CRED: Wrap task credential accesses in the filesystem subsystem

Wrap access to task credentials so that they can be separated more easily from
the task_struct during the introduction of COW creds.

Change most current->(|e|s|fs)[ug]id to current_(|e|s|fs)[ug]id().

Change some task->e?[ug]id to task_e?[ug]id().  In some places it makes more
sense to use RCU directly rather than a convenient wrapper; these will be
addressed by later patches.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index aec931e..39df95a 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -217,11 +217,11 @@
                 switch(pa->e_tag) {
                         case ACL_USER_OBJ:
 				/* (May have been checked already) */
-                                if (inode->i_uid == current->fsuid)
+				if (inode->i_uid == current_fsuid())
                                         goto check_perm;
                                 break;
                         case ACL_USER:
-                                if (pa->e_id == current->fsuid)
+				if (pa->e_id == current_fsuid())
                                         goto mask;
 				break;
                         case ACL_GROUP_OBJ: