Re: [PATCH v2 2/4] riscv/mm: fix hotplug page-table destructor handling

[Björn Töpel]

Muchun Song <songmuchun@xxxxxxxxxxxxx> writes:

> RISC-V uses the same memory-hotplug teardown code for linear-map and
> vmemmap page tables. Late linear-map allocations run page-table
> constructors, while vmemmap and early allocations may not.
>
> free_pte_table() unconditionally calls pagetable_dtor(), corrupting
> NR_PAGETABLE accounting for constructor-free tables. free_pmd_table()
> avoids that for vmemmap using is_vmemmap, but mapping type is not a
> reliable proxy for constructor state. In particular, it becomes invalid
> once runtime vmemmap tables use the normal pgalloc helpers.
>
> Introduce free_pgtable_page() to select free_reserved_page() for reserved
> pages and pagetable_free() otherwise. The latter runs the destructor only
> when PageTable() is set, handling both constructor-backed and
> constructor-free tables.
>
> Fixes: c75a74f4ba19 ("riscv: mm: Add memory hotplugging support")
> Cc: stable@xxxxxxxxxxxxxxx
> Assisted-by: LLM
> Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>

Nice!

Reviewed-by: Björn Töpel <bjorn@xxxxxxxxxx>