[Samba] (DeviceIoControl, FSCTL_SET_SPARSE)

David Disseldorp ddiss at samba.org
Tue Feb 14 10:54:49 UTC 2017

Hi Brian,

On Mon, 13 Feb 2017 19:16:13 -0800, brian lamb via samba wrote:

> Im having an issue with what I believe might be pinned down to a need for a
> proper samba configuration. 

Which version of Samba are you using?

> The problem: sparse writes (not sure which, either write sparse files to a
> system that doesn't support them, or vice versa)

What doesn't support sparse writes? How do you know that the problem is
related to sparse files?

> The system:
> Zfs-on-linux, samba share

ZFS on Linux + Samba supports sparse files...

> Accessing system which is erroring:
> Win7x64_ult, freefilesync
> Error message

What's the error message? Has this application ever worked successfully
against Samba, or only against a Windows share?

> NOTHING I have done to it is fixing, including 
> strict allocate = yes
> strict allocate = no
> share:fake_fscaps = 0
> #share:fake_fscaps = 0

Windows clients request sparse file semantics explicitly, by calling
FSCTL_SET_SPARSE. Samba then retains this flag in the "user.DOSATTRIB"
extended attribute for the given file.
One way to modify this behaviour would be to set "store dos attributes"
to "no" in smb.conf - this would see Samba respond to any
said, I have no idea whether or not this will fix the application error
that you're seeing.

Cheers, David

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