Re: [PATCH xfstests v1 2/2] open_by_handle: add tests for u64 mount ID

[Amir Goldstein <amir73il@gmail.com>]

On Wed, Aug 28, 2024 at 12:37 PM Aleksa Sarai <cyphar@cyphar.com> wrote:
>
> Now that open_by_handle_at(2) can return u64 mount IDs, do some tests to
> make sure they match properly as part of the regular open_by_handle
> tests.
>
> Link: https://lore.kernel.org/all/20240801-exportfs-u64-mount-id-v3-0-be5d6283144a@cyphar.com/
> Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
> ---
>  src/open_by_handle.c | 123 ++++++++++++++++++++++++++++++++-----------
>  tests/generic/426    |   1 +
>  2 files changed, 93 insertions(+), 31 deletions(-)
>
> diff --git a/src/open_by_handle.c b/src/open_by_handle.c
> index d9c802ca9bd1..cbd68aeadac1 100644
> --- a/src/open_by_handle.c
> +++ b/src/open_by_handle.c
> @@ -86,10 +86,15 @@ Examples:
>  #include <errno.h>
>  #include <linux/limits.h>
>  #include <libgen.h>
> +#include <stdint.h>
>
>  #include <sys/stat.h>
>  #include "statx.h"
>
> +#ifndef AT_HANDLE_MNT_ID_UNIQUE
> +#      define AT_HANDLE_MNT_ID_UNIQUE 0x001
> +#endif
> +
>  #define MAXFILES 1024
>
>  struct handle {
> @@ -99,7 +104,7 @@ struct handle {
>
>  void usage(void)
>  {
> -       fprintf(stderr, "usage: open_by_handle [-cludmrwapknhs] [<-i|-o> <handles_file>] <test_dir> [num_files]\n");
> +       fprintf(stderr, "usage: open_by_handle [-cludMmrwapknhs] [<-i|-o> <handles_file>] <test_dir> [num_files]\n");
>         fprintf(stderr, "\n");
>         fprintf(stderr, "open_by_handle -c <test_dir> [N] - create N test files under test_dir, try to get file handles and exit\n");
>         fprintf(stderr, "open_by_handle    <test_dir> [N] - get file handles of test files, drop caches and try to open by handle\n");
> @@ -111,6 +116,7 @@ void usage(void)
>         fprintf(stderr, "open_by_handle -l <test_dir> [N] - create hardlinks to test files, drop caches and try to open by handle\n");
>         fprintf(stderr, "open_by_handle -u <test_dir> [N] - unlink (hardlinked) test files, drop caches and try to open by handle\n");
>         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] - confirm that the mount id returned by name_to_handle_at matches the mount id in statx\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 -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");
> @@ -120,6 +126,81 @@ void usage(void)
>         exit(EXIT_FAILURE);
>  }
>
> +int do_name_to_handle_at(const char *fname, struct file_handle *fh, int bufsz,
> +                        int checkmountid)
> +{
> +       int ret;
> +       int mntid_short;
> +
> +       uint64_t mntid_unique;
> +       uint64_t statx_mntid_short = 0, statx_mntid_unique = 0;
> +       struct handle dummy_fh;
> +
> +       if (checkmountid) {
> +               struct statx statxbuf;
> +
> +               /* Get both the short and unique mount id. */
> +               if (statx(AT_FDCWD, fname, 0, STATX_MNT_ID, &statxbuf) < 0) {
> +                       fprintf(stderr, "%s: statx(STATX_MNT_ID): %m\n", fname);
> +                       return EXIT_FAILURE;
> +               }
> +               if (!(statxbuf.stx_mask & STATX_MNT_ID)) {
> +                       fprintf(stderr, "%s: no STATX_MNT_ID in stx_mask\n", fname);
> +                       return EXIT_FAILURE;
> +               }
> +               statx_mntid_short = statxbuf.stx_mnt_id;
> +
> +               if (statx(AT_FDCWD, fname, 0, STATX_MNT_ID_UNIQUE, &statxbuf) < 0) {
> +                       fprintf(stderr, "%s: statx(STATX_MNT_ID_UNIQUE): %m\n", fname);
> +                       return EXIT_FAILURE;

This failure will break the test on LTS kernels  - we don't want that.
Instead I think you should:
- drop the -M option
- get statx_mntid_unique here IF kernel supports STATX_MNT_ID_UNIQUE
and then...

> +               }
> +               if (!(statxbuf.stx_mask & STATX_MNT_ID_UNIQUE)) {
> +                       fprintf(stderr, "%s: no STATX_MNT_ID_UNIQUE in stx_mask\n", fname);
> +                       return EXIT_FAILURE;
> +               }
> +               statx_mntid_unique = statxbuf.stx_mnt_id;
> +       }
> +
> +       fh->handle_bytes = bufsz;
> +       ret = name_to_handle_at(AT_FDCWD, fname, fh, &mntid_short, 0);
> +       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);
> +       }
> +       if (ret < 0) {
> +               fprintf(stderr, "%s: name_to_handle: %m\n", fname);
> +               return EXIT_FAILURE;
> +       }
> +
> +       if (checkmountid) {
> +               if (mntid_short != (int) statx_mntid_short) {
> +                       fprintf(stderr, "%s: name_to_handle_at returned a different mount ID to STATX_MNT_ID: %u != %lu\n", fname, mntid_short, statx_mntid_short);
> +                       return EXIT_FAILURE;
> +               }
> +
> +               /*
> +                * Get the unique mount ID. We don't need to get another copy of the
> +                * handle so store it in a dummy struct.
> +                */
> +               dummy_fh.fh.handle_bytes = fh->handle_bytes;
> +               if (name_to_handle_at(AT_FDCWD, fname, &dummy_fh.fh, (int *) &mntid_unique, AT_HANDLE_MNT_ID_UNIQUE) < 0) {
> +                       fprintf(stderr, "%s: name_to_handle_at(AT_HANDLE_MNT_ID_UNIQUE): %m\n", fname);
> +                       return EXIT_FAILURE;
> +               }
> +
> +               if (mntid_unique != statx_mntid_unique) {
> +                       fprintf(stderr, "%s: name_to_handle_at(AT_HANDLE_MNT_ID_UNIQUE) returned a different mount ID to STATX_MNT_ID_UNIQUE: %lu != %lu\n", fname, mntid_unique, statx_mntid_unique);
> +                       return EXIT_FAILURE;
> +               }

- check statx_mntid_unique here IFF statx_mntid_unique is set
- always check statx_mntid_short (what could be a reason to not check it?)

> +       }
> +
> +       return 0;
> +}
> +
>  int main(int argc, char **argv)
>  {
>         int     i, c;
> @@ -132,19 +213,20 @@ int main(int argc, char **argv)
>         char    fname2[PATH_MAX];
>         char    *test_dir;
>         char    *mount_dir;
> -       int     mount_fd, mount_id;
> +       int     mount_fd;
>         char    *infile = NULL, *outfile = NULL;
>         int     in_fd = 0, out_fd = 0;
>         int     numfiles = 1;
>         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     checkmountid = 0;
>         int     bufsz = MAX_HANDLE_SZ;
>
>         if (argc < 2)
>                 usage();
>
> -       while ((c = getopt(argc, argv, "cludmrwapknhi:o:sz")) != -1) {
> +       while ((c = getopt(argc, argv, "cludMmrwapknhi:o:sz")) != -1) {
>                 switch (c) {
>                 case 'c':
>                         create = 1;
> @@ -172,6 +254,9 @@ int main(int argc, char **argv)
>                         delete = 1;
>                         nlink = 0;
>                         break;
> +               case 'M':
> +                       checkmountid = 1;
> +                       break;
>                 case 'm':
>                         move = 1;
>                         break;
> @@ -307,21 +392,9 @@ int main(int argc, char **argv)
>                                 return EXIT_FAILURE;
>                         }
>                 } else {
> -                       handle[i].fh.handle_bytes = bufsz;
> -                       ret = name_to_handle_at(AT_FDCWD, fname, &handle[i].fh, &mount_id, 0);
> -                       if (bufsz < handle[i].fh.handle_bytes) {
> -                               /* Query the filesystem required bufsz and the file handle */
> -                               if (ret != -1 || errno != EOVERFLOW) {
> -                                       fprintf(stderr, "Unexpected result from name_to_handle_at(%s)\n", fname);
> -                                       return EXIT_FAILURE;
> -                               }
> -                               ret = name_to_handle_at(AT_FDCWD, fname, &handle[i].fh, &mount_id, 0);
> -                       }
> -                       if (ret < 0) {
> -                               strcat(fname, ": name_to_handle");
> -                               perror(fname);
> +                       ret = do_name_to_handle_at(fname, &handle[i].fh, bufsz, checkmountid);
> +                       if (ret < 0)
>                                 return EXIT_FAILURE;
> -                       }
>                 }
>                 if (keepopen) {
>                         /* Open without close to keep unlinked files around */
> @@ -349,21 +422,9 @@ int main(int argc, char **argv)
>                                 return EXIT_FAILURE;
>                         }
>                 } else {
> -                       dir_handle.fh.handle_bytes = bufsz;
> -                       ret = name_to_handle_at(AT_FDCWD, test_dir, &dir_handle.fh, &mount_id, 0);
> -                       if (bufsz < dir_handle.fh.handle_bytes) {
> -                               /* Query the filesystem required bufsz and the file handle */
> -                               if (ret != -1 || errno != EOVERFLOW) {
> -                                       fprintf(stderr, "Unexpected result from name_to_handle_at(%s)\n", dname);
> -                                       return EXIT_FAILURE;
> -                               }
> -                               ret = name_to_handle_at(AT_FDCWD, test_dir, &dir_handle.fh, &mount_id, 0);
> -                       }
> -                       if (ret < 0) {
> -                               strcat(dname, ": name_to_handle");
> -                               perror(dname);
> +                       ret = do_name_to_handle_at(test_dir, &dir_handle.fh, bufsz, checkmountid);
> +                       if (ret < 0)
>                                 return EXIT_FAILURE;
> -                       }
>                 }
>                 if (out_fd) {
>                         ret = write(out_fd, (char *)&dir_handle, sizeof(*handle));
> diff --git a/tests/generic/426 b/tests/generic/426
> index 25909f220e1e..df481c58562c 100755
> --- a/tests/generic/426
> +++ b/tests/generic/426
> @@ -51,6 +51,7 @@ test_file_handles $testdir -d
>  # Check non-stale handles to linked files
>  create_test_files $testdir
>  test_file_handles $testdir
> +test_file_handles $testdir -M

I see no reason to add option -M and add a second invocation.

Something I am missing?

Thanks,
Amir.