nfsd: Don't get a session reference without a client reference

If the client were to disappear from underneath us while we're holding
a session reference, things would be bad. This cleanup helps ensure
that it cannot, which will be a possibility when the client_mutex is
removed.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 86ec359..29d1ddc 100644 (file)
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -103,12 +103,6 @@ static bool is_session_dead(struct nfsd4_session *ses)
        return ses->se_flags & NFS4_SESSION_DEAD;
 }
 
-void nfsd4_put_session(struct nfsd4_session *ses)
-{
-       if (atomic_dec_and_test(&ses->se_ref) && is_session_dead(ses))
-               free_session(ses);
-}
-
 static __be32 mark_session_dead_locked(struct nfsd4_session *ses, int ref_held_by_me)
 {
        if (atomic_read(&ses->se_ref) > ref_held_by_me)
@@ -117,14 +111,6 @@ static __be32 mark_session_dead_locked(struct nfsd4_session *ses, int ref_held_b
        return nfs_ok;
 }
 
-static __be32 nfsd4_get_session_locked(struct nfsd4_session *ses)
-{
-       if (is_session_dead(ses))
-               return nfserr_badsession;
-       atomic_inc(&ses->se_ref);
-       return nfs_ok;
-}
-
 void
 nfs4_unlock_state(void)
 {
@@ -203,6 +189,39 @@ static void put_client_renew_locked(struct nfs4_client *clp)
                renew_client_locked(clp);
 }
 
+static __be32 nfsd4_get_session_locked(struct nfsd4_session *ses)
+{
+       __be32 status;
+
+       if (is_session_dead(ses))
+               return nfserr_badsession;
+       status = get_client_locked(ses->se_client);
+       if (status)
+               return status;
+       atomic_inc(&ses->se_ref);
+       return nfs_ok;
+}
+
+static void nfsd4_put_session_locked(struct nfsd4_session *ses)
+{
+       struct nfs4_client *clp = ses->se_client;
+
+       if (atomic_dec_and_test(&ses->se_ref) && is_session_dead(ses))
+               free_session(ses);
+       put_client_renew_locked(clp);
+}
+
+static void nfsd4_put_session(struct nfsd4_session *ses)
+{
+       struct nfs4_client *clp = ses->se_client;
+       struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);
+
+       spin_lock(&nn->client_lock);
+       nfsd4_put_session_locked(ses);
+       spin_unlock(&nn->client_lock);
+}
+
+
 static inline u32
 opaque_hashval(const void *ptr, int nbytes)
 {
@@ -1121,7 +1140,7 @@ static void init_session(struct svc_rqst *rqstp, struct nfsd4_session *new, stru
 
 /* caller must hold client_lock */
 static struct nfsd4_session *
-find_in_sessionid_hashtbl(struct nfs4_sessionid *sessionid, struct net *net)
+__find_in_sessionid_hashtbl(struct nfs4_sessionid *sessionid, struct net *net)
 {
        struct nfsd4_session *elem;
        int idx;
@@ -1141,6 +1160,24 @@ find_in_sessionid_hashtbl(struct nfs4_sessionid *sessionid, struct net *net)
        return NULL;
 }
 
+static struct nfsd4_session *
+find_in_sessionid_hashtbl(struct nfs4_sessionid *sessionid, struct net *net,
+               __be32 *ret)
+{
+       struct nfsd4_session *session;
+       __be32 status = nfserr_badsession;
+
+       session = __find_in_sessionid_hashtbl(sessionid, net);
+       if (!session)
+               goto out;
+       status = nfsd4_get_session_locked(session);
+       if (status)
+               session = NULL;
+out:
+       *ret = status;
+       return session;
+}
+
 /* caller must hold client_lock */
 static void
 unhash_session(struct nfsd4_session *ses)
@@ -2157,17 +2194,17 @@ __be32 nfsd4_bind_conn_to_session(struct svc_rqst *rqstp,
        __be32 status;
        struct nfsd4_conn *conn;
        struct nfsd4_session *session;
-       struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
+       struct net *net = SVC_NET(rqstp);
+       struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 
        if (!nfsd4_last_compound_op(rqstp))
                return nfserr_not_only_op;
        nfs4_lock_state();
        spin_lock(&nn->client_lock);
-       session = find_in_sessionid_hashtbl(&bcts->sessionid, SVC_NET(rqstp));
+       session = find_in_sessionid_hashtbl(&bcts->sessionid, net, &status);
        spin_unlock(&nn->client_lock);
-       status = nfserr_badsession;
        if (!session)
-               goto out;
+               goto out_no_session;
        status = nfserr_wrong_cred;
        if (!mach_creds_match(session->se_client, rqstp))
                goto out;
@@ -2181,6 +2218,8 @@ __be32 nfsd4_bind_conn_to_session(struct svc_rqst *rqstp,
        nfsd4_init_conn(rqstp, conn, session);
        status = nfs_ok;
 out:
+       nfsd4_put_session(session);
+out_no_session:
        nfs4_unlock_state();
        return status;
 }
@@ -2200,7 +2239,8 @@ nfsd4_destroy_session(struct svc_rqst *r,
        struct nfsd4_session *ses;
        __be32 status;
        int ref_held_by_me = 0;
-       struct nfsd_net *nn = net_generic(SVC_NET(r), nfsd_net_id);
+       struct net *net = SVC_NET(r);
+       struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 
        nfs4_lock_state();
        status = nfserr_not_only_op;
@@ -2211,14 +2251,12 @@ nfsd4_destroy_session(struct svc_rqst *r,
        }
        dump_sessionid(__func__, &sessionid->sessionid);
        spin_lock(&nn->client_lock);
-       ses = find_in_sessionid_hashtbl(&sessionid->sessionid, SVC_NET(r));
-       status = nfserr_badsession;
+       ses = find_in_sessionid_hashtbl(&sessionid->sessionid, net, &status);
        if (!ses)
                goto out_client_lock;
        status = nfserr_wrong_cred;
        if (!mach_creds_match(ses->se_client, r))
-               goto out_client_lock;
-       nfsd4_get_session_locked(ses);
+               goto out_put_session;
        status = mark_session_dead_locked(ses, 1 + ref_held_by_me);
        if (status)
                goto out_put_session;
@@ -2230,7 +2268,7 @@ nfsd4_destroy_session(struct svc_rqst *r,
        spin_lock(&nn->client_lock);
        status = nfs_ok;
 out_put_session:
-       nfsd4_put_session(ses);
+       nfsd4_put_session_locked(ses);
 out_client_lock:
        spin_unlock(&nn->client_lock);
 out:
@@ -2305,7 +2343,8 @@ nfsd4_sequence(struct svc_rqst *rqstp,
        struct nfsd4_conn *conn;
        __be32 status;
        int buflen;
-       struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
+       struct net *net = SVC_NET(rqstp);
+       struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 
        if (resp->opcnt != 1)
                return nfserr_sequence_pos;
@@ -2319,17 +2358,10 @@ nfsd4_sequence(struct svc_rqst *rqstp,
                return nfserr_jukebox;
 
        spin_lock(&nn->client_lock);
-       status = nfserr_badsession;
-       session = find_in_sessionid_hashtbl(&seq->sessionid, SVC_NET(rqstp));
+       session = find_in_sessionid_hashtbl(&seq->sessionid, net, &status);
        if (!session)
                goto out_no_session;
        clp = session->se_client;
-       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))
@@ -2413,9 +2445,7 @@ out_no_session:
        spin_unlock(&nn->client_lock);
        return status;
 out_put_session:
-       nfsd4_put_session(session);
-out_put_client:
-       put_client_renew_locked(clp);
+       nfsd4_put_session_locked(session);
        goto out_no_session;
 }
 
@@ -2425,18 +2455,12 @@ nfsd4_sequence_done(struct nfsd4_compoundres *resp)
        struct nfsd4_compound_state *cs = &resp->cstate;
 
        if (nfsd4_has_session(cs)) {
-               struct nfs4_client *clp = cs->session->se_client;
-               struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);
-
                if (cs->status != nfserr_replay_cache) {
                        nfsd4_store_cache_entry(resp);
                        cs->slot->sl_flags &= ~NFSD4_SLOT_INUSE;
                }
-               /* Renew the clientid on success and on replay */
-               spin_lock(&nn->client_lock);
+               /* Drop session reference that was taken in nfsd4_sequence() */
                nfsd4_put_session(cs->session);
-               put_client_renew_locked(clp);
-               spin_unlock(&nn->client_lock);
        }
 }
 

diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
index ab937b5..ff160e8 100644 (file)
--- a/fs/nfsd/state.h
+++ b/fs/nfsd/state.h
@@ -212,8 +212,6 @@ struct nfsd4_session {
        struct nfsd4_slot       *se_slots[];    /* forward channel slots */
 };
 
-extern void nfsd4_put_session(struct nfsd4_session *ses);
-
 /* formatted contents of nfs4_sessionid */
 struct nfsd4_sessionid {
        clientid_t      clientid;