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/dquot.c b/fs/dquot.c
index 5e95261..c237ccc 100644
--- a/fs/dquot.c
+++ b/fs/dquot.c
@@ -874,7 +874,7 @@
 
 	switch (dquot->dq_type) {
 		case USRQUOTA:
-			return current->fsuid == dquot->dq_id;
+			return current_fsuid() == dquot->dq_id;
 		case GRPQUOTA:
 			return in_group_p(dquot->dq_id);
 	}
@@ -981,7 +981,7 @@
 		MINOR(dquot->dq_sb->s_dev));
 	if (ret)
 		goto attr_err_out;
-	ret = nla_put_u64(skb, QUOTA_NL_A_CAUSED_ID, current->user->uid);
+	ret = nla_put_u64(skb, QUOTA_NL_A_CAUSED_ID, current_uid());
 	if (ret)
 		goto attr_err_out;
 	genlmsg_end(skb, msg_head);