On 9/15/21 3:03 PM, Mike Kravetz wrote:
> On 9/15/21 6:11 AM, zhenguo yao wrote:
>> Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> 于2021年9月15日周三 上午11:50写道：
>>>
>>> On Thu, 9 Sep 2021 22:16:55 +0800 yaozhenguo <yaozhenguo1@xxxxxxxxx> wrote:
>>>
>>>> +static void __init hugetlb_hstate_alloc_pages_onenode(struct hstate *h, int nid)
>>>> +{
>>>> + unsigned long i;
>>>> + char buf[32];
>>>> +
>>>> + for (i = 0; i < h->max_huge_pages_node[nid]; ++i) {
>>>> + if (hstate_is_gigantic(h)) {
>>>> + struct huge_bootmem_page *m;
>>>> + void *addr;
>>>> +
>>>> + addr = memblock_alloc_try_nid_raw(
>>>> + huge_page_size(h), huge_page_size(h),
>>>> + 0, MEMBLOCK_ALLOC_ACCESSIBLE, nid);
>>>> + if (!addr)
>>>> + break;
>>>> + m = addr;
>>>> + BUG_ON(!IS_ALIGNED(virt_to_phys(m), huge_page_size(h)));
>>>
>>> We try very hard to avoid adding BUG calls. Is there any way in which
>>> this code can emit a WARNing then permit the kernel to keep operating?
>>>
>> Maybe we can rewrite it as below:
>> if (WARN(!IS_ALIGNED(virt_to_phys(m),
>> huge_page_size(h)),
>> "HugeTLB: page addr:%p is not aligned\n", m))
>> break;
>> @Mike, Do you think it's OK?
>
> Sorry, I have not yet reviewed the latest version of this patch.
> Quick thought on this question.
>
> The required alignment passed to memblock_alloc_try_nid_raw() is
> huge_page_size(h). Therefore, we know the virtual address m is
> huge_page_size(h) aligned. The BUG is just checking to make sure
> the physical address associated with the virtual address is aligned
> the same. I really do not see how this could not be the case.
> In fact, the memblock allocator finds a physical address with the
> required alignment and then returns phys_to_virt(alloc).
> Someone please correct me if I am wrong. Otherwise, we can drop
> the BUG.
> Adding Mike Rapport on Cc:
>
> This allocation code and the associated BUG was copied from
> __alloc_bootmem_huge_page(). The BUG was added 12 years ago before
> the memblock allocator existed and we were using the bootmem allocator.
> If there is no need for a BUG in hugetlb_hstate_alloc_pages_onenode,
> there is no need for one in __alloc_bootmem_huge_page.
One additional thought.
Architectures can provide their own version of alloc_bootmem_huge_page.
powerpc is the only architecture doing so today. If an architecture
does provide their own version of alloc_bootmem_huge_page, I do not
think we should/can use hugetlb_hstate_alloc_pages_onenode to allocate
node specific gigantic huge pages.
I think we need to disable this feature for such architectures,
-OR-
provide some method to do architecture specific node allocations of
gigantic pages.
--
Mike Kravetz
