Re: [Netatalk-devel] About symlinks

[didier <dga...@ma...>]

Hi,
Le vendredi 19 février 2010 à 14:01 +0100, Frank Lahm a écrit :
> 2010/2/19 didier <dga...@ma...>:
> > Hi,
> > Le mardi 05 janvier 2010 à 08:34 +0100, Anton Starikov a écrit :
> >
> >> > Locking could be an issue too, for symlink ad_open set adf_fd to 0 but
> >> > it's /dev/null. Need to double check all use of adf_fd for a 'closed' 0
> >> > file descriptor.
> >>
> >> Agree. Will check it. I've been thinking what to put in adf_fd. Probably INT_MIN can be a way, but then it must be checked that negative adf_fd will not introduce some problems later.
> > It's a problem with two clients and deleting symlinks.
> > first client delete a a symlink:
> > afpd call fcntl64(0, F_SETLK64, {type=F_WRLCK, whence=SEEK_SET, start=0,
> > len=0},...
> >
> > But it never releases the lock, it's done by the OS in close syscall.
> >
> > Of course afpd never close 0 but 0 is /dev/null, which is shared between
> > afpd processes.
> >
> > After that a second afpd get a BUSY error every time it tries to remove
> > a symlink.
> >
> > I'm adding a test428 showing the pb.
> 
> Good catch!
> 
> The attached patch fixes it for me. It adds checks for fd == 0 in
> ad_lock. I haven't committed it yet so that you can review it.
I'm afraid it's not enough, if there's no resource fork afpd takes locks
on the data fork.
I'll commit a wrapper around fcntl which does nothing for fd == 0.

There's also pb with:
- fstat(), we don't want to fstat(0,...), we have at least one case in
getforkparams.

- utime(), no lutimes syscall.

- and a couple of others :(


Didier