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From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Fri, 8 Jun 2012 15:06:20 -0700
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Subject: Re: [RFC, PATCH] fs: push rcu_barrier() from deactivate_locked_super()
 to filesystems
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Boaz Harrosh <bharrosh@panasas.com>, Tao Ma <boyu.mt@taobao.com>,
        Andrew Morton <akpm@linux-foundation.org>,
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On Fri, Jun 8, 2012 at 3:00 PM, Kirill A. Shutemov
<kirill.shutemov@linux.intel.com> wrote:
>
> IIUC, moving rcu_barrier() up should help, but I can't say that I fully
> understand SLAB_DESTROY_BY_RCU semantics.

.. hmm. I think you may be right. Even if we do move it up, we
probably shouldn't use it.

We don't even want SLAB_DESTROY_BY_RCU, since we do the delayed RCU
free for other reasons anyway, so it would duplicate the RCU delaying
and cause problems. I forgot about that little complication.

We could have a separate "RCU_BARRIER_ON_DESTROY" thing, but that's
just silly too.

Maybe your patch is the right thing.

            Linus
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