cr: Preparations for snapshot

1. Directory with images may have a "parent" symlink pointing to the
   place where the previous snapshot is
2. Each pagemap will have "in_parent" bit, which means, that the
   pages for this pagemap entry are not in the respective page.img
   but in parent
3. New --leave-running option to use with --snapshot not to kill
   tasks after snapshot

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

crtools.c

@@ -68,7 +68,7 @@ int main(int argc, char *argv[])
 	int log_inited = 0;
 	int log_level = 0;
 
-	static const char short_opts[] = "dsf:t:p:hcD:o:n:vxVr:jl";
+	static const char short_opts[] = "dsRf:t:p:hcD:o:n:vxVr:jl";
 
 	BUILD_BUG_ON(PAGE_SIZE != PAGE_IMAGE_SIZE);
 
@@ -90,6 +90,7 @@ int main(int argc, char *argv[])
 			{ "tree", required_argument, 0, 't' },
 			{ "pid", required_argument, 0, 'p' },
 			{ "leave-stopped", no_argument, 0, 's' },
+			{ "leave-running", no_argument, 0, 'R' },
 			{ "restore-detached", no_argument, 0, 'd' },
 			{ "contents", no_argument, 0, 'c' },
 			{ "file", required_argument, 0, 'f' },
@@ -113,6 +114,7 @@ int main(int argc, char *argv[])
 			{ "page-server", no_argument, 0, 50},
 			{ "address", required_argument, 0, 51},
 			{ "port", required_argument, 0, 52},
+			{ "snapshot", optional_argument, 0, 53},
 			{ },
 		};
 
@@ -124,6 +126,9 @@ int main(int argc, char *argv[])
 		case 's':
 			opts.final_state = TASK_STOPPED;
 			break;
+		case 'R':
+			opts.final_state = TASK_ALIVE;
+			break;
 		case 'x':
 			opts.ext_unix_sk = true;
 			break;
@@ -256,6 +261,10 @@ int main(int argc, char *argv[])
 		case 'l':
 			opts.handle_file_locks = true;
 			break;
+		case 53:
+			opts.mem_snapshot = true;
+			opts.snap_parent = optarg;
+			break;
 		case 'V':
 			pr_msg("Version: %s\n", version);
 			return 0;
@@ -275,6 +284,9 @@ int main(int argc, char *argv[])
 			return ret;
 	}
 
+	if (opts.mem_snapshot)
+		pr_info("Will do snapshot from %s\n", opts.snap_parent);
+
 	ret = open_image_dir();
 	if (ret < 0) {
 		pr_perror("can't open currect directory");
@@ -355,8 +367,10 @@ usage:
 	pr_msg("  -t|--tree             checkpoint/restore the whole process tree identified by pid\n");
 	pr_msg("  -d|--restore-detached detach after restore\n");
 	pr_msg("  -s|--leave-stopped    leave tasks in stopped state after checkpoint instead of killing them\n");
+	pr_msg("  -R|--leave-running    leave tasks in running state after checkpoint\n");
 	pr_msg("  -D|--images-dir       directory where to put images to\n");
 	pr_msg("     --pidfile [FILE]	write a pid of a root task in this file\n");
+	pr_msg("     --snapshot <[DIR]> create snapshot (relative to DIR images if given)\n");
 
 	pr_msg("\n* Special resources support:\n");
 	pr_msg("  -x|--%s      allow external unix connections\n", USK_EXT_PARAM);

image.c

@@ -325,7 +325,29 @@ int open_image_dir(void)
 
 	close(fd);
 
+	if (opts.snap_parent) {
+		ret = symlink(opts.snap_parent, CR_PARENT_LINK);
+		if (ret < 0) {
+			pr_perror("Can't link parent snapshot.");
+			goto err;
+		}
+
+		fd = open(CR_PARENT_LINK, O_RDONLY);
+		if (fd < 0) {
+			pr_perror("Can't open parent snapshot.");
+			goto err;
+		}
+
+		ret = install_service_fd(PARENT_FD_OFF, fd);
+
+		close(fd);
+	}
+
 	return ret;
+
+err:
+	close_image_dir();
+	return -1;
 }
 
 void close_image_dir(void)

include/crtools.h

@@ -117,6 +117,8 @@ struct cr_options {
 	struct list_head	scripts;
 	bool			use_page_server;
 	struct sockaddr_in	ps_addr;
+	bool			mem_snapshot;
+	char			*snap_parent;
 };
 
 extern struct cr_options opts;
@@ -131,10 +133,13 @@ enum sfd_type {
 	PROC_FD_OFF,
 	CTL_TTY_OFF,
 	SELF_STDIN_OFF,
+	PARENT_FD_OFF,
 
 	SERVICE_FD_MAX
 };
 
+#define CR_PARENT_LINK	"parent"
+
 extern int clone_service_fd(int id);
 extern int init_service_fd(void);
 extern int get_service_fd(enum sfd_type type);

protobuf/pagemap.proto

@@ -5,4 +5,5 @@ message pagemap_head {
 message pagemap_entry {
 	required uint64 vaddr = 1;
 	required uint32 nr_pages = 2;
+	optional bool	in_parent = 3;
 }