[RFC PATCH 3/9] NFSD: Handle an NFS4ERR_DELAY response to CB_OFFLOAD

[cel@xxxxxxxxxx]

From: Chuck Lever <chuck.lever@xxxxxxxxxx>

RFC 7862 permits callback services to respond to CB_OFFLOAD with
NFS4ERR_DELAY. Currently NFSD drops the CB_OFFLOAD in that case.

To improve the reliability of COPY offload, NFSD should rather send
another CB_OFFLOAD completion notification.

Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
 fs/nfsd/nfs4proc.c | 8 ++++++++
 fs/nfsd/xdr4.h     | 1 +
 2 files changed, 9 insertions(+)

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index a3c564a9596c..02e73ebbfe5c 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -1613,6 +1613,13 @@ static int nfsd4_cb_offload_done(struct nfsd4_callback *cb,
 		container_of(cb, struct nfsd4_cb_offload, co_cb);
 
 	trace_nfsd_cb_offload_done(&cbo->co_res.cb_stateid, task);
+	switch (task->tk_status) {
+	case -NFS4ERR_DELAY:
+		if (cbo->co_retries--) {
+			rpc_delay(task, 1 * HZ);
+			return 0;
+		}
+	}
 	return 1;
 }
 
@@ -1742,6 +1749,7 @@ static void nfsd4_send_cb_offload(struct nfsd4_copy *copy)
 	memcpy(&cbo->co_res, &copy->cp_res, sizeof(copy->cp_res));
 	memcpy(&cbo->co_fh, &copy->fh, sizeof(copy->fh));
 	cbo->co_nfserr = copy->nfserr;
+	cbo->co_retries = 5;
 
 	nfsd4_init_cb(&cbo->co_cb, copy->cp_clp, &nfsd4_cb_offload_ops,
 		      NFSPROC4_CLNT_CB_OFFLOAD);
diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
index dec29afa43f3..cd2bf63651e3 100644
--- a/fs/nfsd/xdr4.h
+++ b/fs/nfsd/xdr4.h
@@ -675,6 +675,7 @@ struct nfsd4_cb_offload {
 	struct nfsd4_callback	co_cb;
 	struct nfsd42_write_res	co_res;
 	__be32			co_nfserr;
+	unsigned int		co_retries;
 	struct knfsd_fh		co_fh;
 };
 
-- 
2.46.2