On Wed, Sep 04, 2019 at 10:07:12AM -0600, Logan Gunthorpe wrote: > Yes, I agree, we can't solve the mismatch problem in the general case: > with sequences of hot plug events there will always be a case that > mismatches. I just think we can do better in the simple common default case.
This may be something where udev can help us. I might be able to find some time to look at that, but not today. > > Can we just ensure there is never a matching controller then? This > > patch will accomplish that and simpler than wrapping the instance in a > > refcount'ed object: > > > > http://lists.infradead.org/pipermail/linux-nvme/2019-May/024142.html > > I don't really like that idea. It reduces the confusion caused by > mismatching numbers, but causes the controller to never match the > namespace, which is also confusing but in a different way. > > I like the nvme_instance idea. It's not going to be perfect but it has > some nice properties: the subsystem will try to match the controller's > instance whenever possible, but in cases where it doesn't, the instance > number of the subsystem will never be the same as an existing controller. > > I'll see if I can work up a quick patch set and see what people think. How about this: we have the subsys copy the controller's instance, and the nvme_free_ctrl() doesn't release it if its subsys matches? --- diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c index 14c0bfb55615..8a8279ece5ee 100644 --- a/drivers/nvme/host/core.c +++ b/drivers/nvme/host/core.c @@ -81,7 +81,6 @@ EXPORT_SYMBOL_GPL(nvme_reset_wq); struct workqueue_struct *nvme_delete_wq; EXPORT_SYMBOL_GPL(nvme_delete_wq); -static DEFINE_IDA(nvme_subsystems_ida); static LIST_HEAD(nvme_subsystems); static DEFINE_MUTEX(nvme_subsystems_lock); @@ -2344,7 +2343,8 @@ static void nvme_release_subsystem(struct device *dev) struct nvme_subsystem *subsys = container_of(dev, struct nvme_subsystem, dev); - ida_simple_remove(&nvme_subsystems_ida, subsys->instance); + if (subsys->instance >= 0) + ida_simple_remove(&nvme_instance_ida, subsys->instance); kfree(subsys); } @@ -2473,12 +2473,8 @@ static int nvme_init_subsystem(struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id) subsys = kzalloc(sizeof(*subsys), GFP_KERNEL); if (!subsys) return -ENOMEM; - ret = ida_simple_get(&nvme_subsystems_ida, 0, 0, GFP_KERNEL); - if (ret < 0) { - kfree(subsys); - return ret; - } - subsys->instance = ret; + + subsys->instance = -1; mutex_init(&subsys->lock); kref_init(&subsys->ref); INIT_LIST_HEAD(&subsys->ctrls); @@ -2497,7 +2493,7 @@ static int nvme_init_subsystem(struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id) subsys->dev.class = nvme_subsys_class; subsys->dev.release = nvme_release_subsystem; subsys->dev.groups = nvme_subsys_attrs_groups; - dev_set_name(&subsys->dev, "nvme-subsys%d", subsys->instance); + dev_set_name(&subsys->dev, "nvme-subsys%d", ctrl->instance); device_initialize(&subsys->dev); mutex_lock(&nvme_subsystems_lock); @@ -2528,6 +2524,8 @@ static int nvme_init_subsystem(struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id) goto out_put_subsystem; } + if (!found) + subsys->instance = ctrl->instance; ctrl->subsys = subsys; list_add_tail(&ctrl->subsys_entry, &subsys->ctrls); mutex_unlock(&nvme_subsystems_lock); @@ -3803,7 +3801,9 @@ static void nvme_free_ctrl(struct device *dev) container_of(dev, struct nvme_ctrl, ctrl_device); struct nvme_subsystem *subsys = ctrl->subsys; - ida_simple_remove(&nvme_instance_ida, ctrl->instance); + if (subsys && ctrl->instance != subsys->instance) + ida_simple_remove(&nvme_instance_ida, ctrl->instance); + kfree(ctrl->effects); nvme_mpath_uninit(ctrl); __free_page(ctrl->discard_page); @@ -4085,7 +4085,6 @@ static int __init nvme_core_init(void) static void __exit nvme_core_exit(void) { - ida_destroy(&nvme_subsystems_ida); class_destroy(nvme_subsys_class); class_destroy(nvme_class); unregister_chrdev_region(nvme_chr_devt, NVME_MINORS); --
