# Re: \[PATCH\] md/linear: rcu\_dereference outside read-lock section

- From: NeilBrown \<hidden\>
- Date: 2012-08-13 23:52:53 
- List: linux-raid
- Page: https://ratatoskr.run/linux-raid/2012/08/3907792
- Thread: https://ratatoskr.run/linux-raid/2012/08/3907621/t.md

```text
On Tue, 14 Aug 2012 01:08:12 +0400 Denis Efremov [ref]
wrote:

> According to the comment in linear_stop function
> rcu_dereference in linear_start and linear_stop functions
> occurs under reconfig_mutex. The patch represents this
> agreement in code and prevents lockdep complaint.
> 
> Found by Linux Driver Verification project (linuxtesting.org)
> 
> Signed-off-by: Denis Efremov <redacted>
> ---
>  drivers/md/linear.c |    7 +++++--
>  1 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/md/linear.c b/drivers/md/linear.c
> index fa211d8..093f3e4 100644
> --- a/drivers/md/linear.c
> +++ b/drivers/md/linear.c
> @@ -244,7 +244,8 @@ static int linear_add(struct mddev *mddev, struct md_rdev *rdev)
>  	if (!newconf)
>  		return -ENOMEM;
>  
> -	oldconf = rcu_dereference(mddev->private);
> +	oldconf = rcu_dereference_protected(mddev->private,
> +					    lockdep_is_held(&mddev->reconfig_mutex));
>  	mddev->raid_disks++;
>  	rcu_assign_pointer(mddev->private, newconf);
>  	md_set_array_sectors(mddev, linear_size(mddev, 0, 0));
> @@ -256,7 +257,9 @@ static int linear_add(struct mddev *mddev, struct md_rdev *rdev)
>  
>  static int linear_stop (struct mddev *mddev)
>  {
> -	struct linear_conf *conf = mddev->private;
> +	struct linear_conf *conf =
> +		rcu_dereference_protected(mddev->private,
> +					  lockdep_is_held(&mddev->reconfig_mutex));
>  
>  	/*
>  	 * We do not require rcu protection here since


Applied, thanks.

NeilBrown
```

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