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Subject[ 07/20] mm: soft offline: split thp at the beginning of soft_offline_page()
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3.4-stable review patch.  If anyone has any objections, please let me know.

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

From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>

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 <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Andi Kleen <andi.kleen@intel.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
mm/memory-failure.c | 8 ++++++++
1 file changed, 8 insertions(+)

--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1481,9 +1481,17 @@ int soft_offline_page(struct page *page,
{
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)



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