Tang Junhui-- Thank you for the feedback. On Mon, Jan 1, 2018 at 10:33 PM, <tang.junhui@xxxxxxxxxx> wrote: > From: Tang Junhui <tang.junhui@xxxxxxxxxx> > > This patch is useful for preventing the overflow of the expression > (cache_dirty_target * bdev_sectors(dc->bdev)), but it also > lead into a calc error, for example, when there is a 1G and > 100*164G cached device, it would cause the "target" value to > be aways zero of the 1G device, which would cause write-back > threshold losing efficacy. > > Maybe at first we can judge if it overflows or not of the expression > (cache_dirty_target * bdev_sectors(dc->bdev)), if it overflows, > We can calc the value of target as the patch, otherwise, > we calc it as old way. Maybe it'd be preferable just to ensure that share always >=1. It seems like a pretty narrow set of cases where the current math works and the new math doesn't work, though, as I expect that it's relatively rare to have such a variation in sizes, and even so 16.4TB uses up 35 bits of the 64 bit quantity. I don't really like special cases or trying two different ways to do the math, because then it's very difficult to test. What do you think? Mike
