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 X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0DF5EC43460 for ; Tue, 20 Apr 2021 09:40:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C016B613B0 for ; Tue, 20 Apr 2021 09:40:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231372AbhDTJlY (ORCPT ); Tue, 20 Apr 2021 05:41:24 -0400 Received: from mx2.suse.de ([195.135.220.15]:44450 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229937AbhDTJlW (ORCPT ); Tue, 20 Apr 2021 05:41:22 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1618911650; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ISg7e+JkeB3CvE9TQuR+dfKDLHA8lmXq7TDVEpR7Mgo=; b=HWPmlZftGFx3CKPVNnHNN7B+CMURDvW8o3b4OwaFx+MWuH0085ACoaFfmdFfTjWlg2VF4R dbOPdLFj5UUxOX0c+LbS6OvuMBum6FoOIJbMJ00zDKqn8J+2CX+Mi1rDaOD3vhn/MT2q+0 NE0St2D23IYhN0sxI7mNnyexRVmnCOw= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id BC42BAC3E; Tue, 20 Apr 2021 09:40:50 +0000 (UTC) Date: Tue, 20 Apr 2021 11:40:50 +0200 From: Michal Hocko To: Oscar Salvador Cc: Andrew Morton , David Hildenbrand , Anshuman Khandual , Pavel Tatashin , Vlastimil Babka , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v9 2/8] mm,memory_hotplug: Relax fully spanned sections check Message-ID: References: <20210416112411.9826-1-osalvador@suse.de> <20210416112411.9826-3-osalvador@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210416112411.9826-3-osalvador@suse.de> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 16-04-21 13:24:05, Oscar Salvador wrote: > When using self-hosted vmemmap pages, the number of pages passed to > {online,offline}_pages might not fully span sections, but they always > fully span pageblocks. > Relax the check account for that case. It would be good to call those out explicitly. It would be also great to explain why pageblock_nr_pages is an actual constrain. There shouldn't be any real reason for that except for "we want online_pages to operate on whole memblocks and memmap_on_memory will poke pageblock_nr_pages aligned holes in the beginning which is a special case we want to allow." > Signed-off-by: Oscar Salvador > Reviewed-by: David Hildenbrand With the changelog extended and the comment clarification (se below) feel free to add Acked-by: Michal Hocko > --- > mm/memory_hotplug.c | 18 ++++++++++++++---- > 1 file changed, 14 insertions(+), 4 deletions(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 0cdbbfbc5757..25e59d5dc13c 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -838,9 +838,14 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, > int ret; > struct memory_notify arg; > > - /* We can only online full sections (e.g., SECTION_IS_ONLINE) */ > + /* We can only offline full sections (e.g., SECTION_IS_ONLINE). > + * However, when using e.g: memmap_on_memory, some pages are initialized > + * prior to calling in here. The remaining amount of pages must be > + * pageblock aligned. I would rephrase (and also note that multi line comment usually have a leading line without any content - not that I care much though). /* * {on,off}lining is constrained to full memory sections (or * more precisly to memory blocks from the user space POV). * memmap_on_memory is an exception because it reserves initial * part of the physical memory space for vmemmaps. That space is * pageblock aligned. > + */ Same comment would apply to oofline_pages. > if (WARN_ON_ONCE(!nr_pages || > - !IS_ALIGNED(pfn | nr_pages, PAGES_PER_SECTION))) > + !IS_ALIGNED(pfn, pageblock_nr_pages) || > + !IS_ALIGNED(pfn + nr_pages, PAGES_PER_SECTION))) > return -EINVAL; > > mem_hotplug_begin(); > @@ -1573,9 +1578,14 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages) > int ret, node; > char *reason; > > - /* We can only offline full sections (e.g., SECTION_IS_ONLINE) */ > + /* We can only offline full sections (e.g., SECTION_IS_ONLINE). > + * However, when using e.g: memmap_on_memory, some pages are initialized > + * prior to calling in here. The remaining amount of pages must be > + * pageblock aligned. > + */ > if (WARN_ON_ONCE(!nr_pages || > - !IS_ALIGNED(start_pfn | nr_pages, PAGES_PER_SECTION))) > + !IS_ALIGNED(start_pfn, pageblock_nr_pages) || > + !IS_ALIGNED(start_pfn + nr_pages, PAGES_PER_SECTION))) > return -EINVAL; > > mem_hotplug_begin(); > -- > 2.16.3 -- Michal Hocko SUSE Labs