Re: [PATCH 18/18] fs: Reduce inode I_FREEING and factor inode disposal

Matthew Wilcox
2010-10-09T17:22:46Z

On Fri, Oct 08, 2010 at 04:21:32PM +1100, Dave Chinner wrote:
> /*
> - * dispose_list - dispose of the contents of a local list
> - * @head: the head of the list to free
> + * Free the inode passed in, removing it from the lists it is still connected
> + * to but avoiding unnecessary lock round-trips for the lists it is no longer
> + * on.
> *
> - * Dispose-list gets a local list with local inodes in it, so it doesn't
> - * need to worry about list corruption and SMP locks.
> + * An inode must already be marked I_FREEING so that we avoid the inode being
> + * moved back onto lists if we race with other code that manipulates the lists
> + * (e.g. writeback_single_inode).
> */
> -static void dispose_list(struct list_head *head)
> +static void dispose_one_inode(struct inode *inode)
> {
> - while (!list_empty(head)) {
> - struct inode *inode;
> + BUG_ON(!(inode->i_state & I_FREEING));

I think this may be my favourite comment in this whole patch set. It's a
real pain to hit BUG_ONs and not know why it's there. Thank you.

--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."