Re: [PATCH v2] virtio_blk: add SECURE ERASE command support

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Mon, Aug 29, 2022 at 11:23:13AM +0300, Alvaro Karsz wrote:
> @@ -1075,6 +1068,57 @@ static int virtblk_probe(struct virtio_device *vdev)
>  		blk_queue_max_write_zeroes_sectors(q, v ? v : UINT_MAX);
>  	}
>  
> +	if (virtio_has_feature(vdev, VIRTIO_BLK_F_SECURE_ERASE)) {
> +		/* The discard alignment value should be the minimum between
> +		 * secure_erase_sector_alignment and discard_sector_alignment
> +		 * (if VIRTIO_BLK_F_DISCARD is negotiated).
> +		 */
> +		virtio_cread(vdev, struct virtio_blk_config,
> +			     secure_erase_sector_alignment, &v);
> +		if (v) {
> +			if (discard_granularity)
> +				discard_granularity = min(discard_granularity, v);
> +			else
> +				discard_granularity = v;

This can be simplified with min_not_zero().

> +		}
> +
> +		virtio_cread(vdev, struct virtio_blk_config,
> +			     max_secure_erase_sectors, &v);
> +		blk_queue_max_secure_erase_sectors(q, v ? v : UINT_MAX);
> +
> +		/* The max discard segments value should be the minimum between
> +		 * max_secure_erase_seg and max_discard_seg (if VIRTIO_BLK_F_DISCARD
> +		 * is negotiated).
> +		 */
> +		virtio_cread(vdev, struct virtio_blk_config,
> +			     max_secure_erase_seg, &v);
> +		if (v) {
> +			if (max_discard_segs)
> +				max_discard_segs = min(max_discard_segs, v);
> +			else
> +				max_discard_segs = v;

Same here.

> +		}
> +	}
> +
> +	if (virtio_has_feature(vdev, VIRTIO_BLK_F_DISCARD) ||
> +	    virtio_has_feature(vdev, VIRTIO_BLK_F_SECURE_ERASE)) {

It's worth including a comment here that the discard and secure erase
limits are combined because the Linux block layer only has one limit
value. If the block layer supported independent limit values we wouldn't
need to do this.

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