NFSv4.x: Enforce the ca_maxresponsesize_cached on the back channel

We have no duplicate reply cache, so we always set the back channel
ca_maxresponsesize_cached to zero when negotiating the session.
That means we should always error out as soon as we see the server
set args->csa_cachethis.

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

1 files changed, 6 insertions, 3 deletions

diff --git a/fs/nfs/callback_proc.c b/fs/nfs/callback_proc.c
index e0844fdbd9ac..345df6309017 100644
--- a/fs/nfs/callback_proc.c
+++ b/fs/nfs/callback_proc.c
@@ -381,9 +381,8 @@ validate_seqid(struct nfs4_slot_table *tbl, struct cb_sequenceargs * args)
                 if (args->csa_cachethis == 0)
                         return htonl(NFS4ERR_RETRY_UNCACHED_REP);
 
-                /* The ca_maxresponsesize_cached is 0 with no DRC */
-                else if (args->csa_cachethis == 1)
-                        return htonl(NFS4ERR_REP_TOO_BIG_TO_CACHE);
+                /* Liar! We never allowed you to set csa_cachethis != 0 */
+                return htonl(NFS4ERR_SEQ_FALSE_RETRY);
         }
 
         /* Wraparound */
@@ -500,6 +499,10 @@ __be32 nfs4_callback_sequence(struct cb_sequenceargs *args,
 
         cps->slotid = args->csa_slotid;
 
+        /* The ca_maxresponsesize_cached is 0 with no DRC */
+        if (args->csa_cachethis != 0)
+                return htonl(NFS4ERR_REP_TOO_BIG_TO_CACHE);
+
         /*
          * Check for pending referring calls.  If a match is found, a
          * related callback was received before the response to the original