[LTP] [PATCH] fanotify: Fix broken tests due to fanotify_events_supported_by_kernel()

[Amir Goldstein]

On Mon, Nov 27, 2023 at 5:40 PM Jan Kara <jack@suse.cz> wrote:
>
> When LTP test is run with CWD in btrfs subvolume, tests like fanotify16
> fail with:
>
> fanotify.h:169: TBROK: fanotify_mark (3, FAN_MARK_ADD, ..., AT_FDCWD, ".") failed: EXDEV (18)
>
> This is because fanotify_events_supported_by_kernel() try to place a
> mark onto CWD and that is forbidden for btrfs subvolumes. Change
> fanotify_events_supported_by_kernel() to use "/" instead of "." which
> has higher chances of working for btrfs.
>

FWIW, "." in setup() is usually a tempdir (under LTP temp root)
So I'm not sure that "/" is a better choice than ".".
At least the LTP temp dir is configurable.
and no reason that "/" is not a btrfs subvol inside a container...

FYI, in this branch:
https://github.com/amir73il/ltp/commits/fanotify_fsid

I have already implemented fanotify_flags_supported_on_fs()
which can be used to test support for an event/mark on a specific path.

I did not make the change in fanotify16.c to use
fanotify_flags_supported_on_fs() instead of
fanotify_{mark,events}_supported_by_kernel() but it would be trivial to do.

Thanks,
Amir.



> Also update the error message to provide a bit more info.
>
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
>  testcases/kernel/syscalls/fanotify/fanotify.h | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/testcases/kernel/syscalls/fanotify/fanotify.h b/testcases/kernel/syscalls/fanotify/fanotify.h
> index 32b510cdc178..f2fe0c05b449 100644
> --- a/testcases/kernel/syscalls/fanotify/fanotify.h
> +++ b/testcases/kernel/syscalls/fanotify/fanotify.h
> @@ -161,12 +161,13 @@ static inline int fanotify_events_supported_by_kernel(uint64_t mask,
>
>         fd = SAFE_FANOTIFY_INIT(init_flags, O_RDONLY);
>
> -       if (fanotify_mark(fd, FAN_MARK_ADD | mark_flags, mask, AT_FDCWD, ".") < 0) {
> +       if (fanotify_mark(fd, FAN_MARK_ADD | mark_flags, mask, AT_FDCWD, "/") < 0) {
>                 if (errno == EINVAL) {
>                         rval = -1;
>                 } else {
>                         tst_brk(TBROK | TERRNO,
> -                               "fanotify_mark (%d, FAN_MARK_ADD, ..., AT_FDCWD, \".\") failed", fd);
> +                               "fanotify_mark (%d, FAN_MARK_ADD | %x, %llx, AT_FDCWD, \".\") failed",
> +                               fd, mark_flags, (unsigned long long)mask);
>                 }
>         }
>
> --
> 2.35.3
>