Re: [PATCH 1/4] src/open_by_handle: helper to test open_by_handle_at() syscall

J . Bruce Fields
2017-04-18T18:55:27Z

On Tue, Apr 18, 2017 at 09:17:21PM +0300, Amir Goldstein wrote:
> This is a clone of src/stale_handle.c test that uses generic
> open_by_handle_at() syscall instead of the xfs specific ioctl.
>
> No test is using this helper yet.
>
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> ---
> src/Makefile | 2 +-
> src/open_by_handle.c | 145 +++++++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 146 insertions(+), 1 deletion(-)
> create mode 100644 src/open_by_handle.c
>
> diff --git a/src/Makefile b/src/Makefile
> index e62d7a9..6b38e77 100644
> --- a/src/Makefile
> +++ b/src/Makefile
> @@ -22,7 +22,7 @@ LINUX_TARGETS = xfsctl bstat t_mtab getdevicesize preallo_rw_pattern_reader \
> seek_copy_test t_readdir_1 t_readdir_2 fsync-tester nsexec cloner \
> renameat2 t_getcwd e4compact test-nextquota punch-alternating \
> attr-list-by-handle-cursor-test listxattr dio-interleaved t_dir_type \
> - dio-invalidate-cache stat_test
> + dio-invalidate-cache stat_test open_by_handle
>
> SUBDIRS =
>
> diff --git a/src/open_by_handle.c b/src/open_by_handle.c
> new file mode 100644
> index 0000000..8f04865
> --- /dev/null
> +++ b/src/open_by_handle.c
> @@ -0,0 +1,145 @@
> +/*
> + * open_by_handle.c - attempt to create a file handle and open it
> + * with open_by_handle_at() syscall
> + *
> + * Copyright (C) 2017 CTERA Networks. All Rights Reserved.
> + * Author: Amir Goldstein <amir73il@gmail.com>
> + *
> + * from:
> + * stale_handle.c
> + *
> + * Copyright (C) 2010 Red Hat, Inc. All Rights reserved.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program; if not, write to the Free Software
> + * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
> + */
> +
> +#define TEST_UTIME
> +
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <fcntl.h>
> +#include <unistd.h>
> +#include <sys/stat.h>
> +#include <sys/types.h>
> +#include <errno.h>
> +#include <linux/limits.h>
> +
> +#define NUMFILES 1024
> +
> +struct handle {
> + struct file_handle fh;
> + unsigned char fid[MAX_HANDLE_SZ];
> +} handle[NUMFILES];
> +
> +int main(int argc, char **argv)
> +{
> + int i;
> + int fd;
> + int ret;
> + int failed = 0;
> + char fname[PATH_MAX];
> + char *test_dir;
> + int mount_fd, mount_id;
> +
> + if (argc != 2) {
> + fprintf(stderr, "usage: open_by_handle <test_dir>\n");
> + return EXIT_FAILURE;
> + }
> +
> + test_dir = argv[1];
> + mount_fd = open(test_dir, O_RDONLY|O_DIRECTORY);
> + if (mount_fd < 0) {
> + perror("open test_dir");
> + return EXIT_FAILURE;
> + }
> +
> + /*
> + * create a large number of files to force allocation of new inode
> + * chunks on disk.
> + */
> + for (i=0; i < NUMFILES; i++) {
> + sprintf(fname, "%s/file%06d", test_dir, i);
> + fd = open(fname, O_RDWR | O_CREAT | O_TRUNC, 0644);
> + if (fd < 0) {
> + printf("Warning (%s,%d), open(%s) failed.\n", __FILE__, __LINE__, fname);
> + perror(fname);
> + return EXIT_FAILURE;
> + }
> + close(fd);
> + }
> +
> + /* sync to get the new inodes to hit the disk */
> + sync();
> +
> + /* create the handles */
> + for (i=0; i < NUMFILES; i++) {
> + sprintf(fname, "%s/file%06d", test_dir, i);
> + handle[i].fh.handle_bytes = MAX_HANDLE_SZ;
> + ret = name_to_handle_at(AT_FDCWD, fname, &handle[i].fh, &mount_id, 0);
> + if (ret < 0) {
> + perror("name_to_handle");
> + return EXIT_FAILURE;
> + }
> + }
> +
> + /* unlink the files */
> + for (i=0; i < NUMFILES; i++) {
> + sprintf(fname, "%s/file%06d", test_dir, i);
> + ret = unlink(fname);
> + if (ret < 0) {
> + perror("unlink");
> + return EXIT_FAILURE;
> + }
> + }
> +
> + /* sync to get log forced for unlink transactions to hit the disk */
> + sync();
> +
> + /* sync once more FTW */
> + sync();
> +
> + /*
> + * now drop the caches so that unlinked inodes are reclaimed and
> + * buftarg page cache is emptied so that the inode cluster has to be
> + * fetched from disk again for the open_by_handle() call.
> + */
> + ret = system("echo 3 > /proc/sys/vm/drop_caches");
> + if (ret < 0) {
> + perror("drop_caches");
> + return EXIT_FAILURE;

By the way, I noticed some time ago in kernel commit 75a6f82a0d10 that
Al uses a remount for this instead of drop_caches; I wonder if that has
any advantages or if it just amounts to the same thing?

--b.

> + }
> +
> + /*
> + * now try to open the files by the stored handles. Expecting ENOENT
> + * for all of them.
> + */
> + for (i=0; i < NUMFILES; i++) {
> + errno = 0;
> + fd = open_by_handle_at(mount_fd, &handle[i].fh, O_RDWR);
> + if (fd < 0 && (errno == ENOENT || errno == ESTALE)) {
> + continue;
> + }
> + if (fd >= 0) {
> + printf("open_by_handle(%d) opened an unlinked file!\n", i);
> + close(fd);
> + } else
> + printf("open_by_handle(%d) returned %d incorrectly on an unlinked file!\n", i, errno);
> + failed++;
> + }
> + if (failed)
> + return EXIT_FAILURE;
> + return EXIT_SUCCESS;
> +}
> --
> 2.7.4