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Subject: Re: Better interop for NFS/SMB file share mode/reservation
To:     Amir Goldstein <amir73il@gmail.com>,
        Pavel Shilovskiy <pshilov@microsoft.com>
Cc:     "linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>,
        "Volker.Lendecke@sernet.de" <Volker.Lendecke@sernet.de>,
        Jeff Layton <jlayton@kernel.org>,
        "samba-technical@lists.samba.org" <samba-technical@lists.samba.org>,
        Trond Myklebust <trondmy@hammerspace.com>,
        "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>
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From:   Uri Simchoni <uri@samba.org>
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Date:   Tue, 30 Apr 2019 11:12:28 +0300
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On 4/30/19 3:31 AM, Amir Goldstein via samba-technical wrote:
>>
>> About O_DENYDELETE: I don't understand how we may reach a good interop story without a proper implementation of this flag. Windows apps may set it and Samba needs to respect it. If an NFS client removes such an opened file, what will Samba tell the Windows client?
>>
> 
> Samba will tell the Windows client:
> "Sorry, my administrator has decided to trade off interop with nfs on
> share modes,
> with DENY_DELETE functionality, so I cannot grant you DENY_DELETE that you
> requested."
> Not sure if that is workable. Samba developers need to chime in.
> 
> Thanks,
> Amir.
> 

On Windows you don't ask for DENY_DELETE, you get it by default unless
you ask to *allow* deletion. If you fopen() a file, even for
reading-only, the MSVC standard C library would open it with delete
denied because it does not explicitly request to allow it. My guess is
that runtimes of other high-level languages behave that way too on
Windows. That means pretty much everything would stop working.

Thanks,
Uri.