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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 v5 14/16] mm,hwpoison: Return 0 if the page is already poisoned in soft-offline
Date:   Fri, 31 Jul 2020 12:21:10 +0000
Message-Id: <20200731122112.11263-15-nao.horiguchi@gmail.com>
In-Reply-To: <20200731122112.11263-1-nao.horiguchi@gmail.com>
References: <20200731122112.11263-1-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        | 3 ---
 mm/memory-failure.c | 4 ++--
 2 files changed, 2 insertions(+), 5 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 3eee78abdbec..843f6fad3b89 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
@@ -919,9 +919,6 @@ static int madvise_inject_error(int behavior,
 		 */
 		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);
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 904dec64da6b..bd63f1f2e44e 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
@@ -1794,7 +1794,7 @@ 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))
@@ -1895,7 +1895,7 @@ int soft_offline_page(unsigned long pfn)
 
 	if (PageHWPoison(page)) {
 		pr_info("soft offline: %#lx page already poisoned\n", pfn);
-		return -EBUSY;
+		return 0;
 	}
 
 	get_online_mems();
-- 
2.17.1