diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 0c04f81aa63b..9db8a19cceaa 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -1472,6 +1472,11 @@ static u32 nfsd4_get_drc_mem(struct nfsd4_channel_attrs *ca)
 	spin_lock(&nfsd_drc_lock);
 	avail = min((unsigned long)NFSD_MAX_MEM_PER_SESSION,
 		    nfsd_drc_max_mem - nfsd_drc_mem_used);
+	/*
+	 * Never use more than a third of the remaining memory,
+	 * unless it's the only way to give this client a slot:
+	 */
+	avail = clamp_t(int, avail, slotsize, avail/3);
 	num = min_t(int, num, avail / slotsize);
 	nfsd_drc_mem_used += num * slotsize;
 	spin_unlock(&nfsd_drc_lock);