Re: [PATCH] libata, freezer: avoid block device removal while system is frozen

Ming Lei
2013-12-16T13:24:42Z

On Mon, Dec 16, 2013 at 8:45 PM, Tejun Heo <tj@kernel.org> wrote:
> Hello,
>
> On Mon, Dec 16, 2013 at 08:12:07PM +0800, Ming Lei wrote:
>> Looks we should guarantee that I/O queue is emptied before system sleep,
>> otherwise it may be a bug, since battery may be drained up to cause
>> data loss or block devices may be disconnected during sleep.
>
> It's a bit beside the point as that's what journaling is for. Power
> loss during suspend isn't all that different from power loss while
> suspended. Also, the filesystems are already synced before entering
> suspend, so it shouldn't be an issue. However, that doesn't guarantee
> there aren't no pending bdi work items. We *hope* to control the

You mean there are still some write I/O scheduled after processes are
frozen? by unfreezable kernel threads?

> sources with freezer but there's no guarantee about the coverage and
> no way to verify that either.

Thanks,
--
Ming Lei