From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794082211; b=NiN1ycbNJbmAsarpZ+Z01v6AtkwxTIL2SQSHL8PNMYJWVlvg1zYfKOBA9c+LF96RkfhJ mfUmvrEcrsHUrYbsiXjxTrJeQ5N9p0swLRXQoEJgpJ8NYDrayfbVN1YHZtjvz7S0+rgal sIhnH0DWe2coCC3xrwid3aKZjeLHicRnlUOHi2jZYm62lpI9IQ+oJMZkKcEJjLGdIEWYC w6ZLVZoUcOqpneTzAX0KdnaH4FJybWU3+ZRWqpd57vhVbooLQqQNMR29BpsMeAsf5eoN1 zNc3Q/HXm8nd2TDeOl6L377KR5CPRsWVIuVWbUkQXyLo4trKoXewLJ+b1N82Jh0+AgQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794082211; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=oUgpNIq5y7P8hrOoDRzoRBlVsghumVDo96fytymZU4o=; b=akhSK4jYcAFwUnNdZCwmcZ8V4epug4UB2ZLFxM2Tk+mULlp2mY0bO39ej9lsg602LXug 5+kGrzstlj/khhefnS0SFmtSgwhO/D7otuLnBwKfjHC/pE0U33zwuqZ1AxDc5cl3Dn7Xr lTLFbP67zDLVY6bT0RgI48FngRWnZh0NLP3lvZ62aMWE7gLay/aUavndGVRlHyYLtzRKJ 4EcIyujxJBw1Nt4rT5RG2lxt4cvL2/3vkk0Q7NrGBM42zGkcfSWyaYEK8tuoyIpiPXQAY DyHaMKMwPzYosvcNiQ0bFovghpuvchbWz0f8khxDix/DMZt8/onmWqSxVmUoRK6TxOg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=c8GiealS; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 55C6A606D820; Sat, 7 Nov 2026 20:10:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=c8GiealS Received: by smtp.kernel.org (Postfix) with ESMTPSA id EAC091F008A7; Sat, 7 Nov 2026 20:10:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794082211; bh=oUgpNIq5y7P8hrOoDRzoRBlVsghumVDo96fytymZU4o=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=c8GiealSX7kI27Hkj91eti8JBokuozsH9hmLJ2W+cHpUKvghW7FhbRPdGgKqdIImM 5MVOfYeYluV3UkNGpqzbB90EiRcgKcT25oJrfVu7Pu+tQu6qn/vK01Fg53jesd9FCI 4/5h0ACmiirgOTFGbgzFUfD8Oe/TGZ6H9bnCD8BV+IibAKWyUpNQghLscLvQp1MRQE 8tXNithdLu9suG7QjyiOLWuDZy6+NHUUd1c/qLRJnbAvNYszj+dW0JUfdV8YwAmb9o uOjd+lD+sdGF5J3wCQYXfSzn4/4v58IVs9sBUhzFm+l8AQLVgePEKHvp3HufUPsy2A 35BW5Dp2u7rEA== 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 6.18.y 4/5] mm/damon/core: remove unreachable damos charge_{target,addr}_from Date: Sat, 7 Nov 2026 12:10:00 -0800 Message-ID: <20261107201001.206120-5-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261107201001.206120-1-sj@kernel.org> References: <20261107201001.206120-1-sj@kernel.org> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 f2666770b5436..00cd0e2a1e341 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -2261,6 +2261,26 @@ static void damos_trace_esz(struct damon_ctx *c, struct damos *s, trace_damos_esz(cidx, sidx, quota->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; @@ -2297,6 +2317,8 @@ static void damos_adjust_quota(struct damon_ctx *c, struct damos *s) damos_trace_esz(c, s, quota); } + damos_fix_stale_charge_pointers(c, s); + if (!c->ops.get_scheme_score) return; -- 2.47.3