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>

1 files changed, 26 insertions, 0 deletions

diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
index ab0bb98239b0..ae8293a38855 100644
--- 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);