From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-dy1-f201.google.com (mail-dy1-f201.google.com [74.125.82.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CCBAD1A6812 for ; Sun, 22 Mar 2026 07:08:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.82.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774163329; cv=none; b=nP03KjerEGvwzrZ4jPVkiW3ry9ALcMQSWHb4yLHWJhAYQvZboQw0i1BdDbOTlPNxYIGKUjOpMpEvfxGpWFiQtd++gJApjt/i1nsRmIfmVaWzX1zeTci/Hfzj1pa9kdSZhF74O30NH6he1AW4hKrPUHgikRpjXxz2XPXpDbyEVkQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774163329; c=relaxed/simple; bh=LRk+Q6oLc4v5ya3Goo6k0Z0pZXgviyqypQPY0+7Dho8=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=FKVrjogiBxEbKZ04R+yWi8FdBCjcXfDcCnwpllYYS0PvUxRax2oJw7OSuO1FKNiHYW9HP8A+K6w2uzdaQt3m+/x0JNN51xacF3RQdt2sDZU6nKeEvkPW3S6lDwibuKD6i0dNaNlocorzN5hS4xDWL+aVmfg8BbqpnPx61U2Stew= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--surenb.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=TnH+RmLW; arc=none smtp.client-ip=74.125.82.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--surenb.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="TnH+RmLW" Received: by mail-dy1-f201.google.com with SMTP id 5a478bee46e88-2ba8013a9e3so2566091eec.0 for ; Sun, 22 Mar 2026 00:08:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1774163327; x=1774768127; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=bUUcI+G547AnXOqEoU0HumPgtMUcHYFJWOSvPIWQmuo=; b=TnH+RmLWqXustNGA6oVvTol3gbawTAdcLByVmgU7RlsAnOya3OXDV0e3NWm2uywY5z UsU4jnEtcfhUmr/dhZOKQ3KJBEIQBBNC8fQC0C3eZWSY6sfLJELC6ZNMN6ztvuP/VKAV +3bDXIdxrv3LiOt1ZmubwvI+PgypmG/L2mQXXEAHpBX7mFX5GloB/ez6RvNdmi61e/YS ygy2ZFPfbXI6x17KIDDT9f716dYIDg2dYlNLDDTk1rW2gIg7MHJD8J7ZFevuHXp/p+Wq Wb8CgHcybAUHwcwTLFKRnsZceRIW46lHNBPvZ2Ur35HsJMdXY4plaomJKNQPOu6DO5Qh R8mw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1774163327; x=1774768127; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=bUUcI+G547AnXOqEoU0HumPgtMUcHYFJWOSvPIWQmuo=; b=kiacFvqsc9cP+yMSrSkQXBb8+iQgo18Q2jaU3vBA7CciATqXeWtDRby7OiLPVj8PBY wkNZiAQTMZ7COZpkp9nUpexwurfkESdxCTAgVfryCUJ3yKJiZ5+q2uTECpJF7q5zq9PR XItgepeYoA9HzP9NITeeorUQXiu1IiCzWu4f5RgqJgel3XheaH/e0yQipmXRMhzO4cjg 03Y1BeKClk5lxxQeTIzwAJzoEpWuOD9MmcVUrf0WmqOcIeqEouPm6oDsqk8kSJ+zRTm+ r3D1lPN6yO6HMp/Y8kRW6GRt6MRyauJwTHN1mfZGa89Y75SrPaufwKXgTawgbkx3isAk WbaQ== X-Forwarded-Encrypted: i=1; AJvYcCUOC+vQD9fkinmgkW10AkTch5LURQqj+GQAybN0CJKZ2bKK+i7wpVONn9VO0vPfHpUttxuvZsdD6uHLKcg=@vger.kernel.org X-Gm-Message-State: AOJu0Yybk+R111lsTD7x/4Wz02POEwgD/V/Vb3C0xQBbn1OBSQQ1cbKD UxwZsMEtkLp8gTtvSBJPvTYNFeNGGv3qUSkOGG0xVdxal2FvqzlkbpmOkSFVjbVFAaIHyLCYNVL +d7N0bQ== X-Received: from dybme4.prod.google.com ([2002:a05:7301:1884:b0:2c1:264d:62f]) (user=surenb job=prod-delivery.src-stubby-dispatcher) by 2002:a05:7300:6dac:b0:2ba:6854:8d4d with SMTP id 5a478bee46e88-2c109752e05mr4064629eec.20.1774163326701; Sun, 22 Mar 2026 00:08:46 -0700 (PDT) Date: Sun, 22 Mar 2026 00:08:43 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.53.0.1018.g2bb0e51243-goog Message-ID: <20260322070843.941997-1-surenb@google.com> Subject: [PATCH 1/1] mm/vmscan: prevent MGLRU reclaim from pinning address space From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: hannes@cmpxchg.org, david@kernel.org, mhocko@kernel.org, zhengqi.arch@bytedance.com, yuzhao@google.com, shakeel.butt@linux.dev, willy@infradead.org, Liam.Howlett@oracle.com, ljs@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Suren Baghdasaryan Content-Type: text/plain; charset="UTF-8" When shrinking lruvec, MGLRU pins address space before walking it. This is excessive since all it needs for walking the page range is a stable mm_struct to be able to take and release mmap_read_lock and a stable mm->mm_mt tree to walk. This address space pinning results in delays when releasing the memory of a dying process. This also prevents mm reapers (both in-kernel oom-reaper and userspace process_mrelease()) from doing their job during MGLRU scan because they check task_will_free_mem() which will yield negative result due to the elevated mm->mm_users. Replace unnecessary address space pinning with mm_struct pinning by replacing mmget/mmput with mmgrab/mmdrop calls. mm_mt is contained within mm_struct itself, therefore it won't be freed as long as mm_struct is stable and it won't change during the walk because mmap_read_lock is being held. Fixes: bd74fdaea146 ("mm: multi-gen LRU: support page table walks") Signed-off-by: Suren Baghdasaryan --- mm/vmscan.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 33287ba4a500..68e8e90e38f5 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2863,8 +2863,9 @@ static struct mm_struct *get_next_mm(struct lru_gen_mm_walk *walk) return NULL; clear_bit(key, &mm->lru_gen.bitmap); + mmgrab(mm); - return mmget_not_zero(mm) ? mm : NULL; + return mm; } void lru_gen_add_mm(struct mm_struct *mm) @@ -3064,7 +3065,7 @@ static bool iterate_mm_list(struct lru_gen_mm_walk *walk, struct mm_struct **ite reset_bloom_filter(mm_state, walk->seq + 1); if (*iter) - mmput_async(*iter); + mmdrop(*iter); *iter = mm; base-commit: 8c65073d94c8b7cc3170de31af38edc9f5d96f0e -- 2.53.0.1018.g2bb0e51243-goog