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| author | Chuck Lever <chuck.lever@oracle.com> | 2014-05-28 10:34:57 -0400 |
|---|---|---|
| committer | Anna Schumaker <Anna.Schumaker@Netapp.com> | 2014-06-04 08:56:52 -0400 |
| commit | e7ce710a8802351bd4118c5d6136c1d850f67cf9 (patch) | |
| tree | f9c4a23768955b85ee7d6cf519906004c86aff61 /net/sunrpc/xprtrdma/transport.c | |
| parent | 4f4cf5ad6fc1b16dc8dc9d750bb80b35eba5e98d (diff) | |
| download | lwn-e7ce710a8802351bd4118c5d6136c1d850f67cf9.tar.gz lwn-e7ce710a8802351bd4118c5d6136c1d850f67cf9.zip | |
xprtrdma: Avoid deadlock when credit window is reset
Update the cwnd while processing the server's reply. Otherwise the
next task on the xprt_sending queue is still subject to the old
credit window. Currently, no task is awoken if the old congestion
window is still exceeded, even if the new window is larger, and a
deadlock results.
This is an issue during a transport reconnect. Servers don't
normally shrink the credit window, but the client does reset it to
1 when reconnecting so the server can safely grow it again.
As a minor optimization, remove the hack of grabbing the initial
cwnd size (which happens to be RPC_CWNDSCALE) and using that value
as the congestion scaling factor. The scaling value is invariant,
and we are better off without the multiplication operation.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Diffstat (limited to 'net/sunrpc/xprtrdma/transport.c')
| -rw-r--r-- | net/sunrpc/xprtrdma/transport.c | 19 |
1 files changed, 1 insertions, 18 deletions
diff --git a/net/sunrpc/xprtrdma/transport.c b/net/sunrpc/xprtrdma/transport.c index 6b84d7d59e18..187894b4c33f 100644 --- a/net/sunrpc/xprtrdma/transport.c +++ b/net/sunrpc/xprtrdma/transport.c @@ -448,23 +448,6 @@ xprt_rdma_connect(struct rpc_xprt *xprt, struct rpc_task *task) } } -static int -xprt_rdma_reserve_xprt(struct rpc_xprt *xprt, struct rpc_task *task) -{ - struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt); - int credits = atomic_read(&r_xprt->rx_buf.rb_credits); - - /* == RPC_CWNDSCALE @ init, but *after* setup */ - if (r_xprt->rx_buf.rb_cwndscale == 0UL) { - r_xprt->rx_buf.rb_cwndscale = xprt->cwnd; - dprintk("RPC: %s: cwndscale %lu\n", __func__, - r_xprt->rx_buf.rb_cwndscale); - BUG_ON(r_xprt->rx_buf.rb_cwndscale <= 0); - } - xprt->cwnd = credits * r_xprt->rx_buf.rb_cwndscale; - return xprt_reserve_xprt_cong(xprt, task); -} - /* * The RDMA allocate/free functions need the task structure as a place * to hide the struct rpcrdma_req, which is necessary for the actual send/recv @@ -686,7 +669,7 @@ static void xprt_rdma_print_stats(struct rpc_xprt *xprt, struct seq_file *seq) */ static struct rpc_xprt_ops xprt_rdma_procs = { - .reserve_xprt = xprt_rdma_reserve_xprt, + .reserve_xprt = xprt_reserve_xprt_cong, .release_xprt = xprt_release_xprt_cong, /* sunrpc/xprt.c */ .alloc_slot = xprt_alloc_slot, .release_request = xprt_release_rqst_cong, /* ditto */ |