storvsc: force discovery of LUNs that may have been removed.

The host asks the guest to scan when a LUN is removed or added.
The only way a guest can identify the removed LUN is when an I/O is
attempted on a removed LUN - the SRB status code indicates that the LUN
is invalid. We currently handle this SRB status and remove the device.

Rather than waiting for an I/O to remove the device, force the discovery of
LUNs that may have been removed prior to discovering LUNs that may have
been added.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: Long Li <longli@microsoft.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
index ab0bb98239b0d921bf01aae5e62b34589d5e4556..ae8293a388552db2a9982a5cee3681a2b866d098 100644 (file)
--- a/drivers/scsi/storvsc_drv.c
+++ b/drivers/scsi/storvsc_drv.c
@@ -414,10 +414,36 @@ static void storvsc_host_scan(struct work_struct *work)
 {
        struct storvsc_scan_work *wrk;
        struct Scsi_Host *host;
+       struct scsi_device *sdev;
+       unsigned long flags;
 
        wrk = container_of(work, struct storvsc_scan_work, work);
        host = wrk->host;
 
+       /*
+        * Before scanning the host, first check to see if any of the
+        * currrently known devices have been hot removed. We issue a
+        * "unit ready" command against all currently known devices.
+        * This I/O will result in an error for devices that have been
+        * removed. As part of handling the I/O error, we remove the device.
+        *
+        * When a LUN is added or removed, the host sends us a signal to
+        * scan the host. Thus we are forced to discover the LUNs that
+        * may have been removed this way.
+        */
+       mutex_lock(&host->scan_mutex);
+       spin_lock_irqsave(host->host_lock, flags);
+       list_for_each_entry(sdev, &host->__devices, siblings) {
+               spin_unlock_irqrestore(host->host_lock, flags);
+               scsi_test_unit_ready(sdev, 1, 1, NULL);
+               spin_lock_irqsave(host->host_lock, flags);
+               continue;
+       }
+       spin_unlock_irqrestore(host->host_lock, flags);
+       mutex_unlock(&host->scan_mutex);
+       /*
+        * Now scan the host to discover LUNs that may have been added.
+        */
        scsi_scan_host(host);
 
        kfree(wrk);