ficlone.c

/*
This file is part of rmw<https://theimpossibleastronaut.github.io/rmw-website/>

Copyright (C) 2012-2024  Andy Alt (arch_stanton5995@proton.me)
Other authors: https://github.com/theimpossibleastronaut/rmw/blob/master/AUTHORS.md

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 3 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, see <http://www.gnu.org/licenses/>.
*/

#ifndef INC_GLOBALS_H
#define INC_GLOBALS_H
#include "globals.h"
#endif

#ifdef HAVE_FICLONE
#include <fcntl.h>
#include <linux/fs.h>
#include <sys/ioctl.h>
#include <sys/statfs.h>
#include <sys/stat.h>
#include <unistd.h>
#endif

#include "ficlone.h"
#include "messages.h"

bool
is_ficlone_fs(const char *path)
{
#ifdef HAVE_FICLONE
  struct statfs buf;

  if (statfs(path, &buf) == -1)
  {
    print_msg_error();
    perror("statfs");
    exit(EXIT_FAILURE);
  }

  return buf.f_type == BTRFS_SUPER_MAGIC;
#else
  (void) path;
  return false;
#endif
}


int
do_ficlone(const char *source, const char *dest, int *save_errno)
{
#ifdef HAVE_FICLONE
  int src_fd, dest_fd;
  struct stat src_stat;

  // Open the source file in read-only mode
  src_fd = open(source, O_RDONLY);
  if (src_fd == -1)
  {
    perror("open source");
    return src_fd;
  }

  // Retrieve source file permissions
  if (fstat(src_fd, &src_stat) == -1)
  {
    perror("fstat source");
    close(src_fd);
    return -1;
  }

  // Ensure no umask setting interferes with the permissions
  mode_t old_umask = umask(0);
  // Open or create the destination file with the same permissions as the source
  dest_fd = open(dest, O_WRONLY | O_CREAT, src_stat.st_mode & 0777);
  umask(old_umask);
  if (dest_fd == -1)
  {
    perror("open destination");
    close(src_fd);
    return dest_fd;
  }

  int res = ioctl(dest_fd, FICLONE, src_fd);
  *save_errno = errno;

  close(src_fd);
  close(dest_fd);

  if (res == -1)
  {
    if (*save_errno != EXDEV)
      fprintf(stderr, "ioctl: %s in %s\n", strerror(*save_errno), __func__);
    // Clone failed, remove the destination file
    if (unlink(dest) != 0)
      fprintf(stderr, "unlink: %s in %s\n", strerror(errno), __func__);
    return res;
  }

  res = unlink(source);
  if (res == -1)
  {
    perror("unlink source");
    return res;
  }

  return 0;
#else
  (void) source;
  (void) dest;
  (void) save_errno;
  return 0;
#endif
}