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

Zorro Lang
2024-03-06T19:34:13Z

On Wed, Mar 06, 2024 at 07:53:57AM -0800, Darrick J. Wong wrote:
> 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...

Yeah, that confuse me too, especially some io_uring functions set errno,
some return -errno ...

>
> > 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?

Sure, that looks more clearly, I'll change this part. Thanks!

>
> I'll leave the style nits up to you though:
> Reviewed-by: Darrick J. Wong <djwong@kernel.org>
>
> --D
>
>
> --D
>
> > --
> > 2.43.0
> >
> >
>