powerpc/mm: Make clear_fixmap() actually work

The clear_fixmap() routine issues map_page() with flags set to 0.
Currently this causes a BUG_ON() inside the map_page(), as it assumes
that a PTE should be clear before mapping.

This patch makes the map_page() to trigger the BUG_ON() only if the
flags were set.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Acked-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
index 38ff35f2142a..22972cd83cc9 100644
--- a/arch/powerpc/mm/pgtable_32.c
+++ b/arch/powerpc/mm/pgtable_32.c
@@ -266,7 +266,8 @@ int map_page(unsigned long va, phys_addr_t pa, int flags)
                 /* The PTE should never be already set nor present in the
                  * hash table
                  */
-                BUG_ON(pte_val(*pg) & (_PAGE_PRESENT | _PAGE_HASHPTE));
+                BUG_ON((pte_val(*pg) & (_PAGE_PRESENT | _PAGE_HASHPTE)) &&
+                       flags);
                 set_pte_at(&init_mm, va, pg, pfn_pte(pa >> PAGE_SHIFT,
                                                      __pgprot(flags)));
         }