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

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: Ben Hutchings <ben@decadent.org.uk>

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 5bd5bb1..1b03878 100644 (file)
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1475,9 +1475,17 @@ 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)