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SubjectRe: [PATCH] memblock: Make sure reserved.regions is freed really
Hello, Yinghai.

On Fri, Jun 15, 2012 at 08:12:11PM -0700, Yinghai Lu wrote:
> memblock_free() would double reserved.regions too, so we could free
> old range for reserved.regions.
>
> So need to check that regions get doubled. If it is doubled, we need to
> free it.
>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
>
> ---
> mm/memblock.c | 23 +++++++++++++++++++++--
> 1 file changed, 21 insertions(+), 2 deletions(-)
>
> Index: linux-2.6/mm/memblock.c
> ===================================================================
> --- linux-2.6.orig/mm/memblock.c
> +++ linux-2.6/mm/memblock.c
> @@ -148,11 +148,26 @@ phys_addr_t __init_memblock memblock_fin
> */
> int __init_memblock memblock_free_reserved_regions(void)
> {
> + struct memblock_region *r;
> + int ret;
> +
> if (memblock.reserved.regions == memblock_reserved_init_regions)
> return 0;
>
> - return memblock_free(__pa(memblock.reserved.regions),
> - sizeof(struct memblock_region) * memblock.reserved.max);
> + /*
> + * During memblock_free, reserved.regions could be doubled,
> + * try to check with old one for checking, and need to free the new one.
> + */
> + do {
> + r = memblock.reserved.regions;
> + ret = memblock_free(__pa(memblock.reserved.regions),
> + sizeof(struct memblock_region) * memblock.reserved.max);
> +
> + if (ret)
> + break;
> + } while (memblock.reserved.regions != r);
> +
> + return ret;
> }

Hmmm... nice catch but I think it's a bit complex and ugly. In this
case, we *know* that the region isn't gonna be split. Maybe a better
option is to add something like the following?

void memblock_remove_region_by_ptr(struct memblock_type *type,
struct memblock_region *r)
{
WARN_ON(/* make sure @r is inside @type->regions */);
memblock_remove_region(type, r - type->regions);
}

Thanks.

--
tejun


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