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From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
To: linux-mm@kvack.org, linux-kernel@vger.kernel.org
Cc: Michal Hocko <mhocko@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	xishi.qiuxishi@alibaba-inc.com,
	Laurent Dufour <ldufour@linux.vnet.ibm.com>
Subject: [RFC][PATCH v1 04/11] mm: madvise: call soft_offline_page() without MF_COUNT_INCREASED
Date: Fri,  9 Nov 2018 15:47:08 +0900	[thread overview]
Message-ID: <1541746035-13408-5-git-send-email-n-horiguchi@ah.jp.nec.com> (raw)
In-Reply-To: <1541746035-13408-1-git-send-email-n-horiguchi@ah.jp.nec.com>

Currently madvise_inject_error() pins the target page when calling
memory error handler, but it's not good because the refcount is just
an artifact of error injector and mock nothing about hw error itself.
IOW, pinning the error page is part of error handler's task, so
let's stop doing it.

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
---
 mm/madvise.c | 25 +++++++++++--------------
 1 file changed, 11 insertions(+), 14 deletions(-)

diff --git v4.19-mmotm-2018-10-30-16-08/mm/madvise.c v4.19-mmotm-2018-10-30-16-08_patched/mm/madvise.c
index 6cb1ca9..9fa0225 100644
--- v4.19-mmotm-2018-10-30-16-08/mm/madvise.c
+++ v4.19-mmotm-2018-10-30-16-08_patched/mm/madvise.c
@@ -637,6 +637,16 @@ static int madvise_inject_error(int behavior,
 		ret = get_user_pages_fast(start, 1, 0, &page);
 		if (ret != 1)
 			return ret;
+		/*
+		 * The get_user_pages_fast() is just to get the pfn of the
+		 * given address, and the refcount has nothing to do with
+		 * what we try to test, so it should be released immediately.
+		 * This is racy but it's intended because the real hardware
+		 * errors could happen at any moment and memory error handlers
+		 * must properly handle the race.
+		 */
+		put_page(page);
+
 		pfn = page_to_pfn(page);
 
 		/*
@@ -646,16 +656,11 @@ static int madvise_inject_error(int behavior,
 		 */
 		order = compound_order(compound_head(page));
 
-		if (PageHWPoison(page)) {
-			put_page(page);
-			continue;
-		}
-
 		if (behavior == MADV_SOFT_OFFLINE) {
 			pr_info("Soft offlining pfn %#lx at process virtual address %#lx\n",
 					pfn, start);
 
-			ret = soft_offline_page(page, MF_COUNT_INCREASED);
+			ret = soft_offline_page(page, 0);
 			if (ret)
 				return ret;
 			continue;
@@ -663,14 +668,6 @@ static int madvise_inject_error(int behavior,
 
 		pr_info("Injecting memory failure for pfn %#lx at process virtual address %#lx\n",
 				pfn, start);
-
-		/*
-		 * Drop the page reference taken by get_user_pages_fast(). In
-		 * the absence of MF_COUNT_INCREASED the memory_failure()
-		 * routine is responsible for pinning the page to prevent it
-		 * from being released back to the page allocator.
-		 */
-		put_page(page);
 		ret = memory_failure(pfn, 0);
 		if (ret)
 			return ret;
-- 
2.7.0


  parent reply	other threads:[~2018-11-09  6:47 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-09  6:47 [PATCH RFC v1 00/11] hwpoison improvement part 1 Naoya Horiguchi
2018-11-09  6:47 ` [RFC][PATCH v1 01/11] mm: hwpoison: cleanup unused PageHuge() check Naoya Horiguchi
2018-11-09  9:52   ` Anshuman Khandual
2018-11-09  6:47 ` [RFC][PATCH v1 02/11] mm: soft-offline: add missing error check of set_hwpoison_free_buddy_page() Naoya Horiguchi
2018-11-09 10:20   ` Anshuman Khandual
2018-11-13  0:16     ` Naoya Horiguchi
2018-11-14  8:53       ` Anshuman Khandual
2018-11-09  6:47 ` [RFC][PATCH v1 03/11] mm: move definition of num_poisoned_pages_inc/dec to include/linux/mm.h Naoya Horiguchi
2018-11-09 10:28   ` Anshuman Khandual
2018-11-13  0:17     ` Naoya Horiguchi
2018-11-09  6:47 ` Naoya Horiguchi [this message]
2018-11-09 10:46   ` [RFC][PATCH v1 04/11] mm: madvise: call soft_offline_page() without MF_COUNT_INCREASED Anshuman Khandual
2018-11-13  0:18     ` Naoya Horiguchi
2018-11-09  6:47 ` [RFC][PATCH v1 05/11] mm: hwpoison-inject: don't pin for hwpoison_filter() Naoya Horiguchi
2018-11-09  6:47 ` [RFC][PATCH v1 06/11] mm: hwpoison: remove MF_COUNT_INCREASED Naoya Horiguchi
2018-11-09  6:47 ` [RFC][PATCH v1 07/11] mm: remove flag argument from soft offline functions Naoya Horiguchi
2018-11-09  6:47 ` [RFC][PATCH v1 08/11] mm: soft-offline: isolate error pages from buddy freelist Naoya Horiguchi
2018-11-09  6:47 ` [RFC][PATCH v1 09/11] mm: hwpoison: apply buddy page handling code to hard-offline Naoya Horiguchi
2018-11-09  6:47 ` [RFC][PATCH v1 10/11] mm: clear PageHWPoison in memory hotremove Naoya Horiguchi
2018-11-13  1:32   ` Naoya Horiguchi
2018-11-09  6:47 ` [RFC][PATCH v1 11/11] mm: hwpoison: introduce clear_hwpoison_free_buddy_page() Naoya Horiguchi
2018-11-09 11:33   ` Anshuman Khandual
2018-11-13  0:19     ` Naoya Horiguchi
2018-11-14  8:23       ` Anshuman Khandual

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