The HACKING file should be hints for making changes to the code base and
associated processes. A overview of how GParted handled unallocated
space was not that. Also now the size of a JFS is accurately calculated
using JFS as an example of a file system with intrinsic unallocated
space is no longer valid. Therefore removed from the HACKING file.
Instead add the original commit message as an extended comment to method
calc_significant_unallocated_sectors().
Closes!50 - Calculate JFS size accurately
Most file systems report intrinsic unallocated space using the statvfs()
system call when mounted, but not using their own tools. They are:
ext2/3/4, fat16/32, hfs, nilfs2, reiserfs and xfs. Showing either a
little or no unallocated space, depending on whether a file system is
mounted or not, could be confusing to the user.
When all file systems are created filling their partitions the unused
figure reported by statvfs() and their own tools are the same or very
close. Also the used plus unallocated figure from statvfs() agrees with
the used figure from their own tools.
For all file systems don't display intrinsic unallocated space (that
below the threshold of 2 to 5%), instead include it as used space. As
soon as the amount of unallocated space becomes significant display it
everywhere and also trigger the warning.
For display purposes always use the new Partition methods:
get_sectors_used(), get_sectors_unused(), and get_sectors_unallocated().
When calculating new usage figures during Paste and Resize/Move
operations directly access sectors_used, sectors_unused and
sectors_unallocated members.
Bug #499202 - gparted does not see the difference if partition size
differs from filesystem size
Many file systems report differing percentages of unallocated space over
a range of sizes, as well differing figures using their own specific
tools or using statvfs() system call when mounted.
File systems reporting intrinsic unallocated space using their specific
tools are: jfs, lvm2 pv and ntfs. LVM2 PV has the largest amount of
unallocated space with its default Physical Extent size of 4 MiB. For a
100 MiB partition it has 4.0% unallocated space.
File systems reporting intrinsic unallocated space using the statvfs()
system call when mounted are: ext2/3/4, fat16/32, hfs, jfs, nilfs2,
ntfs, reiserfs, and xfs. Xfs has the worst identified unallocated space
of ~4.7% in a 100 MiB partition. Ext2/3 exhibit unusual behaviour by
reporting unallocated space of ~4.6% in a 100 MiB partition falling to a
constant percentage of ~1.8% for sizes of 1 GiB and above.
Update the calculation for used to estimate the maximum size of
intrinsic unallocated space. Limit is now 5% for partitions smaller
than 100 MiB, 2% for partitions larger than 1 GiB and linear scaling of
the percentage between. Will still get false unallocated space warnings
for mounted xfs file systems and lvm2 pvs smaller than 100 MiB.
Also add a short note and worked example calculation of unallocated
space to the HACKING file.
Bug #499202 - gparted does not see the difference if partition size
differs from filesystem size
Mike Fleetwood