[btrfs-devel]A bug related to btrfs_search_slot and btrfs_extend_item

[Chris Mason]

On Tue, 23 Oct 2007 17:58:25 +0800
"Yan Zheng" <yanzheng at 21cn.com> wrote:

> Hello,
> 
> When we want to extent the size of some item in the tree, the typical
> function call sequence is:
>       ...
>       btrfs_search_slot((trans, root, key, path,  size_to_extent, 1);
>       ...
>      btrfs_extend_item(trans, root, path, size_to_extent);
> 
> There is a flaw in codes like this, to guarantee a leaf has enough
> free space, 'btrfs_search_slot' may call 'split_leaf' which split the
> leaf or insert a empty leaf. When 'split_leaf' insert a empty leaf,
> the lowest level of the btrfs_path points to the empty leaf. After
> 'btrfs_search_slot' return, 'btrfs_extend_item' is called, it will be
> in trouble to extent a non-exist item.

Yes, I've fixed a few mistakes in this area, but I think you're right,
I need to add a parameter to search_slot that indicates insert vs
extend.

Thanks for this test case!

-chris