block: Use iov_iter_extract_pages() and page pinning in direct-io.c

Change the old block-based direct-I/O code to use iov_iter_extract_pages()
to pin user pages or leave kernel pages unpinned rather than taking refs
when submitting bios.

This makes use of the preceding patches to not take pins on the zero page
(thereby allowing insertion of zero pages in with pinned pages) and to get
additional pins on pages, allowing an extracted page to be used in multiple
bios without having to re-extract it.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Christoph Hellwig <hch@infradead.org>
cc: David Hildenbrand <david@redhat.com>
cc: Lorenzo Stoakes <lstoakes@gmail.com>
cc: Andrew Morton <akpm@linux-foundation.org>
cc: Jens Axboe <axboe@kernel.dk>
cc: Al Viro <viro@zeniv.linux.org.uk>
cc: Matthew Wilcox <willy@infradead.org>
cc: Jan Kara <jack@suse.cz>
cc: Jeff Layton <jlayton@kernel.org>
cc: Jason Gunthorpe <jgg@nvidia.com>
cc: Logan Gunthorpe <logang@deltatee.com>
cc: Hillf Danton <hdanton@sina.com>
cc: Christian Brauner <brauner@kernel.org>
cc: Linus Torvalds <torvalds@linux-foundation.org>
cc: linux-fsdevel@vger.kernel.org
cc: linux-block@vger.kernel.org
cc: linux-kernel@vger.kernel.org
cc: linux-mm@kvack.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230526214142.958751-4-dhowells@redhat.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>