Re: NFS packet size problem: comments?

Olaf Kirch (
Wed, 29 Jul 1998 21:28:35 +0200

On Wed, 29 Jul 1998 12:42:34 BST, "Stephen C. Tweedie" wrote:
> If you specify an wsize greater than 8192, Linux tries to send bigger
> chunks of data. The BIG problem is when you write to an NFS mounted
> partition: all packets bigger than 8192 are interpreted as bad ones by
> the libc at the other end (the svc_getargs() fails).

Hm, I'm not convinced that it's libc that fails. Are you sure you're
using recent unfsd? It used to have a limit of 8K writes (and would
do unexpected things when you went over that limit). That has been
corrected ages ago, though.

Anyway, you write:

> I think the problem is with a single constant: NFS_MAX_FILE_IO_BUFFER_SIZE.
> In nfs_read_super(), the wsize provided is checked against a MAX:
> else if (server->wsize >= NFS_MAX_FILE_IO_BUFFER_SIZE)
> server->wsize = NFS_MAX_FILE_IO_BUFFER_SIZE;
> but NFS_MAX_FILE_IO_BUFFER_SIZE is set to 16384, not 8192.

While that's not exactly according to the gospel of RFC 1094, it's
not uncommon practice to use bigger sizes.

So I would say it's a bug in unfsd and/or libc.


Olaf Kirch         |  --- o --- Nous sommes du soleil we love when we play  |    / | \   sol.dhoop.naytheet.ah

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