linux-kernel - [PATCH 3.15 122/122] mm/numa: Remove BUG_ON() in __handle_mm

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Message-Id: <20140707235737.894790405@linuxfoundation.org>
Date:	Mon,  7 Jul 2014 16:58:04 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Rik van Riel <riel@...hat.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Sunil Pandey <sunil.k.pandey@...el.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>, linux-mm@...ck.org,
	lwoodman@...hat.com, dave.hansen@...el.com,
	Ingo Molnar <mingo@...nel.org>
Subject: [PATCH 3.15 122/122] mm/numa: Remove BUG_ON() in __handle_mm_fault()

3.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Rik van Riel <riel@...hat.com>

commit 107437febd495a50e2cd09c81bbaa84d30e57b07 upstream.

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>
Patrick McLean <chutzpah@...too.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 mm/memory.c |    3 ---
 1 file changed, 3 deletions(-)

--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3920,9 +3920,6 @@ static int __handle_mm_fault(struct mm_s
 		}
 	}

-	/* 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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