virtio_blk: SG_IO passthru support

Add support for SG_IO passthru to virtio_blk.  We add the scsi command
block after the normal outhdr, and the scsi inhdr with full status
information aswell as the sense buffer before the regular inhdr.

[hch: forward ported, added the VIRTIO_BLK_F_SCSI flags, some comments
 and tested the whole beast]
[axboe: updated to use ->resid and not dual-path the byte count]

Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (+ checkpatch.pl tweak)
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 50 insertions, 14 deletions

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index dfe9ee5f1696..62275dbdf2eb 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -37,6 +37,7 @@ struct virtblk_req
         struct list_head list;
         struct request *req;
         struct virtio_blk_outhdr out_hdr;
+        struct virtio_scsi_inhdr in_hdr;
         u8 status;
 };
 
@@ -49,7 +50,9 @@ static void blk_done(struct virtqueue *vq)
 
         spin_lock_irqsave(&vblk->lock, flags);
         while ((vbr = vblk->vq->vq_ops->get_buf(vblk->vq, &len)) != NULL) {
+                unsigned int nr_bytes;
                 int error;
+
                 switch (vbr->status) {
                 case VIRTIO_BLK_S_OK:
                         error = 0;
@@ -62,6 +65,12 @@ static void blk_done(struct virtqueue *vq)
                         break;
                 }
 
+                if (blk_pc_request(vbr->req)) {
+                        vbr->req->resid_len = vbr->in_hdr.residual;
+                        vbr->req->sense_len = vbr->in_hdr.sense_len;
+                        vbr->req->errors = vbr->in_hdr.errors;
+                }
+
                 __blk_end_request_all(vbr->req, error);
                 list_del(&vbr->list);
                 mempool_free(vbr, vblk->pool);
@@ -74,7 +83,7 @@ static void blk_done(struct virtqueue *vq)
 static bool do_req(struct request_queue *q, struct virtio_blk *vblk,
                    struct request *req)
 {
-        unsigned long num, out, in;
+        unsigned long num, out = 0, in = 0;
         struct virtblk_req *vbr;
 
         vbr = mempool_alloc(vblk->pool, GFP_ATOMIC);
@@ -99,18 +108,36 @@ static bool do_req(struct request_queue *q, struct virtio_blk *vblk,
         if (blk_barrier_rq(vbr->req))
                 vbr->out_hdr.type |= VIRTIO_BLK_T_BARRIER;
 
-        sg_set_buf(&vblk->sg[0], &vbr->out_hdr, sizeof(vbr->out_hdr));
-        num = blk_rq_map_sg(q, vbr->req, vblk->sg+1);
-        sg_set_buf(&vblk->sg[num+1], &vbr->status, sizeof(vbr->status));
+        sg_set_buf(&vblk->sg[out++], &vbr->out_hdr, sizeof(vbr->out_hdr));
 
-        if (rq_data_dir(vbr->req) == WRITE) {
-                vbr->out_hdr.type |= VIRTIO_BLK_T_OUT;
-                out = 1 + num;
-                in = 1;
-        } else {
-                vbr->out_hdr.type |= VIRTIO_BLK_T_IN;
-                out = 1;
-                in = 1 + num;
+        /*
+         * 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 before the normal inhdr.
+         */
+        if (blk_pc_request(vbr->req))
+                sg_set_buf(&vblk->sg[out++], vbr->req->cmd, vbr->req->cmd_len);
+
+        num = blk_rq_map_sg(q, vbr->req, vblk->sg + out);
+
+        if (blk_pc_request(vbr->req)) {
+                sg_set_buf(&vblk->sg[num + out + in++], vbr->req->sense, 96);
+                sg_set_buf(&vblk->sg[num + out + in++], &vbr->in_hdr,
+                           sizeof(vbr->in_hdr));
+        }
+
+        sg_set_buf(&vblk->sg[num + out + in++], &vbr->status,
+                   sizeof(vbr->status));
+
+        if (num) {
+                if (rq_data_dir(vbr->req) == WRITE) {
+                        vbr->out_hdr.type |= VIRTIO_BLK_T_OUT;
+                        out += num;
+                } else {
+                        vbr->out_hdr.type |= VIRTIO_BLK_T_IN;
+                        in += num;
+                }
         }
 
         if (vblk->vq->vq_ops->add_buf(vblk->vq, vblk->sg, out, in, vbr)) {
@@ -148,8 +175,16 @@ static void do_virtblk_request(struct request_queue *q)
 static int virtblk_ioctl(struct block_device *bdev, fmode_t mode,
                          unsigned cmd, unsigned long data)
 {
-        return scsi_cmd_ioctl(bdev->bd_disk->queue,
-                              bdev->bd_disk, mode, cmd,
+        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 -ENOIOCTLCMD;
+
+        return scsi_cmd_ioctl(disk->queue, disk, mode, cmd,
                               (void __user *)data);
 }
 
@@ -356,6 +391,7 @@ static struct virtio_device_id id_table[] = {
 static unsigned int features[] = {
         VIRTIO_BLK_F_BARRIER, 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,
 };
 
 static struct virtio_driver virtio_blk = {