From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751532AbeCNWx3 (ORCPT ); Wed, 14 Mar 2018 18:53:29 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:33740 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750779AbeCNWx2 (ORCPT ); Wed, 14 Mar 2018 18:53:28 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 2330E603AF Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=shankerd@codeaurora.org Reply-To: shankerd@codeaurora.org Subject: Re: [PATCH v2] Revert "mm/page_alloc: fix memmap_init_zone pageblock alignment" To: Jan Glauber , Ard Biesheuvel Cc: mark.rutland@arm.com, Michal Hocko , Mel Gorman , Paul Burton , marc.zyngier@arm.com, catalin.marinas@arm.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, Pavel Tatashin , Vlastimil Babka , Andrew Morton , Linus Torvalds , Daniel Vacek , linux-arm-kernel@lists.infradead.org References: <20180314192937.12888-1-ard.biesheuvel@linaro.org> <20180314222530.GA6300@wintermute> From: Shanker Donthineni Message-ID: <4c31c5ed-9f68-10c3-c73f-5b6f34dd82c9@codeaurora.org> Date: Wed, 14 Mar 2018 17:53:03 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.0 MIME-Version: 1.0 In-Reply-To: <20180314222530.GA6300@wintermute> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Ard, On 03/14/2018 05:25 PM, Jan Glauber wrote: > On Wed, Mar 14, 2018 at 07:29:37PM +0000, Ard Biesheuvel wrote: >> This reverts commit 864b75f9d6b0100bb24fdd9a20d156e7cda9b5ae. > > FWIW, the revert fixes the boot hang I'm seeing on ThunderX1. > > --Jan > Thanks for this patch, it fixes the boot hang on QDF2400 platform. >> Commit 864b75f9d6b0 ("mm/page_alloc: fix memmap_init_zone pageblock >> alignment") modified the logic in memmap_init_zone() to initialize >> struct pages associated with invalid PFNs, to appease a VM_BUG_ON() >> in move_freepages(), which is redundant by its own admission, and >> dereferences struct page fields to obtain the zone without checking >> whether the struct pages in question are valid to begin with. >> >> Commit 864b75f9d6b0 only makes it worse, since the rounding it does >> may cause pfn assume the same value it had in a prior iteration of >> the loop, resulting in an infinite loop and a hang very early in the >> boot. Also, since it doesn't perform the same rounding on start_pfn >> itself but only on intermediate values following an invalid PFN, we >> may still hit the same VM_BUG_ON() as before. >> >> So instead, let's fix this at the core, and ensure that the BUG >> check doesn't dereference struct page fields of invalid pages. >> >> Fixes: 864b75f9d6b0 ("mm/page_alloc: fix memmap_init_zone pageblock alignment") >> Cc: Daniel Vacek >> Cc: Mel Gorman >> Cc: Michal Hocko >> Cc: Paul Burton >> Cc: Pavel Tatashin >> Cc: Vlastimil Babka >> Cc: Andrew Morton >> Cc: Linus Torvalds >> Signed-off-by: Ard Biesheuvel >> --- >> mm/page_alloc.c | 13 +++++-------- >> 1 file changed, 5 insertions(+), 8 deletions(-) >> >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index 3d974cb2a1a1..635d7dd29d7f 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -1910,7 +1910,9 @@ static int move_freepages(struct zone *zone, >> * Remove at a later date when no bug reports exist related to >> * grouping pages by mobility >> */ >> - VM_BUG_ON(page_zone(start_page) != page_zone(end_page)); >> + VM_BUG_ON(pfn_valid(page_to_pfn(start_page)) && >> + pfn_valid(page_to_pfn(end_page)) && >> + page_zone(start_page) != page_zone(end_page)); >> #endif >> >> if (num_movable) >> @@ -5359,14 +5361,9 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone, >> /* >> * Skip to the pfn preceding the next valid one (or >> * end_pfn), such that we hit a valid pfn (or end_pfn) >> - * on our next iteration of the loop. Note that it needs >> - * to be pageblock aligned even when the region itself >> - * is not. move_freepages_block() can shift ahead of >> - * the valid region but still depends on correct page >> - * metadata. >> + * on our next iteration of the loop. >> */ >> - pfn = (memblock_next_valid_pfn(pfn, end_pfn) & >> - ~(pageblock_nr_pages-1)) - 1; >> + pfn = memblock_next_valid_pfn(pfn, end_pfn) - 1; >> #endif >> continue; >> } >> -- >> 2.15.1 >> >> >> _______________________________________________ >> linux-arm-kernel mailing list >> linux-arm-kernel@lists.infradead.org >> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > -- Shanker Donthineni Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.