Re: [PATCH 14/18] fs: Protect inode->i_state with th einode->i_lock

Christoph Hellwig
2010-10-09T08:05:46Z

On Fri, Oct 08, 2010 at 07:04:28PM +1100, Dave Chinner wrote:
> > > inode->i_ino = ++last_ino;
> > > inode->i_state = 0;
> > > + __inode_add_to_lists(sb, NULL, inode);
> > > spin_unlock(&inode_lock);
> > > }
> > > return inode;
> >
> > What's the point in doing this move?
>
> hmmmm, let me think on that....
>
> >
> > > @@ -953,8 +966,8 @@ static struct inode *get_new_inode(struct super_block *sb,
> > > if (set(inode, data))
> > > goto set_failed;
> > >
> > > - __inode_add_to_lists(sb, b, inode);
> > > inode->i_state = I_NEW;
> > > + __inode_add_to_lists(sb, b, inode);
> >
> > Same here.
>
> Ah, done thinking now! I was so the i_state field had been set
> before the inode was added to various lists and potentially
> accessable to other threads. I should probably add a comment to that
> effect, right?

In addition to the comment get_new_inode_fast also needs the same
treatment. I also wonder if we need to set I_NEW in new_inode and
then later call unlock_new_inode on it. It's not on the hash at that
point, but it is on the per-sbi list which we use for a few things.
With current callers it seems safe, but the whole thing also is rather
fragile. Better left for another patch, though.