Re: [PATCH 3/3] nvme-pci: make nvme reset more reliable

[Dongli Zhang <dongli.zhang@oracle.com>]

On 5/20/20 4:56 AM, Ming Lei wrote:
> During waiting for in-flight IO completion in reset handler, timeout
> or controller failure still may happen, then the controller is deleted
> and all inflight IOs are failed. This way is too violent.
> 
> Improve the reset handling by replacing nvme_wait_freeze with query
> & check controller. If all ns queues are frozen, the controller is reset
> successfully, otherwise check and see if the controller has been disabled.
> If yes, break from the current recovery and schedule a fresh new reset.
> 
> This way avoids to failing IO & removing controller unnecessarily.
> 
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Sagi Grimberg <sagi@grimberg.me>
> Cc: Keith Busch <kbusch@kernel.org>
> Cc: Max Gurtovoy <maxg@mellanox.com>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>  drivers/nvme/host/pci.c | 37 ++++++++++++++++++++++++++++++-------
>  1 file changed, 30 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
> index ce0d1e79467a..b5aeed33a634 100644
> --- a/drivers/nvme/host/pci.c
> +++ b/drivers/nvme/host/pci.c
> @@ -24,6 +24,7 @@
>  #include <linux/io-64-nonatomic-lo-hi.h>
>  #include <linux/sed-opal.h>
>  #include <linux/pci-p2pdma.h>
> +#include <linux/delay.h>
>  
>  #include "trace.h"
>  #include "nvme.h"
> @@ -1235,9 +1236,6 @@ static enum blk_eh_timer_return nvme_timeout(struct request *req, bool reserved)
>  	 * shutdown, so we return BLK_EH_DONE.
>  	 */
>  	switch (dev->ctrl.state) {
> -	case NVME_CTRL_CONNECTING:
> -		nvme_change_ctrl_state(&dev->ctrl, NVME_CTRL_DELETING);
> -		/* fall through */
>  	case NVME_CTRL_DELETING:
>  		dev_warn_ratelimited(dev->ctrl.device,
>  			 "I/O %d QID %d timeout, disable controller\n",
> @@ -2393,7 +2391,8 @@ static void nvme_dev_disable(struct nvme_dev *dev, bool shutdown)
>  		u32 csts = readl(dev->bar + NVME_REG_CSTS);
>  
>  		if (dev->ctrl.state == NVME_CTRL_LIVE ||
> -		    dev->ctrl.state == NVME_CTRL_RESETTING) {
> +		    dev->ctrl.state == NVME_CTRL_RESETTING ||
> +		    dev->ctrl.state == NVME_CTRL_CONNECTING) {
>  			freeze = true;
>  			nvme_start_freeze(&dev->ctrl);
>  		}
> @@ -2504,12 +2503,29 @@ static void nvme_remove_dead_ctrl(struct nvme_dev *dev)
>  		nvme_put_ctrl(&dev->ctrl);
>  }
>  
> +static bool nvme_wait_freeze_and_check(struct nvme_dev *dev)
> +{
> +	bool frozen;
> +
> +	while (true) {
> +		frozen = nvme_frozen(&dev->ctrl);
> +		if (frozen)
> +			break;
> +		if (!dev->online_queues)
> +			break;
> +		msleep(5);
> +	}
> +
> +	return frozen;
> +}
> +
>  static void nvme_reset_work(struct work_struct *work)
>  {
>  	struct nvme_dev *dev =
>  		container_of(work, struct nvme_dev, ctrl.reset_work);
>  	bool was_suspend = !!(dev->ctrl.ctrl_config & NVME_CC_SHN_NORMAL);
>  	int result;
> +	bool reset_done = true;
>  
>  	if (WARN_ON(dev->ctrl.state != NVME_CTRL_RESETTING)) {
>  		result = -ENODEV;
> @@ -2606,8 +2622,9 @@ static void nvme_reset_work(struct work_struct *work)
>  		nvme_free_tagset(dev);
>  	} else {
>  		nvme_start_queues(&dev->ctrl);
> -		nvme_wait_freeze(&dev->ctrl);
> -		nvme_dev_add(dev);
> +		reset_done = nvme_wait_freeze_and_check(dev);

Once we arrive at here, it indicates "dev->online_queues >= 2".

2601         if (dev->online_queues < 2) {
2602                 dev_warn(dev->ctrl.device, "IO queues not created\n");
2603                 nvme_kill_queues(&dev->ctrl);
2604                 nvme_remove_namespaces(&dev->ctrl);
2605                 nvme_free_tagset(dev);
2606         } else {
2607                 nvme_start_queues(&dev->ctrl);
2608                 nvme_wait_freeze(&dev->ctrl);
2609                 nvme_dev_add(dev);
2610                 nvme_unfreeze(&dev->ctrl);
2611         }

Is there any reason to check "if (!dev->online_queues)" in
nvme_wait_freeze_and_check()?

Thank you very much!

Dongli Zhang




> +		if (reset_done)
> +			nvme_dev_add(dev);
>  		nvme_unfreeze(&dev->ctrl);
>  	}
>  
> @@ -2622,7 +2639,13 @@ static void nvme_reset_work(struct work_struct *work)
>  		goto out;
>  	}
>  
> -	nvme_start_ctrl(&dev->ctrl);
> +	/* New error happens during reset, so schedule a new reset */
> +	if (!reset_done) {
> +		dev_warn(dev->ctrl.device, "new error during reset\n");
> +		nvme_reset_ctrl(&dev->ctrl);
> +	} else {
> +		nvme_start_ctrl(&dev->ctrl);
> +	}
>  	return;
>  
>   out_unlock:
>