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=1794167515; b=37Pd9TXa6kg+kIaHgD6AFugm+01B2kgju/S/PSzxxM8rDVlHqmRAK00Ek2dLKMl8PC2a N6vS7fqu3hzy2ITWrkTeTQyD7QgwdLmiQ89lVvoci0Mm25x5MxIcb7VWeqemhC9B5fh3k JUJF8Q3WS6Q8ouLt7PeGF2Mf+FdvggPDYdzHVnZ3uhl9CO6sQZGWmjEFlo0Br7mnQDsJg 9mKUx68mPH0gkY+9JttQ9RVsf/LMV+I6vdsNCq4g3iMookHsoBHoe8ZvULJAxG1xskHKQ RoVkCaV33yIdByMl1Wbvl1D/B2aH64BM9ACPT8OPXCjpSnMZcJztD4UbnUTXEF+kaiQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794167515; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=lmfkuEncO7HrgAvrvHVaRTSKNdQ3l+JsObN4du/E/II=; b=ONUv3Y/bXLSW0H100N56QnoOmiAxJByqjxwkfoxuhTG4n1NbIGiS8R8PJKmoe0uEmrnj G/nhUxBhPoa3+nkwBZk67ttiCbWfIkGYppB73Cyzv2lhaeKSjVX4lP4FjgEpxV6b3+BKk WuBqD+lOFu72zvULYYUVyI6kzvsGqRbyyE4lxLVwxUt4AxarmWUbGMNEtty/A8sNXDeQq AtJZPBBdvMgDsens/FEtOBPOT2YrcSnSvh4itJ3faw+hMHXFJzEITJfUydKz6BbBKiIu2 +jb4S3mmPGGcdwEK1zrVJ8WysrzbbQOFgWYREBo+hgslvnCeuTgz9iNlKD+ve/YwLYw== 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=VVWwxJeE; 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 89471606D809; Sun, 8 Nov 2026 19:51:55 +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=VVWwxJeE Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3644E1F008A2; Sun, 8 Nov 2026 19:51:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794167515; bh=lmfkuEncO7HrgAvrvHVaRTSKNdQ3l+JsObN4du/E/II=; h=From:To:Cc:Subject:Date:In-Reply-To:References; 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-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 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