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    Subject[PATCH 4.4 014/190] lockd: fix lockd shutdown race
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: "J. Bruce Fields" <bfields@redhat.com>


    [ Upstream commit efda760fe95ea15291853c8fa9235c32d319cd98 ]

    As reported by David Jeffery: "a signal was sent to lockd while lockd
    was shutting down from a request to stop nfs. The signal causes lockd
    to call restart_grace() which puts the lockd_net structure on the grace
    list. If this signal is received at the wrong time, it will occur after
    lockd_down_net() has called locks_end_grace() but before
    lockd_down_net() stops the lockd thread. This leads to lockd putting
    the lockd_net structure back on the grace list, then exiting without
    anything removing it from the list."

    So, perform the final locks_end_grace() from the the lockd thread; this
    ensures it's serialized with respect to restart_grace().

    Reported-by: David Jeffery <djeffery@redhat.com>
    Signed-off-by: J. Bruce Fields <bfields@redhat.com>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    fs/lockd/svc.c | 6 ++++--
    1 file changed, 4 insertions(+), 2 deletions(-)

    --- a/fs/lockd/svc.c
    +++ b/fs/lockd/svc.c
    @@ -129,6 +129,8 @@ lockd(void *vrqstp)
    {
    int err = 0;
    struct svc_rqst *rqstp = vrqstp;
    + struct net *net = &init_net;
    + struct lockd_net *ln = net_generic(net, lockd_net_id);

    /* try_to_freeze() is called from svc_recv() */
    set_freezable();
    @@ -173,6 +175,8 @@ lockd(void *vrqstp)
    if (nlmsvc_ops)
    nlmsvc_invalidate_all();
    nlm_shutdown_hosts();
    + cancel_delayed_work_sync(&ln->grace_period_end);
    + locks_end_grace(&ln->lockd_manager);
    return 0;
    }

    @@ -267,8 +271,6 @@ static void lockd_down_net(struct svc_se
    if (ln->nlmsvc_users) {
    if (--ln->nlmsvc_users == 0) {
    nlm_shutdown_hosts_net(net);
    - cancel_delayed_work_sync(&ln->grace_period_end);
    - locks_end_grace(&ln->lockd_manager);
    svc_shutdown_net(serv, net);
    dprintk("lockd_down_net: per-net data destroyed; net=%p\n", net);
    }

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