Re: [PATCH RFC 02/29] iomap: introduce iomap_read/write_region interface

Andrey Albershteyn
2025-09-12T11:56:51Z

On 2025-09-12 09:18:59, Christoph Hellwig wrote:
> On Tue, Sep 09, 2025 at 02:30:14PM +0200, Andrey Albershteyn wrote:
> > > Same thoughts here. It seems like we should just have a beyond-EOF or
> > > fsverity flag for ->read_iter / ->write_iter and consolidate all this
> > > code. That'll also go along nicely with the flag in the writepage_ctx
> > > suggested by Joanne.
> > >
> >
> > In addition to being bound by the isize the fiemap_read() copies
> > data to the iov_iter, which is not really needed for fsverity.
>
> Aka, you want an O_DIRECT read into a ITER_BVEC buffer for the data?
>

hmm, but we want fsverity merkle tree to be in page cache to use the
"verified page" flag. As far as I understand iter_bvec will need a
page attached anyway, so this is the same. Or am I missing
something?

And with direct io there's no readahead then, and we don't get any
benefit going through vfs instead of directly calling to iomap.

--
- Andrey