On Fri, Aug 29, 2025 at 12:06:21PM +0200, David Hildenbrand wrote: > On 28.08.25 16:37, Lorenzo Stoakes wrote: > > On Thu, Aug 28, 2025 at 12:01:10AM +0200, 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. > > > > > > Reviewed-by: Zi Yan <z...@nvidia.com> > > > Acked-by: SeongJae Park <s...@kernel.org> > > > Signed-off-by: David Hildenbrand <da...@redhat.com> > > > > Some nits, but overall LGTM so: > > > > Reviewed-by: Lorenzo Stoakes <lorenzo.stoa...@oracle.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 > > > #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) > > > > BIT()? > > I don't think we want to use BIT whenever we convert from order -> folio -- > which is why we also don't do that in other code.
It seems a bit arbitrary, like we open-code this (at risk of making a mistake) in some places but not others. > > BIT() is nice in the context of flags and bitmaps, but not really in the > context of converting orders to pages. It's nice for setting a specific bit :) > > One could argue that maybe one would want a order_to_pages() helper (that > could use BIT() internally), but I am certainly not someone that would > suggest that at this point ... :) I mean maybe. Anyway as I said none of this is massively important, the open-coding here is correct, just seems silly. > > > > > > + > > > /* > > > * 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 baead29b3e67b..426bc404b80cc 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) Funny btw th > > > { > > > + const unsigned int order = ilog2(end - start); > > > 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; > > > > Possibly not worth it for a one off, but be nice to have this as a helper > > function, like: > > > > static bool is_valid_order(gfp_t gfp_mask, unsigned int order) > > { > > return !(gfp_mask & __GFP_COMP) || order <= MAX_FOLIO_ORDER; > > } > > > > Then makes this: > > > > if (WARN_ON_ONCE(!is_valid_order(gfp_mask, order))) > > return -EINVAL; > > > > Kinda self-documenting! > > I don't like it -- especially forwarding __GFP_COMP. > > is_valid_folio_order() to wrap the order check? Also not sure. OK, it's not a big deal. Can we have a comment explaining this though? As people might be confused as to why we check this here and not elsewhere. > > So I'll leave it as is I think. Right fine. > > Thanks for all the review! > > -- > Cheers > > David / dhildenb >