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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,
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        zeil@yandex-team.ru, cai@lca.pw, naoya.horiguchi@nec.com,
        linux-kernel@vger.kernel.org
Subject: [PATCH v6 10/12] mm,hwpoison: Return 0 if the page is already poisoned in soft-offline
Date:   Thu,  6 Aug 2020 18:49:21 +0000
Message-Id: <20200806184923.7007-11-nao.horiguchi@gmail.com>
In-Reply-To: <20200806184923.7007-1-nao.horiguchi@gmail.com>
References: <20200806184923.7007-1-nao.horiguchi@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
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From: Oscar Salvador <osalvador@suse.de>

Currently, there is an inconsistency when calling soft-offline from
different paths on a page that is already poisoned.

1) madvise:

        madvise_inject_error skips any poisoned page and continues
        the loop.
        If that was the only page to madvise, it returns 0.

2) /sys/devices/system/memory/:

        When calling soft_offline_page_store()->soft_offline_page(),
        we return -EBUSY in case the page is already poisoned.
        This is inconsistent with a) the above example and b)
        memory_failure, where we return 0 if the page was poisoned.

Fix this by dropping the PageHWPoison() check in madvise_inject_error,
and let soft_offline_page return 0 if it finds the page already poisoned.

Please, note that this represents a user-api change, since now the
return error when calling soft_offline_page_store()->soft_offline_page()
will be different.

Signed-off-by: Oscar Salvador <osalvador@suse.com>
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
---
 mm/madvise.c        | 5 -----
 mm/memory-failure.c | 4 ++--
 2 files changed, 2 insertions(+), 7 deletions(-)

diff --git v5.8-rc7-mmotm-2020-07-27-18-18/mm/madvise.c v5.8-rc7-mmotm-2020-07-27-18-18_patched/mm/madvise.c
index a16dba21cdf6..5fa5f66468b3 100644
--- v5.8-rc7-mmotm-2020-07-27-18-18/mm/madvise.c
+++ v5.8-rc7-mmotm-2020-07-27-18-18_patched/mm/madvise.c
@@ -910,11 +910,6 @@ static int madvise_inject_error(int behavior,
 		 */
 		size = page_size(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);
diff --git v5.8-rc7-mmotm-2020-07-27-18-18/mm/memory-failure.c v5.8-rc7-mmotm-2020-07-27-18-18_patched/mm/memory-failure.c
index 3a2cd094b77f..61e20b7dd81c 100644
--- v5.8-rc7-mmotm-2020-07-27-18-18/mm/memory-failure.c
+++ v5.8-rc7-mmotm-2020-07-27-18-18_patched/mm/memory-failure.c
@@ -1800,7 +1800,7 @@ static int __soft_offline_page(struct page *page)
 		unlock_page(page);
 		put_page(page);
 		pr_info("soft offline: %#lx page already poisoned\n", pfn);
-		return -EBUSY;
+		return 0;
 	}
 
 	if (!PageHuge(page))
@@ -1904,7 +1904,7 @@ int soft_offline_page(unsigned long pfn, int flags)
 		pr_info("soft offline: %#lx page already poisoned\n", pfn);
 		if (flags & MF_COUNT_INCREASED)
 			put_page(page);
-		return -EBUSY;
+		return 0;
 	}
 
 	get_online_mems();
-- 
2.17.1