From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-187.mta1.migadu.com (out-187.mta1.migadu.com [95.215.58.187]) (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 6E3382F25F5 for ; Fri, 24 Jul 2026 02:18:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.187 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784859488; cv=none; b=igDIG7uSu7ERLuw8WRaGldyEnfk67v/2pF+7bBwbBmfG/FLR8eKb4c3FXWiWIB04fCQPIchjh21Oc6qRMaLPi57g54YC6XG+gSSaa7DrG7Qpt9MiNCqia3anxR8brBwj+S0gr9CTg1OC3aaWn+SnWVo261MV63BtkuZAIzsN8/w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784859488; c=relaxed/simple; bh=T1lioKmUtb8VUim2b8a2stXptMGrLsI4eICPczJnwTE=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=mSP6YW+O5iFfLqbjXhZmQwiCwevKwqREPNOf8ftVVCi/sdZUqgP5V2TZq7WMwmFQqqrxflFfmtyIjjXDnGvLvP9XMsuaJD79HWQp3xF0TfV1nkE+0Cy5+GWYRVnkMqnxJX0lrOK8FhZaOe8kt5Apw7S0Um4h2Z93zXNCDtERf8U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=m6LyyPZe; arc=none smtp.client-ip=95.215.58.187 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="m6LyyPZe" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1784859482; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=dkDxI/YU4h74RWLt0j/KtkqxL8bNC1CurQ3sW+7Nc40=; b=m6LyyPZeNG8i5rjVFkZXPlsO0v9FnA42zs3OT99CGDpyOYelE39pPRuFwb2gnhWuxVFMi5 fWw090Je9B4PLWam00PonOTRKdW/2S9MztGP9S/nourLMlqjLDNLuCKWh+CnH9S1UymNES SQMQVCqlWejoODsnz7GdinNbRZ0xZls= From: Guopeng Zhang To: Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Andrew Morton Cc: Muchun Song , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Guopeng Zhang , Guopeng Zhang Subject: [PATCH] mm: memcg: stop reclaim when a limit update is superseded Date: Fri, 24 Jul 2026 10:18:05 +0800 Message-Id: <20260724021805.1234583-1-guopeng.zhang@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT From: Guopeng Zhang 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. 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 --- 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. mm/memcontrol.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 8319ad8c5c23..638bdc766616 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -4798,6 +4798,9 @@ static ssize_t memory_high_write(struct kernfs_open_file *of, 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; @@ -4853,6 +4856,9 @@ static ssize_t memory_max_write(struct kernfs_open_file *of, for (;;) { unsigned long nr_pages = page_counter_read(&memcg->memory); + if (max != READ_ONCE(memcg->memory.max)) + break; + if (nr_pages <= max) break; -- 2.25.1