Re: [PATCH v3 04/11] arm64/mm: Add temporary arch_remove_memory() implementation

Michal Hocko
2019-07-01T12:48:09Z

On Mon 27-05-19 13:11:45, David Hildenbrand wrote:
> A proper arch_remove_memory() implementation is on its way, which also
> cleanly removes page tables in arch_add_memory() in case something goes
> wrong.
>
> As we want to use arch_remove_memory() in case something goes wrong
> during memory hotplug after arch_add_memory() finished, let's add
> a temporary hack that is sufficient enough until we get a proper
> implementation that cleans up page table entries.
>
> We will remove CONFIG_MEMORY_HOTREMOVE around this code in follow up
> patches.

I would drop this one as well (like s390 counterpart).

> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Chintan Pandya <cpandya@codeaurora.org>
> Cc: Mike Rapoport <rppt@linux.ibm.com>
> Cc: Jun Yao <yaojun8558363@gmail.com>
> Cc: Yu Zhao <yuzhao@google.com>
> Cc: Robin Murphy <robin.murphy@arm.com>
> Cc: Anshuman Khandual <anshuman.khandual@arm.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
> arch/arm64/mm/mmu.c | 19 +++++++++++++++++++
> 1 file changed, 19 insertions(+)
>
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index a1bfc4413982..e569a543c384 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -1084,4 +1084,23 @@ int arch_add_memory(int nid, u64 start, u64 size,
> return __add_pages(nid, start >> PAGE_SHIFT, size >> PAGE_SHIFT,
> restrictions);
> }
> +#ifdef CONFIG_MEMORY_HOTREMOVE
> +void arch_remove_memory(int nid, u64 start, u64 size,
> + struct vmem_altmap *altmap)
> +{
> + unsigned long start_pfn = start >> PAGE_SHIFT;
> + unsigned long nr_pages = size >> PAGE_SHIFT;
> + struct zone *zone;
> +
> + /*
> + * FIXME: Cleanup page tables (also in arch_add_memory() in case
> + * adding fails). Until then, this function should only be used
> + * during memory hotplug (adding memory), not for memory
> + * unplug. ARCH_ENABLE_MEMORY_HOTREMOVE must not be
> + * unlocked yet.
> + */
> + zone = page_zone(pfn_to_page(start_pfn));
> + __remove_pages(zone, start_pfn, nr_pages, altmap);
> +}
> +#endif
> #endif
> --
> 2.20.1

--
Michal Hocko
SUSE Labs