From: "Kiryl Shutsemau (Meta)" <[email protected]> An mTHP collapse test needs to know that a range is backed by folios of the target order, and that they sit where a collapse would put them. Nothing answers that today: is_backed_by_folio() classifies the folio behind a single page, and check_huge_anon() reads smaps AnonHugePages, which only accounts PMD mappings.
Add is_range_backed_by_order(). It requires every folio-sized, folio- aligned part of the range to map one folio of that order, head to tail, with the head at the start of the part. A part backed by two smaller folios fails, and so does a folio mapped off its natural alignment. The mTHP cases need both to tell a collapsed range from the one beside it. Assisted-by: LLM Reviewed-by: Mike Rapoport (Microsoft) <[email protected]> Tested-by: Muhammad Usama Anjum <[email protected]> Signed-off-by: Kiryl Shutsemau (Meta) <[email protected]> --- tools/testing/selftests/mm/vm_util.c | 47 ++++++++++++++++++++++++++++ tools/testing/selftests/mm/vm_util.h | 2 ++ 2 files changed, 49 insertions(+) diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c index 3ea42a7a2a3e..4947612e8b3d 100644 --- a/tools/testing/selftests/mm/vm_util.c +++ b/tools/testing/selftests/mm/vm_util.c @@ -552,6 +552,53 @@ bool is_backed_by_folio(char *vaddr, int order, int pagemap_fd, return false; } +/** + * is_range_backed_by_order() - check that a range is backed by @order folios + * @start: start of the range, a multiple of the folio size + * @len: length of the range in bytes, a multiple of the folio size + * @order: the folio order to check for + * @pagemap_fd: open /proc/<pid>/pagemap of the range's owner + * @kpageflags_fd: open /proc/kpageflags + * + * Every folio-sized, folio-aligned part of the range must map one folio of + * @order, head to tail, with the head at the start of the part. A part + * backed by several smaller folios fails, and so does a folio mapped off + * its natural alignment. + * + * Returns: true if the whole range is backed that way, false otherwise. + */ +bool is_range_backed_by_order(char *start, size_t len, int order, + int pagemap_fd, int kpageflags_fd) +{ + const unsigned long nr_pages = 1UL << order; + const size_t folio_size = nr_pages * psize(); + char *vaddr; + + if ((uintptr_t)start % folio_size || len % folio_size) + return false; + + for (vaddr = start; vaddr < start + len; vaddr += folio_size) { + const unsigned long pfn = pagemap_get_pfn(pagemap_fd, vaddr); + unsigned long i; + + /* Not present, or a tail page */ + if (pfn == -1UL || pfn % nr_pages) + return false; + + for (i = 1; i < nr_pages; i++) { + char *page = vaddr + i * psize(); + + if (pagemap_get_pfn(pagemap_fd, page) != pfn + i) + return false; + } + + if (!is_backed_by_folio(vaddr, order, pagemap_fd, kpageflags_fd)) + return false; + } + + return true; +} + /* If `ioctls' non-NULL, the allowed ioctls will be returned into the var */ int uffd_register_with_ioctls(int uffd, void *addr, uint64_t len, bool miss, bool wp, bool minor, uint64_t *ioctls) diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests/mm/vm_util.h index 56a28ce7d029..e509fc4012a5 100644 --- a/tools/testing/selftests/mm/vm_util.h +++ b/tools/testing/selftests/mm/vm_util.h @@ -99,6 +99,8 @@ int gather_folio_orders(char *vaddr_start, size_t len, int pagemap_fd, int kpageflags_fd, int orders[], int nr_orders); bool is_backed_by_folio(char *vaddr, int order, int pagemap_fd, int kpageflags_fd); +bool is_range_backed_by_order(char *start, size_t len, int order, + int pagemap_fd, int kpageflags_fd); int uffd_register(int uffd, void *addr, uint64_t len, bool miss, bool wp, bool minor); -- 2.54.0
