Re: [PATCH] ltp/fsstress: don't fail on io_uring ENOSYS

[Zorro Lang <zlang@redhat.com>]

On Thu, Jan 28, 2021 at 03:31:40PM -0600, Eric Sandeen wrote:
> We might have URING #defined at build time, but be running on a kernel
> which does not support it.
> 
> For that reason, we should not exit with an error if 
> io_uring_queue_init() fails with ENOSYS. We can just note the lack of
> support and skip all future io_uring operations.
> 
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
> ---
> 
> diff --git a/ltp/fsstress.c b/ltp/fsstress.c
> index 22df5e38..73751935 100644
> --- a/ltp/fsstress.c
> +++ b/ltp/fsstress.c
> @@ -35,6 +35,7 @@ io_context_t	io_ctx;
>  #include <liburing.h>
>  #define URING_ENTRIES	1
>  struct io_uring	ring;
> +bool have_io_uring;			/* to indicate runtime availability */
>  #endif
>  #include <sys/syscall.h>
>  #include <sys/xattr.h>
> @@ -706,9 +707,15 @@ int main(int argc, char **argv)
>  			}
>  #endif
>  #ifdef URING
> +			have_io_uring = true;
> +			/* If ENOSYS, just ignore uring, other errors are fatal. */

Yes, I thought about if we should do this since rhel8 kernel removed io_uring
support from kernel, but left userspace liburing. But if we do this for io_uring,
should we do the same check the others which can be disabled from kernel? Likes: AIO?

Thanks,
Zorro

>  			if (io_uring_queue_init(URING_ENTRIES, &ring, 0)) {
> -				fprintf(stderr, "io_uring_queue_init failed\n");
> -				exit(1);
> +				if (errno == ENOSYS) {
> +					have_io_uring = false;
> +				} else {
> +					fprintf(stderr, "io_uring_queue_init failed\n");
> +					exit(1);
> +				}
>  			}
>  #endif
>  			for (i = 0; !loops || (i < loops); i++)
> @@ -720,7 +727,8 @@ int main(int argc, char **argv)
>  			}
>  #endif
>  #ifdef URING
> -			io_uring_queue_exit(&ring);
> +			if (have_io_uring)
> +				io_uring_queue_exit(&ring);
>  #endif
>  			cleanup_flist();
>  			free(freq_table);
> @@ -2208,6 +2216,9 @@ do_uring_rw(int opno, long r, int flags)
>  	struct iovec	iovec;
>  	int		iswrite = (flags & (O_WRONLY | O_RDWR)) ? 1 : 0;
>  
> +	if (!have_io_uring)
> +		return;
> +
>  	init_pathname(&f);
>  	if (!get_fname(FT_REGFILE, r, &f, NULL, NULL, &v)) {
>  		if (v)
>