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: Alex Elder <elder@dreamhost.com>
Signed-off-by: Sage Weil <sage@newdream.net>
diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index 204e229..7ec6a22 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -521,6 +521,7 @@
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 @@
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 @@
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 @@
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);