linux-kernel - [PATCH AUTOSEL for 4.14 119/135] xprtrdma: Don't defer fencing an async RPC's chunks

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Date:   Thu, 7 Dec 2017 15:46:00 +0000
From:   alexander.levin@...izon.com
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Cc:     Chuck Lever <chuck.lever@...cle.com>,
        Anna Schumaker <Anna.Schumaker@...app.com>,
        alexander.levin@...izon.com
Subject: [PATCH AUTOSEL for 4.14 119/135] xprtrdma: Don't defer fencing an
 async RPC's chunks

From: Chuck Lever <chuck.lever@...cle.com>

[ Upstream commit 8f66b1a529047a972cb9602a919c53a95f3d7a2b ]

In current kernels, waiting in xprt_release appears to be safe to
do. I had erroneously believed that for ASYNC RPCs, waiting of any
kind in xprt_release->xprt_rdma_free would result in deadlock. I've
done injection testing and consulted with Trond to confirm that
waiting in the RPC release path is safe.

For the very few times where RPC resources haven't yet been released
earlier by the reply handler, it is safe to wait synchronously in
xprt_rdma_free for invalidation rather than defering it to MR
recovery.

Note: When the QP is error state, posting a LocalInvalidate should
flush and mark the MR as bad. There is no way the remote HCA can
access that MR via a QP in error state, so it is effectively already
inaccessible and thus safe for the Upper Layer to access. The next
time the MR is used it should be recognized and cleaned up properly
by frwr_op_map.

Signed-off-by: Chuck Lever <chuck.lever@...cle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@...app.com>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
---
 net/sunrpc/xprtrdma/transport.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sunrpc/xprtrdma/transport.c b/net/sunrpc/xprtrdma/transport.c
index c84e2b644e13..8cf5ccfe180d 100644
--- a/net/sunrpc/xprtrdma/transport.c
+++ b/net/sunrpc/xprtrdma/transport.c
@@ -686,7 +686,7 @@ xprt_rdma_free(struct rpc_task *task)
 	dprintk("RPC:       %s: called on 0x%p\n", __func__, req->rl_reply);

 	if (!list_empty(&req->rl_registered))
-		ia->ri_ops->ro_unmap_safe(r_xprt, req, !RPC_IS_ASYNC(task));
+		ia->ri_ops->ro_unmap_sync(r_xprt, &req->rl_registered);
 	rpcrdma_unmap_sges(ia, req);
 	rpcrdma_buffer_put(req);
 }
-- 
2.11.0