CRED: Wrap task credential accesses in the autofs filesystem

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: H. Peter Anvin <hpa@zytor.com>
Cc: autofs@linux.kernel.org
Signed-off-by: James Morris <jmorris@namei.org>

fs/autofs/inode.c

@@ -76,8 +76,8 @@ static int parse_options(char *options, int *pipefd, uid_t *uid, gid_t *gid,
 	substring_t args[MAX_OPT_ARGS];
 	int option;
 
-	*uid = current->uid;
-	*gid = current->gid;
+	*uid = current_uid();
+	*gid = current_gid();
 	*pgrp = task_pgrp_nr(current);
 
 	*minproto = *maxproto = AUTOFS_PROTO_VERSION;