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

Does this indicate the window since nvme_start_queues() in nvme_reset_work(),
that is, just after the queues are unquiesced again?

If v2 is required in the future, how about to mention the specific function to
that it would be much more easier to track the issue.

> 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;

... and how about to comment that the below is because of nvme timeout handler
as explained in another email (if v2 would be sent) so that it is not required
to query for "online_queues" with cscope :)

> +		if (!dev->online_queues)
> +			break;
> +		msleep(5);
> +	}
> +
> +	return frozen;
> +}
> +

Thank you very much!

Dongli Zhang