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Use btrfs filesystem show --raw to read usage (!105) 

'btrfs filesystem show' only used to report rounded human readable size
figures.  Therefore the actual figure could have been anywhere within
the rounding limit.  GParted also applied a heuristic to snap the file
system size figure to the partition size if the partition size was
within the rounding limit of the reported file system size [1].

btrfs-progs v4.1 added the --raw option to print the figures in bytes
[2][3][4].
    # btrfs filesystem show --raw /dev/sdb1
    Label: none  uuid: 003a619e-856f-4b9c-bd29-4d0ae0296d66
            Total devices 2 FS bytes used 178765824
            devid    1 size 2147483648 used 239861760 path /dev/sdb1
            devid    2 size 2147483648 used 436207616 path /dev/sdc1

Since the oldest supported distributions now use btrfs-progs v4.5.3 and
later (see the distribution End-of-Life table in the previous commit
message), unconditionally use this to get accurate figures.

[1] 7fc16a1b69
    Handle btrfs tools rounding of figures (#499202)
[2] btrfs-progs: Allow "filesystem show" command to handle different units
    https://git.kernel.org/pub/scm/linux/kernel/git/kdave/btrfs-progs.git/commit/?id=15379fa2257bf937cf7830c0b1b79f2daf5df72c
[3] btrfs-progs: docs: new size options for fi show
    https://git.kernel.org/pub/scm/linux/kernel/git/kdave/btrfs-progs.git/commit/?id=81225f11d9ea58590476612e69211113ddb9b943
[4] Btrfs progs release 4.1
    https://lore.kernel.org/linux-btrfs/20150622150023.GX6761@twin.jikos.cz/

Closes !105 - Update used btrfs file system commands, new minimum is
              btrfs-progs 4.5
This commit is contained in:
Mike Fleetwood 2022-07-25 20:26:37 +01:00 committed by Curtis Gedak
parent be895fb98e
commit db5df60f22
2 changed files with 83 additions and 177 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
include/btrfs.h
View File

@ -52,10 +52,9 @@ public:
private: private:
static const BTRFS_Device & get_cache_entry( const Glib::ustring & path ) ; static const BTRFS_Device & get_cache_entry( const Glib::ustring & path ) ;
static Byte_Value btrfs_size_to_num( Glib::ustring str, Byte_Value ptn_bytes, bool scale_up ) ;
static gdouble btrfs_size_max_delta( Glib::ustring str ) ;
static gdouble btrfs_size_to_gdouble( Glib::ustring str ) ;
}; };
} //GParted } //GParted
#endif /* GPARTED_BTRFS_H */ #endif /* GPARTED_BTRFS_H */

255
src/btrfs.cc
View File

@ -138,112 +138,108 @@ bool btrfs::check_repair( const Partition & partition, OperationDetail & operati
operationdetail, EXEC_CHECK_STATUS); operationdetail, EXEC_CHECK_STATUS);
} }
void btrfs::set_used_sectors( Partition & partition )
{
//Called when the file system is unmounted *and* when mounted.
//
// Btrfs has a volume manager layer within the file system which allows it to
// provide multiple levels of data redundancy, RAID levels, and use multiple
// devices both of which can be changed while the file system is mounted. To
// achieve this btrfs has to allocate space at two different levels: (1) chunks
// of 256 MiB or more at the volume manager level; and (2) extents at the file
// data level.
// References:
// * Btrfs: Working with multiple devices
// https://lwn.net/Articles/577961/
// * Btrfs wiki: Glossary
// https://btrfs.wiki.kernel.org/index.php/Glossary
//
// This makes the question of how much disk space is being used in an individual
// device a complicated question to answer. Further, the current btrfs tools
// don't provide the required information.
//
// Btrfs filesystem show only provides space usage information at the chunk level
// per device. At the file extent level only a single figure for the whole file
// system is provided. It also reports size of the data and metadata being
// stored, not the larger figure of the amount of space taken after redundancy is
// applied. So it is impossible to answer the question of how much disk space is
// being used in an individual device. Example output:
//
// Label: none uuid: 36eb51a2-2927-4c92-820f-b2f0b5cdae50
// Total devices 2 FS bytes used 156.00KB
// devid 2 size 2.00GB used 512.00MB path /dev/sdb2
// devid 1 size 2.00GB used 240.75MB path /dev/sdb1
//
// Guesstimate the per device used figure as the fraction of the file system wide
// extent usage based on chunk usage per device.
//
// Positives:
// 1) Per device used figure will correctly be between zero and allocated chunk
// size.
//
// Known inaccuracies:
// [for single and multi-device btrfs file systems]
// 1) Btrfs filesystem show reports file system wide file extent usage without
// considering redundancy applied to that data. (By default btrfs stores two
// copies of metadata and one copy of data).
// 2) At minimum size when all data has been consolidated there will be a few
// partly filled chunks of 256 MiB or more for data and metadata of each
// storage profile (RAID level).
// [for multi-device btrfs file systems only]
// 3) Data may be far from evenly distributed between the chunks on multiple
// devices.
// 4) Extents can be and are relocated to other devices within the file system
// when shrinking a device.
Utils::execute_command("btrfs filesystem show " + Glib::shell_quote(partition.get_path()),
output, error, true);
//In many cases the exit status doesn't reflect valid output or an error condition
// so rely on parsing the output to determine success.
//Extract the per device size figure. Guesstimate the per device used void btrfs::set_used_sectors(Partition& partition)
// figure as discussed above. Example output: {
// Called when the file system is unmounted *and* when mounted.
// //
// Label: none uuid: 36eb51a2-2927-4c92-820f-b2f0b5cdae50 // Btrfs has a volume manager layer within the file system which allows it to
// Total devices 2 FS bytes used 156.00KB // provide multiple levels of data redundancy, RAID levels, and use multiple
// devid 2 size 2.00GB used 512.00MB path /dev/sdb2 // devices both of which can be changed while the file system is mounted. To
// devid 1 size 2.00GB used 240.75MB path /dev/sdb1 // achieve this btrfs has to allocate space at two different levels: (1) chunks of
// 256 MiB or more at the volume manager level; and (2) extents at the metadata
// and file data level.
// References:
// * Btrfs: Working with multiple devices
// https://lwn.net/Articles/577961/
// * Btrfs wiki: Glossary
// https://btrfs.wiki.kernel.org/index.php/Glossary
//
// This makes the question of how much disk space is being used in an individual
// device a complicated question to answer. Further, the current btrfs tools
// don't provide the required information.
//
// Btrfs filesystem show only provides space usage information at the chunk level
// per device. At the file extent level only a single figure for the whole file
// system is provided. It also reports size of the data and metadata being
// stored, not the larger figure of the amount of space taken after redundancy is
// applied. So it is impossible to answer the question of how much disk space is
// being used in an individual device. Example:
//
// # btrfs filesystem show --raw /dev/sdb1
// Label: none uuid: 003a619e-856f-4b9c-bd29-4d0ae0296d66
// Total devices 2 FS bytes used 178765824
// devid 1 size 2147483648 used 239861760 path /dev/sdb1
// devid 2 size 2147483648 used 436207616 path /dev/sdc1
//
// Guesstimate the per device used figure as the fraction of the file system wide
// extent usage based on chunk usage per device.
//
// Positives:
// 1) Per device used figure will correctly be between zero and allocated chunk
// size.
//
// Known inaccuracies:
// [for single and multi-device btrfs file systems]
// 1) Btrfs filesystem show reports file system wide file extent usage without
// considering redundancy applied to that data. (By default btrfs stores two
// copies of metadata and one copy of data).
// 2) At minimum size when all data has been consolidated there will be a few
// partly filled chunks of 256 MiB or more for data and metadata of each
// storage profile (RAID level).
// [for multi-device btrfs file systems only]
// 3) Data may be far from evenly distributed between the chunks on multiple
// devices.
// 4) Extents can be and are relocated to other devices within the file system
// when shrinking a device.
Utils::execute_command("btrfs filesystem show --raw " + Glib::shell_quote(partition.get_path()),
output, error, true);
// In many cases the exit status doesn't reflect valid output or an error
// condition so rely on parsing the output to determine success.
// Extract the per device size figure. Guesstimate the per device used
// figure as discussed above. Example:
//
// # btrfs filesystem show --raw /dev/sdb1
// Label: none uuid: 003a619e-856f-4b9c-bd29-4d0ae0296d66
// Total devices 2 FS bytes used 178765824
// devid 1 size 2147483648 used 239861760 path /dev/sdb1
// devid 2 size 2147483648 used 436207616 path /dev/sdc1
// //
// Calculations: // Calculations:
// ptn fs size = devid size // ptn fs size = devid size
// ptn fs used = total fs used * devid used / sum devid used // ptn fs used = total fs used * devid used / sum devid used
Byte_Value ptn_size = partition .get_byte_length() ; long long total_fs_used = -1;
Byte_Value total_fs_used = -1 ; //total fs used long long sum_devid_used = 0;
Byte_Value sum_devid_used = 0 ; //sum devid used long long devid_used = -1;
Byte_Value devid_used = -1 ; //devid used long long devid_size = -1;
Byte_Value devid_size = -1 ; //devid size
//Btrfs file system wide used bytes (extents and items) // Btrfs file system wide used bytes (extents and items)
Glib::ustring str ; Glib::ustring::size_type index = output.find("FS bytes used");
if ( ! ( str = Utils::regexp_label( output, "FS bytes used ([0-9\\.]+( ?[KMGTPE]?i?B)?)" ) ) .empty() ) if (index < output.length())
total_fs_used = Utils::round( btrfs_size_to_gdouble( str ) ) ; sscanf(output.substr(index).c_str(), "FS bytes used %lld", &total_fs_used);
Glib::ustring::size_type offset = 0 ; Glib::ustring::size_type offset = 0 ;
Glib::ustring::size_type index ;
while ( ( index = output .find( "devid ", offset ) ) != Glib::ustring::npos ) while ( ( index = output .find( "devid ", offset ) ) != Glib::ustring::npos )
{ {
Glib::ustring devid_path = Utils::regexp_label( output .substr( index ), Glib::ustring devid_path = Utils::regexp_label( output .substr( index ),
"devid .* path (/dev/[[:graph:]]+)" ) ; "devid .* path (/dev/[[:graph:]]+)" ) ;
if ( ! devid_path .empty() ) if ( ! devid_path .empty() )
{ {
//Btrfs per devid used bytes (chunks) // Btrfs per devid used bytes (chunks)
Byte_Value used = -1 ; long long used = -1;
if ( ! ( str = Utils::regexp_label( output .substr( index ), sscanf(output.substr(index).c_str(), "devid %*d size %*d used %lld path", &used);
"devid .* used ([0-9\\.]+( ?[KMGTPE]?i?B)?) path" ) ) .empty() ) if (used > -1)
{ {
used = btrfs_size_to_num( str, ptn_size, false ) ;
sum_devid_used += used ; sum_devid_used += used ;
if ( devid_path == partition .get_path() ) if ( devid_path == partition .get_path() )
devid_used = used ; devid_used = used ;
} }
if ( devid_path == partition .get_path() ) if ( devid_path == partition .get_path() )
{ // Btrfs per device size bytes (chunks)
//Btrfs per device size bytes (chunks) sscanf(output.substr(index).c_str(), "devid %*d size %lld used", &devid_size);
if ( ! ( str = Utils::regexp_label( output .substr( index ),
"devid .* size ([0-9\\.]+( ?[KMGTPE]?i?B)?) used " ) ) .empty() )
devid_size = btrfs_size_to_num( str, ptn_size, true ) ;
}
} }
offset = index + 5 ; //Next find starts immediately after current "devid" offset = index + 5 ; //Next find starts immediately after current "devid"
} }
@ -482,94 +478,5 @@ const BTRFS_Device & btrfs::get_cache_entry( const Glib::ustring & path )
return btrfs_dev ; return btrfs_dev ;
} }
//Return the value of a btrfs tool formatted size, including reversing
// changes in certain cases caused by using binary prefix multipliers
// and rounding to two decimal places of precision. E.g. "2.00GB".
Byte_Value btrfs::btrfs_size_to_num( Glib::ustring str, Byte_Value ptn_bytes, bool scale_up )
{
Byte_Value size_bytes = Utils::round( btrfs_size_to_gdouble( str ) ) ;
gdouble delta = btrfs_size_max_delta( str ) ;
Byte_Value upper_size = size_bytes + ceil( delta ) ;
Byte_Value lower_size = size_bytes - floor( delta ) ;
if ( size_bytes > ptn_bytes && lower_size <= ptn_bytes )
{
//Scale value down to partition size:
// The btrfs tool reported size appears larger than the partition
// size, but the minimum possible size which could have been rounded
// to the reported figure is within the partition size so use the
// smaller partition size instead. Applied to FS device size and FS
// wide used bytes.
// ............| ptn_bytes
// [ x ) size_bytes with upper & lower size
// x scaled down size_bytes
// Do this to avoid the FS size or used bytes being larger than the
// partition size and GParted failing to read the file system usage and
// report a warning.
size_bytes = ptn_bytes ;
}
else if ( scale_up && size_bytes < ptn_bytes && upper_size > ptn_bytes )
{
//Scale value up to partition size:
// The btrfs tool reported size appears smaller than the partition
// size, but the maximum possible size which could have been rounded
// to the reported figure is within the partition size so use the
// larger partition size instead. Applied to FS device size only.
// ............| ptn_bytes
// [ x ) size_bytes with upper & lower size
// x scaled up size_bytes
// Make an assumption that the file system actually fills the
// partition, rather than is slightly smaller to avoid false reporting
// of unallocated space.
size_bytes = ptn_bytes ;
}
return size_bytes ;
}
//Return maximum delta for which num +/- delta would be rounded by btrfs
// tools to str. E.g. btrfs_size_max_delta("2.00GB") -> 5368709.12
gdouble btrfs::btrfs_size_max_delta( Glib::ustring str )
{
Glib::ustring limit_str ;
//Create limit_str. E.g. str = "2.00GB" -> limit_str = "0.005GB"
for ( Glib::ustring::iterator p = str .begin() ; p != str .end() ; p ++ )
{
if ( isdigit( *p ) )
limit_str .append( "0" ) ;
else if ( *p == '.' )
limit_str .append( "." ) ;
else
{
limit_str .append( "5" ) ;
limit_str .append( p, str .end() ) ;
break ;
}
}
gdouble max_delta = btrfs_size_to_gdouble( limit_str ) ;
return max_delta ;
}
//Return the value of a btrfs tool formatted size.
// E.g. btrfs_size_to_gdouble("2.00GB") -> 2147483648.0
gdouble btrfs::btrfs_size_to_gdouble( Glib::ustring str )
{
gchar * suffix ;
gdouble rawN = g_ascii_strtod( str .c_str(), & suffix ) ;
while ( isspace( suffix[0] ) ) //Skip white space before suffix
suffix ++ ;
unsigned long long mult ;
switch ( suffix[0] )
{
case 'K': mult = KIBIBYTE ; break ;
case 'M': mult = MEBIBYTE ; break ;
case 'G': mult = GIBIBYTE ; break ;
case 'T': mult = TEBIBYTE ; break ;
case 'P': mult = PEBIBYTE ; break ;
case 'E': mult = EXBIBYTE ; break ;
default: mult = 1 ; break ;
}
return rawN * mult ;
}
} //GParted } //GParted