Commit 1643db98 authored Mar 13, 2023 by Qi Zheng Committed by Andrew Morton Mar 28, 2023

mm: vmscan: remove shrinker_rwsem from synchronize_shrinkers()

Currently, the synchronize_shrinkers() is only used by TTM pool.  It only
requires that no shrinkers run in parallel, and doesn't care about
registering and unregistering of shrinkers.

Since slab shrink is protected by SRCU, synchronize_srcu() is sufficient
to ensure that no shrinker is running in parallel.  So the shrinker_rwsem
in synchronize_shrinkers() is no longer needed, just remove it.

Link: https://lkml.kernel.org/r/20230313112819.38938-8-zhengqi.arch@bytedance.com


Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Kirill Tkhai <tkhai@ya.ru>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Christian König <christian.koenig@amd.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Sultan Alsawaf <sultan@kerneltoast.com>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

parent b3cabea3

mm/vmscan.c

+2 −6

Original line number	Diff line number	Diff line
		@@ -790,15 +790,11 @@ EXPORT_SYMBOL(unregister_shrinker);
		/**
		* synchronize_shrinkers - Wait for all running shrinkers to complete.
		*
		* This is equivalent to calling unregister_shrink() and register_shrinker(),
		* but atomically and with less overhead. This is useful to guarantee that all
		* shrinker invocations have seen an update, before freeing memory, similar to
		* rcu.
		* This is useful to guarantee that all shrinker invocations have seen an
		* update, before freeing memory.
		*/
		void synchronize_shrinkers(void)
		{
		down_write(&shrinker_rwsem);
		up_write(&shrinker_rwsem);
		atomic_inc(&shrinker_srcu_generation);
		synchronize_srcu(&shrinker_srcu);
		}