Re: [PATCH 19/19] mm: memcontrol: update page->mem_cgroup stability rules

[Michal Hocko]

On Fri 08-05-20 14:31:06, Johannes Weiner wrote:
> The previous patches have simplified the access rules around
> page->mem_cgroup somewhat:
> 
> 1. We never change page->mem_cgroup while the page is isolated by
>    somebody else. This was by far the biggest exception to our rules
>    and it didn't stop at lock_page() or lock_page_memcg().
> 
> 2. We charge pages before they get put into page tables now, so the
>    somewhat fishy rule about "can be in page table as long as it's
>    still locked" is now gone and boiled down to having an exclusive
>    reference to the page.
> 
> Document the new rules. Any of the following will stabilize the
> page->mem_cgroup association:
> 
> - the page lock
> - LRU isolation
> - lock_page_memcg()
> - exclusive access to the page
> 
> Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> Reviewed-by: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
> Reviewed-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>

Thanks a lot this is a big improvement and simplification.

I have gone through the whole series finally. I have followed up where
necessary but overall this is really nice!

Sorry I couldn't jump in to review in time.
-- 
Michal Hocko
SUSE Labs