Re: [PATCH] nfsd: drop the nfsd_put helper

From: Chuck Lever <chuck.lever@oracle.com>
To: Jeff Layton <jlayton@kernel.org>
Cc: Neil Brown <neilb@suse.de>, Olga Kornievskaia <kolga@netapp.com>,
	Dai Ngo <Dai.Ngo@oracle.com>, Tom Talpey <tom@talpey.com>,
	linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org,
	Zhi Li <yieli@redhat.com>
Subject: Re: [PATCH] nfsd: drop the nfsd_put helper
Date: Wed, 3 Jan 2024 09:48:55 -0500	[thread overview]
Message-ID: <ZZVz1wd/oTvBk3dU@tissot.1015granger.net> (raw)
In-Reply-To: <20240103-nfsd-fixes-v1-1-4f4f9d7edd0d@kernel.org>

On Wed, Jan 03, 2024 at 08:36:52AM -0500, Jeff Layton wrote:
> It's not safe to call nfsd_put once nfsd_last_thread has been called, as
> that function will zero out the nn->nfsd_serv pointer.
> 
> Drop the nfsd_put helper altogether and open-code the svc_put in its
> callers instead. That allows us to not be reliant on the value of that
> pointer when handling an error.
> 
> Fixes: 2a501f55cd64 ("nfsd: call nfsd_last_thread() before final nfsd_put()")
> Reported-by: Zhi Li <yieli@redhat.com>
> Cc: NeilBrown <neilb@suse.de>
> Signed-off-by: Jeffrey Layton <jlayton@redhat.com>
> ---
> I know it's late, but it would be good to get this into v6.7 if
> possible. I think it's fairly straightforward.

How is Zhi finding these? Are there administrative API tests that
can be shared with the community (say, by adding them to kdevops)?

> ---
>  fs/nfsd/nfsctl.c | 31 +++++++++++++++++--------------
>  fs/nfsd/nfsd.h   |  7 -------
>  2 files changed, 17 insertions(+), 21 deletions(-)
> 
> diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
> index 7cd513e59305..87fed75808ff 100644
> --- a/fs/nfsd/nfsctl.c
> +++ b/fs/nfsd/nfsctl.c
> @@ -693,6 +693,7 @@ static ssize_t __write_ports_addfd(char *buf, struct net *net, const struct cred
>  	char *mesg = buf;
>  	int fd, err;
>  	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
> +	struct svc_serv *serv;
>  
>  	err = get_int(&mesg, &fd);
>  	if (err != 0 || fd < 0)
> @@ -703,15 +704,15 @@ static ssize_t __write_ports_addfd(char *buf, struct net *net, const struct cred
>  	if (err != 0)
>  		return err;
>  
> -	err = svc_addsock(nn->nfsd_serv, net, fd, buf, SIMPLE_TRANSACTION_LIMIT, cred);
> +	serv = nn->nfsd_serv;
> +	err = svc_addsock(serv, net, fd, buf, SIMPLE_TRANSACTION_LIMIT, cred);
>  
> -	if (err < 0 && !nn->nfsd_serv->sv_nrthreads && !nn->keep_active)
> +	if (err < 0 && !serv->sv_nrthreads && !nn->keep_active)
>  		nfsd_last_thread(net);
> -	else if (err >= 0 &&
> -		 !nn->nfsd_serv->sv_nrthreads && !xchg(&nn->keep_active, 1))
> -		svc_get(nn->nfsd_serv);
> +	else if (err >= 0 && !serv->sv_nrthreads && !xchg(&nn->keep_active, 1))
> +		svc_get(serv);
>  
> -	nfsd_put(net);
> +	svc_put(serv);
>  	return err;
>  }
>  
> @@ -725,6 +726,7 @@ static ssize_t __write_ports_addxprt(char *buf, struct net *net, const struct cr
>  	struct svc_xprt *xprt;
>  	int port, err;
>  	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
> +	struct svc_serv *serv;
>  
>  	if (sscanf(buf, "%15s %5u", transport, &port) != 2)
>  		return -EINVAL;
> @@ -737,32 +739,33 @@ static ssize_t __write_ports_addxprt(char *buf, struct net *net, const struct cr
>  	if (err != 0)
>  		return err;
>  
> -	err = svc_xprt_create(nn->nfsd_serv, transport, net,
> +	serv = nn->nfsd_serv;
> +	err = svc_xprt_create(serv, transport, net,
>  			      PF_INET, port, SVC_SOCK_ANONYMOUS, cred);
>  	if (err < 0)
>  		goto out_err;
>  
> -	err = svc_xprt_create(nn->nfsd_serv, transport, net,
> +	err = svc_xprt_create(serv, transport, net,
>  			      PF_INET6, port, SVC_SOCK_ANONYMOUS, cred);
>  	if (err < 0 && err != -EAFNOSUPPORT)
>  		goto out_close;
>  
> -	if (!nn->nfsd_serv->sv_nrthreads && !xchg(&nn->keep_active, 1))
> -		svc_get(nn->nfsd_serv);
> +	if (!serv->sv_nrthreads && !xchg(&nn->keep_active, 1))
> +		svc_get(serv);
>  
> -	nfsd_put(net);
> +	svc_put(serv);
>  	return 0;
>  out_close:
> -	xprt = svc_find_xprt(nn->nfsd_serv, transport, net, PF_INET, port);
> +	xprt = svc_find_xprt(serv, transport, net, PF_INET, port);
>  	if (xprt != NULL) {
>  		svc_xprt_close(xprt);
>  		svc_xprt_put(xprt);
>  	}
>  out_err:
> -	if (!nn->nfsd_serv->sv_nrthreads && !nn->keep_active)
> +	if (!serv->sv_nrthreads && !nn->keep_active)
>  		nfsd_last_thread(net);
>  
> -	nfsd_put(net);
> +	svc_put(serv);
>  	return err;
>  }
>  
> diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
> index 3286ffacbc56..9ed0e08d16c2 100644
> --- a/fs/nfsd/nfsd.h
> +++ b/fs/nfsd/nfsd.h
> @@ -113,13 +113,6 @@ int		nfsd_pool_stats_open(struct inode *, struct file *);
>  int		nfsd_pool_stats_release(struct inode *, struct file *);
>  void		nfsd_shutdown_threads(struct net *net);
>  
> -static inline void nfsd_put(struct net *net)
> -{
> -	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
> -
> -	svc_put(nn->nfsd_serv);
> -}
> -
>  bool		i_am_nfsd(void);
>  
>  struct nfsdfs_client {
> 
> ---
> base-commit: 610a9b8f49fbcf1100716370d3b5f6f884a2835a
> change-id: 20240103-nfsd-fixes-1f1196134a11
> 
> Best regards,
> -- 
> Jeff Layton <jlayton@kernel.org>
> 

-- 
Chuck Lever