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cfq: explicitly use 64bit divide operation for 64bit arguments

'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@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
master
Anatol Pomozov 8 years ago
committed by Jens Axboe
parent
commit
f3cff25f05
  1. 2
      block/cfq-iosched.c

2
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;

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