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Date: Wed, 12 Nov 2014 10:32:16 +0200
From: Konstantin Belousov <kostikbel@gmail.com>
To: Marcel Moolenaar <marcel@FreeBSD.org>
Subject: Re: svn commit: r274410 - head/usr.bin/mkimg
Message-ID: <20141112083216.GK17068@kib.kiev.ua>
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On Wed, Nov 12, 2014 at 12:10:27AM +0000, Marcel Moolenaar wrote:
> Author: marcel
> Date: Wed Nov 12 00:10:27 2014
> New Revision: 274410
> URL: https://svnweb.freebsd.org/changeset/base/274410
> 
> Log:
>   SEEK_DATA has interesting behaviour for sparse files on ZFS.  A sparse file
>   with 128K of random data and truncated to 800K can have SEEK_DATA return -1
>   when given an offset of 128K. On UFS, the SEEK_DATA returns 800K (the size
>   of the file). SEEK_HOLE on ZFS seems to behave the same as UFS.
BTW, this is because UFS cannot have hole at the end of file.
The file you describe has the last block allocated on UFS.