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SubjectRe: [PATCH] mm,x86: fix span coverage in e820_all_mapped()
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On Tue, Dec 10, 2013 at 1:06 AM, Xishi Qiu <qiuxishi@huawei.com> wrote:
> In the following case, e820_all_mapped() will return 1.
> A < start < B-1 and B < end < C, it means <start, end> spans two regions.
> <start, end>: [start - end]
> e820 addr: ...[A - B-1][B - C]...

should be [start, end) right?
and
[A, B),[B, C)

>
> Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
> ---
> arch/x86/kernel/e820.c | 15 +++------------
> 1 files changed, 3 insertions(+), 12 deletions(-)
>
> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
> index 174da5f..31ecab2 100644
> --- a/arch/x86/kernel/e820.c
> +++ b/arch/x86/kernel/e820.c
> @@ -85,20 +85,11 @@ int __init e820_all_mapped(u64 start, u64 end, unsigned type)
>
> if (type && ei->type != type)
> continue;
> - /* is the region (part) in overlap with the current region ?*/
> + /* is the region (part) in overlap with the current region ? */
> if (ei->addr >= end || ei->addr + ei->size <= start)
> continue;
> -
> - /* if the region is at the beginning of <start,end> we move
> - * start to the end of the region since it's ok until there
> - */
> - if (ei->addr <= start)
> - start = ei->addr + ei->size;

so in your case new start will be B ?

next run will be C

> - /*
> - * if start is now at or beyond end, we're done, full
> - * coverage
> - */
> - if (start >= end)


> + /* is the region full coverage of <start, end> ? */
> + if (ei->addr <= start && ei->addr + ei->size >= end)
> return 1;
> }
> return 0;

also e820 should be sanitized already to have [A,C).

or you are talking about [A,B), [B+1, C)
first run start will be B, and next run with [B+1, ...), that will be
skipped...
will not return 1.

so old code should be ok.

Thanks

Yinghai


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