diff options
| author | Sagi Grimberg <sagi@grimberg.me> | 2022-09-05 18:07:06 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-09-15 11:32:06 +0200 |
| commit | 6a2a344844625f3b6ffc704098c4eea5f926711b (patch) | |
| tree | c599537a76e9d9fc85b284d79944d9c91c62921f | |
| parent | 5914fa32ef1b7766fea933f9eed94ac5c00aa7ff (diff) | |
nvme-tcp: fix regression that causes sporadic requests to time out
[ Upstream commit 3770a42bb8ceb856877699257a43c0585a5d2996 ]
When we queue requests, we strive to batch as much as possible and also
signal the network stack that more data is about to be sent over a socket
with MSG_SENDPAGE_NOTLAST. This flag looks at the pending requests queued
as well as queue->more_requests that is derived from the block layer
last-in-batch indication.
We set more_request=true when we flush the request directly from
.queue_rq submission context (in nvme_tcp_send_all), however this is
wrongly assuming that no other requests may be queued during the
execution of nvme_tcp_send_all.
Due to this, a race condition may happen where:
1. request X is queued as !last-in-batch
2. request X submission context calls nvme_tcp_send_all directly
3. nvme_tcp_send_all is preempted and schedules to a different cpu
4. request Y is queued as last-in-batch
5. nvme_tcp_send_all context sends request X+Y, however signals for
both MSG_SENDPAGE_NOTLAST because queue->more_requests=true.
==> none of the requests is pushed down to the wire as the network
stack is waiting for more data, both requests timeout.
To fix this, we eliminate queue->more_requests and only rely on
the queue req_list and send_list to be not-empty.
Fixes: 122e5b9f3d37 ("nvme-tcp: optimize network stack with setting msg flags according to batch size")
Reported-by: Jonathan Nicklin <jnicklin@blockbridge.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Tested-by: Jonathan Nicklin <jnicklin@blockbridge.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | drivers/nvme/host/tcp.c | 5 |
1 files changed, 1 insertions, 4 deletions
diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c index 329aeb5fe951..57df87def8c3 100644 --- a/drivers/nvme/host/tcp.c +++ b/drivers/nvme/host/tcp.c @@ -118,7 +118,6 @@ struct nvme_tcp_queue { struct mutex send_mutex; struct llist_head req_list; struct list_head send_list; - bool more_requests; /* recv state */ void *pdu; @@ -314,7 +313,7 @@ static inline void nvme_tcp_send_all(struct nvme_tcp_queue *queue) static inline bool nvme_tcp_queue_more(struct nvme_tcp_queue *queue) { return !list_empty(&queue->send_list) || - !llist_empty(&queue->req_list) || queue->more_requests; + !llist_empty(&queue->req_list); } static inline void nvme_tcp_queue_request(struct nvme_tcp_request *req, @@ -333,9 +332,7 @@ static inline void nvme_tcp_queue_request(struct nvme_tcp_request *req, */ if (queue->io_cpu == raw_smp_processor_id() && sync && empty && mutex_trylock(&queue->send_mutex)) { - queue->more_requests = !last; nvme_tcp_send_all(queue); - queue->more_requests = false; mutex_unlock(&queue->send_mutex); } |