On Fri, Aug 31, 2018 at 04:22:41PM -0400, Dennis Zhou wrote: > Hi everyone, > > This is a split of an earlier series I sent out [1] containing the first > 3 patches with fixes from feedback. This series tackles the first > problem where blkcgs were not being destroyed. > > There is a regression in blkcg destruction where references weren't > properly put causing blkcgs to never be destroyed. Previously, blkgs > were destroyed during offlining of the blkcg. This puts back the blkcg > reference a blkg holds allowing blkcg ref to reach zero. Then, > blkcg_css_free() is called as part of the final cleanup. > > To address the problem, 0001 reverts the broken commit, 0002 delays > blkg destruction until writeback has finished, and 0003 closes the > window on a race condition between a css migration and dying, and > blkg association. This should fix the issue where blkg_get() was getting > called when a blkcg had already begun exiting. If a bio finds itself > here, it will just fall back to root. Oddly enough at one point, > blk-throttle was using policy data from and associating with potentially > different blkgs, thus how this was exposed. For patches 1-3, Acked-by: Tejun Heo <tj@xxxxxxxxxx> Thanks. -- tejun
