[PATCH v4 35/48] nfsd: dynamically allocate the nfsd-client shrinker

[Qi Zheng via Linux-erofs]

In preparation for implementing lockless slab shrink, use new APIs 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.a...@bytedance.com>
Acked-by: Chuck Lever <chuck.le...@oracle.com>
Acked-by: Jeff Layton <jlay...@kernel.org>
---
 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 8534693eb6a4..9e401db8a6d2 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -4400,8 +4400,7 @@ 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)
@@ -8149,12 +8148,17 @@ 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(0, "nfsd-client");
+       if (!nn->nfsd_client_shrinker)
                goto err_shrinker;
+
+       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;
+       nn->nfsd_client_shrinker->private_data = nn;
+
+       shrinker_register(nn->nfsd_client_shrinker);
+
        return 0;
 
 err_shrinker:
@@ -8252,7 +8256,7 @@ 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);
+       shrinker_free(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