Re: [PATCH RFC v24 3/7] NFSD: move create/destroy of laundry_wq to init_nfsd and exit_nfsd

From: "J. Bruce Fields" <bfields@fieldses.org>
To: Dai Ngo <dai.ngo@oracle.com>
Cc: chuck.lever@oracle.com, jlayton@redhat.com,
	viro@zeniv.linux.org.uk, linux-nfs@vger.kernel.org,
	linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH RFC v24 3/7] NFSD: move create/destroy of laundry_wq to init_nfsd and exit_nfsd
Date: Mon, 2 May 2022 11:35:52 -0400	[thread overview]
Message-ID: <20220502153552.GC30550@fieldses.org> (raw)
In-Reply-To: <1651426696-15509-4-git-send-email-dai.ngo@oracle.com>

On Sun, May 01, 2022 at 10:38:12AM -0700, Dai Ngo wrote:
> This patch moves create/destroy of laundry_wq from nfs4_state_start
> and nfs4_state_shutdown_net to init_nfsd and exit_nfsd to prevent
> the laundromat from being freed while a thread is processing a
> conflicting lock.

Reviewed-by: J. Bruce Fields <bfields@fieldses.org>

> 
> Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
> ---
>  fs/nfsd/nfs4state.c | 28 ++++++++++++++++------------
>  fs/nfsd/nfsctl.c    |  4 ++++
>  fs/nfsd/nfsd.h      |  4 ++++
>  3 files changed, 24 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 0e98e9c16e3e..f369142da79f 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -127,6 +127,21 @@ static const struct nfsd4_callback_ops nfsd4_cb_notify_lock_ops;
>  
>  static struct workqueue_struct *laundry_wq;
>  
> +int nfsd4_create_laundry_wq(void)
> +{
> +	int rc = 0;
> +
> +	laundry_wq = alloc_workqueue("%s", WQ_UNBOUND, 0, "nfsd4");
> +	if (laundry_wq == NULL)
> +		rc = -ENOMEM;
> +	return rc;
> +}
> +
> +void nfsd4_destroy_laundry_wq(void)
> +{
> +	destroy_workqueue(laundry_wq);
> +}
> +
>  static bool is_session_dead(struct nfsd4_session *ses)
>  {
>  	return ses->se_flags & NFS4_SESSION_DEAD;
> @@ -7748,22 +7763,12 @@ nfs4_state_start(void)
>  {
>  	int ret;
>  
> -	laundry_wq = alloc_workqueue("%s", WQ_UNBOUND, 0, "nfsd4");
> -	if (laundry_wq == NULL) {
> -		ret = -ENOMEM;
> -		goto out;
> -	}
>  	ret = nfsd4_create_callback_queue();
>  	if (ret)
> -		goto out_free_laundry;
> +		return ret;
>  
>  	set_max_delegations();
>  	return 0;
> -
> -out_free_laundry:
> -	destroy_workqueue(laundry_wq);
> -out:
> -	return ret;
>  }
>  
>  void
> @@ -7800,7 +7805,6 @@ nfs4_state_shutdown_net(struct net *net)
>  void
>  nfs4_state_shutdown(void)
>  {
> -	destroy_workqueue(laundry_wq);
>  	nfsd4_destroy_callback_queue();
>  }
>  
> diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
> index 16920e4512bd..322a208878f2 100644
> --- a/fs/nfsd/nfsctl.c
> +++ b/fs/nfsd/nfsctl.c
> @@ -1544,6 +1544,9 @@ static int __init init_nfsd(void)
>  	retval = register_cld_notifier();
>  	if (retval)
>  		goto out_free_all;
> +	retval = nfsd4_create_laundry_wq();
> +	if (retval)
> +		goto out_free_all;
>  	return 0;
>  out_free_all:
>  	unregister_pernet_subsys(&nfsd_net_ops);
> @@ -1566,6 +1569,7 @@ static int __init init_nfsd(void)
>  
>  static void __exit exit_nfsd(void)
>  {
> +	nfsd4_destroy_laundry_wq();
>  	unregister_cld_notifier();
>  	unregister_pernet_subsys(&nfsd_net_ops);
>  	nfsd_drc_slab_free();
> diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
> index 23996c6ca75e..847b482155ae 100644
> --- a/fs/nfsd/nfsd.h
> +++ b/fs/nfsd/nfsd.h
> @@ -162,6 +162,8 @@ void nfs4_state_shutdown_net(struct net *net);
>  int nfs4_reset_recoverydir(char *recdir);
>  char * nfs4_recoverydir(void);
>  bool nfsd4_spo_must_allow(struct svc_rqst *rqstp);
> +int nfsd4_create_laundry_wq(void);
> +void nfsd4_destroy_laundry_wq(void);
>  #else
>  static inline int nfsd4_init_slabs(void) { return 0; }
>  static inline void nfsd4_free_slabs(void) { }
> @@ -175,6 +177,8 @@ static inline bool nfsd4_spo_must_allow(struct svc_rqst *rqstp)
>  {
>  	return false;
>  }
> +static inline int nfsd4_create_laundry_wq(void) { return 0; };
> +static inline void nfsd4_destroy_laundry_wq(void) {};
>  #endif
>  
>  /*
> -- 
> 2.9.5