New helper - current_umask()

current->fs->umask is what most of fs_struct users are doing.
Put that into a helper function.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index bca729f..7594bec 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -267,7 +267,7 @@
 		goto out_dput;
 
 	if (!IS_POSIXACL(parent->dentry->d_inode))
-		mode &= ~current->fs->umask;
+		mode &= ~current_umask();
 
 	error = mnt_want_write(parent->mnt);
 	if (error)