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

[Chuck Lever <cel@kernel.org>]

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
>