Re: [PATCH 5/5] nfsd: just keep single lockd reference for nfsd

["J. Bruce Fields" <bfields@fieldses.org>]

On Mon, Jul 19, 2010 at 04:50:08PM -0400, Jeff Layton wrote:
> This patch should replace the other patches that I proposed to make
> sure that each sv_permsock entry holds a lockd refrence.
> 
> Right now, nfsd keeps a lockd reference for each socket that it has
> open. This is unnecessary and complicates the error handling on
> startup and shutdown. Change it to just do a lockd_up when creating
> the nfsd_serv and just do a single lockd_down when taking down the
> last nfsd thread.
> 
> This patch also changes the error handling in nfsd_create_serv a
> bit too. There doesn't seem to be any need to reset the nfssvc_boot
> time if the nfsd startup failed.
> 
> Note though that this does change the user-visible behavior slightly.
> Today when someone writes a text socktype and port to the portlist file
> prior to starting nfsd, lockd is not started when nfsd threads are
> brought up. With this change, it will be started any time that
> the nfsd_serv is created.

OK, so it may be started earlier in the process than it was before.

> I'm making the assumption that that's not a
> problem. If it is then we'll need to take a different approach to fixing
> this.

Especially in the case of a later failure, it does worry me a little
that we could leave lockd running without having started nfsd.

Is there a clean way to defer starting lock till we start the first
server threads?  Maybe fs/nfsd/nfssvc.c:nfsd() could (at the start,
while under nfsd_mutex), check if lockd is up and start it if not??  But
I think that can leave us calling lockd_down and not lockd_up in some
cases.  Maybe start lockd in svc_set_num_threads()?

--b.

> 
> Signed-off-by: Jeff Layton <jlayton@redhat.com>
> ---
>  fs/nfsd/nfsctl.c |   10 ----------
>  fs/nfsd/nfssvc.c |   25 ++++++++++---------------
>  2 files changed, 10 insertions(+), 25 deletions(-)
> 
> diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
> index 9e8645a..b1c5be8 100644
> --- a/fs/nfsd/nfsctl.c
> +++ b/fs/nfsd/nfsctl.c
> @@ -949,15 +949,8 @@ static ssize_t __write_ports_addfd(char *buf)
>  	if (err != 0)
>  		return err;
>  
> -	err = lockd_up();
> -	if (err != 0) {
> -		svc_destroy(nfsd_serv);
> -		return err;
> -	}
> -
>  	err = svc_addsock(nfsd_serv, fd, buf, SIMPLE_TRANSACTION_LIMIT);
>  	if (err < 0) {
> -		lockd_down();
>  		svc_destroy(nfsd_serv);
>  		return err;
>  	}
> @@ -982,9 +975,6 @@ static ssize_t __write_ports_delfd(char *buf)
>  	if (nfsd_serv != NULL)
>  		len = svc_sock_names(nfsd_serv, buf,
>  					SIMPLE_TRANSACTION_LIMIT, toclose);
> -	if (len >= 0)
> -		lockd_down();
> -
>  	kfree(toclose);
>  	return len;
>  }
> diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
> index a06ea99..6b59d32 100644
> --- a/fs/nfsd/nfssvc.c
> +++ b/fs/nfsd/nfssvc.c
> @@ -183,9 +183,7 @@ int nfsd_nrthreads(void)
>  static void nfsd_last_thread(struct svc_serv *serv)
>  {
>  	/* When last nfsd thread exits we need to do some clean-up */
> -	struct svc_xprt *xprt;
> -	list_for_each_entry(xprt, &serv->sv_permsocks, xpt_list)
> -		lockd_down();
> +	lockd_down();
>  	nfsd_serv = NULL;
>  	nfsd_racache_shutdown();
>  	nfs4_state_shutdown();
> @@ -264,13 +262,18 @@ int nfsd_create_serv(void)
>  			nfsd_max_blksize /= 2;
>  	}
>  
> +	err = lockd_up();
> +	if (err != 0)
> +		return err;
> +
>  	nfsd_serv = svc_create_pooled(&nfsd_program, nfsd_max_blksize,
>  				      nfsd_last_thread, nfsd, THIS_MODULE);
> -	if (nfsd_serv == NULL)
> -		err = -ENOMEM;
> -	else
> -		set_max_drc();
> +	if (nfsd_serv == NULL) {
> +		lockd_down();
> +		return -ENOMEM;
> +	}
>  
> +	set_max_drc();
>  	do_gettimeofday(&nfssvc_boot);		/* record boot time */
>  	return err;
>  }
> @@ -286,19 +289,11 @@ static int nfsd_init_socks(int port)
>  	if (error < 0)
>  		return error;
>  
> -	error = lockd_up();
> -	if (error < 0)
> -		return error;
> -
>  	error = svc_create_xprt(nfsd_serv, "tcp", PF_INET, port,
>  					SVC_SOCK_DEFAULTS);
>  	if (error < 0)
>  		return error;
>  
> -	error = lockd_up();
> -	if (error < 0)
> -		return error;
> -
>  	return 0;
>  }
>  
> -- 
> 1.5.5.6
>