x86: pat.c more trivial changes

 - add BUG statement to catch invalid start and end parameters
 - No need to track the actual type in both req_type and actual_type --
   keep req_type unchanged.
 - removed (IMHO) superfluous comments

Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Cc: Suresh B Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 8 insertions, 13 deletions

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index a6507bfb12a7..c996a3641200 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -200,7 +200,8 @@ int reserve_memtype(u64 start, u64 end, unsigned long req_type,
         unsigned long actual_type;
         int err = 0;
 
-        /* Only track when pat_enabled */
+        BUG_ON(start >= end); /* end is exclusive */
+
         if (!pat_enabled) {
                 /* This is identical to page table setting without PAT */
                 if (new_type) {
@@ -228,17 +229,13 @@ int reserve_memtype(u64 start, u64 end, unsigned long req_type,
                  */
                 u8 mtrr_type = mtrr_type_lookup(start, end);
 
-                if (mtrr_type == MTRR_TYPE_WRBACK) {
-                        req_type = _PAGE_CACHE_WB;
+                if (mtrr_type == MTRR_TYPE_WRBACK)
                         actual_type = _PAGE_CACHE_WB;
-                } else {
-                        req_type = _PAGE_CACHE_UC_MINUS;
+                else
                         actual_type = _PAGE_CACHE_UC_MINUS;
-                }
-        } else {
-                req_type &= _PAGE_CACHE_MASK;
-                actual_type = pat_x_mtrr_type(start, end, req_type);
-        }
+        } else
+                actual_type = pat_x_mtrr_type(start, end,
+                                              req_type & _PAGE_CACHE_MASK);
 
         new  = kmalloc(sizeof(struct memtype), GFP_KERNEL);
         if (!new)
@@ -406,10 +403,8 @@ int free_memtype(u64 start, u64 end)
         struct memtype *entry;
         int err = -EINVAL;
 
-        /* Only track when pat_enabled */
-        if (!pat_enabled) {
+        if (!pat_enabled)
                 return 0;
-        }
 
         /* Low ISA region is always mapped WB. No need to track */
         if (is_ISA_range(start, end - 1))