Re: [PATCH v2] generic/791: don't run if kernel misses FANOTIFY

["Darrick J. Wong" <djwong@kernel.org>]

On Thu, May 21, 2026 at 10:26:46AM +0200, Andrey Albershteyn wrote:
> If FANOTIFY=no in the kernel, then fs-monitor will fail to start. Fix
> fs-monitor error codes to detect and skip the test on "Function not
> implemented" code.
> 
> Signed-off-by: Andrey Albershteyn <aalbersh@kernel.org>
> ---
> Changes from v1:
> - Remove returning of errno
> - Instead of checking for error code add new -c argument to fs-monitor

Looks good to me now!
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> 
> ---
>  src/fs-monitor.c  | 19 ++++++++++++++++++-
>  tests/generic/791 |  3 +++
>  2 files changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/src/fs-monitor.c b/src/fs-monitor.c
> index 0cf09677a3ef..dd91a5d7f623 100644
> --- a/src/fs-monitor.c
> +++ b/src/fs-monitor.c
> @@ -117,6 +117,8 @@ next_event:
>  int main(int argc, char **argv)
>  {
>  	int fd;
> +	int opt;
> +	int check = 0;
>  
>  	char buffer[BUFSIZ];
>  
> @@ -125,14 +127,29 @@ int main(int argc, char **argv)
>  		return 1;
>  	}
>  
> +	while ((opt = getopt(argc, argv, "c")) != -1) {
> +		switch (opt) {
> +		case 'c':
> +			check = 1;
> +			break;
> +		default:
> +			fprintf(stderr, "Usage: %s [-c] path\n",
> +				argv[0]);
> +			exit(EXIT_FAILURE);
> +		}
> +	}
> +
>  	fd = fanotify_init(FAN_CLASS_NOTIF|FAN_REPORT_FID, O_RDONLY);
> +	if (check)
> +		exit(fd < 0);
> +
>  	if (fd < 0) {
>  		perror("fanotify_init");
>  		errx(1, "fanotify_init");
>  	}
>  
>  	if (fanotify_mark(fd, FAN_MARK_ADD|FAN_MARK_FILESYSTEM,
> -			  FAN_FS_ERROR, AT_FDCWD, argv[1])) {
> +			  FAN_FS_ERROR, AT_FDCWD, argv[optind])) {
>  		perror("fanotify_mark");
>  		errx(1, "fanotify_mark");
>  	}
> diff --git a/tests/generic/791 b/tests/generic/791
> index 90242292cba2..edefbb7767c3 100755
> --- a/tests/generic/791
> +++ b/tests/generic/791
> @@ -65,6 +65,9 @@ _dmerror_mount >> $seqres.full 2>&1
>  
>  test $FSTYP = xfs && _xfs_force_bdev data $SCRATCH_MNT
>  
> +$here/src/fs-monitor -c $SCRATCH_MNT &> /dev/null || \
> +		_notrun "fanotify too old"
> +
>  # Write a file with 4 file blocks worth of data, figure out the LBA to target
>  victim=$SCRATCH_MNT/a
>  file_blksz=$(_get_file_block_size $SCRATCH_MNT)
> -- 
> 2.51.2
>