Re: /usr/bin/df reports false size on big NFS shares

[Andreas Dilger <adilger@clusterfs.com>]

On Jun 10, 2002  16:54 +0200, Samuel Maftoul wrote:
> On several machines, with kernel 2.4.18 the same mounts reports different
> sizes than with 2.4.4 :
> 
> -------------------------------------------------------------------------
> maftoul@brick20:~ > uname  -a 
> Linux brick20 2.4.4-4GB #6 Thu Jul 26 10:00:30 CEST 2001 i686 unknown
> 
> maftoul@brick20:~ > df -h 
> Filesystem            Size  Used Avail Use% Mounted on
> /dev/sda1              13G  3.1G  9.5G  25% /
> shmfs                 517M     0  516M   0% /dev/shm
> grey:/disk91          230G  127G  102G  56% /mntdirect/_disk91
> yellow:/disk23        140G  100G   39G  72% /mntdirect/_disk23
> violet:/data/id19/external
>                       2.7T  1.1T  1.6T  38% /mntdirect/_data_id19_external
> maftoul@brick20:~ >
> -------------------------------------------------------------------------
> 
> maftoul@brick4:~ > uname  -a 
> Linux brick4 2.4.18 #3 Thu Apr 4 17:04:20 CEST 2002 i686 unknown
> maftoul@brick4:~ > 
> 
> maftoul@brick4:~ > df -h 
> Filesystem            Size  Used Avail Use% Mounted on
> /dev/sda1             4.7G  2.7G  2.0G  58% /
> shmfs                 125M     0  124M   0% /dev/shm
> grey:/disk91          230G  127G  102G  56% /mntdirect/_disk91
> yellow:/disk23        140G  100G   39G  72% /mntdirect/_disk23
> violet:/data/id19/external
>                       669G -7.0Z  1.6T 101% /mntdirect/_data_id19_external
> -------------------------------------------------------------------------
> 
> See the violet one ?
> The reported size is the same on every 2.4.18 machine using this mount I
> saw.

Probably an overflow in the math somewhere.  Since the overflow is in
the zettabyte range, it is probably someone not being careful with
64-bit values overflowing.  "64-bit values are large enough for
everything, right..."

> It's all suse 7.2 , first one (2.4.4) is suse 7.2 base kernel, 2.4.18 is
> our own (for firewire better firewire support).

Probably the best thing you can do is either diff the two kernel sources
looking for changes in fs/nfs, or start with 2.4.4 and apply patches
until you get a failure.

I don't think a lot of people will be able to help you test this, as
they don't have 2.7TB NFS servers available ;-).

Cheers, Andreas

FYI: In case anyone is wondering (I was) a "Z" is a Zettabyte (2^70 bytes).
     It falls between Exabyte (1024 PB = 2^60) and Yottabyte (2^80).
--
Andreas Dilger
http://www-mddsp.enel.ucalgary.ca/People/adilger/
http://sourceforge.net/projects/ext2resize/