x86: pat: Clean up req_type special case for reserve_memtype()

Commit:

  b6ff32d: x86, PAT: Consolidate code in pat_x_mtrr_type() and reserve_memtype()

consolidated code in pat_x_mtrr_type() and reserve_memtype(),
which removed the special case (req_type is -1) for the
PAT-enabled part.

We should also change comments and the PAT-disabled part.

Signed-off-by: Xiaotian Feng <dfeng@redhat.com>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
LKML-Reference: <1257844987-7906-1-git-send-email-dfeng@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/mm/pat.c

@@ -355,9 +355,6 @@ static int free_ram_pages_type(u64 start, u64 end)
  * - _PAGE_CACHE_UC_MINUS
  * - _PAGE_CACHE_UC
  *
- * req_type will have a special case value '-1', when requester want to inherit
- * the memory type from mtrr (if WB), existing PAT, defaulting to UC_MINUS.
- *
  * If new_type is NULL, function will return an error if it cannot reserve the
  * region with req_type. If new_type is non-NULL, function will return
  * available type in new_type in case of no error. In case of any error
@@ -377,9 +374,7 @@ int reserve_memtype(u64 start, u64 end, unsigned long req_type,
 	if (!pat_enabled) {
 		/* This is identical to page table setting without PAT */
 		if (new_type) {
-			if (req_type == -1)
+			if (req_type == _PAGE_CACHE_WC)
-				*new_type = _PAGE_CACHE_WB;
-			else if (req_type == _PAGE_CACHE_WC)
 				*new_type = _PAGE_CACHE_UC_MINUS;
 			else
 				*new_type = req_type & _PAGE_CACHE_MASK;