Add libbtrfsutil

Currently, users wishing to manage Btrfs filesystems programatically
have to shell out to btrfs-progs and parse the output. This isn't ideal.
The goal of libbtrfsutil is to provide a library version of as many of
the operations of btrfs-progs as possible and to migrate btrfs-progs to
use it.

Rather than simply refactoring the existing btrfs-progs code, the code
has to be written from scratch for a couple of reasons:

* A lot of the btrfs-progs code was not designed with a nice library API
  in mind in terms of reusability, naming, and error reporting.
* libbtrfsutil is licensed under the LGPL, whereas btrfs-progs is under
  the GPL, which makes it dubious to directly copy or move the code.

Eventually, most of the low-level btrfs-progs code should either live in
libbtrfsutil or the shared kernel/userspace filesystem code, and
btrfs-progs will just be the CLI wrapper.

This first commit just includes the build system changes, license,
README, and error reporting helper.

Signed-off-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 76 insertions, 0 deletions

diff --git a/libbtrfsutil/btrfsutil.h b/libbtrfsutil/btrfsutil.h
new file mode 100644
index 00000000..867418f2
--- /dev/null
+++ b/libbtrfsutil/btrfsutil.h
@@ -0,0 +1,76 @@
+/*
+ * Copyright (C) 2018 Facebook
+ *
+ * This file is part of libbtrfsutil.
+ *
+ * libbtrfsutil is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * libbtrfsutil 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 Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with libbtrfsutil.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef BTRFS_UTIL_H
+#define BTRFS_UTIL_H
+
+#define BTRFS_UTIL_VERSION_MAJOR 1
+#define BTRFS_UTIL_VERSION_MINOR 0
+#define BTRFS_UTIL_VERSION_PATCH 0
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * enum btrfs_util_error - libbtrfsutil error codes.
+ *
+ * All functions in libbtrfsutil that can return an error return this type and
+ * set errno.
+ */
+enum btrfs_util_error {
+	BTRFS_UTIL_OK,
+	BTRFS_UTIL_ERROR_STOP_ITERATION,
+	BTRFS_UTIL_ERROR_NO_MEMORY,
+	BTRFS_UTIL_ERROR_INVALID_ARGUMENT,
+	BTRFS_UTIL_ERROR_NOT_BTRFS,
+	BTRFS_UTIL_ERROR_NOT_SUBVOLUME,
+	BTRFS_UTIL_ERROR_SUBVOLUME_NOT_FOUND,
+	BTRFS_UTIL_ERROR_OPEN_FAILED,
+	BTRFS_UTIL_ERROR_RMDIR_FAILED,
+	BTRFS_UTIL_ERROR_UNLINK_FAILED,
+	BTRFS_UTIL_ERROR_STAT_FAILED,
+	BTRFS_UTIL_ERROR_STATFS_FAILED,
+	BTRFS_UTIL_ERROR_SEARCH_FAILED,
+	BTRFS_UTIL_ERROR_INO_LOOKUP_FAILED,
+	BTRFS_UTIL_ERROR_SUBVOL_GETFLAGS_FAILED,
+	BTRFS_UTIL_ERROR_SUBVOL_SETFLAGS_FAILED,
+	BTRFS_UTIL_ERROR_SUBVOL_CREATE_FAILED,
+	BTRFS_UTIL_ERROR_SNAP_CREATE_FAILED,
+	BTRFS_UTIL_ERROR_SNAP_DESTROY_FAILED,
+	BTRFS_UTIL_ERROR_DEFAULT_SUBVOL_FAILED,
+	BTRFS_UTIL_ERROR_SYNC_FAILED,
+	BTRFS_UTIL_ERROR_START_SYNC_FAILED,
+	BTRFS_UTIL_ERROR_WAIT_SYNC_FAILED,
+};
+
+/**
+ * btrfs_util_strerror() - Convert a libtrfsutil error code to a string
+ * description.
+ * @err: The error to convert.
+ *
+ * Return: Error description.
+ */
+const char *btrfs_util_strerror(enum btrfs_util_error err);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* BTRFS_UTIL_H */