linux-kernel - [PATCH v2 2/2] mm: soft-offline: exit with failure for non anonymous thp

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Date:	Tue, 12 Jan 2016 12:10:45 +0900
From:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Naoya Horiguchi <nao.horiguchi@...il.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>
Subject: [PATCH v2 2/2] mm: soft-offline: exit with failure for non anonymous thp

Currently memory_failure() doesn't handle non anonymous thp case, because we
can hardly expect the error handling to be successful, and it can just hit
some corner case which results in BUG_ON or something severe like that.
This is also the case for soft offline code, so let's make it in the same way.

Orignal code has a MF_COUNT_INCREASED check before put_hwpoison_page(), but
it's unnecessary because get_any_page() is already called when running on
this code, which takes a refcount of the target page regardress of the flag.
So this patch also removes it.

Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
---
ChangeLog v1->v2:
- rebased to next-20160111
---
 mm/memory-failure.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git next-20160111/mm/memory-failure.c next-20160111_patched/mm/memory-failure.c
index 2015c9a..6a2f290 100644
--- next-20160111/mm/memory-failure.c
+++ next-20160111_patched/mm/memory-failure.c
@@ -1691,16 +1691,16 @@ static int soft_offline_in_use_page(struct page *page, int flags)
 
 	if (!PageHuge(page) && PageTransHuge(hpage)) {
 		lock_page(hpage);
-		ret = split_huge_page(hpage);
-		unlock_page(hpage);
-		if (unlikely(ret || PageTransCompound(page) ||
-			     !PageAnon(page))) {
-			pr_info("soft offline: %#lx: failed to split THP\n",
-				page_to_pfn(page));
-			if (flags & MF_COUNT_INCREASED)
-				put_hwpoison_page(hpage);
+		if (!PageAnon(hpage) || unlikely(split_huge_page(hpage))) {
+			unlock_page(hpage);
+			if (!PageAnon(hpage))
+				pr_info("soft offline: %#lx: non anonymous thp\n", pfn);
+			else
+				pr_info("soft offline: %#lx: thp split failed\n", pfn);
+			put_hwpoison_page(hpage);
 			return -EBUSY;
 		}
+		unlock_page(hpage);
 		get_hwpoison_page(page);
 		put_hwpoison_page(hpage);
 	}
-- 
2.7.0