[tip:sched/core] mm/numa: Remove BUG_ON() in __handle_mm_fault()

[tip-bot for Rik van Riel <tipbot@zytor.com>]

Commit-ID:  107437febd495a50e2cd09c81bbaa84d30e57b07
Gitweb:     http://git.kernel.org/tip/107437febd495a50e2cd09c81bbaa84d30e57b07
Author:     Rik van Riel <riel@redhat.com>
AuthorDate: Tue, 29 Apr 2014 15:36:15 -0400
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 7 May 2014 13:33:48 +0200

mm/numa: Remove BUG_ON() in __handle_mm_fault()

Changing PTEs and PMDs to pte_numa & pmd_numa is done with the
mmap_sem held for reading, which means a pmd can be instantiated
and turned into a numa one while __handle_mm_fault() is examining
the value of old_pmd.

If that happens, __handle_mm_fault() should just return and let
the page fault retry, instead of throwing an oops. This is
handled by the test for pmd_trans_huge(*pmd) below.

Signed-off-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reported-by: Sunil Pandey <sunil.k.pandey@intel.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: linux-mm@kvack.org
Cc: lwoodman@redhat.com
Cc: dave.hansen@intel.com
Link: http://lkml.kernel.org/r/20140429153615.2d72098e@annuminas.surriel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 mm/memory.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index d0f0bef..9c2dc65 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3900,9 +3900,6 @@ static int __handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 		}
 	}
 
-	/* THP should already have been handled */
-	BUG_ON(pmd_numa(*pmd));
-
 	/*
 	 * Use __pte_alloc instead of pte_alloc_map, because we can't
 	 * run pte_offset_map on the pmd, if an huge pmd could