libceph: handle zero-length data items
rbd needs this for null copyups -- if copyup data is all zeroes, we
want to save some I/O and network bandwidth. See rbd_obj_issue_copyup()
in the next commit.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Alex Elder <elder@linaro.org>
diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index 91a5785..cee4b3d 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -1605,13 +1605,18 @@ static int write_partial_message_data(struct ceph_connection *con)
* been revoked, so use the zero page.
*/
crc = do_datacrc ? le32_to_cpu(msg->footer.data_crc) : 0;
- while (cursor->resid) {
+ while (cursor->total_resid) {
struct page *page;
size_t page_offset;
size_t length;
bool last_piece;
int ret;
+ if (!cursor->resid) {
+ ceph_msg_data_advance(cursor, 0);
+ continue;
+ }
+
page = ceph_msg_data_next(cursor, &page_offset, &length,
&last_piece);
ret = ceph_tcp_sendpage(con->sock, page, page_offset,
@@ -2327,7 +2332,12 @@ static int read_partial_msg_data(struct ceph_connection *con)
if (do_datacrc)
crc = con->in_data_crc;
- while (cursor->resid) {
+ while (cursor->total_resid) {
+ if (!cursor->resid) {
+ ceph_msg_data_advance(cursor, 0);
+ continue;
+ }
+
page = ceph_msg_data_next(cursor, &page_offset, &length, NULL);
ret = ceph_tcp_recvpage(con->sock, page, page_offset, length);
if (ret <= 0) {