Re: Linux 2.4.33-rc2

Willy Tarreau
2006-07-05T05:18:41Z

Hi Grant,

On Wed, Jul 05, 2006 at 11:51:35AM +1000, Grant Coady wrote:
> On Tue, 4 Jul 2006 00:07:36 +0200, Willy Tarreau <w@1wt.eu> wrote:
(...)
> >What I notice is that in 2.4.32, d_delete(dentry) was performed
> >between down(&dir->i_zombie) and up(&dir->i_zombie), while now
> >it's completely outside. I wonder if this can cause race conditions
> >or not, but at least, I'm sure that we have changed the locking
> >sequence, which might have some impact.
> >
> >Do you think I'm searching in the wrong direction ? I worry a
> >bit, because getting a deadlock after only one day, it's a bit
> >early :-/
> >
> Assuming you mean something like the patch below? Doesn't cause any
> problems (yet, still testing) like eat files or segfault here as
> reported for -rc1 +/- various patches ;)

yes, exactly this. I don't know if it's correct and/or needed. In 2.6,
the d_delete() is performed outside the lock. I'd like someone's advise
on this one. Also, I'll look for an NFS client stress test to try to
reproduce the problem, because I don't like it when problems like this
only appear once a day. And playing with the VFS does not make me happy
at all.

> Cheers,
> Grant.

Cheers,
Willy

> --- linux-2.4.33-rc2/fs/namei.c 2006-06-22 07:27:47.000000000 +1000
> +++ linux-2.4.33-rc2b/fs/namei.c 2006-07-05 11:43:19.000000000 +1000
> @@ -1497,13 +1497,14 @@
> lock_kernel();
> error = dir->i_op->unlink(dir, dentry);
> unlock_kernel();
> + if (!error)
> + d_delete(dentry);
> }
> }
> double_up(&dir->i_zombie, &inode->i_zombie);
> iput(inode);
>
> if (!error) {
> - d_delete(dentry);
> inode_dir_notify(dir, DN_DELETE);
> }
> return error;