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Date:   Fri, 28 Apr 2023 23:11:55 +0800
From:   Cai Huoqing <cai.huoqing@linux.dev>
To:     Herbert Xu <herbert@gondor.apana.org.au>
Cc:     kuba@kernel.org, davem@davemloft.net, edumazet@google.com,
        pabeni@redhat.com, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] netdevsim: fib: Make use of rhashtable_iter
Message-ID: <ZEviO+NPFP/IoiO2@chq-MS-7D45>
References: <20230425144556.98799-1-cai.huoqing@linux.dev>
 <ZEjw7XXFro6zYYXz@gondor.apana.org.au>
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On 26 4月 23 17:37:49, Herbert Xu wrote:
> Cai Huoqing <cai.huoqing@linux.dev> wrote:
> > Iterating 'fib_rt_ht' by rhashtable_walk_next and rhashtable_iter directly
> > instead of using list_for_each, because each entry of fib_rt_ht can be
> > found by rhashtable API. And remove fib_rt_list.
> > 
> > Signed-off-by: Cai Huoqing <cai.huoqing@linux.dev>
> > ---
> > drivers/net/netdevsim/fib.c | 37 ++++++++++++++++++-------------------
> > 1 file changed, 18 insertions(+), 19 deletions(-)
> 
> What is the rationale for this patch? Are you trying to save
> memory?
Hi 
Thanks for your reply,

I think not need to use two structs to link fib_rt node, 
fib_rt_list is redundant.

Thanks,
Cai-

> 
> > @@ -1099,9 +1090,12 @@ static void nsim_fib_dump_inconsistent(struct notifier_block *nb)
> >        /* The notifier block is still not registered, so we do not need to
> >         * take any locks here.
> >         */
> > -       list_for_each_entry_safe(fib_rt, fib_rt_tmp, &data->fib_rt_list, list) {
> > -               rhashtable_remove_fast(&data->fib_rt_ht, &fib_rt->ht_node,
> > +       rhashtable_walk_enter(&data->fib_rt_ht, &hti);
> > +       rhashtable_walk_start(&hti);
> > +       while ((pos = rhashtable_walk_next(&hti))) {
> > +               rhashtable_remove_fast(&data->fib_rt_ht, hti.p,
> >                                       nsim_fib_rt_ht_params);
> > +               fib_rt = rhashtable_walk_peek(&hti);
> >                nsim_fib_rt_free(fib_rt, data);
> >        }
> 
> In general rhashtable walks are not stable.  You may miss entries
> or see entries twice.  They should be avoided unless absolutely
> necessary.
Agree, but how about using rhashtable_free_and_destroy here
instead of rhashtable_walk_next in this patch.

> 
> Cheers,
> -- 
> Email: Herbert Xu <herbert@gondor.apana.org.au>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt