Date: Fri, 13 Sep 2013 16:40:53 +0100
From: Andy Whitcroft <apw@canonical.com>
To: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Ben Howard <ben.howard@canonical.com>, linux-scsi@vger.kernel.org,
        devel@linuxdriverproject.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/4] Hyper-V TRIM support
Message-ID: <20130913154053.GS5382@dm>
References: <1379077109-29606-1-git-send-email-apw@canonical.com>
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On Fri, Sep 13, 2013 at 07:57:58AM -0700, James Bottomley wrote:

> This is an awful lot of contortions (which don't seem to have any other
> users on the horizon) to support a device that's not standards
> compliant.  What about this, it's simple, it does the right thing and
> it's contained in the driver of the problem device.
> 
> James
> 
> ---
> 
> diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
> index 83ec1aa..bd86a4b 100644
> --- a/drivers/scsi/storvsc_drv.c
> +++ b/drivers/scsi/storvsc_drv.c
> @@ -1438,6 +1438,12 @@ static int storvsc_device_configure(struct scsi_device *sdevice)
>  
>  	sdevice->no_write_same = 1;
>  
> +	/*
> +	 * hyper-v is stupid and lies about its capabilities
> +	 * If we pretend to be SPC-3, we send RC16 which activates trim
> +	 */
> +	sdevice->scsi_level = SCSI_SPC_3;
> +
>  	return 0;
>  }

I will get that tested and see if there are any other negative side effects.

-apw
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