[gparted] Enhance calculation of significant unallocated space (#499202)
- From: Curtis Gedak <gedakc src gnome org>
- To: commits-list gnome org
- Cc:
- Subject: [gparted] Enhance calculation of significant unallocated space (#499202)
- Date: Mon, 18 Jun 2012 18:45:45 +0000 (UTC)
commit b5c80f18a9ce27fda2b11e9b590d7f856209ac32
Author: Mike Fleetwood <mike fleetwood googlemail com>
Date: Tue Jun 5 19:32:52 2012 +0100
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
HACKING | 42 ++++++++++++++++++++++++++++++++++++++++++
src/Partition.cc | 37 ++++++++++++++++++++++++++++++-------
2 files changed, 72 insertions(+), 7 deletions(-)
---
diff --git a/HACKING b/HACKING
index 6704ffc..3f2d29f 100644
--- a/HACKING
+++ b/HACKING
@@ -17,3 +17,45 @@ even when it's only one character. =)
Thanks,
Curtis
+
+
+
+partition usage and unallocated space
+=====================================
+
+After addressing bug #499202 GParted now also displays unallocated space
+as well as used and unused space for recognised file systems. The
+unallocated space is shown graphically and the numeric figure is shown
+in the Information Dialog if it is greater than zero. Additionally a
+warning is reported if the unallocated space is considered too much.
+See the code and commit messages for more details.
+
+Worked example of partition and file system usage for a newly created
+jfs file system in a 200 MiB partition reporting a small amount of
+unallocated space:
+
+# sfdisk -s /dev/sda9
+204800
+
+# echo dm | jfs_debugfs /dev/sda9 | egrep 'Block Size:|dn_mapsize:|dn_nfree:'
+Aggregate Block Size: 4096
+[1] dn_mapsize: 0x0000000c6cb [9] dn_agheigth: 0
+[2] dn_nfree: 0x0000000c6a3 [10] dn_agwidth: 1
+
+Partition size = 204800 (1K blocks) = 409600 (512 byte sectors)
+FS size = 0x0c6cb (4K blocks)
+ = 50891 (4K blocks) = 407128 (512 byte sectors)
+FS free = 0x0c6a3 (4K blocks)
+ = 50851 (4K blocks) = 406808 (512 byte sectors)
+
+Calculation:
+size = ptn_size = 409600 = 200.00 MiB
+used = fs_size - fs_free = 407128 - 406808 = 320 = 160.00 KiB
+unused = fs_free = 406808 = 198.64 MiB
+unallocated = ptn_size - fs_size = 409600 - 407128 = 2472 = 1.21 MiB
+
+Figures displayed in the Information dialog:
+Size: 200.00 MiB
+Used: 160.00 KiB ( 0% )
+Unused: 198.64 MiB ( 99% )
+Unallocated: 1.21 MiB ( 1% )
diff --git a/src/Partition.cc b/src/Partition.cc
index c763161..d37d6f5 100644
--- a/src/Partition.cc
+++ b/src/Partition.cc
@@ -21,8 +21,6 @@
namespace GParted
{
-#define SIGNIFICANT_UNALLOCATED_FRACTION 0.05
-
Partition::Partition()
{
Reset() ;
@@ -293,13 +291,38 @@ bool Partition::compare_paths( const Glib::ustring & A, const Glib::ustring & B
}
//Return threshold of sectors which is considered above the intrinsic
-// level for a file system which "fills" the partition.
+// level for a file system which "fills" the partition. Calculation
+// is:
+// %age of partition size , when
+// 5% , ptn size <= 100 MiB
+// linear scaling from 5% down to 2%, 100 MiB < ptn size <= 1 GiB
+// 2% , 1 GiB < ptn size
Sector Partition::get_significant_unallocated_sectors() const
{
- Sector length = get_sector_length() ;
- if ( length >= 0 )
- return Utils::round( length * SIGNIFICANT_UNALLOCATED_FRACTION ) ;
- return 0 ;
+ const double HIGHER_UNALLOCATED_FRACTION = 0.05 ;
+ const double LOWER_UNALLOCATED_FRACTION = 0.02 ;
+ Sector length = get_sector_length() ;
+ Byte_Value byte_len = length * sector_size ;
+ if ( byte_len <= 0 )
+ {
+ return 0 ;
+ }
+ else if ( byte_len <= 100 * MEBIBYTE )
+ {
+ return Utils::round( length * HIGHER_UNALLOCATED_FRACTION ) ;
+ }
+ else if ( byte_len <= 1 * GIBIBYTE )
+ {
+ double fraction = ( HIGHER_UNALLOCATED_FRACTION - LOWER_UNALLOCATED_FRACTION ) -
+ ( byte_len - 100 * MEBIBYTE ) * ( HIGHER_UNALLOCATED_FRACTION - LOWER_UNALLOCATED_FRACTION ) /
+ ( 1 * GIBIBYTE - 100 * MEBIBYTE ) +
+ LOWER_UNALLOCATED_FRACTION ;
+ return Utils::round( length * fraction ) ;
+ }
+ else
+ {
+ return Utils::round( length * LOWER_UNALLOCATED_FRACTION ) ;
+ }
}
Partition::~Partition()
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