Re: [RFC PATCH 3/3] mm, fault_around: do not take a reference to a locked page

[Michal Hocko]

On Tue 20-11-18 17:17:00, Kirill A. Shutemov wrote:
> On Tue, Nov 20, 2018 at 03:12:07PM +0100, Michal Hocko wrote:
> > On Tue 20-11-18 17:07:15, Kirill A. Shutemov wrote:
> > > On Tue, Nov 20, 2018 at 02:43:23PM +0100, Michal Hocko wrote:
> > > > From: Michal Hocko <mhocko@xxxxxxxx>
> > > > 
> > > > filemap_map_pages takes a speculative reference to each page in the
> > > > range before it tries to lock that page. While this is correct it
> > > > also can influence page migration which will bail out when seeing
> > > > an elevated reference count. The faultaround code would bail on
> > > > seeing a locked page so we can pro-actively check the PageLocked
> > > > bit before page_cache_get_speculative and prevent from pointless
> > > > reference count churn.
> > > 
> > > Looks fine to me.
> > 
> > Thanks for the review.
> > 
> > > But please drop a line of comment in the code. As is it might be confusing
> > > for a reader.
> > 
> > This?
> 
> Yep.
> 
> Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>

Cool, thanks! I will wait some more time for review feedback for other
patches and then repost with this folded in.

-- 
Michal Hocko
SUSE Labs