Re: [PATCH 1/3] fsstress: check io_uring_queue_init errno properly

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

On Wed, Mar 06, 2024 at 05:19:33PM +0800, Zorro Lang wrote:
> As the manual of io_uring_queue_init says "io_uring_queue_init(3)
> returns 0 on success and -errno on failure". We should check if the
> return value is -ENOSYS, not the errno.

/me checks liburing source code and sees that the library returns a
negative error code without touching errno (the semi global error code
variable) at all.  That's an unfortunate quirk of the manpage, but this
code here is correct...

> Fixes: d15b1721f284 ("ltp/fsstress: don't fail on io_uring ENOSYS")
> Signed-off-by: Zorro Lang <zlang@kernel.org>
> ---
>  ltp/fsstress.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/ltp/fsstress.c b/ltp/fsstress.c
> index 63c75767..482395c4 100644
> --- a/ltp/fsstress.c
> +++ b/ltp/fsstress.c
> @@ -763,8 +763,8 @@ int main(int argc, char **argv)
>  #ifdef URING
>  			have_io_uring = true;
>  			/* If ENOSYS, just ignore uring, other errors are fatal. */
> -			if (io_uring_queue_init(URING_ENTRIES, &ring, 0)) {
> -				if (errno == ENOSYS) {
> +			if ((c = io_uring_queue_init(URING_ENTRIES, &ring, 0)) != 0) {
> +				if (c == -ENOSYS) {
>  					have_io_uring = false;
>  				} else {
>  					fprintf(stderr, "io_uring_queue_init failed\n");

But why not:

			c = io_uring_queue_init(...);
			switch (c) {
			case 0:
				have_io_uring = true;
				break;
			case -ENOSYS:
				have_io_uring = false;
				break;
			default:
				fprintf(stderr, "io_uring_queue_init failed\n");
				break;
			}

Especially since you add another case in the next patch?

I'll leave the style nits up to you though:
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D


--D

> -- 
> 2.43.0
> 
>