[PATCH] O_DIRECT open check

Updated forward-port of Aodrea's O_DIRECT open() checks.  If the user
asked for O_DIRECT and the inode has no mapping or no a_ops then fail
the open up-front.

fs/fcntl.c

@@ -245,10 +245,9 @@ static int setfl(int fd, struct file * filp, unsigned long arg)
 	}
 
 	if (arg & O_DIRECT) {
-		if (inode->i_mapping && inode->i_mapping->a_ops) {
-			if (!inode->i_mapping->a_ops->direct_IO)
+		if (!inode->i_mapping || !inode->i_mapping->a_ops ||
+			!inode->i_mapping->a_ops->direct_IO)
 				return -EINVAL;
-		}
 
 		/*
 		 * alloc_kiovec() can sleep and we are only serialized by

fs/open.c

@@ -665,10 +665,11 @@ struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags)
 
 	/* 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)
+		if (!inode->i_mapping || !inode->i_mapping->a_ops ||
+			!inode->i_mapping->a_ops->direct_IO) {
+				error = -EINVAL;
 				goto cleanup_all;
+		}
 	}
 
 	return f;