[CRIU] [PATCH v5 5/5] mount: Restore binfmt_misc content in case of missing mount

[Kirill Tkhai]

On 22.08.2016 18:47, Pavel Emelyanov wrote:
>>>>>> @@ -3355,6 +3365,13 @@ static int populate_mnt_ns(void)
>>>>>>  	if (!pms)
>>>>>>  		return -1;
>>>>>>  
>>>>>> +	if (!opts.has_binfmt_misc && stat_image(CR_FD_BINFMT_MISC, &st, 0) == 0) {
>>>>>
>>>>> This should be the other way. In cr-restore.c we have an array of so called cinfos -- these
>>>>> are images that should be pre-loaded during restore. So it's better to add new-style binfmt
>>>>> cinfo and read_mnt_ns_img should check cinfo->flags for COLLECT_HAPPENED (not 100% sure it
>>>>> handles empty images correctly, plz, check) and add cr-time mount if it had.
>>>>
>>>> You had suggested to dump any binfmt_misc content (belonging to a mount point or not)
>>>> to the file of the same name. So, the new suggestion doesn't work.
>>>
>>> Why?
>>
>> Because in case of binfmt_misc image belongs to a real mount, we should not add a cr-time mount;
>> it will be restored when real mount is restored.
>>
>>
>> The second thing I should pointed in previous letter, you have suggested to use opts to check
>> if image present: https://patchwork.criu.org/patch/1069/:
>>
>> "For aufs we have opts.aufs bit. For ... overlayfs (?) we have similar.
>> We can add binfmt_misc to opts, or have separate entity to ask "whether fs X was
>> mounted" for."
>>
>> Why now we are moving to another "check cinfo->flags for COLLECT_HAPPENED" mechanism???
> 
> My point was that you don't need to call stat_image() in the place you do
> explicitly. Instead, add binfmt cinfo that will try to collect the "new style"
> binfmt image and will set the boolean flag about whether or not to add fake
> mount.

Let's say, we collect new binfmt_misc.img and add them to some binfmt_misc_list.
But old type binfmt_misc-xxx.img can't be collected this way. No one of cinfos
has numeric postfix.

So, have we two restore code? One iterates over binfmt_misc_list, another reads
binfmt_misc-xxx.img image?