On Fri, May 09, 2025 at 07:00:32PM +0200, Amir Goldstein wrote:
> Test for kernel and filesystem support for conenctable file handles.
>
> With -N flag, encode connectable file handles and fail the test if the
> kernel or filesystem do not support conenctable file handles.
>
> Verify that decoding connectable file handles always results in a non
> empty path of the fd.
>
> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
Reviewed-by: Zorro Lang <zlang@xxxxxxxxxx>
> common/rc | 16 ++++++++++---
> src/open_by_handle.c | 53 ++++++++++++++++++++++++++++++++++++--------
> 2 files changed, 57 insertions(+), 12 deletions(-)
>
> diff --git a/common/rc b/common/rc
> index 6592c835..6407b744 100644
> --- a/common/rc
> +++ b/common/rc
> @@ -3829,8 +3829,14 @@ _require_freeze()
> }
>
> # Does NFS export work on this fs?
> -_require_exportfs()
> +_require_open_by_handle()
> {
> + local what="NFS export"
> + local opts="$1"
> + if [ "$1" == "-N" ]; then
> + what="connectable file handles"
> + fi
> +
> _require_test_program "open_by_handle"
>
> # virtiofs doesn't support open_by_handle_at(2) yet, though the syscall
> @@ -3841,10 +3847,14 @@ _require_exportfs()
> _notrun "$FSTYP doesn't support open_by_handle_at(2)"
>
> mkdir -p "$TEST_DIR"/exportfs_test
> - $here/src/open_by_handle -c "$TEST_DIR"/exportfs_test 2>&1 \
> - || _notrun "$FSTYP does not support NFS export"
> + $here/src/open_by_handle $opts -c "$TEST_DIR"/exportfs_test 2>&1 \
> + || _notrun "$FSTYP does not support $what"
> }
>
> +_require_exportfs()
> +{
> + _require_open_by_handle
> +}
>
> # Does shutdown work on this fs?
> _require_scratch_shutdown()
> diff --git a/src/open_by_handle.c b/src/open_by_handle.c
> index a99cce4b..7b664201 100644
> --- a/src/open_by_handle.c
> +++ b/src/open_by_handle.c
> @@ -96,6 +96,9 @@ Examples:
> #ifndef AT_HANDLE_MNT_ID_UNIQUE
> # define AT_HANDLE_MNT_ID_UNIQUE 0x001
> #endif
> +#ifndef AT_HANDLE_CONNECTABLE
> +# define AT_HANDLE_CONNECTABLE 0x002
> +#endif
>
> #define MAXFILES 1024
>
> @@ -121,6 +124,7 @@ void usage(void)
> fprintf(stderr, "open_by_handle -d <test_dir> [N] - unlink test files and hardlinks, drop caches and try to open by handle\n");
> fprintf(stderr, "open_by_handle -m <test_dir> [N] - rename test files, drop caches and try to open by handle\n");
> fprintf(stderr, "open_by_handle -M <test_dir> [N] - do not silently skip the mount ID verifications\n");
> + fprintf(stderr, "open_by_handle -N <test_dir> [N] - encode connectable file handles\n");
> fprintf(stderr, "open_by_handle -p <test_dir> - create/delete and try to open by handle also test_dir itself\n");
> fprintf(stderr, "open_by_handle -i <handles_file> <test_dir> [N] - read test files handles from file and try to open by handle\n");
> fprintf(stderr, "open_by_handle -o <handles_file> <test_dir> [N] - get file handles of test files and write handles to file\n");
> @@ -130,14 +134,16 @@ void usage(void)
> fprintf(stderr, "open_by_handle -C <feature> - check if <feature> is supported by the kernel.\n");
> fprintf(stderr, " <feature> can be any of the following values:\n");
> fprintf(stderr, " - AT_HANDLE_MNT_ID_UNIQUE\n");
> + fprintf(stderr, " - AT_HANDLE_CONNECTABLE\n");
> exit(EXIT_FAILURE);
> }
>
> -static int do_name_to_handle_at(const char *fname, struct file_handle *fh,
> - int bufsz, bool force_check_mountid)
> +static int do_name_to_handle_at(const char *fname, struct file_handle *fh, int bufsz,
> + bool force_check_mountid, bool connectable)
> {
> int ret;
> int mntid_short;
> + int at_flags;
>
> static bool skip_mntid, skip_mntid_unique;
>
> @@ -181,18 +187,24 @@ static int do_name_to_handle_at(const char *fname, struct file_handle *fh,
> }
> }
>
> + at_flags = connectable ? AT_HANDLE_CONNECTABLE : 0;
> fh->handle_bytes = bufsz;
> - ret = name_to_handle_at(AT_FDCWD, fname, fh, &mntid_short, 0);
> + ret = name_to_handle_at(AT_FDCWD, fname, fh, &mntid_short, at_flags);
> if (bufsz < fh->handle_bytes) {
> /* Query the filesystem required bufsz and the file handle */
> if (ret != -1 || errno != EOVERFLOW) {
> fprintf(stderr, "%s: unexpected result from name_to_handle_at: %d (%m)\n", fname, ret);
> return EXIT_FAILURE;
> }
> - ret = name_to_handle_at(AT_FDCWD, fname, fh, &mntid_short, 0);
> + ret = name_to_handle_at(AT_FDCWD, fname, fh, &mntid_short, at_flags);
> }
> if (ret < 0) {
> - fprintf(stderr, "%s: name_to_handle: %m\n", fname);
> + /* No filesystem support for encoding connectable file handles (e.g. overlayfs)? */
> + if (connectable)
> + fprintf(stderr, "%s: name_to_handle_at(AT_HANDLE_CONNECTABLE) not supported by %s\n",
> + fname, errno == EINVAL ? "kernel" : "filesystem");
> + else
> + fprintf(stderr, "%s: name_to_handle: %m\n", fname);
> return EXIT_FAILURE;
> }
>
> @@ -245,8 +257,17 @@ static int check_feature(const char *feature)
> return EXIT_FAILURE;
> }
> return 0;
> + } else if (!strcmp(feature, "AT_HANDLE_CONNECTABLE")) {
> + int ret = name_to_handle_at(AT_FDCWD, ".", NULL, NULL, AT_HANDLE_CONNECTABLE);
> + /* If AT_HANDLE_CONNECTABLE is supported, we get EFAULT. */
> + if (ret < 0 && errno == EINVAL) {
> + fprintf(stderr, "name_to_handle_at(AT_HANDLE_CONNECTABLE) not supported by running kernel\n");
> + return EXIT_FAILURE;
> + }
> + return 0;
> }
>
> +
> fprintf(stderr, "unknown feature name '%s'\n", feature);
> return EXIT_FAILURE;
> }
> @@ -270,13 +291,13 @@ int main(int argc, char **argv)
> int create = 0, delete = 0, nlink = 1, move = 0;
> int rd = 0, wr = 0, wrafter = 0, parent = 0;
> int keepopen = 0, drop_caches = 1, sleep_loop = 0;
> - int force_check_mountid = 0;
> + bool force_check_mountid = 0, connectable = 0;
> int bufsz = MAX_HANDLE_SZ;
>
> if (argc < 2)
> usage();
>
> - while ((c = getopt(argc, argv, "cC:ludmMrwapknhi:o:sz")) != -1) {
> + while ((c = getopt(argc, argv, "cC:ludmMNrwapknhi:o:sz")) != -1) {
> switch (c) {
> case 'c':
> create = 1;
> @@ -313,6 +334,9 @@ int main(int argc, char **argv)
> case 'M':
> force_check_mountid = 1;
> break;
> + case 'N':
> + connectable = 1;
> + break;
> case 'p':
> parent = 1;
> break;
> @@ -445,7 +469,8 @@ int main(int argc, char **argv)
> return EXIT_FAILURE;
> }
> } else {
> - ret = do_name_to_handle_at(fname, &handle[i].fh, bufsz, force_check_mountid);
> + ret = do_name_to_handle_at(fname, &handle[i].fh, bufsz,
> + force_check_mountid, connectable);
> if (ret)
> return EXIT_FAILURE;
> }
> @@ -475,7 +500,8 @@ int main(int argc, char **argv)
> return EXIT_FAILURE;
> }
> } else {
> - ret = do_name_to_handle_at(test_dir, &dir_handle.fh, bufsz, force_check_mountid);
> + ret = do_name_to_handle_at(test_dir, &dir_handle.fh, bufsz,
> + force_check_mountid, connectable);
> if (ret)
> return EXIT_FAILURE;
> }
> @@ -589,6 +615,15 @@ int main(int argc, char **argv)
> errno = 0;
> fd = open_by_handle_at(mount_fd, &handle[i].fh, wrafter ? O_RDWR : O_RDONLY);
> if ((nlink || keepopen) && fd >= 0) {
> + char linkname[PATH_MAX];
> + char procname[64];
> + sprintf(procname, "/proc/self/fd/%i", fd);
> + int n = readlink(procname, linkname, PATH_MAX);
> +
> + /* check that fd is "connected" - that is has a non empty path */
> + if (connectable && n <= 1) {
> + printf("open_by_handle(%s) returned a disconnected fd!\n", fname);
> + }
> if (rd) {
> char buf[4] = {0};
> int size = read(fd, buf, 4);
> --
> 2.34.1
>
