linux-kernel - Re: [PATCH] VFS: make file->f_pos access atomic on 32bit arch

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Message-ID: <476002.75149.qm@web26206.mail.ukl.yahoo.com>
Date:	Tue, 16 Sep 2008 13:57:54 +0000 (GMT)
From:	Michael Trimarchi <trimarchimichael@...oo.it>
To:	Nick Piggin <nickpiggin@...oo.com.au>
Cc:	Hisashi Hifumi <hifumi.hisashi@....ntt.co.jp>,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] VFS: make file->f_pos access atomic on 32bit arch

Hi,



----- Messaggio originale -----
> Da: Nick Piggin <nickpiggin@...oo.com.au>
> A: Michael Trimarchi <trimarchimichael@...oo.it>
> Cc: Hisashi Hifumi <hifumi.hisashi@....ntt.co.jp>; akpm@...ux-foundation.org; linux-kernel@...r.kernel.org; linux-fsdevel@...r.kernel.org
> Inviato: Martedì 16 settembre 2008, 14:54:21
> Oggetto: Re: [PATCH] VFS: make file->f_pos access atomic on 32bit arch
> 
> On Tuesday 16 September 2008 21:11, Michael Trimarchi wrote:
> > Hi,
> >
> > > +        if (offset != file_pos_read(file))
> > > +            file_pos_write(file, offset);
> > >         retval = offset;
> > >     }
> >
> > Is not more efficient here a compare xchg operation?
> 
> The compiler should do it if it was.
> --
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 i was thinking about introducing a file_pos_update() not implemented using 
file_pos_read()/file_pos_write() and taking the seq_lock or 
disabling preemption only one time

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