From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=209.85.221.53 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793958978; b=DyCjs4+9JCQ5+QParvMt6wp5XFIkmWVRMrnykDCWg0sbgYqFfxvs1vFo3JgZC4EROqMQ evD/j5zGO/Z83e3JMDdJSgPBN/YvIiLgJ05Pgs7kCEI8f3ik3gEHHk3zMqmZn3pxm0M63 NL2looSLRVXYvp30KH3RcO/tX5RK+S+9GqnCmyj236p33a2+QIO3X+3h6s63YKoB6A3wy mdlxc52NpkmEHYNrlv6G8Nw28bUNSMMSHr+Hf7Lf8/tojNIYhYNPKgbXs6Ul4dvA12VH2 2X8PmqAeok6PCsACAj6opPkoSz48aeqPNl5nk2AEQPUyKeFwPpcSCDnjLhTcEr9+0TA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793958978; h=DMARC-Filter:Received:DKIM-Signature:X-Google-DKIM-Signature: X-Forwarded-Encrypted:X-Gm-Message-State:X-Gm-Gg:X-Received:Received: Message-ID:Date:MIME-Version:User-Agent:Subject:To:Cc:References: Content-Language:From:In-Reply-To:Content-Type: Content-Transfer-Encoding; bh=PVNqNcKixHGsvQRk+aF9Z3pXurarEsFSJxJzB1XGyf0=; b=IP4PbNLlH52oAp05y+rgqlnQ1a6tVUxuQUr0TbtYwdFudMI0Gx8kmlKCEUMRqIbUAeXT yMc4OzQegXTgwPF1ypZGd/j0b9xShCfL40VzVjrbwx+YTNHe78py1dsYGRvHTqg2ZAXde A5R0AN6ssVUrJ6Jkn+BdSxpSptN0y6eepgTdyFzb9IUf+1qqyqPyF2clszFvrdg/ORu8s GbgdOe1i7DtG0T+07cQRaiTL+QMpKL9qNZS5Ak5atxVBU1NQMtFCv7yQGmIqCLZ5mseXN txGz55ica6NaKgoJh/bjsS7aRbh3tYOTbxrBzvq/97k6shjgNNV7iT94MVVOoHKsiBA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20260707 header.b=H1Xmkiwr; arc=none smtp.remote-ip=209.85.221.53 Received: from mail-wr1-f53.google.com (mail-wr1-f53.google.com [209.85.221.53]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 585B6606A326 for ; Fri, 6 Nov 2026 09:56:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 585B6606A326 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20260707 header.b=H1Xmkiwr Received: by mail-wr1-f53.google.com with SMTP id ffacd0b85a97d-49376eb635fso41573f8f.1 for ; Fri, 06 Nov 2026 01:56:17 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20260707; t=1793958976; x=1794563776; darn=vger.kernel.org; h=content-transfer-encoding:content-type:in-reply-to:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:from:to:cc:subject:date:message-id:reply-to :content-type; bh=PVNqNcKixHGsvQRk+aF9Z3pXurarEsFSJxJzB1XGyf0=; b=H1XmkiwrX3YLzUoz8v63tW0K3f8HeQQMrYHC6NguBq0Yc1lHgV5BxOaPiQVM/nx5Kr Nv4Nkr/P+0smDYStmA0vxUWIevexJO6W3YeVFzXWxjpUb82YtyB7exO1WkMPRlrqshbw 7gdELKEwKXzXZnlrkpHr1yD7exsMl5g9kqsHjwkVOrYoszaDhxn1MLxcOJF4sb/6L3MY sIdWD7L/keA+kAzxJc8rrEhKaeUKb4K3OJKzQ0cL4yoRHek+Sk1AtTQV2X8+u59Vj8dP k4wPQ0+F+f6g4v8Op0nmFGDXNrToQHYaCL+7LHoyjFE/RK0fmcwPf6Waptypct15sbUF jOcw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1793958976; x=1794563776; h=content-transfer-encoding:content-type:in-reply-to:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=PVNqNcKixHGsvQRk+aF9Z3pXurarEsFSJxJzB1XGyf0=; b=Ce6cKrBiWc3TW5SpVSih1+KuY3vHG5KUUvCbSoHm/HmkG0ylUCkcnodi18zT8jH+nz gEBcHA7MIVeAII9gaSmtY+5BB02fVI/wvyjqKKQ2hEw2RGk/qwYLCj8/a0t2AzrGmHnC hQMoGoPWj48bPOUtlb5PlM8+iKK/YfHZI0Ug0G6wWkaabsiD6EPxyaJDgBce7syGc2z0 JNq8HS2pXCM0hNAGQlZYoQZsCvGLO78C7FZYlK0ewvapJCzCcruK9Q/xV+Hs5SjoUaNv 6Y7v3/Erb2Pu8iutJ1b3pRcwXNyOUUY66ahQN5dMqyKsMVdoJ6eIXz5zFSa1mF3sCO5T L8MQ== X-Forwarded-Encrypted: i=1; AL+hErHH0YG2nWEI/iOseGs8Uyg+egITGMtyo2gXwHmKAnEtoKqGT2PfEpjstyDcBRO5FAQxon4aQASRCJtuKQQT@vger.kernel.org X-Gm-Message-State: APuU4Z9J+w5SnyLz9V6i4LAesU8nedG7Z6gq7RorV1VekIG9jK6IODwx QmcZDPOXqqtr268b32yvo7SgrxI4dW5ZAVZ6HcrSW4t32WIWFHNwdad8 X-Gm-Gg: AYBFou1FdYo5YTnZ8snTrumsZAj1RVueSl81xDv2qQdZkEX2bkwyJRTgmM2Qss3Aw3t SKGZ1exI1D7Hvlp5dp43dTu2X89LnBd3W/EooKi5NY7S5+IQCR1wyLLhET08KVK8+fVptPXU0Q/ XfNkPbPOVNPIRpeHR6Pm7llO6XmFt95VD/rwuLIBNTbTVDxEtPCl1w4bJ6YJ2Ju6BiSa53VFdTd z92z3Dw+3+Vg5QLPY7CEuJVy29nxcrtsV7s238TA3L+SacuSrsPfbyOeSq66h5frFn/tR1zuN50 dsic1H/yrRkdYzYdr48f5ZR9no/xQLSSziwx630z/+gapepV+iubdZbEwNo8X8uKSnGtWvt9R5c MW/rPtfRBoQ0w2HbZrf2EqIotSRTohB9kQ8hjbJwk8Vfo6SSWO6BkWKUGAvX3dISOVlTTtnE5wa MI+ijuRxr2BGVv7KVDCkKuW+YKiKXFI+X8Ze8EXGJrjH9iAGqVr3Tqw1WmgkQYqws/grokWIMgu /maZPZ8sE3jg1G8QYRDJA/A4rZG7Y9knPVWYylJVIWUFJHbDNM2htcZzl4yFfGNqlDqX0MusQRP D69BwDw53vO4BqwU4jLK2LA= X-Received: by 2002:a05:6000:26d3:b0:48e:6159:8274 with SMTP id ffacd0b85a97d-492765a3e9emr3874962f8f.27.1793958975594; Fri, 06 Nov 2026 01:56:15 -0800 (PST) Received: from [192.168.1.22] ([83.231.69.9]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-492d7dbb0d4sm2752385f8f.50.2026.11.06.01.56.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 06 Nov 2026 01:56:15 -0800 (PST) Message-ID: Date: Fri, 6 Nov 2026 10:56:11 +0100 X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 3/5] mm/mmu_gather: flush pending references early before the folio limit To: "David Hildenbrand (Arm)" , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kiryl Shutsemau , Matthew Brost , Joshua Hahn , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Peter Xu , Johannes Weiner , Song Liu , Rik van Riel , Hugh Dickins , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Peter Zijlstra , Jason Gunthorpe , Kevin Tian , "Joerg Roedel (AMD)" , Robin Murphy , Steve Sistare , John Hubbard Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, iommu@lists.linux.dev, Chris Mason , stable@vger.kernel.org References: <20261105-refcount_overflow_stable-v1-0-70b9c655da3e@kernel.org> <20261105-refcount_overflow_stable-v1-3-70b9c655da3e@kernel.org> Content-Language: en-US From: "Jose A. Perez de Azpillaga" In-Reply-To: <20261105-refcount_overflow_stable-v1-3-70b9c655da3e@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/5/26 2:10 PM, David Hildenbrand (Arm) wrote: > When a task zaps mappings (e.g., MADV_DONTNEED), it can drop the PT lock > and defer dropping the folio references. In the meantime, page faults > can refault pagecache folios, creating more references for the same > folios. > > Let's just request a flush after enqueueing a pagecache folio whose > refcount reached a certain threshold. Start flushing well before new > references are refused, regardless of the caller's privileges. > > This is a temporary measure until we have something better. > > Reported-by: Chris Mason > Fixes: 10ebac4f95e7 ("mm/memory: optimize unmap/zap with PTE-mapped THP") > Cc: stable@vger.kernel.org > Signed-off-by: David Hildenbrand (Arm) LGTM: Reviewed-by: Jose A. Perez de Azpillaga -- cheers, jose a. p-a