[PATCH] nfsd: remove long-standing revoked delegations by force

[Li Lingfeng <lilingfeng3@huawei.com>]

When file access conflicts occur between clients, the server recalls
delegations. If the client holding delegation fails to return it after
a recall, nfs4_laundromat adds the delegation to cl_revoked list.
This causes subsequent SEQUENCE operations to set the
SEQ4_STATUS_RECALLABLE_STATE_REVOKED flag, forcing the client to
validate all delegations and return the revoked one.

However, if the client fails to return the delegation due to a timeout
after receiving the recall or a server bug, the delegation remains in the
server's cl_revoked list. The client marks it revoked and won't find it
upon detecting SEQ4_STATUS_RECALLABLE_STATE_REVOKED. This leads to a loop:
the server persistently sets SEQ4_STATUS_RECALLABLE_STATE_REVOKED, and the
client repeatedly tests all delegations, severely impacting performance
when numerous delegations exist.

Since abnormal delegations are removed from flc_lease via nfs4_laundromat
--> revoke_delegation --> destroy_unhashed_deleg -->
nfs4_unlock_deleg_lease --> kernel_setlease, and do not block new open
requests indefinitely, retaining such a delegation on the server is
unnecessary.

Reported-by: Zhang Jian <zhangjian496@huawei.com>
Fixes: 3bd64a5ba171 ("nfsd4: implement SEQ4_STATUS_RECALLABLE_STATE_REVOKED")
Closes: https://lore.kernel.org/all/ff8debe9-6877-4cf7-ba29-fc98eae0ffa0@huawei.com/
Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com>
---
 fs/nfsd/nfs4state.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 88c347957da5..aa65a685dbb9 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -4326,6 +4326,8 @@ nfsd4_sequence(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	int buflen;
 	struct net *net = SVC_NET(rqstp);
 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+	struct list_head *pos, *next;
+	struct nfs4_delegation *dp;
 
 	if (resp->opcnt != 1)
 		return nfserr_sequence_pos;
@@ -4470,6 +4472,15 @@ nfsd4_sequence(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	default:
 		seq->status_flags = 0;
 	}
+	if (!list_empty(&clp->cl_revoked)) {
+		list_for_each_safe(pos, next, &clp->cl_revoked) {
+			dp = list_entry(pos, struct nfs4_delegation, dl_recall_lru);
+			if (dp->dl_time < (ktime_get_boottime_seconds() - 2 * nn->nfsd4_lease)) {
+				list_del_init(&dp->dl_recall_lru);
+				nfs4_put_stid(&dp->dl_stid);
+			}
+		}
+	}
 	if (!list_empty(&clp->cl_revoked))
 		seq->status_flags |= SEQ4_STATUS_RECALLABLE_STATE_REVOKED;
 	if (atomic_read(&clp->cl_admin_revoked))
-- 
2.46.1