From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt1-f200.google.com (mail-qt1-f200.google.com [209.85.160.200]) by kanga.kvack.org (Postfix) with ESMTP id BB42F8E01DC for ; Fri, 14 Dec 2018 10:22:14 -0500 (EST) Received: by mail-qt1-f200.google.com with SMTP id w1so5339011qta.12 for ; Fri, 14 Dec 2018 07:22:14 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id i6si677918qvr.198.2018.12.14.07.22.13 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 14 Dec 2018 07:22:13 -0800 (PST) Subject: Re: [PATCH v2 1/1] mm, memory_hotplug: Initialize struct pages for the full memory section References: <20181212172712.34019-1-zaslonko@linux.ibm.com> <20181212172712.34019-2-zaslonko@linux.ibm.com> From: David Hildenbrand Message-ID: <476a80cb-5524-16c1-6dd5-da5febbd6139@redhat.com> Date: Fri, 14 Dec 2018 16:22:09 +0100 MIME-Version: 1.0 In-Reply-To: <20181212172712.34019-2-zaslonko@linux.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Mikhail Zaslonko , akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, mhocko@kernel.org, Pavel.Tatashin@microsoft.com, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, gerald.schaefer@de.ibm.com On 12.12.18 18:27, Mikhail Zaslonko wrote: > If memory end is not aligned with the sparse memory section boundary, the > mapping of such a section is only partly initialized. This may lead to > VM_BUG_ON due to uninitialized struct page access from > is_mem_section_removable() or test_pages_in_a_zone() function triggered by > memory_hotplug sysfs handlers: > > Here are the the panic examples: > CONFIG_DEBUG_VM=y > CONFIG_DEBUG_VM_PGFLAGS=y > > kernel parameter mem=2050M > -------------------------- > page:000003d082008000 is uninitialized and poisoned > page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) > Call Trace: > ([<0000000000385b26>] test_pages_in_a_zone+0xde/0x160) > [<00000000008f15c4>] show_valid_zones+0x5c/0x190 > [<00000000008cf9c4>] dev_attr_show+0x34/0x70 > [<0000000000463ad0>] sysfs_kf_seq_show+0xc8/0x148 > [<00000000003e4194>] seq_read+0x204/0x480 > [<00000000003b53ea>] __vfs_read+0x32/0x178 > [<00000000003b55b2>] vfs_read+0x82/0x138 > [<00000000003b5be2>] ksys_read+0x5a/0xb0 > [<0000000000b86ba0>] system_call+0xdc/0x2d8 > Last Breaking-Event-Address: > [<0000000000385b26>] test_pages_in_a_zone+0xde/0x160 > Kernel panic - not syncing: Fatal exception: panic_on_oops > > kernel parameter mem=3075M > -------------------------- > page:000003d08300c000 is uninitialized and poisoned > page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) > Call Trace: > ([<000000000038596c>] is_mem_section_removable+0xb4/0x190) > [<00000000008f12fa>] show_mem_removable+0x9a/0xd8 > [<00000000008cf9c4>] dev_attr_show+0x34/0x70 > [<0000000000463ad0>] sysfs_kf_seq_show+0xc8/0x148 > [<00000000003e4194>] seq_read+0x204/0x480 > [<00000000003b53ea>] __vfs_read+0x32/0x178 > [<00000000003b55b2>] vfs_read+0x82/0x138 > [<00000000003b5be2>] ksys_read+0x5a/0xb0 > [<0000000000b86ba0>] system_call+0xdc/0x2d8 > Last Breaking-Event-Address: > [<000000000038596c>] is_mem_section_removable+0xb4/0x190 > Kernel panic - not syncing: Fatal exception: panic_on_oops > > Fix the problem by initializing the last memory section of each zone > in memmap_init_zone() till the very end, even if it goes beyond the zone > end. > > Signed-off-by: Mikhail Zaslonko > Reviewed-by: Gerald Schaefer > Cc: > --- > mm/page_alloc.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 2ec9cc407216..e2afdb2dc2c5 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -5542,6 +5542,18 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone, > cond_resched(); > } > } > +#ifdef CONFIG_SPARSEMEM > + /* > + * If the zone does not span the rest of the section then > + * we should at least initialize those pages. Otherwise we > + * could blow up on a poisoned page in some paths which depend > + * on full sections being initialized (e.g. memory hotplug). > + */ > + while (end_pfn % PAGES_PER_SECTION) { > + __init_single_page(pfn_to_page(end_pfn), end_pfn, zone, nid); > + end_pfn++; This page will not be marked as PG_reserved - although it is a physical memory gap. Do we care? > + } > +#endif > } > > #ifdef CONFIG_ZONE_DEVICE > -- Thanks, David / dhildenb