[PATCH v7 02/13] iov_iter: add iterator type for dmabuf maps

[Christoph Hellwig]

On Mon, Sep 28, 2026 at 02:32:18PM +0100, Pavel Begunkov wrote:
> Introduce a new iterator type for dmabuf maps. The map in an opaque
> object with internals and format specific to the subsystem / driver, and
> only it can use that subsystem / driver for issuing IO. The task of the
> middle layers is to pass the map / iterator further down, maybe doing
> basic splitting and length checking. The iterator can only be used by
> operations of the file the associated map was created for.
> 
> Suggested-by: Keith Busch <kbusch at kernel.org>
> Reviewed-by: Christoph Hellwig <hch at lst.de>
> Signed-off-by: Pavel Begunkov <asml.silence at gmail.com>

FYI, I think the Sashiko complaint about iterate_and_advance2
is correct here.  We don't really hit that in the series, but leaving
iov_iter methods partially implemented and fall through to others
seems dangerous.  At minimum that needs a WARN_ON to catch that case.