From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from fra-out-009.esa.eu-central-1.outbound.mail-perimeter.amazon.com (fra-out-009.esa.eu-central-1.outbound.mail-perimeter.amazon.com [3.64.237.68]) (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 66ABF2820B9; Thu, 2 Oct 2025 20:50:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=3.64.237.68 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759438242; cv=none; b=K2ehH1bmFtz7TBr7y18CcuRbKdw6QKlemhdStNU0yEG3Z8kUFki1xjZqUD485sgG/Gds9+BgbZ5FARQi98I+WSa0rVItYNAqyrsriN9X8lTyu5icoOEDMtXw+3fyTNb82ZxkWUNTApAO499p1uogUbQZHB+mFRzn4OPnubhFMsc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759438242; c=relaxed/simple; bh=c8CkUW1Wymk66rGG5tsvWtIDgSEWGpXx8+69cD8zAvI=; h=From:To:CC:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=pmNvWJzLaq84/5UaV2XLyhLEyK6ZDPPxOQBQ/1A45qcO/3rU7H4L/R7P0NZDLnzYLRO7uHwcJSjqqeDkO29BZ132KtnYjgGiEnTuPzeD+/LOIa2k1CEmoY28847mIhiU06Jyg5NZOWbaZeb6bnRW4M+5lfiUSjuW6eqqYXPBQVA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.com; spf=pass smtp.mailfrom=amazon.com; dkim=pass (2048-bit key) header.d=amazon.com header.i=@amazon.com header.b=XlTKcyjh; arc=none smtp.client-ip=3.64.237.68 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=amazon.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=amazon.com header.i=@amazon.com header.b="XlTKcyjh" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazoncorp2; t=1759438240; x=1790974240; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=jvk2RBzXwrA99Hwxay/jSQlk3gLjsVti9lJHvH/pTPQ=; b=XlTKcyjhHEM3qadO6wWF4n1TU0Wpi3hIqUjpRIJUrY0reVs1oEauFDME 3QiGr3CG33HSzXQB91Gp+NHGe+Q96muu0mThKmagGg+guntoMA49pa1iJ D1XOLbERnZk9C5e3ysnevYjrM4qmB/0isCGecufpMq20/UZx7NueyAYQA yrs0sLUpIUkvI7buSclEeMXolW50sAUt75aplo40ZtZK+xbfH5+usCDaW S3rUUV28cup/KMEYVseZOK99c1dIE6Kp8V0elXY+exJ4976gE4IvPX5HZ 8cDS1i5CQFB7sxywcX4zSy/K8LHd1krTWSFAgOU7vRuMagGHKPzpU/Okw A==; X-CSE-ConnectionGUID: YiAweu1YTFWm7gL7sAM34g== X-CSE-MsgGUID: cPMixKcNRUaFt+r0RIS6uw== X-IronPort-AV: E=Sophos;i="6.18,310,1751241600"; d="scan'208";a="2929522" Received: from ip-10-6-11-83.eu-central-1.compute.internal (HELO smtpout.naws.eu-central-1.prod.farcaster.email.amazon.dev) ([10.6.11.83]) by internal-fra-out-009.esa.eu-central-1.outbound.mail-perimeter.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Oct 2025 20:50:28 +0000 Received: from EX19MTAEUC001.ant.amazon.com [54.240.197.225:22450] by smtpin.naws.eu-central-1.prod.farcaster.email.amazon.dev [10.0.22.27:2525] with esmtp (Farcaster) id 8269f201-c56b-4da0-ad37-545a7d678908; Thu, 2 Oct 2025 20:50:27 +0000 (UTC) X-Farcaster-Flow-ID: 8269f201-c56b-4da0-ad37-545a7d678908 Received: from EX19D018EUA004.ant.amazon.com (10.252.50.85) by EX19MTAEUC001.ant.amazon.com (10.252.51.155) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.20; Thu, 2 Oct 2025 20:50:26 +0000 Received: from dev-dsk-farbere-1a-46ecabed.eu-west-1.amazon.com (172.19.116.181) by EX19D018EUA004.ant.amazon.com (10.252.50.85) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.20; Thu, 2 Oct 2025 20:50:00 +0000 From: Eliav Farber To: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , CC: Linus Torvalds , Lorenzo Stoakes , David Laight Subject: [PATCH 05/19 5.15.y] minmax: avoid overly complicated constant expressions in VM code Date: Thu, 2 Oct 2025 20:47:19 +0000 Message-ID: <20251002204733.35652-6-farbere@amazon.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20251002204733.35652-1-farbere@amazon.com> References: <20251002204733.35652-1-farbere@amazon.com> Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: EX19D035UWA001.ant.amazon.com (10.13.139.101) To EX19D018EUA004.ant.amazon.com (10.252.50.85) From: Linus Torvalds [ Upstream commit 3a7e02c040b130b5545e4b115aada7bacd80a2b6 ] The minmax infrastructure is overkill for simple constants, and can cause huge expansions because those simple constants are then used by other things. For example, 'pageblock_order' is a core VM constant, but because it was implemented using 'min_t()' and all the type-checking that involves, it actually expanded to something like 2.5kB of preprocessor noise. And when that simple constant was then used inside other expansions: #define pageblock_nr_pages (1UL << pageblock_order) #define pageblock_start_pfn(pfn) ALIGN_DOWN((pfn), pageblock_nr_pages) and we then use that inside a 'max()' macro: case ISOLATE_SUCCESS: update_cached = false; last_migrated_pfn = max(cc->zone->zone_start_pfn, pageblock_start_pfn(cc->migrate_pfn - 1)); the end result was that one statement expanding to 253kB in size. There are probably other cases of this, but this one case certainly stood out. I've added 'MIN_T()' and 'MAX_T()' macros for this kind of "core simple constant with specific type" use. These macros skip the type checking, and as such need to be very sparingly used only for obvious cases that have active issues like this. Reported-by: Lorenzo Stoakes Link: https://lore.kernel.org/all/36aa2cad-1db1-4abf-8dd2-fb20484aabc3@lucifer.local/ Cc: David Laight Signed-off-by: Linus Torvalds Signed-off-by: Eliav Farber --- include/linux/minmax.h | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/include/linux/minmax.h b/include/linux/minmax.h index 2ec559284a9f..a7ef65f78933 100644 --- a/include/linux/minmax.h +++ b/include/linux/minmax.h @@ -270,4 +270,11 @@ static inline bool in_range32(u32 val, u32 start, u32 len) #define swap(a, b) \ do { typeof(a) __tmp = (a); (a) = (b); (b) = __tmp; } while (0) +/* + * Use these carefully: no type checking, and uses the arguments + * multiple times. Use for obvious constants only. + */ +#define MIN_T(type,a,b) __cmp(min,(type)(a),(type)(b)) +#define MAX_T(type,a,b) __cmp(max,(type)(a),(type)(b)) + #endif /* _LINUX_MINMAX_H */ -- 2.47.3