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| #define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>
#include <sys/stat.h>
#include <linux/aio_abi.h>
#include <sys/syscall.h>
// 封装 io_setup 系统调用
static inline int my_io_setup(unsigned nr_events, io_context_t *ctxp) {
return syscall(__NR_io_setup, nr_events, ctxp);
}
// 封装 io_destroy 系统调用
static inline int my_io_destroy(io_context_t ctx) {
return syscall(__NR_io_destroy, ctx);
}
// 封装 io_submit 系统调用
static inline int my_io_submit(io_context_t ctx, long nr, struct iocb **iocbpp) {
return syscall(__NR_io_submit, ctx, nr, iocbpp);
}
// 辅助函数：初始化一个异步写入的 iocb 结构
void prep_pwrite(struct iocb *iocb, int fd, const void *buf, size_t count, __u64 offset) {
memset(iocb, 0, sizeof(*iocb)); // 清零结构体
iocb->aio_lio_opcode = IOCB_CMD_PWRITE; // 设置操作类型为异步写
iocb->aio_fildes = fd; // 设置文件描述符
iocb->aio_buf = (__u64)(unsigned long)buf; // 设置缓冲区地址
iocb->aio_nbytes = count; // 设置写入字节数
iocb->aio_offset = offset; // 设置文件偏移量
iocb->aio_data = (__u64)(unsigned long)buf; // 设置用户数据 (这里用 buf 地址)
}
int main() {
const char *filename = "io_submit_test_file.txt";
const int num_writes = 3;
const size_t chunk_size = 1024;
int fd;
io_context_t ctx = 0; // 必须初始化为 0
struct iocb iocbs[num_writes];
struct iocb *iocb_ptrs[num_writes];
char buffers[num_writes][chunk_size];
int ret, i;
printf("--- Demonstrating io_submit ---\n");
// 1. 初始化要写入的数据
for (i = 0; i < num_writes; ++i) {
memset(buffers[i], 'A' + i, chunk_size); // Fill with 'A', 'B', 'C'
}
// 2. 创建并打开文件
fd = open(filename, O_CREAT | O_TRUNC | O_WRONLY, 0644);
if (fd == -1) {
perror("open");
exit(EXIT_FAILURE);
}
printf("1. Opened/created file '%s' (fd=%d)\n", filename, fd);
// 3. 初始化异步 I/O 上下文
ret = my_io_setup(num_writes, &ctx);
if (ret < 0) {
perror("io_setup");
close(fd);
exit(EXIT_FAILURE);
}
printf("2. Initialized AIO context (ctx_id=%llu)\n", (unsigned long long)ctx);
// 4. 准备 I/O 请求 (iocb)
printf("3. Preparing %d asynchronous write requests...\n", num_writes);
for (i = 0; i < num_writes; ++i) {
prep_pwrite(&iocbs[i], fd, buffers[i], chunk_size, i * chunk_size);
iocb_ptrs[i] = &iocbs[i];
printf(" Prepared write %d: offset=%zu, size=%zu, data='%c'...\n",
i+1, i * chunk_size, chunk_size, 'A' + i);
}
// 5. 提交 I/O 请求
printf("4. Submitting %d write requests using io_submit...\n", num_writes);
ret = my_io_submit(ctx, num_writes, iocb_ptrs);
if (ret != num_writes) {
fprintf(stderr, " io_submit failed: submitted %d requests, expected %d\n", ret, num_writes);
if (ret < 0) {
perror(" io_submit error");
} else {
printf(" Only the first %d requests were submitted successfully.\n", ret);
}
// 清理并退出
my_io_destroy(ctx);
close(fd);
unlink(filename);
exit(EXIT_FAILURE);
}
printf(" io_submit succeeded. All %d requests submitted.\n", ret);
// 6. 注意：此时写入操作可能仍在进行中，我们需要用 io_getevents 来等待完成
// 这个例子只演示提交，不等待完成。
printf("5. Note: io_submit returned immediately. The writes are happening in the background.\n");
printf(" To get the results, you need to call io_getevents().\n");
// 7. 清理资源 (在真实程序中，你应该在 io_getevents 确认完成后再关闭文件)
printf("6. Cleaning up resources...\n");
my_io_destroy(ctx);
printf(" Destroyed AIO context.\n");
close(fd);
printf(" Closed file descriptor.\n");
unlink(filename); // 删除测试文件
printf(" Deleted test file '%s'.\n", filename);
printf("\n--- Summary ---\n");
printf("1. io_submit(ctx_id, nr, iocb_ptrs) submits 'nr' AIO requests to the context 'ctx_id'.\n");
printf("2. Each request is described by an 'iocb' struct, pointed to by elements in 'iocb_ptrs'.\n");
printf("3. It returns the number of requests successfully submitted (may be < nr on partial failure).\n");
printf("4. It returns immediately; the I/O happens asynchronously in the background.\n");
printf("5. Use io_getevents() afterwards to check for completion and get results.\n");
return 0;
}
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