CIFS: Delete echo_retries module parm

It's the essential step before respecting MaxMpxCount value during
negotiating because we will keep only one extra slot for sending
echo requests. If there is no response during two echo intervals -
reconnect the tcp session.
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/README

@@ -753,10 +753,6 @@ module loading or during the runtime by using the interface
 
 i.e. echo "value" > /sys/module/cifs/parameters/<param>
 
-1. echo_retries - The number of echo attempts before giving up and
-		  reconnecting to the server. The default is 5. The value 0
-		  means never reconnect.
-
-2. enable_oplocks - Enable or disable oplocks. Oplocks are enabled by default.
+1. enable_oplocks - Enable or disable oplocks. Oplocks are enabled by default.
 		    [Y/y/1]. To disable use any of [N/n/0].
 

fs/cifs/cifsfs.c

@@ -77,11 +77,6 @@ unsigned int cifs_max_pending = CIFS_MAX_REQ;
 module_param(cifs_max_pending, int, 0444);
 MODULE_PARM_DESC(cifs_max_pending, "Simultaneous requests to server. "
 				   "Default: 32767 Range: 2 to 32767.");
-unsigned short echo_retries = 5;
-module_param(echo_retries, ushort, 0644);
-MODULE_PARM_DESC(echo_retries, "Number of echo attempts before giving up and "
-			       "reconnecting server. Default: 5. 0 means "
-			       "never reconnect.");
 module_param(enable_oplocks, bool, 0644);
 MODULE_PARM_DESC(enable_oplocks, "Enable or disable oplocks (bool). Default:"
 				 "y/Y/1");

fs/cifs/cifsglob.h

@@ -1038,9 +1038,6 @@ GLOBAL_EXTERN unsigned int cifs_min_rcv;    /* min size of big ntwrk buf pool */
 GLOBAL_EXTERN unsigned int cifs_min_small;  /* min size of small buf pool */
 GLOBAL_EXTERN unsigned int cifs_max_pending; /* MAX requests at once to server*/
 
-/* reconnect after this many failed echo attempts */
-GLOBAL_EXTERN unsigned short echo_retries;
-
 #ifdef CONFIG_CIFS_ACL
 GLOBAL_EXTERN struct rb_root uidtree;
 GLOBAL_EXTERN struct rb_root gidtree;

fs/cifs/connect.c

@@ -373,12 +373,22 @@ allocate_buffers(struct TCP_Server_Info *server)
 static bool
 server_unresponsive(struct TCP_Server_Info *server)
 {
-	if (echo_retries > 0 && server->tcpStatus == CifsGood &&
-	    time_after(jiffies, server->lstrp +
-				(echo_retries * SMB_ECHO_INTERVAL))) {
+	/*
+	 * We need to wait 2 echo intervals to make sure we handle such
+	 * situations right:
+	 * 1s  client sends a normal SMB request
+	 * 2s  client gets a response
+	 * 30s echo workqueue job pops, and decides we got a response recently
+	 *     and don't need to send another
+	 * ...
+	 * 65s kernel_recvmsg times out, and we see that we haven't gotten
+	 *     a response in >60s.
+	 */
+	if (server->tcpStatus == CifsGood &&
+	    time_after(jiffies, server->lstrp + 2 * SMB_ECHO_INTERVAL)) {
 		cERROR(1, "Server %s has not responded in %d seconds. "
 			  "Reconnecting...", server->hostname,
-			  (echo_retries * SMB_ECHO_INTERVAL / HZ));
+			  (2 * SMB_ECHO_INTERVAL) / HZ);
 		cifs_reconnect(server);
 		wake_up(&server->response_q);
 		return true;