mempolicy: convert MPOL constants to enum

The mempolicy mode constants, MPOL_DEFAULT, MPOL_PREFERRED, MPOL_BIND, and
MPOL_INTERLEAVE, are better declared as part of an enum since they are
sequentially numbered and cannot be combined.

The policy member of struct mempolicy is also converted from type short to
type unsigned short.  A negative policy does not have any legitimate meaning,
so it is possible to change its type in preparation for adding optional mode
flags later.

The equivalent member of struct shmem_sb_info is also changed from int to
unsigned short.

For compatibility, the policy formal to get_mempolicy() remains as a pointer
to an int:

	int get_mempolicy(int *policy, unsigned long *nmask,
			  unsigned long maxnode, unsigned long addr,
			  unsigned long flags);

although the only possible values is the range of type unsigned short.

Cc: Paul Jackson <pj@sgi.com>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 9 deletions

diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
index b8b3da7a3315..389a06e8ee21 100644
--- a/include/linux/mempolicy.h
+++ b/include/linux/mempolicy.h
@@ -9,12 +9,13 @@
  */
 
 /* Policies */
-#define MPOL_DEFAULT    0
-#define MPOL_PREFERRED  1
-#define MPOL_BIND       2
-#define MPOL_INTERLEAVE 3
-
-#define MPOL_MAX MPOL_INTERLEAVE
+enum {
+        MPOL_DEFAULT,
+        MPOL_PREFERRED,
+        MPOL_BIND,
+        MPOL_INTERLEAVE,
+        MPOL_MAX,       /* always last member of enum */
+};
 
 /* Flags for get_mem_policy */
 #define MPOL_F_NODE     (1<<0)  /* return next IL mode instead of node mask */
@@ -64,7 +65,7 @@ struct mm_struct;
  */
 struct mempolicy {
         atomic_t refcnt;
-        short policy;   /* See MPOL_* above */
+        unsigned short policy;  /* See MPOL_* above */
         union {
                 short            preferred_node; /* preferred */
                 nodemask_t       nodes;         /* interleave/bind */
@@ -134,7 +135,7 @@ struct shared_policy {
         spinlock_t lock;
 };
 
-void mpol_shared_policy_init(struct shared_policy *info, int policy,
+void mpol_shared_policy_init(struct shared_policy *info, unsigned short policy,
                                 nodemask_t *nodes);
 int mpol_set_shared_policy(struct shared_policy *info,
                                 struct vm_area_struct *vma,
@@ -202,7 +203,7 @@ static inline int mpol_set_shared_policy(struct shared_policy *info,
 }
 
 static inline void mpol_shared_policy_init(struct shared_policy *info,
-                                        int policy, nodemask_t *nodes)
+                                unsigned short policy, nodemask_t *nodes)
 {
 }