SUNRPC: Enqueue swapper tagged RPCs at the head of the transmit queue

Avoid memory starvation by giving RPCs that are tagged with the
RPC_TASK_SWAPPER flag the highest priority.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index b03355ae7b16e577c32341b06291ac31ac32b0f6..d7585458dfe406898cb80dbdb2c9cae36cc69434 100644 (file)
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -1112,6 +1112,17 @@ xprt_request_enqueue_transmit(struct rpc_task *task)
                                INIT_LIST_HEAD(&req->rq_xmit2);
                                goto out;
                        }
+               } else if (RPC_IS_SWAPPER(task)) {
+                       list_for_each_entry(pos, &xprt->xmit_queue, rq_xmit) {
+                               if (pos->rq_cong || pos->rq_bytes_sent)
+                                       continue;
+                               if (RPC_IS_SWAPPER(pos->rq_task))
+                                       continue;
+                               /* Note: req is added _before_ pos */
+                               list_add_tail(&req->rq_xmit, &pos->rq_xmit);
+                               INIT_LIST_HEAD(&req->rq_xmit2);
+                               goto out;
+                       }
                } else {
                        list_for_each_entry(pos, &xprt->xmit_queue, rq_xmit) {
                                if (pos->rq_task->tk_owner != task->tk_owner)