NFSv4.1: Don't set up a backchannel if the server didn't agree to do so

If the server doesn't agree to out backchannel setup request, then
don't set one up.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

3 files changed, 9 insertions, 2 deletions

diff --git a/fs/nfs/callback_proc.c b/fs/nfs/callback_proc.c
index e36a9d78ea49..197806fb87ff 100644
--- a/fs/nfs/callback_proc.c
+++ b/fs/nfs/callback_proc.c
@@ -427,6 +427,8 @@ __be32 nfs4_callback_sequence(struct cb_sequenceargs *args,
         if (clp == NULL)
                 goto out;
 
+        if (!(clp->cl_session->flags & SESSION4_BACK_CHAN))
+                goto out;
         tbl = &clp->cl_session->bc_slot_table;
 
         spin_lock(&tbl->slot_tbl_lock);
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 006bfa3da55b..59853797825c 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -7195,6 +7195,8 @@ static int nfs4_verify_back_channel_attrs(struct nfs41_create_session_args *args
         struct nfs4_channel_attrs *sent = &args->bc_attrs;
         struct nfs4_channel_attrs *rcvd = &res->bc_attrs;
 
+        if (!(res->flags & SESSION4_BACK_CHAN))
+                goto out;
         if (rcvd->max_rqst_sz > sent->max_rqst_sz)
                 return -EINVAL;
         if (rcvd->max_resp_sz < sent->max_resp_sz)
@@ -7206,6 +7208,7 @@ static int nfs4_verify_back_channel_attrs(struct nfs41_create_session_args *args
                 return -EINVAL;
         if (rcvd->max_reqs != sent->max_reqs)
                 return -EINVAL;
+out:
         return 0;
 }
 
@@ -7226,7 +7229,9 @@ static void nfs4_update_session(struct nfs4_session *session,
         nfs4_copy_sessionid(&session->sess_id, &res->sessionid);
         session->flags = res->flags;
         memcpy(&session->fc_attrs, &res->fc_attrs, sizeof(session->fc_attrs));
-        memcpy(&session->bc_attrs, &res->bc_attrs, sizeof(session->bc_attrs));
+        if (res->flags & SESSION4_BACK_CHAN)
+                memcpy(&session->bc_attrs, &res->bc_attrs,
+                                sizeof(session->bc_attrs));
 }
 
 static int _nfs4_proc_create_session(struct nfs_client *clp,
diff --git a/fs/nfs/nfs4session.c b/fs/nfs/nfs4session.c
index e799dc3c3b1d..e23366effcfb 100644
--- a/fs/nfs/nfs4session.c
+++ b/fs/nfs/nfs4session.c
@@ -450,7 +450,7 @@ int nfs4_setup_session_slot_tables(struct nfs4_session *ses)
         tbl = &ses->fc_slot_table;
         tbl->session = ses;
         status = nfs4_realloc_slot_table(tbl, ses->fc_attrs.max_reqs, 1);
-        if (status) /* -ENOMEM */
+        if (status || !(ses->flags & SESSION4_BACK_CHAN)) /* -ENOMEM */
                 return status;
         /* Back channel */
         tbl = &ses->bc_slot_table;