[PATCH v2] nvme-rdma: fix possible hang when issuing commands during ctrl removal

[Sagi Grimberg]

nvme_rdma_queue_is_ready() fails requests in case a queue is not
LIVE. If the controller is in RECONNECTING state, we might be in
this state for a long time (until we successfully reconnect) and
we are better off with failing the request fast. Otherwise, we
fail with BLK_STS_RESOURCE to have the block layer try again
soon.

In case we are removing the controller when the admin queue
is not LIVE, we will terminate the request with BLK_STS_RESOURCE
but it happens before we call blk_mq_start_request() so the
request timeout never expires, and the queue will never get
back to LIVE (because we are removing the controller). This
causes the removal operation to block infinitly [1].

Thus, if we are removing (state DELETING), and the queue is
not LIVE, we need to fail the request permanently as there is
no chance for it to ever complete successfully.

[1]
--
sysrq: SysRq : Show Blocked State
  task                        PC stack   pid father
kworker/u66:2   D    0   440      2 0x80000000
Workqueue: nvme-wq nvme_rdma_del_ctrl_work [nvme_rdma]
Call Trace:
 __schedule+0x3e9/0xb00
 schedule+0x40/0x90
 schedule_timeout+0x221/0x580
 io_schedule_timeout+0x1e/0x50
 wait_for_completion_io_timeout+0x118/0x180
 blk_execute_rq+0x86/0xc0
 __nvme_submit_sync_cmd+0x89/0xf0
 nvmf_reg_write32+0x4b/0x90 [nvme_fabrics]
 nvme_shutdown_ctrl+0x41/0xe0
 nvme_rdma_shutdown_ctrl+0xca/0xd0 [nvme_rdma]
 nvme_rdma_remove_ctrl+0x2b/0x40 [nvme_rdma]
 nvme_rdma_del_ctrl_work+0x25/0x30 [nvme_rdma]
 process_one_work+0x1fd/0x630
 worker_thread+0x1db/0x3b0
 kthread+0x11e/0x150
 ret_from_fork+0x27/0x40
01              D    0  2868   2862 0x00000000
Call Trace:
 __schedule+0x3e9/0xb00
 schedule+0x40/0x90
 schedule_timeout+0x260/0x580
 wait_for_completion+0x108/0x170
 flush_work+0x1e0/0x270
 nvme_rdma_del_ctrl+0x5a/0x80 [nvme_rdma]
 nvme_sysfs_delete+0x2a/0x40
 dev_attr_store+0x18/0x30
 sysfs_kf_write+0x45/0x60
 kernfs_fop_write+0x124/0x1c0
 __vfs_write+0x28/0x150
 vfs_write+0xc7/0x1b0
 SyS_write+0x49/0xa0
 entry_SYSCALL_64_fastpath+0x18/0xad
--

Reported-by: Bart Van Assche <bart.vanassche at wdc.com>
Signed-off-by: Sagi Grimberg <sagi at grimberg.me>
---
Changes from v1:
- squashed to ctrl state conditions in nvme_rdma_queue_is_ready

 drivers/nvme/host/rdma.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/nvme/host/rdma.c b/drivers/nvme/host/rdma.c
index 8a4a4a5836a8..fd26bcb9e6b7 100644
--- a/drivers/nvme/host/rdma.c
+++ b/drivers/nvme/host/rdma.c
@@ -1386,12 +1386,15 @@ nvme_rdma_queue_is_ready(struct nvme_rdma_queue *queue, struct request *rq)
 			/*
 			 * reconnecting state means transport disruption, which
 			 * can take a long time and even might fail permanently,
-			 * so we can't let incoming I/O be requeued forever.
-			 * fail it fast to allow upper layers a chance to
-			 * failover.
+			 * fail fast to give upper layers a chance to failover.
+			 * deleting state means that the ctrl will never accept
+			 * commands again, fail it permanently.
 			 */
-			if (queue->ctrl->ctrl.state == NVME_CTRL_RECONNECTING)
+			if (queue->ctrl->ctrl.state == NVME_CTRL_RECONNECTING ||
+			    queue->ctrl->ctrl.state == NVME_CTRL_DELETING) {
+				nvme_req(rq)->status = NVME_SC_ABORT_REQ;
 				return BLK_STS_IOERR;
+			}
 			return BLK_STS_RESOURCE; /* try again later */
 		}
 	}
-- 
2.7.4