Messages in this thread Patch in this message | | | Date | Mon, 29 Nov 2021 08:19:17 -1000 | From | Tejun Heo <> | Subject | Re: [PATCH v2] block: Use div64_ul instead of do_div |
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On Thu, Nov 18, 2021 at 03:40:33AM +0000, cgel.zte@gmail.com wrote: > From: Changcheng Deng <deng.changcheng@zte.com.cn> > > do_div() does a 64-by-32 division. Here the divisor is an unsigned long > which on some platforms is 64 bit wide. So use div64_ul instead of do_div > to avoid a possible truncation. > > Reported-by: Zeal Robot <zealci@zte.com.cn> > Signed-off-by: Changcheng Deng <deng.changcheng@zte.com.cn> > --- > block/blk-throttle.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/block/blk-throttle.c b/block/blk-throttle.c > index 39bb6e68a9a2..2db635d66617 100644 > --- a/block/blk-throttle.c > +++ b/block/blk-throttle.c > @@ -1903,7 +1903,7 @@ static void throtl_downgrade_check(struct throtl_grp *tg) > > if (tg->bps[READ][LIMIT_LOW]) { > bps = tg->last_bytes_disp[READ] * HZ; > - do_div(bps, elapsed_time); > + bps = div64_ul(bps, elapsed_time);
Yeah, the divisor is ulong for whatever reason but the thing is in jiffies. I have a hard time imagining it overflowing 32bit. I'm not sure how useful this patch is.
-- tejun
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