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    Subject[PATCH] nvme: unquiesce the queue before cleaup it
    Date
    There is race between nvme_remove and nvme_reset_work that can
    lead to io hang.

    nvme_remove nvme_reset_work
    -> change state to DELETING
    -> fail to change state to LIVE
    -> nvme_remove_dead_ctrl
    -> nvme_dev_disable
    -> quiesce request_queue
    -> queue remove_work
    -> cancel_work_sync reset_work
    -> nvme_remove_namespaces
    -> splice ctrl->namespaces
    nvme_remove_dead_ctrl_work
    -> nvme_kill_queues
    -> nvme_ns_remove do nothing
    -> blk_cleanup_queue
    -> blk_freeze_queue
    Finally, the request_queue is quiesced state when wait freeze,
    we will get io hang here.

    To fix it, unquiesce the request_queue directly before nvme_ns_remove.
    We have spliced the ctrl->namespaces, so nobody could access them
    and quiesce the queue any more.

    Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com>
    ---
    drivers/nvme/host/core.c | 9 ++++++++-
    1 file changed, 8 insertions(+), 1 deletion(-)

    diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
    index 9df4f71..0e95082 100644
    --- a/drivers/nvme/host/core.c
    +++ b/drivers/nvme/host/core.c
    @@ -3249,8 +3249,15 @@ void nvme_remove_namespaces(struct nvme_ctrl *ctrl)
    list_splice_init(&ctrl->namespaces, &ns_list);
    up_write(&ctrl->namespaces_rwsem);

    - list_for_each_entry_safe(ns, next, &ns_list, list)
    + /*
    + * After splice the namespaces list from the ctrl->namespaces,
    + * nobody could get them anymore, let's unquiesce the request_queue
    + * forcibly to avoid io hang.
    + */
    + list_for_each_entry_safe(ns, next, &ns_list, list) {
    + blk_mq_unquiesce_queue(ns->queue);
    nvme_ns_remove(ns);
    + }
    }
    EXPORT_SYMBOL_GPL(nvme_remove_namespaces);

    --
    2.7.4
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