On Sat, Apr 17, 2021 at 9:41 PM Cong Wang <xiyou.wangc...@gmail.com> wrote: > > From: Cong Wang <cong.w...@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.
