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b=VVWwxJeEFsdCKe/oZmO70wy3CLjkq+dbaLQBYHovLEo0MvUIDKZNciyh8j94v+Jzt eE9/0sShh7R2iqJ/0J9MGC38DIdvDzJfNGi1Sy0uIlIzxY/fAbGUb/Wgh75ezGIarA IbfLGoXBdu02K4bO2CQ2CBGh9OcSBrDb0JQWGOb6r0cWFv9iNSSjci/hWBVA15cfEK 7GWZpNIsd9Fb4g5TtwAv1T9TeLCGUQqgBr5Rz/bVOFvPYyICpra6ZMyXBEkUnGFjT1 4JzfbLHXiW+j0iHNOU+m/Q+PI87jvVZrJw1W1yP/yyZ3jFWbYi2BZ+Mffen5/ge7Fs oDwa/ag5xAOXA== From: SJ Park To: stable@vger.kernel.org Cc: SJ Park , Andrew Morton , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 6.12.y 5/5] mm/damon/core: remove unreachable damos charge_{target,addr}_from Date: Sun, 8 Nov 2026 11:51:44 -0800 Message-ID: <20261108195145.115792-6-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261108195145.115792-1-sj@kernel.org> References: <20261108195145.115792-1-sj@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: 5nzisid59gm4kr5okyyughizbmgec7pd X-Rspam-User: 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: rspam10 X-Rspamd-Queue-Id: 2FD64A0003 X-HE-Tag: 1794167516-857952 X-HE-Meta: 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 3CoKXyy5 3uCc/lujNg0dP1zSg9pxGH7nep7bKU+MJulvv6MwFZsnnMgKEJ0lPoET+OzuWZvw5yNOvr1MrtlHqMMQwy6k4NSJg+roHXUm3yPq+QKbH2AGQ7ZXzfgOl8AezNf5ZJvJdgE+3tLHqa7vRkrKfd5Qx7byiuLjSohRbSdViFGOBs0sd+xYkutvLqRzTgxuBscx7FGs4oFqllXak52jKRTCtGe14Hctqyu4R3MCksgPLNm9olVycsjJB8ZfUKiwGJQOFRxGFzE7TVhHvvSSkkBXcEDoMjJjjIyitz+APIOR7w6LE7GlSSk/3ZoAo2dAk6+90jHYp5iwNhoEpzrK5iGH1aVtzhfMkkhWNKvP4DlJ5TwcVB1PbQpgqoIwlr9fMUAYC7VP/+lp+9tOh4/s= 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 046c07b86a6e7..badd0628e5eb2 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -1686,6 +1686,26 @@ 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 damos_adjust_quota(struct damon_ctx *c, struct damos *s) { struct damos_quota *quota = &s->quota; @@ -1714,6 +1734,8 @@ static void damos_adjust_quota(struct damon_ctx *c, struct damos *s) damos_set_effective_quota(quota); } + damos_fix_stale_charge_pointers(c, s); + if (!c->ops.get_scheme_score) return; -- 2.47.3