linux-kernel - [PATCH] scsi: virtio_scsi: unplug LUNs when events missed

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Message-ID: <20190903170408.32286-1-mlupfer@ddn.com>
Date:   Tue, 3 Sep 2019 17:04:20 +0000
From:   Matt Lupfer <mlupfer@....com>
To:     "Michael S . Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        "James E . J . Bottomley" <jejb@...ux.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>
CC:     "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Matt Lupfer <mlupfer@....com>
Subject: [PATCH] scsi: virtio_scsi: unplug LUNs when events missed

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@....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);
+
+		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