From eeea3ea6a88a8f1c7511abf0b429297a562e7d30 Mon Sep 17 00:00:00 2001
From: Peter Korsgaard <jacmet@sunsite.dk>
Date: Thu, 30 Dec 2010 23:10:21 +0100
Subject: genext2fs.sh: improve number of blocks calculation

Closes #2929

Instead of just adding a fixed amount to the blocks used, try to
estimate the real space needed according to the filesystem structure
(bitmaps, inodes, blocks).

The side effect of this is that we no longer significantly overestimate
the size needed for small file systems.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
---
 fs/ext2/genext2fs.sh | 25 +++++++++++--------------
 1 file changed, 11 insertions(+), 14 deletions(-)

(limited to 'fs')

diff --git a/fs/ext2/genext2fs.sh b/fs/ext2/genext2fs.sh
index b315ec30a..7a518aea7 100755
--- a/fs/ext2/genext2fs.sh
+++ b/fs/ext2/genext2fs.sh
@@ -10,24 +10,11 @@ while getopts x:d:D:b:i:N:m:g:e:zfqUPhVv f
 do
     case $f in
 	b) CALC_BLOCKS=0 ;;
-	N) CALC_INODES=0 ;;
+	N) CALC_INODES=0; INODES=$OPTARG ;;
 	d) TARGET_DIR=$OPTARG ;;
     esac
 done
 
-# calculate needed blocks
-if [ $CALC_BLOCKS -eq 1 ];
-then
-    BLOCKS=$(du -s -c -k $TARGET_DIR | grep total | sed -e "s/total//")
-    if [ $BLOCKS -ge 20000 ];
-    then
-	BLOCKS=$(expr $BLOCKS + 16384)
-    else
-	BLOCKS=$(expr $BLOCKS + 2400)
-    fi
-    set -- $@ -b $BLOCKS
-fi
-
 # calculate needed inodes
 if [ $CALC_INODES -eq 1 ];
 then
@@ -36,4 +23,14 @@ then
     set -- $@ -N $INODES
 fi
 
+# calculate needed blocks
+if [ $CALC_BLOCKS -eq 1 ];
+then
+    # size ~= superblock, block+inode bitmaps, inodes (8 per block), blocks
+    # we scale inodes / blocks with 10% to compensate for bitmaps size + slack
+    BLOCKS=$(du -s -c -k $TARGET_DIR | grep total | sed -e "s/total//")
+    BLOCKS=$(expr 500 + \( $BLOCKS + $INODES / 8 \) \* 11 / 10)
+    set -- $@ -b $BLOCKS
+fi
+
 exec genext2fs $@
-- 
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