Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755812Ab3HZBUN (ORCPT ); Sun, 25 Aug 2013 21:20:13 -0400 Received: from e28smtp06.in.ibm.com ([122.248.162.6]:32983 "EHLO e28smtp06.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754509Ab3HZBTQ (ORCPT ); Sun, 25 Aug 2013 21:19:16 -0400 From: Wanpeng Li To: Andrew Morton Cc: Andi Kleen , Fengguang Wu , Naoya Horiguchi , Tony Luck , gong.chen@linux.intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Wanpeng Li Subject: [PATCH v3 8/8] mm/hwpoison: fix memory failure still hold reference count after unpoison empty zero page Date: Mon, 26 Aug 2013 09:18:51 +0800 Message-Id: <1377479931-7430-8-git-send-email-liwanp@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.5.4 In-Reply-To: <1377479931-7430-1-git-send-email-liwanp@linux.vnet.ibm.com> References: <1377479931-7430-1-git-send-email-liwanp@linux.vnet.ibm.com> X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13082601-9574-0000-0000-000009546F8A Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3392 Lines: 97 madvise hwpoison inject will poison the read-only empty zero page if there is no write access before poison. Empty zero page reference count will be increased for hwpoison, subsequent poison zero page will return directly since page has already been set PG_hwpoison, however, page reference count is still increased by get_user_pages_fast. The unpoison process will unpoison the empty zero page and decrease the reference count successfully for the fist time, however, subsequent unpoison empty zero page will return directly since page has already been unpoisoned and without decrease the page reference count of empty zero page. This patch fix it by decrease page reference count for empty zero page which has already been unpoisoned and page count > 1. Testcase: #define _GNU_SOURCE #include #include #include #include #include #include #include #define PAGES_TO_TEST 3 #define PAGE_SIZE 4096 int main(void) { char *mem; int i; mem = mmap(NULL, PAGES_TO_TEST * PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, 0, 0); if (madvise(mem, PAGES_TO_TEST * PAGE_SIZE, MADV_HWPOISON) == -1) return -1; munmap(mem, PAGES_TO_TEST * PAGE_SIZE); return 0; } Add printk to dump page reference count: [ 93.075959] Injecting memory failure for page 0x19d0 at 0xb77d8000 [ 93.076207] MCE 0x19d0: non LRU page recovery: Ignored [ 93.076209] pfn 0x19d0, page count = 1 after memory failure [ 93.076220] Injecting memory failure for page 0x19d0 at 0xb77d9000 [ 93.076221] MCE 0x19d0: already hardware poisoned [ 93.076222] pfn 0x19d0, page count = 2 after memory failure [ 93.076224] Injecting memory failure for page 0x19d0 at 0xb77da000 [ 93.076224] MCE 0x19d0: already hardware poisoned [ 93.076225] pfn 0x19d0, page count = 3 after memory failure Before patch: [ 139.197474] MCE: Software-unpoisoned page 0x19d0 [ 139.197479] pfn 0x19d0, page count = 2 after unpoison memory [ 150.478130] MCE: Page was already unpoisoned 0x19d0 [ 150.478135] pfn 0x19d0, page count = 2 after unpoison memory [ 151.548288] MCE: Page was already unpoisoned 0x19d0 [ 151.548292] pfn 0x19d0, page count = 2 after unpoison memory After patch: [ 116.022122] MCE: Software-unpoisoned page 0x19d0 [ 116.022127] pfn 0x19d0, page count = 2 after unpoison memory [ 117.256163] MCE: Page was already unpoisoned 0x19d0 [ 117.256167] pfn 0x19d0, page count = 1 after unpoison memory [ 117.917772] MCE: Page was already unpoisoned 0x19d0 [ 117.917777] pfn 0x19d0, page count = 1 after unpoison memory Signed-off-by: Wanpeng Li --- mm/memory-failure.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/memory-failure.c b/mm/memory-failure.c index ca714ac..fb687fd 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -1335,6 +1335,8 @@ int unpoison_memory(unsigned long pfn) page = compound_head(p); if (!PageHWPoison(p)) { + if (pfn == my_zero_pfn(0) && page_count(p) > 1) + put_page(p); pr_info("MCE: Page was already unpoisoned %#lx\n", pfn); return 0; } -- 1.8.1.2 -- 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/