Re: [PATCH] cifs: mark CONFIG_CIFS_NFSD_EXPORT as BROKEN

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On Sun, May 22, 2011 at 7:17 AM, Jeff Layton <jlayton@xxxxxxxxxx> wrote:
> On Sun, 22 May 2011 07:59:38 -0400
> Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:
>
>> On Sun, May 22, 2011 at 07:55:24AM -0400, Jeff Layton wrote:
>> > This will never work properly with CIFS, as the protocol has no ability
>> > whatsoever for looking up files by filehandle. It *might* be possible to
>> > eventually do this with SMB2, but that remains to be seen.
>> >
>> > For now, it just plain doesn't work. Mark it BROKEN to discourage
>> > distros from enabling it.
>>
>> It's actually dead code at this point - fs/nfsd/vfs.c:check_export()
>> refuses to export a filesystem that does not have a fh_to_dentry
>> operation, which cifs doesn't provide.
>>
>> IMHO it's best to just remove the option and all surrounding code.
>>
>
> I agree and proposed a patch to do that a month or two ago. Steve
> NAK'ed it for reasons that I don't quite understand.

We were waiting on clarification on NTCreateX open by inode number flag.

We have had multiple requests to be able to do limited
export of cifs data via nfs (for example for backup to/from
OS with only one of the protocols supported).   NFS clients
don't make this easy - because some don't handle ESTALE
by revalidating their dentries.

For nfs v3 clients that can't handle ESTALE, we are probably
stuck with having to wait for Samba to implement the flag.

I did want to see JRA's opinion and also query if other
NFS clients (other than Linux) can handle ESTALE
(by e.g. revalidating the dentry and repeating the operation).






-- 
Thanks,

Steve
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