Interesting issues with strict allocate and large files ...

[Richard Sharpe]

Hi,

I recently came across an interesting problem with strict allocate and
large files ...

Customer was copying a large file (more than 4GB) to a Samba-based server.
The first thing the client does is a TRANS2 SET_FILE_INFO SET_END_OF_FILE
setting it to whatever the size is (6BG in this case). The smbd then
starts writing 6GB of zeros.

After 37 seconds, the client sends a HELLO.

After another 37 seconds the client drops the connection when it hasn't
heard back.

Thus, the copy fails because of strict allocate.

It would seem that there is basically no way around this, since the smbd
is deep in the VFS writing zeros ...

I am investigating what the issues are with turning off strict allocate,
but they likely involve losing info about when space is exhausted on a
drive/volume.

Windows responds withing about half a second to the SET_END_OF_FILE
request, even for 6GB. It might be that Windows maintains an in-core count
of the space reservations made on the drive, or perhaps it actually does
allocate all that space for the file.

Regards
-----
Richard Sharpe, rsharpe[at]richardsharpe.com, rsharpe[at]samba.org,
sharpe[at]ethereal.com, http://www.richardsharpe.com