> -----Original Message----- > From: Steve Wise [mailto:swise@xxxxxxxxxxxxxxxxxxxxx] > Sent: Monday, November 16, 2015 10:38 AM > To: Sagi Grimberg; Christoph Hellwig; linux-rdma@xxxxxxxxxxxxxxx > Cc: bart.vanassche@xxxxxxxxxxx; axboe@xxxxxx; linux-scsi@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx > Subject: Re: [PATCH 3/9] IB: add a helper to safely drain a QP > > On 11/15/2015 3:34 AM, Sagi Grimberg wrote: > > > >> + > >> +struct ib_stop_cqe { > >> + struct ib_cqe cqe; > >> + struct completion done; > >> +}; > >> + > >> +static void ib_stop_done(struct ib_cq *cq, struct ib_wc *wc) > >> +{ > >> + struct ib_stop_cqe *stop = > >> + container_of(wc->wr_cqe, struct ib_stop_cqe, cqe); > >> + > >> + complete(&stop->done); > >> +} > >> + > >> +/* > >> + * Change a queue pair into the error state and wait until all receive > >> + * completions have been processed before destroying it. This avoids > >> that > >> + * the receive completion handler can access the queue pair while it is > >> + * being destroyed. > >> + */ > >> +void ib_drain_qp(struct ib_qp *qp) > >> +{ > >> + struct ib_qp_attr attr = { .qp_state = IB_QPS_ERR }; > >> + struct ib_stop_cqe stop = { }; > >> + struct ib_recv_wr wr, *bad_wr; > >> + int ret; > >> + > >> + wr.wr_cqe = &stop.cqe; > >> + stop.cqe.done = ib_stop_done; > >> + init_completion(&stop.done); > >> + > >> + ret = ib_modify_qp(qp, &attr, IB_QP_STATE); > >> + if (ret) { > >> + WARN_ONCE(ret, "failed to drain QP: %d\n", ret); > >> + return; > >> + } > >> + > >> + ret = ib_post_recv(qp, &wr, &bad_wr); > >> + if (ret) { > >> + WARN_ONCE(ret, "failed to drain QP: %d\n", ret); > >> + return; > >> + } > >> + > >> + wait_for_completion(&stop.done); > >> +} > > > > This is taken from srp, and srp drains using a recv wr due to a race > > causing a use-after-free condition in srp which re-posts a recv buffer > > in the recv completion handler. srp does not really care if there are > > pending send flushes. > > > > I'm not sure if there are ordering rules for send/recv queues in > > terms of flush completions, meaning that even if all recv flushes > > were consumed maybe there are send flushes still pending. > > > > I think that for a general drain helper it would be useful to > > make sure that both the recv _and_ send flushes were drained. > > > > So, something like: > > > > void ib_drain_qp(struct ib_qp *qp) > > { > > struct ib_qp_attr attr = { .qp_state = IB_QPS_ERR }; > > struct ib_stop_cqe rstop, sstop; > > struct ib_recv_wr rwr = {}, *bad_rwr; > > struct ib_send_wr swr = {}, *bad_swr; > > int ret; > > > > rwr.wr_cqe = &rstop.cqe; > > rstop.cqe.done = ib_stop_done; > > init_completion(&rstop.done); > > > > swr.wr_cqe = &sstop.cqe; > > sstop.cqe.done = ib_stop_done; > > init_completion(&sstop.done); > > > > ret = ib_modify_qp(qp, &attr, IB_QP_STATE); > > if (ret) { > > WARN_ONCE(ret, "failed to drain QP: %d\n", ret); > > return; > > } > > > > ret = ib_post_recv(qp, &rwr, &bad_rwr); > > if (ret) { > > WARN_ONCE(ret, "failed to drain recv queue: %d\n", ret); > > return; > > } > > > > ret = ib_post_send(qp, &swr, &bad_swr); > > if (ret) { > > WARN_ONCE(ret, "failed to drain send queue: %d\n", ret); > > return; > > } > > > > wait_for_completion(&rstop.done); > > wait_for_completion(&sstop.done); > > } > > > > Thoughts? > > This won't work for iWARP as per my previous email. But I will code > something up that will. > > Steve After looking at the nes driver, I don't see any common way to support drain w/o some serious driver mods. Since SRP is the only user, perhaps we can ignore iWARP for this function... -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
