diff -druN Linux-2.4.19-pre3/fs/fcntl.c linux-2.4.19-pre3/fs/fcntl.c
--- Linux-2.4.19-pre3/fs/fcntl.c	Wed Mar 13 12:30:42 2002
+++ linux-2.4.19-pre3/fs/fcntl.c	Thu Mar 21 10:33:10 2002
@@ -219,6 +219,11 @@
 	}
 
 	if (arg & O_DIRECT) {
+		if (inode->i_mapping && inode->i_mapping->a_ops) {
+			if (!inode->i_mapping->a_ops->direct_IO)
+				return -EINVAL;
+		}
+
 		/*
 		 * alloc_kiovec() can sleep and we are only serialized by
 		 * the big kernel lock here, so abuse the i_sem to serialize
diff -druN Linux-2.4.19-pre3/fs/open.c linux-2.4.19-pre3/fs/open.c
--- Linux-2.4.19-pre3/fs/open.c	Wed Mar 13 12:31:10 2002
+++ linux-2.4.19-pre3/fs/open.c	Thu Mar 21 10:31:32 2002
@@ -691,6 +691,14 @@
 	}
 	f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
 
+	/* NB: we're sure to have correct a_ops only after f_op->open */
+	if (f->f_flags & O_DIRECT) {
+		error = -EINVAL;
+		if (inode->i_mapping && inode->i_mapping->a_ops)
+			if (!inode->i_mapping->a_ops->direct_IO)
+				goto cleanup_all;
+	}
+
 	return f;
 
 cleanup_all:
diff -druN Linux-2.4.19-pre3/mm/filemap.c linux-2.4.19-pre3/mm/filemap.c
--- Linux-2.4.19-pre3/mm/filemap.c	Wed Mar 13 12:32:01 2002
+++ linux-2.4.19-pre3/mm/filemap.c	Thu Mar 21 10:13:09 2002
@@ -1562,8 +1562,6 @@
 	retval = -EINVAL;
 	if ((offset & blocksize_mask) || (count & blocksize_mask))
 		goto out_free;
-	if (!mapping->a_ops->direct_IO)
-		goto out_free;
 
 	/*
 	 * Flush to disk exclusively the _data_, metadata must remain