I got "block bitmap differences" when doing e2fsck. I do e2fsck after i unmount that partition. My question is: what exactly is "bitmap difference". The difference is between what to what?
~ # e2fsck -c /dev/sda1 e2fsck 1.42.5 (29-Jul-2012) ext2fs_check_if_mount: Can't check if filesystem is mounted due to missing mtab file while determining whether /dev/sda1 is mounted. Checking for bad blocks (read-only test): done /dev/sda1: Updating bad block inode. Pass 1: Checking inodes, blocks, and sizes Inode 81738, i_blocks is 16, should be 8. Fix<y>? yes Pass 2: Checking directory structure Entry 'collector_prof.txt' in /etc/idirect (81624) has deleted/unused inode 81762. Clear<y>? yes Pass 3: Checking directory connectivity Pass 4: Checking reference counts Pass 5: Checking group summary information Block bitmap differences: -(346115--346116) Fix<y>? yes Free blocks count wrong for group #10 (32124, counted=32126). Fix<y>? yes Free blocks count wrong (435610, counted=435612). Fix<y>? yes Inode bitmap differences: -81762 Fix<y>? yes Free inodes count wrong for group #10 (7998, counted=7999). Fix<y>? yes Free inodes count wrong (121381, counted=121382). Fix<y>? yes /dev/sda1: ***** FILE SYSTEM WAS MODIFIED ***** /dev/sda1: 1018/122400 files (0.1% non-contiguous), 53599/489211 blocks