Re: [PATCH net-next v3 2/2] net/smc: handle -ENOMEM from smc_wr_alloc_link_mem gracefully
From: Paolo Abeni <pabeni@redhat.com>
Date: 2025-09-25 09:40:46
Also in:
linux-doc, linux-rdma, linux-s390, lkml
On 9/21/25 11:44 PM, Halil Pasic wrote:
quoted hunk ↗ jump to hunk
@@ -836,27 +838,39 @@ int smcr_link_init(struct smc_link_group *lgr, struct smc_link *lnk, rc = smc_llc_link_init(lnk); if (rc) goto out; - rc = smc_wr_alloc_link_mem(lnk); - if (rc) - goto clear_llc_lnk; rc = smc_ib_create_protection_domain(lnk); if (rc) - goto free_link_mem; - rc = smc_ib_create_queue_pair(lnk); - if (rc) - goto dealloc_pd; + goto clear_llc_lnk; + do { + rc = smc_ib_create_queue_pair(lnk); + if (rc) + goto dealloc_pd; + rc = smc_wr_alloc_link_mem(lnk); + if (!rc) + break; + else if (rc != -ENOMEM) /* give up */ + goto destroy_qp; + /* retry with smaller ... */ + lnk->max_send_wr /= 2; + lnk->max_recv_wr /= 2; + /* ... unless droping below old SMC_WR_BUF_SIZE */ + if (lnk->max_send_wr < 16 || lnk->max_recv_wr < 48) + goto destroy_qp;
If i.e. smc.sysctl_smcr_max_recv_wr == 2048, and smc.sysctl_smcr_max_send_wr == 16, the above loop can give-up a little too early - after the first failure. What about changing the termination condition to: lnk->max_send_wr < 16 && lnk->max_recv_wr < 48 and use 2 as a lower bound for both lnk->max_send_wr and lnk->max_recv_wr? Thanks, Paolo