Re: [Qemu-devel] [PATCH] nbd: Advertise multi-conn for shared read-only connections

[Eric Blake <eblake@redhat.com>]

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On 8/16/19 5:47 AM, Vladimir Sementsov-Ogievskiy wrote:

>>> +++ b/blockdev-nbd.c
>>> @@ -189,7 +189,7 @@ void qmp_nbd_server_add(const char *device, bool has_name, const char *name,
>>>       }
>>>
>>>       exp = nbd_export_new(bs, 0, len, name, NULL, bitmap,
>>> -                         writable ? 0 : NBD_FLAG_READ_ONLY,
>>> +                         writable ? 0 : NBD_FLAG_READ_ONLY, true,
>>
>> s/true/!writable ?
> 
> Oh, I see, John already noticed this, it's checked in nbd_export_new anyway..

Still, since two reviewers have caught it, I'm fixing it :)


>>> @@ -1486,6 +1486,8 @@ NBDExport *nbd_export_new(BlockDriverState *bs, uint64_t dev_offset,
>>>       perm = BLK_PERM_CONSISTENT_READ;
>>>       if ((nbdflags & NBD_FLAG_READ_ONLY) == 0) {
>>>           perm |= BLK_PERM_WRITE;
>>> +    } else if (shared) {
>>> +        nbdflags |= NBD_FLAG_CAN_MULTI_CONN;
> 
> For me it looks a bit strange: we already have nbdflags parameter for nbd_export_new(), why
> to add a separate boolean to pass one of nbdflags flags?

Because I want to get rid of the nbdflags in my next patch.

> 
> Also, for qemu-nbd, shouldn't we allow -e only together with -r ?

I'm reluctant to; it might break whatever existing user is okay exposing
it (although such users are questionable, so maybe we can argue they
were already broken).  Maybe it's time to start a deprecation cycle?

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


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