On 06/18/2012 06:21 PM, Michael S. Tsirkin wrote:

On Mon, Jun 18, 2012 at 02:53:10PM +0800, Asias He wrote:

quoted

+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?

quoted

+		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.

quoted

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

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-- 
Asias