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

[Ming Lei <ming.lei@redhat.com>]

On Wed, May 20, 2020 at 10:10:47AM -0700, 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()?
> 

nvme_dev_disable() suspends all io queues and admin queue, so dev->online_queues
will become 0 after nvme_dev_disable() is run from timeout handler.


thanks,
Ming