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

[Ming Lei]

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
patch:

	https://marc.info/?l=linux-scsi&m=150703956929333&w=2

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.

--
Ming