[PATCH 0/4] selftests/mm: Tweaks to the cow test

[PATCH 0/4] selftests/mm: Tweaks to the cow test

[Mark Brown]

A collection of non-functional updates from David Hildenbrand's review.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
Mark Brown (4):
      kselftest/mm: Clarify errors for pipe()
      selftests/mm: Convert some cow error reports to ksft_perror()
      selftests/mm: Don't compare return values to in cow
      selftests/mm: Add messages about test errors to the cow tests

 tools/testing/selftests/mm/cow.c | 44 +++++++++++++++++++++++++---------------
 1 file changed, 28 insertions(+), 16 deletions(-)
---
base-commit: 19272b37aa4f83ca52bdf9c16d5d81bdd1354494
change-id: 20250603-selftest-mm-cow-tweaks-0199c5132b3e

Best regards,
-- 
Mark Brown <broonie@kernel.org>

[PATCH 1/4] kselftest/mm: Clarify errors for pipe()

[Mark Brown]

Specify that errors reported from pipe() failures are the result of
failures.

Suggested-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 tools/testing/selftests/mm/cow.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/mm/cow.c b/tools/testing/selftests/mm/cow.c
index dbbcc5eb3dce..0adc0ab142c1 100644
--- a/tools/testing/selftests/mm/cow.c
+++ b/tools/testing/selftests/mm/cow.c
@@ -113,11 +113,11 @@ struct comm_pipes {
 static int setup_comm_pipes(struct comm_pipes *comm_pipes)
 {
 	if (pipe(comm_pipes->child_ready) < 0) {
-		ksft_perror("pipe()");
+		ksft_perror("pipe() failed");
 		return -errno;
 	}
 	if (pipe(comm_pipes->parent_ready) < 0) {
-		ksft_perror("pipe()");
+		ksft_perror("pipe() failed");
 		close(comm_pipes->child_ready[0]);
 		close(comm_pipes->child_ready[1]);
 		return -errno;

-- 
2.39.5

[PATCH 2/4] selftests/mm: Convert some cow error reports to ksft_perror()

[Mark Brown]

This prints the errno and a string decode of it.

Reported-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 tools/testing/selftests/mm/cow.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/mm/cow.c b/tools/testing/selftests/mm/cow.c
index 0adc0ab142c1..ff80329313e4 100644
--- a/tools/testing/selftests/mm/cow.c
+++ b/tools/testing/selftests/mm/cow.c
@@ -332,7 +332,7 @@ static void do_test_vmsplice_in_parent(char *mem, size_t size,
 	if (before_fork) {
 		transferred = vmsplice(fds[1], &iov, 1, 0);
 		if (transferred <= 0) {
-			ksft_print_msg("vmsplice() failed\n");
+			ksft_perror("vmsplice() failed\n");
 			log_test_result(KSFT_FAIL);
 			goto close_pipe;
 		}
@@ -562,7 +562,7 @@ static void do_test_iouring(char *mem, size_t size, bool use_fork)
 	while (total < size) {
 		cur = pread(fd, tmp + total, size - total, total);
 		if (cur < 0) {
-			ksft_print_msg("pread() failed\n");
+			ksft_perror("pread() failed\n");
 			log_test_result(KSFT_FAIL);
 			goto quit_child;
 		}
@@ -628,7 +628,7 @@ static void do_test_ro_pin(char *mem, size_t size, enum ro_pin_test test,
 
 	tmp = malloc(size);
 	if (!tmp) {
-		ksft_print_msg("malloc() failed\n");
+		ksft_perror("malloc() failed\n");
 		log_test_result(KSFT_FAIL);
 		return;
 	}

-- 
2.39.5

[PATCH 3/4] selftests/mm: Don't compare return values to in cow

[Mark Brown]

Tweak the coding style for checking for non-zero return values.
While we're at it also remove a now redundant oring of the madvise()
return code.

Suggested-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 tools/testing/selftests/mm/cow.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/mm/cow.c b/tools/testing/selftests/mm/cow.c
index ff80329313e4..48fcf03aa4cd 100644
--- a/tools/testing/selftests/mm/cow.c
+++ b/tools/testing/selftests/mm/cow.c
@@ -1613,13 +1613,13 @@ static void run_with_huge_zeropage(non_anon_test_fn fn, const char *desc)
 	smem = (char *)(((uintptr_t)mmap_smem + pmdsize) & ~(pmdsize - 1));
 
 	ret = madvise(mem, pmdsize, MADV_HUGEPAGE);
-	if (ret != 0) {
+	if (ret) {
 		ksft_perror("madvise()");
 		log_test_result(KSFT_FAIL);
 		goto munmap;
 	}
-	ret |= madvise(smem, pmdsize, MADV_HUGEPAGE);
-	if (ret != 0) {
+	ret = madvise(smem, pmdsize, MADV_HUGEPAGE);
+	if (ret) {
 		ksft_perror("madvise()");
 		log_test_result(KSFT_FAIL);
 		goto munmap;

-- 
2.39.5

[PATCH 4/4] selftests/mm: Add messages about test errors to the cow tests

[Mark Brown]

It is not sufficiently clear what the individual tests in the cow test
program are checking so add messages for the failure cases.

Suggested-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 tools/testing/selftests/mm/cow.c | 28 ++++++++++++++++++++--------
 1 file changed, 20 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/mm/cow.c b/tools/testing/selftests/mm/cow.c
index 48fcf03aa4cd..29767e2afdd0 100644
--- a/tools/testing/selftests/mm/cow.c
+++ b/tools/testing/selftests/mm/cow.c
@@ -268,8 +268,10 @@ static void do_test_cow_in_parent(char *mem, size_t size, bool do_mprotect,
 		 * fail because (a) harder to fix and (b) nobody really cares.
 		 * Flag them as expected failure for now.
 		 */
+		ksft_print_msg("Leak from parent into child\n");
 		log_test_result(KSFT_XFAIL);
 	} else {
+		ksft_print_msg("Leak from parent into child\n");
 		log_test_result(KSFT_FAIL);
 	}
 close_comm_pipes:
@@ -397,8 +399,10 @@ static void do_test_vmsplice_in_parent(char *mem, size_t size,
 		 * fail because (a) harder to fix and (b) nobody really cares.
 		 * Flag them as expected failure for now.
 		 */
+		ksft_print_msg("Leak from child into parent\n");
 		log_test_result(KSFT_XFAIL);
 	} else {
+		ksft_print_msg("Leak from child into parent\n");
 		log_test_result(KSFT_FAIL);
 	}
 close_pipe:
@@ -570,10 +574,12 @@ static void do_test_iouring(char *mem, size_t size, bool use_fork)
 	}
 
 	/* Finally, check if we read what we expected. */
-	if (!memcmp(mem, tmp, size))
+	if (!memcmp(mem, tmp, size)) {
 		log_test_result(KSFT_PASS);
-	else
+	} else {
+		ksft_print_msg("Longtom R/W pin is not reliable\n");
 		log_test_result(KSFT_FAIL);
+	}
 
 quit_child:
 	if (use_fork) {
@@ -725,10 +731,12 @@ static void do_test_ro_pin(char *mem, size_t size, enum ro_pin_test test,
 		ksft_perror("PIN_LONGTERM_TEST_READ failed");
 		log_test_result(KSFT_FAIL);
 	} else {
-		if (!memcmp(mem, tmp, size))
+		if (!memcmp(mem, tmp, size)) {
 			log_test_result(KSFT_PASS);
-		else
+		} else {
+			ksft_print_msg("Longterm R/O pin is not reliable\n");
 			log_test_result(KSFT_FAIL);
+		}
 	}
 
 	ret = ioctl(gup_fd, PIN_LONGTERM_TEST_STOP);
@@ -1417,10 +1425,12 @@ static void do_test_anon_thp_collapse(char *mem, size_t size,
 	else
 		ret = -EINVAL;
 
-	if (!ret)
+	if (!ret) {
 		log_test_result(KSFT_PASS);
-	else
+	} else {
+		ksft_print_msg("Leak from parent into child\n");
 		log_test_result(KSFT_FAIL);
+	}
 close_comm_pipes:
 	close_comm_pipes(&comm_pipes);
 }
@@ -1528,10 +1538,12 @@ static void test_cow(char *mem, const char *smem, size_t size)
 	memset(mem, 0xff, size);
 
 	/* See if we still read the old values via the other mapping. */
-	if (!memcmp(smem, old, size))
+	if (!memcmp(smem, old, size)) {
 		log_test_result(KSFT_PASS);
-	else
+	} else {
+		ksft_print_msg("Other mapping modified\n");
 		log_test_result(KSFT_FAIL);
+	}
 	free(old);
 }
 

-- 
2.39.5

Re: [PATCH 1/4] kselftest/mm: Clarify errors for pipe()

[David Hildenbrand]

On 10.06.25 16:13, Mark Brown wrote:
> Specify that errors reported from pipe() failures are the result of
> failures.
> 
> Suggested-by: David Hildenbrand <david@redhat.com>
> Signed-off-by: Mark Brown <broonie@kernel.org>
> ---

Acked-by: David Hildenbrand <david@redhat.com>

-- 
Cheers,

David / dhildenb

Re: [PATCH 2/4] selftests/mm: Convert some cow error reports to ksft_perror()

[David Hildenbrand]

On 10.06.25 16:13, Mark Brown wrote:
> This prints the errno and a string decode of it.
> 
> Reported-by: David Hildenbrand <david@redhat.com>

Probably not "Reported-by". Did you mean "Suggested-by" like for the others?

> Signed-off-by: Mark Brown <broonie@kernel.org>
> ---

Acked-by: David Hildenbrand <david@redhat.com>

-- 
Cheers,

David / dhildenb

Re: [PATCH 3/4] selftests/mm: Don't compare return values to in cow

[David Hildenbrand]

On 10.06.25 16:13, Mark Brown wrote:
> Tweak the coding style for checking for non-zero return values.
> While we're at it also remove a now redundant oring of the madvise()
> return code.
> 
> Suggested-by: David Hildenbrand <david@redhat.com>
> Signed-off-by: Mark Brown <broonie@kernel.org>
> ---

Acked-by: David Hildenbrand <david@redhat.com>

-- 
Cheers,

David / dhildenb

Re: [PATCH 4/4] selftests/mm: Add messages about test errors to the cow tests

[David Hildenbrand]

On 10.06.25 16:13, Mark Brown wrote:
> It is not sufficiently clear what the individual tests in the cow test
> program are checking so add messages for the failure cases.
> 
> Suggested-by: David Hildenbrand <david@redhat.com>
> Signed-off-by: Mark Brown <broonie@kernel.org>
> ---

Thanks!

Acked-by: David Hildenbrand <david@redhat.com>

-- 
Cheers,

David / dhildenb

Re: [PATCH 2/4] selftests/mm: Convert some cow error reports to ksft_perror()

[Mark Brown]

[-- Attachment #1: Type: text/plain, Size: 379 bytes --]

On Wed, Jun 11, 2025 at 02:10:20PM +0200, David Hildenbrand wrote:
> On 10.06.25 16:13, Mark Brown wrote:
> > This prints the errno and a string decode of it.
> > 
> > Reported-by: David Hildenbrand <david@redhat.com>
> 
> Probably not "Reported-by". Did you mean "Suggested-by" like for the others?

Probably. I'm sure I was thinking something there but not sure what.

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]