Re: [PATCH v8 06/10] iomap: fix iomap_dio_zero() for fs bs > system page size

[Christoph Hellwig <hch@lst.de>]

On Tue, Jul 02, 2024 at 10:15:56AM +0000, Pankaj Raghav (Samsung) wrote:
> Willy suggested we could use raw pages as we don't need the metadata
> from using a folio. [0]

Ok, that feels weird but I'll defer to his opinion in that case.

> > > +	/*
> > > +	 * Max block size supported is 64k
> > > +	 */
> > > +	WARN_ON_ONCE(len > ZERO_PAGE_64K_SIZE);
> > 
> > 
> > A WARN_ON without actually erroring out here is highly dangerous. 
> 
> I agree but I think we decided that we are safe with 64k for now as fs 
> that uses iomap will not have a block size > 64k. 
> 
> But this function needs some changes when we decide to go beyond 64k
> by returning error instead of not returning anything. 
> Until then WARN_ON_ONCE would be a good stop gap for people developing
> the feature to go beyond 64k block size[1]. 

Sure, but please make it return an error and return that instead of
just warning and going beyond the allocated page.