[PATCH] mm: powerpc ptlock comments

Update comments (only) on page_table_lock and mmap_sem in arch/powerpc.
Removed the comment on page_table_lock from hash_huge_page: since it's no
longer taking page_table_lock itself, it's irrelevant whether others are; but
how it is safe (even against huge file truncation?) I can't say.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 4bd7b0a..ed6ed2e 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -495,7 +495,7 @@
  * We use it to preload an HPTE into the hash table corresponding to
  * the updated linux PTE.
  * 
- * This must always be called with the mm->page_table_lock held
+ * 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)