This is a note to let you know that I've just added the patch titled svcrdma: Hold private mutex while invoking rdma_accept() to the 5.11-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: svcrdma-hold-private-mutex-while-invoking-rdma_accep.patch and it can be found in the queue-5.11 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit b5bc7278d13367d37e8200a5faa183fc53837e5c Author: Chuck Lever <chuck.lever@xxxxxxxxxx> Date: Tue Feb 9 10:48:57 2021 -0500 svcrdma: Hold private mutex while invoking rdma_accept() [ Upstream commit 0ac24c320c4d89a9de6ec802591398b8675c7b3c ] RDMA core mutex locking was restructured by commit d114c6feedfe ("RDMA/cma: Add missing locking to rdma_accept()") [Aug 2020]. When lock debugging is enabled, the RPC/RDMA server trips over the new lockdep assertion in rdma_accept() because it doesn't call rdma_accept() from its CM event handler. As a temporary fix, have svc_rdma_accept() take the handler_mutex explicitly. In the meantime, let's consider how to restructure the RPC/RDMA transport to invoke rdma_accept() from the proper context. Calls to svc_rdma_accept() are serialized with calls to svc_rdma_free() by the generic RPC server layer. Suggested-by: Jason Gunthorpe <jgg@xxxxxxxxxx> Link: https://lore.kernel.org/linux-rdma/20210209154014.GO4247@xxxxxxxxxx/ Fixes: d114c6feedfe ("RDMA/cma: Add missing locking to rdma_accept()") Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c index afba4e9d5425d..c895f80df659c 100644 --- a/net/sunrpc/xprtrdma/svc_rdma_transport.c +++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c @@ -475,9 +475,6 @@ static struct svc_xprt *svc_rdma_accept(struct svc_xprt *xprt) if (!svc_rdma_post_recvs(newxprt)) goto errout; - /* Swap out the handler */ - newxprt->sc_cm_id->event_handler = svc_rdma_cma_handler; - /* Construct RDMA-CM private message */ pmsg.cp_magic = rpcrdma_cmp_magic; pmsg.cp_version = RPCRDMA_CMP_VERSION; @@ -498,7 +495,10 @@ static struct svc_xprt *svc_rdma_accept(struct svc_xprt *xprt) } conn_param.private_data = &pmsg; conn_param.private_data_len = sizeof(pmsg); + rdma_lock_handler(newxprt->sc_cm_id); + newxprt->sc_cm_id->event_handler = svc_rdma_cma_handler; ret = rdma_accept(newxprt->sc_cm_id, &conn_param); + rdma_unlock_handler(newxprt->sc_cm_id); if (ret) { trace_svcrdma_accept_err(newxprt, ret); goto errout;