From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx201.postini.com [74.125.245.201]) by kanga.kvack.org (Postfix) with SMTP id 238036B0044 for ; Tue, 11 Dec 2012 07:42:50 -0500 (EST) Received: from /spool/local by e28smtp04.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 11 Dec 2012 18:12:27 +0530 Received: from d28relay02.in.ibm.com (d28relay02.in.ibm.com [9.184.220.59]) by d28dlp01.in.ibm.com (Postfix) with ESMTP id 51CBDE004C for ; Tue, 11 Dec 2012 18:12:24 +0530 (IST) Received: from d28av03.in.ibm.com (d28av03.in.ibm.com [9.184.220.65]) by d28relay02.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id qBBCgfEb31916080 for ; Tue, 11 Dec 2012 18:12:41 +0530 Received: from d28av03.in.ibm.com (loopback [127.0.0.1]) by d28av03.in.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id qBBCgemO031209 for ; Tue, 11 Dec 2012 23:42:41 +1100 Date: Tue, 11 Dec 2012 20:42:39 +0800 From: Wanpeng Li Subject: Re: [PATCH V3 1/2] MCE: fix an error of mce_bad_pages statistics Message-ID: <20121211124238.GA9959@hacker.(null)> Reply-To: Wanpeng Li References: <50C72493.3080009@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <50C72493.3080009@huawei.com> Sender: owner-linux-mm@kvack.org List-ID: To: Xishi Qiu Cc: WuJianguo , Liujiang , Simon Jeons , Andrew Morton , Borislav Petkov , Andi Kleen , Fengguang Wu , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Tue, Dec 11, 2012 at 08:18:27PM +0800, Xishi Qiu wrote: >1) move poisoned page check at the beginning of the function. >2) add page_lock to avoid unpoison clear the flag. > >Signed-off-by: Xishi Qiu >i>>?Signed-off-by: Jiang Liu >--- > mm/memory-failure.c | 43 ++++++++++++++++++++++--------------------- > 1 files changed, 22 insertions(+), 21 deletions(-) > >diff --git a/mm/memory-failure.c b/mm/memory-failure.c >index 8b20278..9b74983 100644 >--- a/mm/memory-failure.c >+++ b/mm/memory-failure.c >@@ -1419,18 +1419,17 @@ static int soft_offline_huge_page(struct page *page, int flags) > unsigned long pfn = page_to_pfn(page); > struct page *hpage = compound_head(page); > >+ if (PageHWPoison(hpage)) { >+ pr_info("soft offline: %#lx hugepage already poisoned\n", pfn); >+ return -EBUSY; >+ } >+ > ret = get_any_page(page, pfn, flags); > if (ret < 0) > return ret; > if (ret == 0) > goto done; > >- if (PageHWPoison(hpage)) { >- put_page(hpage); >- pr_info("soft offline: %#lx hugepage already poisoned\n", pfn); >- return -EBUSY; >- } >- > /* Keep page count to indicate a given hugepage is isolated. */ > ret = migrate_huge_page(hpage, new_page, MPOL_MF_MOVE_ALL, false, > MIGRATE_SYNC); >@@ -1441,12 +1440,14 @@ static int soft_offline_huge_page(struct page *page, int flags) > return ret; > } > done: >- if (!PageHWPoison(hpage)) >- atomic_long_add(1 << compound_trans_order(hpage), >- &mce_bad_pages); >+ /* keep elevated page count for bad page */ >+ lock_page(hpage); >+ atomic_long_add(1 << compound_trans_order(hpage), &mce_bad_pages); > set_page_hwpoison_huge_page(hpage); >+ unlock_page(hpage); >+ > dequeue_hwpoisoned_huge_page(hpage); >- /* keep elevated page count for bad page */ >+ > return ret; > } > >@@ -1488,6 +1489,11 @@ int soft_offline_page(struct page *page, int flags) > } > } > >+ if (PageHWPoison(page)) { >+ pr_info("soft offline: %#lx page already poisoned\n", pfn); >+ return -EBUSY; >+ } >+ > ret = get_any_page(page, pfn, flags); > if (ret < 0) > return ret; >@@ -1519,19 +1525,11 @@ int soft_offline_page(struct page *page, int flags) > return -EIO; > } > >- lock_page(page); >- wait_on_page_writeback(page); >- > /* > * Synchronized using the page lock with memory_failure() > */ >- if (PageHWPoison(page)) { >- unlock_page(page); >- put_page(page); >- pr_info("soft offline: %#lx page already poisoned\n", pfn); >- return -EBUSY; >- } >- >+ lock_page(page); >+ wait_on_page_writeback(page); > /* > * Try to invalidate first. This should work for > * non dirty unmapped page cache pages. >@@ -1582,8 +1580,11 @@ int soft_offline_page(struct page *page, int flags) > return ret; > > done: >+ /* keep elevated page count for bad page */ >+ lock_page(page); > atomic_long_add(1, &mce_bad_pages); > SetPageHWPoison(page); >- /* keep elevated page count for bad page */ >+ unlock_page(page); >+ Hi Xishi, Why add lock_page here, the comment in function unpoison_memory tell us we don't need it. /* * This test is racy because PG_hwpoison is set outside of page lock. * That's acceptable because that won't trigger kernel panic. Instead, * the PG_hwpoison page will be caught and isolated on the entrance to * the free buddy page pool. */ Futhermore, Andrew didn't like a variable called "mce_bad_pages". - Why do we have a variable called "mce_bad_pages"? MCE is an x86 concept, and this code is in mm/. Lights are flashing, bells are ringing and a loudspeaker is blaring "layering violation" at us! Regards, Wanpeng Li > return ret; > } >-- >1.7.1 > > >-- >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 -- 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