linux-kernel - Re: [PATCH] lightnvm: missing nvm

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Date:	Tue, 24 Nov 2015 19:36:29 +0100
From:	Matias <mb@...htnvm.io>
To:	Wenwei Tao <ww.tao0320@...il.com>
CC:	linux-kernel@...r.kernel.org, linux-block@...r.kernel.org
Subject: Re: [PATCH] lightnvm: missing nvm_lock acquire

On 11/24/2015 04:24 PM, 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@...il.com>
> ---
>   drivers/lightnvm/core.c | 19 +++++++++++++------
>   1 file changed, 13 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/lightnvm/core.c b/drivers/lightnvm/core.c
> index f659e60..39aec3a 100644
> --- a/drivers/lightnvm/core.c
> +++ b/drivers/lightnvm/core.c
> @@ -333,19 +333,19 @@ EXPORT_SYMBOL(nvm_register);
>
>   void nvm_unregister(char *disk_name)
>   {
> +	down_write(&nvm_lock);
>   	struct nvm_dev *dev = nvm_find_nvm_dev(disk_name);

In nvm_find_nvm_dev, can we instead replace it with 
list_for_each_entry_safe. Then we are sure that we won't hit a missing 
element, and will make the other cases significantly cleaner.

>
>   	if (!dev) {
>   		pr_err("nvm: could not find device %s to unregister\n",
>   								disk_name);
> +		up_write(&nvm_lock);
>   		return;
>   	}
>
> -	nvm_exit(dev);
> -
> -	down_write(&nvm_lock);
>   	list_del(&dev->devices);
>   	up_write(&nvm_lock);
> +	nvm_exit(dev);
>   }
>   EXPORT_SYMBOL(nvm_unregister);
>
> @@ -365,12 +365,15 @@ static int nvm_create_target(struct nvm_dev *dev,
>   	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) {

Same with this one?
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