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b=PJZKHTKgxkFAm6c93xDqAvoQwjMN6iFhyBgIc/AWNrJTBMV5ToxMdx0C1WvtvY6yO tiHmG/kp2qocNcaEp8x1xQkKpseGrUEoAWEq7x4wgh19j3R6ytAer6OQVSpACxluQC JhuAm2J8WUnSAJ7vLpPNg/aG2ZX5yumCQGfzKLT8mNDS+bqZdtX4hLJV3YS0cXtFzj L7Irvp3FD/jqqfaklw6jGp67En4y/OsTbXkd1i4Gt7NslSqughMwRiYUCj8BKW7uXj Nmvnajxn45i1srr5n0MleeHWJSOUtiGHBY98uYJpo9X7W3oJOSRy8IMEz3wTy9G/nw K+jL1++CPZ1Lg== 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 4/6] mm/damon/sysfs-schemes: drop redundant and racy zero target_value check Date: Sat, 31 Oct 2026 13:26:11 -0700 Message-ID: <20261031202614.96036-5-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261031202614.96036-1-sj@kernel.org> References: <20261031202614.96036-1-sj@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 4D0DA40003 X-Rspam-User: X-Stat-Signature: btkahzcixccd1m5jqejw3ow8x4m7as7y 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-Rspamd-Server: rspam03 X-HE-Tag: 1793478384-26786 X-HE-Meta: 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 IGAK/OEt IXOPHbKaEKRuYtezdebR/ux9dcA8EhU1V7eXu0JmyXgoUHK4nl+AE9qrZp518YSFin+0aigH5uwWaqxCfrh6vzejl80k7CUNak7tmwAOgmGagdcSDCVlxMjPlClYpcHeciuZ8mCe9v/rymxiGIDyvMXupAgMMAgFWjeB9e+CFeQEssLS/kZiYQPucFRskU2zXwrukkiJNqUyggDT40oIJRx6jrgtHJic6ioeQGr3k/i+ik9AAd/jlECQ2Tf1G3/t2bp3MmzFKxzQgXha3RSDkjKTHpg== 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