[PATCH] Enable mprotect on huge pages

2.6.16-rc3 uses hugetlb on-demand paging, but it doesn_t support hugetlb
mprotect.

From: David Gibson <david@gibson.dropbear.id.au>

  Remove a test from the mprotect() path which checks that the mprotect()ed
  range on a hugepage VMA is hugepage aligned (yes, really, the sense of
  is_aligned_hugepage_range() is the opposite of what you'd guess :-/).

  In fact, we don't need this test.  If the given addresses match the
  beginning/end of a hugepage VMA they must already be suitably aligned.  If
  they don't, then mprotect_fixup() will attempt to split the VMA.  The very
  first test in split_vma() will check for a badly aligned address on a
  hugepage VMA and return -EINVAL if necessary.

From: "Chen, Kenneth W" <kenneth.w.chen@intel.com>

  On i386 and x86-64, pte flag _PAGE_PSE collides with _PAGE_PROTNONE.  The
  identify of hugetlb pte is lost when changing page protection via mprotect.
  A page fault occurs later will trigger a bug check in huge_pte_alloc().

  The fix is to always make new pte a hugetlb pte and also to clean up
  legacy code where _PAGE_PRESENT is forced on in the pre-faulting day.

Signed-off-by: Zhang Yanmin <yanmin.zhang@intel.com>
Cc: David Gibson <david@gibson.dropbear.id.au>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: William Lee Irwin III <wli@holomorphy.com>
Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 2 insertions, 3 deletions

diff --git a/include/asm-i386/pgtable.h b/include/asm-i386/pgtable.h
index 088a945bf26b..ee056c41a9fb 100644
--- a/include/asm-i386/pgtable.h
+++ b/include/asm-i386/pgtable.h
@@ -219,13 +219,12 @@ extern unsigned long pg0[];
  * The following only work if pte_present() is true.
  * Undefined behaviour if not..
  */
-#define __LARGE_PTE (_PAGE_PSE | _PAGE_PRESENT)
 static inline int pte_user(pte_t pte)           { return (pte).pte_low & _PAGE_USER; }
 static inline int pte_read(pte_t pte)           { return (pte).pte_low & _PAGE_USER; }
 static inline int pte_dirty(pte_t pte)          { return (pte).pte_low & _PAGE_DIRTY; }
 static inline int pte_young(pte_t pte)          { return (pte).pte_low & _PAGE_ACCESSED; }
 static inline int pte_write(pte_t pte)          { return (pte).pte_low & _PAGE_RW; }
-static inline int pte_huge(pte_t pte)           { return ((pte).pte_low & __LARGE_PTE) == __LARGE_PTE; }
+static inline int pte_huge(pte_t pte)           { return (pte).pte_low & _PAGE_PSE; }
 
 /*
  * The following only works if pte_present() is not true.
@@ -242,7 +241,7 @@ static inline pte_t pte_mkexec(pte_t pte)	{ (pte).pte_low |= _PAGE_USER; return
 static inline pte_t pte_mkdirty(pte_t pte)      { (pte).pte_low |= _PAGE_DIRTY; return pte; }
 static inline pte_t pte_mkyoung(pte_t pte)      { (pte).pte_low |= _PAGE_ACCESSED; return pte; }
 static inline pte_t pte_mkwrite(pte_t pte)      { (pte).pte_low |= _PAGE_RW; return pte; }
-static inline pte_t pte_mkhuge(pte_t pte)       { (pte).pte_low |= __LARGE_PTE; return pte; }
+static inline pte_t pte_mkhuge(pte_t pte)       { (pte).pte_low |= _PAGE_PSE; return pte; }
 
 #ifdef CONFIG_X86_PAE
 # include <asm/pgtable-3level.h>