Btrfs: remove BUG_ON in __add_tree_block

The BUG_ON() can be triggered when the caller is processing an invalid
extent inline ref, e.g.

a shared data ref is offered instead of an extent data ref, such that
it tries to find a non-existent tree block and then btrfs_search_slot
returns 1 for no such item.

This replaces the BUG_ON() with a WARN() followed by calling
btrfs_print_leaf() to show more details about what's going on and
returning -EINVAL to upper callers.
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/relocation.c

@@ -32,6 +32,7 @@
 #include "free-space-cache.h"
 #include "inode-map.h"
 #include "qgroup.h"
+#include "print-tree.h"
 
 /*
  * backref_node, mapping_node and tree_block start with this
@@ -3483,7 +3484,16 @@ static int __add_tree_block(struct reloc_control *rc,
 			goto again;
 		}
 	}
-	BUG_ON(ret);
+	if (ret) {
+		ASSERT(ret == 1);
+		btrfs_print_leaf(path->nodes[0]);
+		btrfs_err(fs_info,
+	     "tree block extent item (%llu) is not found in extent tree",
+		     bytenr);
+		WARN_ON(1);
+		ret = -EINVAL;
+		goto out;
+	}
 
 	ret = add_tree_block(rc, &key, path, blocks);
 out: