Re: [PATCH V8 5/8] percpu-refcount: introduce __percpu_ref_tryget_live

From: Ming Lei
Date: Tue Oct 03 2017 - 15:20:59 EST

On Tue, Oct 03, 2017 at 07:14:59AM -0700, Tejun Heo wrote:
> Hello,
> On Tue, Oct 03, 2017 at 10:04:03PM +0800, Ming Lei wrote:
> > Block layer need to call this function after holding
> > rcu lock in a real hot path, so introduce this helper.
> The patch description is too anemic. It doesn't even describe what
> changes are being made, let alone justifying them.

Sorry for Cc you, and this change is needed by the following

Block layer need to call percpu_ref_tryget_live()
with holding RCU read lock, given it is a hot I/O
path, that is why I make this patch so that we can
avoid nested RCU read lock and save a bit cost.