[CRIU] [RFC PATCH 3/6] introduce mnt_entry->fsname for FSTYPE__AUTO filesystems

[Pavel Emelyanov]

On 03/31/2015 05:18 PM, Oleg Nesterov wrote:
> On 03/31, Pavel Emelyanov wrote:
>>
>> On 03/31/2015 03:56 PM, Oleg Nesterov wrote:
>>
>>> No. Well yes, de-duplication is good too, but this is minor.
>>>
>>> The main problem is that (I think) we need (or at least want) to re-create the
>>> FSTYPE__AUTO entries asap, before collect_mnt_from_image().
>>
>> Why?! And how, at restore time all entries are read from image, how can we
>> recreate anything before we read them?
>>
>>> See above, parse_mountinfo() is called before this stage. Again, iiuc currently
>>> this doesn't matter correctness wise, but this looks unsafe. At least inconsistent.
>>> It would be better to ensure that "restore" never sees (say) hugetlbfs as
>>> FSTYPE__UNSUPPORTED if it was dumped as FSTYPE__AUTO. Even if (iiuc) collect_mntinfo()
>>> is called to umount everything and thus FSTYPE__UNSUPPORTED is fine.
>>
>> But if the entry in the image _is_ auto, how can restore see it as unsupported?
> 
> Sorry for confusion. I didn't mean collect_mnt_from_image(), of course it
> will see FSTYPE__AUTO with the patches I sent.
> 
> But note that prepare_mnt_ns() calls collect_mntinfo() to umount everything
> before we start to restore the mnt namespace.
> 
> And collect_mntinfo() paths can see the same fsnames as UNSUPPORTED. Again,
> I do not really think this can make any harm, just this doesn't look good.

Ah! This collection is only required for one thing -- to unmount all this
crap in case we're not restoring into new --root root. So seeing this stuff
as even unsupported will work :)

>>> OK. If we can abuse inventory_entry, I'll try to do this. We will see if this
>>> looks better or not. If not, we can return to mnt_entry->fsname.
>>
>> I didn't tell we could abuse inventory :) I told we could add new stuff to
>> mnt entry. But since I still don't understand what the problem is, you can
>> try to abuse inventory and see how it goes.
> 
> Yes, yes, this will be RFC anyway. I can always switch back to the new field
> in mnt entry.

Yup :)

-- Pavel