CRED: Wrap task credential accesses in the UFS 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: Evgeniy Dushistov <dushistov@mail.ru>
Signed-off-by: James Morris <jmorris@namei.org>

fs/ufs/ialloc.c

@@ -304,13 +304,13 @@ cg_found:
 
 	inode->i_ino = cg * uspi->s_ipg + bit;
 	inode->i_mode = mode;
-	inode->i_uid = current->fsuid;
+	inode->i_uid = current_fsuid();
 	if (dir->i_mode & S_ISGID) {
 		inode->i_gid = dir->i_gid;
 		if (S_ISDIR(mode))
 			inode->i_mode |= S_ISGID;
 	} else
-		inode->i_gid = current->fsgid;
+		inode->i_gid = current_fsgid();
 
 	inode->i_blocks = 0;
 	inode->i_generation = 0;