Re: [PATCH 1/1] NFSD: register/unregister of nfsd-client shrinker at nfsd startup/shutdown time

[Jeff Layton <jlayton@kernel.org>]

On Mon, 2023-01-09 at 22:43 -0800, Dai Ngo wrote:
> Currently the nfsd-client shrinker is registered and unregistered at
> the time the nfsd module is loaded and unloaded. This means after the
> nfsd service is shutdown, the nfsd-client shrinker is still registered
> in the system. This causes the nfsd-client shrinker to be called when
> memory is low even thought nfsd service is not running. This is also
> true for the nfsd_reply_cache_shrinker.
> 

But this patch doesn't move the reply cache shrinker. Do you intend to
do that too?

> This patch moves the register/unregister of nfsd-client shrinker from
> module load/unload time to nfsd startup/shutdown time.
> 
> Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
> ---
>  fs/nfsd/nfs4state.c | 18 ++++++------------
>  fs/nfsd/nfsctl.c    |  7 +------
>  fs/nfsd/nfsd.h      |  6 ++----
>  3 files changed, 9 insertions(+), 22 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 7b2ee535ade8..ee56c9466304 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -4421,7 +4421,7 @@ nfsd4_state_shrinker_scan(struct shrinker *shrink, struct shrink_control *sc)
>  	return SHRINK_STOP;
>  }
>  
> -int
> +void
>  nfsd4_init_leases_net(struct nfsd_net *nn)
>  {
>  	struct sysinfo si;
> @@ -4443,16 +4443,6 @@ nfsd4_init_leases_net(struct nfsd_net *nn)
>  	nn->nfs4_max_clients = max_t(int, max_clients, NFS4_CLIENTS_PER_GB);
>  
>  	atomic_set(&nn->nfsd_courtesy_clients, 0);
> -	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;
> -	return register_shrinker(&nn->nfsd_client_shrinker, "nfsd-client");
> -}
> -
> -void
> -nfsd4_leases_net_shutdown(struct nfsd_net *nn)
> -{
> -	unregister_shrinker(&nn->nfsd_client_shrinker);
>  }
>  
>  static void init_nfs4_replay(struct nfs4_replay *rp)
> @@ -8077,7 +8067,10 @@ static int nfs4_state_create_net(struct net *net)
>  	INIT_DELAYED_WORK(&nn->nfsd_shrinker_work, nfsd4_state_shrinker_worker);
>  	get_net(net);
>  
> -	return 0;
> +	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;
> +	return register_shrinker(&nn->nfsd_client_shrinker, "nfsd-client");
>  
>  err_sessionid:
>  	kfree(nn->unconf_id_hashtbl);
> @@ -8171,6 +8164,7 @@ 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);
>  	cancel_delayed_work_sync(&nn->laundromat_work);
>  	locks_end_grace(&nn->nfsd4_manager);
>  
> diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
> index d1e581a60480..c2577ee7ffb2 100644
> --- a/fs/nfsd/nfsctl.c
> +++ b/fs/nfsd/nfsctl.c
> @@ -1457,9 +1457,7 @@ static __net_init int nfsd_init_net(struct net *net)
>  		goto out_idmap_error;
>  	nn->nfsd_versions = NULL;
>  	nn->nfsd4_minorversions = NULL;
> -	retval = nfsd4_init_leases_net(nn);
> -	if (retval)
> -		goto out_drc_error;
> +	nfsd4_init_leases_net(nn);
>  	retval = nfsd_reply_cache_init(nn);
>  	if (retval)
>  		goto out_cache_error;
> @@ -1469,8 +1467,6 @@ static __net_init int nfsd_init_net(struct net *net)
>  	return 0;
>  
>  out_cache_error:
> -	nfsd4_leases_net_shutdown(nn);
> -out_drc_error:
>  	nfsd_idmap_shutdown(net);
>  out_idmap_error:
>  	nfsd_export_shutdown(net);
> @@ -1486,7 +1482,6 @@ static __net_exit void nfsd_exit_net(struct net *net)
>  	nfsd_idmap_shutdown(net);
>  	nfsd_export_shutdown(net);
>  	nfsd_netns_free_versions(net_generic(net, nfsd_net_id));
> -	nfsd4_leases_net_shutdown(nn);
>  }
>  
>  static struct pernet_operations nfsd_net_ops = {
> diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
> index 93b42ef9ed91..fa0144a74267 100644
> --- a/fs/nfsd/nfsd.h
> +++ b/fs/nfsd/nfsd.h
> @@ -504,8 +504,7 @@ extern void unregister_cld_notifier(void);
>  extern void nfsd4_ssc_init_umount_work(struct nfsd_net *nn);
>  #endif
>  
> -extern int nfsd4_init_leases_net(struct nfsd_net *nn);
> -extern void nfsd4_leases_net_shutdown(struct nfsd_net *nn);
> +extern void nfsd4_init_leases_net(struct nfsd_net *nn);
>  
>  #else /* CONFIG_NFSD_V4 */
>  static inline int nfsd4_is_junction(struct dentry *dentry)
> @@ -513,8 +512,7 @@ static inline int nfsd4_is_junction(struct dentry *dentry)
>  	return 0;
>  }
>  
> -static inline int nfsd4_init_leases_net(struct nfsd_net *nn) { return 0; };
> -static inline void nfsd4_leases_net_shutdown(struct nfsd_net *nn) {};
> +static inline void nfsd4_init_leases_net(struct nfsd_net *nn) { };
>  
>  #define register_cld_notifier() 0
>  #define unregister_cld_notifier() do { } while(0)



Patch looks reasonable. It might be good to also move the reply cache
init in a similar way (as you pointed out in the patch description).

Reviewed-by: Jeff Layton <jlayton@kernel.org>