Re: [PATCH 2/2] [RFC] fadvise: Add _VOLATILE,_ISVOLATILE, and_NONVOLATILE flags

[John Stultz]

On Thu, 2012-02-16 at 19:43 -0800, John Stultz wrote:
> On Sun, 2012-02-12 at 13:48 +0100, Dmitry Adamushko wrote:
> > 
> > On 10 February 2012 01:16, John Stultz <john.stultz@xxxxxxxxxx> wrote:
> 
> >         +static inline void volatile_range_shrink(struct
> >         volatile_range *range,
> >         +                               pgoff_t start_index, pgoff_t
> >         end_index)
> >         +{
> >         +       size_t pre = range_size(range);
> >         +
> >         +       range->range_node.start = start_index;
> >         +       range->range_node.end = end_index;
> >         +
> > 
> > I guess, here we get a whole range of races with volatile_shrink(),
> > which may see inconsistent (in-the-middle-of-update) ranges
> > (e.g. .start and .end).
> 
> We should be holding the vlist_mutex to avoid any such races. But you
> also make clear that volatile_range_shrink() should really be called
> volatile_range_resize(), since having two _shrink calls is terrible. My
> apologies.

And sure enough in the shrinker we're not holding the vlist_mutex.
Thanks for pointing that out. 
-john

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