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From: Muchun Song In-Reply-To: Date: Tue, 14 Apr 2026 10:28:24 +0800 Cc: Muchun Song , Andrew Morton , Oscar Salvador , Michael Ellerman , Madhavan Srinivasan , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Nicholas Piggin , Christophe Leroy , aneesh.kumar@linux.ibm.com, joao.m.martins@oracle.com, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: References: <20260405125240.2558577-1-songmuchun@bytedance.com> <20260405125240.2558577-4-songmuchun@bytedance.com> To: "David Hildenbrand (Arm)" X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: 4055F40006 X-Stat-Signature: 8sr6nzqsq6jqcp3exzdz69ecoqafhmuo X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1776133758-925167 X-HE-Meta: U2FsdGVkX1+QedQgHtrW4PVDgAORo4gGrVV5JiZsDsFmtbtmgwltt9nMog+MmWd+d3J4dIM4hly9szGZAToYWM20aYvWNu+kcK9Pye0t7ZXWYw6Bmjo9vNgC0XykaV0uQ3Q4wgETDXJCpNM3zxMNCYvW1mSCSj+b3evSLir2cTsrX7GUzwge1FL4w7nlfpbfMfrvi8BrnGl9+cvul92xV7Gq3N1LMQNHYkjT6U2zvSmtL4sjTqsolcyMIB/lW2S0yQRK/2lL1VI6pywb5yNIxua47T1//AsKAZOMMBZJuj0avezz3genw78AQrcx1fpCGXXI+wA0BN3uDzmoHMhBYfgLpQsIJCBXYcp2TqSYfQH2px5+8DShmgqPbqw4DNxqp2Mfq7o5HUqFX6nRX5RU+vHPK3SI9/PwbmLbqItwvlAluAEOZ926ZT48GNaIAswhdvt8358yh6kEzbeQXh5SMv3AkTF62IkSI+8vZdDw36JhElBw/XDe8b8u12/QJPVk0bdJ3ScLN7Yc/lJjWHBK06i8jQqrqGrBuRJAIb+xDKMm+DdwjgAgtjdGbXpOejBwy78V42Mk/PpNHVuS0KqiAnoCPYShxc5ewCQStgm2Dixa3n4F4BH1tOOzG1uR5fTFn85pOo/M7L/r6ox0spUtYOzIfq0hrutxCYpuR26w12NUyTuaxh1n7P9PYRxQSR4E9tBcns1hL8IFAk6z4bzaYTIpnNYKK7T0BtLcKDRO/uSMT/ucegK/DQ7kgHy+vBDu4aD9wDn5+MqVNr9iNJXDb6rGz0FFY3OXSKxaKKh8o8trS5SHglYwAL8cD9mMRnFJ0UbLug+SKQ6vcovxsAH/cmR9QEIx4CRR8QpC+lbcfUmjTwPK0Nbsr6pONlBYvAqTSAtR+I+E0sheksnJ4+0l59nwaE6h36/j2DfpuTfnnqnAEb4ExOZtUqYogCBLBBiNFk7y+AnrYd9aWysyz1c OwMg2M70 5SFMT2/TC0S6fjIn0lbY/vfPlFin38b2V9+ZZMM6LDZ1euq1Y8GsAV2uUrCY12jNOMmm0cUtnUKSq6yWsS+xEdAXqTqmI3PMonyVq2kmRm/XUPFJyVWNls2/T1Z2lgnOhBBygAIF5NXNeFSdYEB6Zm+9TOQr5ztPPVV0+aaRjTrXNiXWBO04IStmK/9VydVDvAJEDrkIasOvce9ti2BgZqJZKBmYrqPpOh8+YoipTfuIjBK7jX0pA9ZW3LQ9H8Cl6hx2bZvCF7oJiJTeun11gb36Y8QN+Pw6ojLfF Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > On Apr 14, 2026, at 02:39, David Hildenbrand (Arm) = wrote: >=20 > On 4/5/26 14:51, Muchun Song wrote: >> When HVO is enabled for DAX, the vmemmap page accounting is wrong = since >> it only accounts for non-HVO case. >>=20 >> Fix the accounting by introducing section_vmemmap_pages() that = returns >> the exact number of vmemmap pages needed for the given pfn range. >=20 > I guess only the accounting in /proc/meminfo is messed up, correct? No. It is in /proc/vmstat cat /proc/vmstat | grep memmap nr_memmap_pages 0 nr_memmap_boot_pages 2097163 >=20 >>=20 >> Fixes: 15995a352474 ("mm: report per-page metadata information") >=20 > Similarly, please send all fixes out separately. Will do in next version. >=20 >> Signed-off-by: Muchun Song >> --- >> mm/sparse-vmemmap.c | 30 ++++++++++++++++++++++++++---- >> 1 file changed, 26 insertions(+), 4 deletions(-) >>=20 >> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c >> index 7aa9a97498eb..0ef96b1afbcc 100644 >> --- a/mm/sparse-vmemmap.c >> +++ b/mm/sparse-vmemmap.c >> @@ -724,6 +724,27 @@ static int fill_subsection_map(unsigned long = pfn, unsigned long nr_pages) >> return rc; >> } >>=20 >> +static int __meminit section_vmemmap_pages(unsigned long pfn, = unsigned long nr_pages, >> + struct vmem_altmap *altmap, struct dev_pagemap *pgmap) >> +{ >> + unsigned int order =3D pgmap ? pgmap->vmemmap_shift : 0; >> + unsigned long pages_per_compound =3D 1L << order; >> + >> + VM_BUG_ON(!IS_ALIGNED(pfn | nr_pages, min(pages_per_compound, = PAGES_PER_SECTION))); >> + VM_BUG_ON(pfn_to_section_nr(pfn) !=3D pfn_to_section_nr(pfn + = nr_pages - 1)); >=20 > No new VM_BUG_ON. Ever. :) >=20 > VM_WARN_ON_ONCE() is your friend. Got it. >=20 >> + >> + if (!vmemmap_can_optimize(altmap, pgmap)) >> + return DIV_ROUND_UP(nr_pages * sizeof(struct page), = PAGE_SIZE); >> + >> + if (order < PFN_SECTION_SHIFT) >> + return VMEMMAP_RESERVE_NR * nr_pages / = pages_per_compound; >> + >> + if (IS_ALIGNED(pfn, pages_per_compound)) >> + return VMEMMAP_RESERVE_NR; >> + >> + return 0; >> +} >> + >> /* >> * To deactivate a memory region, there are 3 cases to handle: >> * >> @@ -775,11 +796,12 @@ static void section_deactivate(unsigned long = pfn, unsigned long nr_pages, >> * section_activate() and pfn_valid() . >> */ >> if (!section_is_early) { >> - memmap_pages_add(-1L * (DIV_ROUND_UP(nr_pages * = sizeof(struct page), PAGE_SIZE))); >=20 > That's nice to be factored out in any case. >=20 > --=20 > Cheers, >=20 > David