[Nbd] [PATCH] UNTESTED: Add support for NBD_CMD_CLOSE to nbd-server

[Alex Bligh <alex@...872...>]

Add support for NBD_CMD_CLOSE. NBD_CMD_CLOSE waits for all inflight
commands to complete, then does a FLUSH & reply (reporting any error,
which is optional in the spec), then closes the channel (which
is optional in the spec and an easy way to avoid processing further
commands).

Signed-off-by: Alex Bligh <alex@...872...>
---
 nbd-server.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++------
 nbd.h        |  4 +++-
 2 files changed, 49 insertions(+), 7 deletions(-)

This is completely untested my end apart from noting it compiles.
I have no server that sends NBD_CMD_CLOSE to test it against, but
Eric is working on that, and I thought he might like a reference
implementation.

diff --git a/nbd-server.c b/nbd-server.c
index 4edb883..1b558d7 100644
--- a/nbd-server.c
+++ b/nbd-server.c
@@ -261,6 +261,8 @@ static inline const char * getcommandname(uint64_t command) {
 		return "NBD_CMD_FLUSH";
 	case NBD_CMD_TRIM:
 		return "NBD_CMD_TRIM";
+	case NBD_CMD_CLOSE:
+		return "NBD_CMD_CLOSE";
 	default:
 		return "UNKNOWN";
 	}
@@ -1396,6 +1398,7 @@ void send_export_info(CLIENT* client) {
 		flags |= NBD_FLAG_ROTATIONAL;
 	if (client->server->flags & F_TRIM)
 		flags |= NBD_FLAG_SEND_TRIM;
+	flags |= NBD_FLAG_SEND_CLOSE;
 	flags = htons(flags);
 	if (write(client->net, &flags, sizeof(flags)) < 0)
 		err("Negotiation failed/11: %m");
@@ -1517,6 +1520,19 @@ static void handle_trim(CLIENT* client, struct nbd_request* req) {
 	pthread_mutex_unlock(&(client->lock));
 }
 
+static void handle_close(CLIENT* client, struct nbd_request* req) {
+	struct nbd_reply rep;
+	DEBUG("handling close request\n");
+	setup_reply(&rep, req);
+	if(expflush(client)) {
+		DEBUG("Flush on close failed: %m");
+		rep.error = nbd_errno(errno);
+	}
+	pthread_mutex_lock(&(client->lock));
+	writeit(client->net, &rep, sizeof rep);
+	pthread_mutex_unlock(&(client->lock));
+}
+
 static void handle_request(gpointer data, gpointer user_data) {
 	struct work_package* package = (struct work_package*) data;
 	uint32_t type = package->req->type & NBD_CMD_MASK_COMMAND;
@@ -1541,6 +1557,9 @@ static void handle_request(gpointer data, gpointer user_data) {
 		case NBD_CMD_TRIM:
 			handle_trim(package->client, package->req);
 			break;
+		case NBD_CMD_CLOSE:
+			handle_close(package->client, package->req);
+			break;
 		default:
 			msg(LOG_ERR, "E: received unknown command %d of type, ignoring", package->req->type);
 			goto error;
@@ -1586,6 +1605,14 @@ static int mainloop_threaded(CLIENT* client) {
 			g_thread_pool_free(tpool, FALSE, TRUE);
 			return 0;
 		}
+		if(req->type == NBD_CMD_CLOSE) {
+			// we call with immediate FALSE which ensures all current
+			// threads end their work, then manually handle the close
+			// request
+			g_thread_pool_free(tpool, FALSE, TRUE);
+			handle_request(pkg, NULL);
+			return 0;
+		}
 		g_thread_pool_push(tpool, pkg, NULL);
 	}
 }
@@ -1673,12 +1700,6 @@ int mainloop(CLIENT *client) {
 
 		case NBD_CMD_DISC:
 			msg(LOG_INFO, "Disconnect request received.");
-                	if (client->server->flags & F_COPYONWRITE) { 
-				if (client->difmap) g_free(client->difmap) ;
-                		close(client->difffile);
-				unlink(client->difffilename);
-				free(client->difffilename);
-			}
 			go_on=FALSE;
 			continue;
 
@@ -1762,11 +1783,30 @@ int mainloop(CLIENT *client) {
 			SEND(client->net, reply);
 			continue;
 
+		case NBD_CMD_CLOSE:
+			DEBUG("cl: ");
+			if (expflush(client)) {
+				DEBUG("Flush on close failed: %m");
+				ERROR(client, reply, errno);
+			} else {
+				SEND(client->net, reply);
+				DEBUG("OK!\n");
+			}
+			msg(LOG_INFO, "Close request received.");
+			go_on=FALSE;
+			continue;
+
 		default:
 			DEBUG ("Ignoring unknown command\n");
 			continue;
 		}
 	}
+	if (client->server->flags & F_COPYONWRITE) {
+		if (client->difmap) g_free(client->difmap) ;
+		close(client->difffile);
+		unlink(client->difffilename);
+		free(client->difffilename);
+	}
 	return 0;
 }
 
diff --git a/nbd.h b/nbd.h
index 732c605..1841746 100644
--- a/nbd.h
+++ b/nbd.h
@@ -34,7 +34,8 @@ enum {
 	NBD_CMD_WRITE = 1,
 	NBD_CMD_DISC = 2,
 	NBD_CMD_FLUSH = 3,
-	NBD_CMD_TRIM = 4
+	NBD_CMD_TRIM = 4,
+	NBD_CMD_CLOSE = 7
 };
 
 #define NBD_CMD_MASK_COMMAND 0x0000ffff
@@ -48,6 +49,7 @@ enum {
 #define NBD_FLAG_SEND_FUA	(1 << 3)	/* Send FUA (Force Unit Access) */
 #define NBD_FLAG_ROTATIONAL	(1 << 4)	/* Use elevator algorithm - rotational media */
 #define NBD_FLAG_SEND_TRIM	(1 << 5)	/* Send TRIM (discard) */
+#define NBD_FLAG_SEND_CLOSE	(1 << 8)	/* Send CLOSE */
 
 #define nbd_cmd(req) ((req)->cmd[0])
 
-- 
1.9.1