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author | Sagi Grimberg <sagi@grimberg.me> | 2020-04-02 19:34:54 +0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-04-29 17:31:12 +0300 |
commit | b15eafb3f928a6d4717d828701f15e1e8bf19da7 (patch) | |
tree | eb45b723bc1ae832546504c1a856dc04625fddd4 | |
parent | b9b57d4d67a454eae688400c5d4db183c609d85f (diff) | |
download | linux-b15eafb3f928a6d4717d828701f15e1e8bf19da7.tar.xz |
nvme: fix deadlock caused by ANA update wrong locking
[ 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>
-rw-r--r-- | drivers/nvme/host/multipath.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c index e8bc25aed44c..588864beabd8 100644 --- a/drivers/nvme/host/multipath.c +++ b/drivers/nvme/host/multipath.c @@ -402,7 +402,7 @@ 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]); @@ -413,7 +413,7 @@ 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; } |