machined: support non-btrfs file systems with "machinectl clone"

Fall back to a normal copy operation when the backing file system isn't btrfs,
and hence doesn't support cheap snapshotting. Of course, this will be slow, but
given that the execution is asynchronous now, this should be OK.

Fixes: #1308

src/basic/copy.c

@@ -423,6 +423,21 @@ int copy_directory_fd(int dirfd, const char *to, bool merge) {
         return fd_copy_directory(dirfd, NULL, &st, AT_FDCWD, to, st.st_dev, merge);
 }
 
+int copy_directory(const char *from, const char *to, bool merge) {
+        struct stat st;
+
+        assert(from);
+        assert(to);
+
+        if (lstat(from, &st) < 0)
+                return -errno;
+
+        if (!S_ISDIR(st.st_mode))
+                return -ENOTDIR;
+
+        return fd_copy_directory(AT_FDCWD, from, &st, AT_FDCWD, to, st.st_dev, merge);
+}
+
 int copy_file_fd(const char *from, int fdt, bool try_reflink) {
         _cleanup_close_ int fdf = -1;
         int r;

src/basic/copy.h

@@ -30,6 +30,7 @@ int copy_file_atomic(const char *from, const char *to, mode_t mode, bool replace
 int copy_tree(const char *from, const char *to, bool merge);
 int copy_tree_at(int fdf, const char *from, int fdt, const char *to, bool merge);
 int copy_directory_fd(int dirfd, const char *to, bool merge);
+int copy_directory(const char *from, const char *to, bool merge);
 int copy_bytes(int fdf, int fdt, uint64_t max_bytes, bool try_reflink);
 int copy_times(int fdf, int fdt);
 int copy_xattr(int fdf, int fdt);