Re: [PATCH 4.19 078/361] nvmet-rdma: use a private workqueue for delete

Bart Van Assche
2018-11-12T01:27:09Z

On 11/11/18 2:17 PM, Greg Kroah-Hartman wrote:
> 4.19-stable review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Sagi Grimberg <sagi@grimberg.me>
>
> [ Upstream commit 2acf70ade79d26b97611a8df52eb22aa33814cd4 ]
>
> Queue deletion is done asynchronous when the last reference on the queue
> is dropped. Thus, in order to make sure we don't over allocate under a
> connect/disconnect storm, we let queue deletion complete before making
> forward progress.
>
> However, given that we flush the system_wq from rdma_cm context which
> runs from a workqueue context, we can have a circular locking complaint
> [1]. Fix that by using a private workqueue for queue deletion.

Hi Greg,

You may want to drop this patch. A bug was discovered in this patch a
few days ago. I think not backporting this patch is better than
backporting it. See also the discussion at
http://lists.infradead.org/pipermail/linux-nvme/2018-November/020766.html.
A quote from that e-mail thread: "I think we need to revert 2acf70a
("nvmet-rdma: use a private workqueue for delete") altogether because it
never made any difference..".

Bart.