Re: [PATCH] virtio-blk: remove VIRTIO_BLK_F_SCSI support

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Dec 12, 2019 at 05:37:19PM +0100, Christoph Hellwig wrote:
> Since the need for a special flag to support SCSI passthrough on a
> block device was added in May 2017 the SCSI passthrough support in
> virtio-blk has been disabled.  It has always been a bad idea
> (just ask the original author..) and we have virtio-scsi for proper
> passthrough.  The feature also never made it into the virtio 1.0
> or later specifications.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

OK but I'd rather not make such changes with merge window closed.
I'll queue this for next window.

> ---
>  arch/powerpc/configs/guest.config |   1 -
>  drivers/block/Kconfig             |  10 ---
>  drivers/block/virtio_blk.c        | 115 +-----------------------------
>  3 files changed, 1 insertion(+), 125 deletions(-)
> 
> diff --git a/arch/powerpc/configs/guest.config b/arch/powerpc/configs/guest.config
> index 8b8cd18ecd7c..209f58515d88 100644
> --- a/arch/powerpc/configs/guest.config
> +++ b/arch/powerpc/configs/guest.config
> @@ -1,5 +1,4 @@
>  CONFIG_VIRTIO_BLK=y
> -CONFIG_VIRTIO_BLK_SCSI=y
>  CONFIG_SCSI_VIRTIO=y
>  CONFIG_VIRTIO_NET=y
>  CONFIG_NET_FAILOVER=y
> diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
> index 1bb8ec575352..025b1b77b11a 100644
> --- a/drivers/block/Kconfig
> +++ b/drivers/block/Kconfig
> @@ -432,16 +432,6 @@ config VIRTIO_BLK
>  	  This is the virtual block driver for virtio.  It can be used with
>            QEMU based VMMs (like KVM or Xen).  Say Y or M.
>  
> -config VIRTIO_BLK_SCSI
> -	bool "SCSI passthrough request for the Virtio block driver"
> -	depends on VIRTIO_BLK
> -	select BLK_SCSI_REQUEST
> -	---help---
> -	  Enable support for SCSI passthrough (e.g. the SG_IO ioctl) on
> -	  virtio-blk devices.  This is only supported for the legacy
> -	  virtio protocol and not enabled by default by any hypervisor.
> -	  You probably want to use virtio-scsi instead.
> -
>  config BLK_DEV_RBD
>  	tristate "Rados block device (RBD)"
>  	depends on INET && BLOCK
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 7ffd719d89de..54158766334b 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -11,7 +11,6 @@
>  #include <linux/virtio_blk.h>
>  #include <linux/scatterlist.h>
>  #include <linux/string_helpers.h>
> -#include <scsi/scsi_cmnd.h>
>  #include <linux/idr.h>
>  #include <linux/blk-mq.h>
>  #include <linux/blk-mq-virtio.h>
> @@ -56,11 +55,6 @@ struct virtio_blk {
>  };
>  
>  struct virtblk_req {
> -#ifdef CONFIG_VIRTIO_BLK_SCSI
> -	struct scsi_request sreq;	/* for SCSI passthrough, must be first */
> -	u8 sense[SCSI_SENSE_BUFFERSIZE];
> -	struct virtio_scsi_inhdr in_hdr;
> -#endif
>  	struct virtio_blk_outhdr out_hdr;
>  	u8 status;
>  	struct scatterlist sg[];
> @@ -78,80 +72,6 @@ static inline blk_status_t virtblk_result(struct virtblk_req *vbr)
>  	}
>  }
>  
> -/*
> - * If this is a packet command we need a couple of additional headers.  Behind
> - * the normal outhdr we put a segment with the scsi command block, and before
> - * the normal inhdr we put the sense data and the inhdr with additional status
> - * information.
> - */
> -#ifdef CONFIG_VIRTIO_BLK_SCSI
> -static int virtblk_add_req_scsi(struct virtqueue *vq, struct virtblk_req *vbr,
> -		struct scatterlist *data_sg, bool have_data)
> -{
> -	struct scatterlist hdr, status, cmd, sense, inhdr, *sgs[6];
> -	unsigned int num_out = 0, num_in = 0;
> -
> -	sg_init_one(&hdr, &vbr->out_hdr, sizeof(vbr->out_hdr));
> -	sgs[num_out++] = &hdr;
> -	sg_init_one(&cmd, vbr->sreq.cmd, vbr->sreq.cmd_len);
> -	sgs[num_out++] = &cmd;
> -
> -	if (have_data) {
> -		if (vbr->out_hdr.type & cpu_to_virtio32(vq->vdev, VIRTIO_BLK_T_OUT))
> -			sgs[num_out++] = data_sg;
> -		else
> -			sgs[num_out + num_in++] = data_sg;
> -	}
> -
> -	sg_init_one(&sense, vbr->sense, SCSI_SENSE_BUFFERSIZE);
> -	sgs[num_out + num_in++] = &sense;
> -	sg_init_one(&inhdr, &vbr->in_hdr, sizeof(vbr->in_hdr));
> -	sgs[num_out + num_in++] = &inhdr;
> -	sg_init_one(&status, &vbr->status, sizeof(vbr->status));
> -	sgs[num_out + num_in++] = &status;
> -
> -	return virtqueue_add_sgs(vq, sgs, num_out, num_in, vbr, GFP_ATOMIC);
> -}
> -
> -static inline void virtblk_scsi_request_done(struct request *req)
> -{
> -	struct virtblk_req *vbr = blk_mq_rq_to_pdu(req);
> -	struct virtio_blk *vblk = req->q->queuedata;
> -	struct scsi_request *sreq = &vbr->sreq;
> -
> -	sreq->resid_len = virtio32_to_cpu(vblk->vdev, vbr->in_hdr.residual);
> -	sreq->sense_len = virtio32_to_cpu(vblk->vdev, vbr->in_hdr.sense_len);
> -	sreq->result = virtio32_to_cpu(vblk->vdev, vbr->in_hdr.errors);
> -}
> -
> -static int virtblk_ioctl(struct block_device *bdev, fmode_t mode,
> -			     unsigned int cmd, unsigned long data)
> -{
> -	struct gendisk *disk = bdev->bd_disk;
> -	struct virtio_blk *vblk = disk->private_data;
> -
> -	/*
> -	 * Only allow the generic SCSI ioctls if the host can support it.
> -	 */
> -	if (!virtio_has_feature(vblk->vdev, VIRTIO_BLK_F_SCSI))
> -		return -ENOTTY;
> -
> -	return scsi_cmd_blk_ioctl(bdev, mode, cmd,
> -				  (void __user *)data);
> -}
> -#else
> -static inline int virtblk_add_req_scsi(struct virtqueue *vq,
> -		struct virtblk_req *vbr, struct scatterlist *data_sg,
> -		bool have_data)
> -{
> -	return -EIO;
> -}
> -static inline void virtblk_scsi_request_done(struct request *req)
> -{
> -}
> -#define virtblk_ioctl	NULL
> -#endif /* CONFIG_VIRTIO_BLK_SCSI */
> -
>  static int virtblk_add_req(struct virtqueue *vq, struct virtblk_req *vbr,
>  		struct scatterlist *data_sg, bool have_data)
>  {
> @@ -216,13 +136,6 @@ static inline void virtblk_request_done(struct request *req)
>  		      req->special_vec.bv_offset);
>  	}
>  
> -	switch (req_op(req)) {
> -	case REQ_OP_SCSI_IN:
> -	case REQ_OP_SCSI_OUT:
> -		virtblk_scsi_request_done(req);
> -		break;
> -	}
> -
>  	blk_mq_end_request(req, virtblk_result(vbr));
>  }
>  
> @@ -299,10 +212,6 @@ static blk_status_t virtio_queue_rq(struct blk_mq_hw_ctx *hctx,
>  		type = VIRTIO_BLK_T_WRITE_ZEROES;
>  		unmap = !(req->cmd_flags & REQ_NOUNMAP);
>  		break;
> -	case REQ_OP_SCSI_IN:
> -	case REQ_OP_SCSI_OUT:
> -		type = VIRTIO_BLK_T_SCSI_CMD;
> -		break;
>  	case REQ_OP_DRV_IN:
>  		type = VIRTIO_BLK_T_GET_ID;
>  		break;
> @@ -333,10 +242,7 @@ static blk_status_t virtio_queue_rq(struct blk_mq_hw_ctx *hctx,
>  	}
>  
>  	spin_lock_irqsave(&vblk->vqs[qid].lock, flags);
> -	if (blk_rq_is_scsi(req))
> -		err = virtblk_add_req_scsi(vblk->vqs[qid].vq, vbr, vbr->sg, num);
> -	else
> -		err = virtblk_add_req(vblk->vqs[qid].vq, vbr, vbr->sg, num);
> +	err = virtblk_add_req(vblk->vqs[qid].vq, vbr, vbr->sg, num);
>  	if (err) {
>  		virtqueue_kick(vblk->vqs[qid].vq);
>  		blk_mq_stop_hw_queue(hctx);
> @@ -404,7 +310,6 @@ static int virtblk_getgeo(struct block_device *bd, struct hd_geometry *geo)
>  }
>  
>  static const struct block_device_operations virtblk_fops = {
> -	.ioctl  = virtblk_ioctl,
>  	.owner  = THIS_MODULE,
>  	.getgeo = virtblk_getgeo,
>  };
> @@ -683,9 +588,6 @@ static int virtblk_init_request(struct blk_mq_tag_set *set, struct request *rq,
>  	struct virtio_blk *vblk = set->driver_data;
>  	struct virtblk_req *vbr = blk_mq_rq_to_pdu(rq);
>  
> -#ifdef CONFIG_VIRTIO_BLK_SCSI
> -	vbr->sreq.sense = vbr->sense;
> -#endif
>  	sg_init_table(vbr->sg, vblk->sg_elems);
>  	return 0;
>  }
> @@ -698,23 +600,11 @@ static int virtblk_map_queues(struct blk_mq_tag_set *set)
>  					vblk->vdev, 0);
>  }
>  
> -#ifdef CONFIG_VIRTIO_BLK_SCSI
> -static void virtblk_initialize_rq(struct request *req)
> -{
> -	struct virtblk_req *vbr = blk_mq_rq_to_pdu(req);
> -
> -	scsi_req_init(&vbr->sreq);
> -}
> -#endif
> -
>  static const struct blk_mq_ops virtio_mq_ops = {
>  	.queue_rq	= virtio_queue_rq,
>  	.commit_rqs	= virtio_commit_rqs,
>  	.complete	= virtblk_request_done,
>  	.init_request	= virtblk_init_request,
> -#ifdef CONFIG_VIRTIO_BLK_SCSI
> -	.initialize_rq_fn = virtblk_initialize_rq,
> -#endif
>  	.map_queues	= virtblk_map_queues,
>  };
>  
> @@ -991,9 +881,6 @@ 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,
> -#ifdef CONFIG_VIRTIO_BLK_SCSI
> -	VIRTIO_BLK_F_SCSI,
> -#endif
>  	VIRTIO_BLK_F_FLUSH, VIRTIO_BLK_F_TOPOLOGY, VIRTIO_BLK_F_CONFIG_WCE,
>  	VIRTIO_BLK_F_MQ, VIRTIO_BLK_F_DISCARD, VIRTIO_BLK_F_WRITE_ZEROES,
>  }
> -- 
> 2.20.1