[PATCH] hfsplus: Supports freeing newly created tree head

[Edward Adam Davis]

On Fri, 17 Apr 2026 15:03:17 -0700, Viacheslav Dubeyko wrote:
> > hfs_bnode_put() does not support deallocating a newly created btree
> > head node; therefore, regardless of whether hfsplus_bnode_find() succeeds
> > or fails, it cannot effectively reclaim the memory allocated for a newly
> > created head node.
> > 
> > When finding a head node, if the node is a newly created one, we can use
> > hfs_bnode_free() to reclaim its memory.
> > 
> > [1]
> > BUG: memory leak
> > unreferenced object 0xffff88811cabc840 (size 96):
> >   backtrace (crc 3e2dadb7):
> >     __hfs_bnode_create+0x59/0x310 fs/hfsplus/bnode.c:469
> >     hfsplus_bnode_find+0x13e/0x580 fs/hfsplus/bnode.c:547
> >     hfsplus_btree_open+0x2fa/0x6d0 fs/hfsplus/btree.c:382
> >     hfsplus_fill_super+0x272/0x880 fs/hfsplus/super.c:548
> 
> I need slightly more detailed and clear explanation how the issue has been
> happened and why we need to fix it in a such way. Currently, I don't have the
> complete picture how this happened. I am sure that you have the complete
> picture. :) Could you please share what you have in your mind? :) Don't hide the
> wisdom. ;)
    fc_mount()
     vfs_get_tree()
      get_tree_bdev_flags()
       hfsplus_fill_super() 
        hfsplus_btree_open() 
         hfsplus_bnode_find(tree, HFSPLUS_TREE_HEAD) 
          __hfs_bnode_create()
	   ...
	   node->this = cnid; // cnid is HFSPLUS_TREE_HEAD, it is 0
	   ...
	  ...
	  desc = (struct hfs_bnode_desc *)(kmap_local_page(node->page[0])
	  node->type = desc->type;
	  switch (node->type) {
	  ...
	  default:  // because node->type is 127, so run here
	  	goto node_error;
	  ...
	  hfs_bnode_put()
	   ...
	   if (test_bit(HFS_BNODE_DELETED, &node->flags)) { /* head node not set HFS_BNODE_DELETED flag
							     * so, the node will never be freed.
							     * Furthermore, even if the node were marked
							     * with the HFS_BNODE_DELETED flag, hfs_bmap_free()
							     * would still trigger BUG_ON(!node->this).
	   						     */

Edward
BR