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SubjectRe: [PATCH] storvsc: Avoid excessive host scan on controller change
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On 10/31/2017 05:58 PM, Long Li wrote:
> From: Long Li <longli@microsoft.com>
>
> When there are multiple disks attached to the same SCSI controller,
> the host may send several VSTOR_OPERATION_REMOVE_DEVICE or
> VSTOR_OPERATION_ENUMERATE_BUS messages in a row, to indicate there is a
> change on the SCSI controller. In response, storvsc rescans the SCSI host.
>
> There is no need to do multiple scans on the same host. Fix the code to do
> only one scan.
>
> Signed-off-by: Long Li <longli@microsoft.com>
> ---
> drivers/scsi/storvsc_drv.c | 26 +++++++++++---------------
> 1 file changed, 11 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
> index 6febcdb..b602f52 100644
> --- a/drivers/scsi/storvsc_drv.c
> +++ b/drivers/scsi/storvsc_drv.c
> @@ -488,6 +488,8 @@ struct hv_host_device {
> unsigned char target;
> struct workqueue_struct *handle_error_wq;
> char work_q_name[20];
> + struct work_struct host_scan_work;
> + struct Scsi_Host *host;
> };
>
> struct storvsc_scan_work {
> @@ -516,13 +518,12 @@ static void storvsc_device_scan(struct work_struct *work)
>
> static void storvsc_host_scan(struct work_struct *work)
> {
> - struct storvsc_scan_work *wrk;
> struct Scsi_Host *host;
> struct scsi_device *sdev;
> + struct hv_host_device *host_device =
> + container_of(work, struct hv_host_device, host_scan_work);
>
> - wrk = container_of(work, struct storvsc_scan_work, work);
> - host = wrk->host;
> -
> + host = host_device->host;
> /*
> * Before scanning the host, first check to see if any of the
> * currrently known devices have been hot removed. We issue a
> @@ -542,8 +543,6 @@ static void storvsc_host_scan(struct work_struct *work)
> * Now scan the host to discover LUNs that may have been added.
> */
> scsi_scan_host(host);
> -
> - kfree(wrk);
> }
>
> static void storvsc_remove_lun(struct work_struct *work)
> @@ -1119,8 +1118,7 @@ static void storvsc_on_receive(struct storvsc_device *stor_device,
> struct vstor_packet *vstor_packet,
> struct storvsc_cmd_request *request)
> {
> - struct storvsc_scan_work *work;
> -
> + struct hv_host_device *host_dev;
> switch (vstor_packet->operation) {
> case VSTOR_OPERATION_COMPLETE_IO:
> storvsc_on_io_completion(stor_device, vstor_packet, request);
> @@ -1128,13 +1126,9 @@ static void storvsc_on_receive(struct storvsc_device *stor_device,
>
> case VSTOR_OPERATION_REMOVE_DEVICE:
> case VSTOR_OPERATION_ENUMERATE_BUS:
> - work = kmalloc(sizeof(struct storvsc_scan_work), GFP_ATOMIC);
> - if (!work)
> - return;
> -
> - INIT_WORK(&work->work, storvsc_host_scan);
> - work->host = stor_device->host;
> - schedule_work(&work->work);
> + host_dev = shost_priv(stor_device->host);
> + queue_work(
> + host_dev->handle_error_wq, &host_dev->host_scan_work);
> break;
>
> case VSTOR_OPERATION_FCHBA_DATA:
> @@ -1747,6 +1741,7 @@ static int storvsc_probe(struct hv_device *device,
>
> host_dev->port = host->host_no;
> host_dev->dev = device;
> + host_dev->host = host;
>
>
> stor_device = kzalloc(sizeof(struct storvsc_device), GFP_KERNEL);
> @@ -1815,6 +1810,7 @@ static int storvsc_probe(struct hv_device *device,
> create_singlethread_workqueue(host_dev->work_q_name);
> if (!host_dev->handle_error_wq)
> goto err_out2;
> + INIT_WORK(&host_dev->host_scan_work, storvsc_host_scan);
> /* Register the HBA and start the scsi bus scan */
> ret = scsi_add_host(host, &device->device);
> if (ret != 0)

I've tested this patch with both a multipath failover while running fio
and taking hyperV snap shots while luns are being hot added and removed.

Tested-by: Cathy Avery <cavery@redhat.com>



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