[Cluster-devel] [PATCH 16/27] iomap: switch iomap_bmap to use iomap_iter

[Christoph Hellwig]

On Mon, Jul 26, 2021 at 09:39:22AM -0700, Darrick J. Wong wrote:
> The documentation needs to be much more explicit about the fact that you
> cannot "break;" your way out of an iomap_iter loop.  I think the comment
> should be rewritten along these lines:
> 
> "Iterate over filesystem-provided space mappings for the provided file
> range.  This function handles cleanup of resources acquired for
> iteration when the filesystem indicates there are no more space
> mappings, which means that this function must be called in a loop that
> continues as long it returns a positive value.  If 0 or a negative value
> is returned, the caller must not return to the loop body.  Within a loop
> body, there are two ways to break out of the loop body: leave
> @iter.processed unchanged, or set it to the usual negative errno."
> 
> Hm.

Yes, I'll update the documentation.

> Clunky, for sure, but at least we still get to use break as the language
> designers intended.

I can't see any advantage there over just proper documentation.  If you
are totally attached to a working break we might have to come up with
a nasty for_each macro that ensures we have a final iomap_apply, but I
doubt it is worth the effort.