test: introduce TEST-83-BTRFS

The Ubuntu CIs are deny-listed because the shipped
btrfs-progs is too old, i.e. doesn't support the
recently-added 'filesystem mkswapfile' command.

src/test/meson.build

@@ -221,6 +221,10 @@ executables += [
                 'sources' : files('test-btrfs.c'),
                 'type' : 'manual',
         },
+        test_template + {
+                'sources' : files('test-btrfs-physical-offset.c'),
+                'type' : 'manual',
+        },
         test_template + {
                 'sources' : files('test-cap-list.c') +
                             generated_gperf_headers,

src/test/test-btrfs-physical-offset.c

@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <fcntl.h>
+
+#include "btrfs-util.h"
+#include "fd-util.h"
+#include "format-util.h"
+#include "log.h"
+#include "memory-util.h"
+
+int main(int argc, char *argv[]) {
+        _cleanup_close_ int fd = -EBADF;
+        uint64_t offset;
+        int r;
+
+        assert(argc == 2);
+        assert(!isempty(argv[1]));
+
+        fd = open(argv[1], O_RDONLY|O_CLOEXEC|O_NOCTTY);
+        if (fd < 0) {
+                log_error_errno(fd, "Failed to open '%s': %m", argv[1]);
+                return EXIT_FAILURE;
+        }
+
+        r = btrfs_get_file_physical_offset_fd(fd, &offset);
+        if (r < 0) {
+                log_error_errno(r, "Failed to get physical offset of '%s': %m", argv[1]);
+                return EXIT_FAILURE;
+        }
+
+        printf("%" PRIu64 "\n", offset / page_size());
+        return EXIT_SUCCESS;
+}