Re: [PATCH v2] selftests/mm: skip hugetlb_dio tests when DIO alignment is incompatible

[Andrew Morton <akpm@linux-foundation.org>]

On Fri, 27 Mar 2026 20:03:05 +0800 Li Wang <liwang@redhat.com> 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 get_dio_alignment() to query the filesystem's required DIO alignment
> via statx(STATX_DIOALIGN) and pass it to run_dio_using_hugetlb(). Skip
> individual test cases whose write length is not a multiple of the
> alignment, so that aligned cases are still tested.
> 
> === 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
> 
> ...
>
>     v2:
>     	- Pass dio_align as a parameter to run_dio_using_hugetlb()
>     	  instead of generally page_size/2 alignment check.
> 

Whee, AI review has decided that pre glibc-2.36 is a problem (last time
it was pre-2.37).

And it's forgotten the previous fs-doesnt-support-DIO issues.  Did you
alter that?

The get_dio_alignment-before-ksft_print_header thing seems legit.

https://sashiko.dev/#/patchset/20260327120305.58653-1-liwang@redhat.com