Re: [PATCH v4 07/25] io_uring/kbuf: add recycling for kernel managed buffer rings

[Bernd Schubert <bernd@bsbernd.com>]

On 1/17/26 00:30, Joanne Koong wrote:
> Add an interface for buffers to be recycled back into a kernel-managed
> buffer ring.
> 
> This is a preparatory patch for fuse over io-uring.
> 
> Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
> ---
>  include/linux/io_uring/cmd.h | 11 +++++++++
>  io_uring/kbuf.c              | 44 ++++++++++++++++++++++++++++++++++++
>  2 files changed, 55 insertions(+)
> 
> diff --git a/include/linux/io_uring/cmd.h b/include/linux/io_uring/cmd.h
> index 702b1903e6ee..a488e945f883 100644
> --- a/include/linux/io_uring/cmd.h
> +++ b/include/linux/io_uring/cmd.h
> @@ -88,6 +88,10 @@ int io_uring_buf_ring_pin(struct io_uring_cmd *cmd, unsigned buf_group,
>  			  unsigned issue_flags, struct io_buffer_list **bl);
>  int io_uring_buf_ring_unpin(struct io_uring_cmd *cmd, unsigned buf_group,
>  			    unsigned issue_flags);
> +
> +int io_uring_kmbuf_recycle(struct io_uring_cmd *cmd, unsigned int buf_group,
> +			   u64 addr, unsigned int len, unsigned int bid,
> +			   unsigned int issue_flags);
>  #else
>  static inline int
>  io_uring_cmd_import_fixed(u64 ubuf, unsigned long len, int rw,
> @@ -143,6 +147,13 @@ static inline int io_uring_buf_ring_unpin(struct io_uring_cmd *cmd,
>  {
>  	return -EOPNOTSUPP;
>  }
> +static inline int io_uring_kmbuf_recycle(struct io_uring_cmd *cmd,
> +					 unsigned int buf_group, u64 addr,
> +					 unsigned int len, unsigned int bid,
> +					 unsigned int issue_flags)
> +{
> +	return -EOPNOTSUPP;
> +}
>  #endif
>  
>  static inline struct io_uring_cmd *io_uring_cmd_from_tw(struct io_tw_req tw_req)
> diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c
> index 94ab23400721..a7d7d2c6b42c 100644
> --- a/io_uring/kbuf.c
> +++ b/io_uring/kbuf.c
> @@ -102,6 +102,50 @@ void io_kbuf_drop_legacy(struct io_kiocb *req)
>  	req->kbuf = NULL;
>  }
>  
> +int io_uring_kmbuf_recycle(struct io_uring_cmd *cmd, unsigned int buf_group,
> +			   u64 addr, unsigned int len, unsigned int bid,
> +			   unsigned int issue_flags)
> +{
> +	struct io_kiocb *req = cmd_to_io_kiocb(cmd);
> +	struct io_ring_ctx *ctx = req->ctx;
> +	struct io_uring_buf_ring *br;
> +	struct io_uring_buf *buf;
> +	struct io_buffer_list *bl;
> +	int ret = -EINVAL;
> +
> +	if (WARN_ON_ONCE(req->flags & REQ_F_BUFFERS_COMMIT))
> +		return ret;
> +
> +	io_ring_submit_lock(ctx, issue_flags);
> +
> +	bl = io_buffer_get_list(ctx, buf_group);
> +
> +	if (WARN_ON_ONCE(!(bl->flags & IOBL_BUF_RING)) ||
> +	    WARN_ON_ONCE(!(bl->flags & IOBL_KERNEL_MANAGED)))
> +		goto done;

Misses "if bl"?



Thanks,
Bernd