netdev - Re: [PATCH 2/6 bpf-next] Clean up xsk reuseq API

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Message-ID: <20190628134121.2f54c349@cakuba.netronome.com>
Date:   Fri, 28 Jun 2019 13:41:21 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     "Jonathan Lemon" <jonathan.lemon@...il.com>
Cc:     netdev@...r.kernel.org, bjorn.topel@...el.com,
        magnus.karlsson@...el.com, saeedm@...lanox.com,
        maximmi@...lanox.com, brouer@...hat.com, kernel-team@...com
Subject: Re: [PATCH 2/6 bpf-next] Clean up xsk reuseq API

On Thu, 27 Jun 2019 19:31:26 -0700, Jonathan Lemon wrote:
> On 27 Jun 2019, at 15:38, Jakub Kicinski wrote:
> 
> > On Thu, 27 Jun 2019 15:08:32 -0700, Jonathan Lemon wrote:  
> >> The reuseq is actually a recycle stack, only accessed from the kernel 
> >> side.
> >> Also, the implementation details of the stack should belong to the 
> >> umem
> >> object, and not exposed to the caller.
> >>
> >> Clean up and rename for consistency in preparation for the next 
> >> patch.
> >>
> >> Signed-off-by: Jonathan Lemon <jonathan.lemon@...il.com>  
> >
> > Prepare/swap is to cater to how drivers should be written - being able
> > to allocate resources independently of those currently used.  Allowing
> > for changing ring sizes and counts on the fly.  This patch makes it
> > harder to write drivers in the way we are encouraging people to.
> >
> > IOW no, please don't do this.  
> 
> The main reason I rewrote this was to provide the same type
> of functionality as realloc() - no need to allocate/initialize a new
> array if the old one would still end up being used.  This would seem
> to be a win for the typical case of having the interface go up/down.
> 
> Perhaps I should have named the function differently?

Perhaps add a helper which calls both parts to help poorly architected
drivers?