1 files changed, 110 insertions, 0 deletions
diff --git a/lib/btrfs.c b/lib/btrfs.c
new file mode 100644
index 0000000..0391598
--- /dev/null
+++ b/lib/btrfs.c
@@ -0,0 +1,110 @@
+#include <linux/btrfs_tree.h>
+#include <linux/magic.h>
+#include <sys/statfs.h>
+#include <stdbool.h>
+
+#include "prototypes.h"
+
+static bool path_exists(const char *p)
+{
+	struct stat sb;
+
+	return stat(p, &sb) == 0;
+}
+
+static const char *btrfs_cmd(void)
+{
+	const char *const btrfs_paths[] = {"/sbin/btrfs",
+		"/bin/btrfs", "/usr/sbin/btrfs", "/usr/bin/btrfs", NULL};
+	const char *p;
+	int i;
+
+	for (i = 0, p = btrfs_paths[i]; p; i++, p = btrfs_paths[i])
+		if (path_exists(p))
+			return p;
+
+	return NULL;
+}
+
+static int run_btrfs_subvolume_cmd(const char *subcmd, const char *arg1, const char *arg2)
+{
+	int status = 0;
+	const char *cmd = btrfs_cmd();
+	const char *argv[] = {
+		"btrfs",
+		"subvolume",
+		subcmd,
+		arg1,
+		arg2,
+		NULL
+	};
+
+	if (!cmd || access(cmd, X_OK)) {
+		return 1;
+	}
+
+	if (run_command(cmd, argv, NULL, &status))
+		return -1;
+	return status;
+}
+
+
+int btrfs_create_subvolume(const char *path)
+{
+	return run_btrfs_subvolume_cmd("create", path, NULL);
+}
+
+
+int btrfs_remove_subvolume(const char *path)
+{
+	return run_btrfs_subvolume_cmd("delete", "-C", path);
+}
+
+
+/* Adapted from btrfsprogs */
+/*
+ * This intentionally duplicates btrfs_util_is_subvolume_fd() instead of opening
+ * a file descriptor and calling it, because fstat() and fstatfs() don't accept
+ * file descriptors opened with O_PATH on old kernels (before v3.6 and before
+ * v3.12, respectively), but stat() and statfs() can be called on a path that
+ * the user doesn't have read or write permissions to.
+ *
+ * returns:
+ *   1 - btrfs subvolume
+ *   0 - not btrfs subvolume
+ *  -1 - error
+ */
+int btrfs_is_subvolume(const char *path)
+{
+	struct stat st;
+	int ret;
+
+	ret = is_btrfs(path);
+	if (ret <= 0)
+		return ret;
+
+	ret = stat(path, &st);
+	if (ret == -1)
+		return -1;
+
+	if (st.st_ino != BTRFS_FIRST_FREE_OBJECTID || !S_ISDIR(st.st_mode)) {
+		return 0;
+	}
+
+	return 1;
+}
+
+
+/* Adapted from btrfsprogs */
+int is_btrfs(const char *path)
+{
+	struct statfs sfs;
+	int ret;
+
+	ret = statfs(path, &sfs);
+	if (ret == -1)
+		return -1;
+
+	return sfs.f_type == BTRFS_SUPER_MAGIC;
+}
+