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Date: Wed, 03 Apr 2013 15:37:31 +0800
From: Gu Zheng <guz.fnst@...fujitsu.com>
To: Toshi Kani <toshi.kani@...com>
CC: akpm@...ux-foundation.org, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, linuxram@...ibm.com, tmac@...com,
isimatu.yasuaki@...fujitsu.com, wency@...fujitsu.com,
tangchen@...fujitsu.com, jiang.liu@...wei.com
Subject: Re: [PATCH 2/3] resource: Add release_mem_region_adjustable()
On 04/03/2013 12:17 AM, 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@...com>
> ---
> include/linux/ioport.h | 2 +
> kernel/resource.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 89 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..789f160 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -1021,6 +1021,93 @@ 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 = 0;
> +
> + p = &parent->child;
> + end = start + size - 1;
> +
> + write_lock(&resource_lock);
> +
> + while ((res = *p)) {
> + if (res->start > start || res->end < end) {
> + p = &res->sibling;
> + continue;
> + }
> +
> + if (!(res->flags & IORESOURCE_MEM)) {
> + ret = -EINVAL;
> + break;
> + }
> +
> + if (!(res->flags & IORESOURCE_BUSY)) {
> + p = &res->child;
> + continue;
> + }
> +
> + if (res->start == start && res->end == end) {
> + /* free the whole entry */
> + *p = res->sibling;
> + kfree(res);
> + } 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;
> +}
> +
Hi Toshi,
What about the following small changes? Maybe it can make the code more rigorous~
Thanks,
Gu
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 = 0;
end = start + size - 1;
if ((start < parent->start) || (end > parent->end))
return -EINVAL;
p = &parent->child;
write_lock(&resource_lock);
while (res = *p) {
if (res->start <= start && res->end >= end) {
if (!(res->flags & IORESOURCE_MEM)) {
ret = -EINVAL;
break;
}
if (!(res->flags & IORESOURCE_BUSY)) {
p = &res->child;
continue;
}
if (res->start == start && res->end == end) {
/* free the whole entry */
*p = res->sibling;
kfree(res);
} 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;
}
p = &res->sibling;
}
write_unlock(&resource_lock);
return ret;
}
> /*
> * Managed region resource
> */
> --
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