[gparted/8-shrinking-an-ext4-partition-does-not-respect-resize2fs-limits] Work in FS blocks until later while reading EXT2/3/4 usage (#8)

[Mike Fleetwood <mfleetwo src gnome org>]

commit 469e99780120a3707d66312a3926ab997dc49d33
Author: Mike Fleetwood <mike fleetwood googlemail com>
Date:   Mon Jul 30 16:50:35 2018 +0100

    Work in FS blocks until later while reading EXT2/3/4 usage (#8)
    
    No functional change.  Just work in FS block sized units until as late
    as possible in ext2::set_used_sectors(), before converting to device
    sector size units.  This is to make the following change simpler and
    easier to understand.
    
    Closes #8 - Shrinking an EXT4 partition does not respect resize2fs
                limits

 src/ext2.cc | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)
---
diff --git a/src/ext2.cc b/src/ext2.cc
index 7bd191fb..a2f5e1ec 100644
--- a/src/ext2.cc
+++ b/src/ext2.cc
@@ -160,16 +160,15 @@ void ext2::set_used_sectors( Partition & partition )
                     sscanf( output.substr( index ).c_str(), "Block size: %lld", &S ) != 1 )
                        S = -1 ;
 
-               if ( T > -1 && S > -1 )
-                       T = Utils::round( T * ( S / double(partition .sector_size) ) ) ;
-
                if ( partition .busy )
                {
                        Byte_Value ignored ;
                        Byte_Value fs_free ;
                        if ( Utils::get_mounted_filesystem_usage( partition .get_mountpoint(),
                                                                  ignored, fs_free, error ) == 0 )
-                               N = Utils::round( fs_free / double(partition .sector_size) ) ;
+                       {
+                               N = fs_free / S;
+                       }
                        else
                        {
                                N = -1 ;
@@ -182,13 +181,13 @@ void ext2::set_used_sectors( Partition & partition )
                        if ( index >= output .length() ||
                             sscanf( output.substr( index ).c_str(), "Free blocks: %lld", &N ) != 1 )
                                N = -1 ;
-
-                       if ( N > -1 && S > -1 )
-                               N = Utils::round( N * ( S / double(partition .sector_size) ) ) ;
                }
 
                if ( T > -1 && N > -1 && S > -1 )
                {
+                       T = Utils::round( T * ( S / double(partition.sector_size) ) );
+                       N = Utils::round( N * ( S / double(partition.sector_size) ) );
+
                        partition .set_sector_usage( T, N ) ;
                        partition.fs_block_size = S;
                }