Enhance calculation of significant unallocated space (#499202)
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
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HACKING
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HACKING
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@ -17,3 +17,45 @@ even when it's only one character. =)
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Thanks,
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Curtis
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partition usage and unallocated space
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=====================================
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After addressing bug #499202 GParted now also displays unallocated space
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as well as used and unused space for recognised file systems. The
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unallocated space is shown graphically and the numeric figure is shown
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in the Information Dialog if it is greater than zero. Additionally a
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warning is reported if the unallocated space is considered too much.
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See the code and commit messages for more details.
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Worked example of partition and file system usage for a newly created
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jfs file system in a 200 MiB partition reporting a small amount of
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unallocated space:
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# sfdisk -s /dev/sda9
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204800
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# echo dm | jfs_debugfs /dev/sda9 | egrep 'Block Size:|dn_mapsize:|dn_nfree:'
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Aggregate Block Size: 4096
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[1] dn_mapsize: 0x0000000c6cb [9] dn_agheigth: 0
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[2] dn_nfree: 0x0000000c6a3 [10] dn_agwidth: 1
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Partition size = 204800 (1K blocks) = 409600 (512 byte sectors)
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FS size = 0x0c6cb (4K blocks)
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= 50891 (4K blocks) = 407128 (512 byte sectors)
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FS free = 0x0c6a3 (4K blocks)
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= 50851 (4K blocks) = 406808 (512 byte sectors)
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Calculation:
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size = ptn_size = 409600 = 200.00 MiB
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used = fs_size - fs_free = 407128 - 406808 = 320 = 160.00 KiB
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unused = fs_free = 406808 = 198.64 MiB
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unallocated = ptn_size - fs_size = 409600 - 407128 = 2472 = 1.21 MiB
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Figures displayed in the Information dialog:
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Size: 200.00 MiB
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Used: 160.00 KiB ( 0% )
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Unused: 198.64 MiB ( 99% )
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Unallocated: 1.21 MiB ( 1% )
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@ -21,8 +21,6 @@
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namespace GParted
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{
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#define SIGNIFICANT_UNALLOCATED_FRACTION 0.05
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Partition::Partition()
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{
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Reset() ;
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@ -293,13 +291,38 @@ bool Partition::compare_paths( const Glib::ustring & A, const Glib::ustring & B
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}
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//Return threshold of sectors which is considered above the intrinsic
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// level for a file system which "fills" the partition.
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// level for a file system which "fills" the partition. Calculation
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// is:
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// %age of partition size , when
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// 5% , ptn size <= 100 MiB
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// linear scaling from 5% down to 2%, 100 MiB < ptn size <= 1 GiB
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// 2% , 1 GiB < ptn size
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Sector Partition::get_significant_unallocated_sectors() const
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{
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Sector length = get_sector_length() ;
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if ( length >= 0 )
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return Utils::round( length * SIGNIFICANT_UNALLOCATED_FRACTION ) ;
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return 0 ;
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const double HIGHER_UNALLOCATED_FRACTION = 0.05 ;
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const double LOWER_UNALLOCATED_FRACTION = 0.02 ;
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Sector length = get_sector_length() ;
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Byte_Value byte_len = length * sector_size ;
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if ( byte_len <= 0 )
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{
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return 0 ;
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}
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else if ( byte_len <= 100 * MEBIBYTE )
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{
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return Utils::round( length * HIGHER_UNALLOCATED_FRACTION ) ;
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}
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else if ( byte_len <= 1 * GIBIBYTE )
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{
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double fraction = ( HIGHER_UNALLOCATED_FRACTION - LOWER_UNALLOCATED_FRACTION ) -
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( byte_len - 100 * MEBIBYTE ) * ( HIGHER_UNALLOCATED_FRACTION - LOWER_UNALLOCATED_FRACTION ) /
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( 1 * GIBIBYTE - 100 * MEBIBYTE ) +
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LOWER_UNALLOCATED_FRACTION ;
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return Utils::round( length * fraction ) ;
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}
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else
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{
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return Utils::round( length * LOWER_UNALLOCATED_FRACTION ) ;
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}
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}
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Partition::~Partition()
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