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Thu, 28 Jul 2022 02:13:51 -0700 (PDT) From: tujinjiang@bytedance.com To: mhocko@suse.com Cc: shy828301@gmail.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Jinjiang Tu Subject: [PATCH v2] vmscan: Do not free nr_deferred for memcg aware shrinkers Date: Thu, 28 Jul 2022 17:13:41 +0800 Message-Id: <20220728091341.20820-1-tujinjiang@bytedance.com> X-Mailer: git-send-email 2.17.1 ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1658999638; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:content-type: content-transfer-encoding:in-reply-to:references:dkim-signature; bh=ifRf6yNz0UpoCdtj88m7UxYW0lnEYEGGWf6UZFMfb/E=; b=PY39RlLQMgMpT2mvB0QSrWBEhwwuRaZk/NuH4Ys77HnilFK+cvSfFgHFr/c/VHWTbC3rLf WoltVbTynWZm4CDitXP7gS2pWvazlMvVjD5v3SYpeM7aJgBhDKjORbHv4z28wi3PtgIM/6 dsNLfgjaD4UZ5jGAARCyTpyeR7VwfbY= ARC-Authentication-Results: i=1; imf31.hostedemail.com; dkim=pass header.d=bytedance-com.20210112.gappssmtp.com header.s=20210112 header.b=UMqibFaM; spf=pass (imf31.hostedemail.com: domain of tujinjiang@bytedance.com designates 209.85.210.173 as permitted sender) smtp.mailfrom=tujinjiang@bytedance.com; dmarc=pass (policy=none) header.from=bytedance.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1658999638; a=rsa-sha256; cv=none; b=dQ9pWFGapzw3L1pdEWhGZwoPaM0AOjKirNobDplNVsEqhrPFLR3B0I7dsaEpVwBoilDtwE vjJngwXyoSJOmqnZP37BbKjuAC5VvHkNkupxFx1vBRr1Wg6GU6WU3eTqKTI9Ck9zrkDexm 0JukmY13m4grpFcK6FYwzMk3EduO6PU= X-Stat-Signature: o9xunspguu4z4zg614r3torqiau7xopq X-Rspamd-Queue-Id: 8333720013 X-Rspam-User: Authentication-Results: imf31.hostedemail.com; dkim=pass header.d=bytedance-com.20210112.gappssmtp.com header.s=20210112 header.b=UMqibFaM; spf=pass (imf31.hostedemail.com: domain of tujinjiang@bytedance.com designates 209.85.210.173 as permitted sender) smtp.mailfrom=tujinjiang@bytedance.com; dmarc=pass (policy=none) header.from=bytedance.com X-Rspamd-Server: rspam06 X-HE-Tag: 1658999637-713092 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Jinjiang Tu When a memcg aware shrinker is registered by register_shrinker(), shrinker->nr_deferred will not be initialized. But when the shrinker is unregistered by unregister_shrinker(), shrinker->nr_deferred will be freed. Luckily, the memcg aware shrinkers in the current kernel are pre-zeroed. But a new memcg aware shrinker may be added in the future, and we should not assume the shrinker is pre-zeroed. Another unregister API free_prealloced_shrinker() does not assume the shrinker is pre-zered and free shrinker->nr_deferred only if it is not memcg aware. So unregister_shrinker() should do like free_prealloced_shrinker(). Signed-off-by: Jinjiang Tu --- mm/vmscan.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index f7d9a683e3a7..f8a9a5349b6e 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -675,8 +675,11 @@ void unregister_shrinker(struct shrinker *shrinker) down_write(&shrinker_rwsem); list_del(&shrinker->list); shrinker->flags &= ~SHRINKER_REGISTERED; - if (shrinker->flags & SHRINKER_MEMCG_AWARE) + if (shrinker->flags & SHRINKER_MEMCG_AWARE) { unregister_memcg_shrinker(shrinker); + up_write(&shrinker_rwsem); + return; + } up_write(&shrinker_rwsem); kfree(shrinker->nr_deferred);