From: Keith Busch kbusch@kernel.org
commit 70f437fb4395ad4d1d16fab9a1ad9fbc9fc0579b upstream.
Dispatching requests inline with the .queue_rq() call may block while holding the send_mutex. If the tcp io_work also happens to schedule, it may see the req_list is non-empty, leaving "pending" true and remaining in TASK_RUNNING. Since io_work is of higher scheduling priority, the .queue_rq task may not get a chance to run, blocking forward progress and leading to io timeouts.
Instead of checking for pending requests within io_work, let the queueing restart io_work outside the send_mutex lock if there is more work to be done.
Fixes: a0fdd1418007f ("nvme-tcp: rerun io_work if req_list is not empty") Reported-by: Samuel Jones sjones@kalrayinc.com Signed-off-by: Keith Busch kbusch@kernel.org Reviewed-by: Sagi Grimberg sagi@grimberg.me Signed-off-by: Christoph Hellwig hch@lst.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/nvme/host/tcp.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-)
--- a/drivers/nvme/host/tcp.c +++ b/drivers/nvme/host/tcp.c @@ -273,6 +273,12 @@ static inline void nvme_tcp_send_all(str } while (ret > 0); }
+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; +} + static inline void nvme_tcp_queue_request(struct nvme_tcp_request *req, bool sync, bool last) { @@ -293,9 +299,10 @@ static inline void nvme_tcp_queue_reques nvme_tcp_send_all(queue); queue->more_requests = false; mutex_unlock(&queue->send_mutex); - } else if (last) { - queue_work_on(queue->io_cpu, nvme_tcp_wq, &queue->io_work); } + + if (last && nvme_tcp_queue_more(queue)) + queue_work_on(queue->io_cpu, nvme_tcp_wq, &queue->io_work); }
static void nvme_tcp_process_req_list(struct nvme_tcp_queue *queue) @@ -890,12 +897,6 @@ done: read_unlock_bh(&sk->sk_callback_lock); }
-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; -} - static inline void nvme_tcp_done_send_req(struct nvme_tcp_queue *queue) { queue->request = NULL; @@ -1132,8 +1133,7 @@ static void nvme_tcp_io_work(struct work pending = true; else if (unlikely(result < 0)) break; - } else - pending = !llist_empty(&queue->req_list); + }
result = nvme_tcp_try_recv(queue); if (result > 0)