[CRIU] [PATCH 00/11] tty: Add c/r for system console

[Cyrill Gorcunov]

On Mon, Sep 29, 2014 at 06:31:51PM -0500, Tycho Andersen wrote:
> Hi Cyrill,
> 
> On Mon, Sep 29, 2014 at 08:25:26PM +0400, Cyrill Gorcunov wrote:
> > Hi guys, here is a series which implements c/r for /dev/console,
> > I'm not really sure how to test it -- I simply modified our pty00
> > test case adding
> > 
> > 	console = open("/dev/console", O_RDONLY);
> > 
> > into it to check that c/r flow takes proper branches (and looked
> > into image data).
> > 
> > I guess some help needed presumably attempting to c/r lxc conatiner
> > with /dev/console bound to some readable output.
> > 
> > Anyway, any feedback would be highly appreciated!
> 
> Thanks for your work on this set. This patch does fix the aforementioned bug
> about not being able to checkpoint containers that have been restored. (I'm not
> sure which patch does it, but with the entire series applied it works just
> fine. I can go back and find out if this information would be useful.)

Hi Tycho! Thanks a lot for giving it a shot (and btw I remember about the
problem with sequential c/r where second dump failed due to tty layer, simply
didn't manage yet to investigate, I suspect I need to achieve same error on
my testing node, once I manage to I'll ping you, hopefully on the week).

> 
> However, when I try to checkpoint a container with /dev/console and some ttys, I
> get:
> 
> Error (mount.c:453): 113:./dev/lxc/tty4 doesn't have a proper root mount
> 
> On an LXC in my system with ttys enabled, the /proc/self/mountinfo has:
> 
> ubuntu at u1:~$ cat /proc/self/mountinfo 
> 75 76 253:1 /usr/local/var/lib/lxc/u1/rootfs / rw,relatime - ext4 /dev/disk/by-uuid/7fd0b676-46f3-46d6-94a6-5c620e72e7b0 rw,data=ordered
> 103 75 0:35 / /proc rw,nosuid,nodev,noexec,relatime - proc proc rw
> 104 75 0:33 / /sys rw,relatime - sysfs sysfs rw
> 105 104 0:18 / /sys/fs/fuse/connections rw,relatime - fusectl none rw
> 106 104 0:6 / /sys/kernel/debug rw,relatime - debugfs none rw
> 107 104 0:10 / /sys/kernel/security rw,relatime - securityfs none rw
> 108 104 0:22 / /sys/fs/pstore rw,relatime - pstore none rw
> 109 75 0:12 /7 /dev/lxc/console rw,nosuid,noexec,relatime - devpts devpts rw,gid=5,mode=620,ptmxmode=000
> 110 75 0:12 /1 /dev/lxc/tty1 rw,nosuid,noexec,relatime - devpts devpts rw,gid=5,mode=620,ptmxmode=000
> 111 75 0:12 /3 /dev/lxc/tty2 rw,nosuid,noexec,relatime - devpts devpts rw,gid=5,mode=620,ptmxmode=000
> 112 75 0:12 /5 /dev/lxc/tty3 rw,nosuid,noexec,relatime - devpts devpts rw,gid=5,mode=620,ptmxmode=000
> 113 75 0:12 /6 /dev/lxc/tty4 rw,nosuid,noexec,relatime - devpts devpts rw,gid=5,mode=620,ptmxmode=000
> 77 75 0:36 / /dev/pts rw,relatime - devpts devpts rw,gid=5,mode=620,ptmxmode=666
> 78 75 0:36 /ptmx /dev/ptmx rw,relatime - devpts devpts rw,gid=5,mode=620,ptmxmode=666
> 79 104 0:37 / /sys/fs/cgroup rw,relatime - tmpfs none rw,size=4k,mode=755
> 80 75 0:38 / /run rw,nosuid,noexec,relatime - tmpfs none rw,size=200060k,mode=755
> 81 80 0:39 / /run/lock rw,nosuid,nodev,noexec,relatime - tmpfs none rw,size=5120k
> 82 80 0:40 / /run/shm rw,nosuid,nodev,relatime - tmpfs none rw
> 83 80 0:41 / /run/user rw,nosuid,nodev,noexec,relatime - tmpfs none rw,size=102400k,mode=755
> 

Mind to share your lxc conatiner details and how you set it up?

> When I try to work around that with something like,
> 
> diff --git a/mount.c b/mount.c
> index 8c60693..a28e041 100644
> --- a/mount.c
> +++ b/mount.c
> @@ -433,8 +433,19 @@ static int validate_mounts(struct mount_info *info, bool for_dump)
>  					ret = run_plugins(DUMP_EXT_MOUNT, m->mountpoint, m->mnt_id);
>  					if (ret == 0)
>  						m->need_plugin = true;
> -					else if (ret == -ENOTSUP)
> -						ret = try_resolve_ext_mount(m);
> +					else if (ret == -ENOTSUP) {
> +						/* inside containers
> +						 * /dev/console and /dev/tty*
> +						 * are mounted from paths like
> +						 * /5 or /6, so we ignore
> +						 * their path here if things
> +						 * go bad.
> +						 */
> +						if (m->fstype->code == FSTYPE__DEVPTS)
> +							ret = 0;
> +						else
> +							ret = try_resolve_ext_mount(m);
> +					}
>  				} else {
>  					if (m->need_plugin || m->external)
>  						/*
> 
> 
> I hit:
> 
> (00.247031) Error (tty.c:233): tty: Unexpected format on path /dev/lxc/tty4
> 
> which looks like it might be a bigger problem :)
> 
> Any thoughts are appreciated.

Show me the stat output on this paths please? (stat /dev/lxc/tty4)