On Wed, Feb 14, 2018 at 5:28 AM, Sowmini Varadhan <sowmini.varad...@oracle.com> wrote: > RDS removes a datagram (rds_message) from the retransmit queue when > an ACK is received. The ACK indicates that the receiver has queued > the RDS datagram, so that the sender can safely forget the datagram. > When all references to the rds_message are quiesced, rds_message_purge > is called to release resources used by the rds_message > > If the datagram to be removed had pinned pages set up, add > an entry to the rs->rs_znotify_queue so that the notifcation > will be sent up via rds_rm_zerocopy_callback() when the > rds_message is eventually freed by rds_message_purge. > > rds_rm_zerocopy_callback() attempts to batch the number of cookies > sent with each notification to a max of SO_EE_ORIGIN_MAX_ZCOOKIES. > This is achieved by checking the tail skb in the sk_error_queue: > if this has room for one more cookie, the cookie from the > current notification is added; else a new skb is added to the > sk_error_queue. Every invocation of rds_rm_zerocopy_callback() will > trigger a ->sk_error_report to notify the application. > > Signed-off-by: Sowmini Varadhan <sowmini.varad...@oracle.com> > ---
> +static void rds_rm_zerocopy_callback(struct rds_sock *rs, > + struct rds_znotifier *znotif) > +{ > + struct sock *sk = rds_rs_to_sk(rs); > + struct sk_buff *skb, *tail; > + struct sock_exterr_skb *serr; > + unsigned long flags; > + struct sk_buff_head *q; > + u32 cookie = znotif->z_cookie; > + > + q = &sk->sk_error_queue; > + spin_lock_irqsave(&q->lock, flags); > + tail = skb_peek_tail(q); > + > + if (tail && skb_zcookie_add(tail, cookie)) { > + spin_unlock_irqrestore(&q->lock, flags); > + mm_unaccount_pinned_pages(&znotif->z_mmp); > + consume_skb(rds_skb_from_znotifier(znotif)); > + sk->sk_error_report(sk); > + return; > + } > + > + skb = rds_skb_from_znotifier(znotif); > + serr = SKB_EXT_ERR(skb); > + serr->ee.ee_errno = 0; > + serr->ee.ee_origin = SO_EE_ORIGIN_ZCOOKIE; > + serr->ee.ee_info = 0; > + serr->ee.ee_code |= SO_EE_CODE_ZEROCOPY_COPIED; One more thing: this code notifies that the operation succeeded, but the data was copied in the process. It does not have to be set otherwise.