Re: [PATCH v4 05/11] mm: do not split a folio if it has minimum folio order requirement

[Matthew Wilcox]

On Thu, Apr 25, 2024 at 01:37:40PM +0200, Pankaj Raghav (Samsung) wrote:
> From: Pankaj Raghav <p.raghav@xxxxxxxxxxx>
> 
> Splitting a larger folio with a base order is supported using
> split_huge_page_to_list_to_order() API. However, using that API for LBS
> is resulting in an NULL ptr dereference error in the writeback path [1].
> 
> Refuse to split a folio if it has minimum folio order requirement until
> we can start using split_huge_page_to_list_to_order() API. Splitting the
> folio can be added as a later optimization.
> 
> [1] https://gist.github.com/mcgrof/d12f586ec6ebe32b2472b5d634c397df

Obviously this has to be tracked down and fixed before this patchset can
be merged ... I think I have some ideas.  Let me look a bit.  How
would I go about reproducing this?