no fsck for unmounted filesystems

[Reindl Harald]

/dev/sda1 is a ordinary partition containing only /boot
why does the kernel report it is in use?
if that would be true it could not be unmounted
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[root at asterisk:~]$ /usr/sbin/fsck.ext4 -f /dev/sda1
e2fsck 1.42.12 (29-Aug-2014)
/dev/sda1 is in use.
e2fsck: Cannot continue, aborting.
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[root at asterisk:~]$ lsof | grep /dev/sda1
[root at asterisk:~]$
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[root at asterisk:~]$ /usr/sbin/fsck.ext4 -n /dev/sda1
e2fsck 1.42.12 (29-Aug-2014)
Warning!  /dev/sda1 is in use.
boot was not cleanly unmounted, check forced.
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
Free blocks count wrong (454751, counted=469570).
Fix? no

Free inodes count wrong (130215, counted=130220).
Fix? no

boot: 345/130560 files (22.6% non-contiguous), 66464/521215 blocks