[cvsnt] Re: NAV vs. CVSNT

Tony Hoyle tmh at nodomain.org
Fri Feb 28 15:49:45 GMT 2003


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On Fri, 28 Feb 2003 16:30:03 +0200, Ori Berger <cvsnt-newsgroups at orib.net>
wrote:


>Internally, to delete a file on NT, one has to do the following:
>1. Open the file with Delete permission
>2. Mark the file 'pending deletion'
>3. Close the file
>
Actually it's worse than that... step 3 breaks down to
3a. Request that the system closes the file
3b. System returns 'Done' then goes away and thinks about it
3c. File closed.

There is a few milliseconds between the file closing and it actually being
unlocked - this is an NT bug, but quite a subtle one (you normally won't hit
it unless you'd doing a lot of file I/O on a heavily loaded system such as
cvsnt).  Recent builds have been restructured to increase the delay slightly
between close and rename for this reason.

What some AV products do (NAV is one I think) is grab the request at 3b, then
go and virus scan it - unfortunately this takes a *lot* more than a few
milliseconds, so standard code which does:

create temp file.
write data to temp file
close temp file
rename temp file to real file

...Fails when these AV products are loaded.  I'm surprised this doesn't affect
more software than it does, because it's a *very* standard way to make
changes.

Since it's not a bug in cvsnt I'm not going to waste any more time on it...
I'm relying on standard behaviour from the system.  If the AV breaks that
behaviour that's not my problem.

Tony



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