[PATCH] i386: clear_fixmap() should not use set_pte()

While not strictly required with the current code (as the upper half of
page table entries generated by __set_fixmap() cannot be non-zero due
to the second parameter of this function being 'unsigned long'), the
use of set_pte() in __set_fixmap() in the context of clear_fixmap() is
still improper with CONFIG_X86_PAE (see the respective comment in
include/asm-i386/pgtable-3level.h) and would turn into a bug if that
second parameter ever gets changed to a 64-bit type.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>

1 files changed, 5 insertions, 2 deletions

diff --git a/arch/i386/mm/pgtable.c b/arch/i386/mm/pgtable.c
index 10126e3f8174..65b5c0959033 100644
--- a/arch/i386/mm/pgtable.c
+++ b/arch/i386/mm/pgtable.c
@@ -95,8 +95,11 @@ static void set_pte_pfn(unsigned long vaddr, unsigned long pfn, pgprot_t flags)
                 return;
         }
         pte = pte_offset_kernel(pmd, vaddr);
-        /* <pfn,flags> stored as-is, to permit clearing entries */
-        set_pte(pte, pfn_pte(pfn, flags));
+        if (pgprot_val(flags))
+                /* <pfn,flags> stored as-is, to permit clearing entries */
+                set_pte(pte, pfn_pte(pfn, flags));
+        else
+                pte_clear(&init_mm, vaddr, pte);
 
         /*
          * It's enough to flush this one mapping.