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From: nao.horiguchi@gmail.com
To: linux-mm@kvack.org
Cc: mhocko@kernel.org, akpm@linux-foundation.org,
	mike.kravetz@oracle.com, osalvador@suse.de, tony.luck@intel.com,
	david@redhat.com, aneesh.kumar@linux.vnet.ibm.com,
	zeil@yandex-team.ru, naoya.horiguchi@nec.com,
	linux-kernel@vger.kernel.org
Subject: [PATCH v3 03/15] mm,madvise: call soft_offline_page() without MF_COUNT_INCREASED
Date: Wed, 24 Jun 2020 15:01:25 +0000
Message-ID: <20200624150137.7052-4-nao.horiguchi@gmail.com> (raw)
In-Reply-To: <20200624150137.7052-1-nao.horiguchi@gmail.com>

From: Naoya Horiguchi <naoya.horiguchi@nec.com>

The call to get_user_pages_fast is only to get the pointer to a struct
page of a given address, pinning it is memory-poisoning handler's job,
so drop the refcount grabbed by get_user_pages_fast().

Note that the target page is still pinned after this put_page() because
the current process should have refcount from mapping.

Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Signed-off-by: Oscar Salvador <osalvador@suse.de>
---
 mm/madvise.c | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git v5.8-rc1-mmots-2020-06-20-21-44/mm/madvise.c v5.8-rc1-mmots-2020-06-20-21-44_patched/mm/madvise.c
index dd1d43cf026d..275b08edd428 100644
--- v5.8-rc1-mmots-2020-06-20-21-44/mm/madvise.c
+++ v5.8-rc1-mmots-2020-06-20-21-44_patched/mm/madvise.c
@@ -893,16 +893,24 @@ static int madvise_inject_error(int behavior,
 		 */
 		size = page_size(compound_head(page));
 
-		if (PageHWPoison(page)) {
-			put_page(page);
+		/*
+		 * 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);
+
+		if (PageHWPoison(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(pfn, MF_COUNT_INCREASED);
+			ret = soft_offline_page(pfn, 0);
 			if (ret)
 				return ret;
 			continue;
@@ -910,14 +918,6 @@ 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;
-- 
2.17.1



  parent reply index

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-24 15:01 [PATCH v3 00/15] HWPOISON: soft offline rework nao.horiguchi
2020-06-24 15:01 ` [PATCH v3 01/15] mm,hwpoison: cleanup unused PageHuge() check nao.horiguchi
2020-06-30 23:28   ` Mike Kravetz
2020-06-24 15:01 ` [PATCH v3 02/15] mm, hwpoison: remove recalculating hpage nao.horiguchi
2020-06-30 23:45   ` Mike Kravetz
2020-06-24 15:01 ` nao.horiguchi [this message]
2020-06-24 15:01 ` [PATCH v3 04/15] mm,madvise: Refactor madvise_inject_error nao.horiguchi
2020-06-24 15:01 ` [PATCH v3 05/15] mm,hwpoison-inject: don't pin for hwpoison_filter nao.horiguchi
2020-06-24 15:01 ` [PATCH v3 06/15] mm,hwpoison: Un-export get_hwpoison_page and make it static nao.horiguchi
2020-06-24 15:01 ` [PATCH v3 07/15] mm,hwpoison: Kill put_hwpoison_page nao.horiguchi
2020-06-24 15:01 ` [PATCH v3 08/15] mm,hwpoison: remove MF_COUNT_INCREASED nao.horiguchi
2020-06-24 15:01 ` [PATCH v3 09/15] mm,hwpoison: remove flag argument from soft offline functions nao.horiguchi
2020-06-24 15:01 ` [PATCH v3 10/15] mm,hwpoison: Unify THP handling for hard and soft offline nao.horiguchi
2020-06-24 15:01 ` [PATCH v3 11/15] mm,hwpoison: Rework soft offline for free pages nao.horiguchi
2020-06-24 15:01 ` [PATCH v3 12/15] mm,hwpoison: Rework soft offline for in-use pages nao.horiguchi
2020-06-24 15:01 ` [PATCH v3 13/15] mm,hwpoison: Refactor soft_offline_huge_page and __soft_offline_page nao.horiguchi
2020-06-26 16:53   ` Naresh Kamboju
2020-06-28  6:54     ` Naoya Horiguchi
2020-06-29  7:22       ` Stephen Rothwell
2020-06-29  7:33         ` HORIGUCHI NAOYA(堀口 直也)
2020-06-24 15:01 ` [PATCH v3 14/15] mm,hwpoison: Return 0 if the page is already poisoned in soft-offline nao.horiguchi
2020-06-24 15:01 ` [PATCH v3 15/15] mm,hwpoison: introduce MF_MSG_UNSPLIT_THP nao.horiguchi
2020-06-24 19:17 ` [PATCH v3 00/15] HWPOISON: soft offline rework Andrew Morton
2020-06-24 22:36   ` HORIGUCHI NAOYA(堀口 直也)
2020-06-24 22:49     ` Andrew Morton
2020-06-24 23:01       ` HORIGUCHI NAOYA(堀口 直也)
2020-06-26 13:35 ` Qian Cai
2020-06-29 10:29 ` Oscar Salvador
2020-06-30  6:50   ` HORIGUCHI NAOYA(堀口 直也)
2020-06-30  5:08 ` Qian Cai
2020-06-30  6:35   ` Oscar Salvador
2020-07-01  8:22     ` Oscar Salvador
2020-07-01  9:07       ` HORIGUCHI NAOYA(堀口 直也)
2020-07-14 10:08   ` Oscar Salvador

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