staging: lustre: ptlrpc: Early replies need to honor at_max

When determining whether an early reply can be sent the server will
calculate the new deadline based on an offset from the request
arrival time. However, when actually setting the new deadline
the server offsets the current time. This can result in deadlines
being extended more than at_max seconds past the request arrival
time. Instead, the server should offset the arrival time when updating
its request timeout.

When a client receives an early reply it doesn't know the server side
arrival time so we use the original sent time as an approximation.

Signed-off-by: Chris Horn <hornc@cray.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-4578
Reviewed-on: http://review.whamcloud.com/9100
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Reviewed-by: Christopher J. Morrone <chris.morrone.llnl@gmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 13 insertions, 5 deletions

diff --git a/drivers/staging/lustre/lustre/ptlrpc/service.c b/drivers/staging/lustre/lustre/ptlrpc/service.c
index 4788c4940c2a..30d8b72cdf74 100644
--- a/drivers/staging/lustre/lustre/ptlrpc/service.c
+++ b/drivers/staging/lustre/lustre/ptlrpc/service.c
@@ -1005,13 +1005,16 @@ ptlrpc_at_remove_timed(struct ptlrpc_request *req)
 	array->paa_count--;
 }
 
+/*
+ * Attempt to extend the request deadline by sending an early reply to the
+ * client.
+ */
 static int ptlrpc_at_send_early_reply(struct ptlrpc_request *req)
 {
 	struct ptlrpc_service_part *svcpt = req->rq_rqbd->rqbd_svcpt;
 	struct ptlrpc_request *reqcopy;
 	struct lustre_msg *reqmsg;
 	long olddl = req->rq_deadline - ktime_get_real_seconds();
-	time64_t newdl;
 	int rc;
 
 	/* deadline is when the client expects us to reply, margin is the
@@ -1039,8 +1042,13 @@ static int ptlrpc_at_send_early_reply(struct ptlrpc_request *req)
 		return -ENOSYS;
 	}
 
-	/* Fake our processing time into the future to ask the clients
-	 * for some extra amount of time
+	/*
+	 * We want to extend the request deadline by at_extra seconds,
+	 * so we set our service estimate to reflect how much time has
+	 * passed since this request arrived plus an additional
+	 * at_extra seconds. The client will calculate the new deadline
+	 * based on this service estimate (plus some additional time to
+	 * account for network latency). See ptlrpc_at_recv_early_reply
 	 */
 	at_measured(&svcpt->scp_at_estimate, at_extra +
 		    ktime_get_real_seconds() - req->rq_arrival_time.tv_sec);
@@ -1056,7 +1064,6 @@ static int ptlrpc_at_send_early_reply(struct ptlrpc_request *req)
 			  ktime_get_real_seconds());
 		return -ETIMEDOUT;
 	}
-	newdl = ktime_get_real_seconds() + at_get(&svcpt->scp_at_estimate);
 
 	reqcopy = ptlrpc_request_cache_alloc(GFP_NOFS);
 	if (!reqcopy)
@@ -1110,7 +1117,8 @@ static int ptlrpc_at_send_early_reply(struct ptlrpc_request *req)
 
 	if (!rc) {
 		/* Adjust our own deadline to what we told the client */
-		req->rq_deadline = newdl;
+		req->rq_deadline = req->rq_arrival_time.tv_sec +
+				   at_get(&svcpt->scp_at_estimate);
 		req->rq_early_count++; /* number sent, server side */
 	} else {
 		DEBUG_REQ(D_ERROR, req, "Early reply send failed %d", rc);