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Date:   Mon, 19 Oct 2020 09:20:00 -0400
From:   "J. Bruce Fields" <bfields@fieldses.org>
To:     Roberto Bergantinos Corpas <rbergant@redhat.com>
Cc:     linux-nfs@vger.kernel.org
Subject: Re: [PATCH] sunrpc: raise kernel RPC channel buffer size
Message-ID: <20201019132000.GA32403@fieldses.org>
References: <20201019093356.7395-1-rbergant@redhat.com>
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On Mon, Oct 19, 2020 at 11:33:56AM +0200, Roberto Bergantinos Corpas wrote:
> Its possible that using AUTH_SYS and mountd manage-gids option a
> user may hit the 8k RPC channel buffer limit. This have been observed
> on field, causing unanswered RPCs on clients after mountd fails to
> write on channel :
> 
> rpc.mountd[11231]: auth_unix_gid: error writing reply
> 
> Userland nfs-utils uses a buffer size of 32k (RPC_CHAN_BUF_SIZE), so
> lets match those two.

Thanks, applying.

That should allow about 4000 group memberships.  If that doesn't do it
then maybe it's time to rethink....

--b.

> 
> Signed-off-by: Roberto Bergantinos Corpas <rbergant@redhat.com>
> ---
>  net/sunrpc/cache.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
> index baef5ee43dbb..08df4c599ab3 100644
> --- a/net/sunrpc/cache.c
> +++ b/net/sunrpc/cache.c
> @@ -908,7 +908,7 @@ static ssize_t cache_do_downcall(char *kaddr, const char __user *buf,
>  static ssize_t cache_slow_downcall(const char __user *buf,
>  				   size_t count, struct cache_detail *cd)
>  {
> -	static char write_buf[8192]; /* protected by queue_io_mutex */
> +	static char write_buf[32768]; /* protected by queue_io_mutex */
>  	ssize_t ret = -EINVAL;
>  
>  	if (count >= sizeof(write_buf))
> -- 
> 2.21.0