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

[ Upstream commit 286c469a988fbaf68e3a97ddf1e6c245c1446968 ]

Memory error handler calls try_to_unmap() for error pages in various
states.  If the error page is a mlocked page, error handling could fail
with "still referenced by 1 users" message.  This is because the page is
linked to and stays in lru cache after the following call chain.

  try_to_unmap_one
    page_remove_rmap
      clear_page_mlock
        putback_lru_page
          lru_cache_add

memory_failure() calls shake_page() to hanlde the similar issue, but
current code doesn't cover because shake_page() is called only before
try_to_unmap().  So this patches adds shake_page().

Fixes: 23a003bfd23ea9ea0b7756b920e51f64b284b468 ("mm/madvise: pass return code 
of memory_failure() to userspace")
Link: http://lkml.kernel.org/r/20170417055948.GM31394@yexl-desktop
Link: 
http://lkml.kernel.org/r/1493197841-23986-3-git-send-email-n-horigu...@ah.jp.nec.com
Signed-off-by: Naoya Horiguchi <n-horigu...@ah.jp.nec.com>
Reported-by: kernel test robot <l...@intel.com>
Cc: Xiaolong Ye <xiaolong...@intel.com>
Cc: Chen Gong <gong.c...@linux.intel.com>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
---
 mm/memory-failure.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 5aa71a82ca73..851efb004857 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -921,6 +921,7 @@ static int hwpoison_user_mappings(struct page *p, unsigned 
long pfn,
        int ret;
        int kill = 1, forcekill;
        struct page *hpage = *hpagep;
+       bool mlocked = PageMlocked(hpage);
 
        /*
         * Here we are interested only in user-mapped pages, so skip any
@@ -984,6 +985,13 @@ static int hwpoison_user_mappings(struct page *p, unsigned 
long pfn,
                pr_err("Memory failure: %#lx: failed to unmap page 
(mapcount=%d)\n",
                       pfn, page_mapcount(hpage));
 
+       /*
+        * try_to_unmap() might put mlocked page in lru cache, so call
+        * shake_page() again to ensure that it's flushed.
+        */
+       if (mlocked)
+               shake_page(hpage, 0);
+
        /*
         * Now that the dirty bit has been propagated to the
         * struct page and all unmaps done we can decide if
-- 
2.14.1

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