lwn.git/net/smc/smc_cdc.c, branch docs-next

net/smc: adapt cursor update when sndbuf and peer DMB are merged

2024-04-30T11:24:48+00:00

If the local sndbuf shares the same physical memory with peer DMB, the cursor update processing needs to be adapted to ensure that the data to be consumed won't be overwritten. So in this case, the fin_curs and sndbuf_space that were originally updated after sending the CDC message should be modified to not be update until the peer updates cons_curs. Signed-off-by: Wen Gu Reviewed-by: Wenjia Zhang Reviewed-and-tested-by: Jan Karcher Signed-off-by: Paolo Abeni

net/smc: allow cdc msg send rather than drop it with NULL sndbuf_desc

2023-11-06T10:01:07+00:00

This patch re-fix the issues mentioned by commit 22a825c541d7 ("net/smc: fix NULL sndbuf_desc in smc_cdc_tx_handler()"). Blocking sending message do solve the issues though, but it also prevents the peer to receive the final message. Besides, in logic, whether the sndbuf_desc is NULL or not have no impact on the processing of cdc message sending. Hence that, this patch allows the cdc message sending but to check the sndbuf_desc with care in smc_cdc_tx_handler(). Fixes: 22a825c541d7 ("net/smc: fix NULL sndbuf_desc in smc_cdc_tx_handler()") Signed-off-by: D. Wythe Reviewed-by: Dust Li Signed-off-by: David S. Miller

net/smc: fix dangling sock under state SMC_APPFINCLOSEWAIT

2023-11-06T10:01:07+00:00

Considering scenario: smc_cdc_rx_handler __smc_release sock_set_flag smc_close_active() sock_set_flag __set_bit(DEAD) __set_bit(DONE) Dues to __set_bit is not atomic, the DEAD or DONE might be lost. if the DEAD flag lost, the state SMC_CLOSED will be never be reached in smc_close_passive_work: if (sock_flag(sk, SOCK_DEAD) && smc_close_sent_any_close(conn)) { sk->sk_state = SMC_CLOSED; } else { /* just shutdown, but not yet closed locally */ sk->sk_state = SMC_APPFINCLOSEWAIT; } Replace sock_set_flags or __set_bit to set_bit will fix this problem. Since set_bit is atomic. Fixes: b38d732477e4 ("smc: socket closing and linkgroup cleanup") Signed-off-by: D. Wythe Reviewed-by: Dust Li Signed-off-by: David S. Miller

net/smc: fix NULL sndbuf_desc in smc_cdc_tx_handler()

2023-03-13T23:03:58+00:00

When performing a stress test on SMC-R by rmmod mlx5_ib driver during the wrk/nginx test, we found that there is a probability of triggering a panic while terminating all link groups. This issue dues to the race between smc_smcr_terminate_all() and smc_buf_create(). smc_smcr_terminate_all smc_buf_create /* init */ conn->sndbuf_desc = NULL; ... __smc_lgr_terminate smc_conn_kill smc_close_abort smc_cdc_get_slot_and_msg_send __softirqentry_text_start smc_wr_tx_process_cqe smc_cdc_tx_handler READ(conn->sndbuf_desc->len); /* panic dues to NULL sndbuf_desc */ conn->sndbuf_desc = xxx; This patch tries to fix the issue by always to check the sndbuf_desc before send any cdc msg, to make sure that no null pointer is seen during cqe processing. Fixes: 0b29ec643613 ("net/smc: immediate termination for SMCR link groups") Signed-off-by: D. Wythe Reviewed-by: Tony Lu Reviewed-by: Wenjia Zhang Link: https://lore.kernel.org/r/1678263432-17329-1-git-send-email-alibuda@linux.alibaba.com Signed-off-by: Jakub Kicinski

net/smc: fixes for converting from "struct smc_cdc_tx_pend **" to "struct smc_wr_tx_pend_priv *"

2022-05-28T11:36:26+00:00

"struct smc_cdc_tx_pend **" can not directly convert to "struct smc_wr_tx_pend_priv *". Fixes: 2bced6aefa3d ("net/smc: put slot when connection is killed") Signed-off-by: Guangguan Wang Signed-off-by: David S. Miller

net/smc: don't send in the BH context if sock_owned_by_user

2022-03-01T14:25:12+00:00

Send data all the way down to the RDMA device is a time consuming operation(get a new slot, maybe do RDMA Write and send a CDC, etc). Moving those operations from BH to user context is good for performance. If the sock_lock is hold by user, we don't try to send data out in the BH context, but just mark we should send. Since the user will release the sock_lock soon, we can do the sending there. Add smc_release_cb() which will be called in release_sock() and try send in the callback if needed. This patch moves the sending part out from BH if sock lock is hold by user. In my testing environment, this saves about 20% softirq in the qperf 4K tcp_bw test in the sender side with no noticeable throughput drop. Signed-off-by: Dust Li Signed-off-by: David S. Miller

net/smc: add autocorking support

2022-03-01T14:25:12+00:00

This patch adds autocorking support for SMC which could improve throughput for small message by x3+. The main idea is borrowed from TCP autocorking with some RDMA specific modification: 1. The first message should never cork to make sure we won't bring extra latency 2. If we have posted any Tx WRs to the NIC that have not completed, cork the new messages until: a) Receive CQE for the last Tx WR b) We have corked enough message on the connection 3. Try to push the corked data out when we receive CQE of the last Tx WR to prevent the corked messages hang in the send queue. Both SMC autocorking and TCP autocorking check the TX completion to decide whether we should cork or not. The difference is when we got a SMC Tx WR completion, the data have been confirmed by the RNIC while TCP TX completion just tells us the data have been sent out by the local NIC. Add an atomic variable tx_pushing in smc_connection to make sure only one can send to let it cork more and save CDC slot. SMC autocorking should not bring extra latency since the first message will always been sent out immediately. The qperf tcp_bw test shows more than x4 increase under small message size with Mellanox connectX4-Lx, same result with other throughput benchmarks like sockperf/netperf. The qperf tcp_lat test shows SMC autocorking has not increase any ping-pong latency. Test command: client: smc_run taskset -c 1 qperf smc-server -oo msg_size:1:64K:*2 \ -t 30 -vu tcp_{bw|lat} server: smc_run taskset -c 1 qperf === Bandwidth ==== MsgSize(Bytes) SMC-NoCork TCP SMC-AutoCorking 1 0.578 MB/s 2.392 MB/s(313.57%) 2.647 MB/s(357.72%) 2 1.159 MB/s 4.780 MB/s(312.53%) 5.153 MB/s(344.71%) 4 2.283 MB/s 10.266 MB/s(349.77%) 10.363 MB/s(354.02%) 8 4.668 MB/s 19.040 MB/s(307.86%) 21.215 MB/s(354.45%) 16 9.147 MB/s 38.904 MB/s(325.31%) 41.740 MB/s(356.32%) 32 18.369 MB/s 79.587 MB/s(333.25%) 82.392 MB/s(348.52%) 64 36.562 MB/s 148.668 MB/s(306.61%) 161.564 MB/s(341.89%) 128 72.961 MB/s 274.913 MB/s(276.80%) 325.363 MB/s(345.94%) 256 144.705 MB/s 512.059 MB/s(253.86%) 633.743 MB/s(337.96%) 512 288.873 MB/s 884.977 MB/s(206.35%) 1250.681 MB/s(332.95%) 1024 574.180 MB/s 1337.736 MB/s(132.98%) 2246.121 MB/s(291.19%) 2048 1095.192 MB/s 1865.952 MB/s( 70.38%) 2057.767 MB/s( 87.89%) 4096 2066.157 MB/s 2380.337 MB/s( 15.21%) 2173.983 MB/s( 5.22%) 8192 3717.198 MB/s 2733.073 MB/s(-26.47%) 3491.223 MB/s( -6.08%) 16384 4742.221 MB/s 2958.693 MB/s(-37.61%) 4637.692 MB/s( -2.20%) 32768 5349.550 MB/s 3061.285 MB/s(-42.77%) 5385.796 MB/s( 0.68%) 65536 5162.919 MB/s 3731.408 MB/s(-27.73%) 5223.890 MB/s( 1.18%) ==== Latency ==== MsgSize(Bytes) SMC-NoCork TCP SMC-AutoCorking 1 10.540 us 11.938 us( 13.26%) 10.573 us( 0.31%) 2 10.996 us 11.992 us( 9.06%) 10.269 us( -6.61%) 4 10.229 us 11.687 us( 14.25%) 10.240 us( 0.11%) 8 10.203 us 11.653 us( 14.21%) 10.402 us( 1.95%) 16 10.530 us 11.313 us( 7.44%) 10.599 us( 0.66%) 32 10.241 us 11.586 us( 13.13%) 10.223 us( -0.18%) 64 10.693 us 11.652 us( 8.97%) 10.251 us( -4.13%) 128 10.597 us 11.579 us( 9.27%) 10.494 us( -0.97%) 256 10.409 us 11.957 us( 14.87%) 10.710 us( 2.89%) 512 11.088 us 12.505 us( 12.78%) 10.547 us( -4.88%) 1024 11.240 us 12.255 us( 9.03%) 10.787 us( -4.03%) 2048 11.485 us 16.970 us( 47.76%) 11.256 us( -1.99%) 4096 12.077 us 13.948 us( 15.49%) 12.230 us( 1.27%) 8192 13.683 us 16.693 us( 22.00%) 13.786 us( 0.75%) 16384 16.470 us 23.615 us( 43.38%) 16.459 us( -0.07%) 32768 22.540 us 40.966 us( 81.75%) 23.284 us( 3.30%) 65536 34.192 us 73.003 us(113.51%) 34.233 us( 0.12%) With SMC autocorking support, we can archive better throughput than TCP in most message sizes without any latency trade-off. Signed-off-by: Dust Li Signed-off-by: David S. Miller

net/smc: Introduce a new conn->lgr validity check helper

2022-01-13T13:14:53+00:00

It is no longer suitable to identify whether a smc connection is registered in a link group through checking if conn->lgr is NULL, because conn->lgr won't be reset even the connection is unregistered from a link group. So this patch introduces a new helper smc_conn_lgr_valid() and replaces all the check of conn->lgr in original implementation with the new helper to judge if conn->lgr is valid to use. Signed-off-by: Wen Gu Signed-off-by: David S. Miller

net/smc: fix kernel panic caused by race of smc_sock

2021-12-28T12:42:45+00:00

A crash occurs when smc_cdc_tx_handler() tries to access smc_sock but smc_release() has already freed it. [ 4570.695099] BUG: unable to handle page fault for address: 000000002eae9e88 [ 4570.696048] #PF: supervisor write access in kernel mode [ 4570.696728] #PF: error_code(0x0002) - not-present page [ 4570.697401] PGD 0 P4D 0 [ 4570.697716] Oops: 0002 [#1] PREEMPT SMP NOPTI [ 4570.698228] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.16.0-rc4+ #111 [ 4570.699013] Hardware name: Alibaba Cloud Alibaba Cloud ECS, BIOS 8c24b4c 04/0 [ 4570.699933] RIP: 0010:_raw_spin_lock+0x1a/0x30 <...> [ 4570.711446] Call Trace: [ 4570.711746] [ 4570.711992] smc_cdc_tx_handler+0x41/0xc0 [ 4570.712470] smc_wr_tx_tasklet_fn+0x213/0x560 [ 4570.712981] ? smc_cdc_tx_dismisser+0x10/0x10 [ 4570.713489] tasklet_action_common.isra.17+0x66/0x140 [ 4570.714083] __do_softirq+0x123/0x2f4 [ 4570.714521] irq_exit_rcu+0xc4/0xf0 [ 4570.714934] common_interrupt+0xba/0xe0 Though smc_cdc_tx_handler() checked the existence of smc connection, smc_release() may have already dismissed and released the smc socket before smc_cdc_tx_handler() further visits it. smc_cdc_tx_handler() |smc_release() if (!conn) | | |smc_cdc_tx_dismiss_slots() | smc_cdc_tx_dismisser() | |sock_put(&smc->sk) <- last sock_put, | smc_sock freed bh_lock_sock(&smc->sk) (panic) | To make sure we won't receive any CDC messages after we free the smc_sock, add a refcount on the smc_connection for inflight CDC message(posted to the QP but haven't received related CQE), and don't release the smc_connection until all the inflight CDC messages haven been done, for both success or failed ones. Using refcount on CDC messages brings another problem: when the link is going to be destroyed, smcr_link_clear() will reset the QP, which then remove all the pending CQEs related to the QP in the CQ. To make sure all the CQEs will always come back so the refcount on the smc_connection can always reach 0, smc_ib_modify_qp_reset() was replaced by smc_ib_modify_qp_error(). And remove the timeout in smc_wr_tx_wait_no_pending_sends() since we need to wait for all pending WQEs done, or we may encounter use-after- free when handling CQEs. For IB device removal routine, we need to wait for all the QPs on that device been destroyed before we can destroy CQs on the device, or the refcount on smc_connection won't reach 0 and smc_sock cannot be released. Fixes: 5f08318f617b ("smc: connection data control (CDC)") Reported-by: Wen Gu Signed-off-by: Dust Li Signed-off-by: David S. Miller

net/smc: improved fix wait on already cleared link

2021-10-08T16:00:16+00:00

Commit 8f3d65c16679 ("net/smc: fix wait on already cleared link") introduced link refcounting to avoid waits on already cleared links. This patch extents and improves the refcounting to cover all remaining possible cases for this kind of error situation. Fixes: 15e1b99aadfb ("net/smc: no WR buffer wait for terminating link group") Signed-off-by: Karsten Graul Signed-off-by: David S. Miller