On Fri, Mar 27, 2026 at 11:12:43AM +0800, Li Wang wrote:
> hugetlb_dio test uses sub-page offsets (pagesize / 2) to verify that
> hugepages used as DIO user buffers are correctly unpinned at completion.
>
> However, on filesystems with a logical block size larger than half the
> page size (e.g., 4K-sector block devices), these unaligned DIO writes
> are rejected with -EINVAL, causing the test to fail unexpectedly.
>
> Add check_dio_alignment() which queries the filesystem's DIO alignment
> requirement via statx(STATX_DIOALIGN) and skips the test early if the
> sub-page offset used by the test is not compatible with the alignment
> constraint.
>
> === Reproduce Steps ===
>
> # dd if=/dev/zero of=/tmp/test.img bs=1M count=512
> # losetup --sector-size 4096 /dev/loop0 /tmp/test.img
> # mkfs.xfs /dev/loop0
> # mkdir -p /mnt/dio_test
> # mount /dev/loop0 /mnt/dio_test
>
> // Modify test to open /mnt/dio_test and rebuild it:
> - fd = open("/tmp", O_TMPFILE | O_RDWR | O_DIRECT, 0664);
> + fd = open("/mnt/dio_test", O_TMPFILE | O_RDWR | O_DIRECT, 0664);
>
> # getconf PAGESIZE
> 4096
>
> # echo 100 >/proc/sys/vm/nr_hugepages
>
> # ./hugetlb_dio
> TAP version 13
> 1..4
> # No. Free pages before allocation : 100
> # No. Free pages after munmap : 100
> ok 1 free huge pages from 0-12288
> Bail out! Error writing to file
> : Invalid argument (22)
> # Planned tests != run tests (4 != 1)
> # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
>
> Signed-off-by: Li Wang <[email protected]>
> ---
> tools/testing/selftests/mm/hugetlb_dio.c | 37 +++++++++++++++++-------
> 1 file changed, 27 insertions(+), 10 deletions(-)
>
> diff --git a/tools/testing/selftests/mm/hugetlb_dio.c
> b/tools/testing/selftests/mm/hugetlb_dio.c
> index 9ac62eb4c97d..afcca50d190e 100644
> --- a/tools/testing/selftests/mm/hugetlb_dio.c
> +++ b/tools/testing/selftests/mm/hugetlb_dio.c
> @@ -20,6 +20,31 @@
> #include "vm_util.h"
> #include "kselftest.h"
>
> +#ifndef STATX_DIOALIGN
> +#define STATX_DIOALIGN 0x00002000U
> +#endif
> +
> +void check_dio_alignment(size_t pagesize)
> +{
> + int fd;
> + struct statx stx;
> + unsigned int dio_align = 1;
> +
> + fd = open("/tmp", O_TMPFILE | O_RDWR, 0664);
> + if (fd < 0)
> + ksft_exit_skip("Unable to allocate file: %s\n",
> strerror(errno));
> +
> + if (statx(fd, "", AT_EMPTY_PATH, STATX_DIOALIGN, &stx) == 0 &&
> + (stx.stx_mask & STATX_DIOALIGN))
> + dio_align = stx.stx_dio_offset_align;
> +
> + close(fd);
> +
> + if ((pagesize / 2) % dio_align != 0)
> + ksft_exit_skip("DIO alignment (%u) incompatible with sub-page
> offset %lu\n",
> + dio_align, pagesize / 2);
This also needlessly skips the test with aligned offsets.
I'd suggest detecting dio_align here, passing it to run_dio_using_hugetlb()
and moving the check that skips a test there.
> +}
> +
> void run_dio_using_hugetlb(unsigned int start_off, unsigned int end_off)
> {
> int fd;
--
Sincerely yours,
Mike.
