CIFS: Check for reconnects before sending async requests

The reconnect might have happended after we obtained credits
and before we acquired srv_mutex. Check for that under the mutex
and retry an async operation if the reconnect is detected.
Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/cifsproto.h

@@ -93,7 +93,8 @@ extern int cifs_discard_remaining_data(struct TCP_Server_Info *server);
 extern int cifs_call_async(struct TCP_Server_Info *server,
 			struct smb_rqst *rqst,
 			mid_receive_t *receive, mid_callback_t *callback,
-			mid_handle_t *handle, void *cbdata, const int flags);
+			mid_handle_t *handle, void *cbdata, const int flags,
+			const struct cifs_credits *exist_credits);
 extern int cifs_send_recv(const unsigned int xid, struct cifs_ses *ses,
 			  struct smb_rqst *rqst, int *resp_buf_type,
 			  const int flags, struct kvec *resp_iov);

fs/cifs/cifssmb.c

@@ -860,7 +860,7 @@ CIFSSMBEcho(struct TCP_Server_Info *server)
 	iov[1].iov_base = (char *)smb + 4;
 
 	rc = cifs_call_async(server, &rqst, NULL, cifs_echo_callback, NULL,
-			     server, CIFS_ASYNC_OP | CIFS_ECHO_OP);
+			     server, CIFS_ASYNC_OP | CIFS_ECHO_OP, NULL);
 	if (rc)
 		cifs_dbg(FYI, "Echo request failed: %d\n", rc);
 
@@ -1812,7 +1812,7 @@ cifs_async_readv(struct cifs_readdata *rdata)
 
 	kref_get(&rdata->refcount);
 	rc = cifs_call_async(tcon->ses->server, &rqst, cifs_readv_receive,
-			     cifs_readv_callback, NULL, rdata, 0);
+			     cifs_readv_callback, NULL, rdata, 0, NULL);
 
 	if (rc == 0)
 		cifs_stats_inc(&tcon->stats.cifs_stats.num_reads);
@@ -2352,7 +2352,7 @@ cifs_async_writev(struct cifs_writedata *wdata,
 
 	kref_get(&wdata->refcount);
 	rc = cifs_call_async(tcon->ses->server, &rqst, NULL,
-				cifs_writev_callback, NULL, wdata, 0);
+			     cifs_writev_callback, NULL, wdata, 0, NULL);
 
 	if (rc == 0)
 		cifs_stats_inc(&tcon->stats.cifs_stats.num_writes);

fs/cifs/smb2pdu.c

@@ -3034,7 +3034,7 @@ SMB2_echo(struct TCP_Server_Info *server)
 	iov[0].iov_base = (char *)req;
 
 	rc = cifs_call_async(server, &rqst, NULL, smb2_echo_callback, NULL,
-			     server, CIFS_ECHO_OP);
+			     server, CIFS_ECHO_OP, NULL);
 	if (rc)
 		cifs_dbg(FYI, "Echo request failed: %d\n", rc);
 
@@ -3343,7 +3343,8 @@ smb2_async_readv(struct cifs_readdata *rdata)
 	kref_get(&rdata->refcount);
 	rc = cifs_call_async(io_parms.tcon->ses->server, &rqst,
 			     cifs_readv_receive, smb2_readv_callback,
-			     smb3_handle_read_data, rdata, flags);
+			     smb3_handle_read_data, rdata, flags,
+			     &rdata->credits);
 	if (rc) {
 		kref_put(&rdata->refcount, cifs_readdata_release);
 		cifs_stats_fail_inc(io_parms.tcon, SMB2_READ_HE);
@@ -3645,7 +3646,7 @@ smb2_async_writev(struct cifs_writedata *wdata,
 
 	kref_get(&wdata->refcount);
 	rc = cifs_call_async(server, &rqst, NULL, smb2_writev_callback, NULL,
-			     wdata, flags);
+			     wdata, flags, &wdata->credits);
 
 	if (rc) {
 		trace_smb3_write_err(0 /* no xid */, req->PersistentFileId,

fs/cifs/transport.c

@@ -607,7 +607,8 @@ cifs_setup_async_request(struct TCP_Server_Info *server, struct smb_rqst *rqst)
 int
 cifs_call_async(struct TCP_Server_Info *server, struct smb_rqst *rqst,
 		mid_receive_t *receive, mid_callback_t *callback,
-		mid_handle_t *handle, void *cbdata, const int flags)
+		mid_handle_t *handle, void *cbdata, const int flags,
+		const struct cifs_credits *exist_credits)
 {
 	int rc, timeout, optype;
 	struct mid_q_entry *mid;
@@ -623,9 +624,22 @@ cifs_call_async(struct TCP_Server_Info *server, struct smb_rqst *rqst,
 			return rc;
 		credits.value = 1;
 		credits.instance = instance;
-	}
+	} else
+		instance = exist_credits->instance;
 
 	mutex_lock(&server->srv_mutex);
+
+	/*
+	 * We can't use credits obtained from the previous session to send this
+	 * request. Check if there were reconnects after we obtained credits and
+	 * return -EAGAIN in such cases to let callers handle it.
+	 */
+	if (instance != server->reconnect_instance) {
+		mutex_unlock(&server->srv_mutex);
+		add_credits_and_wake_if(server, &credits, optype);
+		return -EAGAIN;
+	}
+
 	mid = server->ops->setup_async_request(server, rqst);
 	if (IS_ERR(mid)) {
 		mutex_unlock(&server->srv_mutex);