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

[Pavel Emelyanov]

On 04/23/2015 06:09 PM, Tycho Andersen wrote:
> On Thu, Apr 23, 2015 at 06:04:35PM +0300, Pavel Emelyanov wrote:
>> On 04/23/2015 05:31 PM, Tycho Andersen wrote:
>>> On Thu, Apr 23, 2015 at 02:52:35PM +0300, Pavel Emelyanov wrote:
>>>> On 04/23/2015 02:17 PM, Oleg Nesterov wrote:
>>>>
>>>>> Now what? Obviously we can't just add
>>>>>
>>>>> 	if (is_not_external_mount(m))
>>>>> 		continue;
>>>>
>>>> Why not? The is_not_external_mount() is
>>>>
>>>> fsroot_mounted(m) || /* mount's root is visible from chroot */
>>>
>>> But what if the mount's root is /? e.g with pstore in lxc, the
>>> mountinfo from inside looks like:
>>>
>>> 110 104 0:23 / /sys/fs/pstore rw,nosuid,nodev,noexec,relatime master:11 - pstore pstore rw
>>>
>>> which is a bind mount from the host's:
>>>
>>> 29 17 0:23 / /sys/fs/pstore rw,nosuid,nodev,noexec,relatime shared:11 - pstore pstore rw
>>
>> Ah, so sharing takes place. OK, then (sorry, maybe I'm replaying your
>> conversation again, but I'm still blind about it) the check should be
>>
>>    (fsroot_mounted(m) || root_is_visible(m)) && master_is_external(m)
> 
> I think not, because if we didn't have this as a shared mount it would
> still be an external bind mount, just without sharing. An external
> master peer is an indication that it's a bind mount, but if we don't
> have one of those, it could still be a bind mount.

Ah, sure. It should be NOT before master_is_external, like this

   (fsroot_mounted(m) || root_is_visible(m)) && !master_is_external()

Provided master_is_external() is false for private mounts, this should
handle Oleg's case with mount --make-rprivate, but in suboptimal way --
all mountpoints will be bind-mounted from host with MS_SLAVE flag.

-- Pavel