linux-kernel - [ 093/135] mm: Fix generic hugetlb pte check return type.

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Message-Id: <20131011193955.369035517@linuxfoundation.org>
Date:	Fri, 11 Oct 2013 12:39:34 -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, Gurudas Pai <gurudas.pai@...cle.com>,
	"David S. Miller" <davem@...emloft.net>,
	David Rientjes <rientjes@...gle.com>
Subject: [ 093/135] mm: Fix generic hugetlb pte check return type.

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

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

From: David Miller <davem@...emloft.net>

[ Upstream commit 26794942461f438a6bc725ec7294b08a6bd782c4 ]

The include/asm-generic/hugetlb.h stubs that just vector huge_pte_*()
calls to the pte_*() implementations won't work in certain situations.

x86 and sparc, for example, return "unsigned long" from the bit
checks, and just go "return pte_val(pte) & PTE_BIT_FOO;"

But since huge_pte_*() returns 'int', if any high bits on 64-bit are
relevant, they get chopped off.

The net effect is that we can loop forever trying to COW a huge page,
because the huge_pte_write() check signals false all the time.

Reported-by: Gurudas Pai <gurudas.pai@...cle.com>
Tested-by: Gurudas Pai <gurudas.pai@...cle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Acked-by: David Rientjes <rientjes@...gle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 include/asm-generic/hugetlb.h |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/include/asm-generic/hugetlb.h
+++ b/include/asm-generic/hugetlb.h
@@ -6,12 +6,12 @@ static inline pte_t mk_huge_pte(struct p
 	return mk_pte(page, pgprot);
 }
 
-static inline int huge_pte_write(pte_t pte)
+static inline unsigned long huge_pte_write(pte_t pte)
 {
 	return pte_write(pte);
 }
 
-static inline int huge_pte_dirty(pte_t pte)
+static inline unsigned long huge_pte_dirty(pte_t pte)
 {
 	return pte_dirty(pte);
 }


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