3.5.7.2 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Naoya Horiguchi <[email protected]>

commit 783657a7dc20e5c0efbc9a09a9dd38e238a723da upstream.

When we try to soft-offline a thp tail page, put_page() is called on the
tail page unthinkingly and VM_BUG_ON is triggered in put_compound_page().

This patch splits thp before going into the main body of soft-offlining.

Signed-off-by: Naoya Horiguchi <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Wu Fengguang <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Herton Ronaldo Krzesinski <[email protected]>
---
 mm/memory-failure.c |    8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 6de0d61..1bf1092 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1481,9 +1481,17 @@ int soft_offline_page(struct page *page, int flags)
 {
        int ret;
        unsigned long pfn = page_to_pfn(page);
+       struct page *hpage = compound_trans_head(page);
 
        if (PageHuge(page))
                return soft_offline_huge_page(page, flags);
+       if (PageTransHuge(hpage)) {
+               if (PageAnon(hpage) && unlikely(split_huge_page(hpage))) {
+                       pr_info("soft offline: %#lx: failed to split THP\n",
+                               pfn);
+                       return -EBUSY;
+               }
+       }
 
        ret = get_any_page(page, pfn, flags);
        if (ret < 0)
-- 
1.7.9.5

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