File ... shrunk by 3337 bytes, padding with zeroes

[Eric Buddington]

Hi - I don't know what to make of this error, and I suspect a problem with tar.

I was copying a directory tree with:
        tar -cf /packages/pcmcia-cs | tar -xvf -
And got the error:
        tar: File /packages/pcmcia-cs/3.1.26/any/share/pnp.ids shrunk by 3337 
bytes, padding with zeroes.
        tar: Error exit delayed from previous errors
And tar dies, without finishing.

diff /packages/pcmcia-cs/3.1.26/any/share/pnp.ids
packages/pcmcia-cs/3.1.26/any/share/pnp.ids is silent, so the copy
seems to have worked in reality (for that file).

The following commands work fine, copy the whole tree, and don't
complain:
        tar -czf /packages/pcmcia-cs | tar -xzvf -
        tar -czf /packages/pcmcia-cs | zcat | tar -xvf -

I suspected maybe a short read from the pipe confusing tar, but I
straced and saw no short reads.

I straced the receiving tar command in these two commands:
        tar -cf /packages/pcmcia-cs | tar -xvf -
        tar -czf /packages/pcmcia-cs | zcat | tar -xvf -

and found that the *second* one (getting imput from zcat, which
worked) sometimes got short blocks of 2k or 4k. I also confirmed that
tar's input from both of these is byte-identical (by redirecting to
files in stead of tar, and diff'ing).

I don't get it. What could be causing this error?

-Eric