netdev - [PATCH 2/8] nfsd: fix CB_SEQUENCE error handling of NFS4ERR_{BADSLOT,BADSESSION,SEQ

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Message-Id: <20250123-nfsd-6-14-v1-2-c1137a4fa2ae@kernel.org>
Date: Thu, 23 Jan 2025 15:25:19 -0500
From: Jeff Layton <jlayton@...nel.org>
To: Chuck Lever <chuck.lever@...cle.com>, Neil Brown <neilb@...e.de>, 
 Olga Kornievskaia <okorniev@...hat.com>, Dai Ngo <Dai.Ngo@...cle.com>, 
 Tom Talpey <tom@...pey.com>, "J. Bruce Fields" <bfields@...ldses.org>, 
 Kinglong Mee <kinglongmee@...il.com>, Trond Myklebust <trondmy@...nel.org>, 
 Anna Schumaker <anna@...nel.org>, "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>
Cc: linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org, 
 netdev@...r.kernel.org, Jeff Layton <jlayton@...nel.org>
Subject: [PATCH 2/8] nfsd: fix CB_SEQUENCE error handling of
 NFS4ERR_{BADSLOT,BADSESSION,SEQ_MISORDERED}

The current error handling has some problems:

BADSLOT and BADSESSION: don't release the slot before retrying the call

SEQ_MISORDERED: does some sketchy resetting of the seqid? I can't find any
recommendation about doing that in the spec, and it seems wrong.

Handle all three errors the same way: release the slot, but then handle
it just like we would as if we hadn't gotten a reply; mark the session
as faulty, and retry the call.

Fixes: 7ba6cad6c88f ("nfsd: New helper nfsd4_cb_sequence_done() for processing more cb errors")
Signed-off-by: Jeff Layton <jlayton@...nel.org>
---
 fs/nfsd/nfs4callback.c | 27 +++++++++++----------------
 1 file changed, 11 insertions(+), 16 deletions(-)

diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
index e12205ef16ca932ffbcc86d67b0817aec2436c89..bfc9de1fcb67b4f05ed2f7a28038cd8290809c17 100644
--- a/fs/nfsd/nfs4callback.c
+++ b/fs/nfsd/nfs4callback.c
@@ -1371,17 +1371,24 @@ static bool nfsd4_cb_sequence_done(struct rpc_task *task, struct nfsd4_callback
 		nfsd4_mark_cb_fault(cb->cb_clp);
 		ret = false;
 		break;
+	case -NFS4ERR_BADSESSION:
+	case -NFS4ERR_BADSLOT:
+	case -NFS4ERR_SEQ_MISORDERED:
+		/*
+		 * These errors indicate that something has gone wrong
+		 * with the server and client's synchronization. Release
+		 * the slot, but handle it as if we hadn't gotten a reply.
+		 */
+		nfsd41_cb_release_slot(cb);
+		fallthrough;
 	case 1:
 		/*
 		 * cb_seq_status remains 1 if an RPC Reply was never
 		 * received. NFSD can't know if the client processed
 		 * the CB_SEQUENCE operation. Ask the client to send a
-		 * DESTROY_SESSION to recover.
+		 * DESTROY_SESSION to recover, but keep the slot.
 		 */
-		fallthrough;
-	case -NFS4ERR_BADSESSION:
 		nfsd4_mark_cb_fault(cb->cb_clp);
-		ret = false;
 		goto need_restart;
 	case -NFS4ERR_DELAY:
 		cb->cb_seq_status = 1;
@@ -1390,14 +1397,6 @@ static bool nfsd4_cb_sequence_done(struct rpc_task *task, struct nfsd4_callback

 		rpc_delay(task, 2 * HZ);
 		return false;
-	case -NFS4ERR_BADSLOT:
-		goto retry_nowait;
-	case -NFS4ERR_SEQ_MISORDERED:
-		if (session->se_cb_seq_nr[cb->cb_held_slot] != 1) {
-			session->se_cb_seq_nr[cb->cb_held_slot] = 1;
-			goto retry_nowait;
-		}
-		break;
 	default:
 		nfsd4_mark_cb_fault(cb->cb_clp);
 	}
@@ -1405,10 +1404,6 @@ static bool nfsd4_cb_sequence_done(struct rpc_task *task, struct nfsd4_callback
 	nfsd41_cb_release_slot(cb);
 out:
 	return ret;
-retry_nowait:
-	if (rpc_restart_call_prepare(task))
-		ret = false;
-	goto out;
 need_restart:
 	if (!test_bit(NFSD4_CLIENT_CB_KILL, &clp->cl_flags)) {
 		trace_nfsd_cb_restart(clp, cb);

-- 
2.48.1