diff --git a/fs/erofs/inode.c b/fs/erofs/inode.c
index 31ac3a7..a552399 100644
--- a/fs/erofs/inode.c
+++ b/fs/erofs/inode.c
@@ -176,7 +176,7 @@
 	}
 
 	if (vi->datalayout == EROFS_INODE_CHUNK_BASED) {
-		if (!(vi->chunkformat & EROFS_CHUNK_FORMAT_ALL)) {
+		if (vi->chunkformat & ~EROFS_CHUNK_FORMAT_ALL) {
 			erofs_err(inode->i_sb,
 				  "unsupported chunk format %x of nid %llu",
 				  vi->chunkformat, vi->nid);
diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c
index 9fb98d8..7a6df35 100644
--- a/fs/erofs/zmap.c
+++ b/fs/erofs/zmap.c
@@ -369,7 +369,8 @@
 	if (compacted_4b_initial == 32 / 4)
 		compacted_4b_initial = 0;
 
-	if (vi->z_advise & Z_EROFS_ADVISE_COMPACTED_2B)
+	if ((vi->z_advise & Z_EROFS_ADVISE_COMPACTED_2B) &&
+	    compacted_4b_initial < totalidx)
 		compacted_2b = rounddown(totalidx - compacted_4b_initial, 16);
 	else
 		compacted_2b = 0;
diff --git a/include/trace/events/erofs.h b/include/trace/events/erofs.h
index bf9806f..db4f2ce 100644
--- a/include/trace/events/erofs.h
+++ b/include/trace/events/erofs.h
@@ -35,20 +35,20 @@
 	TP_STRUCT__entry(
 		__field(dev_t,		dev	)
 		__field(erofs_nid_t,	nid	)
-		__field(const char *,	name	)
+		__string(name,		dentry->d_name.name	)
 		__field(unsigned int,	flags	)
 	),
 
 	TP_fast_assign(
 		__entry->dev	= dir->i_sb->s_dev;
 		__entry->nid	= EROFS_I(dir)->nid;
-		__entry->name	= dentry->d_name.name;
+		__assign_str(name, dentry->d_name.name);
 		__entry->flags	= flags;
 	),
 
 	TP_printk("dev = (%d,%d), pnid = %llu, name:%s, flags:%x",
 		show_dev_nid(__entry),
-		__entry->name,
+		__get_str(name),
 		__entry->flags)
 );