[PATCH] ppc64: Fix pages marked dirty abusively

While working on 64K pages, I found this little buglet in our
update_mmu_cache() implementation.

The code calls __hash_page() passing it an "access" parameter (the type
of access that triggers the hash) containing the bits _PAGE_RW and
_PAGE_USER of the linux PTE.  The latter is useless in this case and the
former is wrong.  In fact, if we have a writeable PTE and we pass
_PAGE_RW to hash_page(), it will set _PAGE_DIRTY (since we track dirty
that way, by hash faulting !dirty) which is not what we want.

In fact, the correct fix is to always pass 0. That means that only
read-only or already dirty read write PTEs will be preloaded. The
(hopefully rare) case of a non dirty read write PTE can't be preloaded
this way, it will have to fault in hash_page on the actual access.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/arch/ppc64/mm/init.c b/arch/ppc64/mm/init.c
index c2157c9c3acbfc585f1cf3a729a28be861564259..be64b157afcef08477b926a31d921858e8065cab 100644 (file)
--- a/arch/ppc64/mm/init.c
+++ b/arch/ppc64/mm/init.c
@@ -799,8 +799,7 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned long ea,
        if (cpus_equal(vma->vm_mm->cpu_vm_mask, tmp))
                local = 1;
 
-       __hash_page(ea, pte_val(pte) & (_PAGE_USER|_PAGE_RW), vsid, ptep,
-                   0x300, local);
+       __hash_page(ea, 0, vsid, ptep, 0x300, local);
        local_irq_restore(flags);
 }