Re: [PATCH] mm/page_alloc: Make alloc_gigantic_page() available for general use

[David Hildenbrand]

On 16.10.19 12:28, Anshuman Khandual wrote:
> On 10/16/2019 02:28 PM, Michal Hocko wrote:
> > On Wed 16-10-19 13:04:53, Anshuman Khandual wrote:
> > > HugeTLB helper alloc_gigantic_page() implements fairly generic allocation
> > > method where it scans over various zones looking for a large contiguous pfn
> > > range before trying to allocate it with alloc_contig_range(). Other than
> > > deriving the requested order from 'struct hstate', there is nothing HugeTLB
> > > specific in there. This can be made available for general use to allocate
> > > contiguous memory which could not have been allocated through the buddy
> > > allocator.
> > >
> > > alloc_gigantic_page() has been split carving out actual allocation method
> > > which is then made available via new alloc_contig_pages() helper wrapped
> > > under CONFIG_CONTIG_ALLOC. All references to 'gigantic' have been replaced
> > > with more generic term 'contig'. Allocated pages here should be freed with
> > > free_contig_range() or by calling __free_page() on each allocated page.
> >
> > Do we want to export this to modules? Apart from mostly styling issues
> > pointed by David this looks fine.
> >
> > I do agree that a general allocator api belongs to page_alloc.c rather
> > than force people to invent their own and broken instances.
> >   
> > > Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
> > > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > > Cc: Vlastimil Babka <vbabka@xxxxxxx>
> > > Cc: Michal Hocko <mhocko@xxxxxxxx>
> > > Cc: David Rientjes <rientjes@xxxxxxxxxx>
> > > Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
> > > Cc: Oscar Salvador <osalvador@xxxxxxx>
> > > Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
> > > Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx>
> > > Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> > > Cc: Pavel Tatashin <pavel.tatashin@xxxxxxxxxxxxx>
> > > Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
> > > Cc: David Hildenbrand <david@xxxxxxxxxx>
> > > Cc: linux-kernel@xxxxxxxxxxxxxxx
> > > Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> >
> > After other issues mentioned by David get resolved you can add
>
> Just to confirm. Only the styling issues, right ? pfn_range_valid_contig(),
> pfn alignment and zone scanning all remain the same like before ?

Fine with me. Please do think about the alignment thingy. (I suggest to 
just enforce an alignment to a power of two for now (and return NULL if 
not a power of two), we can always relax that when needed - and then 
think about a better search for !power of two)

--

Thanks,

David / dhildenb