Using HyperV with Samba 4.2

Richard Sharpe realrichardsharpe at
Fri Oct 17 09:44:25 MDT 2014

On Fri, Oct 17, 2014 at 7:05 AM, Richard Sharpe
<realrichardsharpe at> wrote:
> On Fri, Oct 17, 2014 at 6:49 AM, David Disseldorp <ddiss at> wrote:
>> On Wed, 15 Oct 2014 05:05:24 -0700, Richard Sharpe wrote:
>>> Hi folks,
>>> Sending this out in the hope that it will be useful to some people.
>> Thanks!
>>> Secondly, you will need to create a VFS module (or modify your
>>> existing VFS module if you have one) to assert that your file system
>>> supports compression and to implement the set_compression and
>>> get_compression entry points.
>> I'm a little surprised by the client behaviour here. With
>> FILE_FILE_COMPRESSION missing from the FS capabilities, the server
>> doesn't support compression, so explicitly disabling it on a per-file
>> basis shouldn't be necessary.
> Hmmm, maybe I need to look more closely at the capture. It was asking
> to disable compression so maybe the people who supplied me with the
> capture were mistakenly claiming they supported compression.

Actually, I don't need to.

Here is the key test in fsctl_set_cmprn:

        if ((fsp->conn->fs_capabilities & FILE_FILE_COMPRESSION) == 0) {
                DEBUG(4, ("FS does not advertise compression support\n"));
                return NT_STATUS_NOT_SUPPORTED;

And STATUS_NOT_SUPPORTED is what I saw on the wire.

The client was issuing that FSCTL despite the fact that the server
told it compression was not supported.

Richard Sharpe

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