[PATCH 1/3] SUNRPC: The TCP back channel mustn't disappear while requests are outstanding

Trond Myklebust
2019-10-16T14:17:59Z

If there are TCP back channel requests either 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: 2ea24497a1b3 ("SUNRPC: RPC callbacks may be split across several..")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
net/sunrpc/backchannel_rqst.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/sunrpc/backchannel_rqst.c b/net/sunrpc/backchannel_rqst.c
index 339e8c077c2d..7eb251372f94 100644
--- a/net/sunrpc/backchannel_rqst.c
+++ b/net/sunrpc/backchannel_rqst.c
@@ -307,8 +307,8 @@ void xprt_free_bc_rqst(struct rpc_rqst *req)
*/
dprintk("RPC: Last session removed req=%p\n", req);
xprt_free_allocation(req);
- return;
}
+ xprt_put(xprt);
}

/*
@@ -339,7 +339,7 @@ struct rpc_rqst *xprt_lookup_bc_request(struct rpc_xprt *xprt, __be32 xid)
spin_unlock(&xprt->bc_pa_lock);
if (new) {
if (req != new)
- xprt_free_bc_rqst(new);
+ xprt_free_allocation(new);
break;
} else if (req)
break;
@@ -368,6 +368,7 @@ void xprt_complete_bc_request(struct rpc_rqst *req, uint32_t copied)
set_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);

dprintk("RPC: add callback request to list\n");
+ xprt_get(xprt);
spin_lock(&bc_serv->sv_cb_lock);
list_add(&req->rq_bc_list, &bc_serv->sv_cb_list);
wake_up(&bc_serv->sv_cb_waitq);
--
2.21.0