tree 70be1bb231f4cc2e673920774e759359f3dcf1a5
parent c8b978188c9a0fd3d535c13debd19d522b726f1f
author Yan Zheng <zheng.yan@oracle.com> 1225306145 -0400
committer Chris Mason <chris.mason@oracle.com> 1225306145 -0400

Btrfs: Improve space balancing code

This patch improves the space balancing code to keep more sharing
of tree blocks. The only case that breaks sharing of tree blocks is
data extents get fragmented during balancing. The main changes in
this patch are:

Add a 'drop sub-tree' function. This solves the problem in old code
that BTRFS_HEADER_FLAG_WRITTEN check breaks sharing of tree block.

Remove relocation mapping tree. Relocation mappings are stored in
struct btrfs_ref_path and updated dynamically during walking up/down
the reference path. This reduces CPU usage and simplifies code.

This patch also fixes a bug. Root items for reloc trees should be
updated in btrfs_free_reloc_root.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>