[PATCH v3 1/2] mm: soft-offline: return -EBUSY if set_hwpoison_free_buddy_page() fails

[Naoya Horiguchi]

The pass/fail of soft offline should be judged by checking whether the
raw error page was finally contained or not (i.e. the result of
set_hwpoison_free_buddy_page()), but current code do not work like that.
So this patch is suggesting to fix it.

Without this fix, there are cases where madvise(MADV_SOFT_OFFLINE) may
not offline the original page and will not return an error.  It might
lead us to misjudge the test result when set_hwpoison_free_buddy_page()
actually fails.

Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Fixes: 6bc9b56433b76 ("mm: fix race on soft-offlining")
Cc: <stable@xxxxxxxxxxxxxxx> # v4.19+
---
ChangeLog v2->v3:
- update patch description to clarify user visible change
---
 mm/memory-failure.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git v5.2-rc4/mm/memory-failure.c v5.2-rc4_patched/mm/memory-failure.c
index 8da0334..8ee7b16 100644
--- v5.2-rc4/mm/memory-failure.c
+++ v5.2-rc4_patched/mm/memory-failure.c
@@ -1730,6 +1730,8 @@ static int soft_offline_huge_page(struct page *page, int flags)
 		if (!ret) {
 			if (set_hwpoison_free_buddy_page(page))
 				num_poisoned_pages_inc();
+			else
+				ret = -EBUSY;
 		}
 	}
 	return ret;
-- 
2.7.0