Re: [Ext2-devel] Re: [NFS] htree+NFS (NFS client bug?)

[Stephen C. Tweedie]

Hi,

On Thu, Nov 28, 2002 at 04:44:39PM +0000, Stephen C. Tweedie wrote:
 
> And it's ext3's fault.  Reproducer below.  Run the attached readdir
> against an htree directory and you get something like:
> ...
> getdents at f_pos 0X0000007060CF8B returned 4080.
> getdents at f_pos 0X0000007B9213FA returned 1464.
> getdents at f_pos 0X0000007B9213FA returned 0.
> Final f_pos is 0X0000007B9213FA.
> [root@host1 htest]# 
> 
> The problem is that the htree readdir code is not updating f_pos after
> returning the very last chunk of data to the caller.  That doesn't
> hurt most callers because the location is cached in the filp->private
> data, but it really upsets NFS.

In fact, it's not clear what we _can_ return as f_pos after the last
dirent.

We're only using 31-bit hashes right now.  Trond, how will other NFS
clients react if we return an NFS cookie 32-bits wide?  We could
easily use something like 0x80000000 as an f_pos to represent EOF in
the Linux side of things, but will that cookie work if passed over the
wire on NFSv2?

The alternative is to hack in a special case so that (for example) we
consider a major htree hash of 0x7fffffff to map to an f_pos of
0x7ffffffe and just consider that a possible collision, so that
0x7fffffff is a unique EOF for the htree tree walker.

--Stephen