Re: [PATCH v3 2/6] nbd: Add 'qemu-nbd -A' to expose allocation depth

[Eric Blake]

On 10/9/20 4:03 AM, Richard W.M. Jones wrote:

>>> +++ b/qapi/block-core.json
>>> @@ -3882,9 +3882,12 @@
>>>  #
>>>  # @tls-creds: TLS credentials ID
>>>  #
>>> -# @x-dirty-bitmap: A "qemu:dirty-bitmap:NAME" string to query in place of
>>> +# @x-dirty-bitmap: A metacontext name such as "qemu:dirty-bitmap:NAME" or
>>
>> What is a "metacontext"?
>>
>> Aside: nbd.h spells it "meta context".  The two spellings suggest
>> different meanings to me.  Using meta- as a prefix modifies the prefixed
>> word, as in metadata (data that provides information about other data).
>> Separated by space, meta becomes a noun.  None of its common meanings
>> seem to apply here.  Recommend to pick an appropriate one of
>> "metacontext", "meta-context", "meta context", and stick to it.
> 
> In the NBD protocol it's called a "metadata context".  This is
> abbreviated to "...META_CONTEXT" in the names of constants,
> eg. NBD_OPT_SET_META_CONTEXT.  For the reasons you gave I don't think
> it's a very good name, but it's what we have.
> 
> https://github.com/NetworkBlockDevice/nbd/blob/master/doc/proto.md#metadata-querying
> 
> What it actually is, is a string, like "base:allocation" or
> "qemu:dirty-bitmap:<NAME>" which selects which metadata you want to
> query in NBD_CMD_BLOCK_STATUS commands.

Sounds like documenting it as a "metadata context name" is probably the
one to use then. I'll make that adjustment.

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

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