Re: [PATCH] sd: always scan VPD pages if thin provisioning is enabled

[Christoph Hellwig <hch@lst.de>]

On Wed, Jan 25, 2017 at 08:26:05AM +0100, Hannes Reinecke wrote:
> For any device with an older SCSI revision we might not
> be scanning VPD pages, which results in a wrongly configured
> discard mode if thin provisioned is enabled.
> According to sbc3 any thin provisioned device (ie devices which
> have the LBPME bit set in the output of READ CAPACITY(16)) need
> to support VPD pages. So this patch always enables VPD pages
> even for older SCSI revisions if thin provisioning is enabled.

Can you explain what you need this for?  A device with a per-SBC3
revision that wants us to use UNMAP?

> +		/*
> +		 * sbc3r36 states:
> +		 * The device server in a logical unit the supports
> +		 * logical block provisioning management shall support
> +		 * the Logical Block Provisioning VPD page.
> +		 * So VPD pages should be supported if lbpme is set.
> +		 */

It's a bit odd to quote SBC3 when the device clearly is pre-SBC3
to need this workaround..

> +		if (!scsi_device_supports_vpd(sdp))
> +			sdp->try_vpd_pages = 1;

Do the assignment unconditionally?