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

Darrick J. Wong djwong at kernel.org
Tue Jul 27 14:32:56 UTC 2021

On Tue, Jul 27, 2021 at 08:31:38AM +0200, Christoph Hellwig wrote:
> 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.

Ok, thanks!

> > 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.

I was pushing the explicit _break() function as a means to avoid an even
fuglier loop macro.


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