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b=Z2DnN9FQ/pONrpfmYqdsyadnC5aGPtVXxJDblg/cLi22vodpsA39uT285qpPCtkEf t8z1UcPayk6eXHiM30oSoskX1Wpmec2l6JudAx+tFqrot2gNRvnMqZ6aXY1wT0q+4z LUbGrWu4KcRkeFtbUXgLrHgIxFLhe0onBex8+Ov5cRNg3Wb7nm2R1h5yzObEfKyjWJ ye/UmpNJFnsa3Cms1EGXt+cCMS6N5AYo6GRDh70btIaRB6fpummEYhWZ34nldZoeFQ mV1QaeZvuSCI6u0ftfK17OigkxV+zy8trlgG2CIMbi/6LKgrKdDOcHSdmcbgCOM3yS Z/S7v5GANMagQ== From: SJ Park To: Cc: SJ Park , stable@vger.kernel.org, Andrew Morton , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [RFC PATCH 6.1.y 2/2] mm/damon/core: remove unreachable damos charge_{target,addr}_from Date: Sat, 7 Nov 2026 14:47:59 -0800 Message-ID: <20261107224800.340250-3-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261107224800.340250-1-sj@kernel.org> References: <20261107224800.340250-1-sj@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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: rspam09 X-Stat-Signature: 6hncykuffkkxitkehe1egc1fc5nciuig X-Rspamd-Queue-Id: C640A160003 X-Rspam-User: X-HE-Tag: 1794091694-99873 X-HE-Meta: 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 InTat7WM pd9GZ/lDJ9+TGeIe3dAuZwBO4r06cbcFAVvSS+OKbb+2uuFk8gAkK9kxspyVyjUM7QBojMXHoXOOIdiy07Dc0vXXnSejOPsXiU6HNlBROq4RA5OwgDXHqexGnmTwpcdj/Zall+/9lZi9qg48yNlkocyEB1o966+I4AytdbetxQlCF8j18mHCFdzvZOajbiDiEfFYi06xsrXvMybOh2GRfNjdBOj3Fk/UC2n2GM5eLcBhLB1riRnZ4MW0FoKOM8rAEx3ifzBUPIQtpxQQTa1AuqUFJ2c+SXJW7rDyETrxXryIbvLfgWl1fZDF6aUhwcYm9CBDDK9UBU2Tt8BO3jU0Nga6Y4pP1P6PekbGApd/vEE5prilv2eDi8WAfXNaaSUTeyvJbn62xRU5qpqM= 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 damos_quota->charge_{target,addr}_from saves the target and region the scheme's quota limit is reached. damos_skip_charged_region() skips the target and regions before the point. The target that was assigned to charge_target_from could be dynamically removed from the context by the runtime parameters update (aka commit) feature. In this case, damos_skip_charged_region() cannot find if the point is passed or not, so the scheme is effectively disabled. Similarly, the user could also remove all the regions of the target using the runtime parameters update feature. It would be uncommon to do that, but it is a supported feature. Because the skip pointer detection logic (damos_skip_charged_region()) works for each region of targets, this result in the logic is entirely skipped and the scheme is effectively disabled again. The user impact is that the DAMOS scheme could suddenly stop working under certain uses of the runtime parameters update feature. It could surprise users. No crash or leak happens though. Users could also simply work around by re-installing the scheme. Catch the corner cases in damos_adjust_quota() and reset the pointers. Link: https://lore.kernel.org/20261020023958.108276-1-sj@kernel.org Fixes: da87878010e5 ("mm/damon/sysfs: support online inputs update") Signed-off-by: SJ Park Signed-off-by: Andrew Morton Closes: https://sashiko.dev/#/bug/linux-cd0c55fc-0cc8-45d8-9637-3334811c49b8 Cc: # 5.19.x (cherry picked from commit 5695abc4e742b947f586bfb6a080a80ad9957e5d) Signed-off-by: SJ Park --- mm/damon/core.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/mm/damon/core.c b/mm/damon/core.c index 9206737d05ae7..01f93146b92fe 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -860,6 +860,26 @@ static void damos_set_effective_quota(struct damos_quota *quota) quota->esz = esz; } +static void damos_fix_stale_charge_pointers(struct damon_ctx *c, + struct damos *s) +{ + struct damos_quota *quota; + struct damon_target *t; + + quota = &s->quota; + if (!quota->charge_target_from) + return; + damon_for_each_target(t, c) { + if (t == quota->charge_target_from) { + if (damon_nr_regions(t) > 0) + return; + break; + } + } + quota->charge_target_from = NULL; + quota->charge_addr_from = 0; +} + static void kdamond_apply_schemes(struct damon_ctx *c) { struct damon_target *t; @@ -890,6 +910,8 @@ static void kdamond_apply_schemes(struct damon_ctx *c) damos_set_effective_quota(quota); } + damos_fix_stale_charge_pointers(c, s); + if (!c->ops.get_scheme_score) continue; -- 2.47.3