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

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Message-ID: <20170322150029.GA7532@htj.duckdns.org>
Date:   Wed, 22 Mar 2017 11:00:29 -0400
From:   Tejun Heo <tj@...nel.org>
To:     NeilBrown <neilb@...e.com>
Cc:     Christoph Lameter <cl@...ux.com>, linux-kernel@...r.kernel.org,
        Shaohua Li <shli@...nel.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 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