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=-9.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_NEOMUTT 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 7D7C0C65BAE for ; Thu, 13 Dec 2018 15:12:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 409A02087F for ; Thu, 13 Dec 2018 15:12:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="ifO42s1S" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 409A02087F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729305AbeLMPMO (ORCPT ); Thu, 13 Dec 2018 10:12:14 -0500 Received: from mail-ed1-f68.google.com ([209.85.208.68]:42427 "EHLO mail-ed1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727618AbeLMPMN (ORCPT ); Thu, 13 Dec 2018 10:12:13 -0500 Received: by mail-ed1-f68.google.com with SMTP id j6so2290830edp.9 for ; Thu, 13 Dec 2018 07:12:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:reply-to:references:mime-version :content-disposition:in-reply-to:user-agent; bh=l69N32jmQG2zGN93tkn7NJvUX29xf66d+hF+/Qin/d8=; b=ifO42s1SwvAZ39OUs/6duMDQkzexKmBgUl5UhVqJp2Yc2D3UP3PYijgXyqcG99hvit fvXkHTGUDjIn4r0eN3rcceZ16SPTRIBTI/brsTy2ehb1LcR/MGu7VFeQiZ87O9cnsJ5D UfPR35tGu9g9hJFekDgLHf0FuMKKCtkhzDxGjDJsOMSLQN/hjAhlTtTA4b0AoWCiaCdB CSwSdXr421dgP0Nzo2MSm7vDqnLZLm2Mne4lvq2lohnNPCQHnRopH1eaH5Z2+E5BdGXa jcroCtTTvwmRWzlpKmgIZX8XW5fe66NSVAICqsGw1pKPD7Y9uscofQAQBsltWwFcnx9D kRaQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:reply-to :references:mime-version:content-disposition:in-reply-to:user-agent; bh=l69N32jmQG2zGN93tkn7NJvUX29xf66d+hF+/Qin/d8=; b=laWpocd6/boj5BRVQOuIHONw09sxdAgnillmni/g3suTs6vp3kn1XgQDwmicJRQlbu PqOZ+iwpmjyGYCJcDfi5YZ3eXpuvt3C1OiE5vifzYkI7hXNmAY3PdSHlTYeNzAoUQoL3 nvGzsjBL15iLw5VJ4u5f+s2lkVOaHTgH9FoPXg5Y4bifaMxyBySGwdmWjFeFngecWUPG QNQreV0Tho5A2kXQQxW3Vkif4sdqcQTZMou+6jWj9VqNQhHuHjJN9f3Q4ZoD/QfCrp7z 8pL6hOebs7Q2B64frPmcW6Cg1s3jFp8+Az2meCa+KamMhcfbn6QGheT7+8TT4deNH7Aw mhcw== X-Gm-Message-State: AA+aEWbK2L8lGOllzllkPmVD4JGxtDsnfvr+bePZOeTAO3o4nn6Drm3t gh4i+/696NjR3KJFy9WZ/PA= X-Google-Smtp-Source: AFSGD/USy8N9p1bdi6RLTHnkkBby299W73REWFxbklgRRQ8QR+PsvFHhncCH1bjRbtHOc6iTWYnu8g== X-Received: by 2002:a50:9f64:: with SMTP id b91mr22462900edf.235.1544713931234; Thu, 13 Dec 2018 07:12:11 -0800 (PST) Received: from localhost ([185.92.221.13]) by smtp.gmail.com with ESMTPSA id v14sm630587edq.74.2018.12.13.07.12.10 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 13 Dec 2018 07:12:10 -0800 (PST) Date: Thu, 13 Dec 2018 15:12:09 +0000 From: Wei Yang To: Zaslonko Mikhail Cc: Wei Yang , Mikhail Zaslonko , 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 Subject: Re: [PATCH v2 1/1] mm, memory_hotplug: Initialize struct pages for the full memory section Message-ID: <20181213151209.hmrhrr5gvb256bzm@master> Reply-To: Wei Yang References: <20181212172712.34019-1-zaslonko@linux.ibm.com> <20181212172712.34019-2-zaslonko@linux.ibm.com> <20181213034615.4ntpo4cl2oo5mcx4@master> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 13, 2018 at 01:37:16PM +0100, Zaslonko Mikhail wrote: >On 13.12.2018 04:46, Wei Yang wrote: >> On Wed, Dec 12, 2018 at 06:27:12PM +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: >>> >>> 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++; >>> + } >>> +#endif >>> } >> >> What will happen if the end_pfn is PAGES_PER_SECTION aligned, but there >> is invalid pfn? For example, the page is skipped in the for loop of >> memmap_init_zone()? >> > >If the end_pfn is PAGES_PER_SECTION aligned, we do not do any extra >initialization. >If the page is skipped in the loop, it will remain uninitialized for >the reason (e.g. a memory hole). The behavior has not been changed here. > I may not describe my question clearly. If the page is skipped, then it is uninitialized. Then would this page trigger the call trace when read the removable sysfs? >>> >>> #ifdef CONFIG_ZONE_DEVICE >>> -- >>> 2.16.4 >> -- Wei Yang Help you, Help me