smb3: add missing worker function for SMB3 change notify

SMB3 change notify is important to allow applications to wait
on directory change events of different types (e.g. adding
and deleting files from others systems). Add worker functions
for this.
Acked-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/smb2pdu.c

@@ -3175,6 +3175,91 @@ SMB2_get_srv_num(const unsigned int xid, struct cifs_tcon *tcon,
 			  (void **)&uniqueid, NULL);
 }
 
+/*
+ * CHANGE_NOTIFY Request is sent to get notifications on changes to a directory
+ * See MS-SMB2 2.2.35 and 2.2.36
+ */
+
+int
+SMB2_notify_init(const unsigned int xid, struct smb_rqst *rqst,
+		struct cifs_tcon *tcon, u64 persistent_fid, u64 volatile_fid,
+		u32 completion_filter, bool watch_tree)
+{
+	struct smb2_change_notify_req *req;
+	struct kvec *iov = rqst->rq_iov;
+	unsigned int total_len;
+	int rc;
+
+	rc = smb2_plain_req_init(SMB2_CHANGE_NOTIFY, tcon, (void **) &req, &total_len);
+	if (rc)
+		return rc;
+
+	req->PersistentFileId = persistent_fid;
+	req->VolatileFileId = volatile_fid;
+	req->OutputBufferLength = SMB2_MAX_BUFFER_SIZE - MAX_SMB2_HDR_SIZE;
+	req->CompletionFilter = cpu_to_le32(completion_filter);
+	if (watch_tree)
+		req->Flags = cpu_to_le16(SMB2_WATCH_TREE);
+	else
+		req->Flags = 0;
+
+	iov[0].iov_base = (char *)req;
+	iov[0].iov_len = total_len;
+
+	return 0;
+}
+
+int
+SMB2_change_notify(const unsigned int xid, struct cifs_tcon *tcon,
+		u64 persistent_fid, u64 volatile_fid, bool watch_tree,
+		u32 completion_filter)
+{
+	struct cifs_ses *ses = tcon->ses;
+	struct smb_rqst rqst;
+	struct kvec iov[1];
+	struct kvec rsp_iov = {NULL, 0};
+	int resp_buftype = CIFS_NO_BUFFER;
+	int flags = 0;
+	int rc = 0;
+
+	cifs_dbg(FYI, "change notify\n");
+	if (!ses || !(ses->server))
+		return -EIO;
+
+	if (smb3_encryption_required(tcon))
+		flags |= CIFS_TRANSFORM_REQ;
+
+	memset(&rqst, 0, sizeof(struct smb_rqst));
+	memset(&iov, 0, sizeof(iov));
+	rqst.rq_iov = iov;
+	rqst.rq_nvec = 1;
+
+	rc = SMB2_notify_init(xid, &rqst, tcon, persistent_fid, volatile_fid,
+			      completion_filter, watch_tree);
+	if (rc)
+		goto cnotify_exit;
+
+	trace_smb3_notify_enter(xid, persistent_fid, tcon->tid, ses->Suid,
+				(u8)watch_tree, completion_filter);
+	rc = cifs_send_recv(xid, ses, &rqst, &resp_buftype, flags, &rsp_iov);
+
+	if (rc != 0) {
+		cifs_stats_fail_inc(tcon, SMB2_CHANGE_NOTIFY_HE);
+		trace_smb3_notify_err(xid, persistent_fid, tcon->tid, ses->Suid,
+				(u8)watch_tree, completion_filter, rc);
+	} else
+		trace_smb3_notify_done(xid, persistent_fid, tcon->tid,
+				ses->Suid, (u8)watch_tree, completion_filter);
+
+ cnotify_exit:
+	if (rqst.rq_iov)
+		cifs_small_buf_release(rqst.rq_iov[0].iov_base); /* request */
+	free_rsp_buf(resp_buftype, rsp_iov.iov_base);
+	return rc;
+}
+
+
+
 /*
  * This is a no-op for now. We're not really interested in the reply, but
  * rather in the fact that the server sent one and that server->lstrp

fs/cifs/trace.h

@@ -235,6 +235,8 @@ DEFINE_EVENT(smb3_inf_enter_class, smb3_##name,    \
 
 DEFINE_SMB3_INF_ENTER_EVENT(query_info_enter);
 DEFINE_SMB3_INF_ENTER_EVENT(query_info_done);
+DEFINE_SMB3_INF_ENTER_EVENT(notify_enter);
+DEFINE_SMB3_INF_ENTER_EVENT(notify_done);
 
 DECLARE_EVENT_CLASS(smb3_inf_err_class,
 	TP_PROTO(unsigned int xid,
@@ -281,6 +283,7 @@ DEFINE_EVENT(smb3_inf_err_class, smb3_##name,    \
 
 DEFINE_SMB3_INF_ERR_EVENT(query_info_err);
 DEFINE_SMB3_INF_ERR_EVENT(set_info_err);
+DEFINE_SMB3_INF_ERR_EVENT(notify_err);
 DEFINE_SMB3_INF_ERR_EVENT(fsctl_err);
 
 DECLARE_EVENT_CLASS(smb3_inf_compound_enter_class,