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b=I7RODPVcJBRsd6s9UWRbtl8lpLOuBZpmxFX36HCqgpaIVZNVcAujidNCKp4lU2FFe BAm1Sq94dhTqpSAovKm8Qh0kXVTk4OAQ/EgO69kB7YrXIJOSCR3U1XsIEdq5+PQj10 dgsj562UwM3s3jCZHLRr76XK0JLD0TgCBH/4qVwMueLXjV59DBZ080kXS6S8sd9xO9 dakp9bUiDf+bNOEaUGRXfrC+ZEcoMu7JNmMhqMRnS+jsDDRTLzjdmrIIJlVcLWVmQ9 u5ExWj5KFg4XfPKlyW3XiWRNCETRpSCzh7i3n/3YhxppLjDvmfAIQ6+yPKfkV6Mpni yea7I4chqnnyA== Message-ID: <2fcfa480-e4dd-477f-9c02-42756f3aa373@kernel.org> Date: Fri, 7 Aug 2026 12:05:53 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5] mm/page_alloc: only update lowmem_reserve_ratio on sysctl write To: Jianlin Shi , linux-mm@kvack.org Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, surenb@google.com, mhocko@suse.com, jackmanb@google.com, ziy@nvidia.com, linux-kernel@vger.kernel.org References: From: "Vlastimil Babka (SUSE)" Content-Language: en-US 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 X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: D408640009 X-Rspam-User: X-Stat-Signature: coxswyw6mddgncmrhg8ta188up7696p5 X-HE-Tag: 1786097158-965463 X-HE-Meta: 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 EW8DlmGV eMoJ9kXRgCv6pcs7mJSZeBkV1jm7F0KcEVM0jAUEgDaWh2HKphRQLpUEfgrQ5Lb/yAqVQZ1/Dx5MtGu436QSZdS04UwWOa8Sm5/uutng9YxeLEE7xg1RG36c+1nkRwMmHhTFTRHRBUnBcrGoeIubVkGk9tnlSSKLxI30ACRNcHMuPNtVjpZSCYGclBV5zT5BOLflnNUaEGiG4EEOF7nIXDc/P90NuYHfhDtYB0wVBZzbmA4QPakQET4UV6E5LvPhvWwJNDa1Xo9Z1aVmsjaNuNCE+JVmMRcv79BClhljwWupbbKOysTOFx2vmFb/UG5Av8/xyoJ1/R6H/a+35ThgMOFZlq1R6tfCMEyznJ9Ow7OQzkjH664wS/x3zQuA112hpQS/ipD5+iGhGLttJKu2dDknlGUvp2tZ+pdmU Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8/6/26 10:27, 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 three 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. > > 2. Only call setup_per_zone_lowmem_reserve() when the sysctl is > actually written, matching the write-only refresh pattern of > min_free_kbytes and watermark_scale_factor handlers. > > 3. On write, parse into a temporary ratio[] array and only copy into > sysctl_lowmem_reserve_ratio[] and refresh derived state after the > full vector is validated. This avoids leaving the ratio array > partially updated while skipping setup when proc_dointvec_minmax() > returns an error on a later element (suggested by Andrew Morton). > > Drop the manual "< 1 -> 0" sanitization loop and set .extra1 = > SYSCTL_ZERO on the ctl_table entry so proc_dointvec_minmax() enforces > the minimum on write; negative values now return -EINVAL instead of > being silently coerced to 0 (suggested by Vlastimil Babka). > > Link: https://lore.kernel.org/linux-mm/tencent_FFD4F4D728AAE8A8AE0AF277A59854A29A06@qq.com/ > > Signed-off-by: Jianlin Shi Acked-by: Vlastimil Babka (SUSE)