NFSD: simplify locking for network notifier.

nfsd currently maintains an open-coded read/write semaphore (refcount
and wait queue) for each network namespace to ensure the nfs service
isn't shut down while the notifier is running.

This is excessive.  As there is unlikely to be contention between
notifiers and they run without sleeping, a single spinlock is sufficient
to avoid problems.

Signed-off-by: NeilBrown <neilb@suse.de>
[ cel: ensure nfsd_notifier_lock is static ]
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h
index 1fd59eb0730bba65ca82f7fccb690ccb127a3511..021acdc0d03bb89ffea3763a78e4a6dda03518ad 100644 (file)
--- a/fs/nfsd/netns.h
+++ b/fs/nfsd/netns.h
@@ -131,9 +131,6 @@ struct nfsd_net {
         */
        int keep_active;
 
-       wait_queue_head_t ntf_wq;
-       atomic_t ntf_refcnt;
-
        /*
         * clientid and stateid data for construction of net unique COPY
         * stateids.

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 7b557eb8211a052a649617afc6e17cefa0c7038c..a8ad71567fc72640af8ffa681a7216e7b4e26cfd 100644 (file)
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -1483,8 +1483,6 @@ static __net_init int nfsd_init_net(struct net *net)
        nn->clientid_counter = nn->clientid_base + 1;
        nn->s2s_cp_cl_id = nn->clientid_counter++;
 
-       atomic_set(&nn->ntf_refcnt, 0);
-       init_waitqueue_head(&nn->ntf_wq);
        seqlock_init(&nn->boot_lock);
 
        return 0;

diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index 020156e96bdb507ab4ad591f900d906fdd6a36d8..14c1ef6f8cc7451edf3250ae17d5d0881a8e0813 100644 (file)
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -434,6 +434,7 @@ static void nfsd_shutdown_net(struct net *net)
        nfsd_shutdown_generic();
 }
 
+static DEFINE_SPINLOCK(nfsd_notifier_lock);
 static int nfsd_inetaddr_event(struct notifier_block *this, unsigned long event,
        void *ptr)
 {
@@ -443,18 +444,17 @@ static int nfsd_inetaddr_event(struct notifier_block *this, unsigned long event,
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);
        struct sockaddr_in sin;
 
-       if ((event != NETDEV_DOWN) ||
-           !atomic_inc_not_zero(&nn->ntf_refcnt))
+       if (event != NETDEV_DOWN || !nn->nfsd_serv)
                goto out;
 
+       spin_lock(&nfsd_notifier_lock);
        if (nn->nfsd_serv) {
                dprintk("nfsd_inetaddr_event: removed %pI4\n", &ifa->ifa_local);
                sin.sin_family = AF_INET;
                sin.sin_addr.s_addr = ifa->ifa_local;
                svc_age_temp_xprts_now(nn->nfsd_serv, (struct sockaddr *)&sin);
        }
-       atomic_dec(&nn->ntf_refcnt);
-       wake_up(&nn->ntf_wq);
+       spin_unlock(&nfsd_notifier_lock);
 
 out:
        return NOTIFY_DONE;
@@ -474,10 +474,10 @@ static int nfsd_inet6addr_event(struct notifier_block *this,
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);
        struct sockaddr_in6 sin6;
 
-       if ((event != NETDEV_DOWN) ||
-           !atomic_inc_not_zero(&nn->ntf_refcnt))
+       if (event != NETDEV_DOWN || !nn->nfsd_serv)
                goto out;
 
+       spin_lock(&nfsd_notifier_lock);
        if (nn->nfsd_serv) {
                dprintk("nfsd_inet6addr_event: removed %pI6\n", &ifa->addr);
                sin6.sin6_family = AF_INET6;
@@ -486,8 +486,8 @@ static int nfsd_inet6addr_event(struct notifier_block *this,
                        sin6.sin6_scope_id = ifa->idev->dev->ifindex;
                svc_age_temp_xprts_now(nn->nfsd_serv, (struct sockaddr *)&sin6);
        }
-       atomic_dec(&nn->ntf_refcnt);
-       wake_up(&nn->ntf_wq);
+       spin_unlock(&nfsd_notifier_lock);
+
 out:
        return NOTIFY_DONE;
 }
@@ -504,7 +504,6 @@ static void nfsd_last_thread(struct svc_serv *serv, struct net *net)
 {
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 
-       atomic_dec(&nn->ntf_refcnt);
        /* check if the notifier still has clients */
        if (atomic_dec_return(&nfsd_notifier_refcount) == 0) {
                unregister_inetaddr_notifier(&nfsd_inetaddr_notifier);
@@ -512,7 +511,6 @@ static void nfsd_last_thread(struct svc_serv *serv, struct net *net)
                unregister_inet6addr_notifier(&nfsd_inet6addr_notifier);
 #endif
        }
-       wait_event(nn->ntf_wq, atomic_read(&nn->ntf_refcnt) == 0);
 
        /*
         * write_ports can create the server without actually starting
@@ -624,6 +622,7 @@ int nfsd_create_serv(struct net *net)
 {
        int error;
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+       struct svc_serv *serv;
 
        WARN_ON(!mutex_is_locked(&nfsd_mutex));
        if (nn->nfsd_serv) {
@@ -633,21 +632,23 @@ int nfsd_create_serv(struct net *net)
        if (nfsd_max_blksize == 0)
                nfsd_max_blksize = nfsd_get_default_max_blksize();
        nfsd_reset_versions(nn);
-       nn->nfsd_serv = svc_create_pooled(&nfsd_program, nfsd_max_blksize,
-                                               &nfsd_thread_sv_ops);
-       if (nn->nfsd_serv == NULL)
+       serv = svc_create_pooled(&nfsd_program, nfsd_max_blksize,
+                                &nfsd_thread_sv_ops);
+       if (serv == NULL)
                return -ENOMEM;
 
-       nn->nfsd_serv->sv_maxconn = nn->max_connections;
-       error = svc_bind(nn->nfsd_serv, net);
+       serv->sv_maxconn = nn->max_connections;
+       error = svc_bind(serv, net);
        if (error < 0) {
                /* NOT nfsd_put() as notifiers (see below) haven't
                 * been set up yet.
                 */
-               svc_put(nn->nfsd_serv);
-               nn->nfsd_serv = NULL;
+               svc_put(serv);
                return error;
        }
+       spin_lock(&nfsd_notifier_lock);
+       nn->nfsd_serv = serv;
+       spin_unlock(&nfsd_notifier_lock);
 
        set_max_drc();
        /* check if the notifier is already set */
@@ -657,7 +658,6 @@ int nfsd_create_serv(struct net *net)
                register_inet6addr_notifier(&nfsd_inet6addr_notifier);
 #endif
        }
-       atomic_inc(&nn->ntf_refcnt);
        nfsd_reset_boot_verifier(nn);
        return 0;
 }
@@ -701,7 +701,9 @@ void nfsd_put(struct net *net)
        if (kref_put(&nn->nfsd_serv->sv_refcnt, nfsd_noop)) {
                svc_shutdown_net(nn->nfsd_serv, net);
                svc_destroy(&nn->nfsd_serv->sv_refcnt);
+               spin_lock(&nfsd_notifier_lock);
                nn->nfsd_serv = NULL;
+               spin_unlock(&nfsd_notifier_lock);
        }
 }