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/* find-mount-point.c -- find the root mount point for a file.
Copyright (C) 2010-2017 Free Software Foundation, Inc.
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/>. */
#include <config.h>
#include <sys/types.h>
#include "system.h"
#include "die.h"
#include "error.h"
#include "save-cwd.h"
#include "xgetcwd.h"
#include "find-mount-point.h"
/* Return the root mountpoint of the file system on which FILE exists, in
malloced storage. FILE_STAT should be the result of stating FILE.
Give a diagnostic and return NULL if unable to determine the mount point.
Exit if unable to restore current working directory. */
extern char *
find_mount_point (char const *file, struct stat const *file_stat)
{
struct saved_cwd cwd;
struct stat last_stat;
char *mp = NULL; /* The malloc'd mount point. */
if (save_cwd (&cwd) != 0)
{
error (0, errno, _("cannot get current directory"));
return NULL;
}
if (S_ISDIR (file_stat->st_mode))
/* FILE is a directory, so just chdir there directly. */
{
last_stat = *file_stat;
if (chdir (file) < 0)
{
error (0, errno, _("cannot change to directory %s"), quoteaf (file));
return NULL;
}
}
else
/* FILE is some other kind of file; use its directory. */
{
char *xdir = dir_name (file);
char *dir;
ASSIGN_STRDUPA (dir, xdir);
free (xdir);
if (chdir (dir) < 0)
{
error (0, errno, _("cannot change to directory %s"), quoteaf (dir));
return NULL;
}
if (stat (".", &last_stat) < 0)
{
error (0, errno, _("cannot stat current directory (now %s)"),
quoteaf (dir));
goto done;
}
}
/* Now walk up FILE's parents until we find another file system or /,
chdiring as we go. LAST_STAT holds stat information for the last place
we visited. */
while (true)
{
struct stat st;
if (stat ("..", &st) < 0)
{
error (0, errno, _("cannot stat %s"), quoteaf (".."));
goto done;
}
if (st.st_dev != last_stat.st_dev || st.st_ino == last_stat.st_ino)
/* cwd is the mount point. */
break;
if (chdir ("..") < 0)
{
error (0, errno, _("cannot change to directory %s"), quoteaf (".."));
goto done;
}
last_stat = st;
}
/* Finally reached a mount point, see what it's called. */
mp = xgetcwd ();
done:
/* Restore the original cwd. */
{
int save_errno = errno;
if (restore_cwd (&cwd) != 0)
die (EXIT_FAILURE, errno,
_("failed to return to initial working directory"));
free_cwd (&cwd);
errno = save_errno;
}
return mp;
}
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