lxc-destroy: actually work if underlying fs is overlayfs

src/lxc/utils.c

@@ -29,6 +29,7 @@
 #include <stddef.h>
 #include <string.h>
 #include <sys/types.h>
+#include <sys/vfs.h>
 #include <sys/stat.h>
 #include <sys/mman.h>
 #include <sys/param.h>
@@ -46,7 +47,7 @@
 
 lxc_log_define(lxc_utils, lxc);
 
-static int _recursive_rmdir_onedev(char *dirname, dev_t pdev)
+static int _recursive_rmdir(char *dirname, dev_t pdev, bool onedev)
 {
 	struct dirent dirent, *direntp;
 	DIR *dir;
@@ -76,20 +77,21 @@ static int _recursive_rmdir_onedev(char *dirname, dev_t pdev)
 			failed=1;
 			continue;
 		}
+
 		ret = lstat(pathname, &mystat);
 		if (ret) {
 			ERROR("%s: failed to stat %s", __func__, pathname);
 			failed=1;
 			continue;
 		}
-		if (mystat.st_dev != pdev)
+		if (onedev && mystat.st_dev != pdev)
 			continue;
 		if (S_ISDIR(mystat.st_mode)) {
-			if (_recursive_rmdir_onedev(pathname, pdev) < 0)
+			if (_recursive_rmdir(pathname, pdev, onedev) < 0)
 				failed=1;
 		} else {
 			if (unlink(pathname) < 0) {
-				ERROR("%s: failed to delete %s", __func__, pathname);
+				SYSERROR("%s: failed to delete %s", __func__, pathname);
 				failed=1;
 			}
 		}
@@ -109,17 +111,41 @@ static int _recursive_rmdir_onedev(char *dirname, dev_t pdev)
 	return failed ? -1 : 0;
 }
 
+/* we have two different magic values for overlayfs, yay */
+#define OVERLAYFS_SUPER_MAGIC 0x794c764f
+#define OVERLAY_SUPER_MAGIC 0x794c7630
+/*
+ * In overlayfs, st_dev is unreliable.  so on overlayfs we don't do
+ * the lxc_rmdir_onedev()
+ */
+static bool is_native_overlayfs(const char *path)
+{
+	struct statfs sb;
+
+	if (statfs(path, &sb) < 0)
+		return false;
+	if (sb.f_type == OVERLAYFS_SUPER_MAGIC ||
+			sb.f_type == OVERLAY_SUPER_MAGIC)
+		return true;
+	return false;
+}
+
 /* returns 0 on success, -1 if there were any failures */
 extern int lxc_rmdir_onedev(char *path)
 {
 	struct stat mystat;
+	bool onedev = true;
+
+	if (is_native_overlayfs(path)) {
+		onedev = false;
+	}
 
 	if (lstat(path, &mystat) < 0) {
 		ERROR("%s: failed to stat %s", __func__, path);
 		return -1;
 	}
 
-	return _recursive_rmdir_onedev(path, mystat.st_dev);
+	return _recursive_rmdir(path, mystat.st_dev, onedev);
 }
 
 static int mount_fs(const char *source, const char *target, const char *type)