netdev - Re: [PATCH net-next V7 07/14] devlink: Add parent dev to devlink API

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Message-ID: <9d3d4e49cec85473619eb5166f01168a6ae3fd85.camel@nvidia.com>
Date: Wed, 11 Feb 2026 16:28:14 +0000
From: Cosmin Ratiu <cratiu@...dia.com>
To: Tariq Toukan <tariqt@...dia.com>, "kuba@...nel.org" <kuba@...nel.org>
CC: "corbet@....net" <corbet@....net>, "andrew+netdev@...n.ch"
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Subject: Re: [PATCH net-next V7 07/14] devlink: Add parent dev to devlink API

On Mon, 2026-02-02 at 20:00 -0800, Jakub Kicinski wrote:
> > +		info->user_ptr[1] = parent_devlink;
> 
> Let's convert devlink to use proper overlay struct over info->cb ?
> The user_ptr array only has two entries so devlink stuffs all the
> extra pointers into the second slot. But the cb is much larger - 48B
> so we can easily give each of these values a dedicated pointer.

I assume you are referring to info->ctx, added by Paolo as part of the
netshaper series. If that's the case, sure, I'll convert devlink to
that as part of the next version of this series.

> 
> > +		/* Drop the parent devlink lock but don't release
> > the reference.
> > +		 * This will keep it alive until the end of the
> > request.
> > +		 */
> 
> To be clear -- devlink instances do not behave like netdev instances.
> netdev instances prevent unregistration of the netdev.
> devlink refs are normal refs, they just keep the memory around.
> If memory serves me..

If no reference is held, a concurrent user op could release the parent
devlink instance altogether, and free its memory, that's the reason for
keeping a ref alive for the duration of this request.

Cosmin.