Re: [PATCH 1/1] nvme: introduce generic per-namespace chardev

[Kanchan Joshi <joshiiitr@gmail.com>]

On Thu, Mar 25, 2021 at 6:08 PM Minwoo Im <minwoo.im.dev@gmail.com> wrote:
>
> Userspace has not been allowed to I/O to device that's failed to
> be initialized.  This patch introduces generic per-namespace character
> device to allow userspace to I/O regardless the block device is there or
> not.
>
> The chardev naming convention will exactly be the same with the existing
> blkdev's one.  nvme_set_generic_ns_name() introduced in this patch may
> look like a duplication of nvme_set_disk_name(), but it's not allowing
> controller path specific.  It just for per-namespace path specific.  So,
> the naming will be:
>
>         - /dev/nvme-generic-XnY
>
> It also supports multipath which means it will not expose chardev for
> the hidden namespace blkdevs (e.g., nvmeXcYnZ).  If
> /dev/nvme-generic-XnY is created for the ns_head, then I/O request will
> be routed to the controller-specified path by the iopolicy in the
> subsystem.
>
> This can be controlled by the module parameter `generic_ns` which is
> turned on by default.
>
> Signed-off-by: Minwoo Im <minwoo.im.dev@gmail.com>
> Signed-off-by: Javier González <javier.gonz@samsung.com>
> ---
>  drivers/nvme/host/core.c      | 170 +++++++++++++++++++++++++++++++++-
>  drivers/nvme/host/multipath.c |  17 ++++
>  drivers/nvme/host/nvme.h      |  25 +++++
>  3 files changed, 209 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index c371db47de3c..7dc0e216524b 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -61,6 +61,10 @@ static bool streams;
>  module_param(streams, bool, 0644);
>  MODULE_PARM_DESC(streams, "turn on support for Streams write directives");
>
> +static bool generic_ns = true;
> +module_param(generic_ns, bool, 0644);
> +MODULE_PARM_DESC(generic_ns, "support generic namespace character device");
> +
>  /*
>   * nvme_wq - hosts nvme related works that are not reset or delete
>   * nvme_reset_wq - hosts nvme reset works
> @@ -85,8 +89,11 @@ static LIST_HEAD(nvme_subsystems);
>  static DEFINE_MUTEX(nvme_subsystems_lock);
>
>  static DEFINE_IDA(nvme_instance_ida);
> +static DEFINE_IDA(nvme_generic_ns_minor_ida);
>  static dev_t nvme_ctrl_base_chr_devt;
> +static dev_t nvme_generic_ns_devt;
>  static struct class *nvme_class;
> +static struct class *nvme_generic_ns_class;
>  static struct class *nvme_subsys_class;
>
>  static void nvme_put_subsystem(struct nvme_subsystem *subsys);
> @@ -542,6 +549,7 @@ static void nvme_free_ns_head(struct kref *ref)
>         struct nvme_ns_head *head =
>                 container_of(ref, struct nvme_ns_head, ref);
>
> +       cdev_device_del(&head->generic_ns->cdev, &head->generic_ns->device);
>         nvme_mpath_remove_disk(head);
>         ida_simple_remove(&head->subsys->ns_ida, head->instance);
>         cleanup_srcu_struct(&head->srcu);
> @@ -3784,6 +3792,126 @@ static int __nvme_check_ids(struct nvme_subsystem *subsys,
>         return 0;
>  }
>
> +#ifdef CONFIG_NVME_MULTIPATH
> +static int nvme_generic_ns_open(struct inode *inode, struct file *file)
> +{
> +       struct nvme_generic_ns *generic_ns = container_of(inode->i_cdev,
> +                       struct nvme_generic_ns, cdev);
> +
> +       if (!generic_ns->head->disk)
> +               return -ENODEV;
> +
> +       file->private_data = generic_ns;
> +       return nvme_ns_head_open(generic_ns->head->disk->part0, file->f_mode);
> +}
> +
> +static int nvme_generic_ns_release(struct inode *inode, struct file *file)
> +{
> +       struct nvme_generic_ns *generic_ns = container_of(inode->i_cdev,
> +                       struct nvme_generic_ns, cdev);
> +
> +       nvme_ns_head_release(generic_ns->head->disk, file->f_mode);
> +
> +       return 0;
> +}
> +
> +static long nvme_generic_ns_ioctl(struct file *file, unsigned int cmd,
> +               unsigned long arg)
> +{
> +       struct nvme_generic_ns *generic_ns = file->private_data;
> +
> +       return nvme_ioctl(generic_ns->head->disk->part0, file->f_mode, cmd, arg);
> +}
> +#else
> +static int nvme_generic_ns_open(struct inode *inode, struct file *file)
> +{
> +       struct nvme_generic_ns *generic_ns = container_of(inode->i_cdev,
> +                       struct nvme_generic_ns, cdev);
> +
> +       if (!generic_ns->ns)
> +               return -ENODEV;
> +
> +       file->private_data = generic_ns;
> +       return nvme_open(generic_ns->ns->disk->part0, file->f_mode);
> +}
> +
> +static int nvme_generic_ns_release(struct inode *inode, struct file *file)
> +{
> +       struct nvme_generic_ns *generic_ns = container_of(inode->i_cdev,
> +                       struct nvme_generic_ns, cdev);
> +
> +       nvme_release(generic_ns->ns->disk, file->f_mode);
> +
> +       return 0;
> +}
> +
> +static long nvme_generic_ns_ioctl(struct file *file, unsigned int cmd,
> +               unsigned long arg)
> +{
> +       struct nvme_generic_ns *generic_ns = file->private_data;
> +
> +       return nvme_ioctl(generic_ns->ns->disk->part0, file->f_mode, cmd, arg);
> +}
> +#endif
> +
> +static const struct file_operations nvme_generic_ns_fops = {
> +       .owner          = THIS_MODULE,
> +       .open           = nvme_generic_ns_open,
> +       .release        = nvme_generic_ns_release,
> +       .unlocked_ioctl = nvme_generic_ns_ioctl,
> +       .compat_ioctl   = compat_ptr_ioctl,
> +};
> +
> +static int nvme_alloc_generic_ns(struct nvme_ctrl *ctrl,
> +               struct nvme_ns_head *head, struct nvme_ns *ns)
> +{
> +       struct nvme_generic_ns *generic_ns;
> +       char name[DISK_NAME_LEN];
> +       int minor;
> +       int ret;
> +
> +       generic_ns = kzalloc_node(sizeof(*generic_ns), GFP_KERNEL,
> +                       ctrl->numa_node);
> +       if (!generic_ns)
> +               return -ENOMEM;
> +
> +       ret = ida_simple_get(&nvme_generic_ns_minor_ida, 0, 0, GFP_KERNEL);
> +       if (ret < 0)
> +               goto free_ns;
> +       minor = ret;
> +
> +       device_initialize(&generic_ns->device);
> +       generic_ns->device.devt = MKDEV(MAJOR(nvme_generic_ns_devt), minor);
> +       generic_ns->device.class = nvme_generic_ns_class;
> +       generic_ns->device.parent = ctrl->device;
> +       dev_set_drvdata(&generic_ns->device, generic_ns);
> +
> +       nvme_set_generic_ns_name(name, head, ctrl);
> +       ret = dev_set_name(&generic_ns->device, "%s", name);
> +       if (ret)
> +               goto put_ida;
> +
> +       cdev_init(&generic_ns->cdev, &nvme_generic_ns_fops);
> +       generic_ns->cdev.owner = ctrl->ops->module;
> +
> +       ret = cdev_device_add(&generic_ns->cdev, &generic_ns->device);
> +       if (ret)
> +               goto free_kobj;
> +
> +       head->generic_ns = generic_ns;
> +       generic_ns->head = head;
> +       generic_ns->ns = ns;
> +       return 0;
> +
> +free_kobj:
> +       kfree_const(generic_ns->device.kobj.name);
> +put_ida:
> +       ida_simple_remove(&nvme_generic_ns_minor_ida, minor);
> +free_ns:
> +       kfree(generic_ns);
> +       return ret;
> +}
> +
>  static struct nvme_ns_head *nvme_alloc_ns_head(struct nvme_ctrl *ctrl,
>                 unsigned nsid, struct nvme_ns_ids *ids)
>  {
> @@ -3862,6 +3990,13 @@ static int nvme_init_ns_head(struct nvme_ns *ns, unsigned nsid,
>                         goto out_unlock;
>                 }
>                 head->shared = is_shared;
> +
> +               if (generic_ns && nvme_alloc_generic_ns(ctrl, head, ns)) {
> +                       dev_err(ctrl->device,
> +                               "Failed to initialize generic namespace %d\n",
> +                               nsid);
> +                       goto out_put_ns_head;
> +               }
>         } else {
>                 ret = -EINVAL;
>                 if (!is_shared || !head->shared) {
> @@ -3963,8 +4098,17 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid,
>         memcpy(disk->disk_name, disk_name, DISK_NAME_LEN);
>         ns->disk = disk;
>
> -       if (nvme_update_ns_info(ns, id))
> -               goto out_put_disk;
> +       /*
> +        * If the namespace update fails in a graceful manner, hide the block
> +        * device, but still allow for the generic namespae device to be
> +        * craeted.
> +        */
> +       if (nvme_update_ns_info(ns, id)) {
> +               if (generic_ns)
> +                       ns->disk->flags |= GENHD_FL_HIDDEN;
> +               else
> +                       goto out_put_disk;
> +       }
>
>         if ((ctrl->quirks & NVME_QUIRK_LIGHTNVM) && id->vs[0] == 0x1) {
>                 if (nvme_nvm_register(ns, disk_name, node)) {
> @@ -3983,6 +4127,7 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid,
>
>         nvme_mpath_add_disk(ns, id);
>         nvme_fault_inject_init(&ns->fault_inject, ns->disk->disk_name);
> +
>         kfree(id);
>
>         return;
> @@ -4802,13 +4947,31 @@ static int __init nvme_core_init(void)
>         }
>         nvme_class->dev_uevent = nvme_class_uevent;
>
> +       if (!generic_ns) return 0;

This will suppress creation of nvme_subsys_class when generic_ns
parameter is set as 0.

> +       result = alloc_chrdev_region(&nvme_generic_ns_devt, 0,
> +                       NVME_MINORS, "nvme-generic-ns");
> +       if (result < 0)
> +               goto destroy_class;
> +
>         nvme_subsys_class = class_create(THIS_MODULE, "nvme-subsystem");
>         if (IS_ERR(nvme_subsys_class)) {
>                 result = PTR_ERR(nvme_subsys_class);
> -               goto destroy_class;
> +               goto unregister_generic_ns;
>         }
> +
> +       nvme_generic_ns_class = class_create(THIS_MODULE, "nvme-generic-ns");
> +       if (IS_ERR(nvme_generic_ns_class)) {
> +               result = PTR_ERR(nvme_subsys_class);
> +               goto destroy_subsys_class;
> +       }
> +
>         return 0;
>
> +destroy_subsys_class:
> +       class_destroy(nvme_subsys_class);
> +unregister_generic_ns:
> +       unregister_chrdev_region(nvme_generic_ns_devt, NVME_MINORS);
>  destroy_class:
>         class_destroy(nvme_class);
>  unregister_chrdev:
> @@ -4827,6 +4990,7 @@ static void __exit nvme_core_exit(void)
>  {
>         class_destroy(nvme_subsys_class);
>         class_destroy(nvme_class);
> +       unregister_chrdev_region(nvme_generic_ns_devt, NVME_MINORS);
>         unregister_chrdev_region(nvme_ctrl_base_chr_devt, NVME_MINORS);
>         destroy_workqueue(nvme_delete_wq);
>         destroy_workqueue(nvme_reset_wq);

The "nvme-generic-ns" class has not been destroyed here.

-- 
Kanchan

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