mempolicy: don't call mpol_set_nodemask() when no_context

No need to call mpol_set_nodemask() when we have no context for the
mempolicy.  This can occur when we're parsing a tmpfs 'mpol' mount option.
 Just save the raw nodemask in the mempolicy's w.user_nodemask member for
use when a tmpfs/shmem file is created.  mpol_shared_policy_init() will
"contextualize" the policy for the new file based on the creating task's
context.

Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Ravikiran Thirumalai <kiran@scalex86.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/mempolicy.c

@@ -2239,7 +2239,10 @@ int mpol_parse_str(char *str, struct mempolicy **mpol, int no_context)
 	if (IS_ERR(new))
 		goto out;
 
-	{
+	if (no_context) {
+		/* save for contextualization */
+		new->w.user_nodemask = nodes;
+	} else {
 		int ret;
 		NODEMASK_SCRATCH(scratch);
 		if (scratch) {
@@ -2255,10 +2258,6 @@ int mpol_parse_str(char *str, struct mempolicy **mpol, int no_context)
 		}
 	}
 	err = 0;
-	if (no_context) {
-		/* save for contextualization */
-		new->w.user_nodemask = nodes;
-	}
 
 out:
 	/* Restore string for error message */