mptcp: Avoid acquiring PM lock for subflow priority changes

The in-kernel path manager code for changing subflow flags acquired both
the msk socket lock and the PM lock when possibly changing the "backup"
and "fullmesh" flags. mptcp_pm_nl_mp_prio_send_ack() does not access
anything protected by the PM lock, and it must release and reacquire
the PM lock.

By pushing the PM lock to where it is needed in mptcp_pm_nl_fullmesh(),
the lock is only acquired when the fullmesh flag is changed and the
backup flag code no longer has to release and reacquire the PM lock. The
change in locking context requires the MIB update to be modified - move
that to a better location instead.

This change also makes it possible to call
mptcp_pm_nl_mp_prio_send_ack() for the userspace PM commands without
manipulating the in-kernel PM lock.

Fixes: 0f9f696a502e ("mptcp: add set_flags command in PM netlink")
Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index aead331866a0ce8612b418f9c0e25f3a6946ef77..bd8f0f425be4ca1d09076a054da1f9e8accf363b 100644 (file)
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -1584,6 +1584,9 @@ mp_rst:
                *ptr++ = mptcp_option(MPTCPOPT_MP_PRIO,
                                      TCPOLEN_MPTCP_PRIO,
                                      opts->backup, TCPOPT_NOP);
+
+               MPTCP_INC_STATS(sock_net((const struct sock *)tp),
+                               MPTCP_MIB_MPPRIOTX);
        }
 
 mp_capable_done:

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index e099f2a12504a78edff538c9160e2d97d9203593..5ff93b73f33d04c34cc1cff815741cf68d4d54a0 100644 (file)
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -727,7 +727,6 @@ static int mptcp_pm_nl_mp_prio_send_ack(struct mptcp_sock *msk,
 
        mptcp_for_each_subflow(msk, subflow) {
                struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
-               struct sock *sk = (struct sock *)msk;
                struct mptcp_addr_info local;
 
                local_address((struct sock_common *)ssk, &local);
@@ -739,12 +738,9 @@ static int mptcp_pm_nl_mp_prio_send_ack(struct mptcp_sock *msk,
                subflow->backup = bkup;
                subflow->send_mp_prio = 1;
                subflow->request_bkup = bkup;
-               __MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPPRIOTX);
 
-               spin_unlock_bh(&msk->pm.lock);
                pr_debug("send ack for mp_prio");
                mptcp_subflow_send_ack(ssk);
-               spin_lock_bh(&msk->pm.lock);
 
                return 0;
        }
@@ -1816,8 +1812,10 @@ static void mptcp_pm_nl_fullmesh(struct mptcp_sock *msk,
 
        list.ids[list.nr++] = addr->id;
 
+       spin_lock_bh(&msk->pm.lock);
        mptcp_pm_nl_rm_subflow_received(msk, &list);
        mptcp_pm_create_subflow_or_signal_addr(msk);
+       spin_unlock_bh(&msk->pm.lock);
 }
 
 static int mptcp_nl_set_flags(struct net *net,
@@ -1835,12 +1833,10 @@ static int mptcp_nl_set_flags(struct net *net,
                        goto next;
 
                lock_sock(sk);
-               spin_lock_bh(&msk->pm.lock);
                if (changed & MPTCP_PM_ADDR_FLAG_BACKUP)
                        ret = mptcp_pm_nl_mp_prio_send_ack(msk, addr, bkup);
                if (changed & MPTCP_PM_ADDR_FLAG_FULLMESH)
                        mptcp_pm_nl_fullmesh(msk, addr);
-               spin_unlock_bh(&msk->pm.lock);
                release_sock(sk);
 
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