Re: [RFC PATCH v2 4/7] mm: pgtable: try to reclaim empty PTE pages in zap_page_range_single()

[Qi Zheng]

On 2024/8/16 18:03, David Hildenbrand wrote:
> > > (b) if we didn't have to drop the PTL, we can remove the page table
> > >       without even re-verifying whether the entries are pte_none(). We
> >
> > If we want to remove the PTE page, we must hold the pmd lock (for
> > clearing pmd entry). To prevent ABBA deadlock, we must first release the
> > pte lock and then re-acquire the pmd lock + pte lock. Right? If so, then
> > rechecking pte_none() is unavoidable. Unless we hold the pmd lock + pte
> > lock in advance to execute the original code loop.
>
> Try-locking the PMD should work, and succeed in many cases, right? And 
> if that fails, we could fallback to what you describe.

Ah, right, I got it! Will try to do it in the next version.

Thanks,
Qi

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