[PATCH v4 00/12] selftests/mm: Some cleanups from trying to run them

[PATCH v4 00/12] selftests/mm: Some cleanups from trying to run them

[Brendan Jackman]

I never had much luck running mm selftests so I spent a few hours
digging into why.

Looks like most of the reason is missing SKIP checks, so this series is
just adding a bunch of those that I found. I did not do anything like
all of them, just the ones I spotted in gup_longterm, gup_test, mmap,
userfaultfd and memfd_secret.

It's a bit unfortunate to have to skip those tests when ftruncate()
fails, but I don't have time to dig deep enough into it to actually make
them pass. I have observed the issue on 9pfs and heard rumours that NFS
has a similar problem.

I'm now able to run these test groups successfully:

- mmap
- gup_test
- compaction
- migration
- page_frag
- userfaultfd
- mlock

I've never gone past "Waiting for hugetlb memory to get depleted", in
the hugetlb tests. I don't know if they are stuck or if they would
eventually work if I was patient enough (testing on a 1G machine). I
have not investigated further.

I had some issues with mlock tests failing due to -ENOSRCH from
mlock2(), I can no longer reproduce that though, things work OK now.

Of the remaining tests there may be others that work fine, but there's
no convenient way to survey the whole output of run_vmtests.sh so I'm
just going test by test here.

In my spare moments I am slowly chipping away at a setup to run these
tests continuously in a reasonably hermetic QEMU environment via
virtme-ng:

https://github.com/bjackman/linux/blob/5fad4b9c592290f38e0f8bc73c9abb9c99d8787c/README.md

Hopefully that will eventually offer a way to provide a "canned"
environment where the tests are known to work, which can be fairly
easily reproduced by any developer.

Signed-off-by: Brendan Jackman <jackmanb@google.com>
---
Changes in v4:
- NOT ADDRESSED: still using errno==ENOENT as a hacky way to detect
  buggy filesystems:
  https://lore.kernel.org/all/CA+i-1C3srkh44tN8dMQ5aD-jhoksUkdEpa+mMfdDtDrPAUv7gQ@mail.gmail.com/
- Added some incomplete cleanups for the mlock tests.
- Fixed divide-by-zero error when running uffd-stress on <32cpu systems.
- Fixed misnamed nr_threads variable (now nr_parallel).
- Fixed reporting io_uring errors (retval instead of errno).
- Link to v3: https://lore.kernel.org/r/20250228-mm-selftests-v3-0-958e3b6f0203@google.com

Changes in v3:
- Added fix for userfaultfd tests.
- Dropped attempts to use sudo.
- Fixed garbage printf in uffd-stress.
  (Added EXTRA_CFLAGS=-Werror FORCE_TARGETS=1 to my scripts to prevent
   such errors happening again).
- Fixed missing newlines in ksft_test_result_skip() calls.
- Link to v2: https://lore.kernel.org/r/20250221-mm-selftests-v2-0-28c4d66383c5@google.com

Changes in v2 (Thanks to Dev for the reviews):
- Improve and cleanup some error messages
- Add some extra SKIPs
- Fix misnaming of nr_cpus variable in uffd tests
- Link to v1: https://lore.kernel.org/r/20250220-mm-selftests-v1-0-9bbf57d64463@google.com

---
Brendan Jackman (12):
      selftests/mm: Report errno when things fail in gup_longterm
      selftests/mm: Skip uffd-stress if userfaultfd not available
      selftests/mm: Skip uffd-wp-mremap if userfaultfd not available
      selftests/mm/uffd: Rename nr_cpus -> nr_parallel
      selftests/mm: Print some details when uffd-stress gets bad params
      selftests/mm: Don't fail uffd-stress if too many CPUs
      selftests/mm: Skip map_populate on weird filesystems
      selftests/mm: Skip gup_longterm tests on weird filesystems
      selftests/mm: Drop unnecessary sudo usage
      selftests/mm: Ensure uffd-wp-mremap gets pages of each size
      selftests/mm: Skip mlock tests if nobody user can't read it
      selftests/mm/mlock: Print error on failure

 tools/testing/selftests/mm/gup_longterm.c      | 45 +++++++++++++++++---------
 tools/testing/selftests/mm/map_populate.c      |  7 ++++
 tools/testing/selftests/mm/mlock-random-test.c |  4 +--
 tools/testing/selftests/mm/mlock2.h            |  8 ++++-
 tools/testing/selftests/mm/run_vmtests.sh      | 27 ++++++++++++++--
 tools/testing/selftests/mm/uffd-common.c       |  8 ++---
 tools/testing/selftests/mm/uffd-common.h       |  2 +-
 tools/testing/selftests/mm/uffd-stress.c       | 42 +++++++++++++++---------
 tools/testing/selftests/mm/uffd-unit-tests.c   |  2 +-
 tools/testing/selftests/mm/uffd-wp-mremap.c    |  5 ++-
 10 files changed, 105 insertions(+), 45 deletions(-)
---
base-commit: dcb38e6757f1b7944af9347ce6b54263d3666478
change-id: 20250220-mm-selftests-2d7d0542face

Best regards,
-- 
Brendan Jackman <jackmanb@google.com>

[PATCH v4 01/12] selftests/mm: Report errno when things fail in gup_longterm

[Brendan Jackman]

Just reporting failure doesn't tell you what went wrong. This can fail
in different ways so report errno to help the reader get started
debugging.

Reviewed-by: Dev Jain <dev.jain@arm.com>
Signed-off-by: Brendan Jackman <jackmanb@google.com>
---
 tools/testing/selftests/mm/gup_longterm.c | 37 ++++++++++++++++++-------------
 1 file changed, 21 insertions(+), 16 deletions(-)

diff --git a/tools/testing/selftests/mm/gup_longterm.c b/tools/testing/selftests/mm/gup_longterm.c
index 9423ad439a6140163bdef2974615bb86406a8c14..15335820656b1c143b440b8a1065a025378e22a2 100644
--- a/tools/testing/selftests/mm/gup_longterm.c
+++ b/tools/testing/selftests/mm/gup_longterm.c
@@ -96,13 +96,13 @@ static void do_test(int fd, size_t size, enum test_type type, bool shared)
 	int ret;
 
 	if (ftruncate(fd, size)) {
-		ksft_test_result_fail("ftruncate() failed\n");
+		ksft_test_result_fail("ftruncate() failed (%s)\n", strerror(errno));
 		return;
 	}
 
 	if (fallocate(fd, 0, 0, size)) {
 		if (size == pagesize)
-			ksft_test_result_fail("fallocate() failed\n");
+			ksft_test_result_fail("fallocate() failed (%s)\n", strerror(errno));
 		else
 			ksft_test_result_skip("need more free huge pages\n");
 		return;
@@ -112,7 +112,7 @@ static void do_test(int fd, size_t size, enum test_type type, bool shared)
 		   shared ? MAP_SHARED : MAP_PRIVATE, fd, 0);
 	if (mem == MAP_FAILED) {
 		if (size == pagesize || shared)
-			ksft_test_result_fail("mmap() failed\n");
+			ksft_test_result_fail("mmap() failed (%s)\n", strerror(errno));
 		else
 			ksft_test_result_skip("need more free huge pages\n");
 		return;
@@ -130,7 +130,7 @@ 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\n");
+			ksft_test_result_fail("mprotect() failed (%s)\n", strerror(errno));
 			goto munmap;
 		}
 		/* FALLTHROUGH */
@@ -165,18 +165,20 @@ 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\n");
+			ksft_test_result_skip("PIN_LONGTERM_TEST_START failed (EINVAL)n");
 			break;
 		} else if (ret && errno == EFAULT) {
 			ksft_test_result(!should_work, "Should have failed\n");
 			break;
 		} else if (ret) {
-			ksft_test_result_fail("PIN_LONGTERM_TEST_START failed\n");
+			ksft_test_result_fail("PIN_LONGTERM_TEST_START failed (%s)\n",
+					      strerror(errno));
 			break;
 		}
 
 		if (ioctl(gup_fd, PIN_LONGTERM_TEST_STOP))
-			ksft_print_msg("[INFO] PIN_LONGTERM_TEST_STOP failed\n");
+			ksft_print_msg("[INFO] PIN_LONGTERM_TEST_STOP failed (%s)\n",
+				       strerror(errno));
 
 		/*
 		 * TODO: if the kernel ever supports long-term R/W pinning on
@@ -202,7 +204,8 @@ 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\n");
+			ksft_test_result_skip("io_uring_queue_init() failed (%s)\n",
+					      strerror(-ret));
 			break;
 		}
 		/*
@@ -215,13 +218,15 @@ 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\n");
+			ksft_test_result(!should_work, "Should have failed (%s)\n",
+					 strerror(errno));
 		} else if (ret) {
 			/*
 			 * We might just lack support or have insufficient
 			 * MEMLOCK limits.
 			 */
-			ksft_test_result_skip("io_uring_register_buffers() failed\n");
+			ksft_test_result_skip("io_uring_register_buffers() failed (%s)\n",
+					      strerror(-ret));
 		} else {
 			ksft_test_result(should_work, "Should have worked\n");
 			io_uring_unregister_buffers(&ring);
@@ -249,7 +254,7 @@ static void run_with_memfd(test_fn fn, const char *desc)
 
 	fd = memfd_create("test", 0);
 	if (fd < 0) {
-		ksft_test_result_fail("memfd_create() failed\n");
+		ksft_test_result_fail("memfd_create() failed (%s)\n", strerror(errno));
 		return;
 	}
 
@@ -266,13 +271,13 @@ static void run_with_tmpfile(test_fn fn, const char *desc)
 
 	file = tmpfile();
 	if (!file) {
-		ksft_test_result_fail("tmpfile() failed\n");
+		ksft_test_result_fail("tmpfile() failed (%s)\n", strerror(errno));
 		return;
 	}
 
 	fd = fileno(file);
 	if (fd < 0) {
-		ksft_test_result_fail("fileno() failed\n");
+		ksft_test_result_fail("fileno() failed (%s)\n", strerror(errno));
 		goto close;
 	}
 
@@ -290,12 +295,12 @@ static void run_with_local_tmpfile(test_fn fn, const char *desc)
 
 	fd = mkstemp(filename);
 	if (fd < 0) {
-		ksft_test_result_fail("mkstemp() failed\n");
+		ksft_test_result_fail("mkstemp() failed (%s)\n", strerror(errno));
 		return;
 	}
 
 	if (unlink(filename)) {
-		ksft_test_result_fail("unlink() failed\n");
+		ksft_test_result_fail("unlink() failed (%s)\n", strerror(errno));
 		goto close;
 	}
 
@@ -317,7 +322,7 @@ static void run_with_memfd_hugetlb(test_fn fn, const char *desc,
 
 	fd = memfd_create("test", flags);
 	if (fd < 0) {
-		ksft_test_result_skip("memfd_create() failed\n");
+		ksft_test_result_skip("memfd_create() failed (%s)\n", strerror(errno));
 		return;
 	}
 

-- 
2.49.0.rc0.332.g42c0ae87b1-goog

[PATCH v4 02/12] selftests/mm: Skip uffd-stress if userfaultfd not available

[Brendan Jackman]

It's pretty obvious that the test wouldn't work if you don't have the
feature enabled. But, it's still useful to SKIP instead of failing so
the reader can immediately tell that this is the reason why.

Reviewed-by: Dev Jain <dev.jain@arm.com>
Signed-off-by: Brendan Jackman <jackmanb@google.com>
---
 tools/testing/selftests/mm/uffd-stress.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/mm/uffd-stress.c b/tools/testing/selftests/mm/uffd-stress.c
index 944d559ade21f255404eb38557660e54e81d46b8..91174e9425cde2500b459db78cb27adda6647b55 100644
--- a/tools/testing/selftests/mm/uffd-stress.c
+++ b/tools/testing/selftests/mm/uffd-stress.c
@@ -412,8 +412,8 @@ static void parse_test_type_arg(const char *raw_type)
 	 * feature.
 	 */
 
-	if (uffd_get_features(&features))
-		err("failed to get available features");
+	if (uffd_get_features(&features) && errno == ENOENT)
+		ksft_exit_skip("failed to get available features (%d)\n", errno);
 
 	test_uffdio_wp = test_uffdio_wp &&
 		(features & UFFD_FEATURE_PAGEFAULT_FLAG_WP);

-- 
2.49.0.rc0.332.g42c0ae87b1-goog

[PATCH v4 03/12] selftests/mm: Skip uffd-wp-mremap if userfaultfd not available

[Brendan Jackman]

It's obvious that this should fail in that case, but still, save the
reader the effort of figuring out that they've run into this by just
SKIPping

Reviewed-by: Dev Jain <dev.jain@arm.com>
Signed-off-by: Brendan Jackman <jackmanb@google.com>
---
 tools/testing/selftests/mm/uffd-wp-mremap.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/mm/uffd-wp-mremap.c b/tools/testing/selftests/mm/uffd-wp-mremap.c
index 2c4f984bd73caa17e12b9f4a5bb71e7fdf5d8554..c2ba7d46c7b4581a3c32a6b6acd148e3e89c2172 100644
--- a/tools/testing/selftests/mm/uffd-wp-mremap.c
+++ b/tools/testing/selftests/mm/uffd-wp-mremap.c
@@ -182,7 +182,10 @@ static void test_one_folio(size_t size, bool private, bool swapout, bool hugetlb
 
 	/* Register range for uffd-wp. */
 	if (userfaultfd_open(&features)) {
-		ksft_test_result_fail("userfaultfd_open() failed\n");
+		if (errno == ENOENT)
+			ksft_test_result_skip("userfaultfd not available\n");
+		else
+			ksft_test_result_fail("userfaultfd_open() failed\n");
 		goto out;
 	}
 	if (uffd_register(uffd, mem, size, false, true, false)) {

-- 
2.49.0.rc0.332.g42c0ae87b1-goog

[PATCH v4 04/12] selftests/mm/uffd: Rename nr_cpus -> nr_parallel

[Brendan Jackman]

A later commit will bound this variable so it no longer necessarily
matches the number of CPUs. Rename it appropriately.

Reviewed-by: Dev Jain <dev.jain@arm.com>
Signed-off-by: Brendan Jackman <jackmanb@google.com>
---
 tools/testing/selftests/mm/uffd-common.c     |  8 ++++----
 tools/testing/selftests/mm/uffd-common.h     |  2 +-
 tools/testing/selftests/mm/uffd-stress.c     | 28 ++++++++++++++--------------
 tools/testing/selftests/mm/uffd-unit-tests.c |  2 +-
 4 files changed, 20 insertions(+), 20 deletions(-)

diff --git a/tools/testing/selftests/mm/uffd-common.c b/tools/testing/selftests/mm/uffd-common.c
index 7ad6ba660c7d6f1f5762d0b231b92b05e971a3c5..dd01d2c95175b0329a75e220d2f43c915261090c 100644
--- a/tools/testing/selftests/mm/uffd-common.c
+++ b/tools/testing/selftests/mm/uffd-common.c
@@ -10,7 +10,7 @@
 #define BASE_PMD_ADDR ((void *)(1UL << 30))
 
 volatile bool test_uffdio_copy_eexist = true;
-unsigned long nr_cpus, nr_pages, nr_pages_per_cpu, page_size;
+unsigned long nr_parallel, nr_pages, nr_pages_per_cpu, page_size;
 char *area_src, *area_src_alias, *area_dst, *area_dst_alias, *area_remap;
 int uffd = -1, uffd_flags, finished, *pipefd, test_type;
 bool map_shared;
@@ -269,7 +269,7 @@ void uffd_test_ctx_clear(void)
 	size_t i;
 
 	if (pipefd) {
-		for (i = 0; i < nr_cpus * 2; ++i) {
+		for (i = 0; i < nr_parallel * 2; ++i) {
 			if (close(pipefd[i]))
 				err("close pipefd");
 		}
@@ -365,10 +365,10 @@ int uffd_test_ctx_init(uint64_t features, const char **errmsg)
 	 */
 	uffd_test_ops->release_pages(area_dst);
 
-	pipefd = malloc(sizeof(int) * nr_cpus * 2);
+	pipefd = malloc(sizeof(int) * nr_parallel * 2);
 	if (!pipefd)
 		err("pipefd");
-	for (cpu = 0; cpu < nr_cpus; cpu++)
+	for (cpu = 0; cpu < nr_parallel; cpu++)
 		if (pipe2(&pipefd[cpu * 2], O_CLOEXEC | O_NONBLOCK))
 			err("pipe");
 
diff --git a/tools/testing/selftests/mm/uffd-common.h b/tools/testing/selftests/mm/uffd-common.h
index a70ae10b5f6206daecc8e19ed3e3bbb388e265aa..7700cbfa397563d2f2bc82be45f96f2fc2032bbe 100644
--- a/tools/testing/selftests/mm/uffd-common.h
+++ b/tools/testing/selftests/mm/uffd-common.h
@@ -98,7 +98,7 @@ struct uffd_test_case_ops {
 };
 typedef struct uffd_test_case_ops uffd_test_case_ops_t;
 
-extern unsigned long nr_cpus, nr_pages, nr_pages_per_cpu, page_size;
+extern unsigned long nr_parallel, nr_pages, nr_pages_per_cpu, page_size;
 extern char *area_src, *area_src_alias, *area_dst, *area_dst_alias, *area_remap;
 extern int uffd, uffd_flags, finished, *pipefd, test_type;
 extern bool map_shared;
diff --git a/tools/testing/selftests/mm/uffd-stress.c b/tools/testing/selftests/mm/uffd-stress.c
index 91174e9425cde2500b459db78cb27adda6647b55..d6b57e5a2e1d7611aa1588ee41601ce16117a574 100644
--- a/tools/testing/selftests/mm/uffd-stress.c
+++ b/tools/testing/selftests/mm/uffd-stress.c
@@ -180,12 +180,12 @@ static void *background_thread(void *arg)
 static int stress(struct uffd_args *args)
 {
 	unsigned long cpu;
-	pthread_t locking_threads[nr_cpus];
-	pthread_t uffd_threads[nr_cpus];
-	pthread_t background_threads[nr_cpus];
+	pthread_t locking_threads[nr_parallel];
+	pthread_t uffd_threads[nr_parallel];
+	pthread_t background_threads[nr_parallel];
 
 	finished = 0;
-	for (cpu = 0; cpu < nr_cpus; cpu++) {
+	for (cpu = 0; cpu < nr_parallel; cpu++) {
 		if (pthread_create(&locking_threads[cpu], &attr,
 				   locking_thread, (void *)cpu))
 			return 1;
@@ -203,7 +203,7 @@ static int stress(struct uffd_args *args)
 				   background_thread, (void *)cpu))
 			return 1;
 	}
-	for (cpu = 0; cpu < nr_cpus; cpu++)
+	for (cpu = 0; cpu < nr_parallel; cpu++)
 		if (pthread_join(background_threads[cpu], NULL))
 			return 1;
 
@@ -219,11 +219,11 @@ static int stress(struct uffd_args *args)
 	uffd_test_ops->release_pages(area_src);
 
 	finished = 1;
-	for (cpu = 0; cpu < nr_cpus; cpu++)
+	for (cpu = 0; cpu < nr_parallel; cpu++)
 		if (pthread_join(locking_threads[cpu], NULL))
 			return 1;
 
-	for (cpu = 0; cpu < nr_cpus; cpu++) {
+	for (cpu = 0; cpu < nr_parallel; cpu++) {
 		char c;
 		if (bounces & BOUNCE_POLL) {
 			if (write(pipefd[cpu*2+1], &c, 1) != 1)
@@ -246,11 +246,11 @@ static int userfaultfd_stress(void)
 {
 	void *area;
 	unsigned long nr;
-	struct uffd_args args[nr_cpus];
+	struct uffd_args args[nr_parallel];
 	uint64_t mem_size = nr_pages * page_size;
 	int flags = 0;
 
-	memset(args, 0, sizeof(struct uffd_args) * nr_cpus);
+	memset(args, 0, sizeof(struct uffd_args) * nr_parallel);
 
 	if (features & UFFD_FEATURE_WP_UNPOPULATED && test_type == TEST_ANON)
 		flags = UFFD_FEATURE_WP_UNPOPULATED;
@@ -325,7 +325,7 @@ static int userfaultfd_stress(void)
 		 */
 		uffd_test_ops->release_pages(area_dst);
 
-		uffd_stats_reset(args, nr_cpus);
+		uffd_stats_reset(args, nr_parallel);
 
 		/* bounce pass */
 		if (stress(args)) {
@@ -359,7 +359,7 @@ static int userfaultfd_stress(void)
 
 		swap(area_src_alias, area_dst_alias);
 
-		uffd_stats_report(args, nr_cpus);
+		uffd_stats_report(args, nr_parallel);
 	}
 	uffd_test_ctx_clear();
 
@@ -453,9 +453,9 @@ int main(int argc, char **argv)
 		return KSFT_SKIP;
 	}
 
-	nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
+	nr_parallel = sysconf(_SC_NPROCESSORS_ONLN);
 
-	nr_pages_per_cpu = bytes / page_size / nr_cpus;
+	nr_pages_per_cpu = bytes / page_size / nr_parallel;
 	if (!nr_pages_per_cpu) {
 		_err("invalid MiB");
 		usage();
@@ -466,7 +466,7 @@ int main(int argc, char **argv)
 		_err("invalid bounces");
 		usage();
 	}
-	nr_pages = nr_pages_per_cpu * nr_cpus;
+	nr_pages = nr_pages_per_cpu * nr_parallel;
 
 	printf("nr_pages: %lu, nr_pages_per_cpu: %lu\n",
 	       nr_pages, nr_pages_per_cpu);
diff --git a/tools/testing/selftests/mm/uffd-unit-tests.c b/tools/testing/selftests/mm/uffd-unit-tests.c
index 74c8bc02b5063f4667c4284c432edc7dee7ba3a5..24ea82ee223184612781adc852460138c4fe28f0 100644
--- a/tools/testing/selftests/mm/uffd-unit-tests.c
+++ b/tools/testing/selftests/mm/uffd-unit-tests.c
@@ -198,7 +198,7 @@ uffd_setup_environment(uffd_test_args_t *args, uffd_test_case_t *test,
 
 	nr_pages = UFFD_TEST_MEM_SIZE / page_size;
 	/* TODO: remove this global var.. it's so ugly */
-	nr_cpus = 1;
+	nr_parallel = 1;
 
 	/* Initialize test arguments */
 	args->mem_type = mem_type;

-- 
2.49.0.rc0.332.g42c0ae87b1-goog

[PATCH v4 05/12] selftests/mm: Print some details when uffd-stress gets bad params

[Brendan Jackman]

So this can be debugged more easily.

Signed-off-by: Brendan Jackman <jackmanb@google.com>
---
 tools/testing/selftests/mm/uffd-stress.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/mm/uffd-stress.c b/tools/testing/selftests/mm/uffd-stress.c
index d6b57e5a2e1d7611aa1588ee41601ce16117a574..4ba5bf13a0108435ce8b53340b9e17ccd47e859e 100644
--- a/tools/testing/selftests/mm/uffd-stress.c
+++ b/tools/testing/selftests/mm/uffd-stress.c
@@ -457,7 +457,8 @@ int main(int argc, char **argv)
 
 	nr_pages_per_cpu = bytes / page_size / nr_parallel;
 	if (!nr_pages_per_cpu) {
-		_err("invalid MiB");
+		_err("pages_per_cpu = 0, cannot test (%lu / %lu / %lu)",
+			bytes, page_size, nr_parallel);
 		usage();
 	}
 

-- 
2.49.0.rc0.332.g42c0ae87b1-goog

[PATCH v4 06/12] selftests/mm: Don't fail uffd-stress if too many CPUs

[Brendan Jackman]

This calculation divides a fixed parameter by an environment-dependent
parameter i.e. the number of CPUs.

The simple way to avoid machine-specific failures here is to just put a
cap on the max value of the latter.

Suggested-by: Mateusz Guzik <mjguzik@gmail.com>
Signed-off-by: Brendan Jackman <jackmanb@google.com>
---
 tools/testing/selftests/mm/uffd-stress.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/mm/uffd-stress.c b/tools/testing/selftests/mm/uffd-stress.c
index 4ba5bf13a0108435ce8b53340b9e17ccd47e859e..40af7f67c4074d901be6608e5d64bd0490026dae 100644
--- a/tools/testing/selftests/mm/uffd-stress.c
+++ b/tools/testing/selftests/mm/uffd-stress.c
@@ -435,6 +435,7 @@ static void sigalrm(int sig)
 
 int main(int argc, char **argv)
 {
+	unsigned long nr_cpus;
 	size_t bytes;
 
 	if (argc < 4)
@@ -453,7 +454,15 @@ int main(int argc, char **argv)
 		return KSFT_SKIP;
 	}
 
-	nr_parallel = sysconf(_SC_NPROCESSORS_ONLN);
+	nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
+	if (nr_cpus > 32) {
+		/* Don't let calculation below go to zero. */
+		ksft_print_msg("_SC_NPROCESSORS_ONLN (%lu) too large, capping nr_threads to 32\n",
+			       nr_cpus);
+		nr_parallel = 32;
+	} else {
+		nr_parallel = nr_cpus;
+	}
 
 	nr_pages_per_cpu = bytes / page_size / nr_parallel;
 	if (!nr_pages_per_cpu) {

-- 
2.49.0.rc0.332.g42c0ae87b1-goog

[PATCH v4 07/12] selftests/mm: Skip map_populate on weird filesystems

[Brendan Jackman]

It seems that 9pfs does not allow truncating unlinked files, Mark Brown
has noted that NFS may also behave this way.

It doesn't seem quite right to call this a "bug" but it's probably a
special enough case that it makes sense for the test to just SKIP if it
happens.

Signed-off-by: Brendan Jackman <jackmanb@google.com>
---
 tools/testing/selftests/mm/map_populate.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/tools/testing/selftests/mm/map_populate.c b/tools/testing/selftests/mm/map_populate.c
index 5c8a53869b1bd287b09a250edf628a66c25c2439..433e54fb634f793f2eb4c53ba6b791045c9f4986 100644
--- a/tools/testing/selftests/mm/map_populate.c
+++ b/tools/testing/selftests/mm/map_populate.c
@@ -87,6 +87,13 @@ int main(int argc, char **argv)
 	BUG_ON(!ftmp, "tmpfile()");
 
 	ret = ftruncate(fileno(ftmp), MMAP_SZ);
+	if (ret < 0 && errno == ENOENT) {
+		/*
+		 * This probably means tmpfile() made a file on a filesystem
+		 * that doesn't handle temporary files the way we want.
+		 */
+		ksft_exit_skip("ftruncate(fileno(tmpfile())) gave ENOENT, weird filesystem?\n");
+	}
 	BUG_ON(ret, "ftruncate()");
 
 	smap = mmap(0, MMAP_SZ, PROT_READ | PROT_WRITE,

-- 
2.49.0.rc0.332.g42c0ae87b1-goog

[PATCH v4 08/12] selftests/mm: Skip gup_longterm tests on weird filesystems

[Brendan Jackman]

Some filesystems don't support ftruncate()ing unlinked files. They return
ENOENT. In that case, skip the test.

Signed-off-by: Brendan Jackman <jackmanb@google.com>
---
 tools/testing/selftests/mm/gup_longterm.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/mm/gup_longterm.c b/tools/testing/selftests/mm/gup_longterm.c
index 15335820656b1c143b440b8a1065a025378e22a2..03271442aae5aed060fd44010df552a2eedcdafc 100644
--- a/tools/testing/selftests/mm/gup_longterm.c
+++ b/tools/testing/selftests/mm/gup_longterm.c
@@ -96,7 +96,15 @@ static void do_test(int fd, size_t size, enum test_type type, bool shared)
 	int ret;
 
 	if (ftruncate(fd, size)) {
-		ksft_test_result_fail("ftruncate() failed (%s)\n", strerror(errno));
+		if (errno == ENOENT) {
+			/*
+			 * This can happen if the file has been unlinked and the
+			 * filesystem doesn't support truncating unlinked files.
+			 */
+			ksft_test_result_skip("ftruncate() failed with ENOENT\n");
+		} else {
+			ksft_test_result_fail("ftruncate() failed (%s)\n", strerror(errno));
+		}
 		return;
 	}
 

-- 
2.49.0.rc0.332.g42c0ae87b1-goog

[PATCH v4 09/12] selftests/mm: Drop unnecessary sudo usage

[Brendan Jackman]

This script must be run as root anyway (see all the writing to
privileged files in /proc etc).

Remove the unnecessary use of sudo to avoid breaking on single-user
systems that don't have sudo. This also avoids confusing readers.

Reviewed-by: Dev Jain <dev.jain@arm.com>
Signed-off-by: Brendan Jackman <jackmanb@google.com>
---
 tools/testing/selftests/mm/run_vmtests.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
index da7e266681031d2772fb0c4139648904a18e0bf9..0f9fe757c3320a6551e39b6d4552fd4874b0bf43 100755
--- a/tools/testing/selftests/mm/run_vmtests.sh
+++ b/tools/testing/selftests/mm/run_vmtests.sh
@@ -386,7 +386,7 @@ CATEGORY="madv_populate" run_test ./madv_populate
 
 if [ -x ./memfd_secret ]
 then
-(echo 0 | sudo tee /proc/sys/kernel/yama/ptrace_scope 2>&1) | tap_prefix
+(echo 0 > /proc/sys/kernel/yama/ptrace_scope 2>&1) | tap_prefix
 CATEGORY="memfd_secret" run_test ./memfd_secret
 fi
 

-- 
2.49.0.rc0.332.g42c0ae87b1-goog

[PATCH v4 10/12] selftests/mm: Ensure uffd-wp-mremap gets pages of each size

[Brendan Jackman]

This test allocates a page of every available size and doesn't have any
SKIP logic if the allocation fails. So, ensure it's available and skip
the test if we can't do so.

Signed-off-by: Brendan Jackman <jackmanb@google.com>
---
 tools/testing/selftests/mm/run_vmtests.sh | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
index 0f9fe757c3320a6551e39b6d4552fd4874b0bf43..e86ef8cb37d00e572be8cf0ea9cc8246d4eecd7e 100755
--- a/tools/testing/selftests/mm/run_vmtests.sh
+++ b/tools/testing/selftests/mm/run_vmtests.sh
@@ -309,9 +309,30 @@ CATEGORY="userfaultfd" run_test ${uffd_stress_bin} hugetlb "$half_ufd_size_MB" 3
 CATEGORY="userfaultfd" run_test ${uffd_stress_bin} hugetlb-private "$half_ufd_size_MB" 32
 CATEGORY="userfaultfd" run_test ${uffd_stress_bin} shmem 20 16
 CATEGORY="userfaultfd" run_test ${uffd_stress_bin} shmem-private 20 16
-CATEGORY="userfaultfd" run_test ./uffd-wp-mremap
+# uffd-wp-mremap requires at least one page of each size.
+have_all_size_hugepgs=true
+declare -A nr_size_hugepgs
+for f in /sys/kernel/mm/hugepages/**/nr_hugepages; do
+	old=$(cat $f)
+	nr_size_hugepgs["$f"]="$old"
+	if [ "$old" == 0 ]; then
+		echo 1 > "$f"
+	fi
+	if [ $(cat "$f") == 0 ]; then
+		have_all_size_hugepgs=false
+		break
+	fi
+done
+if $have_all_size_hugepgs; then
+	CATEGORY="userfaultfd" run_test ./uffd-wp-mremap
+else
+	echo "# SKIP ./uffd-wp-mremap"
+fi
 
 #cleanup
+for f in "${!nr_size_hugepgs[@]}"; do
+	echo "${nr_size_hugepgs["$f"]}" > "$f"
+done
 echo "$nr_hugepgs" > /proc/sys/vm/nr_hugepages
 
 CATEGORY="compaction" run_test ./compaction_test

-- 
2.49.0.rc0.332.g42c0ae87b1-goog

[PATCH v4 11/12] selftests/mm: Skip mlock tests if nobody user can't read it

[Brendan Jackman]

If running from a directory that can't be read by unprivileged users,
executing on-fault-test via the nobody user will fail.

The kselftest build does give the file the correct permissions, but
after being installed it might be in a directory without global execute
permissions.

Since the script can't safely fix that, just skip if it happens. Note
that the stderr of the `ls` command is unfiltered meaning the user sees
a "permission denied" error that can help inform them why the test was
skipped.

Signed-off-by: Brendan Jackman <jackmanb@google.com>
---
 tools/testing/selftests/mm/run_vmtests.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
index e86ef8cb37d00e572be8cf0ea9cc8246d4eecd7e..1467594b594c4fb1dceae875fe7616ecc3cd9382 100755
--- a/tools/testing/selftests/mm/run_vmtests.sh
+++ b/tools/testing/selftests/mm/run_vmtests.sh
@@ -337,7 +337,7 @@ echo "$nr_hugepgs" > /proc/sys/vm/nr_hugepages
 
 CATEGORY="compaction" run_test ./compaction_test
 
-if command -v sudo &> /dev/null;
+if command -v sudo &> /dev/null && sudo -u nobody ls ./on-fault-limit >/dev/null;
 then
 	CATEGORY="mlock" run_test sudo -u nobody ./on-fault-limit
 else

-- 
2.49.0.rc0.332.g42c0ae87b1-goog

[PATCH v4 12/12] selftests/mm/mlock: Print error on failure

[Brendan Jackman]

It's not really possible to start diagnosing this without knowing the
actual error.

Also update the mlock2 helper to behave like libc would by setting errno
and returning -1.

Signed-off-by: Brendan Jackman <jackmanb@google.com>
---
 tools/testing/selftests/mm/mlock-random-test.c | 4 ++--
 tools/testing/selftests/mm/mlock2.h            | 8 +++++++-
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/mm/mlock-random-test.c b/tools/testing/selftests/mm/mlock-random-test.c
index 1cd80b0f76c33f04ef01f4dee6602f28b6a7c991..b8d7e966f44c67e5606d384bd660e5a4e5e8fda9 100644
--- a/tools/testing/selftests/mm/mlock-random-test.c
+++ b/tools/testing/selftests/mm/mlock-random-test.c
@@ -161,9 +161,9 @@ static void test_mlock_within_limit(char *p, int alloc_size)
 				       MLOCK_ONFAULT);
 
 		if (ret)
-			ksft_exit_fail_msg("%s() failure at |%p(%d)| mlock:|%p(%d)|\n",
+			ksft_exit_fail_msg("%s() failure (%s) at |%p(%d)| mlock:|%p(%d)|\n",
 					   is_mlock ? "mlock" : "mlock2",
-					   p, alloc_size,
+					   strerror(errno), p, alloc_size,
 					   p + start_offset, lock_size);
 	}
 
diff --git a/tools/testing/selftests/mm/mlock2.h b/tools/testing/selftests/mm/mlock2.h
index 4417eaa5cfb78ba2bb0f51d3418c9b768ff0fe90..81e77fa41901a095cc041e05d01da7dffbf2f4fe 100644
--- a/tools/testing/selftests/mm/mlock2.h
+++ b/tools/testing/selftests/mm/mlock2.h
@@ -6,7 +6,13 @@
 
 static int mlock2_(void *start, size_t len, int flags)
 {
-	return syscall(__NR_mlock2, start, len, flags);
+	int ret = syscall(__NR_mlock2, start, len, flags);
+
+	if (ret) {
+		errno = ret;
+		return -1;
+	}
+	return 0;
 }
 
 static FILE *seek_to_smaps_entry(unsigned long addr)

-- 
2.49.0.rc0.332.g42c0ae87b1-goog