Re: NFS locking bug -- limited mtime resolution means nfs_lock() does not provide coherency guarantee

[Trond Myklebust]

>>>>> " " == Andi Kleen <[EMAIL PROTECTED]> writes:

     > On Wed, Sep 13, 2000 at 11:51:45AM -0400, Theodore Y. Ts'o
     > wrote:
    >>
    >> So this is a really stupid question, but I'll ask it anyway.
    >> If you just need a cookie, is there any way that you might be
    >> able to steal a few bits from i_generation field for that
    >> purpose?  (This assumes that we only worry about solving the
    >> problem for NFS.)

     > No, it does not help. i_generation is only in the NFS file
     > handle, but not in the fattr/file id this is used for cache
     > checks. The NFS file handle has to stay identical anyways, as
     > long as the inode is not deleted/reused.


You might be able to steal a couple of bytes and then rewrite ext2fs
to mask those out from the 'i_generation' field, but it would mean that
you could no longer boot your old 2.2.16 kernel without trouble on
existing clients.

I'm no expert on the consequences of such a change on ext2fs and what
it might do to other OSes, but my gut feeling is that this is perhaps
one solution that we should try to avoid.

Cheers,
  Trond
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