[PATCH v1 18/18] vfio/ccw: Manage ccw/mdev reference counts

[Eric Farman <farman@xxxxxxxxxxxxx>]

Take a reference to the vfio device when looking at the
corresponding vfio_ccw_private struct, and put it back
once we are finished.

Suggested-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Signed-off-by: Eric Farman <farman@xxxxxxxxxxxxx>
---
 drivers/s390/cio/vfio_ccw_drv.c     | 9 ++++++++-
 drivers/s390/cio/vfio_ccw_private.h | 2 ++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
index c8cbbad6e1c5..2e55fa45f76c 100644
--- a/drivers/s390/cio/vfio_ccw_drv.c
+++ b/drivers/s390/cio/vfio_ccw_drv.c
@@ -71,6 +71,7 @@ int vfio_ccw_sch_quiesce(struct subchannel *sch)
 		ret = cio_disable_subchannel(sch);
 	} while (ret == -EBUSY);
 
+	vfio_device_put(&private->vdev);
 	return ret;
 }
 
@@ -131,6 +132,7 @@ static void vfio_ccw_sch_irq(struct subchannel *sch)
 
 	inc_irq_stat(IRQIO_CIO);
 	vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_INTERRUPT);
+	vfio_device_put(&private->vdev);
 }
 
 struct vfio_ccw_private *vfio_ccw_alloc_private(struct mdev_device *mdev,
@@ -252,6 +254,7 @@ static void vfio_ccw_sch_shutdown(struct subchannel *sch)
 
 	vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_CLOSE);
 	vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_NOT_OPER);
+	vfio_device_put(&private->vdev);
 }
 
 /**
@@ -287,6 +290,7 @@ static int vfio_ccw_sch_event(struct subchannel *sch, int process)
 
 out_unlock:
 	spin_unlock_irqrestore(sch->lock, flags);
+	vfio_device_put(&private->vdev);
 
 	return rc;
 }
@@ -334,8 +338,10 @@ static int vfio_ccw_chp_event(struct subchannel *sch,
 			   sch->schid.ssid, sch->schid.sch_no,
 			   mask, event);
 
-	if (cio_update_schib(sch))
+	if (cio_update_schib(sch)) {
+		vfio_device_put(&private->vdev);
 		return -ENODEV;
+	}
 
 	switch (event) {
 	case CHP_VARY_OFF:
@@ -365,6 +371,7 @@ static int vfio_ccw_chp_event(struct subchannel *sch,
 		break;
 	}
 
+	vfio_device_put(&private->vdev);
 	return 0;
 }
 
diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h
index 3833204bd388..be238cf277ff 100644
--- a/drivers/s390/cio/vfio_ccw_private.h
+++ b/drivers/s390/cio/vfio_ccw_private.h
@@ -135,6 +135,8 @@ static inline struct vfio_ccw_private *vfio_ccw_get_private(struct subchannel *s
 		return NULL;
 
 	private = dev_get_drvdata(&sch->dev);
+	if (private && !vfio_device_try_get(&private->vdev))
+		private = NULL;
 
 	return private;
 }
-- 
2.32.0