Add test for partial mremap on THP which exercises move_page_tables(). This verifies that partial mremap correctly splits the PMD, moves only the requested page, and preserves data integrity in both the moved region and the original mapping.
Signed-off-by: Usama Arif <[email protected]> --- .../testing/selftests/mm/thp_pmd_split_test.c | 50 +++++++++++++++++++ 1 file changed, 50 insertions(+) diff --git a/tools/testing/selftests/mm/thp_pmd_split_test.c b/tools/testing/selftests/mm/thp_pmd_split_test.c index 3c9f05457efec..1f29296759a5b 100644 --- a/tools/testing/selftests/mm/thp_pmd_split_test.c +++ b/tools/testing/selftests/mm/thp_pmd_split_test.c @@ -203,4 +203,54 @@ TEST_F(thp_pmd_split, partial_mlock) self->split_pmd_failed_before); } +/* + * Partial mremap (move_page_tables) + * + * Tests that partial mremap of a THP correctly splits the PMD and + * moves only the requested portion. This exercises move_page_tables() + * which now handles split failures. + */ +TEST_F(thp_pmd_split, partial_mremap) +{ + void *new_addr; + unsigned long *ptr = (unsigned long *)self->aligned; + unsigned long *new_ptr; + unsigned long pattern = 0xABCDUL; + int ret; + + ret = allocate_thp(self->aligned, self->pmdsize); + if (ret) + SKIP(return, "Failed to allocate THP"); + + /* Write pattern to the page we'll move */ + ptr[self->pagesize / sizeof(unsigned long)] = pattern; + + /* Also write to first and last page to verify they stay intact */ + ptr[0] = 0x1234UL; + ptr[(self->pmdsize - self->pagesize) / sizeof(unsigned long)] = 0x4567UL; + + /* Partial mremap - move one base page from the THP */ + new_addr = mremap((char *)self->aligned + self->pagesize, self->pagesize, + self->pagesize, MREMAP_MAYMOVE); + if (new_addr == MAP_FAILED) { + if (errno == ENOMEM) + SKIP(return, "mremap failed with ENOMEM"); + ASSERT_NE(new_addr, MAP_FAILED); + } + + /* Verify data was moved correctly */ + new_ptr = (unsigned long *)new_addr; + ASSERT_EQ(new_ptr[0], pattern); + + /* Verify surrounding data is intact */ + ASSERT_EQ(ptr[0], 0x1234UL); + ASSERT_EQ(ptr[(self->pmdsize - self->pagesize) / sizeof(unsigned long)], 0x4567UL); + + /* Cleanup the moved page */ + munmap(new_addr, self->pagesize); + + log_and_check_pmd_split(_metadata, self->split_pmd_before, + self->split_pmd_failed_before); +} + TEST_HARNESS_MAIN -- 2.47.3
