fix block device fallout from ->fsync() changes

blkdev_fsync() needs to write pages in pagecache...
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/block_dev.c

@@ -387,6 +387,10 @@ int blkdev_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
 	struct inode *bd_inode = filp->f_mapping->host;
 	struct block_device *bdev = I_BDEV(bd_inode);
 	int error;
+	
+	error = filemap_write_and_wait_range(filp->f_mapping, start, end);
+	if (error)
+		return error;
 
 	/*
 	 * There is no need to serialise calls to blkdev_issue_flush with