[Devel] [PATCH rh7 v2] vtty: Allow to wait until container's console appear

[Cyrill Gorcunov]

After tty code redesing we've been requiring container to start
first before be able to connect into it via vzctl console command.
Here we rather allow userspace tool to wait until container brought
to life and proceed connecting into console.

https://jira.sw.ru/browse/PSBM-39463

Note: when someone tried to open several consoles for offline
mode (say vzctl console 300 1 and vzctl console 300 2) simultaneously
only one is allowed until VE is up, the second vzctl command will
exit with -EBUSY.

v2:
 - move everything into vtty code

Signed-off-by: Cyrill Gorcunov <gorcunov at virtuozzo.com>
CC: Vladimir Davydov <vdavydov at virtuozzo.com>
CC: Konstantin Khorenko <khorenko at virtuozzo.com>
CC: Igor Sukhih <igor at virtuozzo.com>
CC: Pavel Emelyanov <xemul at virtuozzo.com>
---
 drivers/tty/pty.c   |   67 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/ve.h  |    2 +
 kernel/ve/ve.c      |    5 +++
 kernel/ve/vecalls.c |    6 ++--
 4 files changed, 77 insertions(+), 3 deletions(-)

Index: linux-pcs7.git/drivers/tty/pty.c
===================================================================
--- linux-pcs7.git.orig/drivers/tty/pty.c
+++ linux-pcs7.git/drivers/tty/pty.c
@@ -1284,8 +1284,64 @@ static int __init vtty_init(void)
 	return 0;
 }
 
+static DECLARE_RWSEM(vtty_console_sem);
+static DEFINE_IDR(vtty_idr_console);
+
+static struct ve_struct *vtty_get_ve_by_id(envid_t veid)
+{
+	DECLARE_COMPLETION_ONSTACK(console_work);
+	struct ve_struct *ve;
+	int ret;
+
+	down_write(&vtty_console_sem);
+	ve = get_ve_by_id(veid);
+	if (ve) {
+		up_write(&vtty_console_sem);
+		return ve;
+	}
+
+	if (idr_find(&vtty_idr_console, veid)) {
+		up_write(&vtty_console_sem);
+		return ERR_PTR(-EBUSY);
+	}
+
+	ret = idr_alloc(&vtty_idr_console, &console_work, veid, veid + 1, GFP_KERNEL);
+	if (ret < 0) {
+		if (ret == -ENOSPC)
+			ret = -EBUSY;
+	} else
+		ret = 0;
+	up_write(&vtty_console_sem);
+
+	if (!ret)
+		ret = wait_for_completion_interruptible(&console_work);
+
+	if (!ret)
+		ve = get_ve_by_id(veid);
+	else
+		ve = ERR_PTR(ret);
+
+	down_write(&vtty_console_sem);
+	if (!ret)
+		idr_remove(&vtty_idr_console, veid);
+	up_write(&vtty_console_sem);
+	return ve;
+}
+
+void vtty_console_notify(struct ve_struct *ve)
+{
+	struct completion *console_work;
+
+	down_read(&vtty_console_sem);
+	console_work = idr_find(&vtty_idr_console, ve->veid);
+	if (console_work)
+		complete(console_work);
+	up_read(&vtty_console_sem);
+}
+
 int vtty_open_master(envid_t veid, int idx)
 {
+	struct ve_struct *ve = NULL;
 	struct tty_struct *tty;
 	struct file *file;
 	char devname[64];
@@ -1298,6 +1354,16 @@ int vtty_open_master(envid_t veid, int i
 	if (fd < 0)
 		return fd;
 
+	ve = vtty_get_ve_by_id(veid);
+	if (IS_ERR_OR_NULL(ve)) {
+		if (IS_ERR(ve))
+			ret = PTR_ERR(ve);
+		else
+			ret = -ENOENT;
+		ve = NULL;
+		goto err_put_unused_fd;
+	}
+
 	snprintf(devname, sizeof(devname), "v%utty%d", veid, idx);
 	file = anon_inode_getfile(devname, &vtty_fops, NULL, O_RDWR);
 	if (IS_ERR(file)) {
@@ -1364,6 +1430,7 @@ int vtty_open_master(envid_t veid, int i
 	mutex_unlock(&tty_mutex);
 	ret = fd;
 out:
+	put_ve(ve);
 	return ret;
 
 err_install:
Index: linux-pcs7.git/include/linux/ve.h
===================================================================
--- linux-pcs7.git.orig/include/linux/ve.h
+++ linux-pcs7.git/include/linux/ve.h
@@ -215,6 +215,8 @@ void ve_stop_ns(struct pid_namespace *ns
 void ve_exit_ns(struct pid_namespace *ns);
 int ve_start_container(struct ve_struct *ve);
 
+void vtty_console_notify(struct ve_struct *ve);
+
 extern bool current_user_ns_initial(void);
 struct user_namespace *ve_init_user_ns(void);
 
Index: linux-pcs7.git/kernel/ve/ve.c
===================================================================
--- linux-pcs7.git.orig/kernel/ve/ve.c
+++ linux-pcs7.git/kernel/ve/ve.c
@@ -494,6 +494,11 @@ int ve_start_container(struct ve_struct
 
 	get_ve(ve); /* for ve_exit_ns() */
 
+	/*
+	 * Console waiter are to be notified at the very
+	 * end when everything else is ready.
+	 */
+	vtty_console_notify(ve);
 	return 0;
 
 err_iterate:
Index: linux-pcs7.git/kernel/ve/vecalls.c
===================================================================
--- linux-pcs7.git.orig/kernel/ve/vecalls.c
+++ linux-pcs7.git/kernel/ve/vecalls.c
@@ -990,6 +990,9 @@ static int ve_configure(envid_t veid, un
 	struct ve_struct *ve;
 	int err = -ENOKEY;
 
+	if (key == VE_CONFIGURE_OPEN_TTY)
+		return vtty_open_master(veid, val);
+
 	ve = get_ve_by_id(veid);
 	if (!ve)
 		return -EINVAL;
@@ -998,9 +1001,6 @@ static int ve_configure(envid_t veid, un
 	case VE_CONFIGURE_OS_RELEASE:
 		err = init_ve_osrelease(ve, data);
 		break;
-	case VE_CONFIGURE_OPEN_TTY:
-		err = vtty_open_master(ve->veid, val);
-		break;
 	}
 
 	put_ve(ve);