nfsd4: don't destroy in-use session

This changes session destruction to be similar to client destruction in
that attempts to destroy a session while in use (which should be rare
corner cases) result in DELAY.  This simplifies things somewhat and
helps meet a coming 4.2 requirement.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 3b4ce41..2fd0155 100644 (file)
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -94,17 +94,32 @@ nfs4_lock_state(void)
        mutex_lock(&client_mutex);
 }
 
-static void free_session(struct kref *);
+static void free_session(struct nfsd4_session *);
 
-/* Must be called under the client_lock */
-static void nfsd4_put_session_locked(struct nfsd4_session *ses)
+void nfsd4_put_session(struct nfsd4_session *ses)
+{
+       atomic_dec(&ses->se_ref);
+}
+
+static bool is_session_dead(struct nfsd4_session *ses)
 {
-       kref_put(&ses->se_ref, free_session);
+       return ses->se_flags & NFS4_SESSION_DEAD;
+}
+
+static __be32 mark_session_dead_locked(struct nfsd4_session *ses)
+{
+       if (atomic_read(&ses->se_ref))
+               return nfserr_jukebox;
+       ses->se_flags |= NFS4_SESSION_DEAD;
+       return nfs_ok;
 }
 
-static void nfsd4_get_session(struct nfsd4_session *ses)
+static __be32 nfsd4_get_session_locked(struct nfsd4_session *ses)
 {
-       kref_get(&ses->se_ref);
+       if (is_session_dead(ses))
+               return nfserr_badsession;
+       atomic_inc(&ses->se_ref);
+       return nfs_ok;
 }
 
 void
@@ -935,28 +950,15 @@ static void __free_session(struct nfsd4_session *ses)
        kfree(ses);
 }
 
-static void free_session(struct kref *kref)
+static void free_session(struct nfsd4_session *ses)
 {
-       struct nfsd4_session *ses;
-       struct nfsd_net *nn;
-
-       ses = container_of(kref, struct nfsd4_session, se_ref);
-       nn = net_generic(ses->se_client->net, nfsd_net_id);
+       struct nfsd_net *nn = net_generic(ses->se_client->net, nfsd_net_id);
 
        lockdep_assert_held(&nn->client_lock);
        nfsd4_del_conns(ses);
        __free_session(ses);
 }
 
-void nfsd4_put_session(struct nfsd4_session *ses)
-{
-       struct nfsd_net *nn = net_generic(ses->se_client->net, nfsd_net_id);
-
-       spin_lock(&nn->client_lock);
-       nfsd4_put_session_locked(ses);
-       spin_unlock(&nn->client_lock);
-}
-
 static struct nfsd4_session *alloc_session(struct nfsd4_channel_attrs *fchan,
                                           struct nfsd_net *nn)
 {
@@ -997,7 +999,7 @@ static void init_session(struct svc_rqst *rqstp, struct nfsd4_session *new, stru
        new->se_flags = cses->flags;
        new->se_cb_prog = cses->callback_prog;
        new->se_cb_sec = cses->cb_sec;
-       kref_init(&new->se_ref);
+       atomic_set(&new->se_ref, 0);
        idx = hash_sessionid(&new->se_sessionid);
        spin_lock(&nn->client_lock);
        list_add(&new->se_hash, &nn->sessionid_hashtbl[idx]);
@@ -1095,7 +1097,8 @@ free_client(struct nfs4_client *clp)
                ses = list_entry(clp->cl_sessions.next, struct nfsd4_session,
                                se_perclnt);
                list_del(&ses->se_perclnt);
-               nfsd4_put_session_locked(ses);
+               WARN_ON_ONCE(atomic_read(&ses->se_ref));
+               free_session(ses);
        }
        free_svc_cred(&clp->cl_cred);
        kfree(clp->cl_name.data);
@@ -1976,15 +1979,16 @@ nfsd4_destroy_session(struct svc_rqst *r,
        status = nfserr_badsession;
        if (!ses)
                goto out_client_lock;
-
+       status = mark_session_dead_locked(ses);
+       if (status)
+               goto out_client_lock;
        unhash_session(ses);
        spin_unlock(&nn->client_lock);
 
        nfsd4_probe_callback_sync(ses->se_client);
 
        spin_lock(&nn->client_lock);
-       nfsd4_del_conns(ses);
-       nfsd4_put_session_locked(ses);
+       free_session(ses);
        status = nfs_ok;
 out_client_lock:
        spin_unlock(&nn->client_lock);
@@ -2075,18 +2079,21 @@ nfsd4_sequence(struct svc_rqst *rqstp,
        status = get_client_locked(clp);
        if (status)
                goto out_no_session;
+       status = nfsd4_get_session_locked(session);
+       if (status)
+               goto out_put_client;
 
        status = nfserr_too_many_ops;
        if (nfsd4_session_too_many_ops(rqstp, session))
-               goto out_put_client;
+               goto out_put_session;
 
        status = nfserr_req_too_big;
        if (nfsd4_request_too_big(rqstp, session))
-               goto out_put_client;
+               goto out_put_session;
 
        status = nfserr_badslot;
        if (seq->slotid >= session->se_fchannel.maxreqs)
-               goto out_put_client;
+               goto out_put_session;
 
        slot = session->se_slots[seq->slotid];
        dprintk("%s: slotid %d\n", __func__, seq->slotid);
@@ -2101,7 +2108,7 @@ nfsd4_sequence(struct svc_rqst *rqstp,
        if (status == nfserr_replay_cache) {
                status = nfserr_seq_misordered;
                if (!(slot->sl_flags & NFSD4_SLOT_INITIALIZED))
-                       goto out_put_client;
+                       goto out_put_session;
                cstate->slot = slot;
                cstate->session = session;
                /* Return the cached reply status and set cstate->status
@@ -2111,7 +2118,7 @@ nfsd4_sequence(struct svc_rqst *rqstp,
                goto out;
        }
        if (status)
-               goto out_put_client;
+               goto out_put_session;
 
        nfsd4_sequence_check_conn(conn, session);
        conn = NULL;
@@ -2128,7 +2135,6 @@ nfsd4_sequence(struct svc_rqst *rqstp,
        cstate->session = session;
 
 out:
-       nfsd4_get_session(cstate->session);
        switch (clp->cl_cb_state) {
        case NFSD4_CB_DOWN:
                seq->status_flags = SEQ4_STATUS_CB_PATH_DOWN;
@@ -2143,6 +2149,8 @@ out_no_session:
        kfree(conn);
        spin_unlock(&nn->client_lock);
        return status;
+out_put_session:
+       nfsd4_put_session(session);
 out_put_client:
        put_client_renew_locked(clp);
        goto out_no_session;

diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
index 07f8a82..f6ae4db 100644 (file)
--- a/fs/nfsd/state.h
+++ b/fs/nfsd/state.h
@@ -194,9 +194,11 @@ struct nfsd4_conn {
 };
 
 struct nfsd4_session {
-       struct kref             se_ref;
+       atomic_t                se_ref;
        struct list_head        se_hash;        /* hash by sessionid */
        struct list_head        se_perclnt;
+/* See SESSION4_PERSIST, etc. for standard flags; this is internal-only: */
+#define NFS4_SESSION_DEAD      0x010
        u32                     se_flags;
        struct nfs4_client      *se_client;
        struct nfs4_sessionid   se_sessionid;