[PATCH] usb: uas: wait for pending commands before unbinding

[Jiayi Li]

USB core normally disables interface endpoints before calling
uas_disconnect(). This cancels pending URBs while the device may still
be processing the associated commands. Some storage bridges then stop
responding after a driver rebind and need a disconnect and reconnect
to recover.

Enable soft unbinding and block new SCSI requests before waiting for
pending commands to finish. This keeps the endpoints available until
the wait completes. Stop waiting when USB core marks the device as
not attached, and continue with the existing cleanup on timeout.

Keep requests blocked when leaving the preparation step, including on
timeout. Set resetting before unblocking the host so that queued
requests cannot submit new URBs during teardown.

---
diff --git a/drivers/usb/storage/uas.c b/drivers/usb/storage/uas.c
index 2651629..58a67d7 100644
--- a/drivers/usb/storage/uas.c
+++ b/drivers/usb/storage/uas.c
@@ -9,6 +9,7 @@
  */
 
 #include <linux/blkdev.h>
+#include <linux/delay.h>
 #include <linux/slab.h>
 #include <linux/types.h>
 #include <linux/module.h>
@@ -1211,16 +1212,55 @@ static int uas_reset_resume(struct usb_interface *intf)
 	return 0;
 }
 
+static void uas_pre_disconnect(struct usb_interface *intf)
+{
+	struct Scsi_Host *shost = usb_get_intfdata(intf);
+	struct uas_dev_info *devinfo = (struct uas_dev_info *)shost->hostdata;
+	unsigned long flags, start_time;
+
+	spin_lock_irqsave(shost->host_lock, flags);
+	scsi_block_requests(shost);
+	spin_unlock_irqrestore(shost->host_lock, flags);
+
+	start_time = jiffies;
+	for (;;) {
+		if (READ_ONCE(devinfo->udev->state) == USB_STATE_NOTATTACHED)
+			return;
+
+		flush_work(&devinfo->work);
+
+		if (!usb_wait_anchor_empty_timeout(&devinfo->sense_urbs, 5000))
+			break;
+
+		if (!usb_wait_anchor_empty_timeout(&devinfo->data_urbs, 500))
+			break;
+
+		if (time_after(jiffies, start_time + 5 * HZ))
+			break;
+		if (uas_cmnd_list_empty(devinfo))
+			return;
+
+		msleep(20);
+	}
+
+	shost_printk(KERN_ERR, shost, "%s: timed out\n", __func__);
+}
+
 static void uas_disconnect(struct usb_interface *intf)
 {
 	struct Scsi_Host *shost = usb_get_intfdata(intf);
 	struct uas_dev_info *devinfo = (struct uas_dev_info *)shost->hostdata;
 	unsigned long flags;
 
+	uas_pre_disconnect(intf);
+
 	spin_lock_irqsave(&devinfo->lock, flags);
 	devinfo->resetting = 1;
 	spin_unlock_irqrestore(&devinfo->lock, flags);
 
+	if (shost->host_self_blocked)
+		scsi_unblock_requests(shost);
+
 	cancel_work_sync(&devinfo->work);
 	usb_kill_anchored_urbs(&devinfo->cmd_urbs);
 	usb_kill_anchored_urbs(&devinfo->sense_urbs);
@@ -1260,6 +1300,7 @@ static void uas_shutdown(struct usb_interface *intf)
 
 static struct usb_driver uas_driver = {
 	.name = "uas",
+	.soft_unbind = 1,
 	.probe = uas_probe,
 	.disconnect = uas_disconnect,
 	.pre_reset = uas_pre_reset,