[RFC PATCH] smbd: resilient file handle support

[Bryan Burgin]

Hi Uri,

Then there is some other cause to this.  I'll be happy to work on this with you or any Samba colleague that is willing to work on this.  When you are ready, please send mail to me ("bburgin (at) microsoft (dot) com") AND to Dochelp ("dochelp (at) microsoft (dot) com").  I would want exact repro instructions, including the Samba setup necessary,and network traces.

Bryan

-----Original Message-----
From: Uri Simchoni [mailto:uri at samba.org] 
Sent: Saturday, February 20, 2016 6:30 AM
To: Bryan Burgin <bburgin at microsoft.com>; samba-technical at lists.samba.org
Subject: Re: [RFC PATCH] smbd: resilient file handle support

Bryan,

Sorry for not updating - I haven't had time to figure it out yet, but there's one thing I can already confirm, namely that the Win10 failure against our box has nothing to do with resilient file handles - the failure occurs before creating the .vhdx. I'll update with findings when I have them.

Thanks,
Uri.

On 02/19/2016 08:53 PM, Bryan Burgin wrote:
> Uri,
>
> An update, following up on your comment "I [Uri] will check. I [Uri] have reports that we fail Windows 10 backup too unless downgrading to SMB2.0.2, but I haven't studied it closely as with Win8":
>
> Regarding the Bugzilla report at https://na01.safelinks.protection.outlook.com/?url=https%3a%2f%2fbugzilla.samba.org%2fshow_bug.cgi%3fid%3d10159&data=01%7c01%7cbburgin%40microsoft.com%7cfacf215583da49b1555808d33a02437e%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=JnfGXRbqXN3BZtsbVAq0C%2buRMruZbHvbXgqCnMnuu4A%3d and the fix we created for Windows 8 via the on-demand (you have to pull down the fix) QFE patch https://na01.safelinks.protection.outlook.com/?url=https%3a%2f%2fsupport.microsoft.com%2fen-us%2fkb%2f2920193&data=01%7c01%7cbburgin%40microsoft.com%7cfacf215583da49b1555808d33a02437e%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=hwXtyPbAXZDHSdnlA3dtJ5opMt%2bYiDxC%2f7OpCZoeykk%3d and Windows 8.1 via the "important" Windows Update roll-up patch https://na01.safelinks.protection.outlook.com/?url=https%3a%2f%2fsupport.microsoft.com%2fen-us%2fkb%2f2919355&data=01%7c01%7cbburgin%40microsoft.com%7cfacf215583da49b1555808d33a02437e%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=JDXNArgPx%2bRmCB6ayXL7Oy3Dat0LVK9AZryu1UTR7f8%3d is also included in Windows 10.
>
> The end-user scenarios that were reported back in 2013 was that the feature Windows Server Backup did not work when the target SMB2 server was a dialect 2.1 and above and, as was discovered as the root-cause, the server did not support FSCTL_LMR_REQUEST_RESILIENCY.  Samba servers at the time returned STATUS_NOT_SUPPORTED.  An API that Windows Server Backup relied on, CreateVirtualDisk(), did not consider FSCTL_LMR_REQUEST_RESILIENCY as an optional feature when the dialect was 2.1 or greater.  If the request for resiliency was not supported, the API failed and so did the feature.  The fix was to continue to request if FSCTL_LMR_REQUEST_RESILIENCY is supported (when the negotiated dialect is 2.1 or greater), but NOT to consider a response of STATUS_NOT_SUPPORTED as a hard failure.  This also affected other callers of CreateVirtualDisk(), which included using the Hyper-V Manager to create a new hard disk on a remote share.
>
> I tested both Windows Server Backup on a Windows Server 2016 TP4 box and creating a VHDX from a Windows 10 box using the Hyper-V Manager against a server I modified to always return STATUS_NOT_SUPPORTED to FSCTL_LMR_REQUEST_RESILIENCY requests.  I am satisfied that the issue that was reported in 2013 and fixed soon thereafter continues to be fixed in Windows 10 and Server 2016.
>
> If you have reports of issues, we would be very interested if additional information becomes available.  But, if there is a failure, it is likely a different root-cause that would need to be investigated.
>
> Bryan
>