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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 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 X-Rspamd-Queue-Id: 97DEEC0007 X-Rspam-User: X-Stat-Signature: fyt7dac1dfdyyid7k8hi4u8spmqjwwp9 X-Rspamd-Server: rspam04 X-HE-Tag: 1785745671-170118 X-HE-Meta: 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 WG8tJWkv JuhTcs7iSwo1jWXicprUb9yPERfhbptfuFGfcrNH31E7WrcyyXcd5MfnsHMLLgkTlcBFu/PIA7Mv+hbWrIzARcXNtZrhkrfJ7cYPboVezGMsUSRPx19QGjEkG6En2N3O6Kd+Em1imOzWM85DT04k7Q3l3NS8FzcB3x9NOPIP4WIK1J22cezGSWwwv/q+xPDSAgAndjb17UGMzr6Ybo05lUjKlm2EXlaWH2FSkkQmptzuHI6QKQJ9GolQfJ0KlwQ/OTRFS3wXUfNUXcHk9sEix6kTr7wmyTh1dJJMNmoXY4pqddWc7CmnOkTvtE8kNFqVRKgtUGQKk6ceuBQZmMZTtrjZhbEeDg24yDcrL9+fp1hrqYcDgxuijVG8PlS+/ufhG2SNFmrK74WWgrgzhryUDiOPjwICwxmlQwOchml1LA8Hr2Nf417cwqQn1W8dR/5I1kknYKf0GbWfuLA7+2LvccrjwKg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: +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/