From: Henning Schild henning.schild@siemens.com

commit f2caf901c1b7ce65f9e6aef4217e3241039db768 upstream

There is a race condition with how we send (or supress and don't send) smb echos that will cause the client to incorrectly think the server is unresponsive and thus needs to be reconnected.

Summary of the race condition: 1) Daisy chaining scheduling creates a gap. 2) If traffic comes unfortunate shortly after the last echo, the planned echo is suppressed. 3) Due to the gap, the next echo transmission is delayed until after the timeout, which is set hard to twice the echo interval.

This is fixed by changing the timeouts from 2 to three times the echo interval.

Detailed description of the bug: https://lutz.donnerhacke.de/eng/Blog/Groundhog-Day-with-SMB-remount

Signed-off-by: Ronnie Sahlberg lsahlber@redhat.com Reviewed-by: Pavel Shilovsky pshilov@microsoft.com Signed-off-by: Steve French stfrench@microsoft.com Signed-off-by: Henning Schild henning.schild@siemens.com --- fs/cifs/connect.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c index c018d161735c..f54277049512 100644 --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -551,10 +551,10 @@ static bool server_unresponsive(struct TCP_Server_Info *server) { /* - * We need to wait 2 echo intervals to make sure we handle such + * We need to wait 3 echo intervals to make sure we handle such * situations right: * 1s client sends a normal SMB request - * 2s client gets a response + * 3s client gets a response * 30s echo workqueue job pops, and decides we got a response recently * and don't need to send another * ... @@ -562,9 +562,9 @@ server_unresponsive(struct TCP_Server_Info *server) * a response in >60s. */ if (server->tcpStatus == CifsGood && - time_after(jiffies, server->lstrp + 2 * server->echo_interval)) { + time_after(jiffies, server->lstrp + 3 * server->echo_interval)) { cifs_dbg(VFS, "Server %s has not responded in %lu seconds. Reconnecting...\n", - server->hostname, (2 * server->echo_interval) / HZ); + server->hostname, (3 * server->echo_interval) / HZ); cifs_reconnect(server); wake_up(&server->response_q); return true;