Re: [ISSUE] split_folio() and dirty IOMAP folios

[Matthew Wilcox <willy@infradead.org>]

On Thu, Nov 07, 2024 at 04:07:08PM +0100, David Hildenbrand wrote:
> I'm debugging an interesting problem: split_folio() will fail on dirty
> folios on XFS, and I am not sure who will trigger the writeback in a timely
> manner so code relying on the split to work at some point (in sane setups
> where page pinning is not applicable) can make progress.

You could call something like filemap_write_and_wait_range()?

> ... or is there a feasible way forward to make iomap_release_folio() not
> bail out on dirty folios?
> 
> The comment there says:
> 
> "If the folio is dirty, we refuse to release our metadata because it may be
> partially dirty.  Once we track per-block dirty state, we can release the
> metadata if every block is dirty."

With the data structures and callbacks we have, it's hard to do.
Let's see if getting writeback kicked off will be enough to solve the
problem you're working on.