Re: [PATCH v3 11/26] x86/numa: use get_pfn_range_for_nid to verify that node spans memory

Mike Rapoport
2024-08-05T20:38:18Z

On Mon, Aug 05, 2024 at 01:03:56PM -0700, Dan Williams wrote:
> Mike Rapoport wrote:
> > From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
> >
> > Instead of looping over numa_meminfo array to detect node's start and
> > end addresses use get_pfn_range_for_init().
> >
> > This is shorter and make it easier to lift numa_memblks to generic code.
> >
> > Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> > Tested-by: Zi Yan <ziy@nvidia.com> # for x86_64 and arm64
> > ---
> > arch/x86/mm/numa.c | 13 +++----------
> > 1 file changed, 3 insertions(+), 10 deletions(-)
> >
> > diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
> > index edfc38803779..cfe7e5477cf8 100644
> > --- a/arch/x86/mm/numa.c
> > +++ b/arch/x86/mm/numa.c
> > @@ -521,17 +521,10 @@ static int __init numa_register_memblks(struct numa_meminfo *mi)
> >
> > /* Finally register nodes. */
> > for_each_node_mask(nid, node_possible_map) {
> > - u64 start = PFN_PHYS(max_pfn);
> > - u64 end = 0;
> > + unsigned long start_pfn, end_pfn;
> >
> > - for (i = 0; i < mi->nr_blks; i++) {
> > - if (nid != mi->blk[i].nid)
> > - continue;
> > - start = min(mi->blk[i].start, start);
> > - end = max(mi->blk[i].end, end);
> > - }
> > -
> > - if (start >= end)
> > + get_pfn_range_for_nid(nid, &start_pfn, &end_pfn);
> > + if (start_pfn >= end_pfn)
>
> Assuming I understand why this works, would it be worth a comment like:
>
> "Note, get_pfn_range_for_nid() depends on memblock_set_node() having
> already happened"

Will add a comment, sure.

> ...at least that context was not part of the diff so took me second to
> figure out how this works.
>

--
Sincerely yours,
Mike.