Re: [PATCH v3 10/18] mm: Allow non-hugetlb large folios to be batch processed

[Matthew Wilcox <willy@infradead.org>]

On Thu, Mar 07, 2024 at 06:35:16PM +0000, Ryan Roberts wrote:
> I noticed commit dfa3df509576 ("mm: fix list corruption in put_pages_list")
> turned up in mm-unstable today (after I sent the above). Although I haven't done
> much of the exact testing that was previously causing oopses, I also haven't
> seen any since I rebased onto today's mm-unstable. Could that fix be helping us?

I wish.  Wrong list (lru vs deferred), and the symptom of that crash was
an immediate crash, not a deferred one.  Although maybe with the
right/wrong debugging options ...

> > The thought occurs that we don't need to take the folios off the list.
> > I don't know that will fix anything, but this will fix your "running out
> > of memory" problem -- I forgot to drop the reference if folio_trylock()
> > failed.  
> 
> Ugh, how did I not spot that! So I guess that fits the hypothesis that the
> original change is just increasing the race window and therefore we are leaking
> more folios due to the failed trylock.

It doesn't _confirm_ it, but it certainly fits the theory!
Thanks for testing.