ublk_cmd.h

/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
#ifndef USER_BLK_DRV_CMD_INC_H
#define USER_BLK_DRV_CMD_INC_H
 
#include <linux/types.h>
 
/* ublk server command definition */
 
/*
 * Admin commands, issued by ublk server, and handled by ublk driver.
 *
 * Legacy command definition, don't use in new application, and don't
 * add new such definition any more
 */
#define UBLK_CMD_GET_QUEUE_AFFINITY 0x01
#define UBLK_CMD_GET_DEV_INFO   0x02
#define UBLK_CMD_ADD_DEV        0x04
#define UBLK_CMD_DEL_DEV        0x05
#define UBLK_CMD_START_DEV  0x06
#define UBLK_CMD_STOP_DEV   0x07
#define UBLK_CMD_SET_PARAMS 0x08
#define UBLK_CMD_GET_PARAMS 0x09
#define UBLK_CMD_START_USER_RECOVERY    0x10
#define UBLK_CMD_END_USER_RECOVERY  0x11
#define UBLK_CMD_GET_DEV_INFO2      0x12
 
/* Any new ctrl command should encode by __IO*() */
#define UBLK_U_CMD_GET_QUEUE_AFFINITY   \
    _IOR('u', UBLK_CMD_GET_QUEUE_AFFINITY, struct ublksrv_ctrl_cmd)
#define UBLK_U_CMD_GET_DEV_INFO     \
    _IOR('u', UBLK_CMD_GET_DEV_INFO, struct ublksrv_ctrl_cmd)
#define UBLK_U_CMD_ADD_DEV      \
    _IOWR('u', UBLK_CMD_ADD_DEV, struct ublksrv_ctrl_cmd)
#define UBLK_U_CMD_DEL_DEV      \
    _IOWR('u', UBLK_CMD_DEL_DEV, struct ublksrv_ctrl_cmd)
#define UBLK_U_CMD_START_DEV        \
    _IOWR('u', UBLK_CMD_START_DEV, struct ublksrv_ctrl_cmd)
#define UBLK_U_CMD_STOP_DEV     \
    _IOWR('u', UBLK_CMD_STOP_DEV, struct ublksrv_ctrl_cmd)
#define UBLK_U_CMD_SET_PARAMS       \
    _IOWR('u', UBLK_CMD_SET_PARAMS, struct ublksrv_ctrl_cmd)
#define UBLK_U_CMD_GET_PARAMS       \
    _IOR('u', UBLK_CMD_GET_PARAMS, struct ublksrv_ctrl_cmd)
#define UBLK_U_CMD_START_USER_RECOVERY  \
    _IOWR('u', UBLK_CMD_START_USER_RECOVERY, struct ublksrv_ctrl_cmd)
#define UBLK_U_CMD_END_USER_RECOVERY    \
    _IOWR('u', UBLK_CMD_END_USER_RECOVERY, struct ublksrv_ctrl_cmd)
#define UBLK_U_CMD_GET_DEV_INFO2    \
    _IOR('u', UBLK_CMD_GET_DEV_INFO2, struct ublksrv_ctrl_cmd)
#define UBLK_U_CMD_GET_FEATURES \
    _IOR('u', 0x13, struct ublksrv_ctrl_cmd)
#define UBLK_U_CMD_DEL_DEV_ASYNC    \
    _IOR('u', 0x14, struct ublksrv_ctrl_cmd)
#define UBLK_U_CMD_UPDATE_SIZE      \
    _IOWR('u', 0x15, struct ublksrv_ctrl_cmd)
#define UBLK_U_CMD_QUIESCE_DEV      \
    _IOWR('u', 0x16, struct ublksrv_ctrl_cmd)
#define UBLK_U_CMD_TRY_STOP_DEV     \
    _IOWR('u', 0x17, struct ublksrv_ctrl_cmd)
/*
 * Register a shared memory buffer for zero-copy I/O.
 * Input:  ctrl_cmd.addr points to struct ublk_shmem_buf_reg (buffer VA + size)
 *         ctrl_cmd.len  = sizeof(struct ublk_shmem_buf_reg)
 * Result: >= 0 is the assigned buffer index, < 0 is error
 *
 * The kernel pins pages from the calling process's address space
 * and inserts PFN ranges into a per-device maple tree. When a block
 * request's pages match registered pages, the driver sets
 * UBLK_IO_F_SHMEM_ZC and encodes the buffer index + offset in addr,
 * allowing the server to access the data via its own mapping of the
 * same shared memory — true zero copy.
 *
 * The memory can be backed by memfd, hugetlbfs, or any GUP-compatible
 * shared mapping. Queue freeze is handled internally.
 *
 * The buffer VA and size are passed via a user buffer (not inline in
 * ctrl_cmd) so that unprivileged devices can prepend the device path
 * to ctrl_cmd.addr without corrupting the VA.
 */
#define UBLK_U_CMD_REG_BUF      \
    _IOWR('u', 0x18, struct ublksrv_ctrl_cmd)
/*
 * Unregister a shared memory buffer.
 * Input:  ctrl_cmd.data[0] = buffer index
 */
#define UBLK_U_CMD_UNREG_BUF        \
    _IOWR('u', 0x19, struct ublksrv_ctrl_cmd)
 
/* Parameter buffer for UBLK_U_CMD_REG_BUF, pointed to by ctrl_cmd.addr */
struct ublk_shmem_buf_reg {
    __u64   addr;   /* userspace virtual address of shared memory */
    __u64   len;    /* buffer size in bytes, page-aligned, default max 4GB */
    __u32   flags;
    __u32   reserved;
};
 
/* Pin pages without FOLL_WRITE; usable with write-sealed memfd */
#define UBLK_SHMEM_BUF_READ_ONLY    (1U << 0)
/*
 * 64bits are enough now, and it should be easy to extend in case of
 * running out of feature flags
 */
#define UBLK_FEATURES_LEN  8
 
/*
 * IO commands, issued by ublk server, and handled by ublk driver.
 *
 * FETCH_REQ: issued via sqe(URING_CMD) beforehand for fetching IO request
 *      from ublk driver, should be issued only when starting device. After
 *      the associated cqe is returned, request's tag can be retrieved via
 *      cqe->userdata.
 *
 * COMMIT_AND_FETCH_REQ: issued via sqe(URING_CMD) after ublkserver handled
 *      this IO request, request's handling result is committed to ublk
 *      driver, meantime FETCH_REQ is piggyback, and FETCH_REQ has to be
 *      handled before completing io request.
 *
 * NEED_GET_DATA: only used for write requests to set io addr and copy data
 *      When NEED_GET_DATA is set, ublksrv has to issue UBLK_IO_NEED_GET_DATA
 *      command after ublk driver returns UBLK_IO_RES_NEED_GET_DATA.
 *
 *      It is only used if ublksrv set UBLK_F_NEED_GET_DATA flag
 *      while starting a ublk device.
 */
 
/*
 * Legacy IO command definition, don't use in new application, and don't
 * add new such definition any more
 */
#define UBLK_IO_FETCH_REQ       0x20
#define UBLK_IO_COMMIT_AND_FETCH_REQ    0x21
#define UBLK_IO_NEED_GET_DATA   0x22
 
/* Any new IO command should encode by __IOWR() */
#define UBLK_U_IO_FETCH_REQ     \
    _IOWR('u', UBLK_IO_FETCH_REQ, struct ublksrv_io_cmd)
#define UBLK_U_IO_COMMIT_AND_FETCH_REQ  \
    _IOWR('u', UBLK_IO_COMMIT_AND_FETCH_REQ, struct ublksrv_io_cmd)
#define UBLK_U_IO_NEED_GET_DATA     \
    _IOWR('u', UBLK_IO_NEED_GET_DATA, struct ublksrv_io_cmd)
#define UBLK_U_IO_REGISTER_IO_BUF   \
    _IOWR('u', 0x23, struct ublksrv_io_cmd)
#define UBLK_U_IO_UNREGISTER_IO_BUF \
    _IOWR('u', 0x24, struct ublksrv_io_cmd)
 
/*
 * return 0 if the command is run successfully, otherwise failure code
 * is returned
 */
#define UBLK_U_IO_PREP_IO_CMDS  \
    _IOWR('u', 0x25, struct ublk_batch_io)
/*
 * If failure code is returned, nothing in the command buffer is handled.
 * Otherwise, the returned value means how many bytes in command buffer
 * are handled actually, then number of handled IOs can be calculated with
 * `elem_bytes` for each IO. IOs in the remained bytes are not committed,
 * userspace has to check return value for dealing with partial committing
 * correctly.
 */
#define UBLK_U_IO_COMMIT_IO_CMDS    \
    _IOWR('u', 0x26, struct ublk_batch_io)
 
/*
 * Fetch io commands to provided buffer in multishot style,
 * `IORING_URING_CMD_MULTISHOT` is required for this command.
 */
#define UBLK_U_IO_FETCH_IO_CMDS     \
    _IOWR('u', 0x27, struct ublk_batch_io)
 
/* only ABORT means that no re-fetch */
#define UBLK_IO_RES_OK          0
#define UBLK_IO_RES_NEED_GET_DATA   1
#define UBLK_IO_RES_ABORT       (-ENODEV)
 
#define UBLKSRV_CMD_BUF_OFFSET  0
#define UBLKSRV_IO_BUF_OFFSET   0x80000000
 
/* tag bit is 16bit, so far limit at most 4096 IOs for each queue */
#define UBLK_MAX_QUEUE_DEPTH    4096
 
/* single IO buffer max size is 32MB */
#define UBLK_IO_BUF_OFF     0
#define UBLK_IO_BUF_BITS    25
#define UBLK_IO_BUF_BITS_MASK   ((1ULL << UBLK_IO_BUF_BITS) - 1)
 
/* so at most 64K IOs for each queue */
#define UBLK_TAG_OFF        UBLK_IO_BUF_BITS
#define UBLK_TAG_BITS       16
#define UBLK_TAG_BITS_MASK  ((1ULL << UBLK_TAG_BITS) - 1)
 
/* max 4096 queues */
#define UBLK_QID_OFF        (UBLK_TAG_OFF + UBLK_TAG_BITS)
#define UBLK_QID_BITS       12
#define UBLK_QID_BITS_MASK  ((1ULL << UBLK_QID_BITS) - 1)
 
#define UBLK_MAX_NR_QUEUES  (1U << UBLK_QID_BITS)
 
#define UBLKSRV_IO_BUF_TOTAL_BITS   (UBLK_QID_OFF + UBLK_QID_BITS)
#define UBLKSRV_IO_BUF_TOTAL_SIZE   (1ULL << UBLKSRV_IO_BUF_TOTAL_BITS)
 
/* Copy to/from request integrity buffer instead of data buffer */
#define UBLK_INTEGRITY_FLAG_OFF 62
#define UBLKSRV_IO_INTEGRITY_FLAG (1ULL << UBLK_INTEGRITY_FLAG_OFF)
 
/*
 * ublk server can register data buffers for incoming I/O requests with a sparse
 * io_uring buffer table. The request buffer can then be used as the data buffer
 * for io_uring operations via the fixed buffer index.
 * Note that the ublk server can never directly access the request data memory.
 *
 * To use this feature, the ublk server must first register a sparse buffer
 * table on an io_uring instance.
 * When an incoming ublk request is received, the ublk server submits a
 * UBLK_U_IO_REGISTER_IO_BUF command to that io_uring instance. The
 * ublksrv_io_cmd's q_id and tag specify the request whose buffer to register
 * and addr is the index in the io_uring's buffer table to install the buffer.
 * SQEs can now be submitted to the io_uring to read/write the request's buffer
 * by enabling fixed buffers (e.g. using IORING_OP_{READ,WRITE}_FIXED or
 * IORING_URING_CMD_FIXED) and passing the registered buffer index in buf_index.
 * Once the last io_uring operation using the request's buffer has completed,
 * the ublk server submits a UBLK_U_IO_UNREGISTER_IO_BUF command with q_id, tag,
 * and addr again specifying the request buffer to unregister.
 * The ublk request is completed when its buffer is unregistered from all
 * io_uring instances and the ublk server issues UBLK_U_IO_COMMIT_AND_FETCH_REQ.
 *
 * Not available for UBLK_F_UNPRIVILEGED_DEV, as a ublk server can leak
 * uninitialized kernel memory by not reading into the full request buffer.
 */
#define UBLK_F_SUPPORT_ZERO_COPY    (1ULL << 0)
 
/*
 * Force to complete io cmd via io_uring_cmd_complete_in_task so that
 * performance comparison is done easily with using task_work_add
 */
#define UBLK_F_URING_CMD_COMP_IN_TASK   (1ULL << 1)
 
/*
 * User should issue io cmd again for write requests to
 * set io buffer address and copy data from bio vectors
 * to the userspace io buffer.
 *
 * In this mode, task_work is not used.
 */
#define UBLK_F_NEED_GET_DATA (1UL << 2)
 
/*
 * - Block devices are recoverable if ublk server exits and restarts
 * - Outstanding I/O when ublk server exits is met with errors
 * - I/O issued while there is no ublk server queues
 */
#define UBLK_F_USER_RECOVERY    (1UL << 3)
 
/*
 * - Block devices are recoverable if ublk server exits and restarts
 * - Outstanding I/O when ublk server exits is reissued
 * - I/O issued while there is no ublk server queues
 */
#define UBLK_F_USER_RECOVERY_REISSUE    (1UL << 4)
 
/*
 * Unprivileged user can create /dev/ublkcN and /dev/ublkbN.
 *
 * /dev/ublk-control needs to be available for unprivileged user, and it
 * can be done via udev rule to make all control commands available to
 * unprivileged user. Except for the command of UBLK_CMD_ADD_DEV, all
 * other commands are only allowed for the owner of the specified device.
 *
 * When userspace sends UBLK_CMD_ADD_DEV, the device pair's owner_uid and
 * owner_gid are stored to ublksrv_ctrl_dev_info by kernel, so far only
 * the current user's uid/gid is stored, that said owner of the created
 * device is always the current user.
 *
 * We still need udev rule to apply OWNER/GROUP with the stored owner_uid
 * and owner_gid.
 *
 * Then ublk server can be run as unprivileged user, and /dev/ublkbN can
 * be accessed and managed by its owner represented by owner_uid/owner_gid.
 */
#define UBLK_F_UNPRIVILEGED_DEV (1UL << 5)
 
/* use ioctl encoding for uring command */
#define UBLK_F_CMD_IOCTL_ENCODE (1UL << 6)
 
/*
 *  Copy between request and user buffer by pread()/pwrite()
 *
 *  Not available for UBLK_F_UNPRIVILEGED_DEV, otherwise userspace may
 *  deceive us by not filling request buffer, then kernel uninitialized
 *  data may be leaked.
 */
#define UBLK_F_USER_COPY    (1UL << 7)
 
/*
 * User space sets this flag when setting up the device to request zoned storage support. Kernel may
 * deny the request by returning an error.
 */
#define UBLK_F_ZONED (1ULL << 8)
 
/*
 * - Block devices are recoverable if ublk server exits and restarts
 * - Outstanding I/O when ublk server exits is met with errors
 * - I/O issued while there is no ublk server is met with errors
 */
#define UBLK_F_USER_RECOVERY_FAIL_IO (1ULL << 9)
 
/*
 * Resizing a block device is possible with UBLK_U_CMD_UPDATE_SIZE
 * New size is passed in cmd->data[0] and is in units of sectors
 */
#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 on the same `io_ring_ctx`
 *   for issuing `UBLK_IO_FETCH_REQ` and `UBLK_IO_COMMIT_AND_FETCH_REQ`.
 *   If uring_cmd isn't issued on same `io_ring_ctx`, it is ublk server's
 *   responsibility to unregister the buffer by issuing `IO_UNREGISTER_IO_BUF`
 *   manually, otherwise this ublk request won't complete.
 *
 * - 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
 *
 * - pass flags from `ublk_auto_buf_reg.flags` if needed
 *
 * 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.
 *
 * If wrong data or flags are provided, both IO_FETCH_REQ and
 * IO_COMMIT_AND_FETCH_REQ are failed, for the latter, the ublk IO request
 * won't be completed until new IO_COMMIT_AND_FETCH_REQ command is issued
 * successfully
 */
#define UBLK_F_AUTO_BUF_REG     (1ULL << 11)
 
/*
 * Control command `UBLK_U_CMD_QUIESCE_DEV` is added for quiescing device,
 * which state can be transitioned to `UBLK_S_DEV_QUIESCED` or
 * `UBLK_S_DEV_FAIL_IO` finally, and it needs ublk server cooperation for
 * handling `UBLK_IO_RES_ABORT` correctly.
 *
 * Typical use case is for supporting to upgrade ublk server application,
 * meantime keep ublk block device persistent during the period.
 *
 * This feature is only available when UBLK_F_USER_RECOVERY is enabled.
 *
 * Note, this command returns -EBUSY in case that all IO commands are being
 * handled by ublk server and not completed in specified time period which
 * is passed from the control command parameter.
 */
#define UBLK_F_QUIESCE      (1ULL << 12)
 
/*
 * If this feature is set, ublk_drv supports each (qid,tag) pair having
 * its own independent daemon task that is responsible for handling it.
 * If it is not set, daemons are per-queue instead, so for two pairs
 * (qid1,tag1) and (qid2,tag2), if qid1 == qid2, then the same task must
 * be responsible for handling (qid1,tag1) and (qid2,tag2).
 */
#define UBLK_F_PER_IO_DAEMON (1ULL << 13)
 
/*
 * If this feature is set, UBLK_U_IO_REGISTER_IO_BUF/UBLK_U_IO_UNREGISTER_IO_BUF
 * can be issued for an I/O on any task. q_id and tag are also ignored in
 * UBLK_U_IO_UNREGISTER_IO_BUF's ublksrv_io_cmd.
 * If it is unset, zero-copy buffers can only be registered and unregistered by
 * the I/O's daemon task. The q_id and tag of the registered buffer are required
 * in UBLK_U_IO_UNREGISTER_IO_BUF's ublksrv_io_cmd.
 */
#define UBLK_F_BUF_REG_OFF_DAEMON (1ULL << 14)
 
/*
 * Support the following commands for delivering & committing io command
 * in batch.
 *
 *  - UBLK_U_IO_PREP_IO_CMDS
 *  - UBLK_U_IO_COMMIT_IO_CMDS
 *  - UBLK_U_IO_FETCH_IO_CMDS
 *  - UBLK_U_IO_REGISTER_IO_BUF
 *  - UBLK_U_IO_UNREGISTER_IO_BUF
 *
 * The existing UBLK_U_IO_FETCH_REQ, UBLK_U_IO_COMMIT_AND_FETCH_REQ and
 * UBLK_U_IO_NEED_GET_DATA uring_cmd are not supported for this feature.
 */
#define UBLK_F_BATCH_IO     (1ULL << 15)
 
/*
 * ublk device supports requests with integrity/metadata buffer.
 * Requires UBLK_F_USER_COPY.
 */
#define UBLK_F_INTEGRITY (1ULL << 16)
 
/*
 * The device supports the UBLK_CMD_TRY_STOP_DEV command, which
 * allows stopping the device only if there are no openers.
 */
#define UBLK_F_SAFE_STOP_DEV    (1ULL << 17)
 
/* Disable automatic partition scanning when device is started */
#define UBLK_F_NO_AUTO_PART_SCAN (1ULL << 18)
 
/*
 * Enable shared memory zero copy. When enabled, the server can register
 * shared memory buffers via UBLK_U_CMD_REG_BUF. If a block request's
 * pages match a registered buffer, UBLK_IO_F_SHMEM_ZC is set and addr
 * encodes the buffer index + offset instead of a userspace buffer address.
 */
#define UBLK_F_SHMEM_ZC (1ULL << 19)
 
/* ublksrv_io_desc size is specified by ublksrv_ctrl_dev_info's io_desc_size */
#define UBLK_F_IO_DESC_SIZE (1ULL << 20)
 
/* device state */
#define UBLK_S_DEV_DEAD 0
#define UBLK_S_DEV_LIVE 1
#define UBLK_S_DEV_QUIESCED 2
#define UBLK_S_DEV_FAIL_IO  3
 
/* shipped via sqe->cmd of io_uring command */
struct ublksrv_ctrl_cmd {
    /* sent to which device, must be valid */
    __u32   dev_id;
 
    /* sent to which queue, must be -1 if the cmd isn't for queue */
    __u16   queue_id;
    /*
     * cmd specific buffer, can be IN or OUT.
     */
    __u16   len;
    __u64   addr;
 
    /* inline data */
    __u64   data[1];
 
    /*
     * Used for UBLK_F_UNPRIVILEGED_DEV and UBLK_CMD_GET_DEV_INFO2
     * only, include null char
     */
    __u16   dev_path_len;
    __u16   pad;
    __u32   reserved;
};
 
struct ublksrv_ctrl_dev_info {
    __u16   nr_hw_queues;
    __u16   queue_depth;
    __u16   state;
    __u16   io_desc_size;
 
    __u32   max_io_buf_bytes;
    __u32   dev_id;
 
    __s32   ublksrv_pid;
    __u32   pad1;
 
    __u64   flags;
 
    /* For ublksrv internal use, invisible to ublk driver */
    __u64   ublksrv_flags;
 
    __u32   owner_uid;  /* store by kernel */
    __u32   owner_gid;  /* store by kernel */
    __u64   reserved1;
    __u64   reserved2;
};
 
#define     UBLK_IO_OP_READ     0
#define     UBLK_IO_OP_WRITE        1
#define     UBLK_IO_OP_FLUSH        2
#define     UBLK_IO_OP_DISCARD      3
#define     UBLK_IO_OP_WRITE_SAME       4
#define     UBLK_IO_OP_WRITE_ZEROES     5
#define     UBLK_IO_OP_ZONE_OPEN        10
#define     UBLK_IO_OP_ZONE_CLOSE       11
#define     UBLK_IO_OP_ZONE_FINISH      12
#define     UBLK_IO_OP_ZONE_APPEND      13
#define     UBLK_IO_OP_ZONE_RESET_ALL   14
#define     UBLK_IO_OP_ZONE_RESET       15
/*
 * Construct a zone report. The report request is carried in `struct
 * ublksrv_io_desc`. The `start_sector` field must be the first sector of a zone
 * and shall indicate the first zone of the report. The `nr_zones` shall
 * indicate how many zones should be reported at most. The report shall be
 * delivered as a `struct blk_zone` array. To report fewer zones than requested,
 * zero the last entry of the returned array.
 *
 * Related definitions(blk_zone, blk_zone_cond, blk_zone_type, ...) in
 * include/uapi/linux/blkzoned.h are part of ublk UAPI.
 */
#define     UBLK_IO_OP_REPORT_ZONES     18
 
#define     UBLK_IO_F_FAILFAST_DEV      (1U << 8)
#define     UBLK_IO_F_FAILFAST_TRANSPORT    (1U << 9)
#define     UBLK_IO_F_FAILFAST_DRIVER   (1U << 10)
#define     UBLK_IO_F_META          (1U << 11)
#define     UBLK_IO_F_FUA           (1U << 13)
#define     UBLK_IO_F_NOUNMAP       (1U << 15)
#define     UBLK_IO_F_SWAP          (1U << 16)
/*
 * For UBLK_F_AUTO_BUF_REG & UBLK_AUTO_BUF_REG_FALLBACK only.
 *
 * This flag is set if auto buffer register is failed & ublk server passes
 * UBLK_AUTO_BUF_REG_FALLBACK, and ublk server need to register buffer
 * manually for handling the delivered IO command if this flag is observed
 *
 * ublk server has to check this flag if UBLK_AUTO_BUF_REG_FALLBACK is
 * passed in.
 */
#define     UBLK_IO_F_NEED_REG_BUF      (1U << 17)
/* Request has an integrity data buffer */
#define     UBLK_IO_F_INTEGRITY     (1UL << 18)
/*
 * I/O buffer is in a registered shared memory buffer. When set, the addr
 * field in ublksrv_io_desc encodes buffer index and byte offset instead
 * of a userspace virtual address.
 */
#define     UBLK_IO_F_SHMEM_ZC      (1U << 19)
 
/*
 * io cmd is described by this structure, and stored in share memory, indexed
 * by request tag.
 *
 * The data is stored by ublk driver, and read by ublksrv after one fetch command
 * returns.
 */
struct ublksrv_io_desc {
    /* op: bit 0-7, flags: bit 8-31 */
    __u32       op_flags;
 
    union {
        __u32       nr_sectors;
        __u32       nr_zones; /* for UBLK_IO_OP_REPORT_ZONES */
    };
 
    /* start sector for this io */
    __u64       start_sector;
 
    /* buffer address in ublksrv daemon vm space, from ublk driver */
    __u64       addr;
};
 
static inline __u8 ublksrv_get_op(const struct ublksrv_io_desc *iod)
{
    return iod->op_flags & 0xff;
}
 
static inline __u32 ublksrv_get_flags(const struct ublksrv_io_desc *iod)
{
    return iod->op_flags >> 8;
}
 
/*
 * If this flag is set, fallback by completing the uring_cmd and setting
 * `UBLK_IO_F_NEED_REG_BUF` in case of auto-buf-register failure;
 * otherwise the client ublk request is failed silently
 *
 * If ublk server passes this flag, it has to check if UBLK_IO_F_NEED_REG_BUF
 * is set in `ublksrv_io_desc.op_flags`. If UBLK_IO_F_NEED_REG_BUF is set,
 * ublk server needs to register io buffer manually for handling IO command.
 */
#define UBLK_AUTO_BUF_REG_FALLBACK  (1 << 0)
#define UBLK_AUTO_BUF_REG_F_MASK    UBLK_AUTO_BUF_REG_FALLBACK
 
struct ublk_auto_buf_reg {
    /* index for registering the delivered request buffer */
    __u16  index;
    __u8   flags;
    __u8   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
 *  - bit16 ~ bit23: flags
 *  - 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 = (__u16)sqe_addr,
        .flags = (__u8)(sqe_addr >> 16),
        .reserved0 = (__u8)(sqe_addr >> 24),
        .reserved1 = (__u32)(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->flags << 16 | (__u64)buf->reserved0 << 24 |
        (__u64)buf->reserved1 << 32;
 
    return addr;
}
 
/* issued to ublk driver via /dev/ublkcN */
struct ublksrv_io_cmd {
    __u16   q_id;
 
    /* for fetch/commit which result */
    __u16   tag;
 
    /* io result, it is valid for COMMIT* command only */
    __s32   result;
 
    union {
        /*
         * userspace buffer address in ublksrv daemon process, valid for
         * FETCH* command only
         *
         * `addr` should not be used when UBLK_F_USER_COPY is enabled,
         * because userspace handles data copy by pread()/pwrite() over
         * /dev/ublkcN. But in case of UBLK_F_ZONED, this union is
         * re-used to pass back the allocated LBA for
         * UBLK_IO_OP_ZONE_APPEND which actually depends on
         * UBLK_F_USER_COPY
         */
        __u64   addr;
        __u64   zone_append_lba;
    };
};
 
struct ublk_elem_header {
    __u16 tag;  /* IO tag */
 
    /*
     * Buffer index for incoming io command, only valid iff
     * UBLK_F_AUTO_BUF_REG is set
     */
    __u16 buf_index;
    __s32 result;   /* I/O completion result (commit only) */
};
 
/*
 * uring_cmd buffer structure for batch commands
 *
 * buffer includes multiple elements, which number is specified by
 * `nr_elem`. Each element buffer is organized in the following order:
 *
 * struct ublk_elem_buffer {
 *  // Mandatory fields (8 bytes)
 *  struct ublk_elem_header header;
 *
 *  // Optional fields (8 bytes each, included based on flags)
 *
 *  // Buffer address (if UBLK_BATCH_F_HAS_BUF_ADDR) for copying data
 *  // between ublk request and ublk server buffer
 *  __u64 buf_addr;
 *
 *  // returned Zone append LBA (if UBLK_BATCH_F_HAS_ZONE_LBA)
 *  __u64 zone_lba;
 * }
 *
 * Used for `UBLK_U_IO_PREP_IO_CMDS` and `UBLK_U_IO_COMMIT_IO_CMDS`
 */
struct ublk_batch_io {
    __u16  q_id;
#define UBLK_BATCH_F_HAS_ZONE_LBA   (1 << 0)
#define UBLK_BATCH_F_HAS_BUF_ADDR   (1 << 1)
#define UBLK_BATCH_F_AUTO_BUF_REG_FALLBACK  (1 << 2)
    __u16   flags;
    __u16   nr_elem;
    __u8    elem_bytes;
    __u8    reserved;
    __u64   reserved2;
};
 
struct ublk_param_basic {
#define UBLK_ATTR_READ_ONLY            (1 << 0)
#define UBLK_ATTR_ROTATIONAL           (1 << 1)
#define UBLK_ATTR_VOLATILE_CACHE       (1 << 2)
#define UBLK_ATTR_FUA                  (1 << 3)
    __u32   attrs;
    __u8    logical_bs_shift;
    __u8    physical_bs_shift;
    __u8    io_opt_shift;
    __u8    io_min_shift;
 
    __u32   max_sectors;
    __u32   chunk_sectors;
 
    __u64   dev_sectors;
    __u64   virt_boundary_mask;
};
 
struct ublk_param_discard {
    __u32   discard_alignment;
 
    __u32   discard_granularity;
    __u32   max_discard_sectors;
 
    __u32   max_write_zeroes_sectors;
    __u16   max_discard_segments;
    __u16   reserved0;
};
 
/*
 * read-only, can't set via UBLK_CMD_SET_PARAMS, disk_devt is available
 * after device is started
 */
struct ublk_param_devt {
    __u32   char_major;
    __u32   char_minor;
    __u32   disk_major;
    __u32   disk_minor;
};
 
struct ublk_param_zoned {
    __u32   max_open_zones;
    __u32   max_active_zones;
    __u32   max_zone_append_sectors;
    __u8    reserved[20];
};
 
struct ublk_param_dma_align {
    __u32   alignment;
    __u8    pad[4];
};
 
#define UBLK_MIN_SEGMENT_SIZE   4096
/*
 * If any one of the three segment parameter is set as 0, the behavior is
 * undefined.
 */
struct ublk_param_segment {
    /*
     * seg_boundary_mask + 1 needs to be power_of_2(), and the sum has
     * to be >= UBLK_MIN_SEGMENT_SIZE(4096)
     */
    __u64   seg_boundary_mask;
 
    /*
     * max_segment_size could be override by virt_boundary_mask, so be
     * careful when setting both.
     *
     * max_segment_size has to be >= UBLK_MIN_SEGMENT_SIZE(4096)
     */
    __u32   max_segment_size;
    __u16   max_segments;
    __u8    pad[2];
};
 
struct ublk_param_integrity {
    __u32   flags; /* LBMD_PI_CAP_* from linux/fs.h */
    __u16   max_integrity_segments; /* 0 means no limit */
    __u8    interval_exp;
    __u8    metadata_size; /* UBLK_PARAM_TYPE_INTEGRITY requires nonzero */
    __u8    pi_offset;
    __u8    csum_type; /* LBMD_PI_CSUM_* from linux/fs.h */
    __u8    tag_size;
    __u8    pad[5];
};
 
struct ublk_params {
    /*
     * Total length of parameters, userspace has to set 'len' for both
     * SET_PARAMS and GET_PARAMS command, and driver may update len
     * if two sides use different version of 'ublk_params', same with
     * 'types' fields.
     */
    __u32   len;
#define UBLK_PARAM_TYPE_BASIC           (1 << 0)
#define UBLK_PARAM_TYPE_DISCARD         (1 << 1)
#define UBLK_PARAM_TYPE_DEVT            (1 << 2)
#define UBLK_PARAM_TYPE_ZONED           (1 << 3)
#define UBLK_PARAM_TYPE_DMA_ALIGN       (1 << 4)
#define UBLK_PARAM_TYPE_SEGMENT         (1 << 5)
#define UBLK_PARAM_TYPE_INTEGRITY       (1 << 6) /* requires UBLK_F_INTEGRITY */
    __u32   types;          /* types of parameter included */
 
    struct ublk_param_basic     basic;
    struct ublk_param_discard   discard;
    struct ublk_param_devt      devt;
    struct ublk_param_zoned zoned;
    struct ublk_param_dma_align dma;
    struct ublk_param_segment   seg;
    struct ublk_param_integrity integrity;
};
 
/*
 * Shared memory zero-copy addr encoding for UBLK_IO_F_SHMEM_ZC.
 *
 * When UBLK_IO_F_SHMEM_ZC is set, ublksrv_io_desc.addr is encoded as:
 *   bits [0:31]  = byte offset within the buffer (up to 4GB)
 *   bits [32:47] = buffer index (up to 65536)
 *   bits [48:63] = reserved (must be zero)
 */
#define UBLK_SHMEM_ZC_OFF_MASK      0xffffffffULL
#define UBLK_SHMEM_ZC_IDX_OFF       32
#define UBLK_SHMEM_ZC_IDX_MASK      0xffffULL
 
static inline __u64 ublk_shmem_zc_addr(__u16 index, __u32 offset)
{
    return ((__u64)index << UBLK_SHMEM_ZC_IDX_OFF) | offset;
}
 
static inline __u16 ublk_shmem_zc_index(__u64 addr)
{
    return (addr >> UBLK_SHMEM_ZC_IDX_OFF) & UBLK_SHMEM_ZC_IDX_MASK;
}
 
static inline __u32 ublk_shmem_zc_offset(__u64 addr)
{
    return (__u32)(addr & UBLK_SHMEM_ZC_OFF_MASK);
}
 
#endif