From: Alistair Popple <apopple@nvidia•com>
To: linux-arm-kernel@lists•infradead.org
Cc: linux-kernel@vger•kernel.org, linux-mm@kvack•org,
catalin.marinas@arm•com, will@kernel•org, david@kernel•org,
akpm@linux-foundation•org, Alistair Popple <apopple@nvidia•com>
Subject: [PATCH] arm64: mm: call pagetable dtor when freeing hot-removed page tables
Date: Thu, 21 May 2026 13:27:30 +1000 [thread overview]
Message-ID: <20260521032730.2104017-1-apopple@nvidia.com> (raw)
Since 5e8eb9aeeda3 ("arm64: mm: always call PTE/PMD ctor in
__create_pgd_mapping()") page-table allocation on ARM64 always
calls pagetable_{pte,pmd,pud,p4d}_ctor(). This sets the page_type
to PGTY_table, increments NR_PAGETABLE and possible allocates a PTL.
However the matching pagetable_dtor() calls were never added.
With DEBUG_VM enabled on kernel versions prior to v6.17 without
2dfcd1608f3a9 ("mm/page_alloc: let page freeing clear any set page
type") this leads to the following warning when freeing these pages due
to page->page_type sharing page->_mapcount:
BUG: Bad page state in process ... pfn:284fbb
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x284fbb
flags: 0x17fffc000000000(node=0|zone=2|lastcpupid=0x1ffff)
page_type: f2(table)
page dumped because: nonzero mapcount
Call trace:
bad_page+0x13c/0x160
__free_frozen_pages+0x6cc/0x860
___free_pages+0xf4/0x180
free_pages+0x54/0x80
free_hotplug_page_range.part.0+0x58/0x90
free_empty_tables+0x438/0x500
__remove_pgd_mapping.constprop.0+0x60/0xa8
arch_remove_memory+0x48/0x80
try_remove_memory+0x158/0x1d8
offline_and_remove_memory+0x138/0x180
It can also lead to leaking the ptl allocation if ALLOC_SPLIT_PTLOCKS
is defined and incorrect NR_PAGETABLE stats. Fix this by calling
pagetable_dtor() in free_hotplug_pgtable_page() prior to freeing the
page to undo the effects of calling pagetable_*_ctor().
Fixes: 5e8eb9aeeda3 ("arm64: mm: always call PTE/PMD ctor in __create_pgd_mapping()")
Signed-off-by: Alistair Popple <apopple@nvidia•com>
---
arch/arm64/mm/mmu.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 8e1d80a7033e..0c24fe650e95 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -1422,6 +1422,7 @@ static void free_hotplug_page_range(struct page *page, size_t size,
static void free_hotplug_pgtable_page(struct page *page)
{
+ pagetable_dtor(page_ptdesc(page));
free_hotplug_page_range(page, PAGE_SIZE, NULL);
}
--
2.54.0
next reply other threads:[~2026-05-21 3:27 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-21 3:27 Alistair Popple [this message]
2026-05-21 22:31 ` [PATCH] arm64: mm: call pagetable dtor when freeing hot-removed page tables Andrew Morton
2026-05-21 23:50 ` Alistair Popple
2026-05-22 7:15 ` Catalin Marinas
2026-05-22 7:32 ` Catalin Marinas
2026-05-22 9:36 ` Vishal Moola
2026-05-26 11:54 ` Kevin Brodsky
2026-05-26 12:31 ` David Hildenbrand (Arm)
2026-05-27 7:34 ` Kevin Brodsky
2026-05-27 9:22 ` Vishal Moola
2026-05-31 19:29 ` David Hildenbrand (Arm)
2026-05-26 15:07 ` Will Deacon
2026-05-27 7:35 ` Kevin Brodsky
2026-05-27 9:30 ` Vishal Moola
2026-05-28 8:05 ` Kevin Brodsky
2026-05-29 10:16 ` Vishal Moola
2026-06-02 4:22 ` Andrew Morton
2026-06-02 13:12 ` Will Deacon
2026-06-02 17:06 ` Andrew Morton
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