Mysterious block count (reproducible)

[Bernd Walter]

On Fri, Feb 02, 2007 at 09:05:48PM +0100, Oliver Fromme wrote:
> Hi
> 
> The following is on a standard UFS2 file system under
> FreeBSD 6.2, block size 16 KB, fragsize 2 KB.  The
> filesystems are perfectly ok and fsck-clean.  There
> haven't been any physical disk errors either.
> 
> I've got a file on my home partition that's 214848 bytes.
> According to math it should occupy 14 blocks.  However:
> 
> $ BLOCKSIZE=16K ls -s foo
>  15 foo
> 
> I copied the file to /tmp (which is an mdfs, also UFS2
> with default parameters).  Same result.  I created a
> fresh file from /dev/zero of 214848 bytes.  The same.
> 
> Where does the 15th block come from?  Those additional
> 16 KB must be used for _something_ somewhere ...
> 
> fsdb(8) isn't helpful either:
> 
>    # fsdb -r /dev/md0
>    fsdb (inum: 2)> ls
>    [...]
>    slot 7 ino 5 reclen 20: regular, `foo'
>    fsdb (inum: 2)> inode 5
>    current inode: regular file
>    I=5 MODE=100600 SIZE=214848
>            BTIME=Feb  2 20:46:02 2007 [0 nsec]
>            MTIME=Feb  2 20:46:02 2007 [0 nsec]
>            CTIME=Feb  2 20:46:02 2007 [0 nsec]
>            ATIME=Feb  2 20:46:58 2007 [0 nsec]
>    OWNER=root GRP=wheel LINKCNT=1 FLAGS=0 BLKCNT=1e0 GEN=ffffffffe2ca5220
> 
> 0x1e0 is 224 (== 14 * 16).  So fsdb(8) doesn't see the
> 15th block either.  To confirm:
> 
>    fsdb (inum: 5)> blocks
>    Blocks for inode 5:
>    Direct blocks:
>    2136, 2144, 2152, 2160, 2168, 2176, 2184, 2192, 2248, 2256, 2264, 2272
>    Indirect blocks:
>    2280, 2288,
>    fsdb (inum: 5)> 
> 
> It lists 12 direct blocks and 2 indirect blocks, that's
> still 14 blocks, not 15.
> 
> Where did the 15th block go?!?  Or is there a bug in
> the calculation of ls -s output?

Don't forget the block needed for the indirect table.
fsdb only shows data blocks it seems.

-- 
B.Walter                http://www.bwct.de      http://www.fizon.de
bernd at bwct.de           info at bwct.de            support at fizon.de