cifs: Allow using O_DIRECT with cache=loose

Currently O_DIRECT is supported with cache=none and cache=strict, but
not cache=loose. Add support for using O_DIRECT when mounted with
cache=loose.
Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/cifsfs.c

@@ -754,6 +754,9 @@ cifs_loose_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 	ssize_t rc;
 	struct inode *inode = file_inode(iocb->ki_filp);
 
+	if (iocb->ki_filp->f_flags & O_DIRECT)
+		return cifs_user_readv(iocb, iter);
+
 	rc = cifs_revalidate_mapping(inode);
 	if (rc)
 		return rc;
@@ -768,6 +771,18 @@ static ssize_t cifs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	ssize_t written;
 	int rc;
 
+	if (iocb->ki_filp->f_flags & O_DIRECT) {
+		written = cifs_user_writev(iocb, from);
+		if (written > 0 && CIFS_CACHE_READ(cinode)) {
+			cifs_zap_mapping(inode);
+			cifs_dbg(FYI,
+				 "Set no oplock for inode=%p after a write operation\n",
+				 inode);
+			cinode->oplock = 0;
+		}
+		return written;
+	}
+
 	written = cifs_get_writer(cinode);
 	if (written)
 		return written;