Re: [PATCH v3 32/51] resources: Split out __allocate_resource()

[Bjorn Helgaas <bhelgaas@google.com>]

On Mon, Jul 27, 2015 at 04:29:50PM -0700, Yinghai Lu wrote:
> It will not hold lock, so we could use it in other functions that
> hold the resource lock already.

What's the benefit of this patch?  Does it fix something?  Does it add some
functionality we need?
> 
> -v2: according to Linus, using "bool lock" as parameter
>      aka "conditionally take lock" is *wrong*.
> 
> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
> Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
> ---
>  kernel/resource.c | 70 +++++++++++++++++++++++++++++++++++++++----------------
>  1 file changed, 50 insertions(+), 20 deletions(-)
> 
> diff --git a/kernel/resource.c b/kernel/resource.c
> index fed052a..67b58a5 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -619,7 +619,7 @@ static int find_resource(struct resource *root, struct resource *new,
>  }
>  
>  /**
> - * reallocate_resource - allocate a slot in the resource tree given range & alignment.
> + * __reallocate_resource - allocate a slot in the resource tree given range & alignment.
>   *	The resource will be relocated if the new size cannot be reallocated in the
>   *	current location.
>   *
> @@ -628,7 +628,7 @@ static int find_resource(struct resource *root, struct resource *new,
>   * @newsize: new size of the resource descriptor
>   * @constraint: the size and alignment constraints to be met.
>   */
> -static int reallocate_resource(struct resource *root, struct resource *old,
> +static int __reallocate_resource(struct resource *root, struct resource *old,
>  			resource_size_t newsize,
>  			struct resource_constraint  *constraint)
>  {
> @@ -636,8 +636,6 @@ static int reallocate_resource(struct resource *root, struct resource *old,
>  	struct resource new = *old;
>  	struct resource *conflict;
>  
> -	write_lock(&resource_lock);
> -
>  	if ((err = __find_resource(root, old, &new, newsize, constraint)))
>  		goto out;
>  
> @@ -662,14 +660,13 @@ static int reallocate_resource(struct resource *root, struct resource *old,
>  		BUG_ON(conflict);
>  	}
>  out:
> -	write_unlock(&resource_lock);
>  	return err;
>  }
>  
> -
>  /**
> - * allocate_resource - allocate empty slot in the resource tree given range & alignment.
> - * 	The resource will be reallocated with a new size if it was already allocated
> + * __allocate_resource - allocate empty slot in the resource tree given range & alignment.
> + *	The resource will be reallocated with a new size if it was already
> + *	allocated
>   * @root: root resource descriptor
>   * @new: resource descriptor desired by caller
>   * @size: requested resource region size
> @@ -678,15 +675,17 @@ out:
>   * @align: alignment requested, in bytes
>   * @alignf: alignment function, optional, called if not NULL
>   * @alignf_data: arbitrary data to pass to the @alignf function
> + *
> + * Caller need to hold resource_lock if needed.
>   */
> -int allocate_resource(struct resource *root, struct resource *new,
> -		      resource_size_t size, resource_size_t min,
> -		      resource_size_t max, resource_size_t align,
> -		      resource_size_t (*alignf)(void *,
> -						const struct resource *,
> -						resource_size_t,
> -						resource_size_t),
> -		      void *alignf_data)
> +static int __allocate_resource(struct resource *root, struct resource *new,
> +				resource_size_t size, resource_size_t min,
> +				resource_size_t max, resource_size_t align,
> +				resource_size_t (*alignf)(void *,
> +						  const struct resource *,
> +						  resource_size_t,
> +						  resource_size_t),
> +				void *alignf_data)
>  {
>  	int err;
>  	struct resource_constraint constraint;
> @@ -700,20 +699,51 @@ int allocate_resource(struct resource *root, struct resource *new,
>  	constraint.alignf = alignf;
>  	constraint.alignf_data = alignf_data;
>  
> -	if ( new->parent ) {
> +	if (new->parent) {
>  		/* resource is already allocated, try reallocating with
>  		   the new constraints */
> -		return reallocate_resource(root, new, size, &constraint);
> +		return __reallocate_resource(root, new, size, &constraint);
>  	}
>  
> -	write_lock(&resource_lock);
>  	err = find_resource(root, new, size, &constraint);
>  	if (err >= 0 && __request_resource(root, new))
>  		err = -EBUSY;
> -	write_unlock(&resource_lock);
> +
>  	return err;
>  }
>  
> +/**
> + * allocate_resource - allocate empty slot in the resource tree given range & alignment.
> + *	The resource will be reallocated with a new size if it was already
> + *	allocated
> + * @root: root resource descriptor
> + * @new: resource descriptor desired by caller
> + * @size: requested resource region size
> + * @min: minimum boundary to allocate
> + * @max: maximum boundary to allocate
> + * @align: alignment requested, in bytes
> + * @alignf: alignment function, optional, called if not NULL
> + * @alignf_data: arbitrary data to pass to the @alignf function
> + */
> +int allocate_resource(struct resource *root, struct resource *new,
> +		      resource_size_t size, resource_size_t min,
> +		      resource_size_t max, resource_size_t align,
> +		      resource_size_t (*alignf)(void *,
> +						const struct resource *,
> +						resource_size_t,
> +						resource_size_t),
> +		      void *alignf_data)
> +{
> +	int ret;
> +
> +	write_lock(&resource_lock);
> +	ret = __allocate_resource(root, new, size, min, max, align,
> +				   alignf, alignf_data);
> +	write_unlock(&resource_lock);
> +
> +	return ret;
> +}
> +
>  EXPORT_SYMBOL(allocate_resource);
>  
>  /**
> -- 
> 1.8.4.5
>