Re: [NFS] RE: [autofs] multiple servers per automount

[Mike Waychison]

Ian Kent wrote:

> On Tue, 14 Oct 2003, Joseph V Moss wrote:
>
>  
>
> > The limit is 800 as others have stated.  Although, it can be less than that
> > if something else is already using up some of the reserved UDP ports.
> >
> > I wrote a patch long ago against a 2.2.x kernel to enable it to use
> > multiple majors for NFS mounts (like the patches now common in several
> > distros).  I then ran into the 800 limit in the RPC layer.  After changing
> > the RPC layer to count up from 0, instead of down from 800, with no real
> > upper limit, I was able to mount more than 2000 NFS filesystems simultaneously.
> > I'm sure I could have done many thousand if I had had that many filesystems
> > around to mount.  Obviously, after 1024, it wasn't using reserved ports
> > anymore, but it didn't seem to matter.
> >
> > Unfortunately, while the changes to NFS were easy to port to the 2.4 kernel,
> > the RPC layer is different enough between 2.2 and 2.4 that it didn't work
> > right off.  Bumping it up to somewhere around 1024 should work, but using
> > non-reserved ports didn't seem to work when I made a simple attempt.
> >
> > Of course, the real fix for the NFS layer is the expansion of the minor
> > numbers that's already occurred in 2.6 and the RPC layer problems should
> > be fixed by multiplexing multiple mounts on the same port.
> >
> >
> >    
>
> I don't see that expansion in 2.6 (test6). It looks to me like the 
> allocation is done in set_anon_super (in fs/super.c) and that looks like 
> it is restricted to 256. Please correct this for me. I can't see how there 
> is any change to the number of unnmaed devices.
>
>  

Here is the quick fix for this in RH 2.1AS kernels:

http://www.kernelnewbies.org/kernels/rh21as/SOURCES/linux-2.4.9-moreunnamed.patch

It makes unnamed block devices use majors 12, 14, 38, 39, as well as 0. 

I don't know if anyone is working out a better scheme for 
get_unnamed_dev in 2.6 yet.  It does need to be done though.  A simple 
patch for 2.6 would maybe see the unnamed_dev_in_use bitmap grow to 
PAGE_SIZE, automatically allowing for 32768 unnamed devices.

Mike Waychison

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