[AVFS] Problems with fork, Questions about avfs

Hi,

I have several questions regarding avfs and I hope to find some answers 
here. I want to use AVFS for my filemanager 
(www.boomerangsworld.de/worker). I already tried to use the VFS from MC 
but as it is not thread safe it is not an option. There are some other 
VFS but I think avfs is the system which best fits my needs.
I recently checked out the avfs CVS code and found the shared library. I 
already use it and it works fine so far. However, I have a few questions 
and hints.
First of all I miss some functions. I don't know if the avfs project 
want to implement the fopen/fread/fclose... function class but this is 
not a real problem. But there is no virt_remove function. I know it is 
only a wrapper for unlink/rmdir but according to the man-page the remove 
function is mentioned in ANSI C, POSIX and other standards so it is 
perhaps a good idea to implement it.

A real problem is the init()/destroy() stuff. AVFS is thread safe but 
not fork safe. In the MC VFS code there are the functions vfs_init and 
vfs_shut which need to be called by the programmer. AVFS takes care of 
this itself which is a good thing but it cause problems when forking. If 
a forked child quits, the destroy function is called which will delete 
the temporary directory (/tmp/.avfs...) The original process thinks this 
directory still exists and the VFS does not work properly anymore. I 
workaround this problem for my filemanager by using _exit for the forked 
childs but I think there should be a possibility to prevent the destroy 
call (for example explicitly remove destroy from atexit list or use a 
lock file in the avfs temp dir for some kind of reference counting). 
BTW, can avfs handle shared tmp files between forked processes at all? A 
solution could be the usage of pthread_atfork to recreate temporary 
files for the child.

Then there is serious problem with the character # inside filenames. I'm 
aware that filenames containing for example #utar cannot be accessed but 
atleast files with a # and other following characters not matching any 
vfs extensions should be accessible. For example for a directory 
containing a file "test#test" readdir will return "test##test" but lstat 
on this name fails.

The directory /#avfsstat/cache has the inode 0 but inode 0 & 1 should 
not be used (if 
"http://www.gsp.com/cgi-bin/man.cgi?section=5&topic=inode" is true for 
all filesystems).

A function "isLocal()" would really help me as I use the filecontent for
filetype recognition and it is not always a good idea to read the files 
in virtual directories (slow ftp or ssh). This way I can skip such files.

The last release is 3 years old and I don't know about bugfixes. But is 
there any reason I should not use AVFS for my filemanager? Do you mind 
if I use the latest CVS code and put it on my homepage so the user can 
use this?

I can implement some of the changes myself so if you accept patches I 
will send them to the list.

After all the criticism let me say that I think avfs is a great virtual
filesystem especially since it is very easy to add to a program which 
uses normal file operations.

Best Regards,

Ralf Hoffmann

-- 
Homepage: http://www.boomerangsworld.de
E-Mail: Ralf Hoffmann <[email protected]>
   english or german


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