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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, "D. Wythe" <alibuda@linux.alibaba.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.19 28/51] net/smc: fix unexpected SMC_CLC_DECL_ERR_REGRMB error cause by server
Date:   Mon,  7 Mar 2022 10:19:03 +0100
Message-Id: <20220307091637.792801662@linuxfoundation.org>
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From: D. Wythe <alibuda@linux.alibaba.com>

commit 4940a1fdf31c39f0806ac831cde333134862030b upstream.

The problem of SMC_CLC_DECL_ERR_REGRMB on the server is very clear.
Based on the fact that whether a new SMC connection can be accepted or
not depends on not only the limit of conn nums, but also the available
entries of rtoken. Since the rtoken release is trigger by peer, while
the conn nums is decrease by local, tons of thing can happen in this
time difference.

This only thing that needs to be mentioned is that now all connection
creations are completely protected by smc_server_lgr_pending lock, it's
enough to check only the available entries in rtokens_used_mask.

Fixes: cd6851f30386 ("smc: remote memory buffers (RMBs)")
Signed-off-by: D. Wythe <alibuda@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/smc/smc_core.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -609,7 +609,8 @@ int smc_conn_create(struct smc_sock *smc
 		    !lgr->sync_err &&
 		    lgr->vlan_id == vlan_id &&
 		    (role == SMC_CLNT ||
-		     lgr->conns_num < SMC_RMBS_PER_LGR_MAX)) {
+		    (lgr->conns_num < SMC_RMBS_PER_LGR_MAX &&
+		      !bitmap_full(lgr->rtokens_used_mask, SMC_RMBS_PER_LGR_MAX)))) {
 			/* link group found */
 			local_contact = SMC_REUSE_CONTACT;
 			conn->lgr = lgr;