lkml.org 
[lkml]   [2021]   [Apr]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [Patch] blk-wbt: fix a divide-by-zero error in rwb_arm_timer()
On Sat, Apr 17, 2021 at 9:41 PM Cong Wang <xiyou.wangcong@gmail.com> wrote:
>
> From: Cong Wang <cong.wang@bytedance.com>
>
> We hit a divide error in rwb_arm_timer() and crash dump shows
> rqd->scale_step is 16777215 (0xffffff in hex), so the expression
> "(rqd->scale_step + 1) << 8)" is 0x100000000, which is just beyond
> 32-bit integer range, hence it is truncated to 0 and int_sqrt(0)
> returns 0 too, so we end up passing 0 as a divisor to div_u64().
>

Never mind. rqd->scale_step should be capped by
rq_depth_scale_down(), so should never be so large. In the old
calc_wb_limits() implementation, rwb->wb_max was set to zero
accidentally.

Thanks.

\
 
 \ /
  Last update: 2021-04-20 21:54    [W:0.054 / U:0.024 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site