Re: [PATCH 2/8] bitmap: Introduce bitmap_set, bitmap_clear, bitmap_find_next_zero_area

[Akinobu Mita <akinobu.mita@gmail.com>]

2009/10/17 FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>:
> On Tue, 13 Oct 2009 18:10:17 +0900
> Akinobu Mita <akinobu.mita@gmail.com> wrote:
>
>> My user space testing exposed off-by-one error find_next_zero_area
>> in iommu-helper. Some zero area cannot be found by this bug.
>>
>> Subject: [PATCH] Fix off-by-one error in find_next_zero_area
>>
>> Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
>> ---
>> =A0lib/iommu-helper.c | =A0 =A02 +-
>> =A01 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/lib/iommu-helper.c b/lib/iommu-helper.c
>> index 75dbda0..afc58bc 100644
>> --- a/lib/iommu-helper.c
>> +++ b/lib/iommu-helper.c
>> @@ -19,7 +19,7 @@ again:
>> =A0 =A0 =A0 index =3D (index + align_mask) & ~align_mask;
>>
>> =A0 =A0 =A0 end =3D index + nr;
>> - =A0 =A0 if (end >=3D size)
>> + =A0 =A0 if (end > size)
>
> I think that this is intentional; the last byte of the limit doesn't
> work.

It looks ok to me. Without above change, find_next_zero_area cannot
find a 64 bits zeroed area in next sample code.

        unsigned long offset;

        DECLARE_BITMAP(map, 64);

        bitmap_clear(map, 0, 64);
        offset =3D find_next_zero_area(map, 64, 0, 64, 0);
        if (offset >=3D 64)
                printf("not found\n");
        else
                printf("found\n");