On 09.10.25 12:25, Balbir Singh wrote:
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 david@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
As we are discussing as part of v2 right now, there is the way to just obtain them from memblock during boot.
#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
Right, and if we have code that buggy that does it, it probably shouldn't be our responsibility to sanity check that :)
It would have been completely buggy before this patch.
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 balbirs@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
I'm happy for any review (better in reply to v2), because any bug caught early is good!