[RFC PATCH 3/3] NFSD: Use a referring call list for CB_OFFLOAD

[cel@xxxxxxxxxx]

From: Chuck Lever <chuck.lever@xxxxxxxxxx>

Help the client resolve the race between the reply to an
asynchronous COPY reply and the associated CB_OFFLOAD callback by
planting the session, slot, and sequence number of the COPY in the
CB_SEQUENCE contained in the CB_OFFLOAD COMPOUND.

Suggested-by: Trond Myklebust <trondmy@xxxxxxxxxxxxxxx>
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
 fs/nfsd/nfs4proc.c | 9 +++++++++
 fs/nfsd/xdr4.h     | 4 ++++
 2 files changed, 13 insertions(+)

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index d09a96cbec1e..48b3f5948640 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -1713,6 +1713,7 @@ static int nfsd4_cb_offload_done(struct nfsd4_callback *cb,
 			return 0;
 		}
 	}
+	nfsd41_cb_destroy_referring_call_list(cb);
 	return 1;
 }
 
@@ -1845,6 +1846,9 @@ static void nfsd4_send_cb_offload(struct nfsd4_copy *copy)
 
 	nfsd4_init_cb(&cbo->co_cb, copy->cp_clp, &nfsd4_cb_offload_ops,
 		      NFSPROC4_CLNT_CB_OFFLOAD);
+	nfsd41_cb_referring_call(&cbo->co_cb, &cbo->co_referring_sessionid,
+				 cbo->co_referring_slotid,
+				 cbo->co_referring_seqno);
 	trace_nfsd_cb_offload(copy->cp_clp, &cbo->co_res.cb_stateid,
 			      &cbo->co_fh, copy->cp_count, copy->nfserr);
 	nfsd4_run_cb(&cbo->co_cb);
@@ -1961,6 +1965,11 @@ nfsd4_copy(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 		memcpy(&result->cb_stateid, &copy->cp_stateid.cs_stid,
 			sizeof(result->cb_stateid));
 		dup_copy_fields(copy, async_copy);
+		memcpy(async_copy->cp_cb_offload.co_referring_sessionid.data,
+		       cstate->session->se_sessionid.data,
+		       NFS4_MAX_SESSIONID_LEN);
+		async_copy->cp_cb_offload.co_referring_slotid = cstate->slot_idx;
+		async_copy->cp_cb_offload.co_referring_seqno = cstate->slot->sl_seqid;
 		async_copy->copy_task = kthread_create(nfsd4_do_async_copy,
 				async_copy, "%s", "copy thread");
 		if (IS_ERR(async_copy->copy_task))
diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
index 561894ff4b01..e2e6e6d2393d 100644
--- a/fs/nfsd/xdr4.h
+++ b/fs/nfsd/xdr4.h
@@ -677,6 +677,10 @@ struct nfsd4_cb_offload {
 	__be32			co_nfserr;
 	unsigned int		co_retries;
 	struct knfsd_fh		co_fh;
+
+	struct nfs4_sessionid	co_referring_sessionid;
+	u32			co_referring_slotid;
+	u32			co_referring_seqno;
 };
 
 struct nfsd4_copy {
-- 
2.47.0