Re: Compatibility issue with 2.2.19pre7

[Manfred Spraul <manfred@colorfullife.com>]

Trond Myklebust wrote:
> 
> 
> As for the issue of casting 'fh->data' as a 'struct knfsd' then that
> is a perfectly valid operation.
>
No it isn't.

fh->data is an array of characters, thus without any alignment
restrictions.
'struct knfsd' begins with a pointer, thus it must be 4 or 8 byte
aligned.

The portable 'struct nfs_fh' structure would be

#define NFS_HANDLESIZE	64
struct nfs_fh
{
	unsigned short len;
	void* data[NFS_HANDLESIZE/sizeof(void*)];
};

But now its too late for such a change - it breaks at least i386,
probably all platforms.

Does knfsd actually need all 64 bytes in the nfs_fh?
What about aligning the 'struct knfsd' manually?

-	struct knfsd* ptr = fh->data;
+	struct knfsd* ptr = (fh->data+15)&(~15);

That would be kernel only, no ABI problems.

--
	Manfred
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