CRED: Wrap task credential accesses in the autofs4 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: Ian Kent <raven@themaw.net>
Cc: autofs@linux.kernel.org
Signed-off-by: James Morris <jmorris@namei.org>

fs/autofs4/inode.c

@@ -235,8 +235,8 @@ 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 = AUTOFS_MIN_PROTO_VERSION;

fs/autofs4/waitq.c

@@ -391,8 +391,8 @@ int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
 		memcpy(&wq->name, &qstr, sizeof(struct qstr));
 		wq->dev = autofs4_get_dev(sbi);
 		wq->ino = autofs4_get_ino(sbi);
-		wq->uid = current->uid;
-		wq->gid = current->gid;
+		wq->uid = current_uid();
+		wq->gid = current_gid();
 		wq->pid = current->pid;
 		wq->tgid = current->tgid;
 		wq->status = -EINTR; /* Status return if interrupted */