Ack On Thu, Nov 23, 2023 at 3:28 PM Kui Liu <kui....@acronis.com> wrote: > > In our userspace RDMA implementation, it is required that every > > RIO_MSG_RDMA_READ_REQ msg must be acked strictly in order. However > > this rule can be broken due to a bug in kio, which though is > > triggered by very abnormal hardware behaviour that it can take > > very long time(>10s) for a WR to complete. > > > > This happens in the read workload with large block size that the > > the client needs to issue RDMA READ wr to pull the data portion > > of a response msg returned by csd. When this operation takes very > > long time to complete for a msg, it will block responses to requests > > after it from being sent out by csd for as long as it can take. > > As a result, these requests will be killed due to calendar timout. > > However when these responses arrives later in form of RIO_MSG_RDMA_READ_REQ > > msg, they will be ignored silently due to missing reqeust msg without > > returning corresponding RIO_MSG_RDMA_RAD_ACK back, therefore breaks the > > expectation of ordered ack on the side of csd. Since the rio connection > > is still in working state, a later valid msg exchange will trigger > > the BUGON check of rb->xid in csd, causing it to crash. > > > > This patch makes sure client will always ack every RIO_MSG_RDMA_READ_REQ > > recevied and in order to avoid crashing csd. However it can't address > > any performance impact due to the strange hardware behaviour that it > > takes abnorma long time for a WR to complete. > > > > https://pmc.acronis.work/browse/VSTOR-76834 > > https://pmc.acronis.work/browse/VSTOR-70758 > > https://pmc.acronis.work/browse/VSTOR-60807 > > https://pmc.acronis.work/browse/VSTOR-57903 > > > > Signed-off-by: Liu Kui <kui....@acronis.com> > > --- > > fs/fuse/kio/pcs/pcs_rdma_io.c | 58 +++++++++++++++++++++++++++++++---- > > fs/fuse/kio/pcs/pcs_rdma_io.h | 3 ++ > > 2 files changed, 55 insertions(+), 6 deletions(-) > > > > diff --git a/fs/fuse/kio/pcs/pcs_rdma_io.c b/fs/fuse/kio/pcs/pcs_rdma_io.c > > index 62d138c8b611..c78126ab1d79 100644 > > --- a/fs/fuse/kio/pcs/pcs_rdma_io.c > > +++ b/fs/fuse/kio/pcs/pcs_rdma_io.c > > @@ -130,6 +130,8 @@ static void rio_abort(struct pcs_rdmaio *rio, int error); > > static void rio_rx_done(struct rio_cqe *cqe, bool sync_mode); > > static void rio_tx_done(struct rio_cqe *cqe, bool sync_mode); > > static void rio_tx_err_occured(struct rio_cqe *cqe, bool sync_mode); > > +static int rio_submit(struct pcs_rdmaio *rio, struct pcs_msg *msg, int type, > u64 xid, int status, > > + bool allow_again); > > > > /* Only called when rio->write_queue is not empty */ > > static struct pcs_msg *rio_dequeue_msg(struct pcs_rdmaio *rio) > > @@ -424,6 +426,10 @@ static int rio_submit_rdma_read(struct pcs_rdmaio *rio, > struct pcs_msg *msg, > > struct pcs_rdma_device *dev = rio->dev; > > struct rio_tx *tx; > > > > + /* Blocked until after pending RDMA_READ_ACKs are sent out to > keep ACK in order */ > > + if (rio->n_rdma_read_ack_pending) > > + return -EAGAIN; > > + > > tx = RE_NULL(rio_get_tx(dev)); > > if (!tx) { > > if (allow_again) > > @@ -467,6 +473,8 @@ static int rio_submit_rdma_read(struct pcs_rdmaio *rio, > struct pcs_msg *msg, > > } > > } > > > > + rio->n_rdma_read_ongoing++; > > + > > return 0; > > > > fail: > > @@ -478,6 +486,21 @@ static int rio_submit_rdma_read(struct pcs_rdmaio *rio, > struct pcs_msg *msg, > > return -EIO; > > } > > > > +static int rio_submit_rdma_read_ack(struct pcs_rdmaio *rio, u64 xid) > > +{ > > + int ret; > > + > > + /* Can only be sent after all ongoing RDMA_READ_REQs complete > to keep ack in order */ > > + if (rio->n_rdma_read_ongoing) > > + return -EAGAIN; > > + > > + ret = rio_submit(rio, NULL, SUBMIT_RDMA_READ_ACK, xid, 0, > true); > > + if (!ret) > > + rio->n_rdma_read_ack_pending--; > > + > > + return ret; > > +} > > + > > static int rio_rdma_read_job_work(struct rio_job *j) > > { > > struct rio_rdma_read_job *job = container_of(j, struct > rio_rdma_read_job, job); > > @@ -488,8 +511,15 @@ static int rio_rdma_read_job_work(struct rio_job *j) > > return 0; > > } > > > > - return rio_submit_rdma_read(rio, job->msg, job->offset, > > - &job->rb, > true); > > + /* > > + * Return RDMA_READ_ACK directly if the original request msg > had been killed, > > + * however must wait until all previous RDMA_READ_REQs have > been acked. > > + */ > > + if (job->msg == PCS_TRASH_MSG) > > + return rio_submit_rdma_read_ack(rio, > job->rb.xid); > > + else > > + return rio_submit_rdma_read(rio, job->msg, > job->offset, > > + > &job->rb, true); > > } > > > > static void rio_rdma_read_job_destroy(struct rio_job *j) > > @@ -766,6 +796,7 @@ static void rio_handle_tx(struct pcs_rdmaio *rio, struct > rio_tx *tx, int ok) > > case TX_SUBMIT_RDMA_READ_ACK: > > rio_put_tx(rio->dev, tx); > > rio_submit(rio, NULL, > SUBMIT_RDMA_READ_ACK, xid, !ok, false); > > + rio->n_rdma_read_ongoing--; > > break; > > case TX_WAIT_FOR_TX_COMPL: > > case TX_WAIT_FOR_READ_ACK: > > @@ -798,6 +829,7 @@ static int rio_handle_rx_immediate(struct pcs_rdmaio > *rio, char *buf, int len, > > u32 msg_size; > > int offset = rio->hdr_size; > > struct iov_iter it; > > + struct rio_rdma_read_job *job; > > > > if (rio->throttled) { > > *throttle = 1; > > @@ -820,6 +852,19 @@ static int rio_handle_rx_immediate(struct pcs_rdmaio > *rio, char *buf, int len, > > return err; > > } else if (msg == PCS_TRASH_MSG) { > > TRACE("rio drop trash msg: %u, rio: 0x%p\n", > msg_size, rio); > > + /* > > + * We must Ack every RDMA_READ_REQ received > from our peer in order even it's going to be dropped. > > + * Missing ack will result in out of order ACK > to our peer, which will cause it to crash. > > + * So we setup a job to ack this msg however it > can only be sent out after all ongoing RDMA READ > > + * completes and will block future RDMA READ > being issued. > > + */ > > + if (rb) { > > + job = > rio_rdma_read_job_alloc(rio, msg, 0, rb); > > + if (!job) > > + return > PCS_ERR_NOMEM; > > + rio_post_tx_job(rio, > &job->job); > > + rio->n_rdma_read_ack_pending++; > > + } > > return 0; > > } > > > > @@ -852,12 +897,10 @@ static int rio_handle_rx_immediate(struct pcs_rdmaio > *rio, char *buf, int len, > > if (len == msg->size) { > > msg->done(msg); > > } else if (rio_submit_rdma_read(rio, msg, offset, rb, true) == > -EAGAIN) { > > - struct rio_rdma_read_job *job; > > job = rio_rdma_read_job_alloc(rio, msg, > offset, rb); > > if (!job) > > - rio_submit_rdma_read(rio, > msg, offset, rb, false); > > - else > > - rio_post_tx_job(rio, > &job->job); > > + return PCS_ERR_NOMEM; > > + rio_post_tx_job(rio, &job->job); > > } > > > > return 0; > > @@ -1228,6 +1271,9 @@ struct pcs_rdmaio* pcs_rdma_create(int hdr_size, struct > rdma_cm_id *cmid, > > rio->n_os_credits = 0; > > rio->n_th_credits = queue_depth / 2; > > > > + rio->n_rdma_read_ongoing = 0; > > + rio->n_rdma_read_ack_pending = 0; > > + > > rio->cmid = cmid; > > > > INIT_LIST_HEAD(&rio->write_queue); > > diff --git a/fs/fuse/kio/pcs/pcs_rdma_io.h b/fs/fuse/kio/pcs/pcs_rdma_io.h > > index 18962208e4a2..c5109cbc5fe1 100644 > > --- a/fs/fuse/kio/pcs/pcs_rdma_io.h > > +++ b/fs/fuse/kio/pcs/pcs_rdma_io.h > > @@ -90,6 +90,9 @@ struct pcs_rdmaio > > int n_th_credits; /* threshold: when to return outstanding > > * credits urgently */ > > > > + int n_rdma_read_ongoing; /* number of ongoing > RDMA_READ. */ > > + int n_rdma_read_ack_pending; /* number of RDMA_READ_ACK to be > submitted */ > > + > > struct pcs_rdma_device *dev; > > struct rdma_cm_id *cmid; > > struct ib_cq *cq; > > -- > > 2.32.0 (Apple Git-132) > > _______________________________________________ > Devel mailing list > Devel@openvz.org > https://lists.openvz.org/mailman/listinfo/devel
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