Re: [Qemu-devel] [Qemu-block] [PATCH RFC v3 3/8] block: add throttle block filter driver

[Manos Pitsidianakis <el13635@mail.ntua.gr>]

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On Mon, Jun 26, 2017 at 03:30:55PM +0100, Stefan Hajnoczi wrote:
>> +static BlockDriver bdrv_throttle = {
>> +    .format_name                        =   "throttle",
>> +    .protocol_name                      =   "throttle",
>> +    .instance_size                      =   sizeof(ThrottleGroupMember),
>> +
>> +    .bdrv_file_open                     =   throttle_open,
>> +    .bdrv_close                         =   throttle_close,
>> +    .bdrv_co_flush                      =   throttle_co_flush,
>> +
>> +    .bdrv_child_perm                    =   bdrv_filter_default_perms,
>> +
>> +    .bdrv_getlength                     =   throttle_getlength,
>> +
>> +    .bdrv_co_preadv                     =   throttle_co_preadv,
>> +    .bdrv_co_pwritev                    =   throttle_co_pwritev,
>> +
>> +    .bdrv_co_pwrite_zeroes              =   throttle_co_pwrite_zeroes,
>> +    .bdrv_co_pdiscard                   =   throttle_co_pdiscard,
>> +
>> +    .bdrv_recurse_is_first_non_filter   =   bdrv_recurse_is_first_non_filter,
>> +
>> +    .bdrv_attach_aio_context            =   throttle_attach_aio_context,
>> +    .bdrv_detach_aio_context            =   throttle_detach_aio_context,
>> +
>> +    .bdrv_reopen_prepare                =   throttle_reopen_prepare,
>> +    .bdrv_reopen_commit                 =   throttle_reopen_commit,
>> +    .bdrv_reopen_abort                  =   throttle_reopen_abort,
>> +
>> +    .is_filter                          =   true,
>> +};
>
>Missing:
>bdrv_co_get_block_status()
>bdrv_truncate()
>bdrv_get_info()
>bdrv_probe_blocksizes()
>bdrv_probe_geometry()
>bdrv_media_changed()
>bdrv_eject()
>bdrv_lock_medium()
>bdrv_co_ioctl()
>
>See block/raw-format.c.
>
>I think most of these could be modified in block.c or block/io.c to
>automatically call bs->file's function if drv doesn't implement them.
>This way all block drivers would transparently pass them through by
>default and block/raw-format.c code could be eliminated.

Are these truly necessary? Because other filter drivers (ie quorum, 
blkverify) don't implement them.

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