Add a function to convert a policy into a string.

The policy passed to this function must be properly protected. There are
two cases of policies that are of interest:

1. The memory policies in vm_area_struct

Mmap_sem lock must be held in order to insure that the policy is not changed
under us. The patch that extends smap to display the memory policy holds
the mmap_sem when displaying the memory policy.

2. The policy in task_struct

The policy is not protected by any lock and may therefore only be accessed
in the context of the task.


Syntax of textual representation:

default
preferred=<nodenumber>
bind=<nodelist>
interleave=<nodelist>

Signed-off-by: Christoph Lameter <christoph@lameter.com>

Index: linux-2.6.13-rc6/mm/mempolicy.c
===================================================================
--- linux-2.6.13-rc6.orig/mm/mempolicy.c	2005-08-15 10:57:55.000000000 -0700
+++ linux-2.6.13-rc6/mm/mempolicy.c	2005-08-15 10:58:26.000000000 -0700
@@ -1224,3 +1224,67 @@ void numa_default_policy(void)
 {
 	sys_set_mempolicy(MPOL_DEFAULT, NULL, 0);
 }
+
+static const char *policy_types[] = { "default", "prefer", "bind", "interleave" };
+
+/*
+ * Convert a mempolicy into a string.
+ * Returns the number of characters in buffer (if positive)
+ * or an error (negative)
+ *
+ * Can only be used to access policies in vm_area_struct and must
+ * hold a readlock on mmap_sem to prevent the policy to be changed
+ * under us.
+ *
+ * There is no protection for the policy pointer in the task
+ * struct. Therefore this function may not be used outside
+ * of the context of a task to display the task policy.
+ */
+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;
+
+	switch (mode) {
+	case MPOL_DEFAULT:
+		nodes_clear(nodes);
+		break;
+
+	case MPOL_PREFERRED:
+		nodes_clear(nodes);
+		node_set(pol->v.preferred_node, nodes);
+		break;
+
+	case MPOL_BIND:
+		get_zonemask(pol, &nodes);
+		break;
+
+	case MPOL_INTERLEAVE:
+		nodes = pol->v.nodes;
+		break;
+
+	default:
+		BUG();
+		return -EFAULT;
+	}
+
+	l = strlen(policy_types[mode]);
+	if (buffer + maxlen < p + l + 1)
+		return -ENOSPC;
+
+	strcpy(p, policy_types[mode]);
+	p += l;
+
+	if (!nodes_empty(nodes)) {
+
+		if (buffer + maxlen < p + 2)
+			return -ENOSPC;
+
+		*p++ = '=';
+	 	p += nodelist_scnprintf(p, buffer + maxlen - p, nodes);
+	}
+	return p - buffer;
+}
+
Index: linux-2.6.13-rc6/include/linux/mempolicy.h
===================================================================
--- linux-2.6.13-rc6.orig/include/linux/mempolicy.h	2005-08-15 10:48:49.000000000 -0700
+++ linux-2.6.13-rc6/include/linux/mempolicy.h	2005-08-15 10:58:04.000000000 -0700
@@ -153,6 +153,9 @@ struct mempolicy *mpol_shared_policy_loo
 extern void numa_default_policy(void);
 extern void numa_policy_init(void);
 
+/* Conversion functions */
+int mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol);
+
 #else
 
 struct mempolicy {};