Commit 143334ff authored Mar 29, 2013 by Alex Elder Committed by Sage Weil May 01, 2013

libceph: don't add to crc unless data sent

In write_partial_message_data() we aggregate the crc for the data
portion of the message as each new piece of the data item is
encountered.  Because it was computed *before* sending the data, if
an attempt to send a new piece resulted in 0 bytes being sent, the
crc crc across that piece would erroneously get computed again and
added to the aggregate result.  This would occasionally happen in
the evnet of a connection failure.

The crc value isn't really needed until the complete value is known
after sending all data, so there's no need to compute it before
sending.

So don't calculate the crc for a piece until *after* we know at
least one byte of it has been sent.  That will avoid this problem.

This resolves:
    http://tracker.ceph.com/issues/4450



Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>

parent f5db90bc

net/ceph/messenger.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -1467,8 +1467,6 @@ static int write_partial_message_data(struct ceph_connection *con)

		page = ceph_msg_data_next(&msg->data, &page_offset, &length,
		&last_piece);
		if (do_datacrc && cursor->need_crc)
		crc = ceph_crc32c_page(crc, page, page_offset, length);
		ret = ceph_tcp_sendpage(con->sock, page, page_offset,
		length, last_piece);
		if (ret <= 0) {
		@@ -1477,6 +1475,8 @@ static int write_partial_message_data(struct ceph_connection *con)

		return ret;
		}
		if (do_datacrc && cursor->need_crc)
		crc = ceph_crc32c_page(crc, page, page_offset, length);
		out_msg_pos_next(con, page, length, (size_t) ret);
		}

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