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

Chuck Lever
2023-06-23T21:51:02Z

On Thu, Jun 22, 2023 at 04:53:21PM +0800, Qi Zheng wrote:
> 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>

For 15/29 and 16/29 of this series:

Acked-by: Chuck Lever <chuck.lever@oracle.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
>