[ 067/117] um: Implement a custom pte_same() function

[Ben Hutchings]

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

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

From: Richard Weinberger <richard@xxxxxx>

commit f15b9000eb1d09bbaa4b0a6b2089d7e1f64e84b3 upstream.

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.

Analyzed-by: Hugh Dickins <hughd@xxxxxxxxxx>
Signed-off-by: Richard Weinberger <richard@xxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 arch/um/include/asm/pgtable.h |    6 ++++++
 1 file changed, 6 insertions(+)

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.


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/