Re: [Qemu-devel] [PATCH v2 5/6] nbd: Merge nbd_export_bitmap into nbd_export_new

[Eric Blake <eblake@redhat.com>]

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On 1/10/19 6:25 AM, Vladimir Sementsov-Ogievskiy wrote:
> 10.01.2019 10:13, Eric Blake wrote:
>> We only have one caller that wants to export a bitmap name,
>> which it does right after creation of the export. But there is
>> still a brief window of time where an NBD client could see the
>> export but not the dirty bitmap, which a robust client would
>> have to interpret as meaning the entire image should be treated
>> as dirty.  Better is to eliminate the window entirely, by
>> inlining nbd_export_bitmap() into nbd_export_new(), and refusing
>> to create the bitmap in the first place if the requested bitmap
>> can't be located.
>>
>> We also no longer need logic for setting a different bitmap
>> name compared to the bitmap being exported.
>>

>> +++ b/blockdev-nbd.c
>> @@ -175,7 +175,7 @@ void qmp_nbd_server_add(const char *device, bool has_name, const char *name,
>>           writable = false;
>>       }
>>
>> -    exp = nbd_export_new(bs, 0, -1, name, NULL,
>> +    exp = nbd_export_new(bs, 0, -1, name, NULL, bitmap,
> 
> bitmap is guaranteed to be NULL if has_bitmap is false? Or should we do has_bitmap ? bitmap : NULL?

We fixed our QAPI generators to guarantee that has_foo = false implies
foo == NULL, several years ago.  If you populate a QAPI struct by hand
instead of via the generated visitors, you should use g_malloc0() to
match the same guarantees.  So I don't need the ?:.

> 
> if yes or with fixed:
> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> 
> 

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org


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