[PATCH v5 14/16] mm,hwpoison: Return 0 if the page is already poisoned in soft-offline

[nao . horiguchi]

From: Oscar Salvador <osalva...@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 <osalva...@suse.com>
Signed-off-by: Naoya Horiguchi <naoya.horigu...@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