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SubjectRe: [PATCH 07/17] fs: icache atomic inodes_stat
On Wed, Sep 29, 2010 at 09:52:53PM -0700, Andrew Morton wrote:
> On Wed, 29 Sep 2010 22:18:39 +1000 Dave Chinner <david@fromorbit.com> wrote:
> > From: Nick Piggin <npiggin@suse.de>
> >
> > The inode use statistics are currently protected by the inode_lock.
> > Before we can remove the inode_lock, we need to protect these
> > counters against races. Do this by converting them to atomic
> > counters so they ar enot dependent on any lock at all.
>
> typo

It's Dave, I swear :)


> > +struct inodes_stat_t {
> > + atomic_t nr_inodes;
> > + atomic_t nr_unused;
> > + int dummy[5]; /* padding for sysctl ABI compatibility */
> > +};
>
> OK, that's a hack. The first two "ints" are copied out to userspace.
> This change assumes that sizeof(atomic_t)=4 and that an atomic_t has
> the same layout, alignment and padding as an int.
>
> Probably that's true in current kernels and with current architectures
> but it's a hack and it's presumptive.
>
> It shouldn't be snuck into the tree unchangelogged and uncommented.
>
> (time passes)
>
> OK, I see that all of this gets reverted later on. Please update the
> changelog so the next reviewer doesn't get fooled.

Yeah it is. I might end up folding the per-cpu stuff back over it
and avoid the issue completely. Otherwise I'll add a comment.



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