Re: [PATCH 3/3] tools/testing/selftests: assert that anon merge cases behave as expected

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

I know you mean well Wei,

But drive-by extremely pedantic review on minor details isn't really
useful. I can't tell you not to do this, but I can at least ask. I don't
think this is a great use of either of our time.

Thanks.

On Mon, Apr 07, 2025 at 02:54:56AM +0000, Wei Yang wrote:
> On Mon, Mar 17, 2025 at 09:15:05PM +0000, Lorenzo Stoakes wrote:
> >Prior to the recently applied commit that permits this merge,
> >mprotect()'ing a faulted VMA, adjacent to an unfaulted VMA, such that the
> >two share characteristics would fail to merge due to what appear to be
> >unintended consequences of commit 965f55dea0e3 ("mmap: avoid merging cloned
> >VMAs").
> >
> >Now we have fixed this bug, assert that we can indeed merge anonymous VMAs
> >this way.
> >
> >Also assert that forked source/target VMAs are equally
> >rejected. Previously, all empty target anon merges with one VMA faulted and
> >the other unfaulted would be rejected incorrectly, now we ensure that
> >unforked merge, but forked do not.
> >
> >Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> >---
> > tools/testing/selftests/mm/.gitignore     |   1 +
> > tools/testing/selftests/mm/Makefile       |   1 +
> > tools/testing/selftests/mm/merge.c        | 454 ++++++++++++++++++++++
> > tools/testing/selftests/mm/run_vmtests.sh |   2 +
> > 4 files changed, 458 insertions(+)
> > create mode 100644 tools/testing/selftests/mm/merge.c
> >
> >diff --git a/tools/testing/selftests/mm/.gitignore b/tools/testing/selftests/mm/.gitignore
> >index c5241b193db8..91db34941a14 100644
> >--- a/tools/testing/selftests/mm/.gitignore
> >+++ b/tools/testing/selftests/mm/.gitignore
> >@@ -58,3 +58,4 @@ hugetlb_dio
> > pkey_sighandler_tests_32
> > pkey_sighandler_tests_64
> > guard-regions
> >+merge
> >diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile
> >index 8270895039d1..ad4d6043a60f 100644
> >--- a/tools/testing/selftests/mm/Makefile
> >+++ b/tools/testing/selftests/mm/Makefile
> >@@ -98,6 +98,7 @@ TEST_GEN_FILES += hugetlb_madv_vs_map
> > TEST_GEN_FILES += hugetlb_dio
> > TEST_GEN_FILES += droppable
> > TEST_GEN_FILES += guard-regions
> >+TEST_GEN_FILES += merge
> >
> > ifneq ($(ARCH),arm64)
> > TEST_GEN_FILES += soft-dirty
> >diff --git a/tools/testing/selftests/mm/merge.c b/tools/testing/selftests/mm/merge.c
> >new file mode 100644
> >index 000000000000..9cc61bdbfba8
> >--- /dev/null
> >+++ b/tools/testing/selftests/mm/merge.c
> >@@ -0,0 +1,454 @@
> >+// SPDX-License-Identifier: GPL-2.0-or-later
> >+
> >+#define _GNU_SOURCE
> >+#include "../kselftest_harness.h"
> >+#include <stdio.h>
> >+#include <stdlib.h>
> >+#include <unistd.h>
> >+#include <sys/mman.h>
> >+#include <sys/wait.h>
> >+#include "vm_util.h"
> >+
> >+FIXTURE(merge)
> >+{
> >+	unsigned int page_size;
> >+	char *carveout;
> >+	struct procmap_fd procmap;
> >+};
> >+
> >+FIXTURE_SETUP(merge)
> >+{
> >+	self->page_size = psize();
> >+	/* Carve out PROT_NONE region to map over. */
> >+	self->carveout = mmap(NULL, 12 * self->page_size, PROT_NONE,
> >+			      MAP_ANON | MAP_PRIVATE, -1, 0);
> >+	ASSERT_NE(self->carveout, MAP_FAILED);
> >+	/* Setup PROCMAP_QUERY interface. */
> >+	ASSERT_EQ(open_self_procmap(&self->procmap), 0);
> >+}
> >+
> >+FIXTURE_TEARDOWN(merge)
> >+{
> >+	ASSERT_EQ(munmap(self->carveout, 12 * self->page_size), 0);
> >+	ASSERT_EQ(close_procmap(&self->procmap), 0);
> >+}
> >+
> >+TEST_F(merge, mprotect_unfaulted_left)
> >+{
> >+	unsigned int page_size = self->page_size;
> >+	char *carveout = self->carveout;
> >+	struct procmap_fd *procmap = &self->procmap;
> >+	char *ptr;
> >+
> >+	/*
> >+	 * Map 10 pages of R/W memory within. MAP_NORESERVE so we don't hit
> >+	 * merge failure due to lack of VM_ACCOUNT flag by mistake.
> >+	 *
> >+	 * |-----------------------|
> >+	 * |       unfaulted       |
> >+	 * |-----------------------|
> >+	 */
> >+	ptr = mmap(&carveout[page_size], 10 * page_size, PROT_READ | PROT_WRITE,
> >+		   MAP_ANON | MAP_PRIVATE | MAP_FIXED | MAP_NORESERVE, -1, 0);
> >+	ASSERT_NE(ptr, MAP_FAILED);
> >+	/*
> >+	 * Now make the first 5 pages read-only, splitting the VMA:
> >+	 *
> >+	 *      RO          RW
> >+	 * |-----------|-----------|
> >+	 * | unfaulted | unfaulted |
> >+	 * |-----------|-----------|
> >+	 */
> >+	ASSERT_EQ(mprotect(ptr, 5 * page_size, PROT_READ), 0);
> >+	/*
> >+	 * Fault in the first of the last 5 pages so it gets an anon_vma and
> >+	 * thus the whole VMA becomes 'faulted':
> >+	 *
> >+	 *      RO          RW
> >+	 * |-----------|-----------|
> >+	 * | unfaulted |  faulted  |
> >+	 * |-----------|-----------|
> >+	 */
> >+	ptr[5 * page_size] = 'x';
> >+	/*
> >+	 * Now mprotect() the RW region read-only, we should merge (though for
> >+	 * ~15 years we did not! :):
> >+	 *
> >+	 *             RO
> >+	 * |-----------------------|
> >+	 * |        faulted        |
> >+	 * |-----------------------|
> >+	 */
> >+	ASSERT_EQ(mprotect(&ptr[5 * page_size], 5 * page_size, PROT_READ), 0);
> >+
> >+	/* Assert that the merge succeeded using PROCMAP_QUERY. */
> >+	ASSERT_TRUE(find_vma_procmap(procmap, ptr));
> >+	ASSERT_EQ(procmap->query.vma_start, (unsigned long)ptr);
> >+	ASSERT_EQ(procmap->query.vma_end, (unsigned long)ptr + 10 * page_size);
> >+}
> >+
> >+TEST_F(merge, mprotect_unfaulted_right)
> >+{
> >+	unsigned int page_size = self->page_size;
> >+	char *carveout = self->carveout;
> >+	struct procmap_fd *procmap = &self->procmap;
> >+	char *ptr;
> >+
> >+	/*
> >+	 * |-----------------------|
> >+	 * |       unfaulted       |
> >+	 * |-----------------------|
> >+	 */
> >+	ptr = mmap(&carveout[page_size], 10 * page_size, PROT_READ | PROT_WRITE,
> >+		   MAP_ANON | MAP_PRIVATE | MAP_FIXED | MAP_NORESERVE, -1, 0);
> >+	ASSERT_NE(ptr, MAP_FAILED);
> >+	/*
> >+	 * Now make the last 5 pages read-only, splitting the VMA:
> >+	 *
> >+	 *      RW          RO
> >+	 * |-----------|-----------|
> >+	 * | unfaulted | unfaulted |
> >+	 * |-----------|-----------|
> >+	 */
> >+	ASSERT_EQ(mprotect(&ptr[5 * page_size], 5 * page_size, PROT_READ), 0);
> >+	/*
> >+	 * Fault in the first of the first 5 pages so it gets an anon_vma and
> >+	 * thus the whole VMA becomes 'faulted':
> >+	 *
> >+	 *      RW          RO
> >+	 * |-----------|-----------|
> >+	 * |  faulted  | unfaulted |
> >+	 * |-----------|-----------|
> >+	 */
> >+	ptr[0] = 'x';
> >+	/*
> >+	 * Now mprotect() the RW region read-only, we should merge:
> >+	 *
> >+	 *             RO
> >+	 * |-----------------------|
> >+	 * |        faulted        |
> >+	 * |-----------------------|
> >+	 */
> >+	ASSERT_EQ(mprotect(ptr, 5 * page_size, PROT_READ), 0);
> >+
> >+	/* Assert that the merge succeeded using PROCMAP_QUERY. */
> >+	ASSERT_TRUE(find_vma_procmap(procmap, ptr));
> >+	ASSERT_EQ(procmap->query.vma_start, (unsigned long)ptr);
> >+	ASSERT_EQ(procmap->query.vma_end, (unsigned long)ptr + 10 * page_size);
> >+}
> >+
> >+TEST_F(merge, mprotect_unfaulted_both)
> >+{
> >+	unsigned int page_size = self->page_size;
> >+	char *carveout = self->carveout;
> >+	struct procmap_fd *procmap = &self->procmap;
> >+	char *ptr;
> >+
> >+	/*
> >+	 * |-----------------------|
> >+	 * |       unfaulted       |
> >+	 * |-----------------------|
> >+	 */
> >+	ptr = mmap(&carveout[2 * page_size], 9 * page_size, PROT_READ | PROT_WRITE,
> >+		   MAP_ANON | MAP_PRIVATE | MAP_FIXED | MAP_NORESERVE, -1, 0);
> >+	ASSERT_NE(ptr, MAP_FAILED);
> >+	/*
> >+	 * Now make the first and last 3 pages read-only, splitting the VMA:
> >+	 *
> >+	 *      RO          RW          RO
> >+	 * |-----------|-----------|-----------|
> >+	 * | unfaulted | unfaulted | unfaulted |
> >+	 * |-----------|-----------|-----------|
> >+	 */
> >+	ASSERT_EQ(mprotect(ptr, 3 * page_size, PROT_READ), 0);
> >+	ASSERT_EQ(mprotect(&ptr[6 * page_size], 3 * page_size, PROT_READ), 0);
> >+	/*
> >+	 * Fault in the first of the middle 3 pages so it gets an anon_vma and
> >+	 * thus the whole VMA becomes 'faulted':
> >+	 *
> >+	 *      RO          RW          RO
> >+	 * |-----------|-----------|-----------|
> >+	 * | unfaulted |  faulted  | unfaulted |
> >+	 * |-----------|-----------|-----------|
> >+	 */
> >+	ptr[3 * page_size] = 'x';
> >+	/*
> >+	 * Now mprotect() the RW region read-only, we should merge:
> >+	 *
> >+	 *             RO
> >+	 * |-----------------------|
> >+	 * |        faulted        |
> >+	 * |-----------------------|
> >+	 */
> >+	ASSERT_EQ(mprotect(&ptr[3 * page_size], 3 * page_size, PROT_READ), 0);
> >+
> >+	/* Assert that the merge succeeded using PROCMAP_QUERY. */
> >+	ASSERT_TRUE(find_vma_procmap(procmap, ptr));
> >+	ASSERT_EQ(procmap->query.vma_start, (unsigned long)ptr);
> >+	ASSERT_EQ(procmap->query.vma_end, (unsigned long)ptr + 9 * page_size);
> >+}
> >+
> >+TEST_F(merge, mprotect_faulted_left_unfaulted_right)
> >+{
> >+	unsigned int page_size = self->page_size;
> >+	char *carveout = self->carveout;
> >+	struct procmap_fd *procmap = &self->procmap;
> >+	char *ptr;
> >+
> >+	/*
> >+	 * |-----------------------|
> >+	 * |       unfaulted       |
> >+	 * |-----------------------|
> >+	 */
> >+	ptr = mmap(&carveout[2 * page_size], 9 * page_size, PROT_READ | PROT_WRITE,
> >+		   MAP_ANON | MAP_PRIVATE | MAP_FIXED | MAP_NORESERVE, -1, 0);
> >+	ASSERT_NE(ptr, MAP_FAILED);
> >+	/*
> >+	 * Now make the last 3 pages read-only, splitting the VMA:
> >+	 *
> >+	 *             RW               RO
> >+	 * |-----------------------|-----------|
> >+	 * |       unfaulted       | unfaulted |
> >+	 * |-----------------------|-----------|
> >+	 */
> >+	ASSERT_EQ(mprotect(&ptr[6 * page_size], 3 * page_size, PROT_READ), 0);
> >+	/*
> >+	 * Fault in the first of the first 6 pages so it gets an anon_vma and
> >+	 * thus the whole VMA becomes 'faulted':
> >+	 *
> >+	 *             RW               RO
> >+	 * |-----------------------|-----------|
> >+	 * |       unfaulted       | unfaulted |
>                    ^^^
>
> According to your previous comment convention, the comment here describe the
> result after ptr[0] = 'x'.
>
> faulted is the correct description here?

My 'previous comment convention'? What? You mean my describing what
happens?

Yes this is incorrect, this should read 'faulted' in the RW section. I will
fix if I respin.

>
> >+	 * |-----------------------|-----------|
> >+	 */
> >+	ptr[0] = 'x';
> >+	/*
> >+	 * Now make the first 3 pages read-only, splitting the VMA:
> >+	 *
> >+	 *      RO          RW          RO
> >+	 * |-----------|-----------|-----------|
> >+	 * |  faulted  |  faulted  | unfaulted |
> >+	 * |-----------|-----------|-----------|
> >+	 */
> >+	ASSERT_EQ(mprotect(ptr, 3 * page_size, PROT_READ), 0);
> >+	/*
> >+	 * Now mprotect() the RW region read-only, we should merge:
> >+	 *
> >+	 *             RO
> >+	 * |-----------------------|
> >+	 * |        faulted        |
> >+	 * |-----------------------|
> >+	 */
> >+	ASSERT_EQ(mprotect(&ptr[3 * page_size], 3 * page_size, PROT_READ), 0);
> >+
> >+	/* Assert that the merge succeeded using PROCMAP_QUERY. */
> >+	ASSERT_TRUE(find_vma_procmap(procmap, ptr));
> >+	ASSERT_EQ(procmap->query.vma_start, (unsigned long)ptr);
> >+	ASSERT_EQ(procmap->query.vma_end, (unsigned long)ptr + 9 * page_size);
> >+}
> >+
> >+TEST_F(merge, mprotect_unfaulted_left_faulted_right)
> >+{
> >+	unsigned int page_size = self->page_size;
> >+	char *carveout = self->carveout;
> >+	struct procmap_fd *procmap = &self->procmap;
> >+	char *ptr;
> >+
> >+	/*
> >+	 * |-----------------------|
> >+	 * |       unfaulted       |
> >+	 * |-----------------------|
> >+	 */
> >+	ptr = mmap(&carveout[2 * page_size], 9 * page_size, PROT_READ | PROT_WRITE,
> >+		   MAP_ANON | MAP_PRIVATE | MAP_FIXED | MAP_NORESERVE, -1, 0);
> >+	ASSERT_NE(ptr, MAP_FAILED);
> >+	/*
> >+	 * Now make the first 3 pages read-only, splitting the VMA:
> >+	 *
> >+	 *      RO                RW
> >+	 * |-----------|-----------------------|
> >+	 * | unfaulted |       unfaulted       |
> >+	 * |-----------|-----------------------|
> >+	 */
> >+	ASSERT_EQ(mprotect(ptr, 3 * page_size, PROT_READ), 0);
> >+	/*
> >+	 * FAult in the first of the last 6 pages so it gets an anon_vma and
>             ^
>
> s/A/a/

Right, I'll fix that if I respin.

>
> >+	 * thus the whole VMA becomes 'faulted':
> >+	 *
> >+	 *      RO                RW
> >+	 * |-----------|-----------------------|
> >+	 * | unfaulted |        faulted        |
> >+	 * |-----------|-----------------------|
> >+	 */
> >+	ptr[3 * page_size] = 'x';
> >+	/*
> >+	 * Now make the last 3 pages read-only, splitting the VMA:
> >+	 *
> >+	 *      RO          RW          RO
> >+	 * |-----------|-----------|-----------|
> >+	 * | unfaulted |  faulted  |  faulted  |
> >+	 * |-----------|-----------|-----------|
> >+	 */
> >+	ASSERT_EQ(mprotect(&ptr[6 * page_size], 3 * page_size, PROT_READ), 0);
> >+	/*
> >+	 * Now mprotect() the RW region read-only, we should merge:
> >+	 *
> >+	 *             RO
> >+	 * |-----------------------|
> >+	 * |        faulted        |
> >+	 * |-----------------------|
> >+	 */
> >+	ASSERT_EQ(mprotect(&ptr[3 * page_size], 3 * page_size, PROT_READ), 0);
> >+
> >+	/* Assert that the merge succeeded using PROCMAP_QUERY. */
> >+	ASSERT_TRUE(find_vma_procmap(procmap, ptr));
> >+	ASSERT_EQ(procmap->query.vma_start, (unsigned long)ptr);
> >+	ASSERT_EQ(procmap->query.vma_end, (unsigned long)ptr + 9 * page_size);
> >+}
> >+
> >+TEST_F(merge, forked_target_vma)
> >+{
> >+	unsigned int page_size = self->page_size;
> >+	char *carveout = self->carveout;
> >+	struct procmap_fd *procmap = &self->procmap;
> >+	pid_t pid;
> >+	char *ptr, *ptr2;
> >+	int i;
> >+
> >+	/*
> >+	 * |-----------|
> >+	 * | unfaulted |
> >+	 * |-----------|
> >+	 */
> >+	ptr = mmap(&carveout[page_size], 5 * page_size, PROT_READ | PROT_WRITE,
> >+		   MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
> >+	ASSERT_NE(ptr, MAP_FAILED);
> >+
> >+	/*
> >+	 * Fault in process.
> >+	 *
> >+	 * |-----------|
> >+	 * |  faulted  |
> >+	 * |-----------|
> >+	 */
> >+	ptr[0] = 'x';
> >+
> >+	pid = fork();
> >+	ASSERT_NE(pid, -1);
> >+
> >+	if (pid != 0) {
> >+		wait(NULL);
> >+		return;
> >+	}
> >+
> >+	/* Child process below: */
> >+
> >+	/* Reopen for child. */
> >+	ASSERT_EQ(close_procmap(&self->procmap), 0);
> >+	ASSERT_EQ(open_self_procmap(&self->procmap), 0);
> >+
> >+	/* unCOWing everything does not cause the AVC to go away. */
>            ^^^
>
> Before ptr[i] = 'x', we have unCOWed pages in vma. What we are doing here is
> COWing, right?

Nope, it's the other way round, as commented. A 'CoW' page is one marked
for copy-on-write right? we now make it just a normal mapping by writing to
it.

>
> >+	for (i = 0; i < 5 * page_size; i += page_size)
> >+		ptr[i] = 'x';
> >+
> >+	/*
> >+	 * Map in adjacent VMA in child.
> >+	 *
> >+	 *     forked
> >+	 * |-----------|-----------|
> >+	 * |  faulted  | unfaulted |
> >+	 * |-----------|-----------|
> >+	 *      ptr         ptr2
> >+	 */
> >+	ptr2 = mmap(&ptr[5 * page_size], 5 * page_size, PROT_READ | PROT_WRITE,
> >+		   MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
> >+	ASSERT_NE(ptr2, MAP_FAILED);
> >+
> >+	/* Make sure not merged. */
> >+	ASSERT_TRUE(find_vma_procmap(procmap, ptr));
> >+	ASSERT_EQ(procmap->query.vma_start, (unsigned long)ptr);
> >+	ASSERT_EQ(procmap->query.vma_end, (unsigned long)ptr + 5 * page_size);
> >+}
> >+
> >+TEST_F(merge, forked_source_vma)
> >+{
> >+	unsigned int page_size = self->page_size;
> >+	char *carveout = self->carveout;
> >+	struct procmap_fd *procmap = &self->procmap;
> >+	pid_t pid;
> >+	char *ptr, *ptr2;
> >+	int i;
> >+
> >+	/*
> >+	 * |............|-----------|
> >+	 * | <unmapped> | unfaulted |
> >+	 * |............|-----------|
>
> I am not sure "unmapped" is correct here. The range has already been mapped by
> FIXTURE_SETUP(merge).

This is pointless and actually misleading pedantry.

For the purposes of what we are doing here, this is unmapped. Do you truly
think mentioning a PROT_NONE mapping here would be useful, meaningful, or
add anything but noise?

>
> >+	 */
> >+	ptr = mmap(&carveout[page_size], 5 * page_size, PROT_READ | PROT_WRITE,
> >+		   MAP_ANON | MAP_PRIVATE | MAP_FIXED | MAP_NORESERVE, -1, 0);
> >+	ASSERT_NE(ptr, MAP_FAILED);
> >+
> >+	/*
> >+	 * Fault in process.
> >+	 *
> >+	 * |............||-----------|
> >+	 * | <unmapped> ||  faulted  |
> >+	 * |............||-----------|
>                          ^
>
> Extra line here?

Eh? I don't understand what you mean... you mean an extra '-'? This is to
fit both unfaulted/faulted in the same size SACII 'VMA', a convention I've
kept (hopefully) consistently...

>
> >+	 */
> >+	ptr[0] = 'x';
> >+
> >+	pid = fork();
> >+	ASSERT_NE(pid, -1);
> >+
> >+	if (pid != 0) {
> >+		wait(NULL);
> >+		return;
> >+	}
> >+
> >+	/* Child process below: */
> >+
> >+	/* Reopen for child. */
> >+	ASSERT_EQ(close_procmap(&self->procmap), 0);
> >+	ASSERT_EQ(open_self_procmap(&self->procmap), 0);
> >+
> >+	/* unCOWing everything does not cause the AVC to go away. */
>
> Same as above.

And you're equally wrong here.

I appreciate it's confusing and perhaps a poor way of expressing it, but
I'm not sure there's a gloriously wonderful means of doing so that will
bring clarity to everybody, as is the nature of mm. I do my best.

>
> >+	for (i = 0; i < 5 * page_size; i += page_size)
> >+		ptr[i] = 'x';
> >+
> >+	/*
> >+	 * Map in adjacent VMA in child, ptr2 before ptr, but incompatible.
> >+	 *
> >+	 *      RWX      forked RW
> >+	 * |-----------|-----------|
> >+	 * | unfaulted |  faulted  |
> >+	 * |-----------|-----------|
> >+	 *      ptr2        ptr
> >+	 */
> >+	ptr2 = mmap(&carveout[6 * page_size], 5 * page_size, PROT_READ | PROT_WRITE | PROT_EXEC,
> >+		   MAP_ANON | MAP_PRIVATE | MAP_FIXED | MAP_NORESERVE, -1, 0);
> >+	ASSERT_NE(ptr2, MAP_FAILED);
> >+
>
> I think pt2 is after ptr. Do I miss something?

Yup, didn't update the comments but clearly updated the method. I'll update
if there's a respin.

>
> >+
> >+	/* Make sure not merged. */
> >+	ASSERT_TRUE(find_vma_procmap(procmap, ptr2));
> >+	ASSERT_EQ(procmap->query.vma_start, (unsigned long)ptr2);
> >+	ASSERT_EQ(procmap->query.vma_end, (unsigned long)ptr2 + 5 * page_size);
> >+
> >+	/*
> >+	 * Now mprotect forked region to RWX so it becomes the source for the
> >+	 * merge to unfaulted region:
> >+	 *
> >+	 *      RWX      forked RWX
> >+	 * |-----------|-----------|
> >+	 * | unfaulted |  faulted  |
> >+	 * |-----------|-----------|
> >+	 *      ptr2        ptr
> >+	 */
> >+	ASSERT_EQ(mprotect(ptr, 5 * page_size, PROT_READ | PROT_WRITE | PROT_EXEC), 0);
> >+	/* Again, make sure not merged. */
> >+	ASSERT_TRUE(find_vma_procmap(procmap, ptr2));
> >+	ASSERT_EQ(procmap->query.vma_start, (unsigned long)ptr2);
> >+	ASSERT_EQ(procmap->query.vma_end, (unsigned long)ptr2 + 5 * page_size);
> >+}
> >+
> >+TEST_HARNESS_MAIN
> >diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
> >index 9aff33b10999..0b2f8bb91433 100755
> >--- a/tools/testing/selftests/mm/run_vmtests.sh
> >+++ b/tools/testing/selftests/mm/run_vmtests.sh
> >@@ -421,6 +421,8 @@ CATEGORY="madv_guard" run_test ./guard-regions
> > # MADV_POPULATE_READ and MADV_POPULATE_WRITE tests
> > CATEGORY="madv_populate" run_test ./madv_populate
> >
> >+CATEGORY="vma_merge" run_test ./merge
> >+
>
> ./run_vmtests.sh -h would show a list of categories.
>
> How about add the new category "vma_merge" into the list.

Probably unintended but this sounds pretty rude, especially when you are
performing unrequested, rather pedantic, 'drive-by' review like this.

A polite way of putting it would be 'perhaps additionally update the usage
to add vma_merge to the list?'.

Again, this is not very important, sure if I respin I'll do it.

>
> > if [ -x ./memfd_secret ]
> > then
> > (echo 0 > /proc/sys/kernel/yama/ptrace_scope 2>&1) | tap_prefix
> >--
> >2.48.1
> >
>
> --
> Wei Yang
> Help you, Help me