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SubjectRe: [PATCH V3 1/2] nvme: split resetting state into reset_prepate and resetting
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> Currently, the ctrl->state will be changed to NVME_CTRL_RESETTING
> before queue the reset work. This is not so strict. There could be
> a big gap before the reset_work callback is invoked. In addition,
> there is some disable work in the reset_work callback, strictly
> speaking, not part of reset work, and could lead to some confusion.
>
> This patch splits the NVME_CTRL_RESETTING into NVME_CTRL_RESET_PREPARE
> and NVME_CTRL_RESETTING. Before queue the reset work, changes state
> to NVME_CTRL_RESET_PREPARE, after disable work completes, changes
> state to NVME_CTRL_RESETTING.

What guarantees that nvme_timeout will do the right thing? If it
is relying on the fact that nvme-pci sets the state to RESETTING
only _after_ quiescing the requests queues it needs to be documented
as its a real delicate dependency.



>
> Suggested-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com>
> ---
> drivers/nvme/host/core.c | 17 +++++++++++++++--
> drivers/nvme/host/fc.c | 2 ++
> drivers/nvme/host/nvme.h | 1 +
> drivers/nvme/host/pci.c | 28 ++++++++++++++++++++++------
> drivers/nvme/host/rdma.c | 8 ++++++++
> drivers/nvme/target/loop.c | 5 +++++
> 6 files changed, 53 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index 1e46e60..106a437 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -87,7 +87,7 @@ static __le32 nvme_get_log_dw10(u8 lid, size_t size)
>
> int nvme_reset_ctrl(struct nvme_ctrl *ctrl)
> {
> - if (!nvme_change_ctrl_state(ctrl, NVME_CTRL_RESETTING))
> + if (!nvme_change_ctrl_state(ctrl, NVME_CTRL_RESET_PREPARE))
> return -EBUSY;
> if (!queue_work(nvme_wq, &ctrl->reset_work))
> return -EBUSY;
> @@ -243,7 +243,7 @@ bool nvme_change_ctrl_state(struct nvme_ctrl *ctrl,
> break;
> }
> break;
> - case NVME_CTRL_RESETTING:
> + case NVME_CTRL_RESET_PREPARE:
> switch (old_state) {
> case NVME_CTRL_NEW:
> case NVME_CTRL_LIVE:
> @@ -253,10 +253,21 @@ bool nvme_change_ctrl_state(struct nvme_ctrl *ctrl,
> break;
> }
> break;
> +
> + case NVME_CTRL_RESETTING:
> + switch (old_state) {
> + case NVME_CTRL_RESET_PREPARE:
> + changed = true;
> + /* FALLTHRU */
> + default:
> + break;
> + }
> + break;
> case NVME_CTRL_RECONNECTING:
> switch (old_state) {
> case NVME_CTRL_LIVE:
> case NVME_CTRL_RESETTING:
> + case NVME_CTRL_RESET_PREPARE:
> changed = true;
> /* FALLTHRU */
> default:
> @@ -267,6 +278,7 @@ bool nvme_change_ctrl_state(struct nvme_ctrl *ctrl,
> switch (old_state) {
> case NVME_CTRL_LIVE:
> case NVME_CTRL_RESETTING:
> + case NVME_CTRL_RESET_PREPARE:
> case NVME_CTRL_RECONNECTING:
> changed = true;
> /* FALLTHRU */
> @@ -2603,6 +2615,7 @@ static ssize_t nvme_sysfs_show_state(struct device *dev,
> [NVME_CTRL_NEW] = "new",
> [NVME_CTRL_LIVE] = "live",
> [NVME_CTRL_RESETTING] = "resetting",
> + [NVME_CTRL_RESET_PREPARE] = "reset-prepare",
> [NVME_CTRL_RECONNECTING]= "reconnecting",
> [NVME_CTRL_DELETING] = "deleting",
> [NVME_CTRL_DEAD] = "dead",
> diff --git a/drivers/nvme/host/fc.c b/drivers/nvme/host/fc.c
> index 794e66e..516c1ea 100644
> --- a/drivers/nvme/host/fc.c
> +++ b/drivers/nvme/host/fc.c
> @@ -547,6 +547,7 @@ nvme_fc_resume_controller(struct nvme_fc_ctrl *ctrl)
> break;
>
> case NVME_CTRL_RESETTING:
> + case NVME_CTRL_RESET_PREPARE:
> /*
> * Controller is already in the process of terminating the
> * association. No need to do anything further. The reconnect
> @@ -790,6 +791,7 @@ nvme_fc_ctrl_connectivity_loss(struct nvme_fc_ctrl *ctrl)
> break;
>
> case NVME_CTRL_RESETTING:
> + case NVME_CTRL_RESET_PREPARE:
> /*
> * Controller is already in the process of terminating the
> * association. No need to do anything further. The reconnect

James, can you take a look at this?

> diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
> index f5800c3..e477c35 100644
> --- a/drivers/nvme/host/pci.c
> +++ b/drivers/nvme/host/pci.c
> @@ -1141,8 +1141,13 @@ static bool nvme_should_reset(struct nvme_dev *dev, u32 csts)
> bool nssro = dev->subsystem && (csts & NVME_CSTS_NSSRO);
>
> /* If there is a reset ongoing, we shouldn't reset again. */
> - if (dev->ctrl.state == NVME_CTRL_RESETTING)
> + switch (dev->ctrl.state) {
> + case NVME_CTRL_RESETTING:
> + case NVME_CTRL_RESET_PREPARE:
> return false;
> + default:
> + break;
> + }

Isn't the indentation off? also in other places...

> @@ -2292,7 +2303,7 @@ static void nvme_reset_work(struct work_struct *work)
> bool was_suspend = !!(dev->ctrl.ctrl_config & NVME_CC_SHN_NORMAL);
> int result = -ENODEV;
>
> - if (WARN_ON(dev->ctrl.state != NVME_CTRL_RESETTING))
> + if (WARN_ON(dev->ctrl.state != NVME_CTRL_RESET_PREPARE))
> goto out;
>
> /*
> @@ -2302,6 +2313,11 @@ static void nvme_reset_work(struct work_struct *work)
> if (dev->ctrl.ctrl_config & NVME_CC_ENABLE)
> nvme_dev_disable(dev, false);
>
> + if (!nvme_change_ctrl_state(&dev->ctrl, NVME_CTRL_RESETTING)) {
> + WARN_ON_ONCE(dev->ctrl.state != NVME_CTRL_DELETING);
> + goto out;
> + }
> +

This needs documentation on _why_ here.

> - nvme_change_ctrl_state(&dev->ctrl, NVME_CTRL_RESETTING);
> + nvme_change_ctrl_state(&dev->ctrl, NVME_CTRL_RESET_PREPARE);
> dev_info(dev->ctrl.device, "pci function %s\n", dev_name(&pdev->dev));

Can you rebase on top of my commit:
4caff8fc19f1 nvme-pci: don't open-code nvme_reset_ctrl

> diff --git a/drivers/nvme/host/rdma.c b/drivers/nvme/host/rdma.c
> index 37af565..8ae073e 100644
> --- a/drivers/nvme/host/rdma.c
> +++ b/drivers/nvme/host/rdma.c
> @@ -1753,6 +1753,14 @@ static void nvme_rdma_reset_ctrl_work(struct work_struct *work)
> nvme_stop_ctrl(&ctrl->ctrl);
> nvme_rdma_shutdown_ctrl(ctrl, false);
>
> + changed = nvme_change_ctrl_state(&ctrl->ctrl,
> + NVME_CTRL_RESET_PREPARE);
> + if (!changed) {
> + /* state change failure is ok if we're in DELETING state */
> + WARN_ON_ONCE(ctrl->ctrl.state != NVME_CTRL_DELETING);
> + return;
> + }
> +

setting RESET_PREPARE here??

Also, the error recovery code is mutually excluded from reset_work
by trying to set the same state which is protected by the ctrl state
machine, so a similar change is needed there.

So in order not to break rdma ctrl reset (again) please look at:
bcdacf7fc3d8 nvme-rdma: fix concurrent reset and reconnect

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