linux-kernel - Re: [PATCH net-next v1] netdevsim: Forbid devlink reload when adding or deleting ports

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Date:   Fri, 6 Aug 2021 14:19:43 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     "David S . Miller" <davem@...emloft.net>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v1] netdevsim: Forbid devlink reload when adding
 or deleting ports

On Thu, Aug 05, 2021 at 12:12:03PM -0700, Jakub Kicinski wrote:
> On Thu, 5 Aug 2021 21:02:23 +0300 Leon Romanovsky wrote:
> > > > As it should, given add/delete ports takes the port_list_lock which is
> > > > destroyed by down but not (due to the forced failure) re-initialized by
> > > > up.
> > > > 
> > > > If we want to handle adding ports while down we can just bump port
> > > > count and return, although I don't think there's a practical need
> > > > to support that.  
> > > 
> > > Sorry, but for me netdevsim looks like complete dumpster. 
> 
> I worry that netdevsim's gone unwieldy as a reflection of the quality of
> the devlink APIs that got added, not by itself :/
> 
> > > It was intended for fast prototyping, but ended to be huge pile of
> > > debugfs entries and selftest to execute random flows.
> 
> It's for selftests, IDK what fast prototyping is in terms of driver
> APIs. Fast prototyping makes me think of the "it works" attitude which
> is not sufficiently high bar for core APIs IMO, I'm sure you'll agree.
> 
> netdevsim was written specifically to be able to exercise HW APIs which
> are implemented by small fraction of drivers. Especially offload APIs
> as those can easily be broken by people changing the SW implementation
> without capable HW at hand.
> 
> BTW I wonder if there is a term in human science of situation like when
> a recent contributor tells the guy who wrote the code what the code was
> intended for :)

"Teaching grandmother to suck eggs" ? :)

> 
> > > Do you want me to move in_reload = false line to be after if (nsim_dev->fail_reload)
> > > check?  
> > 
> > BTW, the current implementation where in_reload before if, actually
> > preserves same behaviour as was with devlink_reload_enable() implementation.
> 
> Right, but I think as you rightly pointed out the current protection
> of reload is broken. I'm not saying you must make it perfect or else..
> just pointing out a gap you could address if you so choose.

I don't know, netdevsim needs some dedicated cleanup.

Thanks