Re: [PATCH v4] selftests/mm: skip hugetlb_dio tests when DIO alignment is incompatible

["David Hildenbrand (Arm)" <david@kernel.org>]

On 3/30/26 14:53, 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 get_dio_alignment() to query the filesystem's required DIO alignment
> via statx(STATX_DIOALIGN) and skip individual test cases whose file
> offset or write size is not a multiple of that alignment. Aligned cases
> continue to run so the core coverage is preserved.
> 
> While here, open the temporary file once in main() and share the fd
> across all test cases instead of reopening it in each invocation.
> 
> === 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 <liwang@redhat.com>
> Suggested-by: Mike Rapoport <rppt@kernel.org>
> Suggested-by: David Hildenbrand <david@kernel.org>
> ---


[...]

> +static void run_dio_using_hugetlb(int fd, unsigned int start_off,
> +				  unsigned int end_off)
>  {
> -	int fd;
>  	char *buffer =  NULL;
>  	char *orig_buffer = NULL;
>  	size_t h_pagesize = 0;
> @@ -39,10 +84,9 @@ void run_dio_using_hugetlb(unsigned int start_off, unsigned int end_off)
>  	if (!h_pagesize)
>  		ksft_exit_fail_msg("Unable to determine huge page size\n");
>  
> -	/* Open the file to DIO */
> -	fd = open("/tmp", O_TMPFILE | O_RDWR | O_DIRECT, 0664);
> -	if (fd < 0)
> -		ksft_exit_fail_perror("Error opening file\n");
> +	/* Reset file position since fd is shared across tests */
> +	if (lseek(fd, 0, SEEK_SET) < 0)
> +		ksft_exit_fail_perror("lseek failed\n");
>  
>  	/* Get the free huge pages before allocation */
>  	free_hpage_b = get_free_hugepages();
> @@ -71,7 +115,6 @@ void run_dio_using_hugetlb(unsigned int start_off, unsigned int end_off)
>  
>  	/* unmap the huge page */
>  	munmap(orig_buffer, h_pagesize);
> -	close(fd);
>  
>  	/* Get the free huge pages after unmap*/
>  	free_hpage_a = get_free_hugepages();
> @@ -87,39 +130,49 @@ void run_dio_using_hugetlb(unsigned int start_off, unsigned int end_off)
>  			 "free huge pages from %u-%u\n", start_off, end_off);
>  }
>  
> +static void run_test(int fd, unsigned int start_off,
> +		     unsigned int end_off, unsigned int align)

Nit: prefer to-tab alignment in MM land.

> +{
> +	if (!check_dio_alignment(start_off, end_off, align))
> +		return;

Is there a reason we just perform that at the beginning of
run_dio_using_hugetlb(), avoiding run_test() entirely?


In general, LGTM, thanks!

Feel free to add my

Acked-by: David Hildenbrand (Arm) <david@kernel.org>

-- 
Cheers,

David