On 06/18/2012 06:21 PM, Michael S. Tsirkin wrote:
On Mon, Jun 18, 2012 at 02:53:10PM +0800, Asias He wrote:
+static void virtblk_make_request(struct request_queue *q, struct bio *bio)
+{
+       struct virtio_blk *vblk = q->queuedata;
+       unsigned int num, out = 0, in = 0;
+       struct virtblk_req *vbr;
+
+       BUG_ON(bio->bi_phys_segments + 2 > vblk->sg_elems);
+       BUG_ON(bio->bi_rw & (REQ_FLUSH | REQ_FUA));
+
+       vbr = virtblk_alloc_req(vblk, GFP_NOIO);
+       if (!vbr) {
+               bio_endio(bio, -ENOMEM);
+               return;
+       }
+
+       vbr->bio = bio;
+       vbr->req = NULL;
+       vbr->out_hdr.type = 0;
+       vbr->out_hdr.sector = bio->bi_sector;
+       vbr->out_hdr.ioprio = bio_prio(bio);
+
+       sg_set_buf(&vbr->sg[out++], &vbr->out_hdr, sizeof(vbr->out_hdr));
+
+       num = blk_bio_map_sg(q, bio, vbr->sg + out);
+
+       sg_set_buf(&vbr->sg[num + out + in++], &vbr->status,
+                  sizeof(vbr->status));
+
+       if (num) {
+               if (bio->bi_rw & REQ_WRITE) {
+                       vbr->out_hdr.type |= VIRTIO_BLK_T_OUT;
+                       out += num;
+               } else {
+                       vbr->out_hdr.type |= VIRTIO_BLK_T_IN;
+                       in += num;
+               }
+       }
+
+       spin_lock_irq(vblk->disk->queue->queue_lock);
+       if (virtqueue_add_buf(vblk->vq, vbr->sg, out, in, vbr,
+                             GFP_ATOMIC) < 0) {
+               spin_unlock_irq(vblk->disk->queue->queue_lock);

Any implications of dropping lock like that?
E.g. for suspend. like we are still discussing with
unlocked kick?

+               virtblk_add_buf_wait(vblk, vbr, out, in);
+       } else {
+               virtqueue_kick(vblk->vq);

Why special case the first call? task state manipulation so expensive?

Hmm. Will switch them.


+               spin_unlock_irq(vblk->disk->queue->queue_lock);
+       }
+}
+
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--
Asias


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