linux-kernel - [tip:sched/core] mm/numa: Remove BUG_ON() in __handle_mm

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Message-ID: <tip-107437febd495a50e2cd09c81bbaa84d30e57b07@git.kernel.org>
Date:	Thu, 8 May 2014 03:43:19 -0700
From:	tip-bot for Rik van Riel <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	torvalds@...ux-foundation.org, kirill.shutemov@...ux.intel.com,
	peterz@...radead.org, hannes@...xchg.org,
	n-horiguchi@...jp.nec.com, riel@...hat.com,
	akpm@...ux-foundation.org, mgorman@...e.de,
	sunil.k.pandey@...el.com, tglx@...utronix.de
Subject: [tip:sched/core] mm/numa: Remove BUG_ON() in __handle_mm_fault()

Commit-ID:  107437febd495a50e2cd09c81bbaa84d30e57b07
Gitweb:     http://git.kernel.org/tip/107437febd495a50e2cd09c81bbaa84d30e57b07
Author:     Rik van Riel <riel@...hat.com>
AuthorDate: Tue, 29 Apr 2014 15:36:15 -0400
Committer:  Ingo Molnar <mingo@...nel.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@...hat.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Reported-by: Sunil Pandey <sunil.k.pandey@...el.com>
Signed-off-by: Peter Zijlstra <peterz@...radead.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Johannes Weiner <hannes@...xchg.org>
Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mel Gorman <mgorman@...e.de>
Cc: linux-mm@...ck.org
Cc: lwoodman@...hat.com
Cc: dave.hansen@...el.com
Link: http://lkml.kernel.org/r/20140429153615.2d72098e@annuminas.surriel.com
Signed-off-by: Ingo Molnar <mingo@...nel.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
--
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