From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 4783B39D6E9; Wed, 15 Jul 2026 14:57:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784127476; cv=none; b=ezKn9ycCxpYyt+tM/i1lr+81ciDbVRQw4XZ1dYUwdpAO5YxHFYn2Ppj0DZukCQrZjWyEwQ2iJoJpxK3342T4YGc+1gUTkMmTm4o3QvjQn/2z8ipfK6/Z5GEO4jqgfsGZJbXJb3GIJsUTkzgqmPR+3XxHKGDZhT6Ewb4fANIhxOM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784127476; c=relaxed/simple; bh=wfmC2sNj69fJIVZiqqNs4Of94KPQNh/mvTnPV3EfsZ0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=cvsgCZ/PqBmEDi0lhEtL8RFCeyz9fode3IGtLkLW8utmQZtKD4XYg0PPtUu9cxFP+DXR2tMJX5timgrZ2xZmho2oFsMALHMulLC7J4fcjMet/IBatt81pkP2yJWEgp5eZIsNcqK2SU3PxO/PQ/zYCdHnXA0BtYIlM1mvsGrw3sg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=cPH7HtDg; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="cPH7HtDg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1EA301F000E9; Wed, 15 Jul 2026 14:57:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784127474; bh=z+WsmMVZ0fijyeATWav3FVb2hBbQqIKn5lxc8dFuRgY=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=cPH7HtDgs6cyYjA7uPw3ObONQWW0lg1fg4SZgc3/CVufpkG9c0IVzYYGe9hXpJnBM EciYHh3CSE7MsJrRxFvgeaYvVVnyILFYrvi/K/lkgNkbDtTyzGT9fTt8evuEFCYNKJ /6Q1cuzJWTgyEGbjV+4NTGMIIJQCdHaCzseCZF6+XN/OuEWTRyQp0SKjbilU0YyYVI KJtH/kE43WeJygbG8X1i1uYX0DFToUTqRXR85bojPJPv5c5DdI0FMc6v6EjYbL3/yj qOBAJ6EwOOA7jl4ITRmK6tGfFqVRS+PJHWo5bm2GfnQezZhI9NSeNqI7I+FBExuksu LjiPFApKHUjLA== Message-ID: <67242b7a-d913-48f0-a2fd-56709e474b55@kernel.org> Date: Wed, 15 Jul 2026 16:57:29 +0200 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 17/33] mm: introduce and use linear_page_delta() Content-Language: en-US To: Lorenzo Stoakes , Andrew Morton , David Hildenbrand , "Liam R. Howlett" , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Rik van Riel , Harry Yoo , Jann Horn , Lance Yang , Pedro Falcato , Russell King , Dinh Nguyen , Simon Schuster , "James E.J. Bottomley" , Helge Deller , Alexander Viro , Christian Brauner , Jan Kara , Dan Williams , Matthew Wilcox , Muchun Song , Oscar Salvador , Masami Hiramatsu , Oleg Nesterov , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , James Clark , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Miaohe Lin , Naoya Horiguchi , Xu Xin , Chengming Zhou , SJ Park , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Hugh Dickins , Peter Xu , Kees Cook , Marek Szyprowski , Robin Murphy , Andrey Konovalov , Alexander Potapenko , Dmitry Vyukov , Steven Rostedt , Mathieu Desnoyers , Jarkko Sakkinen , Dave Hansen , Thomas Gleixner , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , Ian Abbott , H Hartley Sweeten , Lucas Stach , Christian Gmeiner , David Airlie , Simona Vetter , Patrik Jakobsson , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Rob Clark , Dmitry Baryshkov , Abhinav Kumar , Jessica Zhang , Sean Paul , Marijn Suijten , Tomi Valkeinen , Thierry Reding , Mikko Perttunen , Jonathan Hunter , Christian Koenig , Huang Rui , Matthew Auld , Jason Gunthorpe , Yishai Hadas , Shameer Kolothum , Kevin Tian , Ankit Agrawal , Alex Williamson , Paolo Bonzini , Shakeel Butt , Usama Arif Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-parisc@vger.kernel.org, linux-fsdevel@vger.kernel.org, nvdimm@lists.linux.dev, linux-perf-users@vger.kernel.org, linux-trace-kernel@vger.kernel.org, damon@lists.linux.dev, iommu@lists.linux.dev, kasan-dev@googlegroups.com, linux-sgx@vger.kernel.org, etnaviv@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-arm-msm@vger.kernel.org, freedreno@lists.freedesktop.org, linux-tegra@vger.kernel.org, kvm@vger.kernel.org, Russell King , Ackerley Tng References: <20260710-b4-pre-scalable-cow-v2-0-2a5aa403d977@kernel.org> <20260710-b4-pre-scalable-cow-v2-17-2a5aa403d977@kernel.org> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSNWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBrZXJuZWwub3JnPsLBsAQTAQoAWhYhBKlA1DSZLC6OmRA9UCJPp+fM gqZkBQJqFFy6GxSAAAAAAAQADm1hbnUyLDIuNSsxLjEyLDIsMgIbAwUJGtCBUAULCQgHAwUV CgkICwUWAgMBAAIeBQIXgAAKCRAiT6fnzIKmZJIUEADFx/tREzUImHrEwVHeSvDFmA7tJysI UVrlvrM09E7GIuzphzv7jYmo8n3ANpCczLEVr4G0syYQdTigaZgv3+FQDIIzhKih1IHhu1Ei XHlywNWKnQxxQEUNi5Mwx43wQz5XVw9F1A7gtKBKNtfogO511hAbrzagrYajyQacEJ/+sfhZ 9Da8ltHIXD8pcYaHUfQgEusCgmEd9+KrUwrTbckFKmYq5chuE6yJ4J0EmWknL096jIE6CnzF FRslQ3B1UKDjxVsm1ZHfir5NeWszLkTvGFsddFaWTgh8UycESG6VQzKXjjewXu2pG7YQYRpj QKm1W5X2TkwWkXRBZTmfmbhxIUMh3+zf5wQ463rSmDN/8v81tdqBtAW6rH/kzg1GvkaTHXn0 507yEHFzBksk2viAuIxxr7km8+/KARYLIdGtx30EG8cKzAUZOK6WqxtNCsXUJNrVE8CWrCaD icoNu7Fs1c5hmPHdSTnU48ce67449DdnO4neLSNhRiGlMHJgfJUmgrxu/hcYeOZ3haWmEQ2w uW1Mh01OHi8QZHCEyAbABrPs9GUgccc/4eYXX9hIgxfSkYzn8f+8NuIFPWl/0uTvjgqU29FQ SbzOLxHq9439Ox40G5mS5eZXRGxITYR+6TXvRGI6P/264jvflnr/pDGUttaikU+0W+1uxgKH cmYbEc7ATQRbGTU1AQgAn0H6UrFiWcovkh6EXVcl+SeqyO6JHOPm+e9Wu0Vw+VIUvXZVUVVQ La1PQDUi6j00ChlcR66g9/V0sPIcSutacPKfdKYOBvzd4rlhL8rfrdEsQw5ApZxrA8kYZVMh FmBRKAa6wos25moTlMKpCWzTH84+WO5+ziCTsTUZASAToz3RdunTD+vQcHj0GqNTPAHK63sf bAB2I0BslZkXkY1RLb/YhuA6E7JyEd2pilZOrIuBGl/5q2qSakgnAVFWFBR/DO27JuAksYnq +aH8vI0xGvwn75KqSk4UzAkDzWSmO4ZHuahKtQgZNsMYV+PGayRBX9b9zbldzopoLBdqHc4n jQARAQABwsF8BBgBCgAmAhsMFiEEqUDUNJksLo6ZED1QIk+n58yCpmQFAmfIHFQFCRYU6J8A CgkQIk+n58yCpmS2PA//bqN1LfcotmArgElsa+0EGZSQlYgK48pm8WAeTXTngudP9IJ4SuKY HR5RNjHcBeqN+Me0zxRqYzRb8nGanHEkDyf4Im8DQM8d6vbyU+FcPmG4skud4kgS1zMHnlVd SXfSIwKC/hKgdHG8aBV7545Lz9X6Iohea+94wneD0aw/hqF+QWewGZhWJriWAZtvEkzNjQOi 4U9F/trLten/x7bpphDSnDMKJtITbtzATT1Dq7o7VpIUK1nCTQALMuMjKCdi8OdU/+V+R3O4 0PXWvX8qrvqYapVbZ+9KqT74FsuB0Ya9uXwgBF2Q6cRuETZk5vqaqKxzqoQZCO8AOz/58j6O 2RHNy/mZEN+7tJ5Tsq42zVJ4jxsT8b9YplavCMsnBgDeRWhcbYhCyttoL7nYISyWg4kQYZ/P wIV3OuNv2f8iKYsxNsRuClOAF82+gvqOy1/1pprFjy8uo2pkoOrb63aOP3vO5VHnRKgra6dq NcaZ+c6J4H+nEJGi2SkHAUJz5oBzuThvPudLvPA/SK8sKoM01IRxSihev/S/5WLazXB1PGem OCbvzC1IjWJJraxiDJ5IygokapUa2RP7+WBR22skQ3SSl6G107QgWKSyTOGWEaRmV53vxQLV jXuCmzSSasTL60zq5yGrT4/DYQVSNEUiUbG4pYekxJujNeEDkUlky0Y= In-Reply-To: <20260710-b4-pre-scalable-cow-v2-17-2a5aa403d977@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/10/26 22:16, Lorenzo Stoakes wrote: > It's often useful to obtain the number of pages a given address lies at > within a VMA. > > Add linear_page_delta() to determine this and update linear_page_index() to > make use of it. > > Add comments to describe both linear_page_delta() and linear_page_index(). > > We refer the reader to the comment for vma_start_pgoff() so we don't > duplicate information about the meaning of a VMA's page offset, which is > also less likely to result in bitrot. > > No functional change intended. > > Reviewed-by: Ackerley Tng > Reviewed-by: Gregory Price > Reviewed-by: Pedro Falcato > Signed-off-by: Lorenzo Stoakes Reviewed-by: Vlastimil Babka (SUSE) > --- > include/linux/pagemap.h | 33 +++++++++++++++++++++++++++++++-- > 1 file changed, 31 insertions(+), 2 deletions(-) > > diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h > index 2c3718d592d6..a950070b045f 100644 > --- a/include/linux/pagemap.h > +++ b/include/linux/pagemap.h > @@ -1063,11 +1063,40 @@ static inline pgoff_t folio_pgoff(const struct folio *folio) > return folio->index; > } > > +/** > + * linear_page_delta() - Determine the relative page offset of @address within > + * @vma. > + * @vma: The VMA in which @address resides. > + * @address: The address whose relative page offset is required. > + * > + * The result is identical for both file-backed and anonymous mappings and > + * simply determines how many pages @address lies from @vma->vm_start. > + * > + * Returns: The number of pages @address is offset by within @vma. > + */ > +static inline pgoff_t linear_page_delta(const struct vm_area_struct *vma, > + const unsigned long address) > +{ > + return (address - vma->vm_start) >> PAGE_SHIFT; > +} > + > +/** > + * linear_page_index() - Determine the absolute page offset of @address within > + * @vma. > + * @vma: The VMA in which @address resides. > + * @address: The address whose absolute page offset is required. > + * > + * See the comment for vma_start_pgoff() for a description of what the page > + * offset signifies. > + * > + * Returns: The absolute page offset of @address within @vma. > + */ > static inline pgoff_t linear_page_index(const struct vm_area_struct *vma, > const unsigned long address) > { > pgoff_t pgoff; > - pgoff = (address - vma->vm_start) >> PAGE_SHIFT; > + > + pgoff = linear_page_delta(vma, address); > pgoff += vma->vm_pgoff; > return pgoff; > } > @@ -1219,7 +1248,7 @@ static inline vm_fault_t folio_lock_or_retry(struct folio *folio, > void folio_wait_bit(struct folio *folio, int bit_nr); > int folio_wait_bit_killable(struct folio *folio, int bit_nr); > > -/* > +/* > * Wait for a folio to be unlocked. > * > * This must be called with the caller "holding" the folio, >