From 60bf8bf8815e6adea4c1d0423578c3b8000e2ec8 Mon Sep 17 00:00:00 2001 From: Sage Weil Date: Fri, 4 Mar 2011 12:24:28 -0800 Subject: [PATCH] libceph: fix msgr backoff With commit f363e45f we replaced a bunch of hacky workqueue mutual exclusion logic with the WQ_NON_REENTRANT flag. One pieces of fallout is that the exponential backoff breaks in certain cases: * con_work attempts to connect. * we get an immediate failure, and the socket state change handler queues immediate work. * con_work calls con_fault, we decide to back off, but can't queue delayed work. In this case, we add a BACKOFF bit to make con_work reschedule delayed work next time it runs (which should be immediately). Signed-off-by: Sage Weil --- include/linux/ceph/messenger.h | 1 + net/ceph/messenger.c | 30 ++++++++++++++++++++++++++++-- 2 files changed, 29 insertions(+), 2 deletions(-) diff --git a/include/linux/ceph/messenger.h b/include/linux/ceph/messenger.h index c3011be..eb31e10 100644 --- a/include/linux/ceph/messenger.h +++ b/include/linux/ceph/messenger.h @@ -123,6 +123,7 @@ struct ceph_msg_pos { #define SOCK_CLOSED 11 /* socket state changed to closed */ #define OPENING 13 /* open connection w/ (possibly new) peer */ #define DEAD 14 /* dead, about to kfree */ +#define BACKOFF 15 /* * A single connection with another host. diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c index 6bd5025..46fbc42 100644 --- a/net/ceph/messenger.c +++ b/net/ceph/messenger.c @@ -1949,6 +1949,19 @@ static void con_work(struct work_struct *work) work.work); mutex_lock(&con->mutex); + if (test_and_clear_bit(BACKOFF, &con->state)) { + dout("con_work %p backing off\n", con); + if (queue_delayed_work(ceph_msgr_wq, &con->work, + round_jiffies_relative(con->delay))) { + dout("con_work %p backoff %lu\n", con, con->delay); + mutex_unlock(&con->mutex); + return; + } else { + con->ops->put(con); + dout("con_work %p FAILED to back off %lu\n", con, + con->delay); + } + } if (test_bit(CLOSED, &con->state)) { /* e.g. if we are replaced */ dout("con_work CLOSED\n"); @@ -2017,11 +2030,24 @@ static void ceph_fault(struct ceph_connection *con) con->delay = BASE_DELAY_INTERVAL; else if (con->delay < MAX_DELAY_INTERVAL) con->delay *= 2; - dout("fault queueing %p delay %lu\n", con, con->delay); con->ops->get(con); if (queue_delayed_work(ceph_msgr_wq, &con->work, - round_jiffies_relative(con->delay)) == 0) + round_jiffies_relative(con->delay))) { + dout("fault queued %p delay %lu\n", con, con->delay); + } else { con->ops->put(con); + dout("fault failed to queue %p delay %lu, backoff\n", + con, con->delay); + /* + * In many cases we see a socket state change + * while con_work is running and end up + * queuing (non-delayed) work, such that we + * can't backoff with a delay. Set a flag so + * that when con_work restarts we schedule the + * delay then. + */ + set_bit(BACKOFF, &con->state); + } } out_unlock: -- 1.7.10.4