cifs: prevent data race in cifs_reconnect_tcon()

Make sure to get an up-to-date TCP_Server_Info::nr_targets value prior
to waiting the server to be reconnected in cifs_reconnect_tcon().  It
is set in cifs_tcp_ses_needs_reconnect() and protected by
TCP_Server_Info::srv_lock.

Create a new cifs_wait_for_server_reconnect() helper that can be used
by both SMB2+ and CIFS reconnect code.

Signed-off-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 44 insertions, 0 deletions

diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
index 0c6c1fc8dae9..a0d286ee723d 100644
--- a/fs/cifs/misc.c
+++ b/fs/cifs/misc.c
@@ -1266,3 +1266,47 @@ int cifs_inval_name_dfs_link_error(const unsigned int xid,
 	return 0;
 }
 #endif
+
+int cifs_wait_for_server_reconnect(struct TCP_Server_Info *server, bool retry)
+{
+	int timeout = 10;
+	int rc;
+
+	spin_lock(&server->srv_lock);
+	if (server->tcpStatus != CifsNeedReconnect) {
+		spin_unlock(&server->srv_lock);
+		return 0;
+	}
+	timeout *= server->nr_targets;
+	spin_unlock(&server->srv_lock);
+
+	/*
+	 * Give demultiplex thread up to 10 seconds to each target available for
+	 * reconnect -- should be greater than cifs socket timeout which is 7
+	 * seconds.
+	 *
+	 * On "soft" mounts we wait once. Hard mounts keep retrying until
+	 * process is killed or server comes back on-line.
+	 */
+	do {
+		rc = wait_event_interruptible_timeout(server->response_q,
+						      (server->tcpStatus != CifsNeedReconnect),
+						      timeout * HZ);
+		if (rc < 0) {
+			cifs_dbg(FYI, "%s: aborting reconnect due to received signal\n",
+				 __func__);
+			return -ERESTARTSYS;
+		}
+
+		/* are we still trying to reconnect? */
+		spin_lock(&server->srv_lock);
+		if (server->tcpStatus != CifsNeedReconnect) {
+			spin_unlock(&server->srv_lock);
+			return 0;
+		}
+		spin_unlock(&server->srv_lock);
+	} while (retry);
+
+	cifs_dbg(FYI, "%s: gave up waiting on reconnect\n", __func__);
+	return -EHOSTDOWN;
+}