fallocate bug?

[Zhu Han <schumi.han@xxxxxxxxx>]

Seems like xfs of CentOS 6.X occupies much more storage space than desired if fallocate is used against the file. Here is the step to reproduce it:

By the way, is it normal when the file is moved around after the preallocated region is filled with data? 

$ uname -r
2.6.32-220.7.1.el6.x86_64

$fallocate -n --offset 0 -l 1G file    ---->Write a little more data than the preallocated size

$ xfs_bmap -p -vv file
file:
 EXT: FILE-OFFSET      BLOCK-RANGE            AG AG-OFFSET              TOTAL FLAGS
   0: [0..2097151]:    2593408088..2595505239 21 (29420144..31517295) 2097152 10000

$ dd if=/dev/zero of=/tmp/file bs=1M count=1026 conv=fsync

$ xfs_bmap -p -vv file
file:
 EXT: FILE-OFFSET      BLOCK-RANGE            AG AG-OFFSET              TOTAL FLAGS
   0: [0..4194303]:    2709184016..2713378319 22 (23101408..27295711) 4194304 00000

$ du -h --apparent-size file
1.1G    file

$du -h file
2.0G

best regards,
韩竹(Zhu Han)