CIFS: Fix an issue with re-sending rdata when transport returning -EAGAIN

When sending a rdata, transport may return -EAGAIN. In this case
we should re-obtain credits because the session may have been
reconnected.

Change in v2: adjust_credits before re-sending
Signed-off-by: Long Li <longli@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>

fs/cifs/file.c

@@ -3361,44 +3361,55 @@ static int cifs_resend_rdata(struct cifs_readdata *rdata,
 	struct TCP_Server_Info *server =
 		tlink_tcon(rdata->cfile->tlink)->ses->server;
 
+	do {
+		if (rdata->cfile->invalidHandle) {
+			rc = cifs_reopen_file(rdata->cfile, true);
+			if (rc == -EAGAIN)
+				continue;
+			else if (rc)
+				break;
+		}
+
 		/*
 		 * Wait for credits to resend this rdata.
-	 * Note: we are attempting to resend the whole rdata not in segments
+		 * Note: we are attempting to resend the whole rdata not in
+		 * segments
 		 */
 		do {
 			rc = server->ops->wait_mtu_credits(server, rdata->bytes,
 						&rsize, &credits);
 
 			if (rc)
-			goto out;
+				goto fail;
 
 			if (rsize < rdata->bytes) {
 				add_credits_and_wake_if(server, &credits, 0);
 				msleep(1000);
 			}
 		} while (rsize < rdata->bytes);
-
 		rdata->credits = credits;
-	rc = -EAGAIN;
-	while (rc == -EAGAIN) {
-		rc = 0;
+
+		rc = adjust_credits(server, &rdata->credits, rdata->bytes);
+		if (!rc) {
 			if (rdata->cfile->invalidHandle)
-			rc = cifs_reopen_file(rdata->cfile, true);
-		if (!rc)
+				rc = -EAGAIN;
+			else
 				rc = server->ops->async_readv(rdata);
 		}
 
+		/* If the read was successfully sent, we are done */
 		if (!rc) {
 			/* Add to aio pending list */
 			list_add_tail(&rdata->list, rdata_list);
 			return 0;
 		}
 
+		/* Roll back credits and retry if needed */
 		add_credits_and_wake_if(server, &rdata->credits, 0);
-out:
-	kref_put(&rdata->refcount,
-		cifs_uncached_readdata_release);
+	} while (rc == -EAGAIN);
 
+fail:
+	kref_put(&rdata->refcount, cifs_uncached_readdata_release);
 	return rc;
 }