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 95F7EF01833 for ; Fri, 6 Mar 2026 12:21:52 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A60606B0005; Fri, 6 Mar 2026 07:21:51 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 9E3A86B0089; Fri, 6 Mar 2026 07:21:51 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8C5D36B0092; Fri, 6 Mar 2026 07:21:51 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 76BBA6B0005 for ; Fri, 6 Mar 2026 07:21:51 -0500 (EST) Received: from smtpin01.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 1A03A8B97A for ; Fri, 6 Mar 2026 12:21:51 +0000 (UTC) X-FDA: 84515549622.01.BBBD696 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf12.hostedemail.com (Postfix) with ESMTP id 7E33440007 for ; Fri, 6 Mar 2026 12:21:49 +0000 (UTC) Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=h5AYGafZ; spf=pass (imf12.hostedemail.com: domain of ljs@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=ljs@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1772799709; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=gvWN8T/GaYPfHf38YasNEjP7sKLaTw3uFCTUGO6dVU4=; b=G1UHdhRv/+iBoS9cPhHjuoDaRVD+hQ0N6aPtJ2YiOZ1rQz9GHACokt4BuzdpvFbOrufA38 llvcuW5KPJjJn1tZj+nHWaimeNq+FR7lPkwpR9BqFXHucO1LYzCQjIWWi9E6DBTXnJp3f9 aUdRo3PdAM8MHi5TX2kQ30ndOiMb2is= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=h5AYGafZ; spf=pass (imf12.hostedemail.com: domain of ljs@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=ljs@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1772799709; a=rsa-sha256; cv=none; b=varlC/9t1hLNaMSn0yfW1E5a9pnAqdb3aLJXo/kw+MnRdYBE53iR6CR7CFvr394eVKHdGh S+kFpbK8F7IYfojUc4dcqg1xaWLCiKTQvKxY14Q6YLNrja78fJxJFGZra/avDbh7YFK2pL yULGIXfkTLh8/6egp4dkTQl2MwbNMjc= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id C1D5E60018; Fri, 6 Mar 2026 12:21:48 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DC2EEC4CEF7; Fri, 6 Mar 2026 12:21:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772799708; bh=theG/LCt2/q2eE4jZPVvO5dWH6DfzprovWLt+cDnxxE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=h5AYGafZBAupVubVI+ZD7t499uAUfoIBiWhpl8owqkPKw6XrDaEVq2gk6V3VMTbJG I4jRzHR0ZgmZkpNFwz4WPgqzlj/ZTXG8Mkg6mu7rnyphpzPSp0u7fh1+VK9oWLl6gi IDaaFcFprJbRbe9bTzXRL2TSF66F78vemrV5U33fTWh+G/lmL2lf9YKdm5HPHC4unn ZD1xuMdPWyTYHNQLOcZ7Z+EV+KFd74oVVcNcMiIFZxDCm23EI+oRIIIQqgBzscf/du 1PqvIt+BJZaIL/QfENv95huWxRehRctl1ISCOa4xhZ4a1heXH/LVdrvC2Qdmxny09h GIoNXwDaiAUHQ== Date: Fri, 6 Mar 2026 12:21:45 +0000 From: "Lorenzo Stoakes (Oracle)" To: "David Hildenbrand (Arm)" Cc: linux-kernel@vger.kernel.org, "linux-mm @ kvack . org" , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , David Rientjes , Shakeel Butt , "Matthew Wilcox (Oracle)" , Alice Ryhl , Madhavan Srinivasan , Michael Ellerman , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Jarkko Sakkinen , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Greg Kroah-Hartman , Arve =?utf-8?B?SGrDuG5uZXbDpWc=?= , Todd Kjos , Christian Brauner , Carlos Llamas , Ian Abbott , H Hartley Sweeten , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , David Airlie , Simona Vetter , Jason Gunthorpe , Leon Romanovsky , Dimitri Sivanich , Arnd Bergmann , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Peter Zijlstra , Arnaldo Carvalho de Melo , Namhyung Kim , Andy Lutomirski , Vincenzo Frascino , Eric Dumazet , Neal Cardwell , "David S. Miller" , David Ahern , Jakub Kicinski , Paolo Abeni , Miguel Ojeda , linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org, linux-s390@vger.kernel.org, linux-sgx@vger.kernel.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-rdma@vger.kernel.org, bpf@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-fsdevel@vger.kernel.org, netdev@vger.kernel.org, rust-for-linux@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH v1 09/16] mm/memory: convert details->even_cows into details->skip_cows Message-ID: <091ce280-9204-4b85-bf39-5e2a61e3d0ba@lucifer.local> References: <20260227200848.114019-1-david@kernel.org> <20260227200848.114019-10-david@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260227200848.114019-10-david@kernel.org> X-Stat-Signature: bgskfhp3seo6uoob3818pogqdgmkueeu X-Rspamd-Server: rspam09 X-Rspam-User: X-Rspamd-Queue-Id: 7E33440007 X-HE-Tag: 1772799709-249295 X-HE-Meta: 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 DPAP/exQ AxtH5k69OWS2n1AcLvKUlKMAIdLZIP7KCB4oXz4jbqiMlVaLSJIFDNk/X7zxuwUPtA+qFNoQ4VkSlTobKXjZWKlaRsFNE58dTUqiR2DJit+z4gBuf9jeqGGHTkeIXcC0TC6pICa7v51fhr9lAeVzg7E1BgPZ9tBQdTEPj6aT6j66MVzJmqXSOGlC4T+AJLpKcmH1+W+iJ5IhscvmH/+JGfH0N1Q5Bhgm1e5QkfTIwR4UlnoXE+tzivuE8oUNGYwNAY9Mzb33eWqMfRXgYGwAX3Vh4U4EGLx6XL8XLvZkr9dZgIjAS0vFBaI3CPeGCMjtbSZSL Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Feb 27, 2026 at 09:08:40PM +0100, David Hildenbrand (Arm) wrote: > The current semantics are confusing: simply because someone specifies an > empty zap_detail struct suddenly makes should_zap_cows() behave > differently. The default should be to also zap CoW'ed anonymous pages. > > Really only unmap_mapping_pages() and friends want to skip zapping of > these anon folios. > > So let's invert the meaning; turn the confusing "reclaim_pt" check that > overrides other properties in should_zap_cows() into a safety check. > > Note that the only caller that sets reclaim_pt=true is > madvise_dontneed_single_vma(), which wants to zap any pages. > > Signed-off-by: David Hildenbrand (Arm) This is another nice change. I have some tweak suggestions below, but past experience suggests to me it's quite possible you do what I ask in subsequent patches, will see :) Anyway overall LGTM, so: Reviewed-by: Lorenzo Stoakes (Oracle) > --- > include/linux/mm.h | 2 +- > mm/madvise.c | 1 - > mm/memory.c | 12 ++++++------ > 3 files changed, 7 insertions(+), 8 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index d3ef586ee1c0..21b67c203e62 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -2798,7 +2798,7 @@ extern void pagefault_out_of_memory(void); > */ > struct zap_details { > struct folio *single_folio; /* Locked folio to be unmapped */ > - bool even_cows; /* Zap COWed private pages too? */ > + bool skip_cows; /* Do not zap COWed private pages */ > bool reclaim_pt; /* Need reclaim page tables? */ > zap_flags_t zap_flags; /* Extra flags for zapping */ > }; > diff --git a/mm/madvise.c b/mm/madvise.c > index 557a360f7919..b51f216934f3 100644 > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -853,7 +853,6 @@ static long madvise_dontneed_single_vma(struct madvise_behavior *madv_behavior) > struct madvise_behavior_range *range = &madv_behavior->range; > struct zap_details details = { > .reclaim_pt = true, > - .even_cows = true, > }; > > zap_page_range_single_batched( > diff --git a/mm/memory.c b/mm/memory.c > index fdcd2abf29c2..7d7c24c6917c 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -1554,11 +1554,13 @@ copy_page_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma) > static inline bool should_zap_cows(struct zap_details *details) Not sure if you fix up later, but we should probably change this function to should_skip_cows() to keep everything consistent, otherwise this is a bit weird and confusing. > { > /* By default, zap all pages */ > - if (!details || details->reclaim_pt) > + if (!details) > return true; > > + VM_WARN_ON_ONCE(details->skip_cows && details->reclaim_pt); > + > /* Or, we zap COWed pages only if the caller wants to */ > - return details->even_cows; > + return !details->skip_cows; > } > > /* Decides whether we should zap this folio with the folio pointer specified */ > @@ -2149,8 +2151,6 @@ void unmap_vmas(struct mmu_gather *tlb, struct unmap_desc *unmap) > struct mmu_notifier_range range; > struct zap_details details = { > .zap_flags = ZAP_FLAG_DROP_MARKER | ZAP_FLAG_UNMAP, > - /* Careful - we need to zap private pages too! */ > - .even_cows = true, > }; > > vma = unmap->first; > @@ -4282,7 +4282,7 @@ void unmap_mapping_folio(struct folio *folio) > first_index = folio->index; > last_index = folio_next_index(folio) - 1; > > - details.even_cows = false; > + details.skip_cows = true; > details.single_folio = folio; > details.zap_flags = ZAP_FLAG_DROP_MARKER; > > @@ -4312,7 +4312,7 @@ void unmap_mapping_pages(struct address_space *mapping, pgoff_t start, > pgoff_t first_index = start; > pgoff_t last_index = start + nr - 1; > > - details.even_cows = even_cows; > + details.skip_cows = !even_cows; Not sure if you clean up later, but seems sensible to cascade the change into the local boolean here. > if (last_index < first_index) > last_index = ULONG_MAX; > > -- > 2.43.0 >