Re: [Qemu-block] [PATCH 02/18] blockjob: introduce .drain callback for jobs

[Paolo Bonzini]

On 16/10/2016 12:02, Stefan Hajnoczi wrote:
> On Thu, Oct 13, 2016 at 07:34:06PM +0200, Paolo Bonzini wrote:
>> +static void backup_drain(BlockJob *job)
>> +{
>> +    BackupBlockJob *s = container_of(job, BackupBlockJob, common);
>> +
>> +    /* Need to keep a reference in case blk_drain triggers execution
>> +     * of backup_complete...
>> +     */
>> +    if (s->target) {
>> +        blk_ref(s->target);
>> +        blk_drain(s->target);
>> +        blk_unref(s->target);
>> +    }
> [...]
>> @@ -331,6 +346,7 @@ static void backup_complete(BlockJob *job, void *opaque)
>>      BackupCompleteData *data = opaque;
>>  
>>      blk_unref(s->target);
>> +    s->target = NULL;
> 
> Will blk_unref(s->target) segfault since backup_complete() has set it to
> NULL?  I expected backup_drain() to stash the pointer in a local
> variable to avoid using s->target.

Yes, indeed.

Paolo