Re: [PATCH v3] virtio-blk: Respect discard granularity

[Michael S. Tsirkin]

On Tue, Feb 23, 2021 at 09:09:40PM +0900, Akihiko Odaki wrote:
> Signed-off-by: Akihiko Odaki <akihiko.odaki@gmail.com>


Acked-by: Michael S. Tsirkin <mst@redhat.com>


whoever knows more about the detail here, feel free to merge.

> ---
>  hw/block/virtio-blk.c          | 8 +++++++-
>  hw/core/machine.c              | 4 +++-
>  include/hw/virtio/virtio-blk.h | 1 +
>  3 files changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
> index bac2d6fa2b2..f4378e61182 100644
> --- a/hw/block/virtio-blk.c
> +++ b/hw/block/virtio-blk.c
> @@ -962,10 +962,14 @@ static void virtio_blk_update_config(VirtIODevice 
> *vdev, uint8_t *config)
>      blkcfg.wce = blk_enable_write_cache(s->blk);
>      virtio_stw_p(vdev, &blkcfg.num_queues, s->conf.num_queues);
>      if (virtio_has_feature(s->host_features, VIRTIO_BLK_F_DISCARD)) {
> +        uint32_t discard_granularity = conf->discard_granularity;
> +        if (discard_granularity == -1 || 
> !s->conf.report_discard_granularity) {
> +            discard_granularity = blk_size;
> +        }
>          virtio_stl_p(vdev, &blkcfg.max_discard_sectors,
>                       s->conf.max_discard_sectors);
>          virtio_stl_p(vdev, &blkcfg.discard_sector_alignment,
> -                     blk_size >> BDRV_SECTOR_BITS);
> +                     discard_granularity >> BDRV_SECTOR_BITS);
>          /*
>           * We support only one segment per request since multiple segments
>           * are not widely used and there are no userspace APIs that allow
> @@ -1299,6 +1303,8 @@ static Property virtio_blk_properties[] = {
>                       IOThread *),
>      DEFINE_PROP_BIT64("discard", VirtIOBlock, host_features,
>                        VIRTIO_BLK_F_DISCARD, true),
> +    DEFINE_PROP_BOOL("report-discard-granularity", VirtIOBlock,
> +                     conf.report_discard_granularity, true),
>      DEFINE_PROP_BIT64("write-zeroes", VirtIOBlock, host_features,
>                        VIRTIO_BLK_F_WRITE_ZEROES, true),
>      DEFINE_PROP_UINT32("max-discard-sectors", VirtIOBlock,
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index de3b8f1b318..e4df5797e72 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -33,7 +33,9 @@
>  #include "migration/global_state.h"
>  #include "migration/vmstate.h"
>  
> -GlobalProperty hw_compat_5_2[] = {};
> +GlobalProperty hw_compat_5_2[] = {
> +    { "virtio-blk-device", "report-discard-granularity", "off" },
> +};
>  const size_t hw_compat_5_2_len = G_N_ELEMENTS(hw_compat_5_2);
>  
>  GlobalProperty hw_compat_5_1[] = {
> diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h
> index 214ab748229..29655a406dd 100644
> --- a/include/hw/virtio/virtio-blk.h
> +++ b/include/hw/virtio/virtio-blk.h
> @@ -41,6 +41,7 @@ struct VirtIOBlkConf
>      uint16_t num_queues;
>      uint16_t queue_size;
>      bool seg_max_adjust;
> +    bool report_discard_granularity;
>      uint32_t max_discard_sectors;
>      uint32_t max_write_zeroes_sectors;
>      bool x_enable_wce_if_config_wce;
> -- 
> 2.24.3 (Apple Git-128)