Re: [PATCH v2 1/1] NFSD: register/unregister of nfsd-client shrinker at nfsd startup/shutdown time

[Chuck Lever III <chuck.lever@oracle.com>]

> On Jan 11, 2023, at 3:17 PM, Dai Ngo <dai.ngo@oracle.com> wrote:
> 
> Currently the nfsd-client shrinker is registered and unregistered at
> the time the nfsd module is loaded and unloaded. The problem with this
> is the shrinker is being registered before all of the relevant fields
> in nfsd_net are initialized when nfsd is started. This can lead to an
> oops when memory is low and the shrinker is called while nfsd is not
> running.
> 
> This patch moves the  register/unregister of nfsd-client shrinker from
> module load/unload time to nfsd startup/shutdown time.
> 
> Fixes: 44df6f439a17 ("NFSD: add delegation reaper to react to low memory condition")
> Reported-by: Mike Galbraith <efault@gmx.de>
> Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
> ---
> v2: reword change log for better description of the problem

Hello Dai, I've applied this to nfsd's for-rc, and expect to send
it along to Linus in a few days. Thanks for seeing it through!


> fs/nfsd/nfs4state.c | 22 +++++++++++-----------
> fs/nfsd/nfsctl.c    |  7 +------
> fs/nfsd/nfsd.h      |  6 ++----
> 3 files changed, 14 insertions(+), 21 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 7b2ee535ade8..a7cfefd7c205 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)
> @@ -8077,8 +8067,17 @@ static int nfs4_state_create_net(struct net *net)
> 	INIT_DELAYED_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"))
> +		goto err_shrinker;
> 	return 0;
> 
> +err_shrinker:
> +	put_net(net);
> +	kfree(nn->sessionid_hashtbl);
> err_sessionid:
> 	kfree(nn->unconf_id_hashtbl);
> err_unconf_id:
> @@ -8171,6 +8170,7 @@ 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)
> -- 
> 2.9.5
> 

--
Chuck Lever