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b=FPEMvVsUUP8GraCvy2ryJBS5ylEbMH/M7XaVX8UGrIaKl2HeAGB/MWdMhtgAz8uDW hyWFw7JkBkZWNRMR2QhKIBt8bDe4pMDqhrl6Yt+Rin2/P2YnXNVoUkP2s0tNkG7eg4 HktkDZoko/ckd1GZswdk5voPkaxz7Ttc6qMcwEmpYsmjeu3O+G3AInHVoaAJZ0JWAg g64NKzGQHL0RjVSsbg7zUUqPYzzWQrxxY13xfgtu8WfRXJ3AiNEJ0l2YUOlfoKLPha HFb1UhTQe5cuA8qRnud7AAHPkn+VLfZa2CWbSFDz/wKGSgR4jZhrvGDM3F79Vc+HAN EK1RUo0c1i3dw== From: SeongJae Park To: Liew Rui Yan Cc: SeongJae Park , damon@lists.linux.dev, linux-mm@kvack.org Subject: Re: [PATCH] mm/damon: validate addr_unit to be power of 2 Date: Fri, 27 Mar 2026 17:14:04 -0700 Message-ID: <20260328001405.4253-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260327145627.10419-1-aethernet65535@gmail.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 7D471160007 X-Stat-Signature: ht3u4ffy46qe7zgutfutjs49qextujhz X-Rspam-User: X-HE-Tag: 1774656847-701018 X-HE-Meta: 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 DmXlyVRJ WuUoY3utfdilDMlm0fscfFXkhtfETSCd9aHWATnSBoNm2wg8Sash3qfmmU9oI2YutsdhXxsTSEuUrqoZrkcVZtkhxJLQwYzV9ffw5mOenc3tzMKiJXdOVOugVAuyzqdgA82tz8fV+dMUErqfGn43cZxl50mM7eZ992mM5xxET4gIvfHUbF23bWo3bWtM5hhFi+zpqQKiskuFbAp20tZPXyyvQmjh3Nav1Mb5HXq5IU23QkWEKRS/ZJxfS9l5fehRCsvYipj/t7ZVmwgS0BD8C0+rbEA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 27 Mar 2026 22:56:27 +0800 Liew Rui Yan wrote: > Hi SeongJae, > > Thank you for the detailed explaination and for pointing out the > 'PAGE_SIZE' limitation. You are right; and I should have accounted for > that. > > However, I performend further testing to address your confusion > regarding kdamond's termination. My patch didn't fix anything. > > Here is my reproduction: > > # Log (Both with and without this patch): > > # cd /sys/module/damon_lru_sort/parameters/ > # echo Y > enabled > # echo 3 > addr_unit > # ps aux | rg "[k]damond" > root 71 0.0 0.0 0 0 ? I 22:26 0:00 [kdamond.0] > # echo Y > commit_inputs > bash: echo: write error: Invalid argument > # cat kdamond_pid > 71 > # ps aux | rg "[k]damond" > # ... kdamond terminated > > I am very sorry for the noise caused by my misunderstanding of the > sashiko review. > > The real question I am facing now is: > Should kdamond terminate itself when damon_commit_ctx() fails due to > invalid user inputs? It would be better to not terminate. But not a big deal. Users could be wary of the consequence, as long as it is well documented. >From my perspective, therefore, code maintenance is more important. If we can make DAMON not terminated by invalid user inputs caused damon_commit_ctx() but it introduces a significant amount of code complexity, I don't think that's a good deal. Thanks, SJ [...]