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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 EB83EC11D2B for ; Mon, 24 Feb 2020 09:47:07 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9823220836 for ; Mon, 24 Feb 2020 09:47:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9823220836 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 2BE606B0005; Mon, 24 Feb 2020 04:47:05 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 26F0F6B0006; Mon, 24 Feb 2020 04:47:05 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1ACEB6B0007; Mon, 24 Feb 2020 04:47:05 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 062806B0005 for ; Mon, 24 Feb 2020 04:47:05 -0500 (EST) Received: from smtpin13.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id B216A81D8 for ; Mon, 24 Feb 2020 09:47:04 +0000 (UTC) X-FDA: 76524541968.13.boot39_5ad306051b21b X-HE-Tag: boot39_5ad306051b21b X-Filterd-Recvd-Size: 5544 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf29.hostedemail.com (Postfix) with ESMTP for ; Mon, 24 Feb 2020 09:47:03 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 346BAAE64; Mon, 24 Feb 2020 09:47:02 +0000 (UTC) From: Vlastimil Babka To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Vlastimil Babka , Gerald Schaefer , Qian Cai , Joonsoo Kim , stable@vger.kernel.org Subject: [PATCH] mm, hotplug: fix page online with DEBUG_PAGEALLOC compiled but not enabled Date: Mon, 24 Feb 2020 10:46:51 +0100 Message-Id: <20200224094651.18257-1-vbabka@suse.cz> X-Mailer: git-send-email 2.25.0 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Commit cd02cf1aceea ("mm/hotplug: fix an imbalance with DEBUG_PAGEALLOC")= fixed memory hotplug with debug_pagealloc enabled, where onlining a page goes t= hrough page freeing, which removes the direct mapping. Some arches don't like wh= en the page is not mapped in the first place, so generic_online_page() maps it f= irst. This is somewhat wasteful, but better than special casing page freeing fa= st paths. The commit however missed that DEBUG_PAGEALLOC configured doesn't mean it= 's actually enabled. One has to test debug_pagealloc_enabled() since 031bc57= 43f15 ("mm/debug-pagealloc: make debug-pagealloc boottime configurable"), or al= ternatively debug_pagealloc_enabled_static() since 8e57f8acbbd1 ("mm, debug_pagealloc= : don't rely on static keys too early"), but this is not done. As a result, a s390 kernel with DEBUG_PAGEALLOC configured but not enable= d will crash: Unable to handle kernel pointer dereference in virtual kernel address spa= ce Failing address: 0000000000000000 TEID: 0000000000000483 Fault in home space mode while using kernel ASCE. AS:0000001ece13400b R2:000003fff7fd000b R3:000003fff7fcc007 S:000003fff7f= d7000 P:000000000000013d Oops: 0004 ilc:2 [#1] SMP CPU: 1 PID: 26015 Comm: chmem Kdump: loaded Tainted: GX 5.3.18-5-default = #1 SLE15-SP2 (unreleased) Krnl PSW : 0704e00180000000 0000001ecd281b9e (__kernel_map_pages+0x166/0x= 188) R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:2 PM:0 RI:0 EA:3 Krnl GPRS: 0000000000000000 0000000000000800 0000400b00000000 00000000000= 00100 0000000000000001 0000000000000000 0000000000000002 0000000000000100 0000001ece139230 0000001ecdd98d40 0000400b00000100 0000000000000000 000003ffa17e4000 001fffe0114f7d08 0000001ecd4d93ea 001fffe0114f7b20 Krnl Code: 0000001ecd281b8e: ec17ffff00d8 ahik %r1,%r7,-1 0000001ecd281b94: ec111dbc0355 risbg %r1,%r1,29,188,3 >0000001ecd281b9e: 94fb5006 ni 6(%r5),251 0000001ecd281ba2: 41505008 la %r5,8(%r5) 0000001ecd281ba6: ec51fffc6064 cgrj %r5,%r1,6,1ecd281b9e 0000001ecd281bac: 1a07 ar %r0,%r7 0000001ecd281bae: ec03ff584076 crj %r0,%r3,4,1ecd281a5e Call Trace: [<0000001ecd281b9e>] __kernel_map_pages+0x166/0x188 [<0000001ecd4d9516>] online_pages_range+0xf6/0x128 [<0000001ecd2a8186>] walk_system_ram_range+0x7e/0xd8 [<0000001ecda28aae>] online_pages+0x2fe/0x3f0 [<0000001ecd7d02a6>] memory_subsys_online+0x8e/0xc0 [<0000001ecd7add42>] device_online+0x5a/0xc8 [<0000001ecd7d0430>] state_store+0x88/0x118 [<0000001ecd5b9f62>] kernfs_fop_write+0xc2/0x200 [<0000001ecd5064b6>] vfs_write+0x176/0x1e0 [<0000001ecd50676a>] ksys_write+0xa2/0x100 [<0000001ecda315d4>] system_call+0xd8/0x2c8 Fix this by checking debug_pagealloc_enabled_static() before calling kernel_map_pages(). Backports for kernel before 5.5 should use debug_pagealloc_enabled() instead. Also add comments. Fixes: cd02cf1aceea ("mm/hotplug: fix an imbalance with DEBUG_PAGEALLOC") Signed-off-by: Vlastimil Babka Reported-by: Gerald Schaefer Cc: Qian Cai Cc: Joonsoo Kim Cc: --- include/linux/mm.h | 4 ++++ mm/memory_hotplug.c | 8 +++++++- 2 files changed, 11 insertions(+), 1 deletion(-) diff --git include/linux/mm.h include/linux/mm.h index 52269e56c514..c54fb96cb1e6 100644 --- include/linux/mm.h +++ include/linux/mm.h @@ -2715,6 +2715,10 @@ static inline bool debug_pagealloc_enabled_static(= void) #if defined(CONFIG_DEBUG_PAGEALLOC) || defined(CONFIG_ARCH_HAS_SET_DIREC= T_MAP) extern void __kernel_map_pages(struct page *page, int numpages, int enab= le); =20 +/* + * When called in DEBUG_PAGEALLOC context, the call should most likely b= e + * guarded by debug_pagealloc_enabled() or debug_pagealloc_enabled_stati= c() + */ static inline void kernel_map_pages(struct page *page, int numpages, int enable) { diff --git mm/memory_hotplug.c mm/memory_hotplug.c index 0a54ffac8c68..19389cdc16a5 100644 --- mm/memory_hotplug.c +++ mm/memory_hotplug.c @@ -574,7 +574,13 @@ EXPORT_SYMBOL_GPL(restore_online_page_callback); =20 void generic_online_page(struct page *page, unsigned int order) { - kernel_map_pages(page, 1 << order, 1); + /* + * Freeing the page with debug_pagealloc enabled will try to unmap it, + * so we should map it first. This is better than introducing a special + * case in page freeing fast path. + */ + if (debug_pagealloc_enabled_static()) + kernel_map_pages(page, 1 << order, 1); __free_pages_core(page, order); totalram_pages_add(1UL << order); #ifdef CONFIG_HIGHMEM --=20 2.25.0