btrfs/010: what's the purpose of test case

[Xu Wang <xuw@redhat.com>]

Hi,

  I run the btrfs/010 for kernel 3.10, the result is failed. When I read the case, I think it may be wrong.
  So I post this letter, and wanna to verify it.

  The case(btrfs/010) firstly produced a file with some extents in a sub volume, then created 2 snaps of the
  sub volume. Then defrag the file in sub volume, and hope the extents numbers are same for sub volume, snap1
  and snap2.
  The btrfs's snapshot is based on cow, so defrag the original sub volume's file will not affect the file in 
  snapshot? Am I right? 
  If I am right, the operation "num_extent_orig=`_extent_count $subvol/foobar`" in btrfs/010 should be before
  the defrag operation. And I will send a patch to fix it.

  Best regards,

-- 
George Wang 王旭

Kernel Quantity Engineer
Red Hat Software (Beijing) Co.,Ltd
IRC:xuw
Tel:+86-010-62608041
Phone:15901231579
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