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 35A473ACA6C for ; Mon, 3 Aug 2026 08:27:50 +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=1785745672; cv=none; b=YuNJQQeOw19CM6gcV6ihpRyDBwv3BC0u2S75YeSD2eHV/LWEP403x5FE2GTg/5TRBO+3vt5CfYceedIscgcWkLyIs4OZI8EXODEH3J6yTiA0DH5yWcd09GrQOdlOn02lH+qNVqYz9H7wMSkVmQ0E0updEFgo1HWJyr8c+Ko1Tpc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785745672; c=relaxed/simple; bh=ohZZKwswdIgjZmcD4VgiL1TK5DhI61ldc5sA22zx0JA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=lkMnNDmy9Wap53qtBx/KgJEoZlcmrjEeySRAwDm9LBiuANyJnXd/bB48UEhc8jwO600wsgdzARjY1xfV4x6rYfmLLrK9LFAa+k4Em0id2WRD19qSva8b6jx+6tMtK5L+YHaa7kktosWTbwxWGAsMhw4we3prtx+WIPkz75qHa78= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=AbfcY4u9; 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="AbfcY4u9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8AC8E1F000E9; Mon, 3 Aug 2026 08:27:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785745670; bh=a+z9Du/7peIkWHVD90FqJtdry90ZFGmfOP9ki67NwPg=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=AbfcY4u9BcDKVXRy63CDlWEDBdxlRgHjcRAsEvPiZXCIpSaq69MUUu5eOEj2VAaeM m/5glaqtxhPJxgzlILYfQGrxMAh/FY0A0lj1UYx/+BSwaPf6XmRSXF2+Vb5KzANGI3 2wQCS3qKKxvMnoYkKrcgGQJI2UjuuOaaLVUFodb90z9qvSGvBsMrRwLn9wE0EVvkKa M1aS5ttx6UMMfMTUEct1Q+//SH8VbLkFd5dIUxBLghmZDOPeBXKhVD43o7CTMDY1Rt HnFLvS/ehZb+9UMLDspksn3+LoNlFKjjP7nJmROzF0daBM3SUVrOEpLZl5Tdb3hEpE IfOPj3JsNCWMA== Message-ID: Date: Mon, 3 Aug 2026 10:27:46 +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 v3] mm/page_alloc: only update lowmem_reserve_ratio on sysctl write Content-Language: en-US To: Andrew Morton , Jianlin Shi , Joel Granados , Kees Cook Cc: linux-mm@kvack.org, hannes@cmpxchg.org, surenb@google.com, mhocko@suse.com, jackmanb@google.com, ziy@nvidia.com, linux-kernel@vger.kernel.org References: <20260801114434.232c97a74d9616c43aac2456@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: <20260801114434.232c97a74d9616c43aac2456@linux-foundation.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit +Cc: sysctl maintainers On 8/1/26 20:44, Andrew Morton wrote: > On Sat, 1 Aug 2026 23:11:25 +0800 Jianlin Shi wrote: > >> lowmem_reserve_ratio_sysctl_handler() ignores the return value of >> proc_dointvec_minmax() and always calls setup_per_zone_lowmem_reserve(), >> even for read operations. >> >> Fix two issues: >> >> 1. Propagate errors from proc_dointvec_minmax() instead of always >> returning success. For example, writing non-integer garbage to the >> sysctl now returns an error instead of silently succeeding with >> unchanged values. > > AI review suggest that this caused a new problem: > > https://sashiko.dev/#/patchset/tencent_1BB7A5C4D5EEA67346634417753190E92A09@qq.com > > Not sure what to do here. Perhaps pass proc_dointvec_minmax() a > temporary then copy that into sysctl_lowmem_reserve_ratio if all > proc_dointvec_minmax() returns "OK". Seeing the v4 [1] it seems easier to keep the current fixup code until proc_dointvec_minmax() is fixed. > But really this is a flaw in proc_dointvec_minmax() isn't it? It > shouldn't update the table data until all the data has been validated. I agree. What do the maintainers think? [1] https://lore.kernel.org/all/tencent_B9556590D4B65ACF74C06897689A6E39F206@qq.com/