From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 92CB0C6FD1D for ; Fri, 7 Apr 2023 18:13:25 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D00276B0074; Fri, 7 Apr 2023 14:13:24 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id CB0BB900002; Fri, 7 Apr 2023 14:13:24 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B78CB6B0078; Fri, 7 Apr 2023 14:13:24 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id A1DFA6B0074 for ; Fri, 7 Apr 2023 14:13:24 -0400 (EDT) Received: from smtpin19.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id E903C120388 for ; Fri, 7 Apr 2023 18:03:39 +0000 (UTC) X-FDA: 80655367758.19.8339091 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf15.hostedemail.com (Postfix) with ESMTP id 3AA2BA0023 for ; Fri, 7 Apr 2023 18:03:38 +0000 (UTC) Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=bOGgaZo+; spf=pass (imf15.hostedemail.com: domain of rppt@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=none) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1680890618; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=xM4Wkps3g4rIAc+eTYo1Alveqdz54rBUU9jp3o8/ZGI=; b=YSk15cwL140UV0cEgQ+sFEeRnLInDHjMwGBFDvJ+WAmk0UAKyQSLYYgwXxODxCdiM5XA6J /AF/8SpOLLkgX0bZ2dK+qscSmcv8z+mk2U+rv+HNF9yD42UkBGnX84OX6Mlh/n3chK0vdd HcrKpO8KIIHhxDyrHjyHQCQDuyP7xGU= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=bOGgaZo+; spf=pass (imf15.hostedemail.com: domain of rppt@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=none) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1680890618; a=rsa-sha256; cv=none; b=V14sp9+tyhSfScVEXcDi8wLeLAYa861DFkwd5pum1fAlJbkDNyf/66u1H8USFZN5C3fs0L d9PScxGEcFwc7uLuYI5dNPvc5korlr6fnMj32EpJA9dhLAw6bEYg+LAwwSnF+ZoqDV5Ujy 2zQUXl3G542zmUwLkyMy5zbmbyau5PI= Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 1CDE264D5F; Fri, 7 Apr 2023 18:03:37 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A212BC433EF; Fri, 7 Apr 2023 18:03:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1680890616; bh=zeLvM+wG9Reg7GPWHX1rrEptBgIOs976gIhZ41Bbdos=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=bOGgaZo+OHVpjw84ut+dKEBX8kFMCYoAYvoqWCKJ+4sKeUDzoTpJFXWmNWDitx7Fz az/TmAIhaqK17Oq6C8Bg/3lHyHo9y8gco3TEVPnUjZH1tyucUpvdp2ILqKtfPrIwxm QnRv47iEtUSkXPWdL/GAlDpOPu07hs6MQcowF7tYX2ohpph3bbxrVIqbnr3Hsy56NO uK1YxKGwuZY6n36JWZOQquc5nKAJwrYfX5mtk7QXlms/euEEbz+c1a8MFZFQgJ6dZo dVf764QB+0TmW9RpbsMPNaA7inIOik2tT7UU3PO4JQmlKMm+rBHt8NxlmNQhWIY9L/ aI7IapTui+ybg== Date: Fri, 7 Apr 2023 21:03:24 +0300 From: Mike Rapoport To: "Kirill A. Shutemov" Cc: Andrew Morton , Guenter Roeck , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm-treewide-redefine-max_order-sanely-fix.txt Message-ID: References: <9460377a-38aa-4f39-ad57-fb73725f92db@roeck-us.net> <20230406072529.vupqyrzqnhyozeyh@box.shutemov.name> <83e6bc46-dfc0-0e95-e69c-5b996af1e50b@roeck-us.net> <20230406151015.yndcm24fyxitvqyc@box.shutemov.name> <20230406154423.20a991bbdd47630fc38d94e8@linux-foundation.org> <20230407124054.27iiers6o36pdfei@box.shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230407124054.27iiers6o36pdfei@box.shutemov.name> X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 3AA2BA0023 X-Stat-Signature: fcu5g9zi816tis5xxcb9m8ute9ju4g6q X-HE-Tag: 1680890618-165205 X-HE-Meta: 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 tRWs5rTd 8M6ILN3+T1jeDXvgmaHcHZIvmKL/2A7rrd5Opl8Y8ofu2KKmICBylH+KLu+yAU4Gm9C2MKQEJD6C4m2Tl75daJI+CGUlacH98uW6elWtCCvKP1UbWv38u+dMSi59bwZgYDwc3X6hJZKBw5wUVGml/5pP/J5prZP8oHNcAsz8Sl1EjvwGWsYCV3JM4hTwEL1CVjbEEw7HDXETFY5E/tR01G1+H0Utj2leV9HDSwjthlYDwLyc/X+lHqeOflij0n09S0bmmkynL3+RIeNPqvNWjOAKPj1j8DFnd1wkTWE0N7zu5uK5EUKQPq+QxcDRwFW6HjV7umiHl2bQbr0hQ032LWj64gY3wkI2FWD3RMQ8UKz4fgFnHjG8aDbeGs7qU4qAeyoRr8Tz7Y4jgdEdJO3Iepc6IwBvsmzhd6xyS X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Apr 07, 2023 at 03:40:54PM +0300, Kirill A. Shutemov wrote: > On Thu, Apr 06, 2023 at 03:44:23PM -0700, Andrew Morton wrote: > > On Fri, 7 Apr 2023 00:14:31 +0300 Mike Rapoport wrote: > > > > > > > Shouldn't that be > > > > > else > > > > > order = 0; > > > > > ? > > > > > > > > +Mike. > > > > > > > > No. start == 0 is MAX_ORDER-aligned. We want to free the pages in the > > > > largest chunks alignment allows. > > > > > > Right. Before the changes to MAX_ORDER it was > > > > > > order = min(MAX_ORDER - 1UL, __ffs(start)); > > > > > > which would evaluate to 10. > > > > > > I'd just prefer the comment to include the explanation about why we choose > > > MAX_ORDER for start == 0. Say > > > > > > /* > > > * __ffs() behaviour is undefined for 0 and we want to free the > > > * pages in the largest chunks alignment allows, so set order to > > > * MAX_ORDER when start == 0 > > > */ > > > > Meanwhile I'd like to fix "various boot failures (hang) on arm targets" > > in -next, so I queued up Kirill's informal fix for now. > > Here's my variant of the fix up with more vervose comments. > > diff --git a/mm/memblock.c b/mm/memblock.c > index 7911224b1ed3..381e36ac9e4d 100644 > --- a/mm/memblock.c > +++ b/mm/memblock.c > @@ -2043,7 +2043,16 @@ static void __init __free_pages_memory(unsigned long start, unsigned long end) > int order; > > while (start < end) { > - order = min_t(int, MAX_ORDER, __ffs(start)); > + /* > + * Free the pages in the largest chunks alignment allows. > + * > + * __ffs() behaviour is undefined for 0. start == 0 is > + * MAX_ORDER-aligned, Set order to MAX_ORDER for the case. ^ small s otherwise feel free to add Reviewed-by: Mike Rapoport (IBM) > + */ > + if (start) > + order = min_t(int, MAX_ORDER, __ffs(start)); > + else > + order = MAX_ORDER; > > while (start + (1UL << order) > end) > order--; > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index c8f0a8c2d049..8e0fa209d533 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -605,7 +605,18 @@ static void online_pages_range(unsigned long start_pfn, unsigned long nr_pages) > * this and the first chunk to online will be pageblock_nr_pages. > */ > for (pfn = start_pfn; pfn < end_pfn;) { > - int order = min_t(int, MAX_ORDER, __ffs(pfn)); > + int order; > + > + /* > + * Free to online pages in the largest chunks alignment allows. > + * > + * __ffs() behaviour is undefined for 0. start == 0 is > + * MAX_ORDER-aligned, Set order to MAX_ORDER for the case. > + */ > + if (pfn) > + order = min_t(int, MAX_ORDER, __ffs(pfn)); > + else > + order = MAX_ORDER; > > (*online_page_callback)(pfn_to_page(pfn), order); > pfn += (1UL << order); > -- > Kiryl Shutsemau / Kirill A. Shutemov -- Sincerely yours, Mike.