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    Subject[PATCH v7 bpf-next 02/11] tcp: Add num_closed_socks to struct sock_reuseport.
    Date
    As noted in the following commit, a closed listener has to hold the
    reference to the reuseport group for socket migration. This patch adds a
    field (num_closed_socks) to struct sock_reuseport to manage closed sockets
    within the same reuseport group. Moreover, this and the following commits
    introduce some helper functions to split socks[] into two sections and keep
    TCP_LISTEN and TCP_CLOSE sockets in each section. Like a double-ended
    queue, we will place TCP_LISTEN sockets from the front and TCP_CLOSE
    sockets from the end.

    TCP_LISTEN----------> <-------TCP_CLOSE
    +---+---+ --- +---+ --- +---+ --- +---+
    | 0 | 1 | ... | i | ... | j | ... | k |
    +---+---+ --- +---+ --- +---+ --- +---+

    i = num_socks - 1
    j = max_socks - num_closed_socks
    k = max_socks - 1

    This patch also extends reuseport_add_sock() and reuseport_grow() to
    support num_closed_socks.

    Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
    Acked-by: Martin KaFai Lau <kafai@fb.com>
    ---
    include/net/sock_reuseport.h | 5 ++-
    net/core/sock_reuseport.c | 76 +++++++++++++++++++++++++++---------
    2 files changed, 60 insertions(+), 21 deletions(-)

    diff --git a/include/net/sock_reuseport.h b/include/net/sock_reuseport.h
    index 505f1e18e9bf..0e558ca7afbf 100644
    --- a/include/net/sock_reuseport.h
    +++ b/include/net/sock_reuseport.h
    @@ -13,8 +13,9 @@ extern spinlock_t reuseport_lock;
    struct sock_reuseport {
    struct rcu_head rcu;

    - u16 max_socks; /* length of socks */
    - u16 num_socks; /* elements in socks */
    + u16 max_socks; /* length of socks */
    + u16 num_socks; /* elements in socks */
    + u16 num_closed_socks; /* closed elements in socks */
    /* The last synq overflow event timestamp of this
    * reuse->socks[] group.
    */
    diff --git a/net/core/sock_reuseport.c b/net/core/sock_reuseport.c
    index b065f0a103ed..079bd1aca0e7 100644
    --- a/net/core/sock_reuseport.c
    +++ b/net/core/sock_reuseport.c
    @@ -18,6 +18,49 @@ DEFINE_SPINLOCK(reuseport_lock);

    static DEFINE_IDA(reuseport_ida);

    +static int reuseport_sock_index(struct sock *sk,
    + struct sock_reuseport *reuse,
    + bool closed)
    +{
    + int left, right;
    +
    + if (!closed) {
    + left = 0;
    + right = reuse->num_socks;
    + } else {
    + left = reuse->max_socks - reuse->num_closed_socks;
    + right = reuse->max_socks;
    + }
    +
    + for (; left < right; left++)
    + if (reuse->socks[left] == sk)
    + return left;
    + return -1;
    +}
    +
    +static void __reuseport_add_sock(struct sock *sk,
    + struct sock_reuseport *reuse)
    +{
    + reuse->socks[reuse->num_socks] = sk;
    + /* paired with smp_rmb() in reuseport_select_sock() */
    + smp_wmb();
    + reuse->num_socks++;
    +}
    +
    +static bool __reuseport_detach_sock(struct sock *sk,
    + struct sock_reuseport *reuse)
    +{
    + int i = reuseport_sock_index(sk, reuse, false);
    +
    + if (i == -1)
    + return false;
    +
    + reuse->socks[i] = reuse->socks[reuse->num_socks - 1];
    + reuse->num_socks--;
    +
    + return true;
    +}
    +
    static struct sock_reuseport *__reuseport_alloc(unsigned int max_socks)
    {
    unsigned int size = sizeof(struct sock_reuseport) +
    @@ -72,9 +115,8 @@ int reuseport_alloc(struct sock *sk, bool bind_inany)
    }

    reuse->reuseport_id = id;
    - reuse->socks[0] = sk;
    - reuse->num_socks = 1;
    reuse->bind_inany = bind_inany;
    + __reuseport_add_sock(sk, reuse);
    rcu_assign_pointer(sk->sk_reuseport_cb, reuse);

    out:
    @@ -98,6 +140,7 @@ static struct sock_reuseport *reuseport_grow(struct sock_reuseport *reuse)
    return NULL;

    more_reuse->num_socks = reuse->num_socks;
    + more_reuse->num_closed_socks = reuse->num_closed_socks;
    more_reuse->prog = reuse->prog;
    more_reuse->reuseport_id = reuse->reuseport_id;
    more_reuse->bind_inany = reuse->bind_inany;
    @@ -105,9 +148,13 @@ static struct sock_reuseport *reuseport_grow(struct sock_reuseport *reuse)

    memcpy(more_reuse->socks, reuse->socks,
    reuse->num_socks * sizeof(struct sock *));
    + memcpy(more_reuse->socks +
    + (more_reuse->max_socks - more_reuse->num_closed_socks),
    + reuse->socks + reuse->num_socks,
    + reuse->num_closed_socks * sizeof(struct sock *));
    more_reuse->synq_overflow_ts = READ_ONCE(reuse->synq_overflow_ts);

    - for (i = 0; i < reuse->num_socks; ++i)
    + for (i = 0; i < reuse->max_socks; ++i)
    rcu_assign_pointer(reuse->socks[i]->sk_reuseport_cb,
    more_reuse);

    @@ -158,7 +205,7 @@ int reuseport_add_sock(struct sock *sk, struct sock *sk2, bool bind_inany)
    return -EBUSY;
    }

    - if (reuse->num_socks == reuse->max_socks) {
    + if (reuse->num_socks + reuse->num_closed_socks == reuse->max_socks) {
    reuse = reuseport_grow(reuse);
    if (!reuse) {
    spin_unlock_bh(&reuseport_lock);
    @@ -166,10 +213,7 @@ int reuseport_add_sock(struct sock *sk, struct sock *sk2, bool bind_inany)
    }
    }

    - reuse->socks[reuse->num_socks] = sk;
    - /* paired with smp_rmb() in reuseport_select_sock() */
    - smp_wmb();
    - reuse->num_socks++;
    + __reuseport_add_sock(sk, reuse);
    rcu_assign_pointer(sk->sk_reuseport_cb, reuse);

    spin_unlock_bh(&reuseport_lock);
    @@ -183,7 +227,6 @@ EXPORT_SYMBOL(reuseport_add_sock);
    void reuseport_detach_sock(struct sock *sk)
    {
    struct sock_reuseport *reuse;
    - int i;

    spin_lock_bh(&reuseport_lock);
    reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
    @@ -200,16 +243,11 @@ void reuseport_detach_sock(struct sock *sk)
    bpf_sk_reuseport_detach(sk);

    rcu_assign_pointer(sk->sk_reuseport_cb, NULL);
    + __reuseport_detach_sock(sk, reuse);
    +
    + if (reuse->num_socks + reuse->num_closed_socks == 0)
    + call_rcu(&reuse->rcu, reuseport_free_rcu);

    - for (i = 0; i < reuse->num_socks; i++) {
    - if (reuse->socks[i] == sk) {
    - reuse->socks[i] = reuse->socks[reuse->num_socks - 1];
    - reuse->num_socks--;
    - if (reuse->num_socks == 0)
    - call_rcu(&reuse->rcu, reuseport_free_rcu);
    - break;
    - }
    - }
    spin_unlock_bh(&reuseport_lock);
    }
    EXPORT_SYMBOL(reuseport_detach_sock);
    @@ -274,7 +312,7 @@ struct sock *reuseport_select_sock(struct sock *sk,
    prog = rcu_dereference(reuse->prog);
    socks = READ_ONCE(reuse->num_socks);
    if (likely(socks)) {
    - /* paired with smp_wmb() in reuseport_add_sock() */
    + /* paired with smp_wmb() in __reuseport_add_sock() */
    smp_rmb();

    if (!prog || !skb)
    --
    2.30.2
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