MREMAP_DONTUNMAP moves a mapping's page tables to a new address while leaving the source mapping in place. Check that mlock accounting charges the page only once after the remap.
Add a test to mremap_dontunmap that verifies mlock charges one page and that MREMAP_DONTUNMAP does not increase VmLck again. Skip the test when mlock is unavailable. Signed-off-by: Sahaj Chaudhari <[email protected]> --- tools/testing/selftests/mm/mremap_dontunmap.c | 92 ++++++++++++++++++- 1 file changed, 91 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/mm/mremap_dontunmap.c b/tools/testing/selftests/mm/mremap_dontunmap.c index 96ba537facf7..e4b0e1868a6f 100644 --- a/tools/testing/selftests/mm/mremap_dontunmap.c +++ b/tools/testing/selftests/mm/mremap_dontunmap.c @@ -90,6 +90,26 @@ static int check_region_contains_byte(void *addr, unsigned long size, char byte) return 0; } +static int read_vmlck(unsigned long *vmlck) +{ + char line[128]; + FILE *status = fopen("/proc/self/status", "r"); + + if (!status) + return -1; + + while (fgets(line, sizeof(line), status)) { + if (sscanf(line, "VmLck: %lu kB", vmlck) == 1) { + fclose(status); + return 0; + } + } + + fclose(status); + errno = EINVAL; + return -1; +} + // this test validates that MREMAP_DONTUNMAP moves the pagetables while leaving // the source mapping mapped. static void mremap_dontunmap_simple() @@ -125,6 +145,75 @@ static void mremap_dontunmap_simple() ksft_test_result_pass("%s\n", __func__); } +static void mremap_dontunmap_mlock_accounting(void) +{ + unsigned long before, after_mlock, after_remap; + char message[128]; + char *source, *dest = MAP_FAILED; + int failed = 0; + int err; + + source = mmap(NULL, page_size, PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); + if (source == MAP_FAILED) + ksft_exit_fail_perror("mmap"); + if (read_vmlck(&before)) + ksft_exit_fail_perror("read VmLck"); + + if (mlock(source, page_size)) { + err = errno; + if (munmap(source, page_size)) + ksft_exit_fail_perror("munmap"); + if (err == EPERM || err == ENOMEM) { + ksft_test_result_skip("%s: mlock unavailable\n", __func__); + return; + } + errno = err; + ksft_exit_fail_perror("mlock"); + } + + if (read_vmlck(&after_mlock)) + ksft_exit_fail_perror("read VmLck after mlock"); + if (after_mlock != before + page_size / 1024) { + snprintf(message, sizeof(message), + "mlock changed VmLck from %lu to %lu kB", before, + after_mlock); + failed = 1; + goto out; + } + + dest = mremap(source, page_size, page_size, + MREMAP_DONTUNMAP | MREMAP_MAYMOVE, NULL); + if (dest == MAP_FAILED) + ksft_exit_fail_perror("mremap"); + if (read_vmlck(&after_remap)) + ksft_exit_fail_perror("read VmLck after mremap"); + + if (after_remap != after_mlock) { + snprintf(message, sizeof(message), + "VmLck changed from %lu to %lu kB", after_mlock, + after_remap); + failed = 1; + } + +out: + if (dest != MAP_FAILED) { + if (munlock(dest, page_size)) + ksft_exit_fail_perror("munlock destination"); + if (munmap(dest, page_size)) + ksft_exit_fail_perror("munmap destination"); + } + if (munlock(source, page_size)) + ksft_exit_fail_perror("munlock source"); + if (munmap(source, page_size)) + ksft_exit_fail_perror("munmap source"); + + if (failed) + ksft_test_result_fail("%s\n", message); + else + ksft_test_result_pass("MREMAP_DONTUNMAP preserves VmLck accounting\n"); +} + // This test validates that MREMAP_DONTUNMAP on a shared mapping works as expected. static void mremap_dontunmap_simple_shmem() { @@ -348,7 +437,7 @@ int main(void) ksft_finished(); } - ksft_set_plan(5); + ksft_set_plan(6); // Keep a page sized buffer around for when we need it. page_buffer = @@ -361,6 +450,7 @@ int main(void) mremap_dontunmap_simple_fixed(); mremap_dontunmap_partial_mapping(); mremap_dontunmap_partial_mapping_overwrite(); + mremap_dontunmap_mlock_accounting(); BUG_ON(munmap(page_buffer, page_size) == -1, "unable to unmap page buffer");
