linux-kernel - [PATCH 1/2] um: Implement a custom pte

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Message-Id: <1334418731-16498-1-git-send-email-richard@nod.at>
Date:	Sat, 14 Apr 2012 17:52:10 +0200
From:	Richard Weinberger <richard@....at>
To:	user-mode-linux-devel@...ts.sourceforge.net
Cc:	linux-kernel@...r.kernel.org, hughd@...gle.com,
	Richard Weinberger <richard@....at>, stable@...nel.org
Subject: [PATCH 1/2] um: Implement a custom pte_same() function

UML uses the _PAGE_NEWPAGE flag to mark pages which are not jet
installed on the host side using mmap().
pte_same() has to ignore this flag, otherwise unuse_pte_range()
is unable to unuse the page because two identical
page tables entries with different _PAGE_NEWPAGE flags would not
match and swapoff() would never return.

CC: stable@...nel.org
Analyzed-by: Hugh Dickins <hughd@...gle.com>
Signed-off-by: Richard Weinberger <richard@....at>
---
 arch/um/include/asm/pgtable.h |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/arch/um/include/asm/pgtable.h b/arch/um/include/asm/pgtable.h
index 6a3f984..294254e 100644
--- a/arch/um/include/asm/pgtable.h
+++ b/arch/um/include/asm/pgtable.h
@@ -273,6 +273,12 @@ static inline void set_pte(pte_t *pteptr, pte_t pteval)
 }
 #define set_pte_at(mm,addr,ptep,pteval) set_pte(ptep,pteval)
 
+#define __HAVE_ARCH_PTE_SAME
+static inline int pte_same(pte_t pte_a, pte_t pte_b)
+{
+	return !((pte_val(pte_a) ^ pte_val(pte_b)) & ~_PAGE_NEWPAGE);
+}
+
 /*
  * Conversion functions: convert a page and protection to a page entry,
  * and a page entry and page directory to the page they refer to.
-- 
1.7.7.3

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