Re: [PATCH] NFSD: fix up error returned by write_threads()

On Mon, 2026-06-08 at 09:14 -0400, Scott Mayhew wrote:
> Previously, writing 0 to /proc/fs/nfsd/threads would return 0 if the NFS
> server wasn't running.  After commit 14282cc3cfa2, -EIO is returned.
> Existing scripts don't expect this behavior.
> 
> Add a check to bypass the call to nfsd_svc() when newthreads is 0 and
> the NFS server is already stopped.
> 
> Fixes: 14282cc3cfa2 ("NFSD: don't start nfsd if sv_permsocks is empty")
> Signed-off-by: Scott Mayhew <[email protected]>
> ---
>  fs/nfsd/nfsctl.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
> index 04e3954d54bd..ed1a06b4edcd 100644
> --- a/fs/nfsd/nfsctl.c
> +++ b/fs/nfsd/nfsctl.c
> @@ -419,6 +419,7 @@ static ssize_t write_threads(struct file *file, char *buf, size_t size)
>  	char *mesg = buf;
>  	int rv;
>  	struct net *net = netns(file);
> +	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
>  
>  	if (size > 0) {
>  		int newthreads;
> @@ -429,7 +430,10 @@ static ssize_t write_threads(struct file *file, char *buf, size_t size)
>  			return -EINVAL;
>  		trace_nfsd_ctl_threads(net, newthreads);
>  		mutex_lock(&nfsd_mutex);
> -		rv = nfsd_svc(1, &newthreads, net, file->f_cred, NULL);
> +		if (newthreads > 0 || nn->nfsd_serv != NULL)
> +			rv = nfsd_svc(1, &newthreads, net, file->f_cred, NULL);
> +		else
> +			rv = 0;
>  		mutex_unlock(&nfsd_mutex);
>  		if (rv < 0)
>  			return rv;

Reviewed-by: Jeff Layton <[email protected]>