Re: Maximum Number of ACL on NFSv4

[Trond Myklebust <trondmy@hammerspace.com>]

On Wed, 2019-08-28 at 17:06 -0400, bfields@fieldses.org wrote:
> On Wed, Aug 28, 2019 at 08:25:16PM +0000, Trond Myklebust wrote:
> > Umm... Don't forget that NFSv4 ACL aces are typically much larger
> > than
> > POSIX ACL aces because the user/group names are encoded as strings,
> > not
> > binary uids and gids.
> > 
> > IOW: The size of the RPC message is likely to be a lot larger than
> > the
> > resulting POSIX ACL...
> 
> Actually this limit is post-idmapping, but, yes, before NFSv4->Posix
> mapping (complicated in itself), which is why I talked about having
> to
> estimate.
> 
> More interested to hear what you think about whether we need a limit
> at
> all.  Do we have any ideas how big is too big a number to pass to
> kmalloc?  Or is it OK to just let anything through and let kmalloc
> fail?
> 

A NFSv4.x client is always required to respect the max request size as
negotiated during CREATE_SESSION, so there is an upper limit right
there. On Linux, the client will never try to negotiate a limit greater
than 1MB.


-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com