Re: [PATCH 2/2] mm/hugetlb: pass correct order_per_bit to cma_declare_contiguous_nid

[Roman Gushchin]

On Thu, Apr 04, 2024 at 10:13:21PM +0200, David Hildenbrand wrote:
> On 04.04.24 18:25, Frank van der Linden wrote:
> > The hugetlb_cma code passes 0 in the order_per_bit argument to
> > cma_declare_contiguous_nid (the alignment, computed using the
> > page order, is correctly passed in).
> > 
> > This causes a bit in the cma allocation bitmap to always represent
> > a 4k page, making the bitmaps potentially very large, and slower.
> > 
> > So, correctly pass in the order instead.
> > 
> > Signed-off-by: Frank van der Linden <fvdl@xxxxxxxxxx>
> > Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx>
> > Fixes: cf11e85fc08c ("mm: hugetlb: optionally allocate gigantic hugepages using cma")
> 
> It might be subopimal, but do we call it a "BUG" that needs "fixing". I
> know, controversial :)

We probably should not rush with a stable backporting, especially given your
next comment on page sizes on arm.