SQE: Submission Queue Entry

The submission queue entry (SQE) is what you use to tell io_uring what you want to do, like read a file, write a file, accept a connection on a socket, etc.


This structure is part of the raw io_uring interface and is defined in io_uring.h.

struct io_uring_sqe

struct io_uring_sqe {
    __u8    opcode;         /* type of operation for this sqe */
    __u8    flags;          /* IOSQE_ flags */
    __u16   ioprio;         /* ioprio for the request */
    __s32   fd;             /* file descriptor to do IO on */
    union {
        __u64       off;    /* offset into file */
        __u64       addr2;
    union {
        __u64       addr;   /* pointer to buffer or iovecs */
        __u64       splice_off_in;
    __u32   len;            /* buffer size or number of iovecs */
    union {
        __kernel_rwf_t      rw_flags;
        __u32               fsync_flags;
        __u16               poll_events;
        __u32               sync_range_flags;
        __u32               msg_flags;
        __u32               timeout_flags;
        __u32               accept_flags;
        __u32               cancel_flags;
        __u32               open_flags;
        __u32               statx_flags;
        __u32               fadvise_advice;
        __u32               splice_flags;
    /* data to be passed back at completion time */
    __u64   user_data;
    union {
        struct {
            /* pack this to avoid bogus arm OABI complaints */
            union {
                /* index into fixed buffers, if used */
                __u16       buf_index;
                /* for grouped buffer selection */
                __u16       buf_group;
            } __attribute__((packed));
            /* personality to use, if used */
            __u16   personality;
            __s32   splice_fd_in;
        __u64       __pad2[3];