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From: "Björn Töpel" <bjorn.topel@gmail.com>
To: Song Liu <liu.song.a23@gmail.com>
Cc: "Alexei Starovoitov" <ast@kernel.org>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	Networking <netdev@vger.kernel.org>,
	"Björn Töpel" <bjorn.topel@intel.com>,
	"Magnus Karlsson" <magnus.karlsson@intel.com>,
	"Bruce Richardson" <bruce.richardson@intel.com>,
	bpf <bpf@vger.kernel.org>
Subject: Re: [PATCH bpf-next v2 1/2] xsk: remove AF_XDP socket from map when the socket is released
Date: Mon, 3 Jun 2019 11:25:19 +0200
Message-ID: <CAJ+HfNggDLVCzAqsFS06+xa6uyH95+jC=74kAi-cJYUcwwnmCg@mail.gmail.com> (raw)
In-Reply-To: <CAPhsuW7asezC+0MA3tNyU9ms0rX9iP7Dk0QW4qqXvNvSECrpGA@mail.gmail.com>

On Sun, 2 Jun 2019 at 00:32, Song Liu <liu.song.a23@gmail.com> wrote:
>
> On Wed, May 22, 2019 at 6:38 AM Björn Töpel <bjorn.topel@gmail.com> wrote:
> >
> > From: Björn Töpel <bjorn.topel@intel.com>
> >
> > When an AF_XDP socket is released/closed the XSKMAP still holds a
> > reference to the socket in a "released" state. The socket will still
> > use the netdev queue resource, and block newly created sockets from
> > attaching to that queue, but no user application can access the
> > fill/complete/rx/tx queues. This results in that all applications need
> > to explicitly clear the map entry from the old "zombie state"
> > socket. This should be done automatically.
> >
> > After this patch, when a socket is released, it will remove itself
> > from all the XSKMAPs it resides in, allowing the socket application to
> > remove the code that cleans the XSKMAP entry.
> >
> > This behavior is also closer to that of SOCKMAP, making the two socket
> > maps more consistent.
> >
> > Suggested-by: Bruce Richardson <bruce.richardson@intel.com>
> > Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
> > ---
> >  include/net/xdp_sock.h |   3 ++
> >  kernel/bpf/xskmap.c    | 101 +++++++++++++++++++++++++++++++++++------
> >  net/xdp/xsk.c          |  25 ++++++++++
> >  3 files changed, 116 insertions(+), 13 deletions(-)
> >
> > diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h
> > index d074b6d60f8a..b5f8f9f826d0 100644
> > --- a/include/net/xdp_sock.h
> > +++ b/include/net/xdp_sock.h
> > @@ -68,6 +68,8 @@ struct xdp_sock {
> >          */
> >         spinlock_t tx_completion_lock;
> >         u64 rx_dropped;
> > +       struct list_head map_list;
> > +       spinlock_t map_list_lock;
> >  };
> >
> >  struct xdp_buff;
> > @@ -87,6 +89,7 @@ struct xdp_umem_fq_reuse *xsk_reuseq_swap(struct xdp_umem *umem,
> >                                           struct xdp_umem_fq_reuse *newq);
> >  void xsk_reuseq_free(struct xdp_umem_fq_reuse *rq);
> >  struct xdp_umem *xdp_get_umem_from_qid(struct net_device *dev, u16 queue_id);
> > +void xsk_map_delete_from_node(struct xdp_sock *xs, struct list_head *node);
> >
> >  static inline char *xdp_umem_get_data(struct xdp_umem *umem, u64 addr)
> >  {
> > diff --git a/kernel/bpf/xskmap.c b/kernel/bpf/xskmap.c
> > index 686d244e798d..318f6a07fa31 100644
> > --- a/kernel/bpf/xskmap.c
> > +++ b/kernel/bpf/xskmap.c
> > @@ -13,8 +13,58 @@ struct xsk_map {
> >         struct bpf_map map;
> >         struct xdp_sock **xsk_map;
> >         struct list_head __percpu *flush_list;
> > +       spinlock_t lock;
> >  };
> >
> > +/* Nodes are linked in the struct xdp_sock map_list field, and used to
> > + * track which maps a certain socket reside in.
> > + */
> > +struct xsk_map_node {
> > +       struct list_head node;
> > +       struct xsk_map *map;
> > +       struct xdp_sock **map_entry;
> > +};
>
> Why do we need map_entry to be struct xdp_sock **? I think we could
> just use struct xdp_sock *? Or did I miss anytihg?
>

It's a reference into the map (which is an array of xdp_sock *), so
that it's simple to clear. Would you prefer storing the index of the
map, and doing a lookup?

Björn

> Thanks,
> Song
>
>
> > +
> > +static struct xsk_map_node *xsk_map_node_alloc(void)
> > +{
> > +       return kzalloc(sizeof(struct xsk_map_node), GFP_ATOMIC | __GFP_NOWARN);
> > +}
> > +
> > +static void xsk_map_node_free(struct xsk_map_node *node)
> > +{
> > +       kfree(node);
> > +}
> > +
> > +static void xsk_map_node_init(struct xsk_map_node *node,
> > +                             struct xsk_map *map,
> > +                             struct xdp_sock **map_entry)
> > +{
> > +       node->map = map;
> > +       node->map_entry = map_entry;
> > +}
> > +
> > +static void xsk_map_add_node(struct xdp_sock *xs, struct xsk_map_node *node)
> > +{
> > +       spin_lock_bh(&xs->map_list_lock);
> > +       list_add_tail(&node->node, &xs->map_list);
> > +       spin_unlock_bh(&xs->map_list_lock);
> > +}
> > +
> > +static void xsk_map_del_node(struct xdp_sock *xs, struct xdp_sock **map_entry)
> > +{
> > +       struct xsk_map_node *n, *tmp;
> > +
> > +       spin_lock_bh(&xs->map_list_lock);
> > +       list_for_each_entry_safe(n, tmp, &xs->map_list, node) {
> > +               if (map_entry == n->map_entry) {
> > +                       list_del(&n->node);
> > +                       xsk_map_node_free(n);
> > +               }
> > +       }
> > +       spin_unlock_bh(&xs->map_list_lock);
> > +
> > +}
> > +
> >  static struct bpf_map *xsk_map_alloc(union bpf_attr *attr)
> >  {
> >         int cpu, err = -EINVAL;
> > @@ -34,6 +84,7 @@ static struct bpf_map *xsk_map_alloc(union bpf_attr *attr)
> >                 return ERR_PTR(-ENOMEM);
> >
> >         bpf_map_init_from_attr(&m->map, attr);
> > +       spin_lock_init(&m->lock);
> >
> >         cost = (u64)m->map.max_entries * sizeof(struct xdp_sock *);
> >         cost += sizeof(struct list_head) * num_possible_cpus();
> > @@ -78,15 +129,16 @@ static void xsk_map_free(struct bpf_map *map)
> >         bpf_clear_redirect_map(map);
> >         synchronize_net();
> >
> > +       spin_lock_bh(&m->lock);
> >         for (i = 0; i < map->max_entries; i++) {
> > -               struct xdp_sock *xs;
> > -
> > -               xs = m->xsk_map[i];
> > -               if (!xs)
> > -                       continue;
> > +               struct xdp_sock **map_entry = &m->xsk_map[i];
> > +               struct xdp_sock *old_xs;
> >
> > -               sock_put((struct sock *)xs);
> > +               old_xs = xchg(map_entry, NULL);
> > +               if (old_xs)
> > +                       xsk_map_del_node(old_xs, map_entry);
> >         }
> > +       spin_unlock_bh(&m->lock);
> >
> >         free_percpu(m->flush_list);
> >         bpf_map_area_free(m->xsk_map);
> > @@ -162,7 +214,8 @@ static int xsk_map_update_elem(struct bpf_map *map, void *key, void *value,
> >  {
> >         struct xsk_map *m = container_of(map, struct xsk_map, map);
> >         u32 i = *(u32 *)key, fd = *(u32 *)value;
> > -       struct xdp_sock *xs, *old_xs;
> > +       struct xdp_sock *xs, *old_xs, **entry;
> > +       struct xsk_map_node *node;
> >         struct socket *sock;
> >         int err;
> >
> > @@ -189,11 +242,20 @@ static int xsk_map_update_elem(struct bpf_map *map, void *key, void *value,
> >                 return -EOPNOTSUPP;
> >         }
> >
> > -       sock_hold(sock->sk);
> > +       node = xsk_map_node_alloc();
> > +       if (!node) {
> > +               sockfd_put(sock);
> > +               return -ENOMEM;
> > +       }
> >
> > -       old_xs = xchg(&m->xsk_map[i], xs);
> > +       spin_lock_bh(&m->lock);
> > +       entry = &m->xsk_map[i];
> > +       xsk_map_node_init(node, m, entry);
> > +       xsk_map_add_node(xs, node);
> > +       old_xs = xchg(entry, xs);
> >         if (old_xs)
> > -               sock_put((struct sock *)old_xs);
> > +               xsk_map_del_node(old_xs, entry);
> > +       spin_unlock_bh(&m->lock);
> >
> >         sockfd_put(sock);
> >         return 0;
> > @@ -202,19 +264,32 @@ static int xsk_map_update_elem(struct bpf_map *map, void *key, void *value,
> >  static int xsk_map_delete_elem(struct bpf_map *map, void *key)
> >  {
> >         struct xsk_map *m = container_of(map, struct xsk_map, map);
> > -       struct xdp_sock *old_xs;
> > +       struct xdp_sock *old_xs, **map_entry;
> >         int k = *(u32 *)key;
> >
> >         if (k >= map->max_entries)
> >                 return -EINVAL;
> >
> > -       old_xs = xchg(&m->xsk_map[k], NULL);
> > +       spin_lock_bh(&m->lock);
> > +       map_entry = &m->xsk_map[k];
> > +       old_xs = xchg(map_entry, NULL);
> >         if (old_xs)
> > -               sock_put((struct sock *)old_xs);
> > +               xsk_map_del_node(old_xs, map_entry);
> > +       spin_unlock_bh(&m->lock);
> >
> >         return 0;
> >  }
> >
> > +void xsk_map_delete_from_node(struct xdp_sock *xs, struct list_head *node)
> > +{
> > +       struct xsk_map_node *n = list_entry(node, struct xsk_map_node, node);
> > +
> > +       spin_lock_bh(&n->map->lock);
> > +       *n->map_entry = NULL;
> > +       spin_unlock_bh(&n->map->lock);
> > +       xsk_map_node_free(n);
> > +}
> > +
> >  const struct bpf_map_ops xsk_map_ops = {
> >         .map_alloc = xsk_map_alloc,
> >         .map_free = xsk_map_free,
> > diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> > index a14e8864e4fa..1931d98a7754 100644
> > --- a/net/xdp/xsk.c
> > +++ b/net/xdp/xsk.c
> > @@ -335,6 +335,27 @@ static int xsk_init_queue(u32 entries, struct xsk_queue **queue,
> >         return 0;
> >  }
> >
> > +static struct list_head *xsk_map_list_pop(struct xdp_sock *xs)
> > +{
> > +       struct list_head *node = NULL;
> > +
> > +       spin_lock_bh(&xs->map_list_lock);
> > +       if (!list_empty(&xs->map_list)) {
> > +               node = xs->map_list.next;
> > +               list_del(node);
> > +       }
> > +       spin_unlock_bh(&xs->map_list_lock);
> > +       return node;
> > +}
> > +
> > +static void xsk_delete_from_maps(struct xdp_sock *xs)
> > +{
> > +       struct list_head *node;
> > +
> > +       while ((node = xsk_map_list_pop(xs)))
> > +               xsk_map_delete_from_node(xs, node);
> > +}
> > +
> >  static int xsk_release(struct socket *sock)
> >  {
> >         struct sock *sk = sock->sk;
> > @@ -354,6 +375,7 @@ static int xsk_release(struct socket *sock)
> >         sock_prot_inuse_add(net, sk->sk_prot, -1);
> >         local_bh_enable();
> >
> > +       xsk_delete_from_maps(xs);
> >         if (xs->dev) {
> >                 struct net_device *dev = xs->dev;
> >
> > @@ -767,6 +789,9 @@ static int xsk_create(struct net *net, struct socket *sock, int protocol,
> >         mutex_init(&xs->mutex);
> >         spin_lock_init(&xs->tx_completion_lock);
> >
> > +       INIT_LIST_HEAD(&xs->map_list);
> > +       spin_lock_init(&xs->map_list_lock);
> > +
> >         mutex_lock(&net->xdp.lock);
> >         sk_add_node_rcu(sk, &net->xdp.list);
> >         mutex_unlock(&net->xdp.lock);
> > --
> > 2.20.1
> >

  reply index

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-22 13:37 [PATCH bpf-next v2 0/2] net: xdp: Two XSKMAP improvements Björn Töpel
2019-05-22 13:37 ` [PATCH bpf-next v2 1/2] xsk: remove AF_XDP socket from map when the socket is released Björn Töpel
2019-06-01 22:32   ` Song Liu
2019-06-03  9:25     ` Björn Töpel [this message]
2019-06-06  9:33       ` Björn Töpel
2019-05-22 13:37 ` [PATCH bpf-next v2 2/2] xsk: support BPF_EXIST and BPF_NOEXIST flags in XSKMAP Björn Töpel

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