From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C8CAE3921E6; Thu, 30 Jul 2026 17:35:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785432927; cv=none; b=EWZt8BIVQcaTS7WnL+nFcJjBttHp+LNDJ6q5Bd+lT0uMdkC2W1pgQvJw/A/grlLWaVXv1h7oEHXBaiCBXSoNy409AsXvaU3a4a9smdofNJ72NM4X+2c+u1c08CCxkK6w9CREb+AOn5VuYjy59lVmT9U77hCiWUp7409y0MPbyuU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785432927; c=relaxed/simple; bh=HQOwbx8X2P8IdCLGqL545ONojzkVrJ1lwDNVfYBF2c0=; h=Date:To:From:Subject:Message-Id; b=RaMFAfLfAaPAUUCfMvOxmwCvY2thRlDl6JsDX4obqdNvTaJOAuNhTquBm1owFlZBSkTWe4LFbmztXxIHohFX/FcqPnCpW0Ny5UVb+Y1F2KTd0+6T+qARNE2IVCtHYJT2VDSYHYJ5oARdwpi8G2xEm3CP+O8Rk0hBWbuo3+0swi4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=1jou75/y; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="1jou75/y" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4FC411F000E9; Thu, 30 Jul 2026 17:35:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1785432925; bh=soMirDxIR8kORKHWOWj9c6KgyI3daJQMD44e9QWhMyY=; h=Date:To:From:Subject; b=1jou75/yBNSlw76VrKTADdStNyQ72cIuerKLiTzxXkjpvqbyoo3Bl6s2xeSz3b9cn BZfoBlAL6pT8MWxkoGbP0c+G10utHdnJECdtc5fdQevNFkA/umMWcd02H6Ml/bYQ6M 0RONOloEHEcGETsc6+qL+n8wVkgFUpGNUiTuMtmM= Date: Thu, 30 Jul 2026 10:35:24 -0700 To: mm-commits@vger.kernel.org,stable@vger.kernel.org,shakeel.butt@linux.dev,roman.gushchin@linux.dev,muchun.song@linux.dev,mhocko@kernel.org,hannes@cmpxchg.org,cuitao@kylinos.cn,zhangguopeng@kylinos.cn,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-memcg-stop-reclaim-when-a-limit-update-is-superseded.patch added to mm-unstable branch Message-Id: <20260730173525.4FC411F000E9@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm: memcg: stop reclaim when a limit update is superseded has been added to the -mm mm-unstable branch. Its filename is mm-memcg-stop-reclaim-when-a-limit-update-is-superseded.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memcg-stop-reclaim-when-a-limit-update-is-superseded.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: Guopeng Zhang Subject: mm: memcg: stop reclaim when a limit update is superseded Date: Fri, 24 Jul 2026 10:18:05 +0800 kernfs serializes file operations only per open file, so separate open files can update the same memory.high or memory.max file concurrently. Both handlers store the new limit before synchronous reclaim, but continue to use the writer's local target in the reclaim loop. If another writer raises or removes the limit, the first writer can continue reclaiming toward a stale target. For memory.max, this can leave the writer looping indefinitely once reclaim retries are exhausted. The OOM path sees sufficient margin under the current limit and returns true without killing, while the writer still compares usage against its stale target and records another OOM event. Check the current limit at the start of each reclaim iteration and stop if it no longer matches the writer's target. Reproducer: Populate a cgroup with anonymous memory and disable swapping. Lower memory.max from one open file, then restore it to "max" through another open file after the new limit becomes visible. Without the patch, the first writer remains blocked and repeatedly increments the OOM event counter. With the patch, it returns normally. This was not motivated by a reported production workload. We found it through automated randomized testing for our cgroup observability work and reduced it to the reproducer above. Link: https://lore.kernel.org/20260724021805.1234583-1-guopeng.zhang@linux.dev Fixes: 8c8c383c04f6 ("mm: memcontrol: try harder to set a new memory.high") Fixes: b6e6edcfa405 ("mm: memcontrol: reclaim and OOM kill when shrinking memory.max below usage") Signed-off-by: Guopeng Zhang Acked-by: Tao Cui Acked-by: Johannes Weiner Cc: Michal Hocko Cc: Muchun Song Cc: Roman Gushchin Cc: Shakeel Butt Cc: Signed-off-by: Andrew Morton --- mm/memcontrol.c | 6 ++++++ 1 file changed, 6 insertions(+) --- a/mm/memcontrol.c~mm-memcg-stop-reclaim-when-a-limit-update-is-superseded +++ a/mm/memcontrol.c @@ -4837,6 +4837,9 @@ static ssize_t memory_high_write(struct unsigned long nr_pages = page_counter_read(&memcg->memory); unsigned long reclaimed; + if (high != READ_ONCE(memcg->memory.high)) + break; + if (nr_pages <= high) break; @@ -4892,6 +4895,9 @@ static ssize_t memory_max_write(struct k for (;;) { unsigned long nr_pages = page_counter_read(&memcg->memory); + if (max != READ_ONCE(memcg->memory.max)) + break; + if (nr_pages <= max) break; _ Patches currently in -mm which might be from zhangguopeng@kylinos.cn are mm-memcontrol-update-state_local-when-flushing-nmi-stats.patch mm-memcg-v1-account-vmpressure-event-allocations.patch mm-memcg-v1-fix-wrong-linux-mm-list-address-in-deprecation-warnings.patch mm-memcontrol-drop-unused-cpu-argument-from-flush_nmi_stats.patch mm-memcontrol-factor-out-memcg-kmem-uncharge-sequence.patch mm-memcg-v1-make-mem_cgroup_oom_notify_cb-return-void.patch mm-memcg-stop-reclaim-when-a-limit-update-is-superseded.patch