On Mon, Mar 15, 2021 at 1:34 PM Zi Yan <zi.yan@xxxxxxxx> wrote:
>
> From: Zi Yan <ziy@xxxxxxxxxx>
>
> Further extend <debugfs>/split_huge_pages to accept
> "<path>,<off_start>,<off_end>" for file-backed THP split tests since
> tmpfs may have file backed by THP that mapped nowhere.
>
> Update selftest program to test file-backed THP split too.
>
> Suggested-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
> ---
> mm/huge_memory.c | 95 ++++++++++++++++++-
> .../selftests/vm/split_huge_page_test.c | 79 ++++++++++++++-
> 2 files changed, 166 insertions(+), 8 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 3bfee54e2cd0..da91ee97d944 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -3043,12 +3043,72 @@ static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
> return ret;
> }
>
> +static int split_huge_pages_in_file(const char *file_path, pgoff_t off_start,
> + pgoff_t off_end)
> +{
> + struct filename *file;
> + struct file *candidate;
> + struct address_space *mapping;
> + int ret = -EINVAL;
> + pgoff_t off_cur;
> + unsigned long total = 0, split = 0;
> +
> + file = getname_kernel(file_path);
> + if (IS_ERR(file))
> + return ret;
> +
> + candidate = file_open_name(file, O_RDONLY, 0);
> + if (IS_ERR(candidate))
> + goto out;
> +
> + pr_info("split file-backed THPs in file: %s, offset: [0x%lx - 0x%lx]\n",
> + file_path, off_start, off_end);
> +
> + mapping = candidate->f_mapping;
> +
> + for (off_cur = off_start; off_cur < off_end;) {
> + struct page *fpage = pagecache_get_page(mapping, off_cur,
> + FGP_ENTRY | FGP_HEAD, 0);
> +
> + if (xa_is_value(fpage) || !fpage) {
Why do you have FGP_ENTRY? It seems it would return page instead of
NULL if page is value. So I think you could remove FGP_ENTRY and
xa_is_value() check as well.
> + off_cur += PAGE_SIZE;
> + continue;
> + }
> +
> + if (!is_transparent_hugepage(fpage)) {
> + off_cur += PAGE_SIZE;
> + goto next;
> + }
> + total++;
> + off_cur = fpage->index + thp_size(fpage);
> +
> + if (!trylock_page(fpage))
> + goto next;
> +
> + if (!split_huge_page(fpage))
> + split++;
> +
> + unlock_page(fpage);
> +next:
> + put_page(fpage);
> + }
> +
> + filp_close(candidate, NULL);
> + ret = 0;
> +
> + pr_info("%lu of %lu file-backed THP split\n", split, total);
> +out:
> + putname(file);
> + return ret;
> +}
> +
> static ssize_t split_huge_pages_write(struct file *file, const char __user *buf,
> size_t count, loff_t *ppops)
> {
> static DEFINE_MUTEX(mutex);
> ssize_t ret;
> - char input_buf[80]; /* hold pid, start_vaddr, end_vaddr */
> + /* hold pid, start_vaddr, end_vaddr or file_path, off_start, off_end */
> + char input_buf[MAX_INPUT];
I didn't find where MAX_INPUT is defined in your patch. Just saw
include/uapi/linux/limits.h have it defined. Is it the one you really
refer to?
> int pid;
> unsigned long vaddr_start, vaddr_end;
>
> @@ -3058,11 +3118,40 @@ static ssize_t split_huge_pages_write(struct file *file, const char __user *buf,
>
> ret = -EFAULT;
>
> - memset(input_buf, 0, 80);
> + memset(input_buf, 0, MAX_INPUT);
> if (copy_from_user(input_buf, buf, min_t(size_t, count, 80)))
> goto out;
>
> - input_buf[79] = '\0';
> + input_buf[MAX_INPUT - 1] = '\0';
> +
> + if (input_buf[0] == '/') {
> + char *tok;
> + char *buf = input_buf;
> + char file_path[MAX_INPUT];
> + pgoff_t off_start = 0, off_end = 0;
> + size_t input_len = strlen(input_buf);
> +
> + tok = strsep(&buf, ",");
> + if (tok) {
> + strncpy(file_path, tok, MAX_INPUT);
> + } else {
> + ret = -EINVAL;
> + goto out;
> + }
> +
> + ret = sscanf(buf, "0x%lx,0x%lx", &off_start, &off_end);
> + if (ret != 2) {
> + pr_info("ret: %ld\n", ret);
> + ret = -EINVAL;
> + goto out;
> + }
> + ret = split_huge_pages_in_file(file_path, off_start, off_end);
> + if (!ret)
> + ret = input_len;
> +
> + goto out;
> + }
> +
> ret = sscanf(input_buf, "%d,0x%lx,0x%lx", &pid, &vaddr_start, &vaddr_end);
> if (ret == 1 && pid == 1) {
> split_huge_pages_all();
> diff --git a/tools/testing/selftests/vm/split_huge_page_test.c b/tools/testing/selftests/vm/split_huge_page_test.c
> index 9f33ddbb3182..0202702f7eda 100644
> --- a/tools/testing/selftests/vm/split_huge_page_test.c
> +++ b/tools/testing/selftests/vm/split_huge_page_test.c
> @@ -7,11 +7,13 @@
> #define _GNU_SOURCE
> #include <stdio.h>
> #include <stdlib.h>
> +#include <stdarg.h>
> #include <unistd.h>
> #include <inttypes.h>
> #include <string.h>
> #include <fcntl.h>
> #include <sys/mman.h>
> +#include <sys/mount.h>
> #include <malloc.h>
> #include <stdbool.h>
>
> @@ -24,6 +26,9 @@ uint64_t pmd_pagesize;
> #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 PFN_MASK ((1UL<<55)-1)
> #define KPF_THP (1UL<<22)
>
> @@ -87,13 +92,16 @@ static int write_file(const char *path, const char *buf, size_t buflen)
> return (unsigned int) numwritten;
> }
>
> -static void write_debugfs(int pid, uint64_t vaddr_start, uint64_t vaddr_end)
> +static void write_debugfs(const char *fmt, ...)
> {
> char input[INPUT_MAX];
> int ret;
> + va_list argp;
> +
> + va_start(argp, fmt);
> + ret = vsnprintf(input, INPUT_MAX, fmt, argp);
> + va_end(argp);
>
> - ret = snprintf(input, INPUT_MAX, "%d,0x%lx,0x%lx", pid, vaddr_start,
> - vaddr_end);
> if (ret >= INPUT_MAX) {
> printf("%s: Debugfs input is too long\n", __func__);
> exit(EXIT_FAILURE);
> @@ -178,7 +186,8 @@ void split_pmd_thp(void)
> }
>
> /* split all THPs */
> - write_debugfs(getpid(), (uint64_t)one_page, (uint64_t)one_page + len);
> + write_debugfs(PID_FMT, getpid(), (uint64_t)one_page,
> + (uint64_t)one_page + len);
>
> for (i = 0; i < len; i++)
> if (one_page[i] != (char)i) {
> @@ -269,7 +278,7 @@ void split_pte_mapped_thp(void)
> }
>
> /* split all remapped THPs */
> - write_debugfs(getpid(), (uint64_t)pte_mapped,
> + write_debugfs(PID_FMT, getpid(), (uint64_t)pte_mapped,
> (uint64_t)pte_mapped + pagesize * 4);
>
> /* smap does not show THPs after mremap, use kpageflags instead */
> @@ -295,6 +304,65 @@ void split_pte_mapped_thp(void)
> close(kpageflags_fd);
> }
>
> +void split_file_backed_thp(void)
> +{
> + 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];
> +
> + status = mount("tmpfs", tmpfs_loc, "tmpfs", 0, "huge=always,size=4m");
> +
> + if (status) {
> + printf("Unable to create a tmpfs for testing\n");
> + exit(EXIT_FAILURE);
> + }
> +
> + 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");
> + goto cleanup;
> + }
> +
> + fd = open(testfile, O_CREAT|O_WRONLY);
> + if (fd == -1) {
> + perror("Cannot open testing file\n");
> + goto cleanup;
> + }
> +
> + /* write something to the file, so a file-backed THP can be allocated */
> + num_written = write(fd, tmpfs_loc, sizeof(tmpfs_loc));
> + close(fd);
> +
> + if (num_written < 1) {
> + printf("Fail to write data to testing file\n");
> + goto cleanup;
> + }
> +
> + /* split the file-backed THP */
> + write_debugfs(PATH_FMT, testfile, 0, 1024);
> +
> + status = unlink(testfile);
> + if (status)
> + perror("Cannot remove testing file\n");
> +
> +cleanup:
> + status = umount(tmpfs_loc);
> + if (status) {
> + printf("Unable to umount %s\n", tmpfs_loc);
> + exit(EXIT_FAILURE);
> + }
> + status = rmdir(tmpfs_loc);
> + if (status) {
> + perror("cannot remove tmp dir");
> + exit(EXIT_FAILURE);
> + }
> +
> + printf("file-backed THP split test done, please check dmesg for more information\n");
> +}
> +
> int main(int argc, char **argv)
> {
> if (geteuid() != 0) {
> @@ -308,6 +376,7 @@ int main(int argc, char **argv)
>
> split_pmd_thp();
> split_pte_mapped_thp();
> + split_file_backed_thp();
>
> return 0;
> }
> --
> 2.30.1
>
