Re: [Qemu-devel] [PATCH] Further tidy-up on block status

[Alex Bligh]

Vladimir,

>> +non-zero number of metadata contexts during negotiation. Servers SHOULD
>> +reply to clients sending `NBD_CMD_BLOCK_STATUS without
> 
> backquote

Fixed

>> +    If zero queries are sent, then the server MUST return all
>> +    the metadata contexts it knows about.
> 
> I think that 'all .. it knows about' is too much. What about 'return all 
> available ..'? Anyway 'all ... it knows about' actually equals to 'all ... it 
> wants'. There may be some private, or unrelated contexts, for example..

This was not my wording, but I've changed it anyway to:

    If zero queries are sent, then the server MUST return all
    the metadata contexts that are available to the client to select
    on the given export with `NBD_OPT_SET_META_CONTEXT`.

I think if they are available to select, we should list them. Thanks
also for reminding me to document why I put the export name into the
_LIST_ data (as it is for _SET_).

However, this raises another question. Wouter deliberately made the
query format freeform so that you could e.g. set a context like:

   backup:modtime>201612081034

which might (in theory) return a list of blocks which are newer than
the given timestamp. It would clearly be impossible to return all such
contexts. I wonder if we should carve out an exception here.

-- 
Alex Bligh