[Dazuko-devel] Dazuko on FreeBSD (no more open-file-list)

[John Ogness]

Hi,

I realized a couple days ago that the FreeBSD extension from Dazuko 
implements a work-around that was designed for Linux. The open-file 
lists have been causing lots of problems. Normally this list is not 
needed, but under Linux the necessary structures to do 
file_descriptor->file_name lookups are hidden from kernel modules. This 
is why Dazuko must track the file_names/file_descriptors as they are opened.

However, FreeBSD does not hide it's code from modules. So under FreeBSD, 
closing file_descriptors should be no problem to look up the 
corresponding file_names.

Well, I implemented this under FreeBSD 4 and it works beautifully 
(available in CVS). Right now it is only being used for the sys_close 
call. I will include this support to dup and dup2 shortly. Then I can 
copy it over to FreeBSD 5.

This is great news because it means no more memory leaks or 
unreliability with ON_CLOSE events (under FreeBSD). Linux could also do 
this if people were willing to compile Dazuko into the kernel (and not 
as a kernel module). I may make this an option since ON_CLOSE is a very 
important event and the memory leaks it causes are unbearable.

This implementation also means that there is no way to track writes 
(because I will eliminate the open-file-list). This means that 
ON_CLOSE_MODIFIED events will never be generated. I personally do not 
have a problem with this because the ON_CLOSE_MODIFIED events generate 
an enormous overhead for something that a userspace application can do 
itself easily (and much more effeciently).

John Ogness

--
Dazuko Maintainer