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 6BD8C501F36 for ; Mon, 7 Sep 2026 15:09:39 +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=1788793780; cv=none; b=WH8gd6xi8Mkr03Ogzk0Lmx9Q1y1pzudZ0gJa2fROW1RkuGDtsiYH23ryePxd3m+WBNyO03fLNp5NiMBUv2xEPFv69wpsl30WQTd1kZHO4Re8ENthK/FjhesiedUWKKAhuh1UvpUSUjn8kuursHnDXNcc0QA+5bN1cxsIYGtWWpI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788793780; c=relaxed/simple; bh=vYccEb9v4ogQi1pDxqXbn5V1aO3tYmPKmmHkHmBZo+g=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=cHGRBRXSVlPBUQO/3g90sR46fFzLsnfWWurMNaB3xdtq17T0c2jqRLgMucnZbMCLhwZSAK549Yb+EVOMezkoky5uO/YByEH1miiHVUAwnUzH/coR8rJnAUnetoVEAKp5GNEMqoqdYmv0Mbzlo4ygFS9VPLVnJ6L9yWdAoSTgNM4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=jZ2Ej4o6; 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="jZ2Ej4o6" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 808521F00A3A; Mon, 7 Sep 2026 15:09:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788793778; bh=a2tewgAqN1l+PrFwzJKAGhBGvdeNnZRzDfeds4hg5zQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=jZ2Ej4o6rCHE2ixHPTMWVEAmIO5OFj7MCI5XtjI1faWcP9lpG+HKvXSgQnnKOKaNu OSY7kCfUHC2N40EHpjnYwTVbQCDs8ZVTlGyw8AV1JoMFXO7+w1pzKYj2gtYCK7w+0o ezaMAlDteQT5vaKbQp0EkqF2hITJRtSYSJ7OLiL5qvyNmx80Mwds/eGji17U1sNaNn a5H0W+TS/TiCCvTYjJeWXhtI6u42a52JMveYl/lnfin0T/yDvgkKs+gPvYuPQf5+IW TBWH4fI/eV5wG8xmpsZJ4oE0PZqSqGvEUoBl+M9K8gP+xtMxh0tPt6BuFkJ4VzCzH3 AFMcrPlq8NqvA== Message-ID: <55ce7bee-c0e0-4051-8bc4-26cf3aa3f7e9@kernel.org> Date: Mon, 7 Sep 2026 17:09:34 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/madvise: swap in CoW'd MAP_PRIVATE-file mappings on MADV_WILLNEED Content-Language: en-US To: "Lorenzo Stoakes (ARM)" , Andrew Morton Cc: Pedro Falcato , "Liam R. Howlett" , David Hildenbrand , Jann Horn , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Mike Kaplinskiy , zhaozhengzhuo References: <20260904-madv-will-need-map-private-v1-1-6b83cc99fcff@kernel.org> <20260905171757.ba8b0f8f0f18ebd04418bfeb@linux-foundation.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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 9/7/26 14:32, Lorenzo Stoakes (ARM) wrote: > On Sat, Sep 05, 2026 at 05:17:57PM -0700, Andrew Morton wrote: >> On Fri, 4 Sep 2026 17:01:37 +0100 "Lorenzo Stoakes (ARM)" wrote: >> >> > Andrew - could you swap the patch out in-place with below? Thanks! >> > >> >> np. >> >> > Currently MADV_WILLNEED treats file-backed and pure anonymous mappings >> > entirely separately - using POSIX_FADV_WILLNEED (equivalent of a readahead) >> > for the former and a tree walk and swap in to swap cache for the latter. >> > >> > MAP_PRIVATE-file backed mappings straddle the two and currently get treated >> > as if they were purely file-backed, meaning any swapped out private pages >> > remain swapped out. >> > >> > Resolve the issue by explicitly checking for CoW'd MAP_PRIVATE-file backed >> > mappings and performing both walks in this case. >> > >> > Since the logic checks for vma->anon_vma this means un-CoW'd >> > MAP_PRIVATE-file backed mappings retain only the single file walk. >> > >> > Reported-by: Mike Kaplinskiy >> > Closes: https://lore.kernel.org/all/CABeknB_S2XJSHFgnHdgnN0rjzHhH4oQJs_APq9fvxHztQ_pgiA@mail.gmail.com/ >> > Signed-off-by: Lorenzo Stoakes (ARM) >> >> The failure mode looks pretty obscure, so I'm thinking that no backport >> is needed. > > Well it's not even really a failure mode so much as a 'known limitation' :) > So yeah agreed. Yeah, as we know madvise() just an advice after all, the kernel is free to ignore it :) (MADV_DONTNEED and friends enter the chat) > -- > Cheers, Lorenzo