[PATCH 15/29] NFSD: dynamically allocate the nfsd-client shrinker

[Qi Zheng <zhengqi.arch@bytedance.com>]

In preparation for implementing lockless slab shrink,
we need to dynamically allocate the nfsd-client shrinker,
so that it can be freed asynchronously using kfree_rcu().
Then it doesn't need to wait for RCU read-side critical
section when releasing the struct nfsd_net.

Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
---
 fs/nfsd/netns.h     |  2 +-
 fs/nfsd/nfs4state.c | 20 ++++++++++++--------
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h
index ec49b200b797..f669444d5336 100644
--- a/fs/nfsd/netns.h
+++ b/fs/nfsd/netns.h
@@ -195,7 +195,7 @@ struct nfsd_net {
 	int			nfs4_max_clients;
 
 	atomic_t		nfsd_courtesy_clients;
-	struct shrinker		nfsd_client_shrinker;
+	struct shrinker		*nfsd_client_shrinker;
 	struct work_struct	nfsd_shrinker_work;
 };
 
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 6e61fa3acaf1..a06184270548 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -4388,8 +4388,7 @@ static unsigned long
 nfsd4_state_shrinker_count(struct shrinker *shrink, struct shrink_control *sc)
 {
 	int count;
-	struct nfsd_net *nn = container_of(shrink,
-			struct nfsd_net, nfsd_client_shrinker);
+	struct nfsd_net *nn = shrink->private_data;
 
 	count = atomic_read(&nn->nfsd_courtesy_clients);
 	if (!count)
@@ -8094,14 +8093,19 @@ static int nfs4_state_create_net(struct net *net)
 	INIT_WORK(&nn->nfsd_shrinker_work, nfsd4_state_shrinker_worker);
 	get_net(net);
 
-	nn->nfsd_client_shrinker.scan_objects = nfsd4_state_shrinker_scan;
-	nn->nfsd_client_shrinker.count_objects = nfsd4_state_shrinker_count;
-	nn->nfsd_client_shrinker.seeks = DEFAULT_SEEKS;
-
-	if (register_shrinker(&nn->nfsd_client_shrinker, "nfsd-client"))
+	nn->nfsd_client_shrinker = shrinker_alloc_and_init(nfsd4_state_shrinker_count,
+							   nfsd4_state_shrinker_scan,
+							   0, DEFAULT_SEEKS, 0,
+							   nn);
+	if (!nn->nfsd_client_shrinker)
 		goto err_shrinker;
+
+	if (register_shrinker(nn->nfsd_client_shrinker, "nfsd-client"))
+		goto err_register;
 	return 0;
 
+err_register:
+	shrinker_free(nn->nfsd_client_shrinker);
 err_shrinker:
 	put_net(net);
 	kfree(nn->sessionid_hashtbl);
@@ -8197,7 +8201,7 @@ nfs4_state_shutdown_net(struct net *net)
 	struct list_head *pos, *next, reaplist;
 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 
-	unregister_shrinker(&nn->nfsd_client_shrinker);
+	unregister_and_free_shrinker(nn->nfsd_client_shrinker);
 	cancel_work(&nn->nfsd_shrinker_work);
 	cancel_delayed_work_sync(&nn->laundromat_work);
 	locks_end_grace(&nn->nfsd4_manager);
-- 
2.30.2