From: Tejun Heo > Sent: 04 December 2024 17:41 > > Hello, > > On Wed, Dec 04, 2024 at 07:50:14PM +0300, Dan Carpenter wrote: > > Tejun probably reads everything to linux-block, but let's CC him explicitly. > > Oh, I'm not. Thanks for cc'ing. > > > block/blk-iocost.c > > 2222 TRACE_IOCG_PATH(iocg_idle, iocg, now, > > 2223 atomic64_read(&iocg->active_period), > > 2224 atomic64_read(&ioc->cur_period), vtime); > > 2225 __propagate_weights(iocg, 0, 0, false, now); > > ^ > > Why is "active" zero? __propagate_weights() does a clamp() to 1 as minimum and > > we've added new build time asserts so this breaks the build. > > > > 2226 list_del_init(&iocg->active_list); > > ... > > This is a good catch. It's impressive that this can be caught at compile > time. The upper limit can become zero but the lower limit should win as > that's there to protect against divide by zero, so I think the right thinig > to do is replacing clamp() with max(min()). Is someone interested in writing > up the patch and sending it Jens' way? Perhaps if written as: inuse = min(inuse, active) ?: 1; it might stop someone changing it back. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
