Re: [PATCH v3 20/25] io_uring/rsrc: rename io_buffer_register_bvec()/io_buffer_unregister_bvec()

[Caleb Sander Mateos <csander@purestorage.com>]

On Mon, Dec 22, 2025 at 4:36 PM Joanne Koong <joannelkoong@gmail.com> wrote:
>
> Currently, io_buffer_register_bvec() takes in a request. In preparation
> for supporting kernel-populated buffers in fuse io-uring (which will
> need to register bvecs directly, not through a struct request), rename
> this to io_buffer_register_request().
>
> A subsequent patch will commandeer the "io_buffer_register_bvec()"
> function name to support registering bvecs directly.
>
> Rename io_buffer_unregister_bvec() to a more generic name,
> io_buffer_unregister(), as both io_buffer_register_request() and
> io_buffer_register_bvec() callers will use it for unregistration.
>
> Signed-off-by: Joanne Koong <joannelkoong@gmail.com>

Reviewed-by: Caleb Sander Mateos <csander@purestorage.com>

> ---
>  Documentation/block/ublk.rst | 14 +++++++-------
>  drivers/block/ublk_drv.c     | 18 +++++++++---------
>  include/linux/io_uring/cmd.h | 26 ++++++++++++++++++++------
>  io_uring/rsrc.c              | 14 +++++++-------
>  4 files changed, 43 insertions(+), 29 deletions(-)
>
> diff --git a/Documentation/block/ublk.rst b/Documentation/block/ublk.rst
> index 8c4030bcabb6..aa6e0bf9405b 100644
> --- a/Documentation/block/ublk.rst
> +++ b/Documentation/block/ublk.rst
> @@ -326,17 +326,17 @@ Zero copy
>  ---------
>
>  ublk zero copy relies on io_uring's fixed kernel buffer, which provides
> -two APIs: `io_buffer_register_bvec()` and `io_buffer_unregister_bvec`.
> +two APIs: `io_buffer_register_request()` and `io_buffer_unregister`.
>
>  ublk adds IO command of `UBLK_IO_REGISTER_IO_BUF` to call
> -`io_buffer_register_bvec()` for ublk server to register client request
> +`io_buffer_register_request()` for ublk server to register client request
>  buffer into io_uring buffer table, then ublk server can submit io_uring
>  IOs with the registered buffer index. IO command of `UBLK_IO_UNREGISTER_IO_BUF`
> -calls `io_buffer_unregister_bvec()` to unregister the buffer, which is
> -guaranteed to be live between calling `io_buffer_register_bvec()` and
> -`io_buffer_unregister_bvec()`. Any io_uring operation which supports this
> -kind of kernel buffer will grab one reference of the buffer until the
> -operation is completed.
> +calls `io_buffer_unregister()` to unregister the buffer, which is guaranteed
> +to be live between calling `io_buffer_register_request()` and
> +`io_buffer_unregister()`. Any io_uring operation which supports this kind of
> +kernel buffer will grab one reference of the buffer until the operation is
> +completed.
>
>  ublk server implementing zero copy or user copy has to be CAP_SYS_ADMIN and
>  be trusted, because it is ublk server's responsibility to make sure IO buffer
> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> index df9831783a13..0a42f6a75b62 100644
> --- a/drivers/block/ublk_drv.c
> +++ b/drivers/block/ublk_drv.c
> @@ -1202,8 +1202,8 @@ __ublk_do_auto_buf_reg(const struct ublk_queue *ubq, struct request *req,
>  {
>         int ret;
>
> -       ret = io_buffer_register_bvec(cmd, req, ublk_io_release,
> -                                     io->buf.auto_reg.index, issue_flags);
> +       ret = io_buffer_register_request(cmd, req, ublk_io_release,
> +                                        io->buf.auto_reg.index, issue_flags);
>         if (ret) {
>                 if (io->buf.auto_reg.flags & UBLK_AUTO_BUF_REG_FALLBACK) {
>                         ublk_auto_buf_reg_fallback(ubq, req->tag);
> @@ -2166,8 +2166,8 @@ static int ublk_register_io_buf(struct io_uring_cmd *cmd,
>         if (!req)
>                 return -EINVAL;
>
> -       ret = io_buffer_register_bvec(cmd, req, ublk_io_release, index,
> -                                     issue_flags);
> +       ret = io_buffer_register_request(cmd, req, ublk_io_release, index,
> +                                        issue_flags);
>         if (ret) {
>                 ublk_put_req_ref(io, req);
>                 return ret;
> @@ -2198,8 +2198,8 @@ ublk_daemon_register_io_buf(struct io_uring_cmd *cmd,
>         if (!ublk_dev_support_zero_copy(ub) || !ublk_rq_has_data(req))
>                 return -EINVAL;
>
> -       ret = io_buffer_register_bvec(cmd, req, ublk_io_release, index,
> -                                     issue_flags);
> +       ret = io_buffer_register_request(cmd, req, ublk_io_release, index,
> +                                        issue_flags);
>         if (ret)
>                 return ret;
>
> @@ -2214,7 +2214,7 @@ static int ublk_unregister_io_buf(struct io_uring_cmd *cmd,
>         if (!(ub->dev_info.flags & UBLK_F_SUPPORT_ZERO_COPY))
>                 return -EINVAL;
>
> -       return io_buffer_unregister_bvec(cmd, index, issue_flags);
> +       return io_buffer_unregister(cmd, index, issue_flags);
>  }
>
>  static int ublk_check_fetch_buf(const struct ublk_device *ub, __u64 buf_addr)
> @@ -2350,7 +2350,7 @@ static int ublk_ch_uring_cmd_local(struct io_uring_cmd *cmd,
>                 goto out;
>
>         /*
> -        * io_buffer_unregister_bvec() doesn't access the ubq or io,
> +        * io_buffer_unregister() doesn't access the ubq or io,
>          * so no need to validate the q_id, tag, or task
>          */
>         if (_IOC_NR(cmd_op) == UBLK_IO_UNREGISTER_IO_BUF)
> @@ -2420,7 +2420,7 @@ static int ublk_ch_uring_cmd_local(struct io_uring_cmd *cmd,
>
>                 /* can't touch 'ublk_io' any more */
>                 if (buf_idx != UBLK_INVALID_BUF_IDX)
> -                       io_buffer_unregister_bvec(cmd, buf_idx, issue_flags);
> +                       io_buffer_unregister(cmd, buf_idx, issue_flags);
>                 if (req_op(req) == REQ_OP_ZONE_APPEND)
>                         req->__sector = addr;
>                 if (compl)
> diff --git a/include/linux/io_uring/cmd.h b/include/linux/io_uring/cmd.h
> index 61c4ca863ef6..06e4cfadb344 100644
> --- a/include/linux/io_uring/cmd.h
> +++ b/include/linux/io_uring/cmd.h
> @@ -102,6 +102,12 @@ int io_uring_cmd_kmbuffer_recycle(struct io_uring_cmd *cmd,
>
>  int io_uring_cmd_is_kmbuf_ring(struct io_uring_cmd *ioucmd,
>                                unsigned int buf_group, unsigned int issue_flags);
> +
> +int io_buffer_register_request(struct io_uring_cmd *cmd, struct request *rq,
> +                              void (*release)(void *), unsigned int index,
> +                              unsigned int issue_flags);
> +int io_buffer_unregister(struct io_uring_cmd *cmd, unsigned int index,
> +                        unsigned int issue_flags);
>  #else
>  static inline int
>  io_uring_cmd_import_fixed(u64 ubuf, unsigned long len, int rw,
> @@ -185,6 +191,20 @@ static inline int io_uring_cmd_is_kmbuf_ring(struct io_uring_cmd *ioucmd,
>  {
>         return -EOPNOTSUPP;
>  }
> +static inline int io_buffer_register_request(struct io_uring_cmd *cmd,
> +                                            struct request *rq,
> +                                            void (*release)(void *),
> +                                            unsigned int index,
> +                                            unsigned int issue_flags)
> +{
> +       return -EOPNOTSUPP;
> +}
> +static inline int io_buffer_unregister(struct io_uring_cmd *cmd,
> +                                      unsigned int index,
> +                                      unsigned int issue_flags)
> +{
> +       return -EOPNOTSUPP;
> +}
>  #endif
>
>  static inline struct io_uring_cmd *io_uring_cmd_from_tw(struct io_tw_req tw_req)
> @@ -234,10 +254,4 @@ static inline void io_uring_cmd_done32(struct io_uring_cmd *ioucmd, s32 ret,
>         return __io_uring_cmd_done(ioucmd, ret, res2, issue_flags, true);
>  }
>
> -int io_buffer_register_bvec(struct io_uring_cmd *cmd, struct request *rq,
> -                           void (*release)(void *), unsigned int index,
> -                           unsigned int issue_flags);
> -int io_buffer_unregister_bvec(struct io_uring_cmd *cmd, unsigned int index,
> -                             unsigned int issue_flags);
> -
>  #endif /* _LINUX_IO_URING_CMD_H */
> diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
> index a141aaeb099d..b25b418e5c11 100644
> --- a/io_uring/rsrc.c
> +++ b/io_uring/rsrc.c
> @@ -936,9 +936,9 @@ int io_sqe_buffers_register(struct io_ring_ctx *ctx, void __user *arg,
>         return ret;
>  }
>
> -int io_buffer_register_bvec(struct io_uring_cmd *cmd, struct request *rq,
> -                           void (*release)(void *), unsigned int index,
> -                           unsigned int issue_flags)
> +int io_buffer_register_request(struct io_uring_cmd *cmd, struct request *rq,
> +                              void (*release)(void *), unsigned int index,
> +                              unsigned int issue_flags)
>  {
>         struct io_ring_ctx *ctx = cmd_to_io_kiocb(cmd)->ctx;
>         struct io_rsrc_data *data = &ctx->buf_table;
> @@ -998,10 +998,10 @@ int io_buffer_register_bvec(struct io_uring_cmd *cmd, struct request *rq,
>         io_ring_submit_unlock(ctx, issue_flags);
>         return ret;
>  }
> -EXPORT_SYMBOL_GPL(io_buffer_register_bvec);
> +EXPORT_SYMBOL_GPL(io_buffer_register_request);
>
> -int io_buffer_unregister_bvec(struct io_uring_cmd *cmd, unsigned int index,
> -                             unsigned int issue_flags)
> +int io_buffer_unregister(struct io_uring_cmd *cmd, unsigned int index,
> +                        unsigned int issue_flags)
>  {
>         struct io_ring_ctx *ctx = cmd_to_io_kiocb(cmd)->ctx;
>         struct io_rsrc_data *data = &ctx->buf_table;
> @@ -1031,7 +1031,7 @@ int io_buffer_unregister_bvec(struct io_uring_cmd *cmd, unsigned int index,
>         io_ring_submit_unlock(ctx, issue_flags);
>         return ret;
>  }
> -EXPORT_SYMBOL_GPL(io_buffer_unregister_bvec);
> +EXPORT_SYMBOL_GPL(io_buffer_unregister);
>
>  static int validate_fixed_range(u64 buf_addr, size_t len,
>                                 const struct io_mapped_ubuf *imu)
> --
> 2.47.3
>