Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753450AbbHCMux (ORCPT ); Mon, 3 Aug 2015 08:50:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34977 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752203AbbHCMuv (ORCPT ); Mon, 3 Aug 2015 08:50:51 -0400 From: Baoquan He To: akpm@linux-foundation.org, ebiederm@xmission.com, vgoyal@redhat.com, dyoung@redhat.com, mhuang@redhat.com, lisa.mitchell@hp.com, tatsu@ab.jp.nec.com, seiji.aguchi.tr@hitachi.com Cc: linux-kernel@vger.kernel.org, kexec@lists.infradead.org, Baoquan He Subject: [Patch v2] align crash_notes allocation to make it be inside one physical page Date: Mon, 3 Aug 2015 20:50:43 +0800 Message-Id: <1438606243-13064-1-git-send-email-bhe@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2466 Lines: 64 People reported that crash_notes in /proc/vmcore were corrupted and this cause crash kdump failure. With code debugging and log we got the root cause. This is because percpu variable crash_notes are allocated in 2 vmalloc pages. Currently percpu is based on vmalloc by default. Vmalloc can't guarantee 2 continuous vmalloc pages are also on 2 continuous physical pages. So when 1st kernel exports the starting address and size of crash_notes through sysfs like below: /sys/devices/system/cpu/cpux/crash_notes /sys/devices/system/cpu/cpux/crash_notes_size kdump kernel use them to get the content of crash_notes. However the 2nd part may not be in the next neighbouring physical page as we expected if crash_notes are allocated accross 2 vmalloc pages. That's why nhdr_ptr->n_namesz or nhdr_ptr->n_descsz could be very huge in update_note_header_size_elf64() and cause note header merging failure or some warnings. In this patch change to call __alloc_percpu() to passed in the align value by rounding crash_notes_size up to the nearest power of two. This make sure the crash_notes is allocated inside one physical page since sizeof(note_buf_t) in all ARCHS is smaller than PAGE_SIZE. Meanwhile add a WARN_ON in case it grows to be bigger than PAGE_SIZE in the future. v1->v2: Minfei mentioned percpu can't take align value bigger then PAGE_SIZE. So limit align to be PAGE_SIZE at most. Signed-off-by: Baoquan He --- kernel/kexec.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/kernel/kexec.c b/kernel/kexec.c index a785c10..9f4b070 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -1620,7 +1620,16 @@ void crash_save_cpu(struct pt_regs *regs, int cpu) static int __init crash_notes_memory_init(void) { /* Allocate memory for saving cpu registers. */ - crash_notes = alloc_percpu(note_buf_t); + size_t size, align; + int order; + + size = sizeof(note_buf_t); + order = get_count_order(size); + align = min_t(size_t, (1< PAGE_SIZE); + + crash_notes = __alloc_percpu(size, align); if (!crash_notes) { pr_warn("Kexec: Memory allocation for saving cpu register states failed\n"); return -ENOMEM; -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/