NULL);
}
-int path_is_mount_point(const char *t, bool allow_symlink) {
-
- union file_handle_union h = FILE_HANDLE_INIT;
+int fd_is_mount_point(int fd) {
+ union file_handle_union h = FILE_HANDLE_INIT, h_parent = FILE_HANDLE_INIT;
int mount_id = -1, mount_id_parent = -1;
+ bool nosupp = false;
struct stat a, b;
int r;
- _cleanup_close_ int fd = -1;
- bool nosupp = false;
+
+ assert(fd >= 0);
/* We are not actually interested in the file handles, but
* name_to_handle_at() also passes us the mount ID, hence use
* it but throw the handle away */
- if (path_equal(t, "/"))
- return 1;
-
- fd = openat(AT_FDCWD, t, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|(allow_symlink ? 0 : O_PATH));
- if (fd < 0) {
- if (errno == ENOENT)
- return 0;
-
- return -errno;
- }
-
r = name_to_handle_at(fd, "", &h.handle, &mount_id, AT_EMPTY_PATH);
if (r < 0) {
if (errno == ENOSYS)
goto fallback;
else if (errno == EOPNOTSUPP)
/* This kernel or file system does not support
- * name_to_handle_at(), hence fallback to the
+ * name_to_handle_at(), hence let's see if the
+ * upper fs supports it (in which case it is a
+ * mount point), otherwise fallback to the
* traditional stat() logic */
nosupp = true;
- else if (errno == ENOENT)
- return 0;
else
return -errno;
}
-
- h.handle.handle_bytes = MAX_HANDLE_SZ;
- r = name_to_handle_at(fd, "..", &h.handle, &mount_id_parent, 0);
- if (r < 0)
- if (errno == EOPNOTSUPP)
+ r = name_to_handle_at(fd, "..", &h_parent.handle, &mount_id_parent, 0);
+ if (r < 0) {
+ if (errno == EOPNOTSUPP) {
if (nosupp)
/* Neither parent nor child do name_to_handle_at()?
We have no choice but to fall back. */
goto fallback;
else
- /* The parent can't do name_to_handle_at() but
- * the directory we are interested in can?
- * Or the other way around?
+ /* The parent can't do name_to_handle_at() but the
+ * directory we are interested in can?
* If so, it must be a mount point. */
return 1;
- else
+ } else
return -errno;
- else
+ } else if (nosupp)
+ /* The parent can do name_to_handle_at() but the
+ * directory we are interested in can't? If so, it
+ * must be a mount point. */
+ return 1;
+ else {
+ /* If the file handle for the directory we are
+ * interested in and its parent are identical, we
+ * assume this is the root directory, which is a mount
+ * point. */
+
+ if (h.handle.handle_bytes == h_parent.handle.handle_bytes &&
+ h.handle.handle_type == h_parent.handle.handle_type &&
+ memcmp(h.handle.f_handle, h_parent.handle.f_handle, h.handle.handle_bytes) == 0)
+ return 1;
+
return mount_id != mount_id_parent;
+ }
fallback:
r = fstatat(fd, "", &a, AT_EMPTY_PATH);
-
- if (r < 0) {
- if (errno == ENOENT)
- return 0;
-
+ if (r < 0)
return -errno;
- }
-
r = fstatat(fd, "..", &b, 0);
if (r < 0)
return -errno;
+ /* A directory with same device and inode as its parent? Must
+ * be the root directory */
+ if (a.st_dev == b.st_dev &&
+ a.st_ino == b.st_ino)
+ return 1;
+
return a.st_dev != b.st_dev;
}
+int path_is_mount_point(const char *t, bool allow_symlink) {
+ _cleanup_close_ int fd = -1;
+
+ assert(t);
+
+ if (path_equal(t, "/"))
+ return 1;
+
+ fd = openat(AT_FDCWD, t, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|(allow_symlink ? 0 : O_PATH));
+ if (fd < 0)
+ return -errno;
+
+ return fd_is_mount_point(fd);
+}
+
int path_is_read_only_fs(const char *path) {
struct statvfs st;