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b=gLFh2pqyt7vwBmDc2xfuwwE3HOJAa3U3cilehm7Iwjj0EbZo7+crWqLU1COEHF2le MbySZw7N4oqbwgcye2XvZIQcqGk6S4TzH/+Y+1pJl7p1cCrYTIN2jyoaZbI2Zda6Dx KY1fNZkirbh6tu0JFr+2hZasuSViYc71gJvGWlzzmk4RLeptOTd6SI4L81eC72gUEl iKx6jLNKVG8GgncpGP39Luk19+tMaHwJxqCHxJ3R46+gO3XjKR7GyqXiOFSL7dpnJq zeuzrpjYopnspq4L7+yITt2aZ3OhuWzbcs2Qth4NnBjVMjKmhZ8aeJ+/JQYat2tLgH WXPwAp+hLYZrQ== From: SJ Park To: Liew Rui Yan Cc: SJ Park , Andrew Morton , damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mm/damon/tests/core-kunit: add test for unconditionally skipping the last region Date: Fri, 25 Sep 2026 02:02:38 -0700 Message-ID: <20260925090239.47821-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260925045350.66595-1-aethernet65535@gmail.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: DC60B4000E X-Stat-Signature: mzec4uwbuptkfdi84cugcn7qckwbcoet X-HE-Tag: 1790326965-274771 X-HE-Meta: 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 gxRlj8Gl N6UwF7APhBjSG470OFPkmKlQqworPOfPKt23D962QI3/ouNmEHyXs0iPmudcPP0UBlew25BhWHKFO1FC8kFdizf7fECwf4nA9WfeAxU0Fq/wE5o7HpgN+htK1yBrArMrXtMAwkHY7ydOI+MafMtOz/sRuGIP82WyFuSbGciNIP3fPeKlDVuwxZhMzphcdb4ZO6COdoDyXQkCKp0O27LlzEuNd9qWiskYproTTLGSlmOihagw= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 25 Sep 2026 12:53:35 +0800 Liew Rui Yan wrote: > Commit 50585192bc2e ("mm/damon/schemes: skip already charged targets and > regions") introduced a minor issue that causes the last region to be > skipped before it is processed. > > Example: > > 1. Target has 2 regions: R1 (0-100 bytes) and R2 (100-200 bytes). > 2. Quota is configured to process only 100 bytes per window. > 3. Window 1: Processes R1 (0-100). Quota is full. charge_{target, > addr}_from is saved at (Target, 100). > 4. Window 2: The loop reaches R2. Because R2 is > damon_last_region(t), the old code unconditionally returns true, > skipping R2 entirely and resetting the charge_{target,addr}_from. > > Result: R2 is permanently skipped even though it has never been > processed. > > Add a test to prevent this regression in the future. The bug is fixed by commit b3723b596b54 ("mm/damon/core: fix unconditionally skip last region"), which is merged into the mainline for 7.3-rc5. Could you update the commit message to mention the fix, rather than the original bug? The fix commit already has a quite good description of the bug, so I don't think we need to duplicate it here. Other than that, looks good to me. Thanks, SJ [...]