linux-kernel - Re: [PATCH v2 15/16] netdevsim: use netmem descriptor and APIs for page pool

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Message-ID: <CAHS8izMwUvLYZipvj+0gcK4Ch8EqGu3g00aP488563VD3d9N9g@mail.gmail.com>
Date: Tue, 27 May 2025 20:25:54 -0700
From: Mina Almasry <almasrymina@...gle.com>
To: Byungchul Park <byungchul@...com>
Cc: willy@...radead.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-mm@...ck.org, kernel_team@...ynix.com, kuba@...nel.org, 
	ilias.apalodimas@...aro.org, harry.yoo@...cle.com, hawk@...nel.org, 
	akpm@...ux-foundation.org, davem@...emloft.net, john.fastabend@...il.com, 
	andrew+netdev@...n.ch, asml.silence@...il.com, toke@...hat.com, 
	tariqt@...dia.com, edumazet@...gle.com, pabeni@...hat.com, saeedm@...dia.com, 
	leon@...nel.org, ast@...nel.org, daniel@...earbox.net, david@...hat.com, 
	lorenzo.stoakes@...cle.com, Liam.Howlett@...cle.com, vbabka@...e.cz, 
	rppt@...nel.org, surenb@...gle.com, mhocko@...e.com, horms@...nel.org, 
	linux-rdma@...r.kernel.org, bpf@...r.kernel.org, vishal.moola@...il.com
Subject: Re: [PATCH v2 15/16] netdevsim: use netmem descriptor and APIs for
 page pool

On Tue, May 27, 2025 at 7:29 PM Byungchul Park <byungchul@...com> wrote:
>
> To simplify struct page, the effort to separate its own descriptor from
> struct page is required and the work for page pool is on going.
>
> Use netmem descriptor and APIs for page pool in netdevsim code.
>
> Signed-off-by: Byungchul Park <byungchul@...com>
> ---
>  drivers/net/netdevsim/netdev.c    | 19 ++++++++++---------
>  drivers/net/netdevsim/netdevsim.h |  2 +-
>  2 files changed, 11 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/net/netdevsim/netdev.c b/drivers/net/netdevsim/netdev.c
> index af545d42961c..d134a6195bfa 100644
> --- a/drivers/net/netdevsim/netdev.c
> +++ b/drivers/net/netdevsim/netdev.c
> @@ -821,7 +821,7 @@ nsim_pp_hold_read(struct file *file, char __user *data,
>         struct netdevsim *ns = file->private_data;
>         char buf[3] = "n\n";
>
> -       if (ns->page)
> +       if (ns->netmem)
>                 buf[0] = 'y';
>
>         return simple_read_from_buffer(data, count, ppos, buf, 2);
> @@ -841,18 +841,19 @@ nsim_pp_hold_write(struct file *file, const char __user *data,
>
>         rtnl_lock();
>         ret = count;
> -       if (val == !!ns->page)
> +       if (val == !!ns->netmem)
>                 goto exit;
>
>         if (!netif_running(ns->netdev) && val) {
>                 ret = -ENETDOWN;
>         } else if (val) {
> -               ns->page = page_pool_dev_alloc_pages(ns->rq[0]->page_pool);
> -               if (!ns->page)
> +               ns->netmem = page_pool_alloc_netmems(ns->rq[0]->page_pool,
> +                                                    GFP_ATOMIC | __GFP_NOWARN);

Can we add a page_pool_dev_alloc_netmems instead of doing this GFP at
the callsite? Other drivers will be interested in using
_dev_alloc_netmems as well.

-- 
Thanks,
Mina