On Mon, Apr 08, 2013 at 03:47:35PM -0600, 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 even 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>
> ---
>
> Added #ifdef CONFIG_MEMORY_HOTPLUG as suggested by Andrew Morton.
>
> ---
> include/linux/ioport.h | 4 ++
> kernel/resource.c | 96 ++++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 100 insertions(+)
>
> diff --git a/include/linux/ioport.h b/include/linux/ioport.h
> index 85ac9b9b..961d4dc 100644
> --- a/include/linux/ioport.h
> +++ b/include/linux/ioport.h
> @@ -192,6 +192,10 @@ 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);
> +#ifdef CONFIG_MEMORY_HOTPLUG
> +extern int release_mem_region_adjustable(struct resource *, resource_size_t,
> + resource_size_t);
> +#endif
>
> 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..25b945c 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -1021,6 +1021,102 @@ void __release_region(struct resource *parent, resource_size_t start,
> }
> EXPORT_SYMBOL(__release_region);
>
> +#ifdef CONFIG_MEMORY_HOTPLUG
> +/**
> + * release_mem_region_adjustable - release a previously reserved memory region
> + * @parent: parent resource descriptor
> + * @start: resource start address
> + * @size: resource region size
> + *
> + * This interface is intended for memory hot-delete. The requested region is
> + * released from a currently busy memory resource. It adjusts the matched
> + * busy memory resource accordingly even 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 ret;
> +
> + 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;
> + }
What if the resource overlaps. In other words, the res->start > start
but res->end > end ?
Also do you handle the case where the range <start,end> spans
across multiple adjacent resources?
--
Ram Pai
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