On Thu, Mar 17, 2022 at 11:08:04PM +0900, Tetsuo Handa wrote:
> Commit 87579e9b7d8dc36e ("loop: use worker per cgroup instead of kworker")
> again started using per device workqueue
>
> - lo->worker_task = kthread_run(loop_kthread_worker_fn,
> - &lo->worker, "loop%d", lo->lo_number);
> + lo->workqueue = alloc_workqueue("loop%d",
> + WQ_UNBOUND | WQ_FREEZABLE,
> + 0,
> + lo->lo_number);
>
> but forgot to restore WQ_MEM_RECLAIM flag.
Early versions of the patch did have WQ_MEM_RECLAIM but it was
removed. I looked up my notes and found this:
Changes since V11:
* Removed WQ_MEM_RECLAIM flag from loop workqueue. Technically, this
can be driven by writeback, but this was causing a warning in xfs
and likely other filesystems aren't equipped to be driven by reclaim
at the VFS layer.
I don't know if this is still the case. Can you test it?
> I don't know why WQ_FREEZABLE flag was added
My memory here is hazy and I don't have it in my notes but the same is
done in block/blk-cgroup.c which is conceptually quite similar.
