linux-kernel - Re: [PATCH] virtio_blk: VIRTIO_BLK_F_WCE->VIRTIO_BLK_F

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Date:	Wed, 24 Feb 2016 16:16:51 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>, linux-kernel@...r.kernel.org
Cc:	virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH] virtio_blk: VIRTIO_BLK_F_WCE->VIRTIO_BLK_F_FLUSH



On 24/02/2016 16:11, Michael S. Tsirkin wrote:
> Latest virtio spec says the feature bit name is VIRTIO_BLK_F_FLUSH,
> VIRTIO_BLK_F_WCE is the legacy name.  virtio blk header says exactly the
> reverse - fix that and update driver code to match.
> 
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> ---
> I'm inclined to merge it for the current kernel -
> safe and avoids confusion.

Since you are at it, also change this:

> +#define VIRTIO_BLK_F_FLUSH	9	/* Writeback mode enabled after reset */

to /* Flush command supported */

>  #define VIRTIO_BLK_F_CONFIG_WCE	11	/* Writeback mode available in config */
>  #ifndef __KERNEL__
> -/* Old (deprecated) name for VIRTIO_BLK_F_WCE. */
> -#define VIRTIO_BLK_F_FLUSH VIRTIO_BLK_F_WCE
> +/* Old (deprecated) name for VIRTIO_BLK_F_FLUSH. */
> +#define VIRTIO_BLK_F_WCE VIRTIO_BLK_F_FLUSH
>  #endif
>  #endif /* !VIRTIO_BLK_NO_LEGACY */
>  
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 6ca3549..dbaebb0 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -478,7 +478,7 @@ static int virtblk_get_cache_mode(struct virtio_device *vdev)
>  				   struct virtio_blk_config, wce,
>  				   &writeback);

and add a comment here:

/*
 * If WCE is not configurable and flush is not available,
 * assume no writeback cache is in use.
 */

>  	if (err)
> -		writeback = virtio_has_feature(vdev, VIRTIO_BLK_F_WCE);
> +		writeback = virtio_has_feature(vdev, VIRTIO_BLK_F_FLUSH);
>  
>  	return writeback;
>  }
> @@ -833,14 +833,14 @@ static const struct virtio_device_id id_table[] = {
>  static unsigned int features_legacy[] = {
>  	VIRTIO_BLK_F_SEG_MAX, VIRTIO_BLK_F_SIZE_MAX, VIRTIO_BLK_F_GEOMETRY,
>  	VIRTIO_BLK_F_RO, VIRTIO_BLK_F_BLK_SIZE, VIRTIO_BLK_F_SCSI,
> -	VIRTIO_BLK_F_WCE, VIRTIO_BLK_F_TOPOLOGY, VIRTIO_BLK_F_CONFIG_WCE,
> +	VIRTIO_BLK_F_FLUSH, VIRTIO_BLK_F_TOPOLOGY, VIRTIO_BLK_F_CONFIG_WCE,
>  	VIRTIO_BLK_F_MQ,
>  }
>  ;
>  static unsigned int features[] = {
>  	VIRTIO_BLK_F_SEG_MAX, VIRTIO_BLK_F_SIZE_MAX, VIRTIO_BLK_F_GEOMETRY,
>  	VIRTIO_BLK_F_RO, VIRTIO_BLK_F_BLK_SIZE,
> -	VIRTIO_BLK_F_WCE, VIRTIO_BLK_F_TOPOLOGY, VIRTIO_BLK_F_CONFIG_WCE,
> +	VIRTIO_BLK_F_FLUSH, VIRTIO_BLK_F_TOPOLOGY, VIRTIO_BLK_F_CONFIG_WCE,
>  	VIRTIO_BLK_F_MQ,
>  };
>  
>