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, 17 insertions, 12 deletions

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index acb5ee3587c3..1311dc4a3888 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -114,7 +114,7 @@ static void mpol_rebind_policy(struct mempolicy *pol,
                                const nodemask_t *newmask);
 
 /* Do sanity checking on a policy */
-static int mpol_check_policy(int mode, nodemask_t *nodes)
+static int mpol_check_policy(unsigned short mode, nodemask_t *nodes)
 {
         int was_empty, is_empty;
 
@@ -159,6 +159,8 @@ static int mpol_check_policy(int mode, nodemask_t *nodes)
                 if (!was_empty && is_empty)
                         return -EINVAL;
                 break;
+        default:
+                BUG();
         }
         return 0;
 }
@@ -185,7 +187,7 @@ static int is_valid_nodemask(nodemask_t *nodemask)
 }
 
 /* Create a new policy */
-static struct mempolicy *mpol_new(int mode, nodemask_t *nodes)
+static struct mempolicy *mpol_new(unsigned short mode, nodemask_t *nodes)
 {
         struct mempolicy *policy;
 
@@ -218,6 +220,8 @@ static struct mempolicy *mpol_new(int mode, nodemask_t *nodes)
                 }
                 policy->v.nodes = *nodes;
                 break;
+        default:
+                BUG();
         }
         policy->policy = mode;
         policy->cpuset_mems_allowed = cpuset_mems_allowed(current);
@@ -462,7 +466,7 @@ static void mpol_set_task_struct_flag(void)
 }
 
 /* Set the process memory policy */
-static long do_set_mempolicy(int mode, nodemask_t *nodes)
+static long do_set_mempolicy(unsigned short mode, nodemask_t *nodes)
 {
         struct mempolicy *new;
 
@@ -759,7 +763,7 @@ static struct page *new_vma_page(struct page *page, unsigned long private, int *
 #endif
 
 static long do_mbind(unsigned long start, unsigned long len,
-                     unsigned long mode, nodemask_t *nmask,
+                     unsigned short mode, nodemask_t *nmask,
                      unsigned long flags)
 {
         struct vm_area_struct *vma;
@@ -769,9 +773,8 @@ static long do_mbind(unsigned long start, unsigned long len,
         int err;
         LIST_HEAD(pagelist);
 
-        if ((flags & ~(unsigned long)(MPOL_MF_STRICT |
-                                      MPOL_MF_MOVE | MPOL_MF_MOVE_ALL))
-            || mode > MPOL_MAX)
+        if (flags & ~(unsigned long)(MPOL_MF_STRICT |
+                                     MPOL_MF_MOVE | MPOL_MF_MOVE_ALL))
                 return -EINVAL;
         if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
                 return -EPERM;
@@ -804,7 +807,7 @@ static long do_mbind(unsigned long start, unsigned long len,
         if (!new)
                 flags |= MPOL_MF_DISCONTIG_OK;
 
-        pr_debug("mbind %lx-%lx mode:%ld nodes:%lx\n",start,start+len,
+        pr_debug("mbind %lx-%lx mode:%d nodes:%lx\n", start, start + len,
                  mode, nmask ? nodes_addr(*nmask)[0] : -1);
 
         down_write(&mm->mmap_sem);
@@ -905,6 +908,8 @@ asmlinkage long sys_mbind(unsigned long start, unsigned long len,
         nodemask_t nodes;
         int err;
 
+        if (mode >= MPOL_MAX)
+                return -EINVAL;
         err = get_nodes(&nodes, nmask, maxnode);
         if (err)
                 return err;
@@ -918,7 +923,7 @@ asmlinkage long sys_set_mempolicy(int mode, unsigned long __user *nmask,
         int err;
         nodemask_t nodes;
 
-        if (mode < 0 || mode > MPOL_MAX)
+        if (mode < 0 || mode >= MPOL_MAX)
                 return -EINVAL;
         err = get_nodes(&nodes, nmask, maxnode);
         if (err)
@@ -1201,7 +1206,7 @@ static unsigned interleave_nodes(struct mempolicy *policy)
  */
 unsigned slab_node(struct mempolicy *policy)
 {
-        int pol = policy ? policy->policy : MPOL_DEFAULT;
+        unsigned short pol = policy ? policy->policy : MPOL_DEFAULT;
 
         switch (pol) {
         case MPOL_INTERLEAVE:
@@ -1635,7 +1640,7 @@ restart:
         return 0;
 }
 
-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 *policy_nodes)
 {
         info->root = RB_ROOT;
@@ -1830,7 +1835,7 @@ static inline int mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)
         char *p = buffer;
         int l;
         nodemask_t nodes;
-        int mode = pol ? pol->policy : MPOL_DEFAULT;
+        unsigned short mode = pol ? pol->policy : MPOL_DEFAULT;
 
         switch (mode) {
         case MPOL_DEFAULT: