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ublk: register buffer to local io_uring with provided buf index via UBLK_F_AUTO_BUF_REG

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Add UBLK_F_AUTO_BUF_REG for supporting to register buffer automatically
to local io_uring context with provided buffer index.

Add UAPI structure `struct ublk_auto_buf_reg` for holding user parameter
to register request buffer automatically, one 'flags' field is defined, and
there is still 32bit available for future extension, such as, adding one
io_ring FD field for registering buffer to external io_uring.

`struct ublk_auto_buf_reg` is populated from ublk uring_cmd's sqe->addr,
and all existing ublk commands are data-less, so it is just fine to reuse
sqe->addr for this purpose.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20250520045455.515691-4-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei
2025-05-20 12:54:33 +08:00
committed by Jens Axboe
parent 9e6b4756b3
commit 99c1e4eb6a
2 changed files with 113 additions and 7 deletions
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64
include/uapi/linux/ublk_cmd.h
View File

@@ -219,6 +219,29 @@
*/
#define UBLK_F_UPDATE_SIZE (1ULL << 10)
/*
* request buffer is registered automatically to uring_cmd's io_uring
* context before delivering this io command to ublk server, meantime
* it is un-registered automatically when completing this io command.
*
* For using this feature:
*
* - ublk server has to create sparse buffer table
*
* - ublk server passes auto buf register data via uring_cmd's sqe->addr,
* `struct ublk_auto_buf_reg` is populated from sqe->addr, please see
* the definition of ublk_sqe_addr_to_auto_buf_reg()
*
* - pass buffer index from `ublk_auto_buf_reg.index`
*
* - all reserved fields in `ublk_auto_buf_reg` need to be zeroed
*
* This way avoids extra cost from two uring_cmd, but also simplifies backend
* implementation, such as, the dependency on IO_REGISTER_IO_BUF and
* IO_UNREGISTER_IO_BUF becomes not necessary.
*/
#define UBLK_F_AUTO_BUF_REG (1ULL << 11)
/* device state */
#define UBLK_S_DEV_DEAD 0
#define UBLK_S_DEV_LIVE 1
@@ -339,6 +362,47 @@ static inline __u32 ublksrv_get_flags(const struct ublksrv_io_desc *iod)
return iod->op_flags >> 8;
}
struct ublk_auto_buf_reg {
/* index for registering the delivered request buffer */
__u16 index;
__u16 reserved0;
/*
* io_ring FD can be passed via the reserve field in future for
* supporting to register io buffer to external io_uring
*/
__u32 reserved1;
};
/*
* For UBLK_F_AUTO_BUF_REG, auto buffer register data is carried via
* uring_cmd's sqe->addr:
*
* - bit0 ~ bit15: buffer index
* - bit24 ~ bit31: reserved0
* - bit32 ~ bit63: reserved1
*/
static inline struct ublk_auto_buf_reg ublk_sqe_addr_to_auto_buf_reg(
__u64 sqe_addr)
{
struct ublk_auto_buf_reg reg = {
.index = sqe_addr & 0xffff,
.reserved0 = (sqe_addr >> 16) & 0xffff,
.reserved1 = sqe_addr >> 32,
};
return reg;
}
static inline __u64
ublk_auto_buf_reg_to_sqe_addr(const struct ublk_auto_buf_reg *buf)
{
__u64 addr = buf->index | (__u64)buf->reserved0 << 16 |
(__u64)buf->reserved1 << 32;
return addr;
}
/* issued to ublk driver via /dev/ublkcN */
struct ublksrv_io_cmd {
__u16 q_id;