check for btrfs fs in should_default_to_snapshot

src/lxc/bdev/lxcbtrfs.c

@@ -40,7 +40,7 @@
 #include "lxcrsync.h"
 #include "utils.h"
 
-lxc_log_define(btrfs, lxc);
+lxc_log_define(lxcbtrfs, lxc);
 
 /* defined in lxccontainer.c: needs to become common helper */
 extern char *dir_new_path(char *src, const char *oldname, const char *name,

src/lxc/bdev/lxcoverlay.c

@@ -36,7 +36,7 @@
 #include "lxcrsync.h"
 #include "utils.h"
 
-lxc_log_define(overlay, lxc);
+lxc_log_define(lxcoverlay, lxc);
 
 static char *ovl_name;
 

src/lxc/lxccontainer.c

@@ -2833,6 +2833,10 @@ bool should_default_to_snapshot(struct lxc_container *c0,
 
 	snprintf(p0, l0, "%s/%s", c0->config_path, c0->name);
 	snprintf(p1, l1, "%s/%s", c1->config_path, c1->name);
+
+	if (!is_btrfs_fs(p0) || !is_btrfs_fs(p1))
+		return false;
+
 	return btrfs_same_fs(p0, p1) == 0;
 }