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

[Bernd Schubert <bschubert@ddn.com>]

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

+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;
> +}
> +
>  static int fuse_uring_copy_from_ring(struct fuse_ring *ring,
>  				     struct fuse_req *req,
>  				     struct fuse_ring_ent *ent)
> @@ -637,13 +649,11 @@ static int fuse_uring_args_to_ring(struct fuse_ring *ring, struct fuse_req *req,
>  		 * Some op code have that as zero size.
>  		 */
>  		if (args->in_args[0].size > 0) {
> -			err = copy_to_user(&ent->headers->op_in, in_args->value,
> -					   in_args->size);
> -			if (err) {
> -				pr_info_ratelimited(
> -					"Copying the header failed.\n");
> -				return -EFAULT;
> -			}
> +			err = copy_header_to_ring(&ent->headers->op_in,
> +						  in_args->value,
> +						  in_args->size);
> +			if (err)
> +				return err;
>  		}
>  		in_args++;
>  		num_args--;
> @@ -659,9 +669,8 @@ static int fuse_uring_args_to_ring(struct fuse_ring *ring, struct fuse_req *req,
>  	}
>  
>  	ent_in_out.payload_sz = cs.ring.copied_sz;
> -	err = copy_to_user(&ent->headers->ring_ent_in_out, &ent_in_out,
> -			   sizeof(ent_in_out));
> -	return err ? -EFAULT : 0;
> +	return copy_header_to_ring(&ent->headers->ring_ent_in_out, &ent_in_out,
> +				   sizeof(ent_in_out));
>  }
>  
>  static int fuse_uring_copy_to_ring(struct fuse_ring_ent *ent,
> @@ -690,14 +699,8 @@ static int fuse_uring_copy_to_ring(struct fuse_ring_ent *ent,
>  	}
>  
>  	/* copy fuse_in_header */
> -	err = copy_to_user(&ent->headers->in_out, &req->in.h,
> -			   sizeof(req->in.h));
> -	if (err) {
> -		err = -EFAULT;
> -		return err;
> -	}
> -
> -	return 0;
> +	return copy_header_to_ring(&ent->headers->in_out, &req->in.h,
> +				   sizeof(req->in.h));
>  }
>  
>  static int fuse_uring_prepare_send(struct fuse_ring_ent *ent,


Reviewed-by: Bernd Schubert <bschubert@ddn.com>