tree 81c108e60e6f66575dd7fbc763f8063a446f28f6
parent 6f3f008d46607e64b760b40fb1f3c9ff510ada8d
author Darrick J. Wong <darrick.wong@oracle.com> 1406047256 -0400
committer Theodore Ts'o <tytso@mit.edu> 1406047256 -0400

e4defrag: backwards-allocated files should be defragmented too

Currently, e4defrag avoids increasing file fragmentation by comparing
the number of runs of physical extents of both the original and the
donor files.  Unfortunately, there is a bug in the routine that counts
physical extents, since it doesn't look at the logical block offsets
of the extents.  Therefore, a file whose blocks were allocated in
reverse order will be seen as only having one big physical extent, and
therefore will not be defragmented.

Fix the counting routine to consider logical extent offset so that we
defragment backwards-allocated files.  This could be problematic if we
ever gain the ability to lay out logically sparse extents in a
physically contiguous manner, but presumably one wouldn't call defrag
on such a file.

Reported-by: Xiaoguang Wang <wangxg.fnst@cn.fujitsu.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>