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

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