[PATCH 5.15 170/262] net/smc: fix unexpected SMC_CLC_DECL_ERR_REGRMB error generated by client

From: Greg Kroah-Hartman
Date: Mon Mar 07 2022 - 05:11:33 EST


From: D. Wythe <alibuda@xxxxxxxxxxxxxxxxx>

commit 0537f0a2151375dcf90c1bbfda6a0aaf57164e89 upstream.

The main reason for this unexpected SMC_CLC_DECL_ERR_REGRMB in client
dues to following execution sequence:

Server Conn A: Server Conn B: Client Conn B:

smc_lgr_unregister_conn
smc_lgr_register_conn
smc_clc_send_accept ->
smc_rtoken_add
smcr_buf_unuse
-> Client Conn A:
smc_rtoken_delete

smc_lgr_unregister_conn() makes current link available to assigned to new
incoming connection, while smcr_buf_unuse() has not executed yet, which
means that smc_rtoken_add may fail because of insufficient rtoken_entry,
reversing their execution order will avoid this problem.

Fixes: 3e034725c0d8 ("net/smc: common functions for RMBs and send buffers")
Signed-off-by: D. Wythe <alibuda@xxxxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/smc/smc_core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -1061,8 +1061,8 @@ void smc_conn_free(struct smc_connection
cancel_work_sync(&conn->abort_work);
}
if (!list_empty(&lgr->list)) {
- smc_lgr_unregister_conn(conn);
smc_buf_unuse(conn, lgr); /* allow buffer reuse */
+ smc_lgr_unregister_conn(conn);
}

if (!lgr->conns_num)