Re: [PATCH] vsock: ratelimit unknown ioctl error message

[Stefano Garzarella]

On Fri, Oct 23, 2020 at 09:30:59PM +0000, David Laight wrote:
> From: Stefano Garzarella
> > Sent: 23 October 2020 15:10
> >
> > On Fri, Oct 23, 2020 at 01:21:13PM +0100, Colin King wrote:
> > >From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> > >
> > >When exercising the kernel with stress-ng with some ioctl tests the
> > >"Unknown ioctl" error message is spamming the kernel log at a high
> > >rate. Rate limit this message to reduce the noise.
> > >
> > >Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> > >---
> > > net/vmw_vsock/af_vsock.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > >diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
> > >index 9e93bc201cc0..b8feb9223454 100644
> > >--- a/net/vmw_vsock/af_vsock.c
> > >+++ b/net/vmw_vsock/af_vsock.c
> > >@@ -2072,7 +2072,7 @@ static long vsock_dev_do_ioctl(struct file *filp,
> > > 		break;
> > >
> > > 	default:
> > >-		pr_err("Unknown ioctl %d\n", cmd);
> > >+		pr_err_ratelimited("Unknown ioctl %d\n", cmd);
> >
> > Make sense, or maybe can we remove the error message returning only the
> > -EINVAL?
>
> Isn't the canonical error for unknown ioctl codes -ENOTTY?

Oh, thanks for pointing that out!

I had not paid attention to the error returned, but looking at it I 
noticed that perhaps the most appropriate would be -ENOIOCTLCMD.
In the ioctl syscall we return -ENOTTY, if the callback returns 
-ENOIOCTLCMD.

What do you think?

Stefano