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Date: Mon, 18 Jan 2010 11:00:19 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
To: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Wu Fengguang <fengguang.wu@intel.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       Al Viro <viro@zeniv.linux.org.uk>,
       Heiko Carstens <heiko.carstens@de.ibm.com>,
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       David Howells <dhowells@redhat.com>, Jonathan Corbet <corbet@lwn.net>,
       <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH 6/6] vfs: introduce FMODE_NEG_OFFSET for allowing
 negative f_pos
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On Mon, 18 Jan 2010 10:38:27 +0900
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> wrote:

> KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> writes:
> 
> >> So, lseek() returns (uses) it?
> >
> > lseek can return negative value, as far as I know.
> 
> Umm..., how do you know the difference of -EOVERFLOW and fpos == -75? 
> 

Ah, sorry. I read wrong.

For /dev/mem, it uses its own lseek function which allows negative f_pos
value. Other usual file system doesn't allow negative f_pos.

It's ok not to return -EOVEFLOW for /dev/mem because there is no file end.

Thanks,
-Kame