From: Sagi Grimberg sagi@grimberg.me
[ Upstream commit 657f1975e9d9c880fa13030e88ba6cc84964f1db ]
The deadlock combines 4 flows in parallel: - ns scanning (triggered from reconnect) - request timeout - ANA update (triggered from reconnect) - I/O coming into the mpath device
(1) ns scanning triggers disk revalidation -> update disk info -> freeze queue -> but blocked, due to (2)
(2) timeout handler reference the g_usage_counter - > but blocks in the transport .timeout() handler, due to (3)
(3) the transport timeout handler (indirectly) calls nvme_stop_queue() -> which takes the (down_read) namespaces_rwsem - > but blocks, due to (4)
(4) ANA update takes the (down_write) namespaces_rwsem -> calls nvme_mpath_set_live() -> which synchronize the ns_head srcu (see commit 504db087aacc) -> but blocks, due to (5)
(5) I/O came into nvme_mpath_make_request -> took srcu_read_lock -> direct_make_request > blk_queue_enter -> but blocked, due to (1)
==> the request queue is under freeze -> deadlock.
The fix is making ANA update take a read lock as the namespaces list is not manipulated, it is just the ns and ns->head that are being updated (which is protected with the ns->head lock).
Fixes: 0d0b660f214dc ("nvme: add ANA support") Signed-off-by: Sagi Grimberg sagi@grimberg.me Reviewed-by: Keith Busch kbusch@kernel.org Reviewed-by: Hannes Reinecke hare@suse.de Signed-off-by: Christoph Hellwig hch@lst.de Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/nvme/host/multipath.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c index aed6354cb2717..56caddeabb5e5 100644 --- a/drivers/nvme/host/multipath.c +++ b/drivers/nvme/host/multipath.c @@ -510,7 +510,7 @@ static int nvme_update_ana_state(struct nvme_ctrl *ctrl, if (!nr_nsids) return 0;
- down_write(&ctrl->namespaces_rwsem); + down_read(&ctrl->namespaces_rwsem); list_for_each_entry(ns, &ctrl->namespaces, list) { unsigned nsid = le32_to_cpu(desc->nsids[n]);
@@ -521,7 +521,7 @@ static int nvme_update_ana_state(struct nvme_ctrl *ctrl, if (++n == nr_nsids) break; } - up_write(&ctrl->namespaces_rwsem); + up_read(&ctrl->namespaces_rwsem); return 0; }