Re: [PATCH v3 11/28] iomap: pass readpage operation to read path

[Christoph Hellwig <hch@infradead.org>]

On Mon, Oct 16, 2023 at 02:32:25PM +0200, Andrey Albershteyn wrote:
> >From the discussion in v2 [1] I understood that btrfs would like to
> have this bio_set/submit_io interface for iomap transition;

For btrfs it would not be a transitional thing, but forever as it has
it's own equivalent of a device mapper at this level.  But now that
the fsverity interfaces work so that we don't have other file system
dependencies I would not want to design around it.  If/when btrfs
migrates to iomap for the buffer read path we can easily hook this
into the existing code.

> and any
> other filesystem deferrals would also be possible. Is it no more the
> case with btrfs? Would fs-verity verification in iomap_read_end_io
> combine both solutions (fs-verity verification in iomap +
> submit_io/bio_set interface).

btrfs does also need to do I/O completion from a workqueue, but it
needs it's own.  fsverity OTOH is a pretty generic feature.