From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from fra-out-005.esa.eu-central-1.outbound.mail-perimeter.amazon.com (fra-out-005.esa.eu-central-1.outbound.mail-perimeter.amazon.com [63.176.194.123]) (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 9485C19D082; Fri, 19 Sep 2025 10:25:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=63.176.194.123 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758277507; cv=none; b=UHK7PcsOACDhD8IwWF1Aqp4QTI0FhfRovBGKJ7x6OCKlQ1WnPVPdu5lrYMoYGQwtYkTCi49DsHX75zckTBMzHHK/t7EGsNIdrOfnx4zGWEu5DHnJUlhw6MVOYrKRGHX2rmFWILkUmJ/LoLZD23S2WXY7VrYIfvXEwN9VGb0+Qhg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758277507; c=relaxed/simple; bh=c8CkUW1Wymk66rGG5tsvWtIDgSEWGpXx8+69cD8zAvI=; h=From:To:CC:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=pG5A/IAHB1flgfhWK5gHpvzOwZ15GYBndrywP5GwcESJo39uO0FNEzBsvCP8ra0Y6TuNQh69mDyqU4KZUL4CYzBbM44RC3plgMk48a0lbhJOpVZIV7xLa0WS6eYrpg3USOj2ZFzk0XxXFY479sVee5zMODCoxq8HXCvyrineVzI= 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=OVm1uqNE; arc=none smtp.client-ip=63.176.194.123 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="OVm1uqNE" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazoncorp2; t=1758277505; x=1789813505; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=jvk2RBzXwrA99Hwxay/jSQlk3gLjsVti9lJHvH/pTPQ=; b=OVm1uqNEcstaTE1GbiRT/wjPblh3TlHxwxnmBT+s6i5oe7RFCgvODFMk lXYhppV48ErKvoGJ66OMATMp01A2nWiF2sYhOC4TdslnfLJn3clybVSxp 2fCnxAVPT8Kb4xYDjxtm6oZZhyddMfkEUa/SlK9QvhatQtx8rleDarcfn MsofHnL03orN+q2f1k2pU+m9bUUJdtgJUt3mBIKT6x5e8U4fFGHZguv8s a0S4qrx/aXCbBTor+X3K0C5wVufhnicdD6atFppu9Ls8piOZX1Qm8ZD1y VNE6LEapKU+Bbw+l4bmgv9fYnDARbIjbY89hxd9dj0itWESyl6n56yJzu A==; X-CSE-ConnectionGUID: KANou9z1RuCe6Vq68KMQTw== X-CSE-MsgGUID: TbLofDk1S/CNyVlnEY1GAw== X-IronPort-AV: E=Sophos;i="6.18,277,1751241600"; d="scan'208";a="2369395" Received: from ip-10-6-6-97.eu-central-1.compute.internal (HELO smtpout.naws.eu-central-1.prod.farcaster.email.amazon.dev) ([10.6.6.97]) by internal-fra-out-005.esa.eu-central-1.outbound.mail-perimeter.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Sep 2025 10:25:03 +0000 Received: from EX19MTAEUA001.ant.amazon.com [54.240.197.233:30717] by smtpin.naws.eu-central-1.prod.farcaster.email.amazon.dev [10.0.30.197:2525] with esmtp (Farcaster) id 083ec295-c61b-4097-9a92-62dae0cb35b4; Fri, 19 Sep 2025 10:25:02 +0000 (UTC) X-Farcaster-Flow-ID: 083ec295-c61b-4097-9a92-62dae0cb35b4 Received: from EX19D018EUA004.ant.amazon.com (10.252.50.85) by EX19MTAEUA001.ant.amazon.com (10.252.50.192) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.2562.20; Fri, 19 Sep 2025 10:25:02 +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; Fri, 19 Sep 2025 10:24:33 +0000 From: Eliav Farber To: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , CC: , Linus Torvalds , Lorenzo Stoakes , David Laight Subject: [PATCH 12/27 5.10.y] minmax: avoid overly complicated constant expressions in VM code Date: Fri, 19 Sep 2025 10:17:12 +0000 Message-ID: <20250919101727.16152-13-farbere@amazon.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20250919101727.16152-1-farbere@amazon.com> References: <20250919101727.16152-1-farbere@amazon.com> Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: EX19D035UWB004.ant.amazon.com (10.13.138.104) 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