Re: [UPDATE][PATCH 2/3] resource: Add release_mem_region_adjustable()

[Yasuaki Ishimatsu]

Hi Toshi,

2013/04/04 8:23, Toshi Kani wrote:
> Added release_mem_region_adjustable(), which releases a requested
> region from a currently busy memory resource.  This interface
> adjusts the matched memory resource accordingly if the requested
> region does not match exactly but still fits into.
> 
> This new interface is intended for memory hot-delete.  During
> bootup, memory resources are inserted from the boot descriptor
> table, such as EFI Memory Table and e820.  Each memory resource
> entry usually covers the whole contigous memory range.  Memory
> hot-delete request, on the other hand, may target to a particular
> range of memory resource, and its size can be much smaller than
> the whole contiguous memory.  Since the existing release interfaces
> like __release_region() require a requested region to be exactly
> matched to a resource entry, they do not allow a partial resource
> to be released.
> 
> There is no change to the existing interfaces since their restriction
> is valid for I/O resources.
> 
> Signed-off-by: Toshi Kani <toshi.kani@xxxxxx>

Reviewed-by : Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>

One nitpick below.

> ---
> 
> Updated per code reviews from Yasuaki Ishimatsu, Ram Pai and
> Gu Zheng.
> 
> ---
>   include/linux/ioport.h |    2 +
>   kernel/resource.c      |   93 ++++++++++++++++++++++++++++++++++++++++++++++++
>   2 files changed, 95 insertions(+)
> 
> diff --git a/include/linux/ioport.h b/include/linux/ioport.h
> index 85ac9b9b..0fe1a82 100644
> --- a/include/linux/ioport.h
> +++ b/include/linux/ioport.h
> @@ -192,6 +192,8 @@ extern struct resource * __request_region(struct resource *,
>   extern int __check_region(struct resource *, resource_size_t, resource_size_t);
>   extern void __release_region(struct resource *, resource_size_t,
>   				resource_size_t);
> +extern int release_mem_region_adjustable(struct resource *, resource_size_t,
> +				resource_size_t);
>   
>   static inline int __deprecated check_region(resource_size_t s,
>   						resource_size_t n)
> diff --git a/kernel/resource.c b/kernel/resource.c
> index ae246f9..c7966c3 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -1021,6 +1021,99 @@ void __release_region(struct resource *parent, resource_size_t start,
>   }
>   EXPORT_SYMBOL(__release_region);
>   
> +/**
> + * release_mem_region_adjustable - release a previously reserved memory region
> + * @parent: parent resource descriptor
> + * @start: resource start address
> + * @size: resource region size
> + *
> + * The requested region is released from a currently busy memory resource.
> + * It adjusts the matched busy memory resource accordingly if the requested
> + * region does not match exactly but still fits into.  Existing children of
> + * the busy memory resource must be immutable in this request.
> + *
> + * Note, when the busy memory resource gets split into two entries, the code
> + * assumes that all children remain in the lower address entry for simplicity.
> + * Enhance this logic when necessary.
> + */
> +int release_mem_region_adjustable(struct resource *parent,
> +			resource_size_t start, resource_size_t size)
> +{
> +	struct resource **p;
> +	struct resource *res, *new;
> +	resource_size_t end;
> +	int ret = -EINVAL;
> +

> +	end = start + size - 1;
> +	if ((start < parent->start) || (end > parent->end))
> +		return -EINVAL;

"ret" is initialized to -EINVAL. So how about use it?

Thanks,
Yasuaki Ishimatsu

> +
> +	p = &parent->child;
> +	write_lock(&resource_lock);
> +
> +	while ((res = *p)) {
> +		if (res->start >= end)
> +			break;
> +
> +		/* look for the next resource if it does not fit into */
> +		if (res->start > start || res->end < end) {
> +			p = &res->sibling;
> +			continue;
> +		}
> +
> +		if (!(res->flags & IORESOURCE_MEM))
> +			break;
> +
> +		if (!(res->flags & IORESOURCE_BUSY)) {
> +			p = &res->child;
> +			continue;
> +		}
> +
> +		/* found the target resource; let's adjust accordingly */
> +		if (res->start == start && res->end == end) {
> +			/* free the whole entry */
> +			*p = res->sibling;
> +			kfree(res);
> +			ret = 0;
> +		} else if (res->start == start && res->end != end) {
> +			/* adjust the start */
> +			ret = __adjust_resource(res, end + 1,
> +						res->end - end);
> +		} else if (res->start != start && res->end == end) {
> +			/* adjust the end */
> +			ret = __adjust_resource(res, res->start,
> +						start - res->start);
> +		} else {
> +			/* split into two entries */
> +			new = kzalloc(sizeof(struct resource), GFP_KERNEL);
> +			if (!new) {
> +				ret = -ENOMEM;
> +				break;
> +			}
> +			new->name = res->name;
> +			new->start = end + 1;
> +			new->end = res->end;
> +			new->flags = res->flags;
> +			new->parent = res->parent;
> +			new->sibling = res->sibling;
> +			new->child = NULL;
> +
> +			ret = __adjust_resource(res, res->start,
> +						start - res->start);
> +			if (ret) {
> +				kfree(new);
> +				break;
> +			}
> +			res->sibling = new;
> +		}
> +
> +		break;
> +	}
> +
> +	write_unlock(&resource_lock);
> +	return ret;
> +}
> +
>   /*
>    * Managed region resource
>    */
> --
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