#include <liburing.h> 

 "void io_uring_sqe_set_data(struct io_uring_sqe *" sqe ","  " void *" user_data ");"  "  "void io_uring_sqe_set_data64(struct io_uring_sqe *" sqe ","  " __u64 " data ");" 

The io_uring_sqe_set_data (3) function stores a user_data pointer with the submission queue entry sqe . The io_uring_sqe_set_data64 (3) function stores a 64-bit data value with the submission queue entry sqe . After the caller has requested a submission queue entry (SQE) with io_uring_get_sqe (3) , they can associate a data pointer or value with the SQE. Once the completion arrives, the function io_uring_cqe_get_data (3) or io_uring_cqe_get_data64 (3) can be called to retrieve the data pointer or value associated with the submitted request. Note that if neither of these functions are called, or the user_data field in the sqe isn't set manually either, then the field may contain a value from a previous use of this sqe. If an application relies on always having a valid user_data value present, it must always assign one to each sqe.