[Ocfs2-devel] [PATCH 2/2] ocfs2: Use ocfs2_rec_clusters in ocfs2_adjust_adjacent_records.

[Tao Ma <tao.ma@oracle.com>]

Joel Becker wrote:
> On Tue, Jul 21, 2009 at 03:42:06PM +0800, Tao Ma wrote:
>   
>> In ocfs2_adjust_adjacent_records, we will adjust adjacent records
>> according to the extent_list in the lower level. But actually
>> the lower level tree will either be a leaf or a branch. So we
>> shouldn't use ocfs2_is_empty_extent which is only valid for a
>> tree leaf. Use ocfs2_rec_clusters instead. We will meet with some
>> problem when the tree depth > 2.
>>     
>
> 	I think you mean "if we leave it as checking e_leaf_clusters,
> we'll have a problem rotating trees with depth > 2".  Is that right?
> Can interior nodes have these empty l_rec[0]s?  If they can't, perhaps
> we should be bugging?
>   
sorry, It should be tree_depth >=2.

ocfs2_adjust_adjacent_records is used to for rotation. And it only use 
e_cpos in most cases.
So we don't have a problem if the lower 16 bits of e_int_clusters isn't 
equal to 0 for a branch.
But if the low 16 bits are 0, this ocfs2_is_empty_extent will treat it 
as an empty record and use the l_recs[1] which will corrupt
the tree. So let me give you a test case I meet.

 Tree Depth: 2   Count: 23   Next Free Rec: 2
        ## Offset        Clusters       Block#
        0  0             9107457        28721
        1  9107457       1922049        28728
Tree Depth: 1   Count: 28   Next Free Rec: 28
        ## Offset        Clusters       Block#
        0  0             227105         28698
        1  227105        197405         28699
   ...
        26 8372225       542208         28725
        27 8914433       193024         28726

Tree Depth: 1   Count: 28   Next Free Rec: 10
        ## Offset        Clusters       Block#
        0  9107457       196608         28727
        1  9304065       204544         28729

In this case: 196608=0x30000, so if we use ocfs2_is_empty_extent will 
treat it as 0, and use 9394065.

Regards,
Tao