Re: [PATCH] mm/sparse: remove unnecessary NULL check before allocating mem_section

[Sang-Heon Jeon <ekffu200098@gmail.com>]

Hi

On Mon, Apr 20, 2026 at 3:49 PM Mike Rapoport <rppt@kernel.org> wrote:
>
> Hi,
>
> On Sun, Apr 19, 2026 at 11:42:25PM +0900, Sang-Heon Jeon wrote:
> > Commit 850ed20539a4 ("mm: move array mem_section init code out
> > of memory_present()") moved mem_section allocation logic
> > into memblocks_present().
> >
> > Before that move, memory_present() could be called multiple times, so
> > unlikely() matched the common case, where most calls found mem_section
> > already allocated.
> >
> > After that move, memblocks_present() is called exactly once from
> > sparse_init(). Under CONFIG_SPARSEMEM_EXTREME, mem_section is always
> > NULL when it is called.
> >
> > So remove unnecessary NULL check before allocating mem_section. No
> > functional change.
> >
> > Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com>
>
> Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
>
> > ---
> > Hello,
> >
> > While looking into boot information, I found a minor enhancement point.
> > If I misunderstood anything, please feel free to let me know.
>
> I would say it's more a cleanup than enhancement :)

You're right. Thanks for your kind review. That's my poor english :-(

> > Thank you for taking valuable time to review this work.
> >
> > Best Regards,
> > Sang-Heon Jeon
> > ---
> >  mm/sparse.c | 10 ++++------
> >  1 file changed, 4 insertions(+), 6 deletions(-)
> >
> > diff --git a/mm/sparse.c b/mm/sparse.c
> > index effdac6b0ab1..e13f9f5fa090 100644
> > --- a/mm/sparse.c
> > +++ b/mm/sparse.c
> > @@ -201,13 +201,11 @@ static void __init memblocks_present(void)
> >       int i, nid;
> >
> >  #ifdef CONFIG_SPARSEMEM_EXTREME
> > -     if (unlikely(!mem_section)) {
> > -             unsigned long size, align;
> > +     unsigned long size, align;
> >
> > -             size = sizeof(struct mem_section *) * NR_SECTION_ROOTS;
> > -             align = 1 << (INTERNODE_CACHE_SHIFT);
> > -             mem_section = memblock_alloc_or_panic(size, align);
> > -     }
> > +     size = sizeof(struct mem_section *) * NR_SECTION_ROOTS;
> > +     align = 1 << (INTERNODE_CACHE_SHIFT);
> > +     mem_section = memblock_alloc_or_panic(size, align);
> >  #endif
> >
> >       for_each_mem_pfn_range(i, MAX_NUMNODES, &start, &end, &nid)
> > --
> > 2.43.0
> >
>
> --
> Sincerely yours,
> Mike.

Best Regards,
Sang-Heon Jeon