Re: fsconfig04: Check FSCONFIG_SET_PATH

Hi Wei,

On Wed, 10 Jun 2026 05:21:25 +0000, Wei Gao wrote:
> fsconfig04: Check FSCONFIG_SET_PATH

> +	TEST(fsconfig(fd, FSCONFIG_SET_STRING, "source", dev0, 0));
> +	if (TST_RET == -1) {
> +		tst_res(TFAIL | TTERRNO, "fsconfig(FSCONFIG_SET_STRING) failed");
> +		SAFE_CLOSE(fd);
> +		return;
> +	}

FSCONFIG_SET_STRING is not the subject of this test -- it is
infrastructure needed before the FSCONFIG_SET_PATH call under test.
If it fails, the test cannot proceed, so it should be reported as
TBROK, not TFAIL.

Using tst_brk(TBROK | TTERRNO, ...) would also simplify this block
because cleanup() already closes fd, making the explicit SAFE_CLOSE
unnecessary:

	TEST(fsconfig(fd, FSCONFIG_SET_STRING, "source", dev0, 0));
	if (TST_RET == -1)
		tst_brk(TBROK | TTERRNO, "fsconfig(FSCONFIG_SET_STRING) failed");

> +	unsigned int major, minor, device_num;
> +	unsigned int found = 0;
> +
> +	SAFE_SSCANF(dev2, "/dev/%s", loop_name);
> +
> +	snprintf(path, sizeof(path), "/sys/block/%s/dev", loop_name);
> +	SAFE_FILE_SCANF(path, "%u:%u", &major, &minor);
> +	device_num = (major << 8) | minor;
> +	snprintf(device_str, sizeof(device_str), "0x%04x", device_num);

The encoding (major << 8) | minor only matches the kernel's
new_encode_dev() when minor < 256. For minor >= 256 the kernel
stores (minor & 0xff) | (major << 8) | ((minor & ~0xff) << 12),
which is what tune2fs prints.

On a system with many loop devices in use the test could get a
loop device with minor >= 256, causing the computed string to
differ from tune2fs output and producing a false TFAIL.

Consider something like:

	device_num = (minor & 0xff) | (major << 8)
		| ((minor & ~0xff) << 12);

Verdict: Needs revision

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