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SubjectRe: [PATCH v2] mm: BUG when __kmap_atomic_idx equals KM_TYPE_NR
On Thu, 31 Jul 2014, Chintan Pandya wrote:

> __kmap_atomic_idx is per_cpu variable. Each CPU can
> use KM_TYPE_NR entries from FIXMAP i.e. from 0 to
> KM_TYPE_NR - 1. Allowing __kmap_atomic_idx to over-
> shoot to KM_TYPE_NR can mess up with next CPU's 0th
> entry which is a bug. Hence BUG_ON if
> __kmap_atomic_idx >= KM_TYPE_NR.
>

This appears to be a completely different patch, not a v2. Why is this
check only done for CONFIG_DEBUG_HIGHMEM?

I think Andrew's comment earlier was referring to the changelog only and
not the patch, which looked correct.

> Signed-off-by: Chintan Pandya <cpandya@codeaurora.org>
> ---
> Changes:
>
> V1 --> V2
>
> Not touching CONFIG_DEBUG_HIGHMEM.
>
> include/linux/highmem.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/highmem.h b/include/linux/highmem.h
> index 7fb31da..9286a46 100644
> --- a/include/linux/highmem.h
> +++ b/include/linux/highmem.h
> @@ -93,7 +93,7 @@ static inline int kmap_atomic_idx_push(void)
>
> #ifdef CONFIG_DEBUG_HIGHMEM
> WARN_ON_ONCE(in_irq() && !irqs_disabled());
> - BUG_ON(idx > KM_TYPE_NR);
> + BUG_ON(idx >= KM_TYPE_NR);
> #endif
> return idx;
> }


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