ceph: use osd_req_op_extent_osd_iter for netfs reads

The netfs layer has already pinned the pages involved before calling
issue_op, so we can just pass down the iter directly instead of calling
iov_iter_get_pages_alloc.

Instead of having to allocate a page array, use CEPH_MSG_DATA_ITER and
pass it the iov_iter directly to clone.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Xiubo Li <xiubli@redhat.com>
Reviewed-and-tested-by: Luís Henriques <lhenriques@suse.de>
Reviewed-by: Milind Changire <mchangir@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

fs/ceph/addr.c

@@ -246,7 +246,6 @@ static void finish_netfs_read(struct ceph_osd_request *req)
 	struct ceph_osd_data *osd_data = osd_req_op_extent_osd_data(req, 0);
 	struct netfs_io_subrequest *subreq = req->r_priv;
 	struct ceph_osd_req_op *op = &req->r_ops[0];
-	int num_pages;
 	int err = req->r_result;
 	bool sparse = (op->op == CEPH_OSD_OP_SPARSE_READ);
 
@@ -268,9 +267,6 @@ static void finish_netfs_read(struct ceph_osd_request *req)
 		__set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
 
 	netfs_subreq_terminated(subreq, err, false);
-
-	num_pages = calc_pages_for(osd_data->alignment, osd_data->length);
-	ceph_put_page_vector(osd_data->pages, num_pages, false);
 	iput(req->r_inode);
 }
 
@@ -338,8 +334,6 @@ static void ceph_netfs_issue_read(struct netfs_io_subrequest *subreq)
 	struct ceph_osd_request *req = NULL;
 	struct ceph_vino vino = ceph_vino(inode);
 	struct iov_iter iter;
-	struct page **pages;
-	size_t page_off;
 	int err = 0;
 	u64 len = subreq->len;
 	bool sparse = ceph_test_mount_opt(fsc, SPARSEREAD);
@@ -370,18 +364,7 @@ static void ceph_netfs_issue_read(struct netfs_io_subrequest *subreq)
 
 	dout("%s: pos=%llu orig_len=%zu len=%llu\n", __func__, subreq->start, subreq->len, len);
 	iov_iter_xarray(&iter, ITER_DEST, &rreq->mapping->i_pages, subreq->start, len);
-	err = iov_iter_get_pages_alloc2(&iter, &pages, len, &page_off);
-	if (err < 0) {
-		dout("%s: iov_ter_get_pages_alloc returned %d\n", __func__, err);
-		goto out;
-	}
-
-	/* should always give us a page-aligned read */
-	WARN_ON_ONCE(page_off);
-	len = err;
-	err = 0;
-
-	osd_req_op_extent_osd_data_pages(req, 0, pages, len, 0, false, false);
+	osd_req_op_extent_osd_iter(req, 0, &iter);
 	req->r_callback = finish_netfs_read;
 	req->r_priv = subreq;
 	req->r_inode = inode;