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Fri, 04 Sep 2026 16:04:50 -0700 (PDT) Date: Fri, 4 Sep 2026 16:04:48 -0700 From: Mohamed Khalfella To: Hannes Reinecke Cc: Justin Tee , Naresh Gottumukkala , Paul Ely , Chaitanya Kulkarni , Christoph Hellwig , Jens Axboe , Keith Busch , Sagi Grimberg , James Smart , Randy Jennings , Dhaval Giani , Aaron Dailey , linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 08/16] nvme: Implement cross-controller reset recovery Message-ID: <20260904230448.GD5552-mkhalfella@purestorage.com> References: <20260712022437.3743117-1-mkhalfella@purestorage.com> <20260712022437.3743117-9-mkhalfella@purestorage.com> <30475d09-bba2-460b-bf05-869f355ef106@suse.de> 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=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <30475d09-bba2-460b-bf05-869f355ef106@suse.de> On Mon 2026-07-13 09:04:14 +0200, Hannes Reinecke wrote: > On 7/12/26 4:23 AM, Mohamed Khalfella wrote: > > A host that has more than one path connecting to an nvme subsystem > > typically has an nvme controller associated with every path. This is > > mostly applicable to nvmeof. If one path goes down, inflight IOs on that > > path should not be retried immediately on another path because this > > could lead to data corruption as described in TP4129. TP8028 defines > > cross-controller reset mechanism that can be used by host to terminate > > IOs on the failed path using one of the remaining healthy paths. Only > > after IOs are terminated, or long enough time passes as defined by > > TP4129, inflight IOs should be retried on another path. Implement core > > cross-controller reset shared logic to be used by the transports. > > > > Signed-off-by: Mohamed Khalfella > > --- > > drivers/nvme/host/constants.c | 1 + > > drivers/nvme/host/core.c | 152 ++++++++++++++++++++++++++++++++++ > > drivers/nvme/host/nvme.h | 10 +++ > > 3 files changed, 163 insertions(+) > > > > diff --git a/drivers/nvme/host/constants.c b/drivers/nvme/host/constants.c > > index dc90df9e13a2..f679efd5110e 100644 > > --- a/drivers/nvme/host/constants.c > > +++ b/drivers/nvme/host/constants.c > > @@ -46,6 +46,7 @@ static const char * const nvme_admin_ops[] = { > > [nvme_admin_virtual_mgmt] = "Virtual Management", > > [nvme_admin_nvme_mi_send] = "NVMe Send MI", > > [nvme_admin_nvme_mi_recv] = "NVMe Receive MI", > > + [nvme_admin_cross_ctrl_reset] = "Cross Controller Reset", > > [nvme_admin_dbbuf] = "Doorbell Buffer Config", > > [nvme_admin_format_nvm] = "Format NVM", > > [nvme_admin_security_send] = "Security Send", > > diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c > > index 1ef4dc38f755..a1deffc3cc00 100644 > > --- a/drivers/nvme/host/core.c > > +++ b/drivers/nvme/host/core.c > > @@ -571,6 +571,157 @@ void nvme_cancel_admin_tagset(struct nvme_ctrl *ctrl) > > } > > EXPORT_SYMBOL_GPL(nvme_cancel_admin_tagset); > > > > +static struct nvme_ctrl *nvme_find_ctrl_ccr(struct nvme_ctrl *ictrl, > > + u32 min_cntlid) > > +{ > > + struct nvme_subsystem *subsys = ictrl->subsys; > > + struct nvme_ctrl *ctrl, *sctrl = NULL; > > + unsigned long flags; > > + int ccr_used; > > + > > + mutex_lock(&nvme_subsystems_lock); > > + list_for_each_entry(ctrl, &subsys->ctrls, subsys_entry) { > > + if (ctrl->cntlid < min_cntlid) > > + continue; > > + > > + spin_lock_irqsave(&ctrl->lock, flags); > > + if (nvme_ctrl_state(ctrl) != NVME_CTRL_LIVE) { > > + spin_unlock_irqrestore(&ctrl->lock, flags); > > + continue; > > + } > > + > > + ccr_used = atomic_inc_return(&ctrl->ccr_used); > > + if (ccr_used > ctrl->ccrl) { > > + atomic_dec(&ctrl->ccr_used); > > + spin_unlock_irqrestore(&ctrl->lock, flags); > > + continue; > > + } > > + > > + /* > > + * We got a good candidate source controller that is locked and > > + * LIVE. However, no guarantee ctrl will not be deleted after > > + * ctrl->lock is released. Get a ref of both ctrl and admin_q > > + * so they do not disappear until we are done with them. > > + */ > > + WARN_ON_ONCE(!blk_get_queue(ctrl->admin_q)); > > + nvme_get_ctrl(ctrl); > > + spin_unlock_irqrestore(&ctrl->lock, flags); > > + sctrl = ctrl; > > + break; > > + } > > + mutex_unlock(&nvme_subsystems_lock); > > + return sctrl; > > +} > > + > > +static void nvme_put_ctrl_ccr(struct nvme_ctrl *sctrl) > > +{ > > + atomic_dec(&sctrl->ccr_used); > > + blk_put_queue(sctrl->admin_q); > > + nvme_put_ctrl(sctrl); > > +} > > + > > +static int nvme_issue_wait_ccr(struct nvme_ctrl *sctrl, struct nvme_ctrl *ictrl, > > + unsigned long deadline) > > +{ > > + struct nvme_ccr_entry ccr = { }; > > + union nvme_result res = { 0 }; > > + struct nvme_command c = { }; > > + unsigned long flags, now, tmo = 0; > > + bool completed = false; > > + int ret = 0; > > + u32 result; > > + > > + init_completion(&ccr.complete); > > + ccr.ictrl = ictrl; > > + > > + spin_lock_irqsave(&sctrl->lock, flags); > > + list_add_tail(&ccr.list, &sctrl->ccr_list); > > + spin_unlock_irqrestore(&sctrl->lock, flags); > > + > > + c.ccr.opcode = nvme_admin_cross_ctrl_reset; > > + c.ccr.ciu = ictrl->ciu; > > + c.ccr.icid = cpu_to_le16(ictrl->cntlid); > > + c.ccr.cirn = cpu_to_le64(ictrl->cirn); > > + ret = __nvme_submit_sync_cmd(sctrl->admin_q, &c, &res, > > + NULL, 0, NVME_QID_ANY, 0); > > + if (ret) { > > + ret = -EIO; > > + goto out; > > + } > > + > > + result = le32_to_cpu(res.u32); > > + if (result & 0x01) /* Immediate Reset Successful */ > > + goto out; > > + > Do we care about any other values of 'result' ? No we do not. It just makes the code easier to read IMO. > > > + now = jiffies; > > + if (time_before(now, deadline)) > > + tmo = min_t(unsigned long, > > + secs_to_jiffies(ictrl->kato), deadline - now); > > + > > Ideally we would check the request timeout for the CCR to not > exceed 'deadline'. > But as __nvme_submit_sync_cmd() doesn't allow to specify the timeout > I guess it'll be good enough for now. > (And if all goes to plan the CCR command should've been aborted in that > case anyway). Right, as a follow up work I would like to extend __nvme_submit_sync_cmd() to take timeout, not in this patchset. > > > + if (!wait_for_completion_timeout(&ccr.complete, tmo)) { > > + ret = -ETIMEDOUT; > > + goto out; > > + } > > + > > + completed = true; > > + > > +out: > > + spin_lock_irqsave(&sctrl->lock, flags); > > + list_del(&ccr.list); > > + spin_unlock_irqrestore(&sctrl->lock, flags); > > + if (completed) { > > + if (ccr.ccrs == NVME_CCR_STATUS_SUCCESS) > > + return 0; > > + return -EREMOTEIO; > > + } > > + return ret; > > +} > > + > > +unsigned long nvme_fence_ctrl(struct nvme_ctrl *ictrl) > > +{ > > + unsigned long now, deadline, timeout; > > + struct nvme_ctrl *sctrl; > > + u32 min_cntlid = 0; > > + int ret; > > + > > + timeout = nvme_fence_timeout_ms(ictrl); > > + dev_info(ictrl->device, "attempting CCR, timeout %lums\n", timeout); > > + > > + now = jiffies; > > + deadline = jiffies + msecs_to_jiffies(timeout); > > + while (time_before(now, deadline)) { > > + sctrl = nvme_find_ctrl_ccr(ictrl, min_cntlid); > > + if (!sctrl) { > > + dev_dbg(ictrl->device, > > + "failed to find source controller\n"); > > + return deadline - now; > > + } > > + > > + ret = nvme_issue_wait_ccr(sctrl, ictrl, deadline); > > + if (!ret) { > > + dev_info(ictrl->device, "CCR succeeded using %s\n", > > + dev_name(sctrl->device)); > > + nvme_put_ctrl_ccr(sctrl); > > + return 0; > > + } > > + > > + /* > > + * CCR command or CCR operation failed on this path. > > + * Try another path as long as we have time. > > + */ > > + dev_err(ictrl->device, "CCR failed using %s, ret = %d\n", > > + dev_name(sctrl->device), ret); > > + min_cntlid = sctrl->cntlid + 1; > > + nvme_put_ctrl_ccr(sctrl); > > + now = jiffies; > > + } > > + > > + /* Fencing timed out call it done */ > > + dev_info(ictrl->device, "fencing timeout\n"); > > + return 0; > > +} > > +EXPORT_SYMBOL_GPL(nvme_fence_ctrl); > > + > > bool nvme_change_ctrl_state(struct nvme_ctrl *ctrl, > > enum nvme_ctrl_state new_state) > > { > > @@ -5205,6 +5356,7 @@ int nvme_init_ctrl(struct nvme_ctrl *ctrl, struct device *dev, > > > > mutex_init(&ctrl->scan_lock); > > INIT_LIST_HEAD(&ctrl->namespaces); > > + INIT_LIST_HEAD(&ctrl->ccr_list); > > xa_init(&ctrl->cels); > > ctrl->dev = dev; > > ctrl->ops = ops; > > diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h > > index e558a19781bd..90b989302e21 100644 > > --- a/drivers/nvme/host/nvme.h > > +++ b/drivers/nvme/host/nvme.h > > @@ -333,6 +333,13 @@ enum nvme_ctrl_flags { > > NVME_CTRL_FROZEN = 6, > > }; > > > > +struct nvme_ccr_entry { > > + struct list_head list; > > + struct completion complete; > > + struct nvme_ctrl *ictrl; > > + u8 ccrs; > > +}; > > + > > struct nvme_ctrl { > > bool comp_seen; > > bool identified; > > @@ -350,6 +357,7 @@ struct nvme_ctrl { > > struct blk_mq_tag_set *tagset; > > struct blk_mq_tag_set *admin_tagset; > > struct list_head namespaces; > > + struct list_head ccr_list; > > struct mutex namespaces_lock; > > struct srcu_struct srcu; > > struct device ctrl_device; > > @@ -393,6 +401,7 @@ struct nvme_ctrl { > > u16 sqsize; > > u32 max_namespaces; > > atomic_t abort_limit; > > + atomic_t ccr_used; > > u8 ccrl; > > u8 vwc; > > u32 vs; > > @@ -887,6 +896,7 @@ blk_status_t nvme_host_path_error(struct request *req); > > bool nvme_cancel_request(struct request *req, void *data); > > void nvme_cancel_tagset(struct nvme_ctrl *ctrl); > > void nvme_cancel_admin_tagset(struct nvme_ctrl *ctrl); > > +unsigned long nvme_fence_ctrl(struct nvme_ctrl *ctrl); > > bool nvme_change_ctrl_state(struct nvme_ctrl *ctrl, > > enum nvme_ctrl_state new_state); > > int nvme_disable_ctrl(struct nvme_ctrl *ctrl, bool shutdown); > > Otherwise looks good. > > Cheers, > > Hannes > -- > Dr. Hannes Reinecke Kernel Storage Architect > hare@suse.de +49 911 74053 688 > SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg > HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich