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From: Muchun Song In-Reply-To: Date: Wed, 1 Apr 2026 15:28:02 +0800 Cc: Muchun Song , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Frank van der Linden , linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: <462D1EBC-22B7-4527-B725-6DED308D428E@linux.dev> References: <20260331113724.2080833-1-songmuchun@bytedance.com> <17246161-f314-45da-933a-770231ef2a49@kernel.org> <2183487D-0CED-4BEF-84D7-4439F3386584@linux.dev> To: "David Hildenbrand (Arm)" X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: A8E7880010 X-Stat-Signature: sjcwuq5hwe79od4esj6ybejbdw61c75i X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1775028521-229567 X-HE-Meta: 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 VyCH0o6L kz+ZH8TC03VYpDnw5CQjOTzpJwWyu55Uk8Pl5aEMIsOH6c37e2cHcQzzBQRSNMPRYawbfpDX4J9Q2W6hATn2S/Cb56s84my362UbpfCFzLKPxwLVVaDiRPIAhd1k2uNg91lHZseqxyApauNO96P1oZrsm565fluyfjaEhy+PqzzqBhe1SKmSdIQrFLC8PzTaPTbi+jfIFFbdhMoNr8EAvzPwkP4yrUv6wAtGQKy4twfo80F1JOqGzFkZe4cIhu3eS6L3gjJ+pShN+Gg+mlPJREjgz6qlqcCq0apBXTDw4N/TLm+LbdJR2VNi7EcXcWtFBajNp91Fyse9UFN8= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > On Apr 1, 2026, at 15:25, David Hildenbrand (Arm) = wrote: >=20 > On 4/1/26 04:41, Muchun Song wrote: >>=20 >>=20 >>> On Apr 1, 2026, at 04:42, David Hildenbrand (Arm) = wrote: >>>=20 >>> On 3/31/26 13:37, Muchun Song wrote: >>>> sparse_init_nid() is careful to leave alone every section whose = vmemmap >>>> has already been set up by sparse_vmemmap_init_nid_early(); it only >>>> clears section_mem_map for the rest: >>>>=20 >>>> if (!preinited_vmemmap_section(ms)) >>>> ms->section_mem_map =3D 0; >>>>=20 >>>> A leftover line after that conditional block >>>>=20 >>>> ms->section_mem_map =3D 0; >>>>=20 >>>> was supposed to be deleted but was missed in the failure path, = causing the >>>> field to be overwritten for all sections when memory allocation = fails, >>>> effectively destroying the pre-initialization check. >>>>=20 >>>> Drop the stray assignment so that preinited sections retain their >>>> already valid state. >>>>=20 >>>> Fixes: d65917c42373 ("mm/sparse: allow for alternate vmemmap = section init at boot") >>>> Signed-off-by: Muchun Song >>>> --- >>>> mm/sparse.c | 1 - >>>> 1 file changed, 1 deletion(-) >>>>=20 >>>> diff --git a/mm/sparse.c b/mm/sparse.c >>>> index c2eb36bfb86d..3a14b733bf71 100644 >>>> --- a/mm/sparse.c >>>> +++ b/mm/sparse.c >>>> @@ -584,7 +584,6 @@ static void __init sparse_init_nid(int nid, = unsigned long pnum_begin, >>>> ms =3D __nr_to_section(pnum); >>>> if (!preinited_vmemmap_section(ms)) >>>> ms->section_mem_map =3D 0; >>>> - ms->section_mem_map =3D 0; >>>=20 >>>=20 >>> Acked-by: David Hildenbrand (Arm) >>=20 >> Thanks. >>=20 >>>=20 >>> I have some cleanup patches lying around that cleanup that code = heavily. >>> I think I get rid of this questionable "failed to allocate" case = entirely. >>=20 >> It's truly a coincidence =E2=80=94 I also have a piece of code = locally >> that does something similar. Since allocation failure would also >> affect subsequent startup processes, I simply made it panic when >> allocation fails. >=20 > Don't use BUG_ON, use actual panic(). :) Got it. >=20 > And yes, we should rip out that handling. Agree. >=20 > --=20 > Cheers, >=20 > David