Re: [PATCH 7/8] nvme: use blk_mq_queue_tag_busy_iter

[jianchao.wang]

Hi James

On 3/16/19 12:33 AM, James Smart wrote:
> On 3/15/2019 1:57 AM, Jianchao Wang wrote:
>> blk_mq_tagset_busy_iter is not safe that it could get stale request
>> in tags->rqs[]. Use blk_mq_queue_tag_busy_iter here. A new helper
>> interface nvme_iterate_inflight_rqs is introduced to iterate
>> all of the ns under a ctrl.
>>
>> Signed-off-by: Jianchao Wang <jianchao.w.wang@xxxxxxxxxx>
>> ---
>> Â drivers/nvme/host/core.cÂÂ | 12 ++++++++++++
>> Â drivers/nvme/host/fc.cÂÂÂÂ | 12 ++++++------
>> Â drivers/nvme/host/nvme.hÂÂ |Â 2 ++
>> Â drivers/nvme/host/pci.cÂÂÂ |Â 5 +++--
>> Â drivers/nvme/host/rdma.cÂÂ |Â 6 +++---
>> Â drivers/nvme/host/tcp.cÂÂÂ |Â 5 +++--
>> Â drivers/nvme/target/loop.c |Â 6 +++---
>> Â 7 files changed, 32 insertions(+), 16 deletions(-)
>>
>> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
>> index 6a9dd68..5760fad 100644
>> --- a/drivers/nvme/host/core.c
>> +++ b/drivers/nvme/host/core.c
>> @@ -3816,6 +3816,18 @@ void nvme_start_queues(struct nvme_ctrl *ctrl)
>> Â }
>> Â EXPORT_SYMBOL_GPL(nvme_start_queues);
>> Â +void nvme_iterate_inflight_rqs(struct nvme_ctrl *ctrl,
>> +ÂÂÂÂÂÂÂ busy_iter_fn *fn, void *data)
>> +{
>> +ÂÂÂ struct nvme_ns *ns;
>> +
>> +ÂÂÂ down_read(&ctrl->namespaces_rwsem);
>> +ÂÂÂ list_for_each_entry(ns, &ctrl->namespaces, list)
>> +ÂÂÂÂÂÂÂ blk_mq_queue_tag_busy_iter(ns->queue, fn, data, true);
>> +ÂÂÂ up_read(&ctrl->namespaces_rwsem);
>> +}
>> +EXPORT_SYMBOL_GPL(nvme_iterate_inflight_rqs);
> 
> Hmm... so this aborts ios for namespaces. How about ios that aren't for a namespace but rather for the controller itself. For example, anything on the admin queue ? Rather critical for those ios be terminated as well.
> 

The blk_mq_tagset_busy_iter which is currently used by nvme is iterating the in-flight ios for the controller.
But due to blk_mq_tagset_busy_iter is not safe which is talked in the patch 0/8,
so change it to blk_mq_queue_busy_tag_iter which is for a namespace/request_queue.

Thanks
Jianchao