Re: [PATCH v2 1/3] lightnvm: missing nvm_lock acquire

["Matias Bjørling" <m@bjorling.me>]

On 11/27/2015 05:09 AM, Wenwei Tao wrote:
> To avoid race conditions, traverse dev, media manager,
> and targeet lists and also register, unregister entries
> to/from them, should be always under the nvm_lock control.
>
> Signed-off-by: Wenwei Tao <ww.tao0320@gmail.com>
> ---
>   drivers/lightnvm/core.c | 73 +++++++++++++++++++++++++------------------------
>   1 file changed, 38 insertions(+), 35 deletions(-)
>
> diff --git a/drivers/lightnvm/core.c b/drivers/lightnvm/core.c
> index 5178645..071a3e4 100644
> --- a/drivers/lightnvm/core.c
> +++ b/drivers/lightnvm/core.c
> @@ -123,6 +123,24 @@ void nvm_unregister_mgr(struct nvmm_type *mt)
>   }
>   EXPORT_SYMBOL(nvm_unregister_mgr);
>
> +/* register with device with a supported manager */
> +static int register_mgr(struct nvm_dev *dev)
> +{
> +	struct nvmm_type *mt;
> +	int ret = 0;
> +
> +	list_for_each_entry(mt, &nvm_mgrs, list) {
> +		ret = mt->register_mgr(dev);
> +		if (ret > 0) {
> +			dev->mt = mt;
> +			break; /* successfully initialized */
> +		}
> +	}
> +	if (!ret)
> +		pr_info("nvm: no compatible nvm manager found.\n");
> +	return ret;
> +}
> +
>   static struct nvm_dev *nvm_find_nvm_dev(const char *name)
>   {
>   	struct nvm_dev *dev;
> @@ -221,7 +239,6 @@ static void nvm_free(struct nvm_dev *dev)
>
>   static int nvm_init(struct nvm_dev *dev)
>   {
> -	struct nvmm_type *mt;
>   	int ret = -EINVAL;
>
>   	if (!dev->q || !dev->ops)
> @@ -251,22 +268,13 @@ static int nvm_init(struct nvm_dev *dev)
>   		pr_err("nvm: could not initialize core structures.\n");
>   		goto err;
>   	}
> -
> -	/* register with device with a supported manager */
> -	list_for_each_entry(mt, &nvm_mgrs, list) {
> -		ret = mt->register_mgr(dev);
> -		if (ret < 0)
> -			goto err; /* initialization failed */
> -		if (ret > 0) {
> -			dev->mt = mt;
> -			break; /* successfully initialized */
> -		}
> -	}
> -
> -	if (!ret) {
> -		pr_info("nvm: no compatible manager found.\n");
> +	down_write(&nvm_lock);
> +	ret = register_mgr(dev);
> +	up_write(&nvm_lock);
> +	if (ret < 0)
> +		goto err;
> +	if (!ret)
>   		return 0;
> -	}
>
>   	pr_info("nvm: registered %s [%u/%u/%u/%u/%u/%u]\n",
>   			dev->name, dev->sec_per_pg, dev->nr_planes,
> @@ -335,18 +343,18 @@ EXPORT_SYMBOL(nvm_register);
>
>   void nvm_unregister(char *disk_name)
>   {
> +	down_write(&nvm_lock);
>   	struct nvm_dev *dev = nvm_find_nvm_dev(disk_name);
>
>   	if (!dev) {
>   		pr_err("nvm: could not find device %s to unregister\n",
>   								disk_name);
> +		up_write(&nvm_lock);
>   		return;
>   	}
>
> -	down_write(&nvm_lock);
>   	list_del(&dev->devices);
>   	up_write(&nvm_lock);
> -
>   	nvm_exit(dev);
>   	kfree(dev);
>   }
> @@ -361,38 +369,30 @@ static int nvm_create_target(struct nvm_dev *dev,
>   {
>   	struct nvm_ioctl_create_simple *s = &create->conf.s;
>   	struct request_queue *tqueue;
> -	struct nvmm_type *mt;
>   	struct gendisk *tdisk;
>   	struct nvm_tgt_type *tt;
>   	struct nvm_target *t;
>   	void *targetdata;
>   	int ret = 0;
>
> +	down_write(&nvm_lock);
>   	if (!dev->mt) {
> -		/* register with device with a supported NVM manager */
> -		list_for_each_entry(mt, &nvm_mgrs, list) {
> -			ret = mt->register_mgr(dev);
> -			if (ret < 0)
> -				return ret; /* initialization failed */
> -			if (ret > 0) {
> -				dev->mt = mt;
> -				break; /* successfully initialized */
> -			}
> -		}
> -
> -		if (!ret) {
> -			pr_info("nvm: no compatible nvm manager found.\n");
> -			return -ENODEV;
> +		ret = register_mgr(dev);
> +		if (!ret)
> +			ret = -ENODEV;
> +		if (ret < 0) {
> +			up_write(&nvm_lock);
> +			return ret;
>   		}
>   	}
>
>   	tt = nvm_find_target_type(create->tgttype);
>   	if (!tt) {
>   		pr_err("nvm: target type %s not found\n", create->tgttype);
> +		up_write(&nvm_lock);
>   		return -EINVAL;
>   	}
>
> -	down_write(&nvm_lock);
>   	list_for_each_entry(t, &dev->online_targets, list) {
>   		if (!strcmp(create->tgtname, t->disk->disk_name)) {
>   			pr_err("nvm: target name already exists.\n");
> @@ -475,8 +475,9 @@ static int __nvm_configure_create(struct nvm_ioctl_create *create)
>   {
>   	struct nvm_dev *dev;
>   	struct nvm_ioctl_create_simple *s;
> -
> +	down_write(&nvm_lock);
>   	dev = nvm_find_nvm_dev(create->dev);
> +	up_write(&nvm_lock);
>   	if (!dev) {
>   		pr_err("nvm: device not found\n");
>   		return -EINVAL;
> @@ -535,7 +536,9 @@ static int nvm_configure_show(const char *val)
>   		return -EINVAL;
>   	}
>
> +	down_write(&nvm_lock);
>   	dev = nvm_find_nvm_dev(devname);
> +	up_write(&nvm_lock);
>   	if (!dev) {
>   		pr_err("nvm: device not found\n");
>   		return -EINVAL;
>

Thanks Wei. I applied the previous version of the patch.

You can see the patches I have queued for upstream in the for-next at 
https://github.com/OpenChannelSSD/linux/commits/for-next