[PATCH] mm: remove unnecessary WARN_ONCE in page_vma_mapped_walk().

[Zi Yan]

From: Zi Yan <zi....@cs.rutgers.edu>

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.

Fixes: 616b8371539a ("mm: thp: enable thp migration in generic path")
Reported-and-tested-by: Abdul Haleem <abdha...@linux.vnet.ibm.com>
Signed-off-by: Zi Yan <zi....@cs.rutgers.edu>
Cc: "Kirill A. Shutemov" <kirill.shute...@linux.intel.com>
Cc: Anshuman Khandual <khand...@linux.vnet.ibm.com>
Cc: Andrew Morton <a...@linux-foundation.org>
---
 mm/page_vma_mapped.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index 6a03946469a9..eb462e7db0a9 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -167,8 +167,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
                                                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 */
-- 
2.14.1