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=-5.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=ham 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 04A42C4360F for ; Mon, 18 Feb 2019 17:06:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BF166217D9 for ; Mon, 18 Feb 2019 17:06:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1550509564; bh=jkjMWOOKX58tCXXccyGbW+1i57yN5F4kf0V2C6P2cVc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=tpsVxGfLahcnvACUlL+2RD/t6z6Fy7Zg9QdgQpmIM9KqV/qoHV/HDSaAA29Nwde+W v33Cz0D7Klbdxl/GtLfW/THMjHroj4Q8t9EUkdy8pNA8nSbFI+kggNuNjT5kfEu5T2 uza0RA5FcztpahRmvspZ8gwgkcPCsrplGbWljFZo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390977AbfBRRGC (ORCPT ); Mon, 18 Feb 2019 12:06:02 -0500 Received: from mx2.suse.de ([195.135.220.15]:56424 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2387990AbfBRRGC (ORCPT ); Mon, 18 Feb 2019 12:06:02 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 7AA8EADD3; Mon, 18 Feb 2019 17:06:00 +0000 (UTC) Date: Mon, 18 Feb 2019 18:05:58 +0100 From: Michal Hocko To: Mike Rapoport Cc: Rong Chen , Pavel Tatashin , linux-kernel@vger.kernel.org, Linux Memory Management List , Andrew Morton , LKP , Oscar Salvador Subject: Re: [LKP] efad4e475c [ 40.308255] Oops: 0000 [#1] PREEMPT SMP PTI Message-ID: <20190218170558.GV4525@dhcp22.suse.cz> References: <20190218052823.GH29177@shao2-debian> <20190218070844.GC4525@dhcp22.suse.cz> <20190218085510.GC7251@dhcp22.suse.cz> <4c75d424-2c51-0d7d-5c28-78c15600e93c@intel.com> <20190218103013.GK4525@dhcp22.suse.cz> <20190218140515.GF25446@rapoport-lnx> <20190218152050.GS4525@dhcp22.suse.cz> <20190218152213.GT4525@dhcp22.suse.cz> <20190218164813.GG25446@rapoport-lnx> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190218164813.GG25446@rapoport-lnx> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 18-02-19 18:48:14, Mike Rapoport wrote: > On Mon, Feb 18, 2019 at 04:22:13PM +0100, Michal Hocko wrote: [...] > > Thinking about it some more, is it possible that we are overflowing by 1 > > here? > > Looks like that, the end_pfn is actually the first pfn in the next section. Thanks for the confirmation. I guess it also exaplains why nobody has noticed this off-by-one. Most people seem to use VMEMMAP SPARSE model and we are safe there. > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > > index 124e794867c5..6618b9d3e53a 100644 > > --- a/mm/memory_hotplug.c > > +++ b/mm/memory_hotplug.c > > @@ -1234,10 +1234,10 @@ bool is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages) > > { > > struct page *page = pfn_to_page(start_pfn); > > unsigned long end_pfn = min(start_pfn + nr_pages, zone_end_pfn(page_zone(page))); > > - struct page *end_page = pfn_to_page(end_pfn); > > + struct page *end_page = pfn_to_page(end_pfn - 1); > > > > /* Check the starting page of each pageblock within the range */ > > - for (; page < end_page; page = next_active_pageblock(page)) { > > + for (; page <= end_page; page = next_active_pageblock(page)) { > > if (!is_pageblock_removable_nolock(page)) > > return false; > > cond_resched(); > > Works with your fix, but I think mine is more intuitive ;-) I would rather go and rework this to pfns. What about this instead. Slightly larger but arguably cleared code? diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 124e794867c5..a799a0bdbf34 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1188,11 +1188,13 @@ static inline int pageblock_free(struct page *page) return PageBuddy(page) && page_order(page) >= pageblock_order; } -/* Return the start of the next active pageblock after a given page */ -static struct page *next_active_pageblock(struct page *page) +/* Return the pfn of the start of the next active pageblock after a given pfn */ +static unsigned long next_active_pageblock(unsigned long pfn) { + struct page *page = pfn_to_page(pfn); + /* Ensure the starting page is pageblock-aligned */ - BUG_ON(page_to_pfn(page) & (pageblock_nr_pages - 1)); + BUG_ON(pfn & (pageblock_nr_pages - 1)); /* If the entire pageblock is free, move to the end of free page */ if (pageblock_free(page)) { @@ -1200,16 +1202,16 @@ static struct page *next_active_pageblock(struct page *page) /* be careful. we don't have locks, page_order can be changed.*/ order = page_order(page); if ((order < MAX_ORDER) && (order >= pageblock_order)) - return page + (1 << order); + return pfn + (1 << order); } - return page + pageblock_nr_pages; + return pfn + pageblock_nr_pages; } -static bool is_pageblock_removable_nolock(struct page *page) +static bool is_pageblock_removable_nolock(unsigned long pfn) { + struct page *page = pfn_to_page(pfn); struct zone *zone; - unsigned long pfn; /* * We have to be careful here because we are iterating over memory @@ -1232,13 +1234,14 @@ static bool is_pageblock_removable_nolock(struct page *page) /* Checks if this range of memory is likely to be hot-removable. */ bool is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages) { - struct page *page = pfn_to_page(start_pfn); - unsigned long end_pfn = min(start_pfn + nr_pages, zone_end_pfn(page_zone(page))); - struct page *end_page = pfn_to_page(end_pfn); + unsigned long end_pfn; + + end_pfn = min(start_pfn + nr_pages, + zone_end_pfn(page_zone(pfn_to_page(start_pfn)))); /* Check the starting page of each pageblock within the range */ - for (; page < end_page; page = next_active_pageblock(page)) { - if (!is_pageblock_removable_nolock(page)) + for (; start_pfn < end_pfn; start_pfn = next_active_pageblock(start_pfn)) { + if (!is_pageblock_removable_nolock(start_pfn)) return false; cond_resched(); } -- Michal Hocko SUSE Labs From mboxrd@z Thu Jan 1 00:00:00 1970 Content-Type: multipart/mixed; boundary="===============0887080058609498762==" MIME-Version: 1.0 From: Michal Hocko To: lkp@lists.01.org Subject: Re: efad4e475c [ 40.308255] Oops: 0000 [#1] PREEMPT SMP PTI Date: Mon, 18 Feb 2019 18:05:58 +0100 Message-ID: <20190218170558.GV4525@dhcp22.suse.cz> In-Reply-To: <20190218164813.GG25446@rapoport-lnx> List-Id: --===============0887080058609498762== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable On Mon 18-02-19 18:48:14, Mike Rapoport wrote: > On Mon, Feb 18, 2019 at 04:22:13PM +0100, Michal Hocko wrote: [...] > > Thinking about it some more, is it possible that we are overflowing by 1 > > here? > = > Looks like that, the end_pfn is actually the first pfn in the next sectio= n. Thanks for the confirmation. I guess it also exaplains why nobody has noticed this off-by-one. Most people seem to use VMEMMAP SPARSE model and we are safe there. > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > > index 124e794867c5..6618b9d3e53a 100644 > > --- a/mm/memory_hotplug.c > > +++ b/mm/memory_hotplug.c > > @@ -1234,10 +1234,10 @@ bool is_mem_section_removable(unsigned long sta= rt_pfn, unsigned long nr_pages) > > { > > struct page *page =3D pfn_to_page(start_pfn); > > unsigned long end_pfn =3D min(start_pfn + nr_pages, zone_end_pfn(page= _zone(page))); > > - struct page *end_page =3D pfn_to_page(end_pfn); > > + struct page *end_page =3D pfn_to_page(end_pfn - 1); > > = > > /* Check the starting page of each pageblock within the range */ > > - for (; page < end_page; page =3D next_active_pageblock(page)) { > > + for (; page <=3D end_page; page =3D next_active_pageblock(page)) { > > if (!is_pageblock_removable_nolock(page)) > > return false; > > cond_resched(); > = > Works with your fix, but I think mine is more intuitive ;-) I would rather go and rework this to pfns. What about this instead. Slightly larger but arguably cleared code? diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 124e794867c5..a799a0bdbf34 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1188,11 +1188,13 @@ static inline int pageblock_free(struct page *page) return PageBuddy(page) && page_order(page) >=3D pageblock_order; } = -/* Return the start of the next active pageblock after a given page */ -static struct page *next_active_pageblock(struct page *page) +/* Return the pfn of the start of the next active pageblock after a given = pfn */ +static unsigned long next_active_pageblock(unsigned long pfn) { + struct page *page =3D pfn_to_page(pfn); + /* Ensure the starting page is pageblock-aligned */ - BUG_ON(page_to_pfn(page) & (pageblock_nr_pages - 1)); + BUG_ON(pfn & (pageblock_nr_pages - 1)); = /* If the entire pageblock is free, move to the end of free page */ if (pageblock_free(page)) { @@ -1200,16 +1202,16 @@ static struct page *next_active_pageblock(struct pa= ge *page) /* be careful. we don't have locks, page_order can be changed.*/ order =3D page_order(page); if ((order < MAX_ORDER) && (order >=3D pageblock_order)) - return page + (1 << order); + return pfn + (1 << order); } = - return page + pageblock_nr_pages; + return pfn + pageblock_nr_pages; } = -static bool is_pageblock_removable_nolock(struct page *page) +static bool is_pageblock_removable_nolock(unsigned long pfn) { + struct page *page =3D pfn_to_page(pfn); struct zone *zone; - unsigned long pfn; = /* * We have to be careful here because we are iterating over memory @@ -1232,13 +1234,14 @@ static bool is_pageblock_removable_nolock(struct pa= ge *page) /* Checks if this range of memory is likely to be hot-removable. */ bool is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pa= ges) { - struct page *page =3D pfn_to_page(start_pfn); - unsigned long end_pfn =3D min(start_pfn + nr_pages, zone_end_pfn(page_zon= e(page))); - struct page *end_page =3D pfn_to_page(end_pfn); + unsigned long end_pfn; + + end_pfn =3D min(start_pfn + nr_pages, + zone_end_pfn(page_zone(pfn_to_page(start_pfn)))); = /* Check the starting page of each pageblock within the range */ - for (; page < end_page; page =3D next_active_pageblock(page)) { - if (!is_pageblock_removable_nolock(page)) + for (; start_pfn < end_pfn; start_pfn =3D next_active_pageblock(start_pfn= )) { + if (!is_pageblock_removable_nolock(start_pfn)) return false; cond_resched(); } -- = Michal Hocko SUSE Labs --===============0887080058609498762==--