From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 782D5C61DCB for ; Fri, 28 Aug 2026 15:07:52 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 581D96B0088; Fri, 28 Aug 2026 11:07:51 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 50C1F6B008A; Fri, 28 Aug 2026 11:07:51 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3AC2A6B008C; Fri, 28 Aug 2026 11:07:51 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 134316B0088 for ; Fri, 28 Aug 2026 11:07:51 -0400 (EDT) Received: from smtpin28.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 85DB31603DA for ; Fri, 28 Aug 2026 15:07:50 +0000 (UTC) X-FDA: 85151007900.28.6A267B7 Received: from mx0b-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) by imf17.hostedemail.com (Postfix) with ESMTP id 0155F40008 for ; Fri, 28 Aug 2026 15:07:47 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=ibm.com header.s=pp1 header.b=cVQ6kEee; dmarc=pass (policy=none) header.from=ibm.com; spf=pass (imf17.hostedemail.com: domain of imbrenda@linux.ibm.com designates 148.163.158.5 as permitted sender) smtp.mailfrom=imbrenda@linux.ibm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1787929668; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=R2ReIfcU6q09mU3umuATDMJX0HzmPeiVXkiDg/a3WZ0=; b=dNX7UUyUEPnq/dOiObqYd3nT1QSXq5N48lV+d0kRjCiAahj50Tp9yDvb2lNmo5yDiiq3IQ uQEb886bdTOARuu34h5OKwY4wP3QAHmmZYBNVHzCjAs3xL2bFaI+Zd0kim9UiNJm6uGSmy w/1wLkgdebp+Zoj/FBUUkq+OE0f48CY= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=ibm.com header.s=pp1 header.b=cVQ6kEee; dmarc=pass (policy=none) header.from=ibm.com; spf=pass (imf17.hostedemail.com: domain of imbrenda@linux.ibm.com designates 148.163.158.5 as permitted sender) smtp.mailfrom=imbrenda@linux.ibm.com ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1787929668; b=W1sD9yaWUQ7/zgR1k74Hs0iEfrIn/KtpqOeIQFcM756usqZf6LaD+sdo7EIeFj7C6mruXO 8zE5Lz8MJVfH9Nb6kxMjRd+zw/PdC5KwwaJzgAJTOL2aZQTU7Ds4i6OTjGLe7u6ZAdqKth Hgv+DIpah+K9klpypVFE1lNps+xZCI4= Received: from pps.filterd (m0360072.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.18.1.11/8.18.1.11) with ESMTP id 67SDVgsu2186259; Fri, 28 Aug 2026 15:02:23 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=cc :content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to; s=pp1; bh=R2ReIf cU6q09mU3umuATDMJX0HzmPeiVXkiDg/a3WZ0=; b=cVQ6kEeeIOBZIof5NJlQup ylyV/I1zq0HtB5g6HlEIjL3uqD0k1SbkZ2e4sqztn2MOZqxPYrDZRqlsqF+aHzIt k/FfJkqgrkyYNvpM6+23MBXi7QfwidYK0jynJxvuMQCv9vMMeFnJH+hYoq0b2CS/ 3HZO63xQNFrF9UiE+le8kygr//DrJGZN5QszhHZ9lu0eOwz4+MIKwgDR/cImP2g6 FFcLF+UKgAz/DfwcqxC9jKw+pme/G3Kx03KAbHCmgS8EKBEmd9yvnGttbR45TjrF umlVhg6AdVlHo96/zr40P3V65wc7z65Q8113Zx5GaX8HZiAl6wPOqnQAXEJM+pOw == Received: from ppma12.dal12v.mail.ibm.com (dc.9e.1632.ip4.static.sl-reverse.com [50.22.158.220]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 4g73dxvpvv-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 28 Aug 2026 15:02:22 +0000 (GMT) Received: from pps.filterd (ppma12.dal12v.mail.ibm.com [127.0.0.1]) by ppma12.dal12v.mail.ibm.com (8.18.1.7/8.18.1.7) with ESMTP id 67SEuQUI021766; Fri, 28 Aug 2026 15:02:21 GMT Received: from smtprelay01.fra02v.mail.ibm.com ([9.218.2.227]) by ppma12.dal12v.mail.ibm.com (PPS) with ESMTPS id 4g7p3qq5xb-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 28 Aug 2026 15:02:21 +0000 (GMT) Received: from smtpav05.fra02v.mail.ibm.com (smtpav05.fra02v.mail.ibm.com [10.20.54.104]) by smtprelay01.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 67SF2J3G32899538 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 28 Aug 2026 15:02:19 GMT Received: from smtpav05.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A081620043; Fri, 28 Aug 2026 15:02:19 +0000 (GMT) Received: from smtpav05.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 15F3520040; Fri, 28 Aug 2026 15:02:19 +0000 (GMT) Received: from p-imbrenda (unknown [9.224.75.30]) by smtpav05.fra02v.mail.ibm.com (Postfix) with SMTP; Fri, 28 Aug 2026 15:02:19 +0000 (GMT) Date: Fri, 28 Aug 2026 17:02:17 +0200 From: Claudio Imbrenda To: Hugh Dickins Cc: Andrew Morton , Ackerley Tng , Alexander Viro , Baolin Wang , Barry Song , Binbin Wu , Christian Brauner , Christoph Hellwig , Christoph Lameter , David Hildenbrand , JP Kobryn , Jan Kara , Jens Axboe , Johannes Weiner , Kairui Song , Kiryl Shutsemau , Lance Yang , Leonardo Bras , Lorenzo Stoakes , Marcelo Tosatti , Matthew Wilcox , Mel Gorman , Miaohe Lin , Michal Hocko , Minchan Kim , Muchun Song , Oscar Salvador , Peter Zijlstra , Qi Zheng , Rik van Riel , Sebastian Andrzej Siewior , Shakeel Butt , Suren Baghdasaryan , Vlastimil Babka , Yang Shi , Yu Zhao , "Zach O'Keefe" , Zi Yan , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 20/25] s390/fbatch: no lru_add_drain_all() in s390_wiggle_split_folio() Message-ID: <20260828170217.324c3445@p-imbrenda> In-Reply-To: References: <14a16945-529b-8bc0-ab38-3ea97e54e223@google.com> <7bf68e7b-f88c-6ca9-39ab-e9fedab0c8be@google.com> <20260826155722.0198d3ce@p-imbrenda> <2319f670-fe0b-f032-c0dc-486cbec0f3e1@google.com> <20260827145502.2fb4505b@p-imbrenda> Organization: IBM X-Mailer: Claws Mail 4.4.0 (GTK 3.24.52; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Info: AW1haW4tMjYwODI4MDEzMCBTYWx0ZWRfXxHuti5Dj527N FiuJvw5RRjbYYN3JC15bUZTx+KDTxKTF+YzVq/ezrl4g++dGepSXXGaZVPkOm4cymppJdcuSX9P xHXurASEMTrGs5t4EgR5ewb+tDvOJx0= X-Authority-Analysis: v=2.4 cv=AYuB2XXG c=1 sm=1 tr=0 ts=6a91a2ff cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=kj9zAlcOel0A:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=1XWaLZrsAAAA:8 a=fg8ePjUzgZY9LUZ9XEsA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-ORIG-GUID: FQUAcCuNRcSdPaHF-8xMvR4ns_OVsTxc X-Proofpoint-GUID: tqGOyE4oqLz6WkdSLX2ygEk1_1IVTp04 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODI4MDEzMCBTYWx0ZWRfXxRCLSM+4Biti Tjs1pSPmVVcJoKO+z3p0Dt1SG8YQgEPKpDMcG/eaCrZOoFaJ9AFvVCkax+818IAsE8Uegm/xMgc 0/cwTHHY1YoT+gHc2fQNCwnZjlqu8AMiNWqlapdmKpzZAI7HmUo9CZmuCr4hKdlqp73EVEnoMQy pNu+pSs1Oh5o5El/K5kbtrI3W1AkYZed0rHnRnt0tO0sNPiWOCoAByfFwGIAsvi7TeogT7IPnrz rEK5ADmyOmerpw33FysddOMskKC+kTa4RWJPGyi68ppeQBBFXXcl18hqGrkc6lRFa6ihlHhCE4q 7IxqQuA/dq4h5+4ff08OmadKB3LkyhDSwC/7Tn9F+zXd6tMPaZiCnf6QPDmTqZeiYwun+8DLvlg fVFgNWQR+c2vPwMIpleETyofoCHhb4yzDx9NL7ik/gqTM/j2gQVlp7eELE7d2jk5a3NuP1eA1X7 H+giiQLr8LQcrtD41UA== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-28_04,2026-08-27_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 phishscore=0 clxscore=1015 adultscore=0 bulkscore=0 impostorscore=0 priorityscore=1501 lowpriorityscore=0 spamscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608280130 X-Stat-Signature: my8s3zfq7o5pqtpe3af75pgs8wsrbo48 X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 0155F40008 X-Rspam-User: X-HE-Tag: 1787929667-665644 X-HE-Meta: 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 x5JYtufg KS3ickWUhtX8BYY3F6kw5owC9eP3jn39F/45DvZ8gUs5bVL3fxM8GKv14NGx5bWyU18w/7tOR9g1+SwEsLaQNbFQGXyccnXZQu7yVBHNv1RxB0rL2sNv9Ijhh5sxDSyQPaVM6MnboW68e+BkDH3Qfdc+9JxYl1hLWbIDwmUjowW1bVz72XradehrZqki8ohnKs3aSabR6nngNrCLyhbtAnMlu00TIPWcq74gzDjv5IJlpHzb22/xsosukYFXjBphFoIWbZa4D9yJjuPcFn+na2nTvyKvX84834hLOWygGzDdbzYJsEZf69ulJiNjD0A+OLkaymTOIngagGQF/X2Cgk0u0LLgb3njS9v515sAQLz/lx5qmukcps2tJBwl/OtwXux5yL7dwKDiR2kMK/2AMdnfZ+lAc6Dh4G6a9wzks8y7/L2A8tywHbiSybDMH3X5nUCh+KZucD5fLXTk= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 28 Aug 2026 01:57:25 -0700 (PDT) Hugh Dickins wrote: > On Thu, 27 Aug 2026, Claudio Imbrenda wrote: > > On Thu, 27 Aug 2026 01:49:12 -0700 (PDT) > > Hugh Dickins wrote: > ... > > > > > > I most certanly don't know s390 or that code well enough to guarantee > > > you that no stray references to mapped folios can remain there. What I > > > can guarantee is that no references, of the kind which lru_add_drain_all() > > > used to be needed to remove, can exist there: so there will no longer > > > be any point in s390 (or others) calling it for that reason, to help > > > split_folio() to succeed. > > > > we are not using it to help split_folio() succeed (although that's a > > pleasant side effect). We need it even for small pages, to guarantee > > that no extra reference from LRU is present on the page. > > Ah, thanks for explaining, that all makes more sense to me now. > I remember from when working on memfd write sealing years ago, it too yep, we use it to make sure no I/O is happening on the page while it's transitioning > had to be able to account for every page reference before proceeding, > and resorted to lru_add_drain() and lru_add_drain_all() to help - > those now removed in 14/25 of this series. I see, then I guess we're good (see below) > > ... > > > If Barry's relaxation goes in before my drainage changes, then > > > there is value in that s390 lru_add_drain_all() in the interim. > > > > hmmm so, should it stay for now, then? > > The s390 lru_add_drain_all() should go whenever the rest of this > series goes in. It's not essential for the callers to be removed > immediately, no correctness requirement; but nicer if we can get > rid of most of them. I'm hoping this patch can just go in along > with the rest via the mm tree - and I'm sure you can trust David > Hildenbrand to understand and protect s390's interests. so if I understand correctly, with this series the LRU caches will never hold extra references (as in refcount) on pages anymore, therefore calling lru_add_drain_all() will never decrease the refcount on any of the pages that are in any of the LRU caches in that case the lru drain can indeed go > > > > > also: I'm working on completely reworking how the transition from > > non-secure to secure is handled, with the explicit goal of getting rid > > of that kludge we are currently using. That will also get rid of the > > lru drain. But it will take some time (I hope to have something by the > > end of the year) > > Good luck! > Hugh