[PATCH v5 08/13] xen/page_alloc: introduce preserved page flags macro

[Carlo Nonato <carlo.nonato@xxxxxxxxxxxxxxx>]

PGC_static and PGC_extra are flags that needs to be preserved when assigning
a page. Define a new macro that groups those flags and use it instead of
or'ing every time.

The new macro is used also in free_heap_pages() allowing future commits to
extended it with other flags that must stop merging, as it now works for
PGC_static. PGC_extra is no harm here since it's only ever being set on
allocated pages.

Signed-off-by: Carlo Nonato <carlo.nonato@xxxxxxxxxxxxxxx>
Signed-off-by: Marco Solieri <marco.solieri@xxxxxxxxxxxxxxx>
---
v5:
- new patch
---
 xen/common/page_alloc.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 9ee3981bb5..3bf3120287 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -158,6 +158,8 @@
 #define PGC_static 0
 #endif
 
+#define preserved_flags (PGC_extra | PGC_static)
+
 #ifndef PGT_TYPE_INFO_INITIALIZER
 #define PGT_TYPE_INFO_INITIALIZER 0
 #endif
@@ -1504,7 +1506,7 @@ static void free_heap_pages(
             /* Merge with predecessor block? */
             if ( !mfn_valid(page_to_mfn(predecessor)) ||
                  !page_state_is(predecessor, free) ||
-                 (predecessor->count_info & PGC_static) ||
+                 (predecessor->count_info & preserved_flags) ||
                  (PFN_ORDER(predecessor) != order) ||
                  (page_to_nid(predecessor) != node) )
                 break;
@@ -1528,7 +1530,7 @@ static void free_heap_pages(
             /* Merge with successor block? */
             if ( !mfn_valid(page_to_mfn(successor)) ||
                  !page_state_is(successor, free) ||
-                 (successor->count_info & PGC_static) ||
+                 (successor->count_info & preserved_flags) ||
                  (PFN_ORDER(successor) != order) ||
                  (page_to_nid(successor) != node) )
                 break;
@@ -2365,7 +2367,7 @@ int assign_pages(
 
         for ( i = 0; i < nr; i++ )
         {
-            ASSERT(!(pg[i].count_info & ~(PGC_extra | PGC_static)));
+            ASSERT(!(pg[i].count_info & ~preserved_flags));
             if ( pg[i].count_info & PGC_extra )
                 extra_pages++;
         }
@@ -2425,7 +2427,7 @@ int assign_pages(
         page_set_owner(&pg[i], d);
         smp_wmb(); /* Domain pointer must be visible before updating refcnt. */
         pg[i].count_info =
-            (pg[i].count_info & (PGC_extra | PGC_static)) | PGC_allocated | 1;
+            (pg[i].count_info & preserved_flags) | PGC_allocated | 1;
 
         page_list_add_tail(&pg[i], page_to_list(d, &pg[i]));
     }
-- 
2.34.1