Original rom http://smackerelofopinion.blogspot.de/2010/01/using-fiemap-ioctl-to-get-file-extents.html Extended by David Weber

fiemap.c

/*
 * Copyright (C) 2010 Canonical
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * 
 */

/*
 *  Author Colin Ian King,  colin.king@canonical.com
 */



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

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

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

void syntax(char **argv)
{
        fprintf(stderr, "%s [filename] [start] [length]...\n",argv[0]);
}

struct fiemap *read_fiemap(int fd, __u64 start, __u64 length)
{
        struct fiemap *fiemap;
        int extents_size;

        if ((fiemap = (struct fiemap*)malloc(sizeof(struct fiemap))) == NULL) {
                fprintf(stderr, "Out of memory allocating fiemap\n");
                return NULL;
        }
        memset(fiemap, 0, sizeof(struct fiemap));

        fiemap->fm_start = start;
        fiemap->fm_length = length;             /* Lazy */
        fiemap->fm_flags = 0;
        fiemap->fm_extent_count = 0;
        fiemap->fm_mapped_extents = 0;

        printf("start: %x, length: %x\n", start, length);

        /* Find out how many extents there are */
        if (ioctl(fd, FS_IOC_FIEMAP, fiemap) < 0) {
                fprintf(stderr, "fiemap ioctl() failed\n");
                return NULL;
        }

        /* Read in the extents */
        extents_size = sizeof(struct fiemap_extent) * 
                              (fiemap->fm_mapped_extents);

        /* Resize fiemap to allow us to read in the extents */
        if ((fiemap = (struct fiemap*)realloc(fiemap,sizeof(struct fiemap) + 
                                         extents_size)) == NULL) {
                fprintf(stderr, "Out of memory allocating fiemap\n");
                return NULL;
        }

        memset(fiemap->fm_extents, 0, extents_size);
        fiemap->fm_extent_count = fiemap->fm_mapped_extents;
        fiemap->fm_mapped_extents = 0;

        if (ioctl(fd, FS_IOC_FIEMAP, fiemap) < 0) {
                fprintf(stderr, "fiemap ioctl() failed\n");
                return NULL;
        }

        return fiemap;
}

void dump_fiemap(struct fiemap *fiemap, char *filename)
{
        int i;

        printf("File %s has %d extents:\n",filename, fiemap->fm_mapped_extents);

        printf("#\tLogical          Physical         Length           Flags\n");
        for (i=0;i<fiemap->fm_mapped_extents;i++) {
                printf("%d:\t%-16.16llx %-16.16llx %-16.16llx %-4.4x\n",
                        i,
                        fiemap->fm_extents[i].fe_logical,
                        fiemap->fm_extents[i].fe_physical,
                        fiemap->fm_extents[i].fe_length,
                        fiemap->fm_extents[i].fe_flags);
        }
        printf("\n");
}

int main(int argc, char **argv)
{
        int i;

        if (argc < 4) {
                syntax(argv);
                exit(EXIT_FAILURE);
        }

                int fd;

                if ((fd = open(argv[1], O_RDONLY)) < 0) {
                        fprintf(stderr, "Cannot open file %s\n", argv[i]);
                }
                else {
                        struct fiemap *fiemap;

                        if ((fiemap = read_fiemap(fd, (__u64)atoi(argv[2]), (__u64)atoi(argv[3]))) != NULL) 
                                dump_fiemap(fiemap, argv[1]);
                        close(fd);
                }
        exit(EXIT_SUCCESS);
}