netdev - Re: [PATCHv2 1/1] xdp: remove the function xsk_map

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Message-ID: <CAJ8uoz2rfeDKhJCRwNCSs2oT+M=Xv0z=pW+7k2m5yqq-K6ceDg@mail.gmail.com>
Date:   Mon, 23 Nov 2020 14:49:11 +0100
From:   Magnus Karlsson <magnus.karlsson@...il.com>
To:     Zhu Yanjun <zyjzyj2000@...il.com>
Cc:     "Karlsson, Magnus" <magnus.karlsson@...el.com>,
        Björn Töpel <bjorn.topel@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>
Subject: Re: [PATCHv2 1/1] xdp: remove the function xsk_map_inc

On Mon, Nov 23, 2020 at 2:37 PM Zhu Yanjun <zyjzyj2000@...il.com> wrote:
>
> On Mon, Nov 23, 2020 at 8:19 PM Magnus Karlsson
> <magnus.karlsson@...il.com> wrote:
> >
> > On Mon, Nov 23, 2020 at 1:11 PM Zhu Yanjun <zyjzyj2000@...il.com> wrote:
> > >
> > > On Mon, Nov 23, 2020 at 8:05 PM <zyjzyj2000@...il.com> wrote:
> > > >
> > > > From: Zhu Yanjun <zyjzyj2000@...il.com>
> > > >
> > > > The function xsk_map_inc is a simple wrapper of bpf_map_inc and
> > > > always returns zero. As such, replacing this function with bpf_map_inc
> > > > and removing the test code.
> > > >
> > > > Signed-off-by: Zhu Yanjun <zyjzyj2000@...il.com>
> > >
> > >
> > > > ---
> > > >  net/xdp/xsk.c    |  1 -
> > > >  net/xdp/xsk.h    |  1 -
> > > >  net/xdp/xskmap.c | 13 +------------
> > > >  3 files changed, 1 insertion(+), 14 deletions(-)
> > > >
> > > > diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> > > > index cfbec3989a76..c1b8a888591c 100644
> > > > --- a/net/xdp/xsk.c
> > > > +++ b/net/xdp/xsk.c
> > > > @@ -548,7 +548,6 @@ static struct xsk_map *xsk_get_map_list_entry(struct xdp_sock *xs,
> > > >         node = list_first_entry_or_null(&xs->map_list, struct xsk_map_node,
> > > >                                         node);
> > > >         if (node) {
> > > > -               WARN_ON(xsk_map_inc(node->map));
> >
> > This should be bpf_map_inc(&node->map->map); Think you forgot to
> > convert this one.
>
> In include/linux/bpf.h:
> "
> ...
> 1213 void bpf_map_inc(struct bpf_map *map);
> ...
> "

Sorry if I was not clear enough. What I meant is that you cannot just
remove WARN_ON(xsk_map_inc(node->map)). You need to replace it with
bpf_map_inc(&node->map->map), otherwise you will not make a map_inc
and the refcount will be wrong. Please send a v3 using git send-email
so it is nice and clean.

> Zhu Yanjun
> >
> > > >                 map = node->map;
> > > >                 *map_entry = node->map_entry;
> > > >         }
> > > > diff --git a/net/xdp/xsk.h b/net/xdp/xsk.h
> > > > index b9e896cee5bb..0aad25c0e223 100644
> > > > --- a/net/xdp/xsk.h
> > > > +++ b/net/xdp/xsk.h
> > > > @@ -41,7 +41,6 @@ static inline struct xdp_sock *xdp_sk(struct sock *sk)
> > > >
> > > >  void xsk_map_try_sock_delete(struct xsk_map *map, struct xdp_sock *xs,
> > > >                              struct xdp_sock **map_entry);
> > > > -int xsk_map_inc(struct xsk_map *map);
> > > >  void xsk_map_put(struct xsk_map *map);
> > > >  void xsk_clear_pool_at_qid(struct net_device *dev, u16 queue_id);
> > > >  int xsk_reg_pool_at_qid(struct net_device *dev, struct xsk_buff_pool *pool,
> > > > diff --git a/net/xdp/xskmap.c b/net/xdp/xskmap.c
> > > > index 49da2b8ace8b..6b7e9a72b101 100644
> > > > --- a/net/xdp/xskmap.c
> > > > +++ b/net/xdp/xskmap.c
> > > > @@ -11,12 +11,6 @@
> > > >
> > > >  #include "xsk.h"
> > > >
> > > > -int xsk_map_inc(struct xsk_map *map)
> > > > -{
> > > > -       bpf_map_inc(&map->map);
> > > > -       return 0;
> > > > -}
> > >
> > > Hi, Magnus
> > >
> > > The function xsk_map_inc is replaced with bpf_map_inc.
> > >
> > > Zhu Yanjun
> > >
> > > > -
> > > >  void xsk_map_put(struct xsk_map *map)
> > > >  {
> > > >         bpf_map_put(&map->map);
> > > > @@ -26,17 +20,12 @@ static struct xsk_map_node *xsk_map_node_alloc(struct xsk_map *map,
> > > >                                                struct xdp_sock **map_entry)
> > > >  {
> > > >         struct xsk_map_node *node;
> > > > -       int err;
> > > >
> > > >         node = kzalloc(sizeof(*node), GFP_ATOMIC | __GFP_NOWARN);
> > > >         if (!node)
> > > >                 return ERR_PTR(-ENOMEM);
> > > >
> > > > -       err = xsk_map_inc(map);
> > > > -       if (err) {
> > > > -               kfree(node);
> > > > -               return ERR_PTR(err);
> > > > -       }
> > > > +       bpf_map_inc(&map->map);
> > > >
> > > >         node->map = map;
> > > >         node->map_entry = map_entry;
> > > > --
> > > > 2.25.1
> > > >