Re: [PATCH v3 14/25] fuse: refactor io-uring header copying to ring

[Joanne Koong <joannelkoong@gmail.com>]

On Sun, Jan 11, 2026 at 8:04 AM Bernd Schubert <bschubert@ddn.com> wrote:
>
> On 12/23/25 01:35, Joanne Koong wrote:
> > Move header copying to ring logic into a new copy_header_to_ring()
> > function. This consolidates error handling.
> >
> > Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
> > ---
> >  fs/fuse/dev_uring.c | 39 +++++++++++++++++++++------------------
> >  1 file changed, 21 insertions(+), 18 deletions(-)
> >
> > diff --git a/fs/fuse/dev_uring.c b/fs/fuse/dev_uring.c
> > index 1efee4391af5..7962a9876031 100644
> > --- a/fs/fuse/dev_uring.c
> > +++ b/fs/fuse/dev_uring.c
> > @@ -575,6 +575,18 @@ static int fuse_uring_out_header_has_err(struct fuse_out_header *oh,
> >       return err;
> >  }
> >
> > +static __always_inline int copy_header_to_ring(void __user *ring,
> > +                                            const void *header,
> > +                                            size_t header_size)
>
> Minor nit: The only part I don't like too much is the __always_inline. I
> had at least two times a debug issue where I didn't get much out of the
> trace and then used for fuse.ko

Unfortunately the __always_inline here is necessary else builds with
CONFIG_HARDENED_USERCOPY will complain because there's no metadata
visibility into the header object which means __builtin_object_size()
can't correctly determine the header size.

Thanks,
Joanne

>
> +ccflags-y += -g -O1\
> +             -fno-inline-functions \
> +             -fno-omit-frame-pointer \
> +             -fno-optimize-sibling-calls \
> +             -fno-strict-aliasing \
> +             -fno-delete-null-pointer-checks \
> +             -fno-common \
>
> After that the trace became very clear within 5min, before that I
> couldn't decode the trace.
>
> > +{
> > +     if (copy_to_user(ring, header, header_size)) {
> > +             pr_info_ratelimited("Copying header to ring failed.\n");
> > +             return -EFAULT;
> > +     }
> > +
> > +     return 0;
> > +}