Re: [PATCH 13/18] fs: split locking of inode writeback and LRU lists

Christoph Hellwig
2010-10-08T08:18:19Z

On Fri, Oct 08, 2010 at 07:00:18PM +1100, Dave Chinner wrote:
> > >
> > > - if (inode->i_state & (I_NEW | I_WILL_FREE)) {
> > > + if (inode->i_state & (I_NEW | I_WILL_FREE | I_FREEING)) {
> > > requeue_io(inode);
> > > continue;
> > > }
> >
> > What does this have to do with the rest of the patch?
>
> That's because there's now a window between setting I_FREEING and taking
> the inode off the writeback list which means that we can see inodes
> in that state here. Generally it means that the code setting
> I_FREEING is spinning waiting for the wb->b_lock that this thread
> currently holds so it can be removed from the list.. Hence the requeue
> to move the inode out of the way and keep processing inodes for
> writeback.

That needs some documentation both in the changelog and in the code
I think.