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lockd: fix lockd shutdown race

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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>
This commit is contained in:
J. Bruce Fields 2017-03-28 21:25:08 -04:00
parent ed6473ddc7
commit efda760fe9
1 changed files with 4 additions and 2 deletions
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6
fs/lockd/svc.c
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@ -132,6 +132,8 @@ 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();
@ -176,6 +178,8 @@ 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;
}
@ -270,8 +274,6 @@ static void lockd_down_net(struct svc_serv *serv, struct net *net)
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);
}