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 2B0C32DCF55 for ; Wed, 7 Oct 2026 00:50:55 +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=1791334256; cv=none; b=lJWL+OvuQTG4kYDXvJtmajz7l2gtP+WL+0iJ8EOPHNb/pjpz+NQjOwiTAhcvE/N/Gn+IwntE5526hoLyUkI7241gAD5TFRggUDcB2Ev7UJ+j7aUauwWgD7FwDBJsKToaLBd4YynNa9VBIRvs4augaF0d6fBJh1gBBMqisg5+KZg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791334256; c=relaxed/simple; bh=8/GWQHZOXolk+ykUdu8Qp9A9HkJ8kHHYZ5LDoeNcfjM=; h=Date:To:From:Subject:Message-Id; b=KQsZDaL9gg1LKLnbdiWl347s1FDsf+rbKJQNTj6cwGxD5/4tAiYY1e380AUC2TJKtYa/Dvw55tM4hkZGR4TBmuC+PRT3zJFB11RdcHtg8boW09tk+c0aAworMoHFnuLoEHz4W7EKLj/13VxsczjcSYqKRIVohwlXtPWqyf7e5cM= 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=DQL/YHDx; 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="DQL/YHDx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 025551F0089B; Wed, 7 Oct 2026 00:50:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1791334255; bh=2j+4NPj+YyQXd4t41WJFni7wnZrWdIv5tflMX087dHc=; h=Date:To:From:Subject; b=DQL/YHDx/svc41W3V2Z6wvD80vEryCSqTZ1D7QS6dNjvs/VdVpk4BJpzxzoK6oSHI F3p5jPJrS5o0XC4jkTZHsJAv41vi0XkeMZaj++mfGizsuh6x4CebV9jGKljj+L/Q3q sbwtQfvsZgIsbdJ4WjBvDWd0BVpE4BgHrZYm+DiM= Date: Tue, 06 Oct 2026 17:50:54 -0700 To: mm-commits@vger.kernel.org,tj@kernel.org,shakeel.butt@linux.dev,roman.gushchin@linux.dev,muchun.song@linux.dev,mkoutny@suse.com,mhocko@kernel.org,hannes@cmpxchg.org,davidf@vimeo.com,cuitao@kylinos.cn,chenridong@xiaomi.com,akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-stable] mm-memcg-fix-memorypeak-reset-clobbering-other-fds-watermark.patch removed from -mm tree Message-Id: <20261007005055.025551F0089B@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: mm, memcg: fix memory.peak reset clobbering other fds' watermark has been removed from the -mm tree. Its filename was mm-memcg-fix-memorypeak-reset-clobbering-other-fds-watermark.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Ridong Chen Subject: mm, memcg: fix memory.peak reset clobbering other fds' watermark Date: Sun, 30 Aug 2026 08:20:44 +0800 Writing to memory.peak resets the peak for that fd only. Each fd is a watcher and reads back max(its own value, the shared local_watermark). peak_write() resets by lowering local_watermark to the current usage. To keep the other watchers' peaks it then walks the watcher list, but it stores the current usage into them instead of the old watermark. So once usage has dropped from a peak, a reset on one fd wrongly drags every other fd's peak down too, even fds that never reset. Reproduced on 7.2.0-rc5-next under QEMU, two fds A and B on one cgroup: B sees the peak (410624 KB), usage drops, then A resets -- and B's peak collapses to 1060 KB although B never reset. With this patch B keeps reading 410624 KB. Fix: save the old watermark before lowering it and use that to floor the other watchers, so a reset only affects the fd that issued it. Link: https://lore.kernel.org/20260830002044.1938621-3-ridong.chen@linux.dev Fixes: c6f53ed8f213 ("mm, memcg: cg2 memory{.swap,}.peak write handlers") Signed-off-by: Ridong Chen Signed-off-by: Andrew Morton Closes: https://sashiko.dev/#/patchset/20260807090000.1532495-1-ridong.chen@linux.dev Acked-by: Tao Cui Acked-by: Johannes Weiner Acked-by: Shakeel Butt Assisted-by: Claude:claude-opus-4-8 Cc: David Finkel Cc: Michal Hocko Cc: Michal Koutný Cc: Muchun Song Cc: Roman Gushchin Cc: Tejun Heo --- mm/memcontrol.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) --- a/mm/memcontrol.c~mm-memcg-fix-memorypeak-reset-clobbering-other-fds-watermark +++ a/mm/memcontrol.c @@ -4775,7 +4775,7 @@ static ssize_t peak_write(struct kernfs_ loff_t off, struct page_counter *pc, struct list_head *watchers) { - unsigned long usage; + unsigned long usage, old_watermark; struct cgroup_of_peak *peer_ctx; struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of)); struct cgroup_of_peak *ofp = of_peak(of); @@ -4783,11 +4783,12 @@ static ssize_t peak_write(struct kernfs_ spin_lock(&memcg->peaks_lock); usage = page_counter_read(pc); + old_watermark = READ_ONCE(pc->local_watermark); WRITE_ONCE(pc->local_watermark, usage); list_for_each_entry(peer_ctx, watchers, list) - if (usage > peer_ctx->value) - WRITE_ONCE(peer_ctx->value, usage); + if (peer_ctx != ofp && old_watermark > peer_ctx->value) + WRITE_ONCE(peer_ctx->value, old_watermark); /* initial write, register watcher */ if (ofp->value == OFP_PEAK_UNSET) _ Patches currently in -mm which might be from chenridong@xiaomi.com are mm-page_counter-avoid-integer-overflow-in-effective_protection.patch mm-mglru-fix-ineffective-memory-protection-for-non-kswapd-reclaim.patch mm-vmscan-put-rotation-missed-folios-at-the-lru-tail.patch