Re: [Qemu-block] [Qemu-devel] [PATCH] migration: disallow migrate_add_blocker during migration

[Markus Armbruster]

Kevin Wolf <address@hidden> writes:

> Am 29.09.2015 um 22:20 hat John Snow geschrieben:
>> If a migration is already in progress and somebody attempts
>> to add a migration blocker, this should rightly fail.
>> 
>> Add an errp parameter and a retcode return value to migrate_add_blocker.
>> 
>> This is part one of two for a solution to prohibit e.g. block jobs
>> from running concurrently with migration.
>> 
>> Signed-off-by: John Snow <address@hidden>
[...]
>> diff --git a/hw/misc/ivshmem.c b/hw/misc/ivshmem.c
>> index cc76989..859e844 100644
>> --- a/hw/misc/ivshmem.c
>> +++ b/hw/misc/ivshmem.c
>> @@ -740,7 +740,10 @@ static int pci_ivshmem_init(PCIDevice *dev)
>>      if (s->role_val == IVSHMEM_PEER) {
>>          error_setg(&s->migration_blocker,
>>                     "Migration is disabled when using feature 'peer mode' in 
>> device 'ivshmem'");
>> -        migrate_add_blocker(s->migration_blocker);
>> +        if (migrate_add_blocker(s->migration_blocker, NULL) < 0) {
>> +            error_report("Unable to prohibit migration during ivshmem 
>> init");
>> +            exit(1);
>
> Seriously? :-/
>
> I see that the whole function does the same and has an int return value
> only so that it can always return 0. So what you're doing is probably
> right for this patch, but generally, the error handling in this init
> function is horrible.

Horrible indeed.  Marc-André's series to clean it up clocks in at 47
patches right now.

Message-Id: <address@hidden>
http://lists.gnu.org/archive/html/qemu-devel/2015-09/msg06302.html

> The good thing is that you can't leak anything this way...
>
>> +        }
>>      }
>>  
>>      pci_conf = dev->config;
[...]