On 08/28/2012 01:54 PM, Paolo Bonzini wrote:
> We will place the request virtqueues in the flexible array member.
>
> Refining the virtqueue API would let us drop the sglist copy, at
> which point the pointer-to-array-of-pointers can become a simple
> pointer-to-array. It would both simplify the allocation and remove a
> dereference in several hot paths.
>
> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
> ---
> drivers/scsi/virtio_scsi.c | 23 +++++++++++++++--------
> 1 files changed, 15 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
> index 595af1a..62fec04 100644
> --- a/drivers/scsi/virtio_scsi.c
> +++ b/drivers/scsi/virtio_scsi.c
> @@ -77,7 +77,7 @@ struct virtio_scsi {
> /* Get some buffers ready for event vq */
> struct virtio_scsi_event_node event_list[VIRTIO_SCSI_EVENT_LEN];
>
> - struct virtio_scsi_target_state *tgt[];
> + struct virtio_scsi_target_state **tgt;
> };
>
> static struct kmem_cache *virtscsi_cmd_cache;
> @@ -615,10 +615,13 @@ static void virtscsi_remove_vqs(struct virtio_device
> *vdev)
> /* Stop all the virtqueues. */
> vdev->config->reset(vdev);
>
> - num_targets = sh->max_id;
> - for (i = 0; i < num_targets; i++) {
> - kfree(vscsi->tgt[i]);
> - vscsi->tgt[i] = NULL;
> + if (vscsi->tgt) {
> + num_targets = sh->max_id;
> + for (i = 0; i < num_targets; i++) {
> + kfree(vscsi->tgt[i]);
Since we now kmalloc() the vscsi->tgt array, it doesn't get zeroed anymore.
This means that if for example, num_targets=3, and the second
virtscsi_alloc_tgt() in virtscsi_init() failed, we're going to kfree() garbage
here.
Thanks,
Sasha
> + vscsi->tgt[i] = NULL;
> + }
> + kfree(vscsi->tgt);
> }
> vdev->config->del_vqs(vdev);
> @@ -660,6 +663,12 @@ static int virtscsi_init(struct virtio_device *vdev,
> /* We need to know how many segments before we allocate. */
> sg_elems = virtscsi_config_get(vdev, seg_max) ?: 1;
>
> + vscsi->tgt = kmalloc(num_targets *
> + sizeof(struct virtio_scsi_target_state *), GFP_KERNEL);
> + if (!vscsi->tgt) {
> + err = -ENOMEM;
> + goto out;
> + }
> for (i = 0; i < num_targets; i++) {
> vscsi->tgt[i] = virtscsi_alloc_tgt(vdev, sg_elems);
> if (!vscsi->tgt[i]) {
> @@ -685,9 +694,7 @@ static int __devinit virtscsi_probe(struct virtio_device
> *vdev)
>
> /* Allocate memory and link the structs together. */
> num_targets = virtscsi_config_get(vdev, max_target) + 1;
> - shost = scsi_host_alloc(&virtscsi_host_template,
> - sizeof(*vscsi)
> - + num_targets * sizeof(struct virtio_scsi_target_state));
> + shost = scsi_host_alloc(&virtscsi_host_template, sizeof(*vscsi));
>
> if (!shost)
> return -ENOMEM;
>
--
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