On Wed, Jun 11, 2025 at 11:59:00PM -0700, Nicolin Chen wrote: > We can see the 64MB was rounded up to 512MB by ksys_mmap_pgoff() > when being passed in to hugetlb_file_setup() at: > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/mm/mmap.c?h=v6.16-rc1#n594 > " len = ALIGN(len, huge_page_size(hs)); " > > By looking at the comments here..: > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/hugetlbfs/inode.c#n1521 > " > /* > * Note that size should be aligned to proper hugepage size in caller side, > * otherwise hugetlb_reserve_pages reserves one less hugepages than intended. > */ > struct file *hugetlb_file_setup(const char *name, size_t size, > " > > ..I guess this function was supposed to fail the not-a-multiple > case as you remarked? But it certainly can't do that, when that > size passed in is already hugepage-aligned.. > > It feels like a kernel bug as you suspect :-/
Certainly is > And I just found one more weird thing... > > In iommufd.c selftest code, we have: > "static __attribute__((constructor)) void setup_sizes(void)" > where it does another pair of posix_memalign/mmap, although this > one doesn't flag MAP_HUGETLB and shouldn't impact what is coming > to the next... This could all just be more weirdness from the above, it doesn't really make alot of sense. I think change things so the MAP_HUGETLB test all skip if HUGEPAGE_SIZE < buffer_size and move on.. Can't run those tests on ARM64 64k which is unfortunate.. I thought there were patches to give that config a 2M huge page size option based on the new contiguous page support though? Maybe it was only THPS.. Jason
