MM: Pass a PTE pointer to update_mmu_cache() rather than the PTE itself

On VIVT ARM, when we have multiple shared mappings of the same file
in the same MM, we need to ensure that we have coherency across all
copies.  We do this via make_coherent() by making the pages
uncacheable.

This used to work fine, until we allowed highmem with highpte - we
now have a page table which is mapped as required, and is not available
for modification via update_mmu_cache().

Ralf Beache suggested getting rid of the PTE value passed to
update_mmu_cache():

  On MIPS update_mmu_cache() calls __update_tlb() which walks pagetables
  to construct a pointer to the pte again.  Passing a pte_t * is much
  more elegant.  Maybe we might even replace the pte argument with the
  pte_t?

Ben Herrenschmidt would also like the pte pointer for PowerPC:

  Passing the ptep in there is exactly what I want.  I want that
  -instead- of the PTE value, because I have issue on some ppc cases,
  for I$/D$ coherency, where set_pte_at() may decide to mask out the
  _PAGE_EXEC.

So, pass in the mapped page table pointer into update_mmu_cache(), and
remove the PTE value, updating all implementations and call sites to
suit.

Includes a fix from Stephen Rothwell:

  sparc: fix fallout from update_mmu_cache API change

  Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>

Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

2 files changed, 3 insertions, 3 deletions

diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
index 21207e54825b..89f158731ce3 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -209,7 +209,7 @@ extern void paging_init(void);
  * corresponding HPTE into the hash table ahead of time, instead of
  * waiting for the inevitable extra hash-table miss exception.
  */
-extern void update_mmu_cache(struct vm_area_struct *, unsigned long, pte_t);
+extern void update_mmu_cache(struct vm_area_struct *, unsigned long, pte_t *);
 
 extern int gup_hugepd(hugepd_t *hugepd, unsigned pdshift, unsigned long addr,
                       unsigned long end, int write, struct page **pages, int *nr);
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index b9b152558f9c..311224cdb7ad 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -494,13 +494,13 @@ EXPORT_SYMBOL(flush_icache_user_range);
  * This must always be called with the pte lock held.
  */
 void update_mmu_cache(struct vm_area_struct *vma, unsigned long address,
-                      pte_t pte)
+                      pte_t *ptep)
 {
 #ifdef CONFIG_PPC_STD_MMU
         unsigned long access = 0, trap;
 
         /* We only want HPTEs for linux PTEs that have _PAGE_ACCESSED set */
-        if (!pte_young(pte) || address >= TASK_SIZE)
+        if (!pte_young(*ptep) || address >= TASK_SIZE)
                 return;
 
         /* We try to figure out if we are coming from an instruction