From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx206.postini.com [74.125.245.206]) by kanga.kvack.org (Postfix) with SMTP id 839EA6B003B for ; Sun, 25 Aug 2013 21:19:17 -0400 (EDT) Received: from /spool/local by e28smtp05.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 26 Aug 2013 06:42:40 +0530 Received: from d28relay02.in.ibm.com (d28relay02.in.ibm.com [9.184.220.59]) by d28dlp01.in.ibm.com (Postfix) with ESMTP id 3E00EE0053 for ; Mon, 26 Aug 2013 06:49:45 +0530 (IST) Received: from d28av05.in.ibm.com (d28av05.in.ibm.com [9.184.220.67]) by d28relay02.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r7Q1KoeR39059546 for ; Mon, 26 Aug 2013 06:50:50 +0530 Received: from d28av05.in.ibm.com (localhost [127.0.0.1]) by d28av05.in.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id r7Q1JAY2011498 for ; Mon, 26 Aug 2013 06:49:10 +0530 From: 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> 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> Sender: owner-linux-mm@kvack.org List-ID: 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 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org