id);
+       up_write(&shrinker_rwsem);
+}
+#else /* CONFIG_MEMCG_KMEM */
+static int prealloc_memcg_shrinker(struct shrinker *shrinker)
+{
+       return 0;
+}
+
+static void unregister_memcg_shrinker(struct shrinker *shrinker)
+{
+}
+#endif /* CONFIG_MEMCG_KMEM */
+
 #ifdef CONFIG_MEMCG
 static bool global_reclaim(struct scan_control *sc)
 {
@@ -313,11 +357,28 @@ int prealloc_shrinker(struct shrinker *shrinker)
        shrinker->nr_deferred = kzalloc(size, GFP_KERNEL);
        if (!shrinker->nr_deferred)
                return -ENOMEM;
+
+       if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
+               if (prealloc_memcg_shrinker(shrinker))
+                       goto free_deferred;
+       }
+
        return 0;
+
+free_deferred:
+       kfree(shrinker->nr_deferred);
+       shrinker->nr_deferred = NULL;
+       return -ENOMEM;
 }
 
 void free_prealloced_shrinker(struct shrinker *shrinker)
 {
+       if (!shrinker->nr_deferred)
+               return;
+
+       if (shrinker->flags & SHRINKER_MEMCG_AWARE)
+               unregister_memcg_shrinker(shrinker);
+
        kfree(shrinker->nr_deferred);
        shrinker->nr_deferred = NULL;
 }
@@ -347,6 +408,8 @@ void unregister_shrinker(struct shrinker *shrinker)
 {
        if (!shrinker->nr_deferred)
                return;
+       if (shrinker->flags & SHRINKER_MEMCG_AWARE)
+               unregister_memcg_shrinker(shrinker);
        down_write(&shrinker_rwsem);
        list_del(&shrinker->list);
        up_write(&shrinker_rwsem);