selftests/vm: anon_cow: hugetlb tests

Let's run all existing test cases with all hugetlb sizes we're able to
detect.

Note that some tests cases still fail. This will, for example, be fixed
once vmsplice properly uses FOLL_PIN instead of FOLL_GET for pinning.
With 2 MiB and 1 GiB hugetlb on x86_64, the expected failures are:

 # [RUN] vmsplice() + unmap in child ... with hugetlb (2048 kB)
 not ok 23 No leak from parent into child
 # [RUN] vmsplice() + unmap in child ... with hugetlb (1048576 kB)
 not ok 24 No leak from parent into child
 # [RUN] vmsplice() before fork(), unmap in parent after fork() ... with hugetlb (2048 kB)
 not ok 35 No leak from child into parent
 # [RUN] vmsplice() before fork(), unmap in parent after fork() ... with hugetlb (1048576 kB)
 not ok 36 No leak from child into parent
 # [RUN] vmsplice() + unmap in parent after fork() ... with hugetlb (2048 kB)
 not ok 47 No leak from child into parent
 # [RUN] vmsplice() + unmap in parent after fork() ... with hugetlb (1048576 kB)
 not ok 48 No leak from child into parent

Link: https://lkml.kernel.org/r/20220927110120.106906-5-david@redhat.comSigned-off-by: David Hildenbrand <david@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christoph von Recklinghausen <crecklin@redhat.com>
Cc: Don Dutile <ddutile@redhat.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nadav Amit <namit@vmware.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

tools/testing/selftests/vm/anon_cow.c

@@ -25,6 +25,8 @@
 static size_t pagesize;
 static int pagemap_fd;
 static size_t thpsize;
+static int nr_hugetlbsizes;
+static size_t hugetlbsizes[10];
 
 static void detect_thpsize(void)
 {
@@ -54,6 +56,31 @@ static void detect_thpsize(void)
 	close(fd);
 }
 
+static void detect_hugetlbsizes(void)
+{
+	DIR *dir = opendir("/sys/kernel/mm/hugepages/");
+
+	if (!dir)
+		return;
+
+	while (nr_hugetlbsizes < ARRAY_SIZE(hugetlbsizes)) {
+		struct dirent *entry = readdir(dir);
+		size_t kb;
+
+		if (!entry)
+			break;
+		if (entry->d_type != DT_DIR)
+			continue;
+		if (sscanf(entry->d_name, "hugepages-%zukB", &kb) != 1)
+			continue;
+		hugetlbsizes[nr_hugetlbsizes] = kb * 1024;
+		nr_hugetlbsizes++;
+		ksft_print_msg("[INFO] detected hugetlb size: %zu KiB\n",
+			       kb);
+	}
+	closedir(dir);
+}
+
 static bool range_is_swapped(void *addr, size_t size)
 {
 	for (; size; addr += pagesize, size -= pagesize)
@@ -556,6 +583,41 @@ static void run_with_partial_shared_thp(test_fn fn, const char *desc)
 	do_run_with_thp(fn, THP_RUN_PARTIAL_SHARED);
 }
 
+static void run_with_hugetlb(test_fn fn, const char *desc, size_t hugetlbsize)
+{
+	int flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB;
+	char *mem, *dummy;
+
+	ksft_print_msg("[RUN] %s ... with hugetlb (%zu kB)\n", desc,
+		       hugetlbsize / 1024);
+
+	flags |= __builtin_ctzll(hugetlbsize) << MAP_HUGE_SHIFT;
+
+	mem = mmap(NULL, hugetlbsize, PROT_READ | PROT_WRITE, flags, -1, 0);
+	if (mem == MAP_FAILED) {
+		ksft_test_result_skip("need more free huge pages\n");
+		return;
+	}
+
+	/* Populate an huge page. */
+	memset(mem, 0, hugetlbsize);
+
+	/*
+	 * We need a total of two hugetlb pages to handle COW/unsharing
+	 * properly, otherwise we might get zapped by a SIGBUS.
+	 */
+	dummy = mmap(NULL, hugetlbsize, PROT_READ | PROT_WRITE, flags, -1, 0);
+	if (dummy == MAP_FAILED) {
+		ksft_test_result_skip("need more free huge pages\n");
+		goto munmap;
+	}
+	munmap(dummy, hugetlbsize);
+
+	fn(mem, hugetlbsize);
+munmap:
+	munmap(mem, hugetlbsize);
+}
+
 struct test_case {
 	const char *desc;
 	test_fn fn;
@@ -602,6 +664,8 @@ static const struct test_case test_cases[] = {
 
 static void run_test_case(struct test_case const *test_case)
 {
+	int i;
+
 	run_with_base_page(test_case->fn, test_case->desc);
 	run_with_base_page_swap(test_case->fn, test_case->desc);
 	if (thpsize) {
@@ -614,6 +678,9 @@ static void run_test_case(struct test_case const *test_case)
 		run_with_partial_mremap_thp(test_case->fn, test_case->desc);
 		run_with_partial_shared_thp(test_case->fn, test_case->desc);
 	}
+	for (i = 0; i < nr_hugetlbsizes; i++)
+		run_with_hugetlb(test_case->fn, test_case->desc,
+				 hugetlbsizes[i]);
 }
 
 static void run_test_cases(void)
@@ -626,7 +693,7 @@ static void run_test_cases(void)
 
 static int tests_per_test_case(void)
 {
-	int tests = 2;
+	int tests = 2 + nr_hugetlbsizes;
 
 	if (thpsize)
 		tests += 8;
@@ -640,6 +707,7 @@ int main(int argc, char **argv)
 
 	pagesize = getpagesize();
 	detect_thpsize();
+	detect_hugetlbsizes();
 
 	ksft_print_header();
 	ksft_set_plan(nr_test_cases * tests_per_test_case());