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

[Alex Bligh <alex@...872...>]

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