Re: [PATCH v5] selftests/mm: skip hugetlb_dio tests when DIO alignment is incompatible

[Andrew Morton]

On Wed,  1 Apr 2026 17:05:20 +0800 Li Wang <liwang@xxxxxxxxxx> 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

Thanks, I update mm.git to this version,

> Notes:
>     v5:
>     	- Perform that align checks at the beginning of run_dio_using_hugetlb()
>     	  but not addinital run_test().

Here's how v5 altered mm.git:

--- a/tools/testing/selftests/mm/hugetlb_dio.c~selftests-mm-skip-hugetlb_dio-tests-when-dio-alignment-is-incompatible-v5
+++ a/tools/testing/selftests/mm/hugetlb_dio.c
@@ -66,7 +66,7 @@ static bool check_dio_alignment(unsigned
 }
 
 static void run_dio_using_hugetlb(int fd, unsigned int start_off,
-				  unsigned int end_off)
+				unsigned int end_off, unsigned int align)
 {
 	char *buffer =  NULL;
 	char *orig_buffer = NULL;
@@ -77,6 +77,9 @@ static void run_dio_using_hugetlb(int fd
 	const int mmap_flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB;
 	const int mmap_prot  = PROT_READ | PROT_WRITE;
 
+	if (!check_dio_alignment(start_off, end_off, align))
+		return;
+
 	writesize = end_off - start_off;
 
 	/* Get the default huge page size */
@@ -130,15 +133,6 @@ static void run_dio_using_hugetlb(int fd
 			 "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)
-{
-	if (!check_dio_alignment(start_off, end_off, align))
-		return;
-
-	run_dio_using_hugetlb(fd, start_off, end_off);
-}
-
 int main(void)
 {
 	int fd, align;
@@ -161,16 +155,16 @@ int main(void)
 	ksft_set_plan(4);
 
 	/* start and end is aligned to pagesize */
-	run_test(fd, 0, (pagesize * 3), align);
+	run_dio_using_hugetlb(fd, 0, (pagesize * 3), align);
 
 	/* start is aligned but end is not aligned */
-	run_test(fd, 0, (pagesize * 3) - (pagesize / 2), align);
+	run_dio_using_hugetlb(fd, 0, (pagesize * 3) - (pagesize / 2), align);
 
 	/* start is unaligned and end is aligned */
-	run_test(fd, pagesize / 2, (pagesize * 3), align);
+	run_dio_using_hugetlb(fd, pagesize / 2, (pagesize * 3), align);
 
 	/* both start and end are unaligned */
-	run_test(fd, pagesize / 2, (pagesize * 3) + (pagesize / 2), align);
+	run_dio_using_hugetlb(fd, pagesize / 2, (pagesize * 3) + (pagesize / 2), align);
 
 	close(fd);
 
_