From f3cff25f05f2ac29b2ee355e611b0657482f6f1d Mon Sep 17 00:00:00 2001 From: Anatol Pomozov Date: Sun, 22 Sep 2013 12:43:47 -0600 Subject: [PATCH] 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 Acked-by: Tejun Heo Signed-off-by: Jens Axboe --- 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 f0468e252ee4..51e06ea06a2e 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; -- 2.20.1