[PATCH] mm: move_pte to remap ZERO_PAGE

Move the ZERO_PAGE remapping complexity to the move_pte macro in
asm-generic, have it conditionally depend on
__HAVE_ARCH_MULTIPLE_ZERO_PAGE, which gets defined for MIPS.

For architectures without __HAVE_ARCH_MULTIPLE_ZERO_PAGE, move_pte becomes
a noop.

From: Hugh Dickins <hugh@veritas.com>

Fix nasty little bug we've missed in Nick's mremap move ZERO_PAGE patch.
The "pte" at that point may be a swap entry or a pte_file entry: we must
check pte_present before perhaps corrupting such an entry.

Patch below against 2.6.14-rc2-mm1, but the same bug is in 2.6.14-rc2's
mm/mremap.c, and more dangerous there since it's affecting all arches: I
think the safest course is to send Nick's patch and Yoichi's build fix and
this fix (build tested) on to Linus - so only MIPS can be affected.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/asm-mips/pgtable.h b/include/asm-mips/pgtable.h
index cbd1672c94cb..eaf5d9b3a0e1 100644
--- a/include/asm-mips/pgtable.h
+++ b/include/asm-mips/pgtable.h
@@ -68,6 +68,8 @@ extern unsigned long zero_page_mask;
 #define ZERO_PAGE(vaddr) \
         (virt_to_page(empty_zero_page + (((unsigned long)(vaddr)) & zero_page_mask)))
 
+#define __HAVE_ARCH_MULTIPLE_ZERO_PAGE
+
 extern void paging_init(void);
 
 /*