nfs41: back channel drc minimal implementation

For now the back channel ca_maxresponsesize_cached is 0 and there is no
backchannel DRC. Return NFS4ERR_REP_TOO_BIG_TO_CACHE when a cb_sequence
cachethis is true.  When it is false, return NFS4ERR_RETRY_UNCACHED_REP as the
next operation error.

Remember the replay error accross compound operation processing.

Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

2 files changed, 32 insertions, 12 deletions

diff --git a/fs/nfs/callback_proc.c b/fs/nfs/callback_proc.c
index 3d7edd65577b..4062f7690a33 100644
--- a/fs/nfs/callback_proc.c
+++ b/fs/nfs/callback_proc.c
@@ -143,9 +143,8 @@ int nfs41_validate_delegation_stateid(struct nfs_delegation *delegation, const n
  * Return success if the sequenceID is one more than what we last saw on
  * this slot, accounting for wraparound.  Increments the slot's sequence.
  *
- * We don't yet implement a duplicate request cache, so at this time
- * we will log replays, and process them as if we had not seen them before,
- * but we don't bump the sequence in the slot.  Not too worried about it,
+ * We don't yet implement a duplicate request cache, instead we set the
+ * back channel ca_maxresponsesize_cached to zero. This is OK for now
  * since we only currently implement idempotent callbacks anyway.
  *
  * We have a single slot backchannel at this time, so we don't bother
@@ -174,9 +173,15 @@ validate_seqid(struct nfs4_slot_table *tbl, struct cb_sequenceargs * args)
 
         /* Replay */
         if (args->csa_sequenceid == slot->seq_nr) {
-                dprintk("%s seqid %d is a replay - no DRC available\n",
+                dprintk("%s seqid %d is a replay\n",
                         __func__, args->csa_sequenceid);
-                return htonl(NFS4_OK);
+                /* Signal process_op to set this error on next op */
+                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);
         }
 
         /* Wraparound */
@@ -319,9 +324,13 @@ out:
                 kfree(args->csa_rclists[i].rcl_refcalls);
         kfree(args->csa_rclists);
 
-        dprintk("%s: exit with status = %d\n", __func__, ntohl(status));
-        res->csr_status = status;
-        return res->csr_status;
+        if (status == htonl(NFS4ERR_RETRY_UNCACHED_REP))
+                res->csr_status = 0;
+        else
+                res->csr_status = status;
+        dprintk("%s: exit with status = %d res->csr_status %d\n", __func__,
+                ntohl(status), ntohl(res->csr_status));
+        return status;
 }
 
 unsigned nfs4_callback_recallany(struct cb_recallanyargs *args, void *dummy)
diff --git a/fs/nfs/callback_xdr.c b/fs/nfs/callback_xdr.c
index a6f2ded72b17..08b430d922c4 100644
--- a/fs/nfs/callback_xdr.c
+++ b/fs/nfs/callback_xdr.c
@@ -605,7 +605,7 @@ preprocess_nfs4_op(unsigned int op_nr, struct callback_op **op)
 static __be32 process_op(uint32_t minorversion, int nop,
                 struct svc_rqst *rqstp,
                 struct xdr_stream *xdr_in, void *argp,
-                struct xdr_stream *xdr_out, void *resp)
+                struct xdr_stream *xdr_out, void *resp, int* drc_status)
 {
         struct callback_op *op = &callback_ops[0];
         unsigned int op_nr;
@@ -628,6 +628,11 @@ static __be32 process_op(uint32_t minorversion, int nop,
         if (status)
                 goto encode_hdr;
 
+        if (*drc_status) {
+                status = *drc_status;
+                goto encode_hdr;
+        }
+
         maxlen = xdr_out->end - xdr_out->p;
         if (maxlen > 0 && maxlen < PAGE_SIZE) {
                 status = op->decode_args(rqstp, xdr_in, argp);
@@ -636,6 +641,12 @@ static __be32 process_op(uint32_t minorversion, int nop,
         } else
                 status = htonl(NFS4ERR_RESOURCE);
 
+        /* Only set by OP_CB_SEQUENCE processing */
+        if (status == htonl(NFS4ERR_RETRY_UNCACHED_REP)) {
+                *drc_status = status;
+                status = 0;
+        }
+
 encode_hdr:
         res = encode_op_hdr(xdr_out, op_nr, status);
         if (unlikely(res))
@@ -655,7 +666,7 @@ static __be32 nfs4_callback_compound(struct svc_rqst *rqstp, void *argp, void *r
         struct cb_compound_hdr_res hdr_res = { NULL };
         struct xdr_stream xdr_in, xdr_out;
         __be32 *p;
-        __be32 status;
+        __be32 status, drc_status = 0;
         unsigned int nops = 0;
 
         dprintk("%s: start\n", __func__);
@@ -675,8 +686,8 @@ static __be32 nfs4_callback_compound(struct svc_rqst *rqstp, void *argp, void *r
                 return rpc_system_err;
 
         while (status == 0 && nops != hdr_arg.nops) {
-                status = process_op(hdr_arg.minorversion, nops,
-                                    rqstp, &xdr_in, argp, &xdr_out, resp);
+                status = process_op(hdr_arg.minorversion, nops, rqstp,
+                                    &xdr_in, argp, &xdr_out, resp, &drc_status);
                 nops++;
         }