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SubjectRe: NFS locking bug -- limited mtime resolution means nfs_lock() does not provide coherency guarantee
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>>>>> " " == Andi Kleen <ak@suse.de> 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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