queue-5.15/nfsd-simplify-locking-for-network-notifier.patch

   1 From 9b3db1e18b4fb74efea1110fbb757aaa240559c0 Mon Sep 17 00:00:00 2001
   2 From: Sasha Levin <sashal@kernel.org>
   3 Date: Mon, 29 Nov 2021 15:51:25 +1100
   4 Subject: NFSD: simplify locking for network notifier.
   5
   6 From: NeilBrown <neilb@suse.de>
   7
   8 [ Upstream commit d057cfec4940ce6eeffa22b4a71dec203b06cd55 ]
   9
  10 nfsd currently maintains an open-coded read/write semaphore (refcount
  11 and wait queue) for each network namespace to ensure the nfs service
  12 isn't shut down while the notifier is running.
  13
  14 This is excessive.  As there is unlikely to be contention between
  15 notifiers and they run without sleeping, a single spinlock is sufficient
  16 to avoid problems.
  17
  18 Signed-off-by: NeilBrown <neilb@suse.de>
  19 [ cel: ensure nfsd_notifier_lock is static ]
  20 Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
  21 ---
  22  fs/nfsd/netns.h  |  3 ---
  23  fs/nfsd/nfsctl.c |  2 --
  24  fs/nfsd/nfssvc.c | 38 ++++++++++++++++++++------------------
  25  3 files changed, 20 insertions(+), 23 deletions(-)
  26
  27 diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h
  28 index 1fd59eb0730bb..021acdc0d03bb 100644
  29 --- a/fs/nfsd/netns.h
  30 +++ b/fs/nfsd/netns.h
  31 @@ -131,9 +131,6 @@ struct nfsd_net {
  32          */
  33         int keep_active;
  34
  35 -       wait_queue_head_t ntf_wq;
  36 -       atomic_t ntf_refcnt;
  37 -
  38         /*
  39          * clientid and stateid data for construction of net unique COPY
  40          * stateids.
  41 diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
  42 index 53076c5afe62c..504b169d27881 100644
  43 --- a/fs/nfsd/nfsctl.c
  44 +++ b/fs/nfsd/nfsctl.c
  45 @@ -1484,8 +1484,6 @@ static __net_init int nfsd_init_net(struct net *net)
  46         nn->clientid_counter = nn->clientid_base + 1;
  47         nn->s2s_cp_cl_id = nn->clientid_counter++;
  48
  49 -       atomic_set(&nn->ntf_refcnt, 0);
  50 -       init_waitqueue_head(&nn->ntf_wq);
  51         seqlock_init(&nn->boot_lock);
  52
  53         return 0;
  54 diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
  55 index 8d49dfbe03f85..8554bc7ff4322 100644
  56 --- a/fs/nfsd/nfssvc.c
  57 +++ b/fs/nfsd/nfssvc.c
  58 @@ -434,6 +434,7 @@ static void nfsd_shutdown_net(struct net *net)
  59         nfsd_shutdown_generic();
  60  }
  61
  62 +static DEFINE_SPINLOCK(nfsd_notifier_lock);
  63  static int nfsd_inetaddr_event(struct notifier_block *this, unsigned long event,
  64         void *ptr)
  65  {
  66 @@ -443,18 +444,17 @@ static int nfsd_inetaddr_event(struct notifier_block *this, unsigned long event,
  67         struct nfsd_net *nn = net_generic(net, nfsd_net_id);
  68         struct sockaddr_in sin;
  69
  70 -       if ((event != NETDEV_DOWN) ||
  71 -           !atomic_inc_not_zero(&nn->ntf_refcnt))
  72 +       if (event != NETDEV_DOWN || !nn->nfsd_serv)
  73                 goto out;
  74
  75 +       spin_lock(&nfsd_notifier_lock);
  76         if (nn->nfsd_serv) {
  77                 dprintk("nfsd_inetaddr_event: removed %pI4\n", &ifa->ifa_local);
  78                 sin.sin_family = AF_INET;
  79                 sin.sin_addr.s_addr = ifa->ifa_local;
  80                 svc_age_temp_xprts_now(nn->nfsd_serv, (struct sockaddr *)&sin);
  81         }
  82 -       atomic_dec(&nn->ntf_refcnt);
  83 -       wake_up(&nn->ntf_wq);
  84 +       spin_unlock(&nfsd_notifier_lock);
  85
  86  out:
  87         return NOTIFY_DONE;
  88 @@ -474,10 +474,10 @@ static int nfsd_inet6addr_event(struct notifier_block *this,
  89         struct nfsd_net *nn = net_generic(net, nfsd_net_id);
  90         struct sockaddr_in6 sin6;
  91
  92 -       if ((event != NETDEV_DOWN) ||
  93 -           !atomic_inc_not_zero(&nn->ntf_refcnt))
  94 +       if (event != NETDEV_DOWN || !nn->nfsd_serv)
  95                 goto out;
  96
  97 +       spin_lock(&nfsd_notifier_lock);
  98         if (nn->nfsd_serv) {
  99                 dprintk("nfsd_inet6addr_event: removed %pI6\n", &ifa->addr);
 100                 sin6.sin6_family = AF_INET6;
 101 @@ -486,8 +486,8 @@ static int nfsd_inet6addr_event(struct notifier_block *this,
 102                         sin6.sin6_scope_id = ifa->idev->dev->ifindex;
 103                 svc_age_temp_xprts_now(nn->nfsd_serv, (struct sockaddr *)&sin6);
 104         }
 105 -       atomic_dec(&nn->ntf_refcnt);
 106 -       wake_up(&nn->ntf_wq);
 107 +       spin_unlock(&nfsd_notifier_lock);
 108 +
 109  out:
 110         return NOTIFY_DONE;
 111  }
 112 @@ -504,7 +504,6 @@ static void nfsd_last_thread(struct svc_serv *serv, struct net *net)
 113  {
 114         struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 115
 116 -       atomic_dec(&nn->ntf_refcnt);
 117         /* check if the notifier still has clients */
 118         if (atomic_dec_return(&nfsd_notifier_refcount) == 0) {
 119                 unregister_inetaddr_notifier(&nfsd_inetaddr_notifier);
 120 @@ -512,7 +511,6 @@ static void nfsd_last_thread(struct svc_serv *serv, struct net *net)
 121                 unregister_inet6addr_notifier(&nfsd_inet6addr_notifier);
 122  #endif
 123         }
 124 -       wait_event(nn->ntf_wq, atomic_read(&nn->ntf_refcnt) == 0);
 125
 126         /*
 127          * write_ports can create the server without actually starting
 128 @@ -624,6 +622,7 @@ int nfsd_create_serv(struct net *net)
 129  {
 130         int error;
 131         struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 132 +       struct svc_serv *serv;
 133
 134         WARN_ON(!mutex_is_locked(&nfsd_mutex));
 135         if (nn->nfsd_serv) {
 136 @@ -633,21 +632,23 @@ int nfsd_create_serv(struct net *net)
 137         if (nfsd_max_blksize == 0)
 138                 nfsd_max_blksize = nfsd_get_default_max_blksize();
 139         nfsd_reset_versions(nn);
 140 -       nn->nfsd_serv = svc_create_pooled(&nfsd_program, nfsd_max_blksize,
 141 -                                               &nfsd_thread_sv_ops);
 142 -       if (nn->nfsd_serv == NULL)
 143 +       serv = svc_create_pooled(&nfsd_program, nfsd_max_blksize,
 144 +                                &nfsd_thread_sv_ops);
 145 +       if (serv == NULL)
 146                 return -ENOMEM;
 147
 148 -       nn->nfsd_serv->sv_maxconn = nn->max_connections;
 149 -       error = svc_bind(nn->nfsd_serv, net);
 150 +       serv->sv_maxconn = nn->max_connections;
 151 +       error = svc_bind(serv, net);
 152         if (error < 0) {
 153                 /* NOT nfsd_put() as notifiers (see below) haven't
 154                  * been set up yet.
 155                  */
 156 -               svc_put(nn->nfsd_serv);
 157 -               nn->nfsd_serv = NULL;
 158 +               svc_put(serv);
 159                 return error;
 160         }
 161 +       spin_lock(&nfsd_notifier_lock);
 162 +       nn->nfsd_serv = serv;
 163 +       spin_unlock(&nfsd_notifier_lock);
 164
 165         set_max_drc();
 166         /* check if the notifier is already set */
 167 @@ -657,7 +658,6 @@ int nfsd_create_serv(struct net *net)
 168                 register_inet6addr_notifier(&nfsd_inet6addr_notifier);
 169  #endif
 170         }
 171 -       atomic_inc(&nn->ntf_refcnt);
 172         nfsd_reset_boot_verifier(nn);
 173         return 0;
 174  }
 175 @@ -701,7 +701,9 @@ void nfsd_put(struct net *net)
 176         if (kref_put(&nn->nfsd_serv->sv_refcnt, nfsd_noop)) {
 177                 svc_shutdown_net(nn->nfsd_serv, net);
 178                 svc_destroy(&nn->nfsd_serv->sv_refcnt);
 179 +               spin_lock(&nfsd_notifier_lock);
 180                 nn->nfsd_serv = NULL;
 181 +               spin_unlock(&nfsd_notifier_lock);
 182         }
 183  }
 184
 185 --
 186 2.43.0
 187