libceph: add new iov_iter-based ceph_msg_data_type and ceph_osd_data_type

Add an iov_iter to the unions in ceph_msg_data and ceph_msg_data_cursor.
Instead of requiring a list of pages or bvecs, we can just use an
iov_iter directly, and avoid extra allocations.

We assume that the pages represented by the iter are pinned such that
they shouldn't incur page faults, which is the case for the iov_iters
created by netfs.

While working on this, Al Viro informed me that he was going to change
iov_iter_get_pages to auto-advance the iterator as that pattern is more
or less required for ITER_PIPE anyway. We emulate that here for now by
advancing in the _next op and tracking that amount in the "lastlen"
field.

In the event that _next is called twice without an intervening
_advance, we revert the iov_iter by the remaining lastlen before
calling iov_iter_get_pages.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: David Howells <dhowells@redhat.com>
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>

1 files changed, 27 insertions, 0 deletions

diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
index 0aacbadcab06..684faf8553de 100644
--- a/net/ceph/osd_client.c
+++ b/net/ceph/osd_client.c
@@ -171,6 +171,13 @@ static void ceph_osd_data_bvecs_init(struct ceph_osd_data *osd_data,
 	osd_data->num_bvecs = num_bvecs;
 }
 
+static void ceph_osd_iter_init(struct ceph_osd_data *osd_data,
+			       struct iov_iter *iter)
+{
+	osd_data->type = CEPH_OSD_DATA_TYPE_ITER;
+	osd_data->iter = *iter;
+}
+
 static struct ceph_osd_data *
 osd_req_op_raw_data_in(struct ceph_osd_request *osd_req, unsigned int which)
 {
@@ -264,6 +271,22 @@ void osd_req_op_extent_osd_data_bvec_pos(struct ceph_osd_request *osd_req,
 }
 EXPORT_SYMBOL(osd_req_op_extent_osd_data_bvec_pos);
 
+/**
+ * osd_req_op_extent_osd_iter - Set up an operation with an iterator buffer
+ * @osd_req: The request to set up
+ * @which: Index of the operation in which to set the iter
+ * @iter: The buffer iterator
+ */
+void osd_req_op_extent_osd_iter(struct ceph_osd_request *osd_req,
+				unsigned int which, struct iov_iter *iter)
+{
+	struct ceph_osd_data *osd_data;
+
+	osd_data = osd_req_op_data(osd_req, which, extent, osd_data);
+	ceph_osd_iter_init(osd_data, iter);
+}
+EXPORT_SYMBOL(osd_req_op_extent_osd_iter);
+
 static void osd_req_op_cls_request_info_pagelist(
 			struct ceph_osd_request *osd_req,
 			unsigned int which, struct ceph_pagelist *pagelist)
@@ -346,6 +369,8 @@ static u64 ceph_osd_data_length(struct ceph_osd_data *osd_data)
 #endif /* CONFIG_BLOCK */
 	case CEPH_OSD_DATA_TYPE_BVECS:
 		return osd_data->bvec_pos.iter.bi_size;
+	case CEPH_OSD_DATA_TYPE_ITER:
+		return iov_iter_count(&osd_data->iter);
 	default:
 		WARN(true, "unrecognized data type %d\n", (int)osd_data->type);
 		return 0;
@@ -954,6 +979,8 @@ static void ceph_osdc_msg_data_add(struct ceph_msg *msg,
 #endif
 	} else if (osd_data->type == CEPH_OSD_DATA_TYPE_BVECS) {
 		ceph_msg_data_add_bvecs(msg, &osd_data->bvec_pos);
+	} else if (osd_data->type == CEPH_OSD_DATA_TYPE_ITER) {
+		ceph_msg_data_add_iter(msg, &osd_data->iter);
 	} else {
 		BUG_ON(osd_data->type != CEPH_OSD_DATA_TYPE_NONE);
 	}