[PATCH v5 5/8] NFSD: Count delegations per network namespace

[Chuck Lever <cel@kernel.org>]

The state shrinker is allocated per network namespace, but
nfsd4_state_shrinker_count() reports num_delegations, which counts
the delegations held by the whole host. Every namespace therefore
reports every delegation on the server. Reclaim sees the
population multiplied by the number of namespaces running NFSD. A
namespace holding no delegations of its own still reports a
nonzero count and queues its reaper, which then finds nothing to
recall.

Count the delegations in each namespace and report that instead.
num_delegations stays for the admission check in
__alloc_init_deleg() and the ceiling check in nfs4_laundromat().
Both compare against max_delegations, which is sized from host
memory and so remains a host-wide limit.

Signed-off-by: Chuck Lever <cel@kernel.org>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
---
 fs/nfsd/netns.h     | 2 ++
 fs/nfsd/nfs4state.c | 7 ++++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h
index 71eebfea020d..bb62d19430bc 100644
--- a/fs/nfsd/netns.h
+++ b/fs/nfsd/netns.h
@@ -238,6 +238,8 @@ struct nfsd_net {
 	int			nfs4_max_clients;
 
 	atomic_t		nfsd_courtesy_clients;
+	/* per-namespace; num_delegations in nfs4state.c is host-wide */
+	atomic_long_t		nfsd_delegations;
 	struct shrinker		*nfsd_client_shrinker;
 	struct work_struct	nfsd_shrinker_work;
 
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 5c2dd6657fac..2c169bfabfbe 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -1161,6 +1161,7 @@ static struct nfs4_ol_stateid * nfs4_alloc_open_stateid(struct nfs4_client *clp)
  */
 static void nfs4_free_deleg(struct nfs4_stid *stid)
 {
+	struct nfsd_net *nn = net_generic(stid->sc_client->net, nfsd_net_id);
 	struct nfs4_delegation *dp = delegstateid(stid);
 
 	WARN_ON_ONCE(!list_empty(&stid->sc_cp_list));
@@ -1171,6 +1172,7 @@ static void nfs4_free_deleg(struct nfs4_stid *stid)
 	nfsd41_cb_destroy_referring_call_list(&dp->dl_recall);
 	kmem_cache_free(deleg_slab, stid);
 	atomic_long_dec(&num_delegations);
+	atomic_long_dec(&nn->nfsd_delegations);
 }
 
 /*
@@ -1255,6 +1257,7 @@ __alloc_init_deleg(struct nfs4_client *clp, struct nfs4_file *fp,
 		   struct nfs4_clnt_odstate *odstate, u32 dl_type,
 		   void (*sc_free)(struct nfs4_stid *))
 {
+	struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);
 	struct nfs4_delegation *dp;
 	struct nfs4_stid *stid;
 	long n;
@@ -1263,6 +1266,7 @@ __alloc_init_deleg(struct nfs4_client *clp, struct nfs4_file *fp,
 		return NULL;
 
 	n = atomic_long_inc_return(&num_delegations);
+	atomic_long_inc(&nn->nfsd_delegations);
 	if (n < 0 || n > max_delegations)
 		goto out_dec;
 
@@ -1295,6 +1299,7 @@ __alloc_init_deleg(struct nfs4_client *clp, struct nfs4_file *fp,
 	return dp;
 out_dec:
 	atomic_long_dec(&num_delegations);
+	atomic_long_dec(&nn->nfsd_delegations);
 	return NULL;
 }
 
@@ -5564,7 +5569,7 @@ nfsd4_state_shrinker_count(struct shrinker *shrink, struct shrink_control *sc)
 
 	count = atomic_read(&nn->nfsd_courtesy_clients);
 	if (!count)
-		count = atomic_long_read(&num_delegations);
+		count = atomic_long_read(&nn->nfsd_delegations);
 	if (count)
 		queue_work(laundry_wq, &nn->nfsd_shrinker_work);
 	return (unsigned long)count;

-- 
2.54.0