btrfs-progs/common/path-utils.c

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/*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public
* License v2 as published by the Free Software Foundation.
*
* 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., 59 Temple Place - Suite 330,
* Boston, MA 021110-1307, USA.
*/
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <linux/major.h>
#include <linux/kdev_t.h>
#include <linux/loop.h>
#include <linux/limits.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <mntent.h>
#include <string.h>
#include <errno.h>
#include <ctype.h>
/*
* For dirname() and basename(), but never use basename directly, there's
* path_basename() with unified GNU behaviour regardless of the includes and
* conditional defines. See basename(3) for more.
*/
#include <libgen.h>
#include <limits.h>
#include "common/string-utils.h"
#include "common/path-utils.h"
/*
* Check if @path is a block device node
* Returns:
* 1 - path is a block device
* 0 - not a block device
* <0 - negative errno
*/
int path_is_block_device(const char *path)
{
struct stat statbuf;
if (stat(path, &statbuf) < 0)
return -errno;
return !!S_ISBLK(statbuf.st_mode);
}
/*
* Check if given path is a mount point. (Note: a similar function also exists
* in libudev so it's been renamed to avoid clash.)
*
* Return: 1 if yes,
* 0 if no,
* -1 for error
*/
int path_is_a_mount_point(const char *path)
{
FILE *f;
struct mntent *mnt;
int ret = 0;
f = setmntent("/proc/self/mounts", "r");
if (f == NULL)
return -1;
while ((mnt = getmntent(f)) != NULL) {
if (strcmp(mnt->mnt_dir, path))
continue;
ret = 1;
break;
}
endmntent(f);
return ret;
}
int path_is_reg_file(const char *path)
{
struct stat statbuf;
if (stat(path, &statbuf) < 0)
return -errno;
return S_ISREG(statbuf.st_mode);
}
int path_exists(const char *path)
{
struct stat statbuf;
int ret;
ret = stat(path, &statbuf);
if (ret < 0) {
if (errno == ENOENT)
return 0;
else
return -errno;
}
return 1;
}
/* checks if a device is a loop device */
static int is_loop_device(const char *device)
{
struct stat statbuf;
if(stat(device, &statbuf) < 0)
return -errno;
return (S_ISBLK(statbuf.st_mode) &&
MAJOR(statbuf.st_rdev) == LOOP_MAJOR);
}
/*
* Takes a loop device path (e.g. /dev/loop0) and returns
* the associated file (e.g. /images/my_btrfs.img) using
* loopdev API
*/
static int resolve_loop_device_with_loopdev(const char* loop_dev, char* loop_file)
{
int fd;
int ret;
struct loop_info64 lo64;
fd = open(loop_dev, O_RDONLY | O_NONBLOCK);
if (fd < 0)
return -errno;
ret = ioctl(fd, LOOP_GET_STATUS64, &lo64);
if (ret < 0) {
ret = -errno;
goto out;
}
memcpy(loop_file, lo64.lo_file_name, sizeof(lo64.lo_file_name));
loop_file[sizeof(lo64.lo_file_name)] = 0;
out:
close(fd);
return ret;
}
/*
* Takes a loop device path (e.g. /dev/loop0) and returns
* the associated file (e.g. /images/my_btrfs.img)
*/
static int resolve_loop_device(const char* loop_dev, char* loop_file,
int max_len)
{
int ret;
FILE *f;
char fmt[20];
char p[PATH_MAX];
char real_loop_dev[PATH_MAX];
if (!realpath(loop_dev, real_loop_dev))
return -errno;
snprintf(p, PATH_MAX, "/sys/block/%s/loop/backing_file", strrchr(real_loop_dev, '/'));
if (!(f = fopen(p, "r"))) {
if (errno == ENOENT)
/*
* It's possibly a partitioned loop device, which is
* resolvable with loopdev API.
*/
return resolve_loop_device_with_loopdev(loop_dev, loop_file);
return -errno;
}
snprintf(fmt, 20, "%%%i[^\n]", max_len - 1);
ret = fscanf(f, fmt, loop_file);
fclose(f);
if (ret == EOF)
return -errno;
return 0;
}
/*
* Checks whether a and b are identical or device
* files associated with the same block device
*/
static int is_same_blk_file(const char* a, const char* b)
{
struct stat st_buf_a, st_buf_b;
char real_a[PATH_MAX];
char real_b[PATH_MAX];
if (!realpath(a, real_a))
strncpy_null(real_a, a, sizeof(real_a));
if (!realpath(b, real_b))
strncpy_null(real_b, b, sizeof(real_b));
/* Identical path? */
if (strcmp(real_a, real_b) == 0)
return 1;
if (stat(a, &st_buf_a) < 0 || stat(b, &st_buf_b) < 0) {
if (errno == ENOENT)
return 0;
return -errno;
}
/* Same blockdevice? */
if (S_ISBLK(st_buf_a.st_mode) && S_ISBLK(st_buf_b.st_mode) &&
st_buf_a.st_rdev == st_buf_b.st_rdev) {
return 1;
}
/* Hardlink? */
if (st_buf_a.st_dev == st_buf_b.st_dev &&
st_buf_a.st_ino == st_buf_b.st_ino) {
return 1;
}
return 0;
}
/*
* Checks if a and b are identical or device files associated with the same
* block device or if one file is a loop device that uses the other file.
*/
int is_same_loop_file(const char *a, const char *b)
{
char res_a[PATH_MAX];
char res_b[PATH_MAX];
const char* final_a = NULL;
const char* final_b = NULL;
int ret;
/* Resolve a if it is a loop device */
if ((ret = is_loop_device(a)) < 0) {
if (ret == -ENOENT)
return 0;
return ret;
} else if (ret) {
ret = resolve_loop_device(a, res_a, sizeof(res_a));
if (ret < 0) {
if (errno != EPERM)
return ret;
} else {
final_a = res_a;
}
} else {
final_a = a;
}
/* Resolve b if it is a loop device */
if ((ret = is_loop_device(b)) < 0) {
if (ret == -ENOENT)
return 0;
return ret;
} else if (ret) {
ret = resolve_loop_device(b, res_b, sizeof(res_b));
if (ret < 0) {
if (errno != EPERM)
return ret;
} else {
final_b = res_b;
}
} else {
final_b = b;
}
return is_same_blk_file(final_a, final_b);
}
/* Checks if a file exists and is a block or regular file*/
int path_is_reg_or_block_device(const char *filename)
{
struct stat st_buf;
if (stat(filename, &st_buf) < 0) {
if(errno == ENOENT)
return 0;
else
return -errno;
}
return (S_ISBLK(st_buf.st_mode) || S_ISREG(st_buf.st_mode));
}
/*
* Resolve a pathname to a device mapper node to /dev/mapper/<name>
* Returns NULL on invalid input or malloc failure; Other failures
* will be handled by the caller using the input pathname.
*/
char *path_canonicalize_dm_name(const char *ptname)
{
FILE *f;
size_t sz;
char path[PATH_MAX], name[PATH_MAX], *res = NULL;
if (!ptname || !*ptname)
return NULL;
snprintf(path, sizeof(path), "/sys/block/%s/dm/name", ptname);
if (!(f = fopen(path, "r")))
return NULL;
/* read <name>\n from sysfs */
if (fgets(name, sizeof(name), f) && (sz = strlen(name)) > 1) {
name[sz - 1] = '\0';
snprintf(path, sizeof(path), "/dev/mapper/%s", name);
if (access(path, F_OK) == 0)
res = strdup(path);
}
fclose(f);
return res;
}
/*
* Resolve a pathname to a canonical device node, e.g. /dev/sda1 or
* to a device mapper pathname.
* Returns NULL on invalid input or malloc failure; Other failures
* will be handled by the caller using the input pathname.
*/
char *path_canonicalize(const char *path)
{
char *canonical, *p;
if (!path || !*path)
return NULL;
canonical = realpath(path, NULL);
if (!canonical)
return strdup(path);
p = strrchr(canonical, '/');
if (p && strncmp(p, "/dm-", 4) == 0 && isdigit(*(p + 4))) {
char *dm = path_canonicalize_dm_name(p + 1);
if (dm) {
free(canonical);
return dm;
}
}
return canonical;
}
/*
* Test if path is a directory
* Returns:
* 0 - path exists but it is not a directory
* 1 - path exists and it is a directory
* < 0 - error
*/
int path_is_dir(const char *path)
{
struct stat st;
int ret;
ret = stat(path, &st);
if (ret < 0)
return -errno;
return !!S_ISDIR(st.st_mode);
}
/*
* Test if a path is recursively contained in parent. Assumes parent and path
* are null terminated absolute paths.
*
* Returns:
* 0 - path not contained in parent
* 1 - path contained in parent
* < 0 - error
*
* e.g. (/, /foo) -> 1
* (/foo, /) -> 0
* (/foo, /foo/bar/baz) -> 1
*/
int path_is_in_dir(const char *parent, const char *path)
{
char tmp[PATH_MAX];
char *curr_dir = tmp;
int ret;
strncpy_null(tmp, path, sizeof(tmp));
while (strcmp(parent, curr_dir) != 0) {
if (strcmp(curr_dir, "/") == 0) {
ret = 0;
goto out;
}
curr_dir = dirname(curr_dir);
}
ret = 1;
out:
return ret;
}
/*
* Copy a path argument from SRC to DEST and check the SRC length if it's at
* most PATH_MAX and fits into DEST. DESTLEN is supposed to be exact size of
* the buffer.
* The destination buffer is zero terminated.
* Return < 0 for error, 0 otherwise.
*/
int arg_copy_path(char *dest, const char *src, int destlen)
{
size_t len = strlen(src);
if (len >= PATH_MAX || len >= destlen)
return -ENAMETOOLONG;
strncpy_null(dest, src, destlen);
return 0;
}
int path_cat_out(char *out, const char *p1, const char *p2)
{
int p1_len = strlen(p1);
int p2_len = strlen(p2);
if (p1_len + p2_len + 2 >= PATH_MAX)
return -ENAMETOOLONG;
if (p1_len && p1[p1_len - 1] == '/')
p1_len--;
if (p2_len && p2[p2_len - 1] == '/')
p2_len--;
sprintf(out, "%.*s/%.*s", p1_len, p1, p2_len, p2);
return 0;
}
int path_cat3_out(char *out, const char *p1, const char *p2, const char *p3)
{
int p1_len = strlen(p1);
int p2_len = strlen(p2);
int p3_len = strlen(p3);
if (p1_len + p2_len + p3_len + 3 >= PATH_MAX)
return -ENAMETOOLONG;
if (p1_len && p1[p1_len - 1] == '/')
p1_len--;
if (p2_len && p2[p2_len - 1] == '/')
p2_len--;
if (p3_len && p3[p3_len - 1] == '/')
p3_len--;
sprintf(out, "%.*s/%.*s/%.*s", p1_len, p1, p2_len, p2, p3_len, p3);
return 0;
}
/* Subvolume helper functions */
/*
* test if name is a correct subvolume name
* this function return
* 0-> name is not a correct subvolume name
* 1-> name is a correct subvolume name
*/
int test_issubvolname(const char *name)
{
return name[0] != '\0' && !strchr(name, '/') &&
strcmp(name, ".") && strcmp(name, "..");
}
/*
* Unified GNU semantics basename helper, never changing the argument. Always
* use this instead of basename().
*/
char *path_basename(char *path)
{
#if 0
const char *tmp = strrchr(path, '/');
/* Special case when the whole path is just "/". */
if (path[0] == '/' && path[1] == 0)
return path;
return tmp ? tmp + 1 : path;
#else
return basename(path);
#endif
}
/*
* Return dirname component of path, may change the argument.
* Own helper for parity with path_basename().
*/
char *path_dirname(char *path)
{
return dirname(path);
}