linux-kernel - Re: [PATCH v2 34/47] nfsd: dynamically allocate the nfsd-client shrinker

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Message-ID: <01e8445d033314b6d9cd67bece74ca1c3ce89945.camel@kernel.org>
Date:   Mon, 24 Jul 2023 08:17:39 -0400
From:   Jeff Layton <jlayton@...nel.org>
To:     Qi Zheng <zhengqi.arch@...edance.com>, akpm@...ux-foundation.org,
        david@...morbit.com, tkhai@...ru, vbabka@...e.cz,
        roman.gushchin@...ux.dev, djwong@...nel.org, brauner@...nel.org,
        paulmck@...nel.org, tytso@....edu, steven.price@....com,
        cel@...nel.org, senozhatsky@...omium.org, yujie.liu@...el.com,
        gregkh@...uxfoundation.org, muchun.song@...ux.dev
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org,
        kvm@...r.kernel.org, xen-devel@...ts.xenproject.org,
        linux-erofs@...ts.ozlabs.org,
        linux-f2fs-devel@...ts.sourceforge.net, cluster-devel@...hat.com,
        linux-nfs@...r.kernel.org, linux-mtd@...ts.infradead.org,
        rcu@...r.kernel.org, netdev@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        dm-devel@...hat.com, linux-raid@...r.kernel.org,
        linux-bcache@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-xfs@...r.kernel.org, linux-btrfs@...r.kernel.org,
        Chuck Lever <chuck.lever@...cle.com>
Subject: Re: [PATCH v2 34/47] nfsd: dynamically allocate the nfsd-client
 shrinker

On Mon, 2023-07-24 at 17:43 +0800, Qi Zheng wrote:
> 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.
> 
> Acked-by: Chuck Lever <chuck.lever@...cle.com>
> Signed-off-by: Qi Zheng <zhengqi.arch@...edance.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 3339177f8e2f..c7a4616cd866 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)
> @@ -8125,12 +8124,17 @@ 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:
> @@ -8228,7 +8232,7 @@ 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_unregister(nn->nfsd_client_shrinker);
>  	cancel_work(&nn->nfsd_shrinker_work);
>  	cancel_delayed_work_sync(&nn->laundromat_work);
>  	locks_end_grace(&nn->nfsd4_manager);

Acked-by: Jeff Layton <jlayton@...nel.org>