media: v4l2-core: push taking ioctl mutex down to ioctl handler

The ioctl serialization mutex (vdev->lock or q->lock for vb2 queues)
was taken at the highest level in v4l2-dev.c. This prevents more
fine-grained locking since at that level we cannot examine the ioctl
arguments, we can only do that after video_usercopy is called.

So push the locking down to __video_do_ioctl() and subdev_do_ioctl_lock().

This also allows us to make a few functions in v4l2-ioctl.c static and
video_usercopy() is no longer exported.

The locking scheme is not changed by this patch, just pushed down.

Signed-off-by: Hans Verkuil <hansverk@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

1 files changed, 16 insertions, 1 deletions

diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index f9eed938d348..6a7f7f75dfd7 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -502,10 +502,25 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
 	return 0;
 }
 
+static long subdev_do_ioctl_lock(struct file *file, unsigned int cmd, void *arg)
+{
+	struct video_device *vdev = video_devdata(file);
+	struct mutex *lock = vdev->lock;
+	long ret = -ENODEV;
+
+	if (lock && mutex_lock_interruptible(lock))
+		return -ERESTARTSYS;
+	if (video_is_registered(vdev))
+		ret = subdev_do_ioctl(file, cmd, arg);
+	if (lock)
+		mutex_unlock(lock);
+	return ret;
+}
+
 static long subdev_ioctl(struct file *file, unsigned int cmd,
 	unsigned long arg)
 {
-	return video_usercopy(file, cmd, arg, subdev_do_ioctl);
+	return video_usercopy(file, cmd, arg, subdev_do_ioctl_lock);
 }
 
 #ifdef CONFIG_COMPAT