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b=XPLksAgYffr0yle6lKJ6XByLq/4bc3FRUCodqnf4SrClABYzHbAlOrsZjitB0eoFM rFkVa/PJlHlAg2Ran+D/zwQBrPw9NSVmsdQ+90da47gwcAt9fnNMHf/lqveBv1ydk7 W2Coiaw+m17khA9iK1rsB6UZp7xpk8hrVgSUreA6NQnsSf0woOVy5FhFt8NYn0X4AZ xiQyesN0WbmdeGF5iOnybS/2YvZux6O/LOm9qDKkCtrGxH6kh5mSnYXOxfm8A9Q4Tr wayNzZCNfrYd0BvA6va5cTa+uUq7QT7ObBguny0eiGOnr7f5zEKCGuBHN/XIi9Hk+8 A9QDivFwMiVnA== From: SJ Park To: KunWu Chan Cc: SJ Park , Andrew Morton , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lianux.mm@gmail.com Subject: Re: [RFC PATCH 4/9] mm/damon/core: use damos_quota_is_set() in damos_adjust_quota() Date: Mon, 14 Sep 2026 19:26:33 -0700 Message-ID: <20260915022635.103818-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Stat-Signature: y98iej9bdbbfohuzba3is3pp6qka97a8 X-Rspam-User: X-Rspamd-Queue-Id: 725E0A0002 X-Rspamd-Server: rspam03 X-HE-Tag: 1789439203-646246 X-HE-Meta: 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 Zpktr2un G4d94lT7EUhkLydv7oX0+np1TlLj2HqvXFitl7cBm7ixpaoJNlbDDhaYkt1d4EviQ92JqmCDERZAaZlVPmTS16yLsKzyOqkYxQJMdcFWpOmYeqtnIvtkAeA0rAVWVIYsn6w0G3Scw/OinRRp4XeclAGf/bVqu2LrSIu5nLcSEPniKaUbs+BZ5uAMdPqxRdonDZ0nKbx893A7unkHmnRjO1wK4qj82yctQUjyWJnQxNT88yTZA6Vcwb6n+dX81WFXS6dPENgXcLA8tm5n6leCcTsRS9mTQqd2eayawT0bRfoYX8eWR2C6nJIKcKiZhhgthhbzw194u6P40QvkspzoTAU7kRQJw087Ap1hwYuNzGzTsUCgZKvg8+OJgVsgfE4CkIrfGVDMkBEehRezI8LWuM45NLvFWSL7qNWHq Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 15 Sep 2026 10:19:43 +0800 KunWu Chan wrote: > On Mon, Sep 14, 2026 at 11:16 PM SJ Park wrote: > > > > On Mon, 14 Sep 2026 23:01:48 +0800 Kunwu Chan wrote: > > > > > On Sat, 12 Sep 2026 13:08:05 -0700 SJ Park wrote: [...] > > So, if user sets only time quota, and then commits the quota to zero while the > > esz is non-zero, esz is never reset to zero. As a result, DAMOS keeps applying > > the action with the esz forever. Correct? > > Yes, the stale esz path is confirmed. > > One clarification, though: it does not keep applying the action > forever. While charged_sz < stale_esz, damos_adjust_quota() still > returns early, but damos_apply_target() continues to apply the > scheme and damos_charge_quota() keeps increasing charged_sz. > > Once charged_sz >= stale_esz, damos_quota_is_full() returns true, > so damon_do_apply_schemes() skips the scheme. Since the early return > also prevents the charge-window handling from running, > charged_sz is never reset, and the scheme remains permanently > inactive. > > So clearing the quota can result in the scheme applying up to the > stale esz, and then stopping permanently. Thank you for detailed clarification, Kunwu! > > > > > If so, this may deserve Cc-ing stable@. Kunwu, what do you think? > > I think this is a functional bug in the existing code, and Cc'ing > stable makes sense. Agreed. I will post this as a hotfix soon. Thanks, SJ [...]