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

[Michael Trimarchi]

Hi,



----- Messaggio originale -----
> Da: Nick Piggin <nickpiggin@xxxxxxxxxxxx>
> A: Michael Trimarchi <trimarchimichael@xxxxxxxx>
> Cc: Hisashi Hifumi <hifumi.hisashi@xxxxxxxxxxxxx>; akpm@xxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-fsdevel@xxxxxxxxxxxxxxx
> 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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