compare.c

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <assert.h>

#include <sys/stat.h>
#include <sys/time.h>
#include <sys/ioctl.h>

#include <linux/fs.h>
#include <linux/fiemap.h>

#define FILE_INTERVAL (1<<13) /* 8Kb */
#define CHUNK_SIZE (1<<12)
long long interval(struct timeval t1, struct timeval t2)
{
    long long val = 0;
    val += (t2.tv_usec - t1.tv_usec);
    val += (t2.tv_sec - t1.tv_sec) * 1000 * 1000;
    return val;
}

int dumping(int fd, int file_size){
	off_t data, hole = 0;
	off_t len, off = 0;
	int i=0;
	while (hole < file_size) {
		data = lseek(fd, hole, SEEK_DATA);
		if (data < 0) {
			if (hole == 0) {
				/* No SEEK_HOLE/DATA by FS */
				data = 0;
				hole = file_size;
			} else if(errno == ENXIO){
                /* The end of file */
				return 0;
			} else{
                return -1;
            }
		} else {
			hole = lseek(fd, data, SEEK_HOLE);
			if (hole < 0) {
                if(errno == ENXIO){
                    /* The end of file */
                    return 0;
                }
				fprintf(stderr, "Can't seek file hole");
				return -1;
			}
		}
		len = hole - data;
		off = data;
		i++;
	}
	return 0;
}

int main(int argc, char **argv) {
    struct fiemap fiemap = {};
    struct timeval t1, t2;
    char data[CHUNK_SIZE];
    memset(data, 'a', CHUNK_SIZE);
    struct stat st;
    int fd, off, file_size = FILE_INTERVAL;

    if (argc != 3 && argc != 2) {
            printf("usage: %s <path> [size]\n", argv[0]);
            return 1;
    }

    if (argc == 3)
            file_size = atoi(argv[2]);
    if (file_size < FILE_INTERVAL)
            file_size = FILE_INTERVAL;
    file_size -= file_size % FILE_INTERVAL;

    fd = open(argv[1], O_RDWR | O_CREAT | O_TRUNC, 0644);
    if (fd < 0) {
            perror("open");
            return 1;
    }

    for (off = 0; off < file_size; off += FILE_INTERVAL) {
            if (pwrite(fd, &data, CHUNK_SIZE, off) != CHUNK_SIZE) {
                    perror("pwrite");
                    close(fd);
                    return 1;
            }
    }

    if (ftruncate(fd, file_size)) {
            perror("ftruncate");
            close(fd);
            return 1;
    }

    if (fstat(fd, &st) < 0) {
            perror("fstat");
            close(fd);
            return 1;
    }
    assert(file_size == st.st_size);
    printf("size: %ld\n", st.st_size);
    printf("actual size: %ld\n", st.st_blocks * 512);

    fiemap.fm_length = FIEMAP_MAX_OFFSET;
    gettimeofday(&t1, NULL);
    if (ioctl(fd, FS_IOC_FIEMAP, &fiemap) < 0) {
        perror("fiemap");
        close(fd);
        return 1;
    }
    gettimeofday(&t2, NULL);
    printf("fiemap time = %lld us\n", interval(t1, t2));

    gettimeofday(&t1, NULL);
    if (dumping(fd, file_size) < 0) {  
        printf("error");     
        close(fd);
        return 1;
    }
    gettimeofday(&t2, NULL);

    printf("SEEK time = %lld us\n", interval(t1, t2));
    close(fd);
    return 0;
}