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SubjectRe: [PATCH] scsi: virtio_scsi: unplug LUNs when events missed
On Tue, Sep 03, 2019 at 05:04:20PM +0000, Matt Lupfer wrote:
> The event handler calls scsi_scan_host() when events are missed, which
> will hotplug new LUNs. However, this function won't remove any
> unplugged LUNs. The result is that hotunplug doesn't work properly when
> the number of unplugged LUNs exceeds the event queue size (currently 8).
>
> Scan existing LUNs when events are missed to check if they are still
> present. If not, remove them.
>
> Signed-off-by: Matt Lupfer <mlupfer@ddn.com>
> ---
> drivers/scsi/virtio_scsi.c | 31 +++++++++++++++++++++++++++++++
> 1 file changed, 31 insertions(+)
>
> diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
> index 297e1076e571..18df77bf371b 100644
> --- a/drivers/scsi/virtio_scsi.c
> +++ b/drivers/scsi/virtio_scsi.c
> @@ -324,6 +324,36 @@ static void virtscsi_handle_param_change(struct virtio_scsi *vscsi,
> scsi_device_put(sdev);
> }
>
> +static void virtscsi_rescan_hotunplug(struct virtio_scsi *vscsi)
> +{
> + struct scsi_device *sdev;
> + struct Scsi_Host *shost = virtio_scsi_host(vscsi->vdev);
> + unsigned char scsi_cmd[MAX_COMMAND_SIZE];
> + int result, inquiry_len, inq_result_len = 256;
> + char *inq_result = kmalloc(inq_result_len, GFP_KERNEL);
> +
> + shost_for_each_device(sdev, shost) {
> + inquiry_len = sdev->inquiry_len ? sdev->inquiry_len : 36;
> +
> + memset(scsi_cmd, 0, sizeof(scsi_cmd));
> + scsi_cmd[0] = INQUIRY;
> + scsi_cmd[4] = (unsigned char) inquiry_len;
> +
> + memset(inq_result, 0, inq_result_len);
> +
> + result = scsi_execute_req(sdev, scsi_cmd, DMA_FROM_DEVICE,
> + inq_result, inquiry_len, NULL,
> + 2, 3, NULL);


Where do the weird 2 and 3 values come from?

Most callers seem to use SD_TIMEOUT, SD_MAX_RETRIES...

> +
> + if (result == 0 && inq_result[0] >> 5) {
> + /* PQ indicates the LUN is not attached */
> + scsi_remove_device(sdev);
> + }
> + }
> +
> + kfree(inq_result);
> +}
> +
> static void virtscsi_handle_event(struct work_struct *work)
> {
> struct virtio_scsi_event_node *event_node =
> @@ -335,6 +365,7 @@ static void virtscsi_handle_event(struct work_struct *work)
> cpu_to_virtio32(vscsi->vdev, VIRTIO_SCSI_T_EVENTS_MISSED)) {
> event->event &= ~cpu_to_virtio32(vscsi->vdev,
> VIRTIO_SCSI_T_EVENTS_MISSED);
> + virtscsi_rescan_hotunplug(vscsi);
> scsi_scan_host(virtio_scsi_host(vscsi->vdev));
> }
>
> --
> 2.23.0

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