+ mm-vmscan-remove-shrinker_rwsem-from-synchronize_shrinkers.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm: vmscan: remove shrinker_rwsem from synchronize_shrinkers()
has been added to the -mm mm-unstable branch.  Its filename is
     mm-vmscan-remove-shrinker_rwsem-from-synchronize_shrinkers.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-vmscan-remove-shrinker_rwsem-from-synchronize_shrinkers.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Qi Zheng <zhengqi.arch@bytedance.com>
Subject: mm: vmscan: remove shrinker_rwsem from synchronize_shrinkers()
Date: Tue, 7 Mar 2023 14:56:04 +0800

Now there are no readers of shrinker_rwsem, so synchronize_shrinkers()
does not need to hold the writer of shrinker_rwsem to wait for all running
shinkers to complete, synchronize_srcu() is enough.

Link: https://lkml.kernel.org/r/20230307065605.58209-8-zhengqi.arch@bytedance.com
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kirill Tkhai <tkhai@ya.ru>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
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>
---

 mm/vmscan.c |    8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

--- a/mm/vmscan.c~mm-vmscan-remove-shrinker_rwsem-from-synchronize_shrinkers
+++ a/mm/vmscan.c
@@ -796,15 +796,11 @@ 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);
 }
_

Patches currently in -mm which might be from zhengqi.arch@bytedance.com are

mm-vmscan-add-a-map_nr_max-field-to-shrinker_info.patch
mm-vmscan-make-global-slab-shrink-lockless.patch
mm-vmscan-make-memcg-slab-shrink-lockless.patch
mm-shrinkers-make-count-and-scan-in-shrinker-debugfs-lockless.patch
mm-vmscan-hold-write-lock-to-reparent-shrinker-nr_deferred.patch
mm-vmscan-remove-shrinker_rwsem-from-synchronize_shrinkers.patch
mm-shrinkers-convert-shrinker_rwsem-to-mutex.patch