mm: remove unnecessary WARN_ONCE in page_vma_mapped_walk().

A non present pmd entry can appear after pmd_lock is taken in
page_vma_mapped_walk(), even if THP migration is not enabled.  The
WARN_ONCE is unnecessary.

Link: http://lkml.kernel.org/r/20171003142606.12324-1-zi.yan@sent.com
Fixes: 616b8371539a ("mm: thp: enable thp migration in generic path")
Signed-off-by: Zi Yan <zi.yan@cs.rutgers.edu>
Reported-by: Abdul Haleem <abdhalee@linux.vnet.ibm.com>
Tested-by: Abdul Haleem <abdhalee@linux.vnet.ibm.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index 6a03946469a99eb535851194f519893a5e8a2d11..eb462e7db0a95972d3f59439938162fd49f8c025 100644 (file)
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -167,8 +167,7 @@ restart:
                                                return not_found(pvmw);
                                        return true;
                                }
-                       } else
-                               WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
+                       }
                        return not_found(pvmw);
                } else {
                        /* THP pmd was split under us: handle on pte level */