page-server: allow to execute page-server in the background (v2)

page-server creates a listen socket and only then goes into the
background, so we can be sure, that page-server is ready for work after
detaching.

v2: call daemon() in a proper place and reuse the option -d
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

crtools.c

@@ -346,7 +346,7 @@ int main(int argc, char *argv[])
 	}
 
 	if (!strcmp(argv[optind], "page-server"))
-		return  cr_page_server();
+		return cr_page_server(opts.restore_detach);
 
 	pr_msg("Unknown command \"%s\"\n", argv[optind]);
 usage:
@@ -415,6 +415,7 @@ usage:
 "Page server options\n"
 "  --address ADDR        address of page server\n"
 "  --port PORT           port of page server\n"
+"  -d                    run in the background after creating socket\n"
 "\n"
 "Show options:\n"
 "  -f|--file FILE        show contents of a checkpoint file\n"

include/page-xfer.h

 #ifndef __CR_PAGE_XFER__H__
 #define __CR_PAGE_XFER__H__
-int cr_page_server(void);
+int cr_page_server(bool daemon_mode);
 
 /*
  * page_xfer -- transfer pages into image file.

page-xfer.c

@@ -195,7 +195,7 @@ static int page_server_serve(int sk)
 	return ret;
 }
 
-int cr_page_server(void)
+int cr_page_server(bool daemon_mode)
 {
 	int sk, ask = -1;
 	struct sockaddr_in caddr;
@@ -223,6 +223,9 @@ int cr_page_server(void)
 		goto out;
 	}
 
+	if (daemon_mode)
+		daemon(0, 0);
+
 	ask = accept(sk, (struct sockaddr *)&caddr, &clen);
 	if (ask < 0)
 		pr_perror("Can't accept connection to server");

test/zdtm.sh

@@ -350,7 +350,7 @@ EOF
 	mkdir -p $ddump
 
 	if [ $PAGE_SERVER -eq 1 ]; then
-		$CRTOOLS page-server -D $ddump -o page_server.log -v 4 --port $PS_PORT &
+		$CRTOOLS page-server -D $ddump -o page_server.log -v 4 --port $PS_PORT -d
 		PS_PID=$!
 		opts="--page-server --address 127.0.0.1 --port $PS_PORT"
 	fi