diff mbox series

[RFC,6/7] tools/testing/selftests: add MREMAP_RELOCATE_ANON merge test cases

Message ID 8b82838696e93d97161af4f62f9f01dc9981ec7f.1742478846.git.lorenzo.stoakes@oracle.com (mailing list archive)
State New
Headers show
Series mm/mremap: introduce more mergeable mremap via MREMAP_RELOCATE_ANON | expand

Commit Message

Lorenzo Stoakes March 21, 2025, 9:54 p.m. UTC 
Add test cases to the mm self test asserting that the merge cases which the
newly introduced MREMAP[_MUST]_RELOCATE_ANON results in merges occurring as
expected, which otherwise without it would not succeed.

This extends the newly introduced VMA merge self tests for these cases and
exhaustively attempts each merge case, asserting expected behaviour.

We use the MREMAP_MUST_RELOCATE_ANON variant to ensure that, should the
anon relocate fail, we observe an error, as quietly demoting the move to
non-relocate anon would cause unusual test failures.

We carefully document each case to make clear what we are testing.

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
---
 tools/testing/selftests/mm/merge.c | 730 +++++++++++++++++++++++++++++
 1 file changed, 730 insertions(+)
diff mbox series

Patch

diff --git a/tools/testing/selftests/mm/merge.c b/tools/testing/selftests/mm/merge.c
index 7c4f3f93c30d..bd1b82665348 100644
--- a/tools/testing/selftests/mm/merge.c
+++ b/tools/testing/selftests/mm/merge.c
@@ -1055,4 +1055,734 @@  TEST_F(merge, mremap_correct_placed_faulted)
 	ASSERT_EQ(procmap->query.vma_end, (unsigned long)ptr + 15 * page_size);
 }
 
+TEST_F(merge, mremap_relocate_anon_faulted_after_unfaulted)
+{
+	unsigned int page_size = self->page_size;
+	char *carveout = self->carveout;
+	struct procmap_fd *procmap = &self->procmap;
+	char *ptr, *ptr2;
+
+	/*
+	 * Map two distinct areas:
+	 *
+	 * |-----------|  |-----------|
+	 * | unfaulted |  | unfaulted |
+	 * |-----------|  |-----------|
+	 *      ptr            ptr2
+	 */
+	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);
+	ptr2 = mmap(&carveout[7 * page_size], 5 * page_size, PROT_READ | PROT_WRITE,
+		    MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
+	ASSERT_NE(ptr2, MAP_FAILED);
+
+	/*
+	 * Offset ptr2 further away. Note we don't have to use
+	 * MREMAP_RELOCATE_ANON yet.
+	 */
+	ptr2 = sys_mremap(ptr2, 5 * page_size, 5 * page_size,
+			  MREMAP_MAYMOVE | MREMAP_FIXED, ptr2 + page_size * 1000);
+	ASSERT_NE(ptr2, MAP_FAILED);
+
+	/*
+	 * Fault ptr2 in:
+	 *                \
+	 * |-----------|  /  |-----------|
+	 * | unfaulted |  \  |  faulted  |
+	 * |-----------|  /  |-----------|
+	 *      ptr       \       ptr2
+	 */
+	ptr2[0] = 'x';
+
+	/*
+	 * Move ptr2 after ptr, using MREMAP_MUST_RELOCATE_ANON:
+	 *
+	 * |-----------|-----------|
+	 * | unfaulted |  faulted  |
+	 * |-----------|-----------|
+	 *      ptr         ptr2
+	 *
+	 * It should merge:
+	 *
+	 * |-----------------------|
+	 * |        faulted        |
+	 * |-----------------------|
+	 */
+	ptr2 = sys_mremap(ptr2, 5 * page_size, 5 * page_size,
+			  MREMAP_MAYMOVE | MREMAP_FIXED | MREMAP_MUST_RELOCATE_ANON,
+			  &ptr[5 * page_size]);
+	ASSERT_NE(ptr2, MAP_FAILED);
+
+	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, mremap_relocate_anon_faulted_before_unfaulted)
+{
+	unsigned int page_size = self->page_size;
+	char *carveout = self->carveout;
+	struct procmap_fd *procmap = &self->procmap;
+	char *ptr, *ptr2;
+
+	/*
+	 * Map two distinct areas:
+	 *
+	 * |-----------|  |-----------|
+	 * | unfaulted |  | unfaulted |
+	 * |-----------|  |-----------|
+	 *      ptr            ptr2
+	 */
+	ptr = mmap(&carveout[6 * page_size], 5 * page_size, PROT_READ | PROT_WRITE,
+		   MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
+	ASSERT_NE(ptr, MAP_FAILED);
+	ptr2 = mmap(&carveout[12 * page_size], 5 * page_size, PROT_READ | PROT_WRITE,
+		    MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
+	ASSERT_NE(ptr2, MAP_FAILED);
+
+	/*
+	 * Offset ptr2 further away. Note we don't have to use
+	 * MREMAP_RELOCATE_ANON yet.
+	 */
+	ptr2 = sys_mremap(ptr2, 5 * page_size, 5 * page_size,
+			  MREMAP_MAYMOVE | MREMAP_FIXED, ptr2 + page_size * 1000);
+	ASSERT_NE(ptr2, MAP_FAILED);
+
+	/*
+	 * Fault ptr2 in:
+	 *                \
+	 * |-----------|  /  |-----------|
+	 * | unfaulted |  \  |  faulted  |
+	 * |-----------|  /  |-----------|
+	 *      ptr       \       ptr2
+	 */
+	ptr2[0] = 'x';
+
+	/*
+	 * Move ptr2 before ptr, using MREMAP_MUST_RELOCATE_ANON:
+	 *
+	 * |-----------|-----------|
+	 * |  faulted  | unfaulted |
+	 * |-----------|-----------|
+	 *      ptr2        ptr
+	 *
+	 * It should merge:
+	 *
+	 * |-----------------------|
+	 * |        faulted        |
+	 * |-----------------------|
+	 */
+	ptr2 = sys_mremap(ptr2, 5 * page_size, 5 * page_size,
+			  MREMAP_MAYMOVE | MREMAP_FIXED | MREMAP_MUST_RELOCATE_ANON,
+			  &carveout[page_size]);
+	ASSERT_NE(ptr2, MAP_FAILED);
+
+	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 + 10 * page_size);
+}
+
+TEST_F(merge, mremap_relocate_anon_faulted_between_unfaulted)
+{
+	unsigned int page_size = self->page_size;
+	char *carveout = self->carveout;
+	struct procmap_fd *procmap = &self->procmap;
+	char *ptr, *ptr2, *ptr3;
+
+	/*
+	 * Map three distinct areas:
+	 *
+	 * |-----------|  |-----------|  |-----------|
+	 * | unfaulted |  | unfaulted |  | unfaulted |
+	 * |-----------|  |-----------|  |-----------|
+	 *      ptr            ptr2           ptr3
+	 */
+	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);
+	ptr2 = mmap(&carveout[7 * page_size], 5 * page_size, PROT_READ | PROT_WRITE,
+		    MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
+	ASSERT_NE(ptr2, MAP_FAILED);
+	ptr3 = mmap(&carveout[14 * page_size], 5 * page_size, PROT_READ | PROT_WRITE,
+		    MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
+	ASSERT_NE(ptr3, MAP_FAILED);
+
+	/*
+	 * Offset ptr2 further away, and move ptr3 into position:
+	 *                                        \
+	 * |-----------|           |-----------|  /  |-----------|
+	 * | unfaulted |           | unfaulted |  \  | unfaulted |
+	 * |-----------|           |-----------|  /  |-----------|
+	 *      ptr                    ptr3       \      ptr2
+	 */
+	ptr2 = sys_mremap(ptr2, 5 * page_size, 5 * page_size,
+			  MREMAP_MAYMOVE | MREMAP_FIXED, ptr2 + page_size * 1000);
+	ASSERT_NE(ptr2, MAP_FAILED);
+	ptr3 = sys_mremap(ptr3, 5 * page_size, 5 * page_size,
+			  MREMAP_MAYMOVE | MREMAP_FIXED, ptr3 + page_size * 2000);
+	ASSERT_NE(ptr3, MAP_FAILED);
+	ptr3 = sys_mremap(ptr3, 5 * page_size, 5 * page_size,
+			  MREMAP_MAYMOVE | MREMAP_FIXED, &ptr[10 * page_size]);
+	ASSERT_NE(ptr3, MAP_FAILED);
+
+	/*
+	 * Fault in ptr2:
+	 *                                        \
+	 * |-----------|           |-----------|  /  |-----------|
+	 * | unfaulted |           | unfaulted |  \  |  faulted  |
+	 * |-----------|           |-----------|  /  |-----------|
+	 *      ptr                    ptr3       \      ptr2
+	 */
+	ptr2[0] = 'x';
+
+	/*
+	 * Move ptr2 between ptr, ptr3, using MREMAP_MUST_RELOCATE_ANON:
+	 *
+	 * |-----------|-----------|-----------|
+	 * | unfaulted |  faulted  | unfaulted |
+	 * |-----------|-----------|-----------|
+	 *
+	 * It should merge:
+	 *
+	 * |-----------------------------------|
+	 * |              faulted              |
+	 * |-----------------------------------|
+	 */
+	ptr2 = sys_mremap(ptr2, 5 * page_size, 5 * page_size,
+			  MREMAP_MAYMOVE | MREMAP_FIXED | MREMAP_MUST_RELOCATE_ANON,
+			  &ptr[5 * page_size]);
+	ASSERT_NE(ptr2, MAP_FAILED);
+
+	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 + 15 * page_size);
+}
+
+TEST_F(merge, mremap_relocate_anon_faulted_after_faulted)
+{
+	unsigned int page_size = self->page_size;
+	char *carveout = self->carveout;
+	struct procmap_fd *procmap = &self->procmap;
+	char *ptr, *ptr2;
+
+	/*
+	 * Map two distinct areas:
+	 *
+	 * |-----------|  |-----------|
+	 * | unfaulted |  | unfaulted |
+	 * |-----------|  |-----------|
+	 *      ptr            ptr2
+	 */
+	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);
+	ptr2 = mmap(&carveout[7 * page_size], 5 * page_size, PROT_READ | PROT_WRITE,
+		    MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
+	ASSERT_NE(ptr2, MAP_FAILED);
+
+	/*
+	 * Offset ptr2 further away. Note we don't have to use
+	 * MREMAP_RELOCATE_ANON yet.
+	 */
+	ptr2 = sys_mremap(ptr2, 5 * page_size, 5 * page_size,
+			  MREMAP_MAYMOVE | MREMAP_FIXED, ptr2 + page_size * 1000);
+	ASSERT_NE(ptr2, MAP_FAILED);
+
+	/*
+	 * Fault ptr and ptr2 in:
+	 *                \
+	 * |-----------|  /  |-----------|
+	 * |  faulted  |  \  |  faulted  |
+	 * |-----------|  /  |-----------|
+	 *      ptr       \       ptr2
+	 */
+	ptr[0] = 'x';
+	ptr2[0] = 'x';
+
+	/*
+	 * Move ptr2 after ptr, using MREMAP_MUST_RELOCATE_ANON:
+	 *
+	 * |-----------|-----------|
+	 * |  faulted  |  faulted  |
+	 * |-----------|-----------|
+	 *      ptr         ptr2
+	 *
+	 * It should merge:
+	 *
+	 * |-----------------------|
+	 * |        faulted        |
+	 * |-----------------------|
+	 */
+	ptr2 = sys_mremap(ptr2, 5 * page_size, 5 * page_size,
+			  MREMAP_MAYMOVE | MREMAP_FIXED | MREMAP_MUST_RELOCATE_ANON,
+			  &ptr[5 * page_size]);
+	ASSERT_NE(ptr2, MAP_FAILED);
+
+	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, mremap_relocate_anon_faulted_before_faulted)
+{
+	unsigned int page_size = self->page_size;
+	char *carveout = self->carveout;
+	struct procmap_fd *procmap = &self->procmap;
+	char *ptr, *ptr2;
+
+	/*
+	 * Map two distinct areas:
+	 *
+	 * |-----------|  |-----------|
+	 * | unfaulted |  | unfaulted |
+	 * |-----------|  |-----------|
+	 *      ptr            ptr2
+	 */
+	ptr = mmap(&carveout[6 * page_size], 5 * page_size, PROT_READ | PROT_WRITE,
+		   MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
+	ASSERT_NE(ptr, MAP_FAILED);
+	ptr2 = mmap(&carveout[12 * page_size], 5 * page_size, PROT_READ | PROT_WRITE,
+		    MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
+	ASSERT_NE(ptr2, MAP_FAILED);
+
+	/*
+	 * Offset ptr2 further away. Note we don't have to use
+	 * MREMAP_RELOCATE_ANON yet.
+	 */
+	ptr2 = sys_mremap(ptr2, 5 * page_size, 5 * page_size,
+			  MREMAP_MAYMOVE | MREMAP_FIXED, ptr2 + page_size * 1000);
+	ASSERT_NE(ptr2, MAP_FAILED);
+
+	/*
+	 * Fault ptr, ptr2 in:
+	 *                \
+	 * |-----------|  /  |-----------|
+	 * |  faulted  |  \  |  faulted  |
+	 * |-----------|  /  |-----------|
+	 *      ptr       \       ptr2
+	 */
+	ptr[0] = 'x';
+	ptr2[0] = 'x';
+
+	/*
+	 * Move ptr2 before ptr, using MREMAP_MUST_RELOCATE_ANON:
+	 *
+	 * |-----------|-----------|
+	 * |  faulted  |  faulted  |
+	 * |-----------|-----------|
+	 *      ptr2        ptr
+	 *
+	 * It should merge:
+	 *
+	 * |-----------------------|
+	 * |        faulted        |
+	 * |-----------------------|
+	 */
+	ptr2 = sys_mremap(ptr2, 5 * page_size, 5 * page_size,
+			  MREMAP_MAYMOVE | MREMAP_FIXED | MREMAP_MUST_RELOCATE_ANON,
+			  &carveout[page_size]);
+	ASSERT_NE(ptr2, MAP_FAILED);
+
+	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 + 10 * page_size);
+}
+
+TEST_F(merge, mremap_relocate_anon_faulted_between_faulted_unfaulted)
+{
+	unsigned int page_size = self->page_size;
+	char *carveout = self->carveout;
+	struct procmap_fd *procmap = &self->procmap;
+	char *ptr, *ptr2, *ptr3;
+
+	/*
+	 * Map three distinct areas:
+	 *
+	 * |-----------|  |-----------|  |-----------|
+	 * | unfaulted |  | unfaulted |  | unfaulted |
+	 * |-----------|  |-----------|  |-----------|
+	 *      ptr            ptr2           ptr3
+	 */
+	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);
+	ptr2 = mmap(&carveout[7 * page_size], 5 * page_size, PROT_READ | PROT_WRITE,
+		    MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
+	ASSERT_NE(ptr2, MAP_FAILED);
+	ptr3 = mmap(&carveout[14 * page_size], 5 * page_size, PROT_READ | PROT_WRITE,
+		    MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
+	ASSERT_NE(ptr3, MAP_FAILED);
+
+	/*
+	 * Offset ptr2 further away, and move ptr3 into position:
+	 *                                        \
+	 * |-----------|           |-----------|  /  |-----------|
+	 * | unfaulted |           | unfaulted |  \  | unfaulted |
+	 * |-----------|           |-----------|  /  |-----------|
+	 *      ptr                    ptr3       \      ptr2
+	 */
+	ptr2 = sys_mremap(ptr2, 5 * page_size, 5 * page_size,
+			  MREMAP_MAYMOVE | MREMAP_FIXED, ptr2 + page_size * 1000);
+	ASSERT_NE(ptr2, MAP_FAILED);
+	ptr3 = sys_mremap(ptr3, 5 * page_size, 5 * page_size,
+			  MREMAP_MAYMOVE | MREMAP_FIXED, ptr3 + page_size * 2000);
+	ASSERT_NE(ptr3, MAP_FAILED);
+	ptr3 = sys_mremap(ptr3, 5 * page_size, 5 * page_size,
+			  MREMAP_MAYMOVE | MREMAP_FIXED, &ptr[10 * page_size]);
+	ASSERT_NE(ptr3, MAP_FAILED);
+
+	/*
+	 * Fault in ptr, ptr2:
+	 *                                        \
+	 * |-----------|           |-----------|  /  |-----------|
+	 * |  faulted  |           | unfaulted |  \  |  faulted  |
+	 * |-----------|           |-----------|  /  |-----------|
+	 *      ptr                    ptr3       \      ptr2
+	 */
+	ptr[0] = 'x';
+	ptr2[0] = 'x';
+
+	/*
+	 * Move ptr2 between ptr, ptr3, using MREMAP_MUST_RELOCATE_ANON:
+	 *
+	 * |-----------|-----------|-----------|
+	 * |  faulted  |  faulted  | unfaulted |
+	 * |-----------|-----------|-----------|
+	 *
+	 * It should merge:
+	 *
+	 * |-----------------------------------|
+	 * |              faulted              |
+	 * |-----------------------------------|
+	 */
+	ptr2 = sys_mremap(ptr2, 5 * page_size, 5 * page_size,
+			  MREMAP_MAYMOVE | MREMAP_FIXED | MREMAP_MUST_RELOCATE_ANON,
+			  &ptr[5 * page_size]);
+	ASSERT_NE(ptr2, MAP_FAILED);
+
+	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 + 15 * page_size);
+}
+
+TEST_F(merge, mremap_relocate_anon_faulted_between_unfaulted_faulted)
+{
+	unsigned int page_size = self->page_size;
+	char *carveout = self->carveout;
+	struct procmap_fd *procmap = &self->procmap;
+	char *ptr, *ptr2, *ptr3;
+
+	/*
+	 * Map three distinct areas:
+	 *
+	 * |-----------|  |-----------|  |-----------|
+	 * | unfaulted |  | unfaulted |  | unfaulted |
+	 * |-----------|  |-----------|  |-----------|
+	 *      ptr            ptr2           ptr3
+	 */
+	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);
+	ptr2 = mmap(&carveout[7 * page_size], 5 * page_size, PROT_READ | PROT_WRITE,
+		    MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
+	ASSERT_NE(ptr2, MAP_FAILED);
+	ptr3 = mmap(&carveout[14 * page_size], 5 * page_size, PROT_READ | PROT_WRITE,
+		    MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
+	ASSERT_NE(ptr3, MAP_FAILED);
+
+	/*
+	 * Offset ptr2 further away, and move ptr3 into position:
+	 *                                        \
+	 * |-----------|           |-----------|  /  |-----------|
+	 * | unfaulted |           | unfaulted |  \  | unfaulted |
+	 * |-----------|           |-----------|  /  |-----------|
+	 *      ptr                    ptr3       \      ptr2
+	 */
+	ptr2 = sys_mremap(ptr2, 5 * page_size, 5 * page_size,
+			  MREMAP_MAYMOVE | MREMAP_FIXED, ptr2 + page_size * 1000);
+	ASSERT_NE(ptr2, MAP_FAILED);
+	ptr3 = sys_mremap(ptr3, 5 * page_size, 5 * page_size,
+			  MREMAP_MAYMOVE | MREMAP_FIXED, ptr3 + page_size * 2000);
+	ASSERT_NE(ptr3, MAP_FAILED);
+	ptr3 = sys_mremap(ptr3, 5 * page_size, 5 * page_size,
+			  MREMAP_MAYMOVE | MREMAP_FIXED, &ptr[10 * page_size]);
+	ASSERT_NE(ptr3, MAP_FAILED);
+
+	/*
+	 * Fault in ptr2, ptr3:
+	 *                                        \
+	 * |-----------|           |-----------|  /  |-----------|
+	 * | unfaulted |           |  faulted  |  \  |  faulted  |
+	 * |-----------|           |-----------|  /  |-----------|
+	 *      ptr                    ptr3       \      ptr2
+	 */
+	ptr2[0] = 'x';
+	ptr3[0] = 'x';
+
+	/*
+	 * Move ptr2 between ptr, ptr3, using MREMAP_MUST_RELOCATE_ANON:
+	 *
+	 * |-----------|-----------|-----------|
+	 * | unfaulted |  faulted  |  faulted  |
+	 * |-----------|-----------|-----------|
+	 *
+	 * It should merge:
+	 *
+	 * |-----------------------------------|
+	 * |              faulted              |
+	 * |-----------------------------------|
+	 */
+	ptr2 = sys_mremap(ptr2, 5 * page_size, 5 * page_size,
+			  MREMAP_MAYMOVE | MREMAP_FIXED | MREMAP_MUST_RELOCATE_ANON,
+			  &ptr[5 * page_size]);
+	ASSERT_NE(ptr2, MAP_FAILED);
+
+	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 + 15 * page_size);
+}
+
+TEST_F(merge, mremap_relocate_anon_faulted_between_faulted)
+{
+	unsigned int page_size = self->page_size;
+	char *carveout = self->carveout;
+	struct procmap_fd *procmap = &self->procmap;
+	char *ptr, *ptr2, *ptr3;
+
+	/*
+	 * Map three distinct areas:
+	 *
+	 * |-----------|  |-----------|  |-----------|
+	 * | unfaulted |  | unfaulted |  | unfaulted |
+	 * |-----------|  |-----------|  |-----------|
+	 *      ptr            ptr2           ptr3
+	 */
+	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);
+	ptr2 = mmap(&carveout[7 * page_size], 5 * page_size, PROT_READ | PROT_WRITE,
+		    MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
+	ASSERT_NE(ptr2, MAP_FAILED);
+	ptr3 = mmap(&carveout[14 * page_size], 5 * page_size, PROT_READ | PROT_WRITE,
+		    MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
+	ASSERT_NE(ptr3, MAP_FAILED);
+
+	/*
+	 * Offset ptr2 further away, and move ptr3 into position:
+	 *                                        \
+	 * |-----------|           |-----------|  /  |-----------|
+	 * | unfaulted |           | unfaulted |  \  | unfaulted |
+	 * |-----------|           |-----------|  /  |-----------|
+	 *      ptr                    ptr3       \      ptr2
+	 */
+	ptr2 = sys_mremap(ptr2, 5 * page_size, 5 * page_size,
+			  MREMAP_MAYMOVE | MREMAP_FIXED, ptr2 + page_size * 1000);
+	ASSERT_NE(ptr2, MAP_FAILED);
+	ptr3 = sys_mremap(ptr3, 5 * page_size, 5 * page_size,
+			  MREMAP_MAYMOVE | MREMAP_FIXED, ptr3 + page_size * 2000);
+	ASSERT_NE(ptr3, MAP_FAILED);
+	ptr3 = sys_mremap(ptr3, 5 * page_size, 5 * page_size,
+			  MREMAP_MAYMOVE | MREMAP_FIXED, &ptr[10 * page_size]);
+	ASSERT_NE(ptr3, MAP_FAILED);
+
+	/*
+	 * Fault in ptr, ptr2, ptr3:
+	 *                                        \
+	 * |-----------|           |-----------|  /  |-----------|
+	 * |  faulted  |           |  faulted  |  \  |  faulted  |
+	 * |-----------|           |-----------|  /  |-----------|
+	 *      ptr                    ptr3       \      ptr2
+	 */
+	ptr[0] = 'x';
+	ptr2[0] = 'x';
+	ptr3[0] = 'x';
+
+	/*
+	 * Move ptr2 between ptr, ptr3, using MREMAP_MUST_RELOCATE_ANON:
+	 *
+	 * |-----------|-----------|-----------|
+	 * |  faulted  |  faulted  |  faulted  |
+	 * |-----------|-----------|-----------|
+	 *
+	 * It should merge, but only the latter two VMAs:
+	 *
+	 * |-----------|-----------------------|
+	 * |  faulted  |        faulted        |
+	 * |-----------|-----------------------|
+	 */
+	ptr2 = sys_mremap(ptr2, 5 * page_size, 5 * page_size,
+			  MREMAP_MAYMOVE | MREMAP_FIXED | MREMAP_MUST_RELOCATE_ANON,
+			  &ptr[5 * page_size]);
+	ASSERT_NE(ptr2, MAP_FAILED);
+
+	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 + 10 * page_size);
+}
+
+TEST_F(merge, mremap_relocate_anon_faulted_between_correctly_placed_faulted)
+{
+	unsigned int page_size = self->page_size;
+	char *carveout = self->carveout;
+	struct procmap_fd *procmap = &self->procmap;
+	char *ptr, *ptr2;
+
+	/*
+	 * Map one larger area:
+	 *
+	 * |-----------------------------------|
+	 * |            unfaulted              |
+	 * |-----------------------------------|
+	 */
+	ptr = mmap(&carveout[page_size], 15 * page_size, PROT_READ | PROT_WRITE,
+		   MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
+	ASSERT_NE(ptr, MAP_FAILED);
+
+	/*
+	 * Fault in ptr:
+	 *
+	 * |-----------------------------------|
+	 * |              faulted              |
+	 * |-----------------------------------|
+	 */
+	ptr[0] = 'x';
+
+	/*
+	 * Unmap middle:
+	 *
+	 * |-----------|           |-----------|
+	 * |  faulted  |           |  faulted  |
+	 * |-----------|           |-----------|
+	 *
+	 * Now the faulted areas are compatible with each other (anon_vma the
+	 * same, vma->vm_pgoff equal to virtual page offset).
+	 */
+	ASSERT_EQ(munmap(&ptr[5 * page_size], 5 * page_size), 0);
+
+	/*
+	 * Map a new area, ptr2:
+	 *                                        \
+	 * |-----------|           |-----------|  /  |-----------|
+	 * |  faulted  |           |  faulted  |  \  | unfaulted |
+	 * |-----------|           |-----------|  /  |-----------|
+	 *      ptr                               \       ptr2
+	 */
+	ptr2 = mmap(&carveout[20 * page_size], 5 * page_size, PROT_READ | PROT_WRITE,
+		    MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
+	ASSERT_NE(ptr2, MAP_FAILED);
+
+	/*
+	 * Fault it in:
+	 *                                        \
+	 * |-----------|           |-----------|  /  |-----------|
+	 * |  faulted  |           |  faulted  |  \  |  faulted  |
+	 * |-----------|           |-----------|  /  |-----------|
+	 *      ptr                               \       ptr2
+	 */
+	ptr2[0] = 'x';
+
+	/*
+	 * Finally, move ptr2 into place, using MREMAP_MUST_RELOCATE_ANON:
+	 *
+	 * |-----------|-----------|-----------|
+	 * |  faulted  |  faulted  |  faulted  |
+	 * |-----------|-----------|-----------|
+	 *      ptr        ptr2         ptr3
+	 *
+	 * It should merge:
+	 *
+	 * |-----------------------------------|
+	 * |              faulted              |
+	 * |-----------------------------------|
+	 */
+	ptr2 = sys_mremap(ptr2, 5 * page_size, 5 * page_size,
+			  MREMAP_MAYMOVE | MREMAP_FIXED | MREMAP_MUST_RELOCATE_ANON,
+			  &ptr[5 * page_size]);
+	ASSERT_NE(ptr2, MAP_FAILED);
+
+	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 + 15 * page_size);
+}
+
+TEST_F(merge, mremap_relocate_anon_mprotect_faulted_faulted)
+{
+	unsigned int page_size = self->page_size;
+	char *carveout = self->carveout;
+	struct procmap_fd *procmap = &self->procmap;
+	char *ptr, *ptr2;
+
+
+	/*
+	 * Map two distinct areas:
+	 *
+	 * |-----------|  |-----------|
+	 * | unfaulted |  | unfaulted |
+	 * |-----------|  |-----------|
+	 *      ptr            ptr2
+	 */
+	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);
+	ptr2 = mmap(&carveout[12 * page_size], 5 * page_size, PROT_READ | PROT_WRITE,
+		    MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
+	ASSERT_NE(ptr2, MAP_FAILED);
+
+	/*
+	 * Fault in ptr, ptr2, mprotect() ptr2 read-only:
+	 *
+	 *      RW              RO
+	 * |-----------|  |-----------|
+	 * |  faulted  |  |  faulted  |
+	 * |-----------|  |-----------|
+	 *      ptr            ptr2
+	 */
+	ptr[0] = 'x';
+	ptr2[0] = 'x';
+	ASSERT_EQ(mprotect(ptr2, 5 * page_size, PROT_READ), 0);
+
+	/*
+	 * Move ptr2 next to ptr:
+	 *
+	 *      RW          RO
+	 * |-----------|-----------|
+	 * |  faulted  |  faulted  |
+	 * |-----------|-----------|
+	 *      ptr        ptr2
+	 */
+	ptr2 = sys_mremap(ptr2, 5 * page_size, 5 * page_size,
+			  MREMAP_MAYMOVE | MREMAP_FIXED | MREMAP_MUST_RELOCATE_ANON,
+			  &ptr[5 * page_size]);
+	ASSERT_NE(ptr2, MAP_FAILED);
+
+	/* No merge should happen. */
+	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);
+
+	/*
+	 * Now mremap ptr2 RW:
+	 *
+	 *      RW          RW
+	 * |-----------|-----------|
+	 * |  faulted  |  faulted  |
+	 * |-----------|-----------|
+	 *      ptr        ptr2
+	 *
+	 * This should result in a merge:
+	 *
+	 *            RW
+	 * |-----------------------|
+	 * |        faulted        |
+	 * |-----------------------|
+	 *            ptr
+	 */
+	ASSERT_EQ(mprotect(ptr2, 5 * page_size, PROT_READ | PROT_WRITE), 0);
+
+	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_HARNESS_MAIN