On Mon, Jun 28, 2021 at 06:47:58PM +0100, Christoph Hellwig wrote:

On Mon, Jun 28, 2021 at 06:39:09PM +0100, Matthew Wilcox wrote:

quoted

Not hugely happy with either of these options, tbh.  I'd rather we apply
a patch akin to this one (plucked from the folio tree), so won't apply:

quoted

so permit pages without an iop to enter writeback and create an iop
*then*.  Would that solve your problem?

It is the right thing to do, especially when combined with a feature
patch to not bother to create the iomap_page structure on small
block size file systems when the extent covers the whole page.

We don't know the extent layout at the point where *this* patch creates
iomap_pages during writeback.  I imagine we can delay creating one until
we find out what our destination layout will be?