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Wed, 31 Dec 2025 16:27:24 -0800 (PST) Date: Wed, 31 Dec 2025 16:27:23 -0800 From: Mohamed Khalfella To: Sagi Grimberg Cc: Chaitanya Kulkarni , Christoph Hellwig , Jens Axboe , Keith Busch , Aaron Dailey , Randy Jennings , John Meneghini , Hannes Reinecke , linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 10/14] nvme-tcp: Use CCR to recover controller that hits an error Message-ID: <20260101002723.GS3864520-mkhalfella@purestorage.com> References: <20251126021250.2583630-1-mkhalfella@purestorage.com> <20251126021250.2583630-11-mkhalfella@purestorage.com> <5befc95c-b66a-4dd8-bb72-7cc6839c7c4b@grimberg.me> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5befc95c-b66a-4dd8-bb72-7cc6839c7c4b@grimberg.me> On Sat 2025-12-27 12:35:23 +0200, Sagi Grimberg wrote: > > > On 26/11/2025 4:11, Mohamed Khalfella wrote: > > An alive nvme controller that hits an error now will move to RECOVERING > > state instead of RESETTING state. In RECOVERING state ctrl->err_work > > will attempt to use cross-controller recovery to terminate inflight IOs > > on the controller. If CCR succeeds, then switch to RESETTING state and > > continue error recovery as usuall by tearing down controller and attempt > > reconnecting to target. If CCR fails, then the behavior of recovery > > depends on whether CQT is supported or not. If CQT is supported, switch > > to time-based recovery by holding inflight IOs until it is safe for them > > to be retried. If CQT is not supported proceed to retry requests > > immediately, as the code currently does. > > > > To support implementing time-based recovery turn ctrl->err_work into > > delayed work. Update nvme_tcp_timeout() to not complete inflight IOs > > while controller in RECOVERING state. > > > > Signed-off-by: Mohamed Khalfella > > --- > > drivers/nvme/host/tcp.c | 52 +++++++++++++++++++++++++++++++++++------ > > 1 file changed, 45 insertions(+), 7 deletions(-) > > > > diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c > > index 9a96df1a511c..ec9a713490a9 100644 > > --- a/drivers/nvme/host/tcp.c > > +++ b/drivers/nvme/host/tcp.c > > @@ -193,7 +193,7 @@ struct nvme_tcp_ctrl { > > struct sockaddr_storage src_addr; > > struct nvme_ctrl ctrl; > > > > - struct work_struct err_work; > > + struct delayed_work err_work; > > struct delayed_work connect_work; > > struct nvme_tcp_request async_req; > > u32 io_queues[HCTX_MAX_TYPES]; > > @@ -611,11 +611,12 @@ static void nvme_tcp_init_recv_ctx(struct nvme_tcp_queue *queue) > > > > static void nvme_tcp_error_recovery(struct nvme_ctrl *ctrl) > > { > > - if (!nvme_change_ctrl_state(ctrl, NVME_CTRL_RESETTING)) > > + if (!nvme_change_ctrl_state(ctrl, NVME_CTRL_RECOVERING) && > > + !nvme_change_ctrl_state(ctrl, NVME_CTRL_RESETTING)) > > This warrants an explanation. It is not clear at all why we should allow > two different > transitions to allow error recovery to start... The behavior of the ctrl->err_work depends on the controller state. We go to RECOVERING only if the controller is LIVE. Otherwise, we attempt to got to RESETTING. > > > return; > > > > dev_warn(ctrl->device, "starting error recovery\n"); > > - queue_work(nvme_reset_wq, &to_tcp_ctrl(ctrl)->err_work); > > + queue_delayed_work(nvme_reset_wq, &to_tcp_ctrl(ctrl)->err_work, 0); > > } > > > > static int nvme_tcp_process_nvme_cqe(struct nvme_tcp_queue *queue, > > @@ -2470,12 +2471,48 @@ static void nvme_tcp_reconnect_ctrl_work(struct work_struct *work) > > nvme_tcp_reconnect_or_remove(ctrl, ret); > > } > > > > +static int nvme_tcp_recover_ctrl(struct nvme_ctrl *ctrl) > > +{ > > + unsigned long rem; > > + > > + if (test_and_clear_bit(NVME_CTRL_RECOVERED, &ctrl->flags)) { > > + dev_info(ctrl->device, "completed time-based recovery\n"); > > + goto done; > > + } > > This is also not clear, why should we get here when NVME_CTRL_RECOVERED > is set? NVME_CTRL_RECOVERED flag is set before scheduling ctrl->err_work as delayed work. This is how how time-based recovery is implemented. We get here when ctrl->err_work runs for the second time, and at this point we know that it is safe to just reset the controller and cancel inflight requests. > > + > > + rem = nvme_recover_ctrl(ctrl); > > + if (!rem) > > + goto done; > > + > > + if (!ctrl->cqt) { > > + dev_info(ctrl->device, > > + "CCR failed, CQT not supported, skip time-based recovery\n"); > > + goto done; > > + } > > + > > + dev_info(ctrl->device, > > + "CCR failed, switch to time-based recovery, timeout = %ums\n", > > + jiffies_to_msecs(rem)); > > + set_bit(NVME_CTRL_RECOVERED, &ctrl->flags); > > + queue_delayed_work(nvme_reset_wq, &to_tcp_ctrl(ctrl)->err_work, rem); > > + return -EAGAIN; > > I don't think that reusing the same work to handle two completely > different things > is the right approach here. > > How about splitting to fence_work and err_work? That should eliminate > some of the > ctrl state inspections and simplify error recovery. > > > + > > +done: > > + nvme_end_ctrl_recovery(ctrl); > > + return 0; > > +} > > + > > static void nvme_tcp_error_recovery_work(struct work_struct *work) > > { > > - struct nvme_tcp_ctrl *tcp_ctrl = container_of(work, > > + struct nvme_tcp_ctrl *tcp_ctrl = container_of(to_delayed_work(work), > > struct nvme_tcp_ctrl, err_work); > > struct nvme_ctrl *ctrl = &tcp_ctrl->ctrl; > > > > + if (nvme_ctrl_state(ctrl) == NVME_CTRL_RECOVERING) { > > + if (nvme_tcp_recover_ctrl(ctrl)) > > + return; > > + } > > + > > Yea, I think we want to rework the current design. Good point. Splitting ctrl->fence_work simplifies things. The if condition above will be moved to fence_work. However, we will still need to reschedule ctrl->fence_work from within its self to implement time-based recovery. Is this good option? If not, and we prefer to drop NVME_CTRL_RECOVERED flag above and not reschedule ctrl->fence_work from within its self, then we can add another ctr->fenced_work. How about that?