virtio_blk: Drop unused request tracking list

commit f65ca1dc6a8c81c6bd72297d4399ec5f4c1f3a01 upstream.

Benchmark shows small performance improvement on fusion io device.

Before:
  seq-read : io=1,024MB, bw=19,982KB/s, iops=39,964, runt= 52475msec
  seq-write: io=1,024MB, bw=20,321KB/s, iops=40,641, runt= 51601msec
  rnd-read : io=1,024MB, bw=15,404KB/s, iops=30,808, runt= 68070msec
  rnd-write: io=1,024MB, bw=14,776KB/s, iops=29,552, runt= 70963msec

After:
  seq-read : io=1,024MB, bw=20,343KB/s, iops=40,685, runt= 51546msec
  seq-write: io=1,024MB, bw=20,803KB/s, iops=41,606, runt= 50404msec
  rnd-read : io=1,024MB, bw=16,221KB/s, iops=32,442, runt= 64642msec
  rnd-write: io=1,024MB, bw=15,199KB/s, iops=30,397, runt= 68991msec

Signed-off-by: Asias He <asias@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index b672b9faab31d4971e6bc433e6d411c5ce2989f4..108ebb43ed5141d94539c528c289e61027e92cae 100644 (file)
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -27,9 +27,6 @@ struct virtio_blk
        /* The disk structure for the kernel. */
        struct gendisk *disk;
 
-       /* Request tracking. */
-       struct list_head reqs;
-
        mempool_t *pool;
 
        /* Process context for config space updates */
@@ -53,7 +50,6 @@ struct virtio_blk
 
 struct virtblk_req
 {
-       struct list_head list;
        struct request *req;
        struct virtio_blk_outhdr out_hdr;
        struct virtio_scsi_inhdr in_hdr;
@@ -97,7 +93,6 @@ static void blk_done(struct virtqueue *vq)
                }
 
                __blk_end_request_all(vbr->req, error);
-               list_del(&vbr->list);
                mempool_free(vbr, vblk->pool);
        }
        /* In case queue is stopped waiting for more buffers. */
@@ -182,7 +177,6 @@ static bool do_req(struct request_queue *q, struct virtio_blk *vblk,
                return false;
        }
 
-       list_add_tail(&vbr->list, &vblk->reqs);
        return true;
 }
 
@@ -394,7 +388,6 @@ static int __devinit virtblk_probe(struct virtio_device *vdev)
                goto out_free_index;
        }
 
-       INIT_LIST_HEAD(&vblk->reqs);
        vblk->vdev = vdev;
        vblk->sg_elems = sg_elems;
        sg_init_table(vblk->sg, vblk->sg_elems);
@@ -559,9 +552,6 @@ static void __devexit virtblk_remove(struct virtio_device *vdev)
        vblk->config_enable = false;
        mutex_unlock(&vblk->config_lock);
 
-       /* Nothing should be pending. */
-       BUG_ON(!list_empty(&vblk->reqs));
-
        /* Stop all the virtqueues. */
        vdev->config->reset(vdev);