Re: [PATCH 5/7] xfs: fill dirty folios on zero range of unwritten mappings

[Christoph Hellwig <hch@infradead.org>]

On Mon, Jun 09, 2025 at 09:12:19AM -0700, Darrick J. Wong wrote:
> > +	struct iomap_iter	*iter = container_of(iomap, struct iomap_iter,
> > +						     iomap);
> 
> /me has been wondering more and more if we should just pass the iter
> directly to iomap_begin rather than make them play these container_of
> tricks... OTOH I think the whole point of this:
> 
> 	ret = ops->iomap_begin(iter->inode, iter->pos, iter->len, iter->flags,
> 			       &iter->iomap, &iter->srcmap);
> 
> is to "avoid" allowing the iomap users to mess with the internals of the
> iomap iter...

No, the reason is that the ->iomap_begin interface predates
struct iomap_iter.  I delayed changing the prototype because I thought
I'd get to the second step of willy's iterization idea and kill these
methods in favor of a real iterator, but that just doesn't keep
happening.