Re: [PATCH v2 3/3] selftests/mm: check after-split folio orders in split_huge_page_test.

[Donet Tom <donettom@linux.ibm.com>]

On 8/9/25 12:31 AM, Zi Yan wrote:
> Instead of just checking the existence of PMD folios before and after folio
> split tests, use check_folio_orders() to check after-split folio orders.
>
> The following tests are not changed:
> 1. split_pte_mapped_thp: the test already uses kpageflags to check;
> 2. split_file_backed_thp: no vaddr available.
>
> Signed-off-by: Zi Yan <ziy@nvidia.com>
> ---
>   .../selftests/mm/split_huge_page_test.c       | 98 ++++++++++++++-----
>   1 file changed, 72 insertions(+), 26 deletions(-)
>
> diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c
> index 5ab488fab1cd..161108717f1c 100644
> --- a/tools/testing/selftests/mm/split_huge_page_test.c
> +++ b/tools/testing/selftests/mm/split_huge_page_test.c
> @@ -25,6 +25,10 @@
>   uint64_t pagesize;
>   unsigned int pageshift;
>   uint64_t pmd_pagesize;
> +unsigned int pmd_order;
> +unsigned int max_order;
> +
> +#define NR_ORDERS (max_order + 1)
>   
>   #define SPLIT_DEBUGFS "/sys/kernel/debug/split_huge_pages"
>   #define SMAP_PATH "/proc/self/smaps"
> @@ -36,6 +40,11 @@ uint64_t pmd_pagesize;
>   
>   #define GET_ORDER(nr_pages)    (31 - __builtin_clz(nr_pages))
>   
> +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)
>   {
>   	uint64_t paddr;
> @@ -151,6 +160,11 @@ void split_pmd_thp_to_order(int order)
>   	char *one_page;
>   	size_t len = 4 * pmd_pagesize;
>   	size_t i;
> +	int *orders;
> +
> +	orders = (int *)malloc(sizeof(int) * NR_ORDERS);
> +	if (!orders)
> +		ksft_exit_fail_msg("Fail to allocate memory: %s\n", strerror(errno));
>   
>   	one_page = memalign(pmd_pagesize, len);
>   	if (!one_page)
> @@ -172,12 +186,20 @@ void split_pmd_thp_to_order(int order)
>   		if (one_page[i] != (char)i)
>   			ksft_exit_fail_msg("%ld byte corrupted\n", i);
>   
> +	memset(orders, 0, sizeof(int) * NR_ORDERS);
> +	/* set expected orders */
> +	orders[order] = 4 << (pmd_order - order);
> +
> +	if (check_folio_orders(one_page, len, pagemap_fd, kpageflags_fd,
> +			       orders, NR_ORDERS))
> +		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);
> +	free(orders);
>   }
>   
>   void split_pte_mapped_thp(void)
> @@ -186,22 +208,6 @@ void split_pte_mapped_thp(void)
>   	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)
> -		ksft_exit_fail_msg("get pagemap proc error: %s\n", strerror(errno));
> -
> -	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));
>   
>   	one_page = mmap((void *)(1UL << 30), len, PROT_READ | PROT_WRITE,
>   			MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
> @@ -259,8 +265,6 @@ void split_pte_mapped_thp(void)
>   
>   	ksft_test_result_pass("Split PTE-mapped huge pages successful\n");
>   	munmap(one_page, len);
> -	close(pagemap_fd);
> -	close(kpageflags_fd);
>   }
>   
>   void split_file_backed_thp(int order)
> @@ -463,10 +467,16 @@ 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;
> +	int *orders;
> +
> +	orders = (int *)malloc(sizeof(int) * NR_ORDERS);
> +	if (!orders)
> +		ksft_exit_fail_msg("Fail to allocate memory: %s\n", strerror(errno));
>   
>   	err = snprintf(testfile, INPUT_MAX, "%s/test", fs_loc);
>   
> @@ -474,16 +484,32 @@ void split_thp_in_pagecache_to_order_at(size_t fd_size, const char *fs_loc,
>   		ksft_exit_fail_msg("cannot generate right test file name\n");
>   
>   	err = create_pagecache_thp_and_fd(testfile, fd_size, &fd, &addr);
> -	if (err)
> +	if (err) {
> +		free(orders);
>   		return;
> +	}
>   	err = 0;
>   
> -	if (offset == -1)
> -		write_debugfs(PID_FMT, getpid(), (uint64_t)addr,
> -			      (uint64_t)addr + fd_size, order);
> -	else
> -		write_debugfs(PID_FMT_OFFSET, getpid(), (uint64_t)addr,
> -			      (uint64_t)addr + fd_size, order, offset);
> +	memset(orders, 0, sizeof(int) * NR_ORDERS);
> +	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);
> +
> +		/* set expected orders */
> +		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);
> +
> +		/* set expected orders */
> +		for (i = order + 1; i < pmd_order; i++)
> +			orders[i] = times;
> +		orders[order] = 2 * times;
> +	}
>   
>   	for (i = 0; i < fd_size; i++)
>   		if (*(addr + i) != (char)i) {
> @@ -492,6 +518,14 @@ void split_thp_in_pagecache_to_order_at(size_t fd_size, const char *fs_loc,
>   			goto out;
>   		}
>   
> +	if (check_folio_orders(addr, fd_size, pagemap_fd, kpageflags_fd, orders,
> +			       NR_ORDERS)) {
> +		ksft_print_msg("Unexpected THP split\n");
> +		err = 1;
> +		goto out;
> +	}
> +
> +
>   	if (!check_huge_file(addr, 0, pmd_pagesize)) {
>   		ksft_print_msg("Still FilePmdMapped not split\n");
>   		err = EXIT_FAILURE;
> @@ -499,6 +533,7 @@ void split_thp_in_pagecache_to_order_at(size_t fd_size, const char *fs_loc,
>   	}
>   
>   out:
> +	free(orders);
>   	munmap(addr, fd_size);
>   	close(fd);
>   	unlink(testfile);
> @@ -522,7 +557,6 @@ int main(int argc, char **argv)
>   	const char *fs_loc;
>   	bool created_tmp;
>   	int offset;
> -	unsigned int max_order;
>   	unsigned int nr_pages;
>   	unsigned int tests;
>   
> @@ -539,6 +573,7 @@ int main(int argc, char **argv)
>   	pagesize = getpagesize();
>   	pageshift = ffs(pagesize) - 1;
>   	pmd_pagesize = read_pmd_pagesize();
> +	pmd_order = GET_ORDER(pmd_pagesize / pagesize);


I think max_order is also same as pmd_order

   nr_pages = pmd_pagesize / pagesize;
   max_order = GET_ORDER(nr_pages);

Can we use one?

>   	if (!pmd_pagesize)
>   		ksft_exit_fail_msg("Reading PMD pagesize failed\n");
>   
> @@ -547,6 +582,14 @@ int main(int argc, char **argv)
>   	tests = 2 + (max_order - 1) + (2 * max_order) + (max_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();
> @@ -571,6 +614,9 @@ int main(int argc, char **argv)
>   			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);
> +
>   	ksft_finished();
>   
>   	return 0;