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 B651E4F4049; Wed, 30 Sep 2026 17:01:18 +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=1790787679; cv=none; b=hyNjVe1wuuWqup5v94r74yVq70Un6VnZH8f107Ghose9i9glnHLaBtf6RLgHlcjcJDzj1MUfVxLuZfPMoMakNeRLZHntxPmHjRlMgaWeNb21oRErgyWdfBgYTfO4QUVrjb5h81QIj7bRd42UIrMG1Mz/wERkJZhBWB8BC5WVb+k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790787679; c=relaxed/simple; bh=DqZnEifAKAWILRGLOxk7gtsuGBOnjhU7zmmp/FThGCM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=fkeHpN9eQ1/37l8iQbRpT7vnjScoDKCeq+J62mwIypyFn9YoyIvCj3x71B/8M8m/oBLS5EodhE2/YuBcJtyZZjt6KmbIgB4rsAk/zFNlxiPXT1247hVbylrYndMnlVO+COl+hVzFQ4vCtFoctscksmxDWksHCM8o7wm+uKGitYk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=cG64V52x; 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="cG64V52x" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1D4EA1F000FF; Wed, 30 Sep 2026 17:01:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790787678; bh=y7o0zhpm4CdN6yulLg75hB/FNnAKYrVUBIhdoIMsu3w=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=cG64V52xkvh3O5FtArNRCiZtz0xtsidvNS1LDZQPXFCY5M6QfQ4H52NJaM023CWP+ +KGGO1WUQxPmFFxGDg6d4uClTX65WtNkfan39LfReJEyjeOJ4a+Lbd4Yxx3rqJfBGk EYVLU7QG5SyV7VRtVyugQuPJKGGQF0rEBTEVl7wo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Liew Rui Yan , SJ Park , Andrew Morton Subject: [PATCH 7.2 316/457] mm/damon/core: fix unconditionally skip last region Date: Wed, 30 Sep 2026 17:27:01 +0200 Message-ID: <20260930152352.844493691@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152346.024115587@linuxfoundation.org> References: <20260930152346.024115587@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Liew Rui Yan commit b3723b596b548c837a766aae3553c14a7b15af2b upstream. 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 Signed-off-by: Greg Kroah-Hartman --- mm/damon/core.c | 25 ++++++++++++++----------- 1 file changed, 14 insertions(+), 11 deletions(-) --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -2145,36 +2145,39 @@ static bool damos_skip_charged_region(st { 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,