Re: [LTP] [PATCH v2 2/4] syscalls/statx10: Add basic test for STATX_DIOALIGN on regular file

[Eric Biggers <ebiggers@kernel.org>]

On Mon, Apr 03, 2023 at 06:44:34PM +0800, Yang Xu wrote:
> +static void verify_statx(void)
> +{
> +	struct statx buf;
> +
> +	memset(&buf, 0, sizeof(buf));
> +	TST_EXP_PASS(statx(AT_FDCWD, TESTFILE, 0, STATX_DIOALIGN, &buf),
> +		"statx(AT_FDCWD, %s, 0, STATX_DIOALIGN, &buf)", TESTFILE);
> +
> +	if (!(buf.stx_mask & STATX_DIOALIGN)) {
> +		tst_res(TCONF, "STATX_DIOALIGN is not supported until linux 6.1");
> +		return;
> +	}
> +
> +	if (buf.stx_dio_mem_align != 0)
> +		tst_res(TPASS, "stx_dio_mem_align:%u", buf.stx_dio_mem_align);
> +	else
> +		tst_res(TFAIL, "don't get stx_dio_mem_align on supported dio fs");
> +
> +	if (buf.stx_dio_offset_align != 0)
> +		tst_res(TPASS, "stx_dio_offset_align:%u", buf.stx_dio_offset_align);
> +	else
> +		tst_res(TFAIL, "don't get stx_dio_offset_align on supported dio fs");
> +}
> +
> +static void setup(void)
> +{
> +	if (strcmp(tst_device->fs_type, "xfs") && strcmp(tst_device->fs_type, "ext4"))
> +		tst_brk(TCONF, "This test only supports ext4 and xfs");
> +
> +	SAFE_FILE_PRINTF(TESTFILE, "AAAA");
> +	fd = open(TESTFILE, O_RDWR | O_DIRECT);
> +	if (fd == -1 && errno == EINVAL)
> +		tst_brk(TCONF, "The regular file is not on a filesystem that support DIO");
> +}

On ext4, files that use certain filesystem features (data journalling,
encryption, and verity) fall back to buffered I/O.  This test will fail when
passed such a file, as it assumes that DIO doesn't fall back to buffered I/O.

How is it guaranteed that such a file is not passed to this test?

- Eric

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