Re: [Qemu-devel] [PATCH 2/3] file: Expose some protocol-specific information

[Vladimir Sementsov-Ogievskiy]

17.01.2019 18:33, Eric Blake wrote:
> When analyzing performance, it might be nice to let 'qemu-img info'
> expose details that it learned from the underlying file or block
> device.  Start the process by picking a few useful items determined
> during raw_open_common().
> 
> Signed-off-by: Eric Blake <address@hidden>
> ---
>   qapi/block-core.json | 24 +++++++++++++++++++++++-
>   block/file-posix.c   | 21 +++++++++++++++++++++
>   2 files changed, 44 insertions(+), 1 deletion(-)
> 
> diff --git a/qapi/block-core.json b/qapi/block-core.json
> index f28d5f5fc76..296c22a1003 100644
> --- a/qapi/block-core.json
> +++ b/qapi/block-core.json
> @@ -101,6 +101,25 @@
>         'extents': ['ImageInfo']
>     } }
> 
> +##
> +# @ImageInfoSpecificFile:
> +#
> +# Details about a file protocol BDS.
> +#
> +# @align: Alignment in use
> +#
> +# @discard: True if discard operations can be attempted
> +#
> +# @write-zero: True if efficient write zero operations can be attempted
> +#
> +# @discard-zero: True if discarding is known to read back as zero
> +#
> +# Since: 4.0
> +##
> +{ 'struct': 'ImageInfoSpecificFile',
> +  'data': { 'align': 'int', 'discard': 'bool', 'write-zero': 'bool',
> +            '*discard-zero': 'bool' } }

Not sure if this works, as I remember raw-posix will adjust these fields
on first failed write, and without this first write, we will not actually
know are they supported.

> +
>   ##
>   # @ImageInfoSpecific:
>   #
> @@ -110,12 +129,15 @@
>   ##
>   { 'union': 'ImageInfoSpecific',
>     'data': {
> +      # Format drivers:
>         'qcow2': 'ImageInfoSpecificQCow2',
>         'vmdk': 'ImageInfoSpecificVmdk',
>         # If we need to add block driver specific parameters for
>         # LUKS in future, then we'll subclass QCryptoBlockInfoLUKS
>         # to define a ImageInfoSpecificLUKS
> -      'luks': 'QCryptoBlockInfoLUKS'
> +      'luks': 'QCryptoBlockInfoLUKS',
> +      # Protocol drivers:
> +      'file': 'ImageInfoSpecificFile'
>     } }
> 
>   ##
> diff --git a/block/file-posix.c b/block/file-posix.c
> index 8aee7a3fb8b..d4ce0e9116c 100644
> --- a/block/file-posix.c
> +++ b/block/file-posix.c
> @@ -1079,6 +1079,23 @@ static void raw_refresh_limits(BlockDriverState *bs, 
> Error **errp)
>       bs->bl.opt_mem_alignment = MAX(s->buf_align, getpagesize());
>   }
> 
> +static ImageInfoSpecific *raw_get_specific_info(BlockDriverState *bs)
> +{
> +    BDRVRawState *s = bs->opaque;
> +    ImageInfoSpecific *info = g_new0(ImageInfoSpecific, 1);
> +    ImageInfoSpecificFile *infofile = g_new0(ImageInfoSpecificFile, 1);
> +
> +    info->type = IMAGE_INFO_SPECIFIC_KIND_FILE;
> +    info->u.file.data = infofile;
> +    infofile->align = s->buf_align;
> +    infofile->discard = s->has_discard;
> +    infofile->write_zero = s->has_write_zeroes;
> +    infofile->has_discard_zero = s->has_discard;
> +    infofile->discard_zero = s->discard_zeroes;
> +
> +    return info;
> +}
> +
>   static int check_for_dasd(int fd)
>   {
>   #ifdef BIODASDINFO2
> @@ -2765,6 +2782,7 @@ BlockDriver bdrv_file = {
>       .bdrv_co_copy_range_from = raw_co_copy_range_from,
>       .bdrv_co_copy_range_to  = raw_co_copy_range_to,
>       .bdrv_refresh_limits = raw_refresh_limits,
> +    .bdrv_get_specific_info = raw_get_specific_info,
>       .bdrv_io_plug = raw_aio_plug,
>       .bdrv_io_unplug = raw_aio_unplug,
>       .bdrv_attach_aio_context = raw_aio_attach_aio_context,
> @@ -3240,6 +3258,7 @@ static BlockDriver bdrv_host_device = {
>       .bdrv_co_copy_range_from = raw_co_copy_range_from,
>       .bdrv_co_copy_range_to  = raw_co_copy_range_to,
>       .bdrv_refresh_limits = raw_refresh_limits,
> +    .bdrv_get_specific_info = raw_get_specific_info,
>       .bdrv_io_plug = raw_aio_plug,
>       .bdrv_io_unplug = raw_aio_unplug,
>       .bdrv_attach_aio_context = raw_aio_attach_aio_context,
> @@ -3363,6 +3382,7 @@ static BlockDriver bdrv_host_cdrom = {
>       .bdrv_co_pwritev        = raw_co_pwritev,
>       .bdrv_co_flush_to_disk  = raw_co_flush_to_disk,
>       .bdrv_refresh_limits = raw_refresh_limits,
> +    .bdrv_get_specific_info = raw_get_specific_info,
>       .bdrv_io_plug = raw_aio_plug,
>       .bdrv_io_unplug = raw_aio_unplug,
>       .bdrv_attach_aio_context = raw_aio_attach_aio_context,
> @@ -3494,6 +3514,7 @@ static BlockDriver bdrv_host_cdrom = {
>       .bdrv_co_pwritev        = raw_co_pwritev,
>       .bdrv_co_flush_to_disk  = raw_co_flush_to_disk,
>       .bdrv_refresh_limits = raw_refresh_limits,
> +    .bdrv_get_specific_info = raw_get_specific_info,
>       .bdrv_io_plug = raw_aio_plug,
>       .bdrv_io_unplug = raw_aio_unplug,
>       .bdrv_attach_aio_context = raw_aio_attach_aio_context,
> 


-- 
Best regards,
Vladimir