[CRIU] Sync TODO-s for mount.c work

[Oleg Nesterov]

Tycho,

Thanks for your answers. I feel I should not waste your time until I
try to read the docs and the code, but let me ask another question
right now.

On 04/22, Tycho Andersen wrote:
>
> On Wed, Apr 22, 2015 at 9:35 AM, Oleg Nesterov <oleg at redhat.com> wrote:
> >
> > OK, before I dive into the sources, could you please tell me what
> > should I pass as KEY:VAL pair? (I didn't read this code yet and I
> > am not sure if I can understand it, at least quickly).
>
> Looking at your mountinfo, I'm not sure you can dump this process. The
> problem is e.g.:
>
> 36 34 253:1 / / rw,relatime shared:7 master:1 - xfs
> /dev/mapper/rhel_ibm--x3650m4--02--vm--02-root
> rw,seclabel,attr2,inode64,noquota
>
> This is not a bind mount, but it has external sharing according to the
> rest of your mountinfo (there is no "shared:1" anywhere). There is no
> way to tell criu (currently) to allow mounts that aren't bind mounts
> to have sharing.

Hmm. But it fails because it can't dump the _bind_ mount?

> I guess this configuration is the result of something
> like:
>
> unshare(CLONE_NEWNS)
> mount(NULL, "/", NULL, MS_PRIVATE, NULL)

MS_SLAVE + MS_SHARED according to strace...


> so all criu needs to do is learn how to do that and it should be ok.

Let me start from the very beginning.

	# unshare -m
	# perl -e 'close STDIN; close STDOUT; close STDERR; sleep'

dump/restore from the root ns works.

	# unshare -m
	# mount --make-slave /
	# mount --make-shared /
	# perl -e 'close STDIN; close STDOUT; close STDERR; sleep'
	
dump/restore still work

	# unshare -m
	# mount --make-slave /
	# mount --make-shared /
	# mkdir /tmp/A /tmp/B
	# mount --bind /tmp/A /tmp/B
	# perl -e 'close STDIN; close STDOUT; close STDERR; sleep' 

Now it fails with the same

	Mount 35 ./tmp/B (master_id: 1 shared_id: 7) has unreachable sharing.

error message.

Why "restore" can't dump it? "restore" could simply do MS_BIND?

Oleg.