Subject: df -h should use human_round_to_nearest in human_output_opts for more accurate results
From: Sabuj Pattanayek <[email-masked]>
To: [email-masked]
Date: Thu, 11 Aug 2011 00:54:00 -0500
List-Id: <debbugs-submit.debbugs.gnu.org>

Hi,

We have a 37TB filesystem that shows up in the output of df -h as 38TB :

Filesystem            Size  Used Avail Use% Mounted on
blue:/sas2fs03/        38T   24T   14T  63% /blue/sas2

df -k shows :

Filesystem           1K-blocks      Used Available Use% Mounted on
blue:/sas2fs03/      39741816832 25020650784 14721166048  63% /blue/sas2

39741816832 is definitely much closer to 37TB than to 38TB :

% echo "39741816832 / (1024^3)" | bc -l
37.01245117187500000000

38TB would be :

 echo "38*1024^3" | bc -l
40802189312 (in 1K-blocks) which is >> 39741816832 (difference of 1060372480)

With my suggested patch (below), I get correct output :

coreutils-8.9/src% ./df -h /blue/sas2
Filesystem            Size  Used Avail Use% Mounted on
blue:/sas2fs03/        37T   23T   14T  63% /blue/sas2

Here's my suggested patch against the 8.9 release :

--- df.c.old	2011-08-11 00:45:02.697289000 -0500
+++ df.c	2011-08-11 00:45:45.884017000 -0500
@@ -794,7 +794,7 @@
           inode_format = true;
           break;
         case 'h':
-          human_output_opts = human_autoscale | human_SI | human_base_1024;
+          human_output_opts = human_round_to_nearest |
human_autoscale | human_SI | human_base_1024;
           output_block_size = 1;
           break;
         case 'H':

Thanks,
Sabuj Pattanayek