From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C594439C657 for ; Tue, 29 Sep 2026 08:28:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790670486; cv=none; b=hDjuZppDE8Km0SuU2Z6+RJR0e9NFY/C3ZJ0IoPgvBGryhHjSVQuSF0woVB9Fp6/MoQDsqVkBP6p+kslcoDRuPW8Cl4sMRAm9A2NtG1o3tjnsoRynFqsZhKsZ2PsjlgupUH9KYdFSal7ty9muPUyjQJeWg7g8JmZsjZMbVbMd0L8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790670486; c=relaxed/simple; bh=UP0Td7RWxBWEd56CbrddI/z4vVrHvpbnbf6NkFVLNfM=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=BSDEsPJRkbIpozAUXENqYIvckUDsWgVdu5P7L1LZ8emVOBhs4zx76ooSlHPyZbys1E53N+1HpPdBAWFa5jVkYdZj8PG/ERfjjdDusNblibi9MXylcCVdAR60Wlr5GBpkDxN8biloooCR/UIXjOujx5b51uluXpSDTQ/w1j7FRPU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Hk3x74D/; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Hk3x74D/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EE75B1F000FF; Tue, 29 Sep 2026 08:28:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790670484; bh=8pz8iIjGis0dmufb8Wbmd0drTFgXmoB+88Ck05iO7lM=; h=Subject:To:Cc:From:Date; b=Hk3x74D/yn1/tjroeO2AJqOndiCfTd/zd9MGfQlsBYa2+ZXgx5kKXKx3LOpfnaUaE jtqX4D2O1XzvSUL/YeQWThC7hNb3xmsrbRxMc5QHvaNbcI1yVauZT2/yTMRSRNeI1g LOpaOdjlkDlQAxT9eQGkk+oOOTVRlGDSE+E2p8aI= Subject: FAILED: patch "[PATCH] mm/damon/core: fix unconditionally skip last region" failed to apply to 6.12-stable tree To: aethernet65535@gmail.com,akpm@linux-foundation.org,sj@kernel.org,stable@vger.kernel.org Cc: From: Date: Tue, 29 Sep 2026 10:27:48 +0200 Message-ID: <2026092948-agency-overhand-3fd1@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 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 b3723b596b548c837a766aae3553c14a7b15af2b # git commit -s git send-email --to '' --in-reply-to '2026092948-agency-overhand-3fd1@gregkh' --subject-prefix 'PATCH 6.12.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From b3723b596b548c837a766aae3553c14a7b15af2b Mon Sep 17 00:00:00 2001 From: Liew Rui Yan Date: Tue, 8 Sep 2026 06:47:38 -0700 Subject: [PATCH] mm/damon/core: fix unconditionally skip last region Once quota set, the charge_{target,addr}_from unconditionally skips and resets at the last region of the tracked target, so the last region can be skipped even when it has not been processed. Example: 1. Target has 2 regions: R1 (0-100 bytes) and R2 (100-200 bytes). 2. Quota is configured to process only 100 bytes per window. 3. Window 1: Processes R1 (0-100). Quota is full. charge_{target, addr}_from is saved at (Target, 100). 4. Window 2: The loop reaches R2. Because R2 is damon_last_region(t), the old code unconditionally returns true, skipping R2 entirely and resetting the charge_{target,addr}_from. Result: R2 is permanently skipped even though it has never been processed. However, it is important to note that this is a very minor issue. This is because it is triggered only when the previous window saved/kept charge_{target,addr}_from, and in the next window, all regions except the last region were skipped by damos_skip_charged_region(). Fix this by only resetting the charge_{target,addr}_from when last region is reached, only skipping when it is applied or cannot split. Link: https://lore.kernel.org/20260908134739.96919-1-sj@kernel.org Fixes: 50585192bc2e ("mm/damon/schemes: skip already charged targets and regions") Signed-off-by: Liew Rui Yan Reviewed-by: SJ Park Signed-off-by: SJ Park Signed-off-by: Andrew Morton Cc: # v5.16.x diff --git a/mm/damon/core.c b/mm/damon/core.c index 2b294fb46648..06a253df8d4b 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -2342,36 +2342,39 @@ static bool damos_skip_charged_region(struct damon_target *t, { struct damos_quota *quota = &s->quota; unsigned long sz_to_skip; + bool skip = false; /* Skip previously charged regions */ if (quota->charge_target_from) { if (t != quota->charge_target_from) return true; - if (r == damon_last_region(t)) { - quota->charge_target_from = NULL; - quota->charge_addr_from = 0; - return true; - } if (quota->charge_addr_from && - r->ar.end <= quota->charge_addr_from) - return true; + r->ar.end <= quota->charge_addr_from) { + skip = true; + goto out; + } if (quota->charge_addr_from && r->ar.start < quota->charge_addr_from) { sz_to_skip = ALIGN_DOWN(quota->charge_addr_from - r->ar.start, min_region_sz); if (!sz_to_skip) { - if (damon_sz_region(r) <= min_region_sz) - return true; + if (damon_sz_region(r) <= min_region_sz) { + skip = true; + goto out; + } sz_to_skip = min_region_sz; } damon_split_region_at(t, r, sz_to_skip); - return true; + skip = true; } + } +out: + if (r == damon_last_region(t)) { quota->charge_target_from = NULL; quota->charge_addr_from = 0; } - return false; + return skip; } static void damos_update_stat(struct damos *s,