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bh=kuii1OxTBCJKn/aKUCi3+2COKzMgGJ8Y558hfckwvWc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=bHnHlvuLtN8sAW4efMQa/2BStqLpezZTUSvbaMHV4QTiT0zRg9a8rjjsZ4nEIzjMX NB0/XxHhbZM4xXO/RZgy2tQz276Nxs0atzjpGLVanS+E8J1uhgXiGKbkjZ+C//TP6X 5Y0mPolpqhHcAvQxISBEINUq2cAbGNgNEX08k3M2SAAC7XbU57ZHEZ9/UYN0tNf9yJ 5CmaCYVRbHLauBdWQBbuNuXHL7o+0mKlheCugfDltMc4jjblbf5JUrTOM5Zs0wL8oc gb72hxel/oq1xU7u11QdktDXNwNiNEq6fDbzNy+pXuKnGEeKWMIp9WVH9fML3DXTh3 TkrYcb2Z7oHyQ== From: SJ Park To: Cc: SJ Park , Andrew Morton , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [RFC PATCH v2 4/6] mm/damon/sysfs-schemes: drop redundant and racy zero target_value check Date: Sun, 1 Nov 2026 09:16:27 -0800 Message-ID: <20261101171630.81477-5-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261101171630.81477-1-sj@kernel.org> References: <20261101171630.81477-1-sj@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: 3F42E140004 X-Stat-Signature: 7gb1yi6aw3a6mbtfor73u31stmtoc5y8 X-Rspamd-Server: rspam01 X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1793553400-219655 X-HE-Meta: U2FsdGVkX19p1VwxbkM8VwNl/PIQUr5Z0G2UQ1eXjK7/N35zlu7pddLHWGNgFGHmhQMx7qOA2AKuu/edBfMkl11oxB5FPmWdi68N8Xb5is5CWnDHdCDp929XLaCfDN25kmLedoMRkGcocmyG+IGp1REJgl3UGELb9slJQB3MA89nt+diF2CNECkBGMlLwtcNxVWD4ejHcU39U4rczWgRsYONvyb64slTO/DeY1Qi0NNjzoL/dqWLqiTIujxuJ3QRwdyzKrgdeEdx6cdO32JiOjpkJhgnz4hxaQOF9eiBvQCuRgiLUfWvNH+vJfPJRjaNywODk5tPaTo15MQbfeMsIHOXvpt/1sO3lcJLhs0cC8J9BnAQQ0hRH0u7JZBx/4aM0TmNCqr4qYfl4l8k7I48BGL9BrGJvOh2o051LleK12rD6pL/AZEIGhsXGWIF/vU3oKiKPZmpjsgsaBZ1eOx06hFgceYCmiUHrIb8i4ZfT7C/lYjcGdZ741ElZLR25qKfp28C02cmm5FGu6nznFjw7VN73A6pjyTI7XjBhXfSywYiZfiVKrwXCt4q3o73lMle1dDTdxkVkTlowMQKCYHAjrpc8JOoPI+Rffw78ONnMZRauQ7IMzR9Zsi7i0ueic8EmZxAifEolRoCiLOizgOi+ItE0yKen0sQo/n9ltuV8bG5ZbaYBe/7toy0XlrjZDZ/VMvG31B/WkunyKP/iEKt1CRSQ9fpAHHUX1bctdJWtObN0dJnZDP3u06gDX0cprHOLEVO0zEkN7dXZyFdbIGK9XtvNBrZURivFu9hi/JyTvkqw++ewSnUBTRqIzN5L6i59vLsWCtZgxbAjdXc9RNjnXklddeEM2whLkggbav0jP3VVcj6u5sHfAV1pq5X5LVF4pxkh5lDT3+6bfTMXBo2Jl9drVbQJWUv8h9bLI8bEAmJe+7X7zsXIcHeL1Yd3fkautYd8boBWBWH61Ba7ce uvLd63mm cqd/4hQ8nwvGtUnnykMYCeA3hYzlyjv6qtg5vhg0+ebeUKB02j7NFw05WAf/GRnyC7PoDt+Z4iMx+xEBjExLyYjkaz78ntXKwlhJ5MTr8Q8VvOb3PS30D+N6Lf/f+Qt6gxUnn41Db2lymdbGIrLUcaIuJX0Vc7SMXj8LRibUGgINRHPq1TQ3q7ggpwGMS7SwnneAjo3tieGq7qkq8XglsiOeseEnT34W8TZ91m8byzQWq8Jvjy6lBv/qMoLwhtKcP/x0K+mNKYd1Bd+kPNu1AQ0xPeg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 DAMON sysfs interface disallowed zero target_value because it could result in divide-by-zero in damos_quota_store(). Because similar checks were duplicated to other DAMON API callers, a patch series that starts with commit 610c4438fb66 ("mm/damon/core: error damos_commit_quota_goal() for zero target_value") added a same check in the core layer central parameters, and dropped redundant checks in DAMON_LRU_SORT and DAMON_SAMPLIE_MTIER. It forgot to drop that in the DAMON sysfs interface. Now the zero target_value check in DAMON sysfs interface is only redundant. Further, it has a time-of-check to time-of-use (toctou) race with target_value_store(). It can confuse readers to believe [1] the division-by-zero can still happen. Drop the redundant and racy check. [1] https://lore.kernel.org/20261021005234.94107-1-sj@kernel.org Signed-off-by: SJ Park --- mm/damon/sysfs-schemes.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c index 637f1bd0c950b..38efdc258ef3f 100644 --- a/mm/damon/sysfs-schemes.c +++ b/mm/damon/sysfs-schemes.c @@ -2898,9 +2898,6 @@ static int damos_sysfs_add_quota_score( struct damos_sysfs_quota_goal *sysfs_goal = sysfs_goals->goals_arr[i]; - if (!sysfs_goal->target_value) - continue; - goal = damos_new_quota_goal(sysfs_goal->metric, sysfs_goal->complement, sysfs_goal->target_value); -- 2.47.3