On 10/9/25 17:12, David Hildenbrand wrote:
> On 09.10.25 06:21, Balbir Singh wrote:
>> On 8/22/25 06:06, David Hildenbrand wrote:
>>> Let's reject them early, which in turn makes folio_alloc_gigantic() reject
>>> them properly.
>>>
>>> To avoid converting from order to nr_pages, let's just add MAX_FOLIO_ORDER
>>> and calculate MAX_FOLIO_NR_PAGES based on that.
>>>
>>> Signed-off-by: David Hildenbrand <da...@redhat.com>
>>> ---
>>> include/linux/mm.h | 6 ++++--
>>> mm/page_alloc.c | 5 ++++-
>>> 2 files changed, 8 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>>> index 00c8a54127d37..77737cbf2216a 100644
>>> --- a/include/linux/mm.h
>>> +++ b/include/linux/mm.h
>>> @@ -2055,11 +2055,13 @@ static inline long folio_nr_pages(const struct
>>> folio *folio)
>>> /* Only hugetlbfs can allocate folios larger than MAX_ORDER */
>>> #ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
>>> -#define MAX_FOLIO_NR_PAGES (1UL << PUD_ORDER)
>>> +#define MAX_FOLIO_ORDER PUD_ORDER
>>
>> Do we need to check for CONTIG_ALLOC as well with
>> CONFIG_ARCH_HAS_GIGANTIC_PAGE?
>>
>
> I don't think so, can you elaborate?
>
The only way to allocate a gigantic page is to use CMA, IIRC, which is covered
by CONTIG_ALLOC
>>> #else
>>> -#define MAX_FOLIO_NR_PAGES MAX_ORDER_NR_PAGES
>>> +#define MAX_FOLIO_ORDER MAX_PAGE_ORDER
>>> #endif
>>> +#define MAX_FOLIO_NR_PAGES (1UL << MAX_FOLIO_ORDER)
>>> +
>>> /*
>>> * compound_nr() returns the number of pages in this potentially compound
>>> * page. compound_nr() can be called on a tail page, and is defined to
>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>>> index ca9e6b9633f79..1e6ae4c395b30 100644
>>> --- a/mm/page_alloc.c
>>> +++ b/mm/page_alloc.c
>>> @@ -6833,6 +6833,7 @@ static int __alloc_contig_verify_gfp_mask(gfp_t
>>> gfp_mask, gfp_t *gfp_cc_mask)
>>> int alloc_contig_range_noprof(unsigned long start, unsigned long end,
>>> acr_flags_t alloc_flags, gfp_t gfp_mask)
>>> {
>>> + const unsigned int order = ilog2(end - start);
>>
>> Do we need a VM_WARN_ON(end < start)?
>
> I don't think so.
>
end - start being < 0, completely breaks ilog2. But we would error out because
ilog2 > MAX_FOLIO_ORDER, so we should fine
>>
>>> unsigned long outer_start, outer_end;
>>> int ret = 0;
>>> @@ -6850,6 +6851,9 @@ int alloc_contig_range_noprof(unsigned long start,
>>> unsigned long end,
>>> PB_ISOLATE_MODE_CMA_ALLOC :
>>> PB_ISOLATE_MODE_OTHER;
>>> + if (WARN_ON_ONCE((gfp_mask & __GFP_COMP) && order > MAX_FOLIO_ORDER))
>>> + return -EINVAL;
>>> +
>>> gfp_mask = current_gfp_context(gfp_mask);
>>> if (__alloc_contig_verify_gfp_mask(gfp_mask, (gfp_t *)&cc.gfp_mask))
>>> return -EINVAL;
>>> @@ -6947,7 +6951,6 @@ int alloc_contig_range_noprof(unsigned long start,
>>> unsigned long end,
>>> free_contig_range(end, outer_end - end);
>>> } else if (start == outer_start && end == outer_end &&
>>> is_power_of_2(end - start)) {
>>> struct page *head = pfn_to_page(start);
>>> - int order = ilog2(end - start);
>>> check_new_pages(head, order);
>>> prep_new_page(head, order, gfp_mask, 0);
>>
>> Acked-by: Balbir Singh <balb...@nvidia.com>
>
> Thanks for the review, but note that this is already upstream.
>
Sorry, this showed up in my updated mm thread and I ended up reviewing it,
please ignore if it's upstream
Balbir
