linux-kernel - Re: [PATCH] percpu-refcount: support synchronous switch to atomic mode.

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Message-ID: <20170323022020.buq4us3lvp2jbyes@kernel.org>
Date:   Wed, 22 Mar 2017 19:20:20 -0700
From:   Shaohua Li <shli@...nel.org>
To:     Tejun Heo <tj@...nel.org>
Cc:     NeilBrown <neilb@...e.com>, Christoph Lameter <cl@...ux.com>,
        linux-kernel@...r.kernel.org,
        Linux-RAID <linux-raid@...r.kernel.org>
Subject: Re: [PATCH] percpu-refcount: support synchronous switch to atomic
 mode.

On Wed, Mar 22, 2017 at 11:00:29AM -0400, Tejun Heo wrote:
> On Wed, Mar 22, 2017 at 12:50:12PM +1100, NeilBrown wrote:
> > 
> > percpu_ref_switch_to_atomic_sync() schedules the switch
> > to atomic mode, then waits for it to complete.
> > 
> > Also export percpu_ref_switch_to_* so they can be used from modules.
> > 
> > This will be used in md/raid to count the number of pending write
> > requests to an array.
> > We occasionally need to check if the count is zero, but most often
> > we don't care.
> > We always want updates to the counter to be fast, as in some cases
> > we count every 4K page.
> > 
> > Signed-off-by: NeilBrown <neilb@...e.com>
> 
> Acked-by: Tejun Heo <tj@...nel.org>
> 
> Please feel free to route through other patches through md tree.  If
> preferable, I can route it through percpu/for-4.12.

Thanks, Tejun. I applied it to md tree, that will avoid a lot of troubles.

Thanks,
Shaohua