| Message ID | 20211118034033.163550-1-deng.changcheng@zte.com.cn (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] block: Use div64_ul instead of do_div | expand |
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.
Hello. On Thu, Nov 18, 2021 at 03:40:33AM +0000, cgel.zte@gmail.com wrote: > Reported-by: Zeal Robot <zealci@zte.com.cn> > Signed-off-by: Changcheng Deng <deng.changcheng@zte.com.cn> Just feedback to the bot or to you -- the same do_div() is in the same function for writes too. I think the processing shouldn't stop at the first occurence. Michal
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); if (bps >= tg->bps[READ][LIMIT_LOW]) tg->last_low_overflow_time[READ] = now; }