Re: mountd --manage-gids supports max 100 groups?

[NeilBrown <neilb@suse.de>]

On Wed, 9 Mar 2011 16:20:42 +0100 "Assarsson, Emil"
<Emil.Assarsson@sonyericsson.com> wrote:

> Hi All,
> 
> Running linux kernel 2.6.32 and nfs-utils 1.2.0 (Ubuntu Lucid)
> 
> A regular user in our company usually is member of more than 300 groups. Some user even have up to 600. We want to use the --manage-gids option for mountd. However it seems to me that it is limited to about 100 groups.
> 
> The reason seems to be that there is a hard limit for mountd but also that the /proc/net/rpc/auth.unix.gid/channel won't accept more than 1008 characters as input.
> 
> I tried to adjust the code for mountd so that it tried to add up to 1000 groups but then I ran in to the channel problem.
> 
> Can someone please guide me to the place where I can adjust this limit?
> 

The limit should be 8192, not 1008.

This is set in net/sunrpc/cache.c
If the write is less than one page, it is handled in cache_downcall().
If it is bigger it is passed to cache_slow_downcall() which stops at
8192 (but could trivially be make to handle more).

What is your evidence that '.../channel won't accept more than 1008
characters as input" ???

Thanks,
NeilBrown