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>
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@ -1605,13 +1605,18 @@ static int write_partial_message_data(struct ceph_connection *con)
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* been revoked, so use the zero page.
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*/
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crc = do_datacrc ? le32_to_cpu(msg->footer.data_crc) : 0;
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while (cursor->resid) {
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while (cursor->total_resid) {
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struct page *page;
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size_t page_offset;
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size_t length;
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bool last_piece;
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int ret;
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if (!cursor->resid) {
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ceph_msg_data_advance(cursor, 0);
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continue;
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}
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page = ceph_msg_data_next(cursor, &page_offset, &length,
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&last_piece);
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ret = ceph_tcp_sendpage(con->sock, page, page_offset,
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@ -2327,7 +2332,12 @@ static int read_partial_msg_data(struct ceph_connection *con)
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if (do_datacrc)
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crc = con->in_data_crc;
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while (cursor->resid) {
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while (cursor->total_resid) {
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if (!cursor->resid) {
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ceph_msg_data_advance(cursor, 0);
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continue;
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}
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page = ceph_msg_data_next(cursor, &page_offset, &length, NULL);
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ret = ceph_tcp_recvpage(con->sock, page, page_offset, length);
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if (ret <= 0) {
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