netdev - [PATCH v2 46/47] mm: shrinker: hold write lock to reparent shrinker nr

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date: Mon, 24 Jul 2023 17:43:53 +0800
From: Qi Zheng <zhengqi.arch@...edance.com>
To: akpm@...ux-foundation.org,
	david@...morbit.com,
	tkhai@...ru,
	vbabka@...e.cz,
	roman.gushchin@...ux.dev,
	djwong@...nel.org,
	brauner@...nel.org,
	paulmck@...nel.org,
	tytso@....edu,
	steven.price@....com,
	cel@...nel.org,
	senozhatsky@...omium.org,
	yujie.liu@...el.com,
	gregkh@...uxfoundation.org,
	muchun.song@...ux.dev
Cc: linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	x86@...nel.org,
	kvm@...r.kernel.org,
	xen-devel@...ts.xenproject.org,
	linux-erofs@...ts.ozlabs.org,
	linux-f2fs-devel@...ts.sourceforge.net,
	cluster-devel@...hat.com,
	linux-nfs@...r.kernel.org,
	linux-mtd@...ts.infradead.org,
	rcu@...r.kernel.org,
	netdev@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	linux-arm-msm@...r.kernel.org,
	dm-devel@...hat.com,
	linux-raid@...r.kernel.org,
	linux-bcache@...r.kernel.org,
	virtualization@...ts.linux-foundation.org,
	linux-fsdevel@...r.kernel.org,
	linux-ext4@...r.kernel.org,
	linux-xfs@...r.kernel.org,
	linux-btrfs@...r.kernel.org,
	Qi Zheng <zhengqi.arch@...edance.com>
Subject: [PATCH v2 46/47] mm: shrinker: hold write lock to reparent shrinker nr_deferred

For now, reparent_shrinker_deferred() is the only holder of read lock of
shrinker_rwsem. And it already holds the global cgroup_mutex, so it will
not be called in parallel.

Therefore, in order to convert shrinker_rwsem to shrinker_mutex later,
here we change to hold the write lock of shrinker_rwsem to reparent.

Signed-off-by: Qi Zheng <zhengqi.arch@...edance.com>
---
 mm/shrinker.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/shrinker.c b/mm/shrinker.c
index 744361afd520..90c045620fe3 100644
--- a/mm/shrinker.c
+++ b/mm/shrinker.c
@@ -303,7 +303,7 @@ void reparent_shrinker_deferred(struct mem_cgroup *memcg)
 		parent = root_mem_cgroup;
 
 	/* Prevent from concurrent shrinker_info expand */
-	down_read(&shrinker_rwsem);
+	down_write(&shrinker_rwsem);
 	for_each_node(nid) {
 		child_info = shrinker_info_protected(memcg, nid);
 		parent_info = shrinker_info_protected(parent, nid);
@@ -316,7 +316,7 @@ void reparent_shrinker_deferred(struct mem_cgroup *memcg)
 			}
 		}
 	}
-	up_read(&shrinker_rwsem);
+	up_write(&shrinker_rwsem);
 }
 #else
 static int shrinker_memcg_alloc(struct shrinker *shrinker)
-- 
2.30.2