SUNRPC: The RDMA back channel mustn't disappear while requests are outstanding

BugLink: https://bugs.launchpad.net/bugs/1852338
[ Upstream commit 9edb455e6797bb50aa38ef71e62668966065ede8 ]

If there are RDMA back channel requests being processed by the
server threads, then we should hold a reference to the transport
to ensure it doesn't get freed from underneath us.

Reported-by: Neil Brown <neilb@suse.de>
Fixes: 63cae47005af ("xprtrdma: Handle incoming backward direction RPC calls")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/net/sunrpc/xprtrdma/backchannel.c b/net/sunrpc/xprtrdma/backchannel.c
index 59e624b1d7a0d06062ec55a5153bb0e1a539da7f..7cccaab9a17ae2522b862ec0874347f9930f8827 100644 (file)
--- a/net/sunrpc/xprtrdma/backchannel.c
+++ b/net/sunrpc/xprtrdma/backchannel.c
@@ -165,6 +165,7 @@ void xprt_rdma_bc_free_rqst(struct rpc_rqst *rqst)
        spin_lock(&xprt->bc_pa_lock);
        list_add_tail(&rqst->rq_bc_pa_list, &xprt->bc_pa_list);
        spin_unlock(&xprt->bc_pa_lock);
+       xprt_put(xprt);
 }
 
 static struct rpc_rqst *rpcrdma_bc_rqst_get(struct rpcrdma_xprt *r_xprt)
@@ -261,6 +262,7 @@ void rpcrdma_bc_receive_call(struct rpcrdma_xprt *r_xprt,
 
        /* Queue rqst for ULP's callback service */
        bc_serv = xprt->bc_serv;
+       xprt_get(xprt);
        spin_lock(&bc_serv->sv_cb_lock);
        list_add(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
        spin_unlock(&bc_serv->sv_cb_lock);