From: "D. Wythe" <alibuda@linux.alibaba.com> mainline inclusion from mainline-v6.3-rc1 commit 4da687448de7b51dcca9d024c6049fa223f5363f category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/IC914B Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- Unlike smc_buf_create() and smcr_buf_unuse(), smcr_lgr_reg_rmbs() is exclusive when assigned rmb_desc was not registered, although it can be executed in parallel when assigned rmb_desc was registered already and only performs read semtamics on it. Hence, we can not simply replace it with read semaphore. The idea here is that if the assigned rmb_desc was registered already, use read semaphore to protect the critical section, once the assigned rmb_desc was not registered, keep using keep write semaphore still to keep its exclusivity. Thanks to the reusable features of rmb_desc, which allows us to execute in parallel in most cases. Signed-off-by: D. Wythe <alibuda@linux.alibaba.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Wang Liang <wangliang74@huawei.com> --- net/smc/af_smc.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c index 6d3c2744f539..139df50c99ef 100644 --- a/net/smc/af_smc.c +++ b/net/smc/af_smc.c @@ -499,11 +499,26 @@ static int smcr_lgr_reg_rmbs(struct smc_link *link, struct smc_buf_desc *rmb_desc) { struct smc_link_group *lgr = link->lgr; + bool do_slow = false; int i, rc = 0; rc = smc_llc_flow_initiate(lgr, SMC_LLC_FLOW_RKEY); if (rc) return rc; + + down_read(&lgr->llc_conf_mutex); + for (i = 0; i < SMC_LINKS_PER_LGR_MAX; i++) { + if (!smc_link_active(&lgr->lnk[i])) + continue; + if (!rmb_desc->is_reg_mr[link->link_idx]) { + up_read(&lgr->llc_conf_mutex); + goto slow_path; + } + } + /* mr register already */ + goto fast_path; +slow_path: + do_slow = true; /* protect against parallel smc_llc_cli_rkey_exchange() and * parallel smcr_link_reg_buf() */ @@ -515,7 +530,7 @@ static int smcr_lgr_reg_rmbs(struct smc_link *link, if (rc) goto out; } - +fast_path: /* exchange confirm_rkey msg with peer */ rc = smc_llc_do_confirm_rkey(link, rmb_desc); if (rc) { @@ -524,7 +539,7 @@ static int smcr_lgr_reg_rmbs(struct smc_link *link, } rmb_desc->is_conf_rkey = true; out: - up_write(&lgr->llc_conf_mutex); + do_slow ? up_write(&lgr->llc_conf_mutex) : up_read(&lgr->llc_conf_mutex); smc_llc_flow_stop(lgr, &lgr->llc_flow_lcl); return rc; } -- 2.34.1