[PATCH v3 2/7] xprtrdma: Avoid 250 ms delay on backlog wakeup

[Chuck Lever <cel@kernel.org>]

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

Commit a721035477fb ("SUNRPC/xprt: async tasks mustn't block waiting
for memory") changed xprt_rdma_alloc_slot() to set tk_status to
-ENOMEM so that call_reserveresult() would sleep HZ/4 before
retrying.  That rationale applies to xprt_dynamic_alloc_slot(),
where an immediate retry under memory pressure wastes CPU, but not
to the RDMA backlog path: a task woken from the backlog has a slot
waiting for it, so the 250 ms rpc_delay adds latency without
benefit.

This also aligns the code with the existing kernel-doc for
xprt_rdma_alloc_slot(), which already documented %-EAGAIN.

Fixes: a721035477fb ("SUNRPC/xprt: async tasks mustn't block waiting for memory")
Signed-off-by: Chuck Lever <chuck.lever@oracle.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 9a8ce5df83ca..ca079439f9cc 100644
--- a/net/sunrpc/xprtrdma/transport.c
+++ b/net/sunrpc/xprtrdma/transport.c
@@ -510,7 +510,7 @@ xprt_rdma_alloc_slot(struct rpc_xprt *xprt, struct rpc_task *task)
 	return;
 
 out_sleep:
-	task->tk_status = -ENOMEM;
+	task->tk_status = -EAGAIN;
 	xprt_add_backlog(xprt, task);
 }
 
-- 
2.53.0