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Mon, 20 Apr 2026 05:55:44 -0700 (PDT) MIME-Version: 1.0 References: <20260419144225.2875654-1-ekffu200098@gmail.com> In-Reply-To: From: Sang-Heon Jeon Date: Mon, 20 Apr 2026 21:55:32 +0900 X-Gm-Features: AQROBzB1tVXHHOLPdJ_CWIQhP3lrfUl7ID8IyuEaGjHJyd0xcaXhnBb-DShBw_I Message-ID: Subject: Re: [PATCH] mm/sparse: remove unnecessary NULL check before allocating mem_section To: Mike Rapoport Cc: akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, surenb@google.com, mhocko@suse.com, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: q8oqtf9dnb75xbuhxn8tcymojrrwnefd X-Rspamd-Queue-Id: 369D812000B X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1776689745-96276 X-HE-Meta: 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 UkoEOEHD 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi On Mon, Apr 20, 2026 at 3:49=E2=80=AFPM Mike Rapoport wro= te: > > 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 > > Acked-by: Mike Rapoport (Microsoft) > > > --- > > 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 =3D sizeof(struct mem_section *) * NR_SECTION_ROOTS; > > - align =3D 1 << (INTERNODE_CACHE_SHIFT); > > - mem_section =3D memblock_alloc_or_panic(size, align); > > - } > > + size =3D sizeof(struct mem_section *) * NR_SECTION_ROOTS; > > + align =3D 1 << (INTERNODE_CACHE_SHIFT); > > + mem_section =3D 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