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

Pavel Machek
2008-10-09T12:33:56Z

On Tue 2008-10-07 20:52:09, Matthew Wilcox wrote:
> On Wed, Oct 08, 2008 at 01:35:44PM +1100, Nick Piggin wrote:
> > Right you are. That's the fundamental question. The actual details of
> > the fix and how likely the race is don't really matter until we
> > answer the first question (except to say that the "fix" is never going
> > to be free).
> >
> > We've lasted this long with the current semantics. So the natural
> > reaction to anything that strengthens the semantics now is "why?". If
> > we do that then we can basically never return to the weaker semantics.
> > So there had better be a really good reason.
>
> And it's worth saying that letter-of-the-standard arguments aren't
> necessarily enough. Linux does not honour the POSIX guarantee that
> writes are atomic (if they cross page boundaries, it's not certain).
> This seems like even more of a corner case to me.

We have append-only files, and normal users should not be able to work
around that restriction.
Pavel
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