Re: [PATCH v2 4/4] selftests/mm: Fix test result reporting in gup_longterm

[Lorenzo Stoakes <lorenzo.stoakes@oracle.com>]

This seems to be causing tests to fail rather than be skipped if hugetlb
isn't configured. I bisected the problem to this patch so it's definitely
changed how things are handled (though of course it might just be
_revealing_ some previously existing bug in this test...).

Using a couple of tests as an example:

Before this patch:

# [RUN] R/O longterm GUP-fast pin in MAP_PRIVATE file mapping ... with memfd hugetlb (2048 kB)
ok 39 # SKIP memfd_create() failed (Cannot allocate memory)
# [RUN] R/O longterm GUP-fast pin in MAP_PRIVATE file mapping ... with memfd hugetlb (1048576 kB)
ok 40 # SKIP memfd_create() failed (Cannot allocate memory)

After:

# [RUN] R/O longterm GUP-fast pin in MAP_PRIVATE file mapping ... with memfd hugetlb (2048 kB)
# memfd_create() failed (Cannot allocate memory)
not ok 39 R/O longterm GUP-fast pin in MAP_PRIVATE file mapping ... with memfd hugetlb (2048 kB)
# [RUN] R/O longterm GUP-fast pin in MAP_PRIVATE file mapping ... with memfd hugetlb (1048576 kB)
# memfd_create() failed (Cannot allocate memory)
not ok 40 R/O longterm GUP-fast pin in MAP_PRIVATE file mapping ... with memfd hugetlb (1048576 kB)

See below, I think I've found where it happens...

On Tue, May 27, 2025 at 05:04:48PM +0100, Mark Brown wrote:
> The kselftest framework uses the string logged when a test result is
> reported as the unique identifier for a test, using it to track test
> results between runs. The gup_longterm test fails to follow this
> pattern, it runs a single test function repeatedly with various
> parameters but each result report is a string logging an error message
> which is fixed between runs.
>
> Since the code already logs each test uniquely before it starts refactor
> to also print this to a buffer, then use that name as the test result.
> This isn't especially pretty but is relatively straightforward and is a
> great help to tooling.
>
> Signed-off-by: Mark Brown <broonie@kernel.org>
> ---
>  tools/testing/selftests/mm/gup_longterm.c | 150 +++++++++++++++++++-----------
>  1 file changed, 94 insertions(+), 56 deletions(-)
>
> diff --git a/tools/testing/selftests/mm/gup_longterm.c b/tools/testing/selftests/mm/gup_longterm.c
> index e60e62809186..f84ea97c2543 100644
> --- a/tools/testing/selftests/mm/gup_longterm.c
> +++ b/tools/testing/selftests/mm/gup_longterm.c
> @@ -93,33 +93,48 @@ static void do_test(int fd, size_t size, enum test_type type, bool shared)
>  	__fsword_t fs_type = get_fs_type(fd);
>  	bool should_work;
>  	char *mem;
> +	int result = KSFT_PASS;
>  	int ret;
>
> +	if (fd < 0) {
> +		result = KSFT_FAIL;
> +		goto report;
> +	}
> +
>  	if (ftruncate(fd, size)) {
>  		if (errno == ENOENT) {
>  			skip_test_dodgy_fs("ftruncate()");
>  		} else {
> -			ksft_test_result_fail("ftruncate() failed (%s)\n", strerror(errno));
> +			ksft_print_msg("ftruncate() failed (%s)\n",
> +				       strerror(errno));
> +			result = KSFT_FAIL;
> +			goto report;
>  		}
>  		return;
>  	}
>
>  	if (fallocate(fd, 0, 0, size)) {
> -		if (size == pagesize)
> -			ksft_test_result_fail("fallocate() failed (%s)\n", strerror(errno));
> -		else
> -			ksft_test_result_skip("need more free huge pages\n");
> -		return;
> +		if (size == pagesize) {
> +			ksft_print_msg("fallocate() failed (%s)\n", strerror(errno));
> +			result = KSFT_FAIL;
> +		} else {
> +			ksft_print_msg("need more free huge pages\n");
> +			result = KSFT_SKIP;
> +		}
> +		goto report;
>  	}
>
>  	mem = mmap(NULL, size, PROT_READ | PROT_WRITE,
>  		   shared ? MAP_SHARED : MAP_PRIVATE, fd, 0);
>  	if (mem == MAP_FAILED) {
> -		if (size == pagesize || shared)
> -			ksft_test_result_fail("mmap() failed (%s)\n", strerror(errno));
> -		else
> -			ksft_test_result_skip("need more free huge pages\n");
> -		return;
> +		if (size == pagesize || shared) {
> +			ksft_print_msg("mmap() failed (%s)\n", strerror(errno));
> +			result = KSFT_FAIL;
> +		} else {
> +			ksft_print_msg("need more free huge pages\n");
> +			result = KSFT_SKIP;
> +		}
> +		goto report;
>  	}
>
>  	/* Fault in the page such that GUP-fast can pin it directly. */
> @@ -134,7 +149,8 @@ static void do_test(int fd, size_t size, enum test_type type, bool shared)
>  		 */
>  		ret = mprotect(mem, size, PROT_READ);
>  		if (ret) {
> -			ksft_test_result_fail("mprotect() failed (%s)\n", strerror(errno));
> +			ksft_print_msg("mprotect() failed (%s)\n", strerror(errno));
> +			result = KSFT_FAIL;
>  			goto munmap;
>  		}
>  		/* FALLTHROUGH */
> @@ -147,12 +163,14 @@ static void do_test(int fd, size_t size, enum test_type type, bool shared)
>  				type == TEST_TYPE_RW_FAST;
>
>  		if (gup_fd < 0) {
> -			ksft_test_result_skip("gup_test not available\n");
> +			ksft_print_msg("gup_test not available\n");
> +			result = KSFT_SKIP;
>  			break;
>  		}
>
>  		if (rw && shared && fs_is_unknown(fs_type)) {
> -			ksft_test_result_skip("Unknown filesystem\n");
> +			ksft_print_msg("Unknown filesystem\n");
> +			result = KSFT_SKIP;
>  			return;
>  		}
>  		/*
> @@ -169,14 +187,19 @@ static void do_test(int fd, size_t size, enum test_type type, bool shared)
>  		args.flags |= rw ? PIN_LONGTERM_TEST_FLAG_USE_WRITE : 0;
>  		ret = ioctl(gup_fd, PIN_LONGTERM_TEST_START, &args);
>  		if (ret && errno == EINVAL) {
> -			ksft_test_result_skip("PIN_LONGTERM_TEST_START failed (EINVAL)n");
> +			ksft_print_msg("PIN_LONGTERM_TEST_START failed (EINVAL)n");
> +			result = KSFT_SKIP;
>  			break;
>  		} else if (ret && errno == EFAULT) {
> -			ksft_test_result(!should_work, "Should have failed\n");
> +			if (should_work)
> +				result = KSFT_FAIL;
> +			else
> +				result = KSFT_PASS;
>  			break;
>  		} else if (ret) {
> -			ksft_test_result_fail("PIN_LONGTERM_TEST_START failed (%s)\n",
> -					      strerror(errno));
> +			ksft_print_msg("PIN_LONGTERM_TEST_START failed (%s)\n",
> +				       strerror(errno));
> +			result = KSFT_FAIL;
>  			break;
>  		}
>
> @@ -189,7 +212,10 @@ static void do_test(int fd, size_t size, enum test_type type, bool shared)
>  		 * some previously unsupported filesystems, we might want to
>  		 * perform some additional tests for possible data corruptions.
>  		 */
> -		ksft_test_result(should_work, "Should have worked\n");
> +		if (should_work)
> +			result = KSFT_PASS;
> +		else
> +			result = KSFT_FAIL;
>  		break;
>  	}
>  #ifdef LOCAL_CONFIG_HAVE_LIBURING
> @@ -199,8 +225,9 @@ static void do_test(int fd, size_t size, enum test_type type, bool shared)
>
>  		/* io_uring always pins pages writable. */
>  		if (shared && fs_is_unknown(fs_type)) {
> -			ksft_test_result_skip("Unknown filesystem\n");
> -			return;
> +			ksft_print_msg("Unknown filesystem\n");
> +			result = KSFT_SKIP;
> +			goto report;
>  		}
>  		should_work = !shared ||
>  			      fs_supports_writable_longterm_pinning(fs_type);
> @@ -208,8 +235,9 @@ static void do_test(int fd, size_t size, enum test_type type, bool shared)
>  		/* Skip on errors, as we might just lack kernel support. */
>  		ret = io_uring_queue_init(1, &ring, 0);
>  		if (ret < 0) {
> -			ksft_test_result_skip("io_uring_queue_init() failed (%s)\n",
> -					      strerror(-ret));
> +			ksft_print_msg("io_uring_queue_init() failed (%s)\n",
> +				       strerror(-ret));
> +			result = KSFT_SKIP;
>  			break;
>  		}
>  		/*
> @@ -222,17 +250,28 @@ static void do_test(int fd, size_t size, enum test_type type, bool shared)
>  		/* Only new kernels return EFAULT. */
>  		if (ret && (errno == ENOSPC || errno == EOPNOTSUPP ||
>  			    errno == EFAULT)) {
> -			ksft_test_result(!should_work, "Should have failed (%s)\n",
> -					 strerror(errno));
> +			if (should_work) {
> +				ksft_print_msg("Should have failed (%s)\n",
> +					       strerror(errno));
> +				result = KSFT_FAIL;
> +			} else {
> +				result = KSFT_PASS;
> +			}
>  		} else if (ret) {
>  			/*
>  			 * We might just lack support or have insufficient
>  			 * MEMLOCK limits.
>  			 */
> -			ksft_test_result_skip("io_uring_register_buffers() failed (%s)\n",
> -					      strerror(-ret));
> +			ksft_print_msg("io_uring_register_buffers() failed (%s)\n",
> +				       strerror(-ret));
> +			result = KSFT_SKIP;
>  		} else {
> -			ksft_test_result(should_work, "Should have worked\n");
> +			if (should_work) {
> +				result = KSFT_PASS;
> +			} else {
> +				ksft_print_msg("Should have worked\n");
> +				result = KSFT_FAIL;
> +			}
>  			io_uring_unregister_buffers(&ring);
>  		}
>
> @@ -246,6 +285,8 @@ static void do_test(int fd, size_t size, enum test_type type, bool shared)
>
>  munmap:
>  	munmap(mem, size);
> +report:
> +	log_test_result(result);
>  }
>
>  typedef void (*test_fn)(int fd, size_t size);
> @@ -254,13 +295,11 @@ static void run_with_memfd(test_fn fn, const char *desc)
>  {
>  	int fd;
>
> -	ksft_print_msg("[RUN] %s ... with memfd\n", desc);
> +	log_test_start("%s ... with memfd", desc);
>
>  	fd = memfd_create("test", 0);
> -	if (fd < 0) {
> -		ksft_test_result_fail("memfd_create() failed (%s)\n", strerror(errno));
> -		return;
> -	}
> +	if (fd < 0)
> +		ksft_print_msg("memfd_create() failed (%s)\n", strerror(errno));
>
>  	fn(fd, pagesize);
>  	close(fd);
> @@ -271,23 +310,23 @@ static void run_with_tmpfile(test_fn fn, const char *desc)
>  	FILE *file;
>  	int fd;
>
> -	ksft_print_msg("[RUN] %s ... with tmpfile\n", desc);
> +	log_test_start("%s ... with tmpfile", desc);
>
>  	file = tmpfile();
>  	if (!file) {
> -		ksft_test_result_fail("tmpfile() failed (%s)\n", strerror(errno));
> -		return;
> -	}
> -
> -	fd = fileno(file);
> -	if (fd < 0) {
> -		ksft_test_result_fail("fileno() failed (%s)\n", strerror(errno));
> -		goto close;
> +		ksft_print_msg("tmpfile() failed (%s)\n", strerror(errno));
> +		fd = -1;
> +	} else {
> +		fd = fileno(file);
> +		if (fd < 0) {
> +			ksft_print_msg("fileno() failed (%s)\n", strerror(errno));
> +		}
>  	}
>
>  	fn(fd, pagesize);
> -close:
> -	fclose(file);
> +
> +	if (file)
> +		fclose(file);
>  }
>
>  static void run_with_local_tmpfile(test_fn fn, const char *desc)
> @@ -295,22 +334,22 @@ static void run_with_local_tmpfile(test_fn fn, const char *desc)
>  	char filename[] = __FILE__"_tmpfile_XXXXXX";
>  	int fd;
>
> -	ksft_print_msg("[RUN] %s ... with local tmpfile\n", desc);
> +	log_test_start("%s ... with local tmpfile", desc);
>
>  	fd = mkstemp(filename);
> -	if (fd < 0) {
> -		ksft_test_result_fail("mkstemp() failed (%s)\n", strerror(errno));
> -		return;
> -	}
> +	if (fd < 0)
> +		ksft_print_msg("mkstemp() failed (%s)\n", strerror(errno));
>
>  	if (unlink(filename)) {
> -		ksft_test_result_fail("unlink() failed (%s)\n", strerror(errno));
> -		goto close;
> +		ksft_print_msg("unlink() failed (%s)\n", strerror(errno));
> +		close(fd);
> +		fd = -1;
>  	}
>
>  	fn(fd, pagesize);
> -close:
> -	close(fd);
> +
> +	if (fd >= 0)
> +		close(fd);
>  }
>
>  static void run_with_memfd_hugetlb(test_fn fn, const char *desc,
> @@ -319,15 +358,14 @@ static void run_with_memfd_hugetlb(test_fn fn, const char *desc,
>  	int flags = MFD_HUGETLB;
>  	int fd;
>
> -	ksft_print_msg("[RUN] %s ... with memfd hugetlb (%zu kB)\n", desc,
> +	log_test_start("%s ... with memfd hugetlb (%zu kB)", desc,
>  		       hugetlbsize / 1024);
>
>  	flags |= __builtin_ctzll(hugetlbsize) << MFD_HUGE_SHIFT;
>
>  	fd = memfd_create("test", flags);
>  	if (fd < 0) {
> -		ksft_test_result_skip("memfd_create() failed (%s)\n", strerror(errno));
> -		return;
> +		ksft_print_msg("memfd_create() failed (%s)\n", strerror(errno));

I think it's this change that does it (probably).

I wonder if it's worth checking for errno == ENOMEM and skipping in this
case? Or is that too general?

>  	}
>
>  	fn(fd, hugetlbsize);
>
> --
> 2.39.5
>