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=1794047188; b=THxPHPwozt0CtjVFadgEnfcfupNouURtw9XDxw6uoOiaE16dMOj1npef6L8saZuqm3lw eF65JGM+rHeVPEivWmslmJBcfgnSO6PFirevsosmnjClHKsqWqPsOC7C7q9W/yrNSzgFZ 9tnujMmnfVDHd/sy1xzGZW1ACFwCqISVtscfVpI+QQlJjBbCBWIthP/jVGuQbYij8WaTc mEKJJSCsPEd/kP2nbx9SZv9dEq2aAt4I5vFqFlTdV2RkkHVDdmsP6h+gUwEQvq07kk5x4 2cqEVlinPvJ6YwKKxGcpGKMzZSnK6Hl/qAy1t3uT3NJDobXtLDJfgb3KyLtLR4ShgbQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794047188; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=BH57Ycfej9zaXX/hcWN2ww556KK76gvyH5HN8Ibtl28=; b=ZGf+J+9LI9iuS54ZxOJWIZIw48daq53bJxYkVDWgya78tYkC3P78WrdrSvT+vK1RFRyB xjXUlXu/iI09waDDiFHjZ9ywwp00zHKHvz2DY2NiHWYLhQ3U8JasS2wt/lI5HSwPIgd5k Ri6se4SeJQhADlGLsJSRgvzb+ZoPQqtTE/B5ki1vxyhyfBSwIDemPb0AeJIINZIgRltV7 p543N6hflDs8jGLWkOjj4ONv0WeDxRM/nEeZtbuXZ0IHdPHUUiVf7PKE5XulmgHjKlIiG JkGHD4kBT23JkhIOIrDmSpg4ROL0X8qwwzT/Fjtb7ajuuZYuudhKJRZGvC2p/bIC7ZA== 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=KlnyVU8r; 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 5A339606A326 for ; Sat, 7 Nov 2026 10:26:28 +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=KlnyVU8r Received: by smtp.kernel.org (Postfix) with ESMTPSA id CCA761F0089F; Sat, 7 Nov 2026 10:26:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794047188; bh=BH57Ycfej9zaXX/hcWN2ww556KK76gvyH5HN8Ibtl28=; h=From:To:Cc:Subject:Date; b=KlnyVU8rgRY74Zz+Mz7JOK+oRoqgTf/WiZuONVnqjNDtjlWarf7fM3118tNsRy58v LhsscZij524oYJ47DuZQyaigc39BODN9ZU052Z7unufjsn7cFeNB41r8721WKZFJty HQg8t4JkBUlFIW2g0ROj2etOfXvff42V9gr39avFjO3/yG+dedyH4lSFHBfdPsSnQW CyYBFK2yflkFYaY8pBt7i+mBCqbin+yCSS2f9kVJ0jmIFI7HRZgZ+P4VFmcwQYbE1H f796h9/4JFZgNlhn3sot8HoS13ZmZKcDUMaQRHxbM8/4kbJjuTyjMCxQNvSPC6xrpy fLslVnjQkgilQ== From: Sasha Levin To: sj@kernel.org, akpm@linux-foundation.org Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] mm/damon/core: remove unreachable damos charge_{target,addr}_from" failed to apply to 6.12-stable tree Date: Sat, 7 Nov 2026 05:26:26 -0500 Message-ID: <20261107052626-failed-6.12-5695abc4e742@kernel.org> X-Mailer: git-send-email 2.53.0 X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.12-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y git checkout FETCH_HEAD git cherry-pick -x 5695abc4e742b947f586bfb6a080a80ad9957e5d # git commit -s git send-email --to '' --in-reply-to '20261107052626-failed-6.12-5695abc4e742@kernel.org' --subject-prefix 'PATCH 6.12.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From 5695abc4e742b947f586bfb6a080a80ad9957e5d Mon Sep 17 00:00:00 2001 From: SJ Park Date: Mon, 19 Oct 2026 19:39:56 -0700 Subject: [PATCH] mm/damon/core: remove unreachable damos charge_{target,addr}_from 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 --- mm/damon/core.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/mm/damon/core.c b/mm/damon/core.c index 479169dc9ac75..eb1fcdabc0075 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -3383,6 +3383,26 @@ 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; @@ -3418,6 +3438,8 @@ 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 (damos_quota_is_full(quota, c->min_region_sz)) return; if (!c->ops.get_scheme_score) -- 2.53.0