Bug#190732: [PATCH] hurd/libdiskfs/dir-renamed.c

[Ognyan Kulev]

Marco Gerards wrote:
> Ognyan Kulev <ogi@fmi.uni-sofia.bg> writes:
> > $ mkdir d
> > $ cd d
> > $ mkdir x
> > $ mv x y
> > $ mv y x
>
> I've tested this both with and without your patch. Nothing (weird)
> happened.

(I suppose you are talking about your patch, not about mine.)  I tried 
your patch and, suprisingly for me, the assertion failure in 
ext2fs/dir.c:716 didn't trigger.  Anyway, by protocol[1] (diskfs.h:313), 
two diskfs_lookup in the same directory must have diskfs_drop_dirstat or 
diskfs_dir* between them.

[1] http://mail.gnu.org/archive/html/bug-hurd/2003-07/msg00092.html

BTW There is a possible deadlock in this function when source and 
destination parent directories are different.  Let's name them A and B. 
 Moving A/x to B/x first locks A.  If in this moment another thread 
moves B/y to A/y, then it locks B and tries to lock A and then sleeps 
waiting A to be unlocked.  The first thread continues by trying to lock 
B, but it's already locked.  I'll try to address this and other problems 
(like reverting back st_nlink when error occurs) in a "final" patch soon.

Regards
--
Ognyan Kulev <ogi@{fmi.uni-sofia.bg,fsa-bg.org}>
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