[Cluster-devel] [RFC v3 2/7] iomap: Add iomap_folio_done helper

[Christoph Hellwig <hch@infradead.org>]

On Fri, Dec 23, 2022 at 09:54:34PM +0100, Andreas Gr?nbacher wrote:
> > But for the current version I don't really understand why the error
> > unwinding changes here.
> 
> Currently, we have this order of operations in iomap_write_begin():
> 
>   folio_unlock() // folio_put() // iomap_write_failed() // ->page_done()
> 
> and this order in iomap_write_end():
> 
>   folio_unlock() // ->page_done() // folio_put() // iomap_write_failed()
> 
> The unwinding in iomap_write_begin() works because this is the trivial
> case in which nothing happens to the page. We might just as well use
> the same order of operations there as in iomap_write_end() though, and
> when you switch to that, this is what you get.

Please document this in the commit message.