Commit a9a0c51a authored by Alex Elder's avatar Alex Elder
Browse files

libceph: separate CRC calculation from byte swapping 



Calculate CRC in a separate step from rearranging the byte order
of the result, to improve clarity and readability.

Use offsetof() to determine the number of bytes to include in the
CRC calculation.

In read_partial_message(), switch which value gets byte-swapped,
since the just-computed CRC is already likely to be in a register.

Signed-off-by: default avatarAlex Elder <elder@dreamhost.com>
Signed-off-by: default avatarSage Weil <sage@newdream.net>
parent bca064d2

net/ceph/messenger.c

+17 −14
Original line number Diff line number Diff line
@@ -521,6 +521,7 @@ static void prepare_write_message_footer(struct ceph_connection *con) 
static void prepare_write_message(struct ceph_connection *con)

{

	struct ceph_msg *m;

	u32 crc;



	ceph_con_out_kvec_reset(con);

	con->out_kvec_is_msg = true;
@@ -569,17 +570,17 @@ static void prepare_write_message(struct ceph_connection *con) 
			m->middle->vec.iov_base);



	/* fill in crc (except data pages), footer */

	con->out_msg->hdr.crc =

		cpu_to_le32(crc32c(0, &m->hdr,

				      sizeof(m->hdr) - sizeof(m->hdr.crc)));

	crc = crc32c(0, &m->hdr, offsetof(struct ceph_msg_header, crc));

	con->out_msg->hdr.crc = cpu_to_le32(crc);

	con->out_msg->footer.flags = CEPH_MSG_FOOTER_COMPLETE;

	con->out_msg->footer.front_crc =

		cpu_to_le32(crc32c(0, m->front.iov_base, m->front.iov_len));

	if (m->middle)

		con->out_msg->footer.middle_crc =

			cpu_to_le32(crc32c(0, m->middle->vec.iov_base,

					   m->middle->vec.iov_len));

	else



	crc = crc32c(0, m->front.iov_base, m->front.iov_len);

	con->out_msg->footer.front_crc = cpu_to_le32(crc);

	if (m->middle) {

		crc = crc32c(0, m->middle->vec.iov_base,

				m->middle->vec.iov_len);

		con->out_msg->footer.middle_crc = cpu_to_le32(crc);

	} else

		con->out_msg->footer.middle_crc = 0;

	con->out_msg->footer.data_crc = 0;

	dout("prepare_write_message front_crc %u data_crc %u\n",
@@ -875,12 +876,13 @@ static int write_partial_msg_pages(struct ceph_connection *con) 
			    total_max_write);



		if (do_crc && !con->out_msg_pos.did_page_crc) {

			u32 crc;

			void *base = kaddr + con->out_msg_pos.page_pos;

			u32 tmpcrc = le32_to_cpu(con->out_msg->footer.data_crc);



			BUG_ON(kaddr == NULL);

			con->out_msg->footer.data_crc =

				cpu_to_le32(crc32c(tmpcrc, base, len));

			crc = crc32c(tmpcrc, base, len);

			con->out_msg->footer.data_crc = cpu_to_le32(crc);

			con->out_msg_pos.did_page_crc = true;

		}

		ret = kernel_sendpage(con->sock, page,
@@ -1650,8 +1652,9 @@ static int read_partial_message(struct ceph_connection *con) 
		con->in_base_pos += ret;

		if (con->in_base_pos == sizeof(con->in_hdr)) {

			u32 crc = crc32c(0, &con->in_hdr,

				 sizeof(con->in_hdr) - sizeof(con->in_hdr.crc));

			if (crc != le32_to_cpu(con->in_hdr.crc)) {

					offsetof(struct ceph_msg_header, crc));



			if (cpu_to_le32(crc) != con->in_hdr.crc) {

				pr_err("read_partial_message bad hdr "

				       " crc %u != expected %u\n",

				       crc, con->in_hdr.crc);

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