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Commit c3901e72 authored by Naoya Horiguchi's avatar Naoya Horiguchi Committed by Linus Torvalds
Browse files

mm: hwpoison: fix thp split handling in memory_failure() 

When memory_failure() runs on a thp tail page after pmd is split, we
trigger the following VM_BUG_ON_PAGE():

   page:ffffd7cd819b0040 count:0 mapcount:0 mapping:         (null) index:0x1
   flags: 0x1fffc000400000(hwpoison)
   page dumped because: VM_BUG_ON_PAGE(!page_count(p))
   ------------[ cut here ]------------
   kernel BUG at /src/linux-dev/mm/memory-failure.c:1132!

memory_failure() passed refcount and page lock from tail page to head
page, which is not needed because we can pass any subpage to
split_huge_page().

Fixes: 61f5d698 ("mm: re-enable THP")
Link: http://lkml.kernel.org/r/1477961577-7183-1-git-send-email-n-horiguchi@ah.jp.nec.com


Signed-off-by: default avatarNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: <stable@vger.kernel.org>	[4.5+]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent dd111be6

mm/memory-failure.c

+5 −7
Original line number Diff line number Diff line
@@ -1112,10 +1112,10 @@ int memory_failure(unsigned long pfn, int trapno, int flags) 
	}



	if (!PageHuge(p) && PageTransHuge(hpage)) {

		lock_page(hpage);

		if (!PageAnon(hpage) || unlikely(split_huge_page(hpage))) {

			unlock_page(hpage);

			if (!PageAnon(hpage))

		lock_page(p);

		if (!PageAnon(p) || unlikely(split_huge_page(p))) {

			unlock_page(p);

			if (!PageAnon(p))

				pr_err("Memory failure: %#lx: non anonymous thp\n",

					pfn);

			else
@@ -1126,9 +1126,7 @@ int memory_failure(unsigned long pfn, int trapno, int flags) 
			put_hwpoison_page(p);

			return -EBUSY;

		}

		unlock_page(hpage);

		get_hwpoison_page(p);

		put_hwpoison_page(hpage);

		unlock_page(p);

		VM_BUG_ON_PAGE(!page_count(p), p);

		hpage = compound_head(p);

	}