Re: [PATCH v3] virtio-scsi: hotplug support for virtio-scsi

[Paolo Bonzini <pbonzini@redhat.com>]

Il 05/07/2012 09:09, Cong Meng ha scritto:
> This patch implements the hotplug support for virtio-scsi.
> When there is a device attached/detached, the virtio-scsi driver will be
> signaled via event virtual queue and it will add/remove the scsi device 
> in question automatically.
> 
> v2: handle no_event event
> v3: add handle event dropped, and typo fix
> 
> Signed-off-by: Sen Wang <senwang@linux.vnet.ibm.com>
> Signed-off-by: Cong Meng <mc@linux.vnet.ibm.com>
> ---
>  drivers/scsi/virtio_scsi.c  |  113 ++++++++++++++++++++++++++++++++++++++++++-
>  include/linux/virtio_scsi.h |    9 ++++
>  2 files changed, 121 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
> index 9fc5e67..d87446b 100644
> --- a/drivers/scsi/virtio_scsi.c
> +++ b/drivers/scsi/virtio_scsi.c
> @@ -25,6 +25,7 @@
>  #include <scsi/scsi_cmnd.h>
>  
>  #define VIRTIO_SCSI_MEMPOOL_SZ 64
> +#define VIRTIO_SCSI_EVENT_LEN 8
>  
>  /* Command queue element */
>  struct virtio_scsi_cmd {
> @@ -43,6 +44,12 @@ struct virtio_scsi_cmd {
>  	} resp;
>  } ____cacheline_aligned_in_smp;
>  
> +struct virtio_scsi_event_node {
> +	struct virtio_scsi *vscsi;
> +	struct virtio_scsi_event event;
> +	struct work_struct work;
> +};
> +
>  struct virtio_scsi_vq {
>  	/* Protects vq */
>  	spinlock_t vq_lock;
> @@ -67,6 +74,9 @@ struct virtio_scsi {
>  	struct virtio_scsi_vq event_vq;
>  	struct virtio_scsi_vq req_vq;
>  
> +	/* Get some buffers ready for event vq */
> +	struct virtio_scsi_event_node event_list[VIRTIO_SCSI_EVENT_LEN];
> +
>  	struct virtio_scsi_target_state *tgt[];
>  };
>  
> @@ -202,6 +212,97 @@ static void virtscsi_ctrl_done(struct virtqueue *vq)
>  	spin_unlock_irqrestore(&vscsi->ctrl_vq.vq_lock, flags);
>  };
>  
> +static int virtscsi_kick_event(struct virtio_scsi *vscsi,
> +			       struct virtio_scsi_event_node *event_node)
> +{
> +	int ret;
> +	struct scatterlist sg;
> +	unsigned long flags;
> +
> +	sg_set_buf(&sg, &event_node->event, sizeof(struct virtio_scsi_event));
> +
> +	spin_lock_irqsave(&vscsi->event_vq.vq_lock, flags);
> +
> +	ret = virtqueue_add_buf(vscsi->event_vq.vq, &sg, 0, 1, event_node, GFP_ATOMIC);
> +	if (ret >= 0)
> +		virtqueue_kick(vscsi->event_vq.vq);
> +
> +	spin_unlock_irqrestore(&vscsi->event_vq.vq_lock, flags);
> +
> +	return ret;
> +}
> +
> +static int virtscsi_kick_event_all(struct virtio_scsi *vscsi)
> +{
> +	int i;
> +
> +	for (i = 0; i < VIRTIO_SCSI_EVENT_LEN; i++) {
> +		vscsi->event_list[i].vscsi = vscsi;
> +		virtscsi_kick_event(vscsi, &vscsi->event_list[i]);
> +	}
> +
> +	return 0;
> +}
> +
> +static void virtscsi_handle_transport_reset(struct virtio_scsi *vscsi,
> +						struct virtio_scsi_event *event)
> +{
> +	struct scsi_device *sdev;
> +	struct Scsi_Host *shost = virtio_scsi_host(vscsi->vdev);
> +	unsigned int target = event->lun[1];
> +	unsigned int lun = (event->lun[2] << 8) | event->lun[3];
> +
> +	switch (event->reason) {
> +	case VIRTIO_SCSI_EVT_RESET_RESCAN:
> +		scsi_add_device(shost, 0, target, lun);
> +		break;
> +	case VIRTIO_SCSI_EVT_RESET_REMOVED:
> +		sdev = scsi_device_lookup(shost, 0, target, lun);
> +		if (sdev) {
> +			scsi_remove_device(sdev);
> +			scsi_device_put(sdev);
> +		} else {
> +			pr_err("SCSI device %d 0 %d %d not found\n",
> +				shost->host_no, target, lun);
> +		}
> +		break;
> +	default:
> +		pr_info("Unsupport virtio scsi event reason %x\n", event->reason);
> +	}
> +}
> +
> +static void virtscsi_handle_event(struct work_struct *work)
> +{
> +	struct virtio_scsi_event_node *event_node =
> +		container_of(work, struct virtio_scsi_event_node, work);
> +	struct virtio_scsi *vscsi = event_node->vscsi;
> +	struct virtio_scsi_event *event = &event_node->event;
> +
> +	if (event->event & VIRTIO_SCSI_T_EVENTS_MISSED) {
> +		event->event &= (~VIRTIO_SCSI_T_EVENTS_MISSED);

Coding standard (no parentheses on the right hand side of operators).

Also, you're missing a loop that calls cancel_work_sync in virtscsi_remove.

I believe with these changes we're good to go.  Thanks again, and sorry
for missing the cancel_work_sync issue so far.

Paolo

> +		scsi_scan_host(virtio_scsi_host(vscsi->vdev));
> +	}
> +
> +	switch (event->event) {
> +	case VIRTIO_SCSI_T_NO_EVENT:
> +		break;
> +	case VIRTIO_SCSI_T_TRANSPORT_RESET:
> +		virtscsi_handle_transport_reset(vscsi, event);
> +		break;
> +	default:
> +		pr_err("Unsupport virtio scsi event %x\n", event->event);
> +	}
> +	virtscsi_kick_event(vscsi, event_node);
> +}
> +
> +static void virtscsi_complete_event(void *buf)
> +{
> +	struct virtio_scsi_event_node *event_node = buf;
> +
> +	INIT_WORK(&event_node->work, virtscsi_handle_event);
> +	schedule_work(&event_node->work);
> +}
> +
>  static void virtscsi_event_done(struct virtqueue *vq)
>  {
>  	struct Scsi_Host *sh = virtio_scsi_host(vq->vdev);
> @@ -209,7 +310,7 @@ static void virtscsi_event_done(struct virtqueue *vq)
>  	unsigned long flags;
>  
>  	spin_lock_irqsave(&vscsi->event_vq.vq_lock, flags);
> -	virtscsi_vq_done(vq, virtscsi_complete_free);
> +	virtscsi_vq_done(vq, virtscsi_complete_event);
>  	spin_unlock_irqrestore(&vscsi->event_vq.vq_lock, flags);
>  };
>  
> @@ -510,6 +611,10 @@ static int virtscsi_init(struct virtio_device *vdev,
>  	virtscsi_config_set(vdev, cdb_size, VIRTIO_SCSI_CDB_SIZE);
>  	virtscsi_config_set(vdev, sense_size, VIRTIO_SCSI_SENSE_SIZE);
>  
> +	if (virtio_has_feature(vdev, VIRTIO_SCSI_F_HOTPLUG)) {
> +		virtscsi_kick_event_all(vscsi);
> +	}
> +
>  	/* We need to know how many segments before we allocate.  */
>  	sg_elems = virtscsi_config_get(vdev, seg_max) ?: 1;
>  
> @@ -608,7 +713,13 @@ static struct virtio_device_id id_table[] = {
>  	{ 0 },
>  };
>  
> +static unsigned int features[] = {
> +	VIRTIO_SCSI_F_HOTPLUG
> +};
> +
>  static struct virtio_driver virtio_scsi_driver = {
> +	.feature_table = features,
> +	.feature_table_size = ARRAY_SIZE(features),
>  	.driver.name = KBUILD_MODNAME,
>  	.driver.owner = THIS_MODULE,
>  	.id_table = id_table,
> diff --git a/include/linux/virtio_scsi.h b/include/linux/virtio_scsi.h
> index 8ddeafd..dc8d305 100644
> --- a/include/linux/virtio_scsi.h
> +++ b/include/linux/virtio_scsi.h
> @@ -69,6 +69,10 @@ struct virtio_scsi_config {
>  	u32 max_lun;
>  } __packed;
>  
> +/* Feature Bits */
> +#define VIRTIO_SCSI_F_INOUT                    0
> +#define VIRTIO_SCSI_F_HOTPLUG                  1
> +
>  /* Response codes */
>  #define VIRTIO_SCSI_S_OK                       0
>  #define VIRTIO_SCSI_S_OVERRUN                  1
> @@ -105,6 +109,11 @@ struct virtio_scsi_config {
>  #define VIRTIO_SCSI_T_TRANSPORT_RESET          1
>  #define VIRTIO_SCSI_T_ASYNC_NOTIFY             2
>  
> +/* Reasons of transport reset event */
> +#define VIRTIO_SCSI_EVT_RESET_HARD             0
> +#define VIRTIO_SCSI_EVT_RESET_RESCAN           1
> +#define VIRTIO_SCSI_EVT_RESET_REMOVED          2
> +
>  #define VIRTIO_SCSI_S_SIMPLE                   0
>  #define VIRTIO_SCSI_S_ORDERED                  1
>  #define VIRTIO_SCSI_S_HEAD                     2
>