Re: [PATCH 3/3] cma: move allocation from HIGHMEM to a helper function

[David Hildenbrand]

On 03.07.25 11:53, Oscar Salvador wrote:
> On Wed, Jul 02, 2025 at 08:36:05PM +0300, Mike Rapoport wrote:
> > From: "Mike Rapoport (Microsoft)" <rppt@xxxxxxxxxx>
> >
> > When CONFIG_HIGMEM is enabled, __cma_declare_contiguous_nid() first
> > tries to allocate the area from HIGHMEM and if that fails it falls back
> > to allocation from low memory.
> >
> > Split allocation from HIGMEM into a helper function to further decouple
> > logic related to CONFIG_HIGHMEM.
> >
> > Signed-off-by: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx>
> > ---
> >   mm/cma.c | 52 +++++++++++++++++++++++++++++-----------------------
> >   1 file changed, 29 insertions(+), 23 deletions(-)
> >
> > diff --git a/mm/cma.c b/mm/cma.c
> > index 1df8ff312d99..0a24c46f3296 100644
> > --- a/mm/cma.c
> > +++ b/mm/cma.c
> > @@ -376,6 +376,30 @@ static int __init cma_fixed_reserve(phys_addr_t base, phys_addr_t size)
> >   	return 0;
> >   }
> >   
> > +static phys_addr_t __init cma_alloc_highmem(phys_addr_t base, phys_addr_t size,
> > +			phys_addr_t align, phys_addr_t *limit, int nid)
> > +{
> > +	phys_addr_t addr = 0;
> > +
> > +	if (IS_ENABLED(CONFIG_HIGHMEM)) {
> > +		phys_addr_t highmem = __pa(high_memory - 1) + 1;
> > +
> > +		/*
> > +		 * All pages in the reserved area must come from the same zone.
> > +		 * If the requested region crosses the low/high memory boundary,
> > +		 * try allocating from high memory first and fall back to low
> > +		 * memory in case of failure.
> > +		 */
> > +		if (base < highmem && *limit > highmem) {
> > +			addr = memblock_alloc_range_nid(size, align, highmem,
> > +							*limit, nid, true);
> > +			*limit = highmem;
> > +		}
> > +	}
>
> Not a big deal, but maybe better to do it in one function? 

Yes, same thought here.

--
Cheers,

David / dhildenb