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

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

On 5/20/20 10:10 AM, Dongli Zhang wrote:
> 
> 
> 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()?
> 

I think you meant another nvme_dev_disable() during reset?

Sorry for the misunderstanding in previous email.

Dongli Zhang