Re: [PATCH] iomap: follow the alignment requirement for iomap_dio_hole_iter()

On Thu, Jul 30, 2026 at 06:06:17PM +0930, Qu Wenruo wrote:
> > iomap generall expects extents to be block aligned, how do you end up
> > with non-aligned reporting here?
> 
> The dio read buffer is 2 pages (matching the 8K alignment), but only the
> first page is faulted in.
> 
> Furthermore btrfs has disabled page fault during dio read, so the 2nd page
> will not be faulted in.
> 
> Thus iov_iter_zero() only got to zero the first page.
> 
> Btrfs always returned a hole that is properly aligned, but as long as bs >
> ps, the page fault can always break in the middle, causing unaligned range.

Urgg, we really need to get rid of this nofault behavior rather sooner
than later.  But I think the iomap should always be fsblock alignment.
While we can support smaller I/O, the mapping should always be block
aligned.