restore: add action scripts setup-namespaces (v2)

After creating namespaces we may need to apply some configuration.
For example uid and gid maps should be applied in this moment.

This script should be executed from crtools, but namespaces are created
in a root process, so we need to add a new stage for synchronizing.

v2: use a separate stage instead of socketpair.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cr-restore.c

@@ -931,6 +931,14 @@ static void sigchld_handler(int signal, siginfo_t *siginfo, void *data)
 
 	exit = (siginfo->si_code == CLD_EXITED);
 	status = siginfo->si_status;
+
+	/* skip scripts */
+	if (!current && root_item->pid.real != pid) {
+		pid = waitpid(root_item->pid.real, &status, WNOHANG);
+		if (pid <= 0)
+			return;
+	}
+
 	if (!current || status)
 		goto err;
 
@@ -1091,6 +1099,8 @@ static int restore_task_with_children(void *_arg)
 		if (mount_proc())
 			exit(1);
 
+		restore_finish_stage(CR_STATE_RESTORE_NS);
+
 		if (root_prepare_shared())
 			exit(1);
 	}
@@ -1158,6 +1168,8 @@ static int restore_task_with_children(void *_arg)
 static inline int stage_participants(int next_stage)
 {
 	switch (next_stage) {
+	case CR_STATE_RESTORE_NS:
+		return 1;
 	case CR_STATE_FORKING:
 		return task_entries->nr_tasks + task_entries->nr_helpers;
 	case CR_STATE_RESTORE_PGID:
@@ -1173,7 +1185,7 @@ static inline int stage_participants(int next_stage)
 	return -1;
 }
 
-static int restore_switch_stage(int next_stage)
+static int restore_wait_inprogress_tasks()
 {
 	int ret;
 	futex_t *np = &task_entries->nr_in_progress;
@@ -1183,7 +1195,19 @@ static int restore_switch_stage(int next_stage)
 	if (ret < 0)
 		return ret;
 
-	futex_set(np, stage_participants(next_stage));
+	return 0;
+}
+
+static int restore_switch_stage(int next_stage)
+{
+	int ret;
+
+	ret = restore_wait_inprogress_tasks();
+	if (ret)
+		return ret;
+
+	futex_set(&task_entries->nr_in_progress,
+			stage_participants(next_stage));
 	futex_set_and_wake(&task_entries->start, next_stage);
 	return 0;
 }
@@ -1230,12 +1254,26 @@ static int restore_root_task(struct pstree_item *init)
 		return -1;
 	}
 
-	futex_set(&task_entries->nr_in_progress, stage_participants(CR_STATE_FORKING));
+	futex_set(&task_entries->nr_in_progress,
+			stage_participants(CR_STATE_RESTORE_NS));
 
 	ret = fork_with_pid(init);
 	if (ret < 0)
 		return -1;
 
+	pr_info("Wait until namespaces are created\n");
+	ret = restore_wait_inprogress_tasks();
+	if (ret)
+		goto out;
+
+	ret = run_scripts("setup-namespaces");
+	if (ret)
+		goto out;
+
+	ret = restore_switch_stage(CR_STATE_FORKING);
+	if (ret < 0)
+		goto out;
+
 	pr_info("Wait until all tasks are forked\n");
 	ret = restore_switch_stage(CR_STATE_RESTORE_PGID);
 	if (ret < 0)
@@ -1303,7 +1341,7 @@ static int prepare_task_entries()
 	task_entries->nr_threads = 0;
 	task_entries->nr_tasks = 0;
 	task_entries->nr_helpers = 0;
-	futex_set(&task_entries->start, CR_STATE_FORKING);
+	futex_set(&task_entries->start, CR_STATE_RESTORE_NS);
 	mutex_init(&task_entries->zombie_lock);
 
 	return 0;

include/restorer.h

@@ -162,6 +162,7 @@ struct shmems {
 #define TASK_ENTRIES_SIZE 4096
 
 enum {
+	CR_STATE_RESTORE_NS, /* is used for executing "setup-namespace" scripts */
 	CR_STATE_FORKING,
 	CR_STATE_RESTORE_PGID,
 	CR_STATE_RESTORE,