[CRIU] [PATCH CRIU 1/4] mount: get over autodetected mounts in search for widest shared peer

[Pavel Tikhomirov]

On 01/20/2016 09:23 PM, Andrew Vagin wrote:
> On Wed, Jan 20, 2016 at 06:42:55PM +0300, Pavel Tikhomirov wrote:
>> now all autodetected mounts are considered to be shared - fix it
>
> I don't understand what and how you fix.

In collect_mnt_namespaces->resolve_external_mounts if "--ext-mount-map 
auto" is set all mounts which are resolved external have set 
m->external->val = "CRIU:AUTOGENERATED". Thus in dump_one_mountpoint, 
m->root is set to it. So on restore in prepare_namespace->prepare_mnt_ns
->populate_mnt_ns->validate_mounts->find_widest_shared->issubpath
for all external mounts we check issubpath("CRIU:AUTOGENERATED", 
"CRIU:AUTOGENERATED") and for matched mounts check that they are equal. 
So next in validate_shared validation fails for really different 
external mounts. I propose to check sources for such mounts instead of 
roots.

>
>>
>> In VZ7:
>> vzctl exec 101 mkdir /testmounts /testmounts/dir /testmounts/bind
>> 	/testmounts/tmp /testmounts/dir/b
>> vzctl exec 101 mount --bind /testmounts/dir /testmounts/bind
>> vzctl exec 101 mount --bind /testmounts/tmp /testmounts/bind/b
>> vzctl suspend 101; vzctl resume 101
>>
>> In criu logs:
>> The restore log was saved in /vz/private/101/dump/Dump/restore.log
>> Failed to restore the Container
>>
>> (00.213750)      1: Error (mount.c:631): mnt: 134:./testmounts/bind and
>> 137:./testmounts/dir/b have different set of mounts
>>
>> but those two are really different
>>
>> https://jira.sw.ru/browse/PSBM-42829
>> Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
>> ---
>>   mount.c | 17 +++++++++++++++--
>>   1 file changed, 15 insertions(+), 2 deletions(-)
>>
>> diff --git a/mount.c b/mount.c
>> index 9d5667a..e267e10 100644
>> --- a/mount.c
>> +++ b/mount.c
>> @@ -472,14 +472,27 @@ static int try_resolve_ext_mount(struct mount_info *info)
>>   static struct mount_info *find_widest_shared(struct mount_info *m)
>>   {
>>   	struct mount_info *p;
>> +	bool madm = !strcmp(m->root, AUTODETECTED_MOUNT);
>>
>>   	/*
>>   	 * Try to find a mount, which is wider or equal.
>>   	 * A is wider than B, if A->root is a subpath of B->root.
>>   	 */
>> -	list_for_each_entry(p, &m->mnt_share, mnt_share)
>> -		if (issubpath(m->root, p->root))
>> +	list_for_each_entry(p, &m->mnt_share, mnt_share) {
>> +		bool padm = !strcmp(p->root, AUTODETECTED_MOUNT);
>> +
>> +		/* Skip check between different kinds of mounts */
>> +		if (madm != padm)
>> +			continue;
>> +
>> +		/*
>> +		 * Compare source for autodetected mounts as
>> +		 * root is always "CRIU:AUTOGENERATED" for them
>> +		 */
>> +		if ((madm && issubpath(m->source, p->source))
>> +		    || (!madm && issubpath(m->root, p->root)))
>>   			return p;
>> +	}
>>
>>   	return NULL;
>>   }
>> --
>> 1.9.3
>>