On Tue, Jun 13, 2023 at 04:13:42PM +0300, Sagi Grimberg wrote: > > > For block layer freeze/unfreeze APIs, the caller is required to call the > > two in strict pair, so most of users simply call them from same context, > > and everything works just fine. > > > > For NVMe, the two are done from different contexts, this way has caused > > all kinds of IO hang issue, such as: > > > > 1) When io queue connect fails, this controller is deleted without being > > marked as DEAD. Upper layer may wait forever in __bio_queue_enter(), because > > in del_gendisk(), disk won't be marked as DEAD unless bdev sync & invalidate > > returns. If any writeback IO waits in __bio_queue_enter(), IO deadlock is > > caused. Reported from Yi Zhang. > > > > 2) error recovering vs. namespace deletiong, if any IO originated from > > scan work is waited in __bio_queue_enter(), flushing scan work hangs for > > ever in nvme_remove_namespaces() because controller is left as frozen > > when error recovery is interrupted by controller removal. Reported from > > Chunguang. > > > > Fix the issue by calling the two in same context just when reset is done > > and not starting freeze from beginning of error recovery. Not only IO hang > > is solved, correctness of freeze & unfreeze is respected. > > > > And this way is correct because quiesce is enough for driver to handle > > error recovery. The only difference is where to wait during error recovery. > > With this way, IO is just queued in block layer queue instead of > > __bio_queue_enter(), finally waiting for completion is done in upper > > layer. Either way, IO can't move on during error recovery. > > > > Reported-by: Chunguang Xu <brookxu.cn@xxxxxxxxx> > > Closes: https://lore.kernel.org/linux-nvme/cover.1685350577.git.chunguang.xu@xxxxxxxxxx/ > > Reported-by: Yi Zhang <yi.zhang@xxxxxxxxxx> > > Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx> > > --- > > drivers/nvme/host/core.c | 4 +--- > > drivers/nvme/host/pci.c | 8 +++++--- > > drivers/nvme/host/rdma.c | 3 ++- > > drivers/nvme/host/tcp.c | 3 ++- > > 4 files changed, 10 insertions(+), 8 deletions(-) > > > > diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c > > index 4ef5eaecaa75..d5d9b6f6ec74 100644 > > --- a/drivers/nvme/host/core.c > > +++ b/drivers/nvme/host/core.c > > @@ -4707,10 +4707,8 @@ void nvme_remove_namespaces(struct nvme_ctrl *ctrl) > > * removing the namespaces' disks; fail all the queues now to avoid > > * potentially having to clean up the failed sync later. > > */ > > - if (ctrl->state == NVME_CTRL_DEAD) { > > + if (ctrl->state == NVME_CTRL_DEAD) > > nvme_mark_namespaces_dead(ctrl); > > - nvme_unquiesce_io_queues(ctrl); > > - } > > Shouldn't this be in the next patch? Not sure what > this helps in this patch? It is not clearly documented > in the commit msg. oops, good catch, will fix it in V2. > > > /* this is a no-op when called from the controller reset handler */ > > nvme_change_ctrl_state(ctrl, NVME_CTRL_DELETING_NOIO); > > diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c > > index 492f319ebdf3..5d775b76baca 100644 > > --- a/drivers/nvme/host/pci.c > > +++ b/drivers/nvme/host/pci.c > > @@ -2578,14 +2578,15 @@ static void nvme_dev_disable(struct nvme_dev *dev, bool shutdown) > > dead = nvme_pci_ctrl_is_dead(dev); > > if (dev->ctrl.state == NVME_CTRL_LIVE || > > dev->ctrl.state == NVME_CTRL_RESETTING) { > > - if (pci_is_enabled(pdev)) > > - nvme_start_freeze(&dev->ctrl); > > /* > > * Give the controller a chance to complete all entered requests > > * if doing a safe shutdown. > > */ > > - if (!dead && shutdown) > > + if (!dead && shutdown & pci_is_enabled(pdev)) { > > + nvme_start_freeze(&dev->ctrl); > > nvme_wait_freeze_timeout(&dev->ctrl, NVME_IO_TIMEOUT); > > + nvme_unfreeze(&dev->ctrl); > > + } > > I'd split out the pci portion, it is not related to the reported issue, Yes. > and it is structured differently than the fabrics transports (as for now > at least). The above change needs to be done in this patch given the same pattern needs to remove the above 'if (pci_is_enabled(pdev)) nvme_start_freeze()'. > > > } > > nvme_quiesce_io_queues(&dev->ctrl); > > @@ -2740,6 +2741,7 @@ static void nvme_reset_work(struct work_struct *work) > > * controller around but remove all namespaces. > > */ > > if (dev->online_queues > 1) { > > + nvme_start_freeze(&dev->ctrl); > > nvme_unquiesce_io_queues(&dev->ctrl); > > nvme_wait_freeze(&dev->ctrl); > > nvme_pci_update_nr_queues(dev); > > diff --git a/drivers/nvme/host/rdma.c b/drivers/nvme/host/rdma.c > > index 0eb79696fb73..354cce8853c1 100644 > > --- a/drivers/nvme/host/rdma.c > > +++ b/drivers/nvme/host/rdma.c > > @@ -918,6 +918,7 @@ static int nvme_rdma_configure_io_queues(struct nvme_rdma_ctrl *ctrl, bool new) > > goto out_cleanup_tagset; > > if (!new) { > > + nvme_start_freeze(&ctrl->ctrl); > > nvme_unquiesce_io_queues(&ctrl->ctrl); > > if (!nvme_wait_freeze_timeout(&ctrl->ctrl, NVME_IO_TIMEOUT)) { > > /* > > @@ -926,6 +927,7 @@ static int nvme_rdma_configure_io_queues(struct nvme_rdma_ctrl *ctrl, bool new) > > * to be safe. > > */ > > ret = -ENODEV; > > + nvme_unfreeze(&ctrl->ctrl); > > What does this unfreeze designed to do? It is for undoing the previous nvme_start_freeze. Thanks, Ming
