NFSv4.2: Serialise O_DIRECT i/o and copy range

Ensure that all O_DIRECT reads and writes complete before copying a file
range, so that the destination is up to date.

Fixes: a5864c999d ("NFS: Do not serialise O_DIRECT reads and writes")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/nfs42proc.c

@@ -445,6 +445,7 @@ static ssize_t _nfs42_proc_copy(struct file *src,
 		return status;
 	}
 
+	nfs_file_block_o_direct(NFS_I(dst_inode));
 	status = nfs_sync_inode(dst_inode);
 	if (status)
 		return status;