Re: [PATCH 02/18] fuse: Allow exporting BDSs via FUSE

[Markus Armbruster]

Kevin Wolf <address@hidden> writes:

> Am 19.12.2019 um 15:38 hat Max Reitz geschrieben:
>> fuse-export-add allows mounting block graph nodes via FUSE on some
>> existing regular file.  That file should then appears like a raw disk
>> image, and accesses to it result in accesses to the exported BDS.
>> 
>> Right now, we only set up the mount point and tear all mount points down
>> in bdrv_close_all().  We do not implement any access functions, so
>> accessing the mount point only results in errors.  This will be
>> addressed by a followup patch.
>> 
>> The set of exported nodes is kept in a hash table so we can later add a
>> fuse-export-remove that allows unmounting.
>> 
>> Signed-off-by: Max Reitz <address@hidden>
>
>> diff --git a/qapi/block.json b/qapi/block.json
>> index 145c268bb6..03f8d1b537 100644
>> --- a/qapi/block.json
>> +++ b/qapi/block.json
>> @@ -317,6 +317,29 @@
>>  ##
>>  { 'command': 'nbd-server-stop' }
>>  
>> +##
>> +# @fuse-export-add:
>> +#
>> +# Exports a block graph node on some (file) mountpoint as a raw image.
>> +#
>> +# @node-name: Node to be exported
>> +#
>> +# @mountpoint: Path on which to export the block device via FUSE.
>> +#              This must point to an existing regular file.
>> +#
>> +# @writable: Whether clients should be able to write to the block
>> +#            device via the FUSE export. (default: false)
>> +#
>> +# Since: 5.0
>> +##
>> +{ 'command': 'fuse-export-add',
>> +  'data': {
>> +      'node-name': 'str',
>> +      'mountpoint': 'str',
>> +      '*writable': 'bool'
>> +  },
>> +  'if': 'defined(CONFIG_FUSE)' }
>
> Can this use a BlockExport union from the start like I'm introducing in
> the storage daemon series, together with a generic block-export-add?
>
> It also looks like node-name and writable should be part of the common
> base of BlockExport. Unfortunately this would mean that I can't use the
> same BlockExportNbd for the existing nbd-server-add command any more. I
> guess I could somehow get a shared base type for both, though.
>
> Markus, any thoughts on these QAPI interfaces?

Context?  How far back should I read?