On 03/16/2018 07:37 AM, Alex Elder wrote:
> From: Ilya Dryomov <idryomov@xxxxxxxxx>
>
> 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@xxxxxxxxx>
I don't think I realized you could advance a message by 0 bytes.
I think it's not really intuitive, although I do think that
encoding a 0-byte data item to mean implicitly zero-filled is
a good convention. Anyway, I feel like there should be an
explicit comment above ceph_msg_data_advance() to explain that
would be good. (Maybe I've just forgotten about this, or maybe
it's explained elsewhere...)
Anwyay, this looks fine to me.
Reviewed-by: Alex Elder <elder@xxxxxxxxxx>
> ---
> net/ceph/messenger.c | 14 ++++++++++++--
> 1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
> index 91a57857cf11..cee4b3d307de 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 * been revoked, so use the zero page.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) {
>
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