[PATCH v2 2/2] Drivers: hv: vmbus: Fix rescind handling in uio_hv_generic

[Naman Jain <namjain@linux.microsoft.com>]

Rescind offer handling relies on rescind callbacks for some of the
resources cleanup, if they are registered. It does not unregister
vmbus device for the primary channel closure, when callback is
registered. Without it, next onoffer does not come, rescind flag
remains set and device goes to unusable state.

Add logic to unregister vmbus for the primary channel in rescind callback
to ensure channel removal and relid release, and to ensure that next
onoffer can be received and handled properly.

Cc: stable@vger.kernel.org
Fixes: ca3cda6fcf1e ("uio_hv_generic: add rescind support")
Signed-off-by: Naman Jain <namjain@linux.microsoft.com>
---
 drivers/hv/vmbus_drv.c       | 1 +
 drivers/uio/uio_hv_generic.c | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 7242c4920427..c405295b930a 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1980,6 +1980,7 @@ void vmbus_device_unregister(struct hv_device *device_obj)
 	 */
 	device_unregister(&device_obj->device);
 }
+EXPORT_SYMBOL_GPL(vmbus_device_unregister);
 
 #ifdef CONFIG_ACPI
 /*
diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c
index e3e66a3e85a8..870409599411 100644
--- a/drivers/uio/uio_hv_generic.c
+++ b/drivers/uio/uio_hv_generic.c
@@ -121,6 +121,14 @@ static void hv_uio_rescind(struct vmbus_channel *channel)
 
 	/* Wake up reader */
 	uio_event_notify(&pdata->info);
+
+	/*
+	 * With rescind callback registered, rescind path will not unregister the device
+	 * from vmbus when the primary channel is rescinded.
+	 * Without it, rescind handling is incomplete and next onoffer msg does not come.
+	 * Unregister the device from vmbus here.
+	 */
+	vmbus_device_unregister(channel->device_obj);
 }
 
 /* Sysfs API to allow mmap of the ring buffers
-- 
2.34.1