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From: Muchun Song In-Reply-To: <3DA11168-5E37-4CE9-9934-CD1CAF3085D6@nvidia.com> Date: Thu, 29 Jan 2026 11:23:58 +0800 Cc: Kiryl Shutsemau , Andrew Morton , David Hildenbrand , Matthew Wilcox , Usama Arif , Frank van der Linden , Oscar Salvador , Mike Rapoport , Vlastimil Babka , Lorenzo Stoakes , Baoquan He , Michal Hocko , Johannes Weiner , Jonathan Corbet , Huacai Chen , WANG Xuerui , Palmer Dabbelt , Paul Walmsley , Albert Ou , Alexandre Ghiti , kernel-team@meta.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, loongarch@lists.linux.dev, linux-riscv@lists.infradead.org Content-Transfer-Encoding: quoted-printable Message-Id: <1A08D224-E1AC-4FE5-B1D0-1BAE2D5FF31E@linux.dev> References: <20260128135500.22121-1-kas@kernel.org> <20260128135500.22121-10-kas@kernel.org> <3DA11168-5E37-4CE9-9934-CD1CAF3085D6@nvidia.com> To: Zi Yan X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 5DC8920006 X-Stat-Signature: gruxf5dnpcd9qdf1pj3qtkecxbyg3x39 X-Rspam-User: X-HE-Tag: 1769657085-268484 X-HE-Meta: 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 Q5q0JSPv C3EWCTUAMaYDqyKdXpT0Xs2LS0G49/jO1Lkunfs1m6ZZizOYYqrGBElQUlLULkgzDrVZc8pNdn+etjd6izUCPnw3VSWZyHWfX+AbKBcn6K0XtIaRsalglthFhmdEtGv5DgOp+ysEY6kKwi09c1q6Yv0VbJnqUtrZDGeFEv2Nb1g0Vbw3/R87uVdt6+bArtdtDuMXuoq/GFkVs5e2OLhowt7nIOhnZct6HLkfLhDWcVNBqj58t4g71n+fVwP4KTTJDV0DWUhVHewlu0wvT2cihIpdHYiGqTrlZg3wWCzVipY57Yy09Wx+Y9zN76Ry5SMyqCX02VUtkm6HYZkE= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > On Jan 29, 2026, at 11:10, Zi Yan wrote: >=20 > On 28 Jan 2026, at 22:00, Muchun Song wrote: >=20 >>> On Jan 28, 2026, at 21:54, Kiryl Shutsemau wrote: >>>=20 >>> If page->compound_info encodes a mask, it is expected that vmemmap = to be >>> naturally aligned to the maximum folio size. >>>=20 >>> Trigger a BUG() for CONFIG_DEBUG_VM=3Dy or WARN() otherwise. >>>=20 >>> Signed-off-by: Kiryl Shutsemau >>> Acked-by: Zi Yan >>> --- >>> mm/sparse.c | 13 +++++++++++++ >>> 1 file changed, 13 insertions(+) >>>=20 >>> diff --git a/mm/sparse.c b/mm/sparse.c >>> index b5b2b6f7041b..9c0f4015778c 100644 >>> --- a/mm/sparse.c >>> +++ b/mm/sparse.c >>> @@ -600,6 +600,19 @@ void __init sparse_init(void) >>> BUILD_BUG_ON(!is_power_of_2(sizeof(struct mem_section))); >>> memblocks_present(); >>>=20 >>> + if (compound_info_has_mask()) { >>> + unsigned long alignment; >>> + bool aligned; >>> + >>> + alignment =3D MAX_FOLIO_NR_PAGES * sizeof(struct page); >>> + aligned =3D IS_ALIGNED((unsigned long) pfn_to_page(0), = alignment); >>> + >>> + if (IS_ENABLED(CONFIG_DEBUG_VM)) >>> + BUG_ON(!aligned); >>> + else >>> + WARN_ON(!aligned); >>=20 >> Since you=E2=80=99ve fixed all the problematic architectures, I = don=E2=80=99t believe >> we=E2=80=99ll ever hit the WARN or BUG here anymore. >>=20 >> I think we can now simplify the code further and just use VM_BUG_ON: >> if any architecture changes in the future, the misalignment will be >> caught during testing, so we won=E2=80=99t need to worry about it at = run-time. >>=20 >=20 > VM_WARN_ON should be sufficient, since bots should report warnings > from any patch/change. I=E2=80=99m not sure a WARN will get developers=E2=80=99 attention, = since the message is unlikely to have any visible consequences and only fires on allocations with a special order. >=20 >>> + } >>> + >>> pnum_begin =3D first_present_section_nr(); >>> nid_begin =3D sparse_early_nid(__nr_to_section(pnum_begin)); >>>=20 >>> --=20 >>> 2.51.2 >>>=20 >=20 >=20 > Best Regards, > Yan, Zi