mm: soft offline: split thp at the beginning of soft_offline_page()

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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 6c5899b9034a..8b20278be6a6 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1476,9 +1476,17 @@ 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)