Hi, Tejun
On Fri, Aug 30, 2013 at 10:52 AM, Anatol Pomozov
<anatol.pomozov@xxxxxxxxx> wrote:
> 'samples' is 64bit operant, but do_div() second parameter is 32.
> do_div silently truncates high 32 bits and calculated result
> is invalid.
>
> In case if low 32bit of 'samples' are zeros then do_div() produces
> kernel crash.
>
> Signed-off-by: Anatol Pomozov <anatol.pomozov@xxxxxxxxx>
> ---
> block/cfq-iosched.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
> index d5bbdcf..c410752 100644
> --- a/block/cfq-iosched.c
> +++ b/block/cfq-iosched.c
> @@ -1803,7 +1803,7 @@ static u64 cfqg_prfill_avg_queue_size(struct seq_file *sf,
>
> if (samples) {
> v = blkg_stat_read(&cfqg->stats.avg_queue_size_sum);
> - do_div(v, samples);
> + v = div64_u64(v, samples);
> }
> __blkg_prfill_u64(sf, pd, v);
> return 0;
what do you think about this patch?
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