From: Sayali Patil Date: Thu, 21 May 2026 06:47:48 +0000 (+0530) Subject: selftest/mm: register existing mapping with userfaultfd in hugetlb-mremap X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1df31d5ef58dc6bdf0f2a8b809152d835c60b28e;p=thirdparty%2Flinux.git selftest/mm: register existing mapping with userfaultfd in hugetlb-mremap Previously, register_region_with_uffd() created a new anonymous mapping and overwrote the address supplied by the caller before registering the range with userfaultfd. As a result, userfaultfd was applied to an unrelated anonymous mapping instead of the hugetlb region used by the test. Remove the extra mmap() and register the caller-provided address range directly using UFFDIO_REGISTER_MODE_MISSING, so that faults are generated for the hugetlb mapping used by the test. This ensures userfaultfd operates on the actual hugetlb test region and validates the expected fault handling. Before patch: running ./hugetlb-mremap ------------------------- TAP version 13 1..1 Map haddr: Returned address is 0x7eaa40000000 Map daddr: Returned address is 0x7daa40000000 Map vaddr: Returned address is 0x7faa40000000 Address returned by mmap() = 0x7fff9d000000 Mremap: Returned address is 0x7faa40000000 First hex is 0 First hex is 3020100 ok 1 Read same data Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0 [PASS] ok 1 hugetlb-mremap After patch: running ./hugetb-mremap ------------------------- TAP version 13 1..1 Map haddr: Returned address is 0x7eaa40000000 Map daddr: Returned address is 0x7daa40000000 Map vaddr: Returned address is 0x7faa40000000 Registered memory at address 0x7eaa40000000 with userfaultfd Mremap: Returned address is 0x7faa40000000 First hex is 0 First hex is 3020100 ok 1 Read same data Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0 [PASS] ok 1 hugetlb-mremap Link: https://lore.kernel.org/13845da872ed174316173e8996dbb5f181994017.1779296493.git.sayalip@linux.ibm.com Fixes: 12b613206474 ("mm, hugepages: add hugetlb vma mremap() test") Signed-off-by: Sayali Patil Acked-by: David Hildenbrand (Arm) Tested-by: Venkat Rao Bagalkote Cc: Dev Jain Cc: Liam Howlett Cc: Miaohe Lin Cc: Michal Hocko Cc: Oscar Salvador Cc: "Ritesh Harjani (IBM)" Cc: Shuah Khan Cc: Zi Yan Signed-off-by: Andrew Morton --- diff --git a/tools/testing/selftests/mm/hugetlb-mremap.c b/tools/testing/selftests/mm/hugetlb-mremap.c index d239905790dd8..00b4c2cc95a66 100644 --- a/tools/testing/selftests/mm/hugetlb-mremap.c +++ b/tools/testing/selftests/mm/hugetlb-mremap.c @@ -86,25 +86,14 @@ static void register_region_with_uffd(char *addr, size_t len) if (ioctl(uffd, UFFDIO_API, &uffdio_api) == -1) ksft_exit_fail_msg("ioctl-UFFDIO_API: %s\n", strerror(errno)); - /* Create a private anonymous mapping. The memory will be - * demand-zero paged--that is, not yet allocated. When we - * actually touch the memory, it will be allocated via - * the userfaultfd. - */ - - addr = mmap(NULL, len, PROT_READ | PROT_WRITE, - MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); - if (addr == MAP_FAILED) - ksft_exit_fail_msg("mmap: %s\n", strerror(errno)); - - ksft_print_msg("Address returned by mmap() = %p\n", addr); - - /* Register the memory range of the mapping we just created for - * handling by the userfaultfd object. In mode, we request to track - * missing pages (i.e., pages that have not yet been faulted in). + /* Register the passed memory range for handling by the userfaultfd object. + * In mode, we request to track missing pages + * (i.e., pages that have not yet been faulted in). */ if (uffd_register(uffd, addr, len, true, false, false)) ksft_exit_fail_msg("ioctl-UFFDIO_REGISTER: %s\n", strerror(errno)); + + ksft_print_msg("Registered memory at address %p with userfaultfd\n", addr); } int main(int argc, char *argv[])