tree 2ae66461455a750baa970d02589cb393d27ffbd1
parent 2a0f7f5769992bae5b3f97157fd80b2b943be485
author Chris Mason <chris.mason@oracle.com> 1318347700 -0400
committer Chris Mason <chris.mason@oracle.com> 1318347955 -0400

Btrfs: make sure not to defrag extents past i_size

The btrfs file defrag code will loop through the extents and
force COW on them.  But there is a concurrent truncate in the middle of
the defrag, it might end up defragging the same range over and over
again.

The problem is that writepage won't go through and do anything on pages
past i_size, so the cow won't happen, so the file will appear to still
be fragmented.  defrag will end up hitting the same extents again and
again.

In the worst case, the truncate can actually live lock with the defrag
because the defrag keeps creating new ordered extents which the truncate
code keeps waiting on.

The fix here is to make defrag check for i_size inside the main loop,
instead of just once before the looping starts.

Signed-off-by: Chris Mason <chris.mason@oracle.com>