Re: [PATCH] mm: memcontrol: remove BUG_ON in uncharge_list

[Michal Hocko <mhocko@kernel.org>]

On Wed 08-06-16 10:58:33, Johannes Weiner wrote:
> On Wed, Jun 08, 2016 at 09:25:54AM +0200, Michal Hocko wrote:
> > On Wed 08-06-16 15:00:48, roy.qing.li@gmail.com wrote:
> > > From: Li RongQing <roy.qing.li@gmail.com>
> > > 
> > > when call uncharge_list, if a page is transparent huge, and not need to
> > > BUG_ON about non-transparent huge, since nobody should be be seeing the
> > > page at this stage and this page cannot be raced with a THP split up
> > 
> > Johannes do you remember why you have kept this bug on even after
> > 0a31bc97c80c ("mm: memcontrol: rewrite uncharge API")?
> 
> No, I just copied it over without thinking too much about it. That
> patch was pretty drastic, so why not keep the sanity checks in case
> one of the many assumptions it made were flawed...

Yeah the VM_BUG_ON made sense before because the charge could have gone
away while the page could be visible, thus split.
 
> But it's probably okay to drop it at this point.

Thanks for double checking. I was just not sure I didn't miss anything.
I am always a bit nervous when bug_ons a removed.

> > > Signed-off-by: Li RongQing <roy.qing.li@gmail.com>
> 
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>

With the reference to the rewrite which made it pointless
Acked-by: Michal Hocko <mhocko@suse.com>
-- 
Michal Hocko
SUSE Labs

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