virtio-blk: use virtqueue_add_sgs on req path

(This is a respin of Paolo Bonzini's patch, but it calls
virtqueue_add_sgs() instead of his multi-part API).

This is similar to the previous patch, but a bit more radical
because the bio and req paths now share the buffer construction
code.  Because the req path doesn't use vbr->sg, however, we
need to add a couple of arguments to __virtblk_add_req.

We also need to teach __virtblk_add_req how to build SCSI command
requests.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Reviewed-by: Asias He <asias@redhat.com>

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index cfbe39d..cc88b29 100644 (file)
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -102,19 +102,40 @@ static inline struct virtblk_req *virtblk_alloc_req(struct virtio_blk *vblk,
 }
 
 static int __virtblk_add_req(struct virtqueue *vq,
-                            struct virtblk_req *vbr)
+                            struct virtblk_req *vbr,
+                            struct scatterlist *data_sg,
+                            unsigned data_nents)
 {
-       struct scatterlist hdr, status, *sgs[3];
+       struct scatterlist hdr, status, cmd, sense, inhdr, *sgs[6];
        unsigned int num_out = 0, num_in = 0;
+       int type = vbr->out_hdr.type & ~VIRTIO_BLK_T_OUT;
 
        sg_init_one(&hdr, &vbr->out_hdr, sizeof(vbr->out_hdr));
        sgs[num_out++] = &hdr;
 
-       if (vbr->nents) {
+       /*
+        * 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.
+        */
+       if (type == VIRTIO_BLK_T_SCSI_CMD) {
+               sg_init_one(&cmd, vbr->req->cmd, vbr->req->cmd_len);
+               sgs[num_out++] = &cmd;
+       }
+
+       if (data_nents) {
                if (vbr->out_hdr.type & VIRTIO_BLK_T_OUT)
-                       sgs[num_out++] = vbr->sg;
+                       sgs[num_out++] = data_sg;
                else
-                       sgs[num_out + num_in++] = vbr->sg;
+                       sgs[num_out + num_in++] = data_sg;
+       }
+
+       if (type == VIRTIO_BLK_T_SCSI_CMD) {
+               sg_init_one(&sense, vbr->req->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));
@@ -130,7 +151,8 @@ static void virtblk_add_req(struct virtblk_req *vbr)
        int ret;
 
        spin_lock_irq(vblk->disk->queue->queue_lock);
-       while (unlikely((ret = __virtblk_add_req(vblk->vq, vbr)) < 0)) {
+       while (unlikely((ret = __virtblk_add_req(vblk->vq, vbr, vbr->sg,
+                                                vbr->nents)) < 0)) {
                prepare_to_wait_exclusive(&vblk->queue_wait, &wait,
                                          TASK_UNINTERRUPTIBLE);
 
@@ -283,7 +305,7 @@ static void virtblk_done(struct virtqueue *vq)
 static bool do_req(struct request_queue *q, struct virtio_blk *vblk,
                   struct request *req)
 {
-       unsigned long num, out = 0, in = 0;
+       unsigned int num;
        struct virtblk_req *vbr;
 
        vbr = virtblk_alloc_req(vblk, GFP_ATOMIC);
@@ -320,40 +342,15 @@ static bool do_req(struct request_queue *q, struct virtio_blk *vblk,
                }
        }
 
-       sg_set_buf(&vblk->sg[out++], &vbr->out_hdr, sizeof(vbr->out_hdr));
-
-       /*
-        * 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 (vbr->req->cmd_type == REQ_TYPE_BLOCK_PC)
-               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 (vbr->req->cmd_type == REQ_TYPE_BLOCK_PC) {
-               sg_set_buf(&vblk->sg[num + out + in++], vbr->req->sense, SCSI_SENSE_BUFFERSIZE);
-               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));
-
+       num = blk_rq_map_sg(q, vbr->req, vblk->sg);
        if (num) {
-               if (rq_data_dir(vbr->req) == WRITE) {
+               if (rq_data_dir(vbr->req) == WRITE)
                        vbr->out_hdr.type |= VIRTIO_BLK_T_OUT;
-                       out += num;
-               } else {
+               else
                        vbr->out_hdr.type |= VIRTIO_BLK_T_IN;
-                       in += num;
-               }
        }
 
-       if (virtqueue_add_buf(vblk->vq, vblk->sg, out, in, vbr,
-                             GFP_ATOMIC) < 0) {
+       if (__virtblk_add_req(vblk->vq, vbr, vblk->sg, num) < 0) {
                mempool_free(vbr, vblk->pool);
                return false;
        }