1 files changed, 678 insertions, 154 deletions

diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c
index 0e74635c8c3d..40799f3f0213 100644
--- a/tools/testing/selftests/mm/split_huge_page_test.c
+++ b/tools/testing/selftests/mm/split_huge_page_test.c
@@ -5,6 +5,7 @@
  */
 
 #define _GNU_SOURCE
+#include <assert.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdarg.h>
@@ -14,57 +15,259 @@
 #include <fcntl.h>
 #include <sys/mman.h>
 #include <sys/mount.h>
+#include <sys/param.h>
 #include <malloc.h>
 #include <stdbool.h>
+#include <time.h>
 #include "vm_util.h"
+#include "kselftest.h"
 
 uint64_t pagesize;
 unsigned int pageshift;
 uint64_t pmd_pagesize;
+unsigned int pmd_order;
+int *expected_orders;
 
 #define SPLIT_DEBUGFS "/sys/kernel/debug/split_huge_pages"
+#define SMAP_PATH "/proc/self/smaps"
 #define INPUT_MAX 80
 
-#define PID_FMT "%d,0x%lx,0x%lx"
-#define PATH_FMT "%s,0x%lx,0x%lx"
+#define PID_FMT "%d,0x%lx,0x%lx,%d"
+#define PID_FMT_OFFSET "%d,0x%lx,0x%lx,%d,%d"
+#define PATH_FMT "%s,0x%lx,0x%lx,%d"
 
-#define PFN_MASK     ((1UL<<55)-1)
-#define KPF_THP      (1UL<<22)
+const char *pagemap_proc = "/proc/self/pagemap";
+const char *kpageflags_proc = "/proc/kpageflags";
+int pagemap_fd;
+int kpageflags_fd;
 
-int is_backed_by_thp(char *vaddr, int pagemap_file, int kpageflags_file)
+static bool is_backed_by_folio(char *vaddr, int order, int pagemap_fd,
+		int kpageflags_fd)
 {
-	uint64_t paddr;
-	uint64_t page_flags;
+	const uint64_t folio_head_flags = KPF_THP | KPF_COMPOUND_HEAD;
+	const uint64_t folio_tail_flags = KPF_THP | KPF_COMPOUND_TAIL;
+	const unsigned long nr_pages = 1UL << order;
+	unsigned long pfn_head;
+	uint64_t pfn_flags;
+	unsigned long pfn;
+	unsigned long i;
+
+	pfn = pagemap_get_pfn(pagemap_fd, vaddr);
+
+	/* non present page */
+	if (pfn == -1UL)
+		return false;
+
+	if (pageflags_get(pfn, kpageflags_fd, &pfn_flags))
+		goto fail;
+
+	/* check for order-0 pages */
+	if (!order) {
+		if (pfn_flags & (folio_head_flags | folio_tail_flags))
+			return false;
+		return true;
+	}
+
+	/* non THP folio */
+	if (!(pfn_flags & KPF_THP))
+		return false;
+
+	pfn_head = pfn & ~(nr_pages - 1);
+
+	if (pageflags_get(pfn_head, kpageflags_fd, &pfn_flags))
+		goto fail;
+
+	/* head PFN has no compound_head flag set */
+	if ((pfn_flags & folio_head_flags) != folio_head_flags)
+		return false;
+
+	/* check all tail PFN flags */
+	for (i = 1; i < nr_pages; i++) {
+		if (pageflags_get(pfn_head + i, kpageflags_fd, &pfn_flags))
+			goto fail;
+		if ((pfn_flags & folio_tail_flags) != folio_tail_flags)
+			return false;
+	}
+
+	/*
+	 * check the PFN after this folio, but if its flags cannot be obtained,
+	 * assume this folio has the expected order
+	 */
+	if (pageflags_get(pfn_head + nr_pages, kpageflags_fd, &pfn_flags))
+		return true;
+
+	/* If we find another tail page, then the folio is larger. */
+	return (pfn_flags & folio_tail_flags) != folio_tail_flags;
+fail:
+	ksft_exit_fail_msg("Failed to get folio info\n");
+	return false;
+}
+
+static int vaddr_pageflags_get(char *vaddr, int pagemap_fd, int kpageflags_fd,
+		uint64_t *flags)
+{
+	unsigned long pfn;
+
+	pfn = pagemap_get_pfn(pagemap_fd, vaddr);
+
+	/* non-present PFN */
+	if (pfn == -1UL)
+		return 1;
 
-	if (pagemap_file) {
-		pread(pagemap_file, &paddr, sizeof(paddr),
-			((long)vaddr >> pageshift) * sizeof(paddr));
+	if (pageflags_get(pfn, kpageflags_fd, flags))
+		return -1;
+
+	return 0;
+}
+
+/*
+ * gather_after_split_folio_orders - scan through [vaddr_start, len) and record
+ * folio orders
+ *
+ * @vaddr_start: start vaddr
+ * @len: range length
+ * @pagemap_fd: file descriptor to /proc/<pid>/pagemap
+ * @kpageflags_fd: file descriptor to /proc/kpageflags
+ * @orders: output folio order array
+ * @nr_orders: folio order array size
+ *
+ * gather_after_split_folio_orders() scan through [vaddr_start, len) and check
+ * all folios within the range and record their orders. All order-0 pages will
+ * be recorded. Non-present vaddr is skipped.
+ *
+ * NOTE: the function is used to check folio orders after a split is performed,
+ * so it assumes [vaddr_start, len) fully maps to after-split folios within that
+ * range.
+ *
+ * Return: 0 - no error, -1 - unhandled cases
+ */
+static int gather_after_split_folio_orders(char *vaddr_start, size_t len,
+		int pagemap_fd, int kpageflags_fd, int orders[], int nr_orders)
+{
+	uint64_t page_flags = 0;
+	int cur_order = -1;
+	char *vaddr;
+
+	if (pagemap_fd == -1 || kpageflags_fd == -1)
+		return -1;
+	if (!orders)
+		return -1;
+	if (nr_orders <= 0)
+		return -1;
+
+	for (vaddr = vaddr_start; vaddr < vaddr_start + len;) {
+		char *next_folio_vaddr;
+		int status;
+
+		status = vaddr_pageflags_get(vaddr, pagemap_fd, kpageflags_fd,
+					&page_flags);
+		if (status < 0)
+			return -1;
+
+		/* skip non present vaddr */
+		if (status == 1) {
+			vaddr += psize();
+			continue;
+		}
+
+		/* all order-0 pages with possible false postive (non folio) */
+		if (!(page_flags & (KPF_COMPOUND_HEAD | KPF_COMPOUND_TAIL))) {
+			orders[0]++;
+			vaddr += psize();
+			continue;
+		}
+
+		/* skip non thp compound pages */
+		if (!(page_flags & KPF_THP)) {
+			vaddr += psize();
+			continue;
+		}
 
-		if (kpageflags_file) {
-			pread(kpageflags_file, &page_flags, sizeof(page_flags),
-				(paddr & PFN_MASK) * sizeof(page_flags));
+		/* vpn points to part of a THP at this point */
+		if (page_flags & KPF_COMPOUND_HEAD)
+			cur_order = 1;
+		else {
+			vaddr += psize();
+			continue;
+		}
 
-			return !!(page_flags & KPF_THP);
+		next_folio_vaddr = vaddr + (1UL << (cur_order + pshift()));
+
+		if (next_folio_vaddr >= vaddr_start + len)
+			break;
+
+		while ((status = vaddr_pageflags_get(next_folio_vaddr,
+						     pagemap_fd, kpageflags_fd,
+						     &page_flags)) >= 0) {
+			/*
+			 * non present vaddr, next compound head page, or
+			 * order-0 page
+			 */
+			if (status == 1 ||
+			    (page_flags & KPF_COMPOUND_HEAD) ||
+			    !(page_flags & (KPF_COMPOUND_HEAD | KPF_COMPOUND_TAIL))) {
+				if (cur_order < nr_orders) {
+					orders[cur_order]++;
+					cur_order = -1;
+					vaddr = next_folio_vaddr;
+				}
+				break;
+			}
+
+			cur_order++;
+			next_folio_vaddr = vaddr + (1UL << (cur_order + pshift()));
 		}
+
+		if (status < 0)
+			return status;
 	}
+	if (cur_order > 0 && cur_order < nr_orders)
+		orders[cur_order]++;
 	return 0;
 }
 
-static int write_file(const char *path, const char *buf, size_t buflen)
+static int check_after_split_folio_orders(char *vaddr_start, size_t len,
+		int pagemap_fd, int kpageflags_fd, int orders[], int nr_orders)
+{
+	int *vaddr_orders;
+	int status;
+	int i;
+
+	vaddr_orders = (int *)malloc(sizeof(int) * nr_orders);
+
+	if (!vaddr_orders)
+		ksft_exit_fail_msg("Cannot allocate memory for vaddr_orders");
+
+	memset(vaddr_orders, 0, sizeof(int) * nr_orders);
+	status = gather_after_split_folio_orders(vaddr_start, len, pagemap_fd,
+				     kpageflags_fd, vaddr_orders, nr_orders);
+	if (status)
+		ksft_exit_fail_msg("gather folio info failed\n");
+
+	for (i = 0; i < nr_orders; i++)
+		if (vaddr_orders[i] != orders[i]) {
+			ksft_print_msg("order %d: expected: %d got %d\n", i,
+				       orders[i], vaddr_orders[i]);
+			status = -1;
+		}
+
+	free(vaddr_orders);
+	return status;
+}
+
+static void write_file(const char *path, const char *buf, size_t buflen)
 {
 	int fd;
 	ssize_t numwritten;
 
 	fd = open(path, O_WRONLY);
 	if (fd == -1)
-		return 0;
+		ksft_exit_fail_msg("%s open failed: %s\n", path, strerror(errno));
 
 	numwritten = write(fd, buf, buflen - 1);
 	close(fd);
 	if (numwritten < 1)
-		return 0;
-
-	return (unsigned int) numwritten;
+		ksft_exit_fail_msg("Write failed\n");
 }
 
 static void write_debugfs(const char *fmt, ...)
@@ -77,237 +280,558 @@ static void write_debugfs(const char *fmt, ...)
 	ret = vsnprintf(input, INPUT_MAX, fmt, argp);
 	va_end(argp);
 
-	if (ret >= INPUT_MAX) {
-		printf("%s: Debugfs input is too long\n", __func__);
-		exit(EXIT_FAILURE);
-	}
+	if (ret >= INPUT_MAX)
+		ksft_exit_fail_msg("%s: Debugfs input is too long\n", __func__);
 
-	if (!write_file(SPLIT_DEBUGFS, input, ret + 1)) {
-		perror(SPLIT_DEBUGFS);
-		exit(EXIT_FAILURE);
-	}
+	write_file(SPLIT_DEBUGFS, input, ret + 1);
 }
 
-void split_pmd_thp(void)
+static char *allocate_zero_filled_hugepage(size_t len)
 {
-	char *one_page;
-	size_t len = 4 * pmd_pagesize;
+	char *result;
 	size_t i;
 
-	one_page = memalign(pmd_pagesize, len);
-
-	if (!one_page) {
+	result = memalign(pmd_pagesize, len);
+	if (!result) {
 		printf("Fail to allocate memory\n");
 		exit(EXIT_FAILURE);
 	}
 
-	madvise(one_page, len, MADV_HUGEPAGE);
+	madvise(result, len, MADV_HUGEPAGE);
 
 	for (i = 0; i < len; i++)
-		one_page[i] = (char)i;
+		result[i] = (char)0;
 
-	if (!check_huge_anon(one_page, 4, pmd_pagesize)) {
-		printf("No THP is allocated\n");
-		exit(EXIT_FAILURE);
-	}
+	return result;
+}
+
+static void verify_rss_anon_split_huge_page_all_zeroes(char *one_page, int nr_hpages, size_t len)
+{
+	unsigned long rss_anon_before, rss_anon_after;
+	size_t i;
+
+	if (!check_huge_anon(one_page, nr_hpages, pmd_pagesize))
+		ksft_exit_fail_msg("No THP is allocated\n");
+
+	rss_anon_before = rss_anon();
+	if (!rss_anon_before)
+		ksft_exit_fail_msg("No RssAnon is allocated before split\n");
 
 	/* split all THPs */
 	write_debugfs(PID_FMT, getpid(), (uint64_t)one_page,
-		(uint64_t)one_page + len);
+		      (uint64_t)one_page + len, 0);
 
 	for (i = 0; i < len; i++)
-		if (one_page[i] != (char)i) {
-			printf("%ld byte corrupted\n", i);
-			exit(EXIT_FAILURE);
-		}
+		if (one_page[i] != (char)0)
+			ksft_exit_fail_msg("%ld byte corrupted\n", i);
 
+	if (!check_huge_anon(one_page, 0, pmd_pagesize))
+		ksft_exit_fail_msg("Still AnonHugePages not split\n");
 
-	if (!check_huge_anon(one_page, 0, pmd_pagesize)) {
-		printf("Still AnonHugePages not split\n");
-		exit(EXIT_FAILURE);
-	}
+	rss_anon_after = rss_anon();
+	if (rss_anon_after >= rss_anon_before)
+		ksft_exit_fail_msg("Incorrect RssAnon value. Before: %ld After: %ld\n",
+		       rss_anon_before, rss_anon_after);
+}
 
-	printf("Split huge pages successful\n");
+static void split_pmd_zero_pages(void)
+{
+	char *one_page;
+	int nr_hpages = 4;
+	size_t len = nr_hpages * pmd_pagesize;
+
+	one_page = allocate_zero_filled_hugepage(len);
+	verify_rss_anon_split_huge_page_all_zeroes(one_page, nr_hpages, len);
+	ksft_test_result_pass("Split zero filled huge pages successful\n");
 	free(one_page);
 }
 
-void split_pte_mapped_thp(void)
+static void split_pmd_thp_to_order(int order)
 {
-	char *one_page, *pte_mapped, *pte_mapped2;
+	char *one_page;
 	size_t len = 4 * pmd_pagesize;
-	uint64_t thp_size;
 	size_t i;
-	const char *pagemap_template = "/proc/%d/pagemap";
-	const char *kpageflags_proc = "/proc/kpageflags";
-	char pagemap_proc[255];
-	int pagemap_fd;
-	int kpageflags_fd;
-
-	if (snprintf(pagemap_proc, 255, pagemap_template, getpid()) < 0) {
-		perror("get pagemap proc error");
-		exit(EXIT_FAILURE);
-	}
-	pagemap_fd = open(pagemap_proc, O_RDONLY);
 
-	if (pagemap_fd == -1) {
-		perror("read pagemap:");
-		exit(EXIT_FAILURE);
-	}
+	one_page = memalign(pmd_pagesize, len);
+	if (!one_page)
+		ksft_exit_fail_msg("Fail to allocate memory: %s\n", strerror(errno));
 
-	kpageflags_fd = open(kpageflags_proc, O_RDONLY);
+	madvise(one_page, len, MADV_HUGEPAGE);
 
-	if (kpageflags_fd == -1) {
-		perror("read kpageflags:");
-		exit(EXIT_FAILURE);
-	}
+	for (i = 0; i < len; i++)
+		one_page[i] = (char)i;
 
-	one_page = mmap((void *)(1UL << 30), len, PROT_READ | PROT_WRITE,
-			MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+	if (!check_huge_anon(one_page, 4, pmd_pagesize))
+		ksft_exit_fail_msg("No THP is allocated\n");
 
-	madvise(one_page, len, MADV_HUGEPAGE);
+	/* split all THPs */
+	write_debugfs(PID_FMT, getpid(), (uint64_t)one_page,
+		(uint64_t)one_page + len, order);
 
 	for (i = 0; i < len; i++)
-		one_page[i] = (char)i;
+		if (one_page[i] != (char)i)
+			ksft_exit_fail_msg("%ld byte corrupted\n", i);
 
-	if (!check_huge_anon(one_page, 4, pmd_pagesize)) {
-		printf("No THP is allocated\n");
-		exit(EXIT_FAILURE);
+	memset(expected_orders, 0, sizeof(int) * (pmd_order + 1));
+	expected_orders[order] = 4 << (pmd_order - order);
+
+	if (check_after_split_folio_orders(one_page, len, pagemap_fd,
+					   kpageflags_fd, expected_orders,
+					   (pmd_order + 1)))
+		ksft_exit_fail_msg("Unexpected THP split\n");
+
+	if (!check_huge_anon(one_page, 0, pmd_pagesize))
+		ksft_exit_fail_msg("Still AnonHugePages not split\n");
+
+	ksft_test_result_pass("Split huge pages to order %d successful\n", order);
+	free(one_page);
+}
+
+static void split_pte_mapped_thp(void)
+{
+	const size_t nr_thps = 4;
+	const size_t thp_area_size = nr_thps * pmd_pagesize;
+	const size_t page_area_size = nr_thps * pagesize;
+	char *thp_area, *tmp, *page_area = MAP_FAILED;
+	size_t i;
+
+	thp_area = mmap((void *)(1UL << 30), thp_area_size, PROT_READ | PROT_WRITE,
+			MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+	if (thp_area == MAP_FAILED) {
+		ksft_test_result_fail("Fail to allocate memory: %s\n", strerror(errno));
+		return;
 	}
 
-	/* remap the first pagesize of first THP */
-	pte_mapped = mremap(one_page, pagesize, pagesize, MREMAP_MAYMOVE);
+	madvise(thp_area, thp_area_size, MADV_HUGEPAGE);
 
-	/* remap the Nth pagesize of Nth THP */
-	for (i = 1; i < 4; i++) {
-		pte_mapped2 = mremap(one_page + pmd_pagesize * i + pagesize * i,
-				     pagesize, pagesize,
-				     MREMAP_MAYMOVE|MREMAP_FIXED,
-				     pte_mapped + pagesize * i);
-		if (pte_mapped2 == (char *)-1) {
-			perror("mremap failed");
-			exit(EXIT_FAILURE);
-		}
+	for (i = 0; i < thp_area_size; i++)
+		thp_area[i] = (char)i;
+
+	if (!check_huge_anon(thp_area, nr_thps, pmd_pagesize)) {
+		ksft_test_result_skip("Not all THPs allocated\n");
+		goto out;
 	}
 
-	/* smap does not show THPs after mremap, use kpageflags instead */
-	thp_size = 0;
-	for (i = 0; i < pagesize * 4; i++)
-		if (i % pagesize == 0 &&
-		    is_backed_by_thp(&pte_mapped[i], pagemap_fd, kpageflags_fd))
-			thp_size++;
+	/*
+	 * To challenge spitting code, we will mremap a single page of each
+	 * THP (page[i] of thp[i]) in the thp_area into page_area. This will
+	 * replace the PMD mappings in the thp_area by PTE mappings first,
+	 * but leaving the THP unsplit, to then create a page-sized hole in
+	 * the thp_area.
+	 * We will then manually trigger splitting of all THPs through the
+	 * single mremap'ed pages of each THP in the page_area.
+	 */
+	page_area = mmap(NULL, page_area_size, PROT_READ | PROT_WRITE,
+			MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+	if (page_area == MAP_FAILED) {
+		ksft_test_result_fail("Fail to allocate memory: %s\n", strerror(errno));
+		goto out;
+	}
 
-	if (thp_size != 4) {
-		printf("Some THPs are missing during mremap\n");
-		exit(EXIT_FAILURE);
+	for (i = 0; i < nr_thps; i++) {
+		tmp = mremap(thp_area + pmd_pagesize * i + pagesize * i,
+			     pagesize, pagesize, MREMAP_MAYMOVE|MREMAP_FIXED,
+			     page_area + pagesize * i);
+		if (tmp != MAP_FAILED)
+			continue;
+		ksft_test_result_fail("mremap failed: %s\n", strerror(errno));
+		goto out;
 	}
 
-	/* split all remapped THPs */
-	write_debugfs(PID_FMT, getpid(), (uint64_t)pte_mapped,
-		      (uint64_t)pte_mapped + pagesize * 4);
+	/*
+	 * Verify that our THPs were not split yet. Note that
+	 * check_huge_anon() cannot be used as it checks for PMD mappings.
+	 */
+	for (i = 0; i < nr_thps; i++) {
+		if (is_backed_by_folio(page_area + i * pagesize, pmd_order,
+				       pagemap_fd, kpageflags_fd))
+			continue;
+		ksft_test_result_fail("THP %zu missing after mremap\n", i);
+		goto out;
+	}
 
-	/* smap does not show THPs after mremap, use kpageflags instead */
-	thp_size = 0;
-	for (i = 0; i < pagesize * 4; i++) {
-		if (pte_mapped[i] != (char)i) {
-			printf("%ld byte corrupted\n", i);
-			exit(EXIT_FAILURE);
-		}
-		if (i % pagesize == 0 &&
-		    is_backed_by_thp(&pte_mapped[i], pagemap_fd, kpageflags_fd))
-			thp_size++;
+	/* Split all THPs through the remapped pages. */
+	write_debugfs(PID_FMT, getpid(), (uint64_t)page_area,
+		      (uint64_t)page_area + page_area_size, 0);
+
+	/* Corruption during mremap or split? */
+	for (i = 0; i < page_area_size; i++) {
+		if (page_area[i] == (char)i)
+			continue;
+		ksft_test_result_fail("%zu byte corrupted\n", i);
+		goto out;
 	}
 
-	if (thp_size) {
-		printf("Still %ld THPs not split\n", thp_size);
-		exit(EXIT_FAILURE);
+	/* Split failed? */
+	for (i = 0; i < nr_thps; i++) {
+		if (is_backed_by_folio(page_area + i * pagesize, 0,
+				       pagemap_fd, kpageflags_fd))
+			continue;
+		ksft_test_result_fail("THP %zu not split\n", i);
 	}
 
-	printf("Split PTE-mapped huge pages successful\n");
-	munmap(one_page, len);
-	close(pagemap_fd);
-	close(kpageflags_fd);
+	ksft_test_result_pass("Split PTE-mapped huge pages successful\n");
+out:
+	munmap(thp_area, thp_area_size);
+	if (page_area != MAP_FAILED)
+		munmap(page_area, page_area_size);
 }
 
-void split_file_backed_thp(void)
+static void split_file_backed_thp(int order)
 {
 	int status;
 	int fd;
-	ssize_t num_written;
 	char tmpfs_template[] = "/tmp/thp_split_XXXXXX";
 	const char *tmpfs_loc = mkdtemp(tmpfs_template);
 	char testfile[INPUT_MAX];
+	ssize_t num_written, num_read;
+	char *file_buf1, *file_buf2;
 	uint64_t pgoff_start = 0, pgoff_end = 1024;
+	int i;
 
-	printf("Please enable pr_debug in split_huge_pages_in_file() if you need more info.\n");
+	ksft_print_msg("Please enable pr_debug in split_huge_pages_in_file() for more info.\n");
 
-	status = mount("tmpfs", tmpfs_loc, "tmpfs", 0, "huge=always,size=4m");
+	file_buf1 = (char *)malloc(pmd_pagesize);
+	file_buf2 = (char *)malloc(pmd_pagesize);
 
-	if (status) {
-		printf("Unable to create a tmpfs for testing\n");
-		exit(EXIT_FAILURE);
+	if (!file_buf1 || !file_buf2) {
+		ksft_print_msg("cannot allocate file buffers\n");
+		goto out;
 	}
 
+	for (i = 0; i < pmd_pagesize; i++)
+		file_buf1[i] = (char)i;
+	memset(file_buf2, 0, pmd_pagesize);
+
+	status = mount("tmpfs", tmpfs_loc, "tmpfs", 0, "huge=always,size=4m");
+
+	if (status)
+		ksft_exit_fail_msg("Unable to create a tmpfs for testing\n");
+
 	status = snprintf(testfile, INPUT_MAX, "%s/thp_file", tmpfs_loc);
 	if (status >= INPUT_MAX) {
-		printf("Fail to create file-backed THP split testing file\n");
+		ksft_print_msg("Fail to create file-backed THP split testing file\n");
 		goto cleanup;
 	}
 
-	fd = open(testfile, O_CREAT|O_WRONLY);
+	fd = open(testfile, O_CREAT|O_RDWR, 0664);
 	if (fd == -1) {
-		perror("Cannot open testing file\n");
+		ksft_perror("Cannot open testing file");
 		goto cleanup;
 	}
 
-	/* write something to the file, so a file-backed THP can be allocated */
-	num_written = write(fd, tmpfs_loc, strlen(tmpfs_loc) + 1);
-	close(fd);
+	/* write pmd size data to the file, so a file-backed THP can be allocated */
+	num_written = write(fd, file_buf1, pmd_pagesize);
 
-	if (num_written < 1) {
-		printf("Fail to write data to testing file\n");
-		goto cleanup;
+	if (num_written == -1 || num_written != pmd_pagesize) {
+		ksft_perror("Failed to write data to testing file");
+		goto close_file;
 	}
 
 	/* split the file-backed THP */
-	write_debugfs(PATH_FMT, testfile, pgoff_start, pgoff_end);
+	write_debugfs(PATH_FMT, testfile, pgoff_start, pgoff_end, order);
+
+	/* check file content after split */
+	status = lseek(fd, 0, SEEK_SET);
+	if (status == -1) {
+		ksft_perror("Cannot lseek file");
+		goto close_file;
+	}
+
+	num_read = read(fd, file_buf2, num_written);
+	if (num_read == -1 || num_read != num_written) {
+		ksft_perror("Cannot read file content back");
+		goto close_file;
+	}
+
+	if (strncmp(file_buf1, file_buf2, pmd_pagesize) != 0) {
+		ksft_print_msg("File content changed\n");
+		goto close_file;
+	}
 
+	close(fd);
 	status = unlink(testfile);
-	if (status)
-		perror("Cannot remove testing file\n");
+	if (status) {
+		ksft_perror("Cannot remove testing file");
+		goto cleanup;
+	}
 
-cleanup:
 	status = umount(tmpfs_loc);
 	if (status) {
-		printf("Unable to umount %s\n", tmpfs_loc);
-		exit(EXIT_FAILURE);
+		rmdir(tmpfs_loc);
+		ksft_exit_fail_msg("Unable to umount %s\n", tmpfs_loc);
 	}
+
 	status = rmdir(tmpfs_loc);
-	if (status) {
-		perror("cannot remove tmp dir");
-		exit(EXIT_FAILURE);
+	if (status)
+		ksft_exit_fail_msg("cannot remove tmp dir: %s\n", strerror(errno));
+
+	ksft_print_msg("Please check dmesg for more information\n");
+	ksft_test_result_pass("File-backed THP split to order %d test done\n", order);
+	return;
+
+close_file:
+	close(fd);
+cleanup:
+	umount(tmpfs_loc);
+	rmdir(tmpfs_loc);
+out:
+	ksft_exit_fail_msg("Error occurred\n");
+}
+
+static bool prepare_thp_fs(const char *xfs_path, char *thp_fs_template,
+		const char **thp_fs_loc)
+{
+	if (xfs_path) {
+		*thp_fs_loc = xfs_path;
+		return false;
+	}
+
+	*thp_fs_loc = mkdtemp(thp_fs_template);
+
+	if (!*thp_fs_loc)
+		ksft_exit_fail_msg("cannot create temp folder\n");
+
+	return true;
+}
+
+static void cleanup_thp_fs(const char *thp_fs_loc, bool created_tmp)
+{
+	int status;
+
+	if (!created_tmp)
+		return;
+
+	status = rmdir(thp_fs_loc);
+	if (status)
+		ksft_exit_fail_msg("cannot remove tmp dir: %s\n",
+				   strerror(errno));
+}
+
+static int create_pagecache_thp_and_fd(const char *testfile, size_t fd_size,
+		int *fd, char **addr)
+{
+	size_t i;
+	unsigned char buf[1024];
+
+	srand(time(NULL));
+
+	*fd = open(testfile, O_CREAT | O_RDWR, 0664);
+	if (*fd == -1)
+		ksft_exit_fail_msg("Failed to create a file at %s\n", testfile);
+
+	assert(fd_size % sizeof(buf) == 0);
+	for (i = 0; i < sizeof(buf); i++)
+		buf[i] = (unsigned char)i;
+	for (i = 0; i < fd_size; i += sizeof(buf))
+		write(*fd, buf, sizeof(buf));
+
+	close(*fd);
+	sync();
+	*fd = open("/proc/sys/vm/drop_caches", O_WRONLY);
+	if (*fd == -1) {
+		ksft_perror("open drop_caches");
+		goto err_out_unlink;
+	}
+	if (write(*fd, "3", 1) != 1) {
+		ksft_perror("write to drop_caches");
+		goto err_out_unlink;
+	}
+	close(*fd);
+
+	*fd = open(testfile, O_RDWR);
+	if (*fd == -1) {
+		ksft_perror("Failed to open testfile\n");
+		goto err_out_unlink;
+	}
+
+	*addr = mmap(NULL, fd_size, PROT_READ|PROT_WRITE, MAP_SHARED, *fd, 0);
+	if (*addr == (char *)-1) {
+		ksft_perror("cannot mmap");
+		goto err_out_close;
+	}
+	madvise(*addr, fd_size, MADV_HUGEPAGE);
+
+	for (size_t i = 0; i < fd_size; i++) {
+		char *addr2 = *addr + i;
+
+		FORCE_READ(*addr2);
+	}
+
+	if (!check_huge_file(*addr, fd_size / pmd_pagesize, pmd_pagesize)) {
+		ksft_print_msg("No large pagecache folio generated, please provide a filesystem supporting large folio\n");
+		munmap(*addr, fd_size);
+		close(*fd);
+		unlink(testfile);
+		ksft_test_result_skip("Pagecache folio split skipped\n");
+		return -2;
+	}
+	return 0;
+err_out_close:
+	close(*fd);
+err_out_unlink:
+	unlink(testfile);
+	ksft_exit_fail_msg("Failed to create large pagecache folios\n");
+	return -1;
+}
+
+static void split_thp_in_pagecache_to_order_at(size_t fd_size,
+		const char *fs_loc, int order, int offset)
+{
+	int fd;
+	char *split_addr;
+	char *addr;
+	size_t i;
+	char testfile[INPUT_MAX];
+	int err = 0;
+
+	err = snprintf(testfile, INPUT_MAX, "%s/test", fs_loc);
+
+	if (err < 0)
+		ksft_exit_fail_msg("cannot generate right test file name\n");
+
+	err = create_pagecache_thp_and_fd(testfile, fd_size, &fd, &addr);
+	if (err)
+		return;
+
+	err = 0;
+
+	memset(expected_orders, 0, sizeof(int) * (pmd_order + 1));
+	/*
+	 * use [split_addr, split_addr + pagesize) range to split THPs, since
+	 * the debugfs function always split a range with pagesize step and
+	 * providing a full [addr, addr + fd_size) range can trigger multiple
+	 * splits, complicating after-split result checking.
+	 */
+	if (offset == -1) {
+		for (split_addr = addr; split_addr < addr + fd_size; split_addr += pmd_pagesize)
+			write_debugfs(PID_FMT, getpid(), (uint64_t)split_addr,
+				      (uint64_t)split_addr + pagesize, order);
+
+		expected_orders[order] = fd_size / (pagesize << order);
+	} else {
+		int times = fd_size / pmd_pagesize;
+
+		for (split_addr = addr; split_addr < addr + fd_size; split_addr += pmd_pagesize)
+			write_debugfs(PID_FMT_OFFSET, getpid(), (uint64_t)split_addr,
+				      (uint64_t)split_addr + pagesize, order, offset);
+
+		for (i = order + 1; i < pmd_order; i++)
+			expected_orders[i] = times;
+		expected_orders[order] = 2 * times;
+	}
+
+	for (i = 0; i < fd_size; i++)
+		if (*(addr + i) != (char)i) {
+			ksft_print_msg("%lu byte corrupted in the file\n", i);
+			err = EXIT_FAILURE;
+			goto out;
+		}
+
+	if (check_after_split_folio_orders(addr, fd_size, pagemap_fd,
+					   kpageflags_fd, expected_orders,
+					   (pmd_order + 1))) {
+		ksft_print_msg("Unexpected THP split\n");
+		err = 1;
+		goto out;
 	}
 
-	printf("file-backed THP split test done, please check dmesg for more information\n");
+	if (!check_huge_file(addr, 0, pmd_pagesize)) {
+		ksft_print_msg("Still FilePmdMapped not split\n");
+		err = EXIT_FAILURE;
+		goto out;
+	}
+
+out:
+	munmap(addr, fd_size);
+	close(fd);
+	unlink(testfile);
+	if (offset == -1) {
+		if (err)
+			ksft_exit_fail_msg("Split PMD-mapped pagecache folio to order %d failed\n", order);
+		ksft_test_result_pass("Split PMD-mapped pagecache folio to order %d passed\n", order);
+	} else {
+		if (err)
+			ksft_exit_fail_msg("Split PMD-mapped pagecache folio to order %d at in-folio offset %d failed\n", order, offset);
+		ksft_test_result_pass("Split PMD-mapped pagecache folio to order %d at in-folio offset %d passed\n", order, offset);
+	}
 }
 
 int main(int argc, char **argv)
 {
+	int i;
+	size_t fd_size;
+	char *optional_xfs_path = NULL;
+	char fs_loc_template[] = "/tmp/thp_fs_XXXXXX";
+	const char *fs_loc;
+	bool created_tmp;
+	int offset;
+	unsigned int nr_pages;
+	unsigned int tests;
+
+	ksft_print_header();
+
 	if (geteuid() != 0) {
-		printf("Please run the benchmark as root\n");
-		exit(EXIT_FAILURE);
+		ksft_print_msg("Please run the benchmark as root\n");
+		ksft_finished();
 	}
 
+	if (argc > 1)
+		optional_xfs_path = argv[1];
+
 	pagesize = getpagesize();
 	pageshift = ffs(pagesize) - 1;
 	pmd_pagesize = read_pmd_pagesize();
-	if (!pmd_pagesize) {
-		printf("Reading PMD pagesize failed\n");
-		exit(EXIT_FAILURE);
-	}
+	if (!pmd_pagesize)
+		ksft_exit_fail_msg("Reading PMD pagesize failed\n");
+
+	nr_pages = pmd_pagesize / pagesize;
+	pmd_order = sz2ord(pmd_pagesize, pagesize);
+
+	expected_orders = (int *)malloc(sizeof(int) * (pmd_order + 1));
+	if (!expected_orders)
+		ksft_exit_fail_msg("Fail to allocate memory: %s\n", strerror(errno));
+
+	tests = 2 + (pmd_order - 1) + (2 * pmd_order) + (pmd_order - 1) * 4 + 2;
+	ksft_set_plan(tests);
+
+	pagemap_fd = open(pagemap_proc, O_RDONLY);
+	if (pagemap_fd == -1)
+		ksft_exit_fail_msg("read pagemap: %s\n", strerror(errno));
+
+	kpageflags_fd = open(kpageflags_proc, O_RDONLY);
+	if (kpageflags_fd == -1)
+		ksft_exit_fail_msg("read kpageflags: %s\n", strerror(errno));
+
+	fd_size = 2 * pmd_pagesize;
+
+	split_pmd_zero_pages();
+
+	for (i = 0; i < pmd_order; i++)
+		if (i != 1)
+			split_pmd_thp_to_order(i);
 
-	split_pmd_thp();
 	split_pte_mapped_thp();
-	split_file_backed_thp();
+	for (i = 0; i < pmd_order; i++)
+		split_file_backed_thp(i);
+
+	created_tmp = prepare_thp_fs(optional_xfs_path, fs_loc_template,
+			&fs_loc);
+	for (i = pmd_order - 1; i >= 0; i--)
+		split_thp_in_pagecache_to_order_at(fd_size, fs_loc, i, -1);
+
+	for (i = 0; i < pmd_order; i++)
+		for (offset = 0;
+		     offset < nr_pages;
+		     offset += MAX(nr_pages / 4, 1 << i))
+			split_thp_in_pagecache_to_order_at(fd_size, fs_loc, i, offset);
+	cleanup_thp_fs(fs_loc, created_tmp);
+
+	close(pagemap_fd);
+	close(kpageflags_fd);
+	free(expected_orders);
+
+	ksft_finished();
 
 	return 0;
 }