From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f70.google.com (mail-ed1-f70.google.com [209.85.208.70]) by kanga.kvack.org (Postfix) with ESMTP id 3D9E28E0018 for ; Mon, 10 Dec 2018 10:10:08 -0500 (EST) Received: by mail-ed1-f70.google.com with SMTP id e12so5448327edd.16 for ; Mon, 10 Dec 2018 07:10:08 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id e28sor6438092edb.24.2018.12.10.07.10.06 for (Google Transport Security); Mon, 10 Dec 2018 07:10:06 -0800 (PST) Date: Mon, 10 Dec 2018 15:10:05 +0000 From: Wei Yang Subject: Re: [PATCH 1/1] mm, memory_hotplug: Initialize struct pages for the full memory section Message-ID: <20181210151005.xukiibwbb6ohqyex@master> Reply-To: Wei Yang References: <20181210130712.30148-1-zaslonko@linux.ibm.com> <20181210130712.30148-2-zaslonko@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181210130712.30148-2-zaslonko@linux.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Mikhail Zaslonko Cc: akpm@linux-foundation.org, 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 Mon, Dec 10, 2018 at 02:07:12PM +0100, 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: > > 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 > >Fix the problem by initializing the last memory section of the highest 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 | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) > >diff --git a/mm/page_alloc.c b/mm/page_alloc.c >index 2ec9cc407216..41ef5508e5f1 100644 >--- a/mm/page_alloc.c >+++ b/mm/page_alloc.c >@@ -5542,6 +5542,21 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone, > cond_resched(); > } > } >+#ifdef CONFIG_SPARSEMEM >+ /* >+ * If there is no zone spanning 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). >+ */ >+ if (end_pfn == max_pfn) { >+ while (end_pfn % PAGES_PER_SECTION) { >+ __init_single_page(pfn_to_page(end_pfn), end_pfn, zone, >+ nid); >+ end_pfn++; >+ } >+ } >+#endif If my understanding is correct, end_pfn is not a valid range. memmap_init_zone() initialize the range [start_pfn, start_pfn + size). I am afraid this will break the syntax. And max_pfn is also not a valid one. For example, on x86, update_end_of_memory_vars() will update max_pfn, which is calculated by: end_pfn = PFN_UP(start + size); BTW, as you mentioned this apply to hotplug case. And then why this couldn't happen during boot up? What differ these two cases? > } > > #ifdef CONFIG_ZONE_DEVICE >-- >2.16.4 -- Wei Yang Help you, Help me