Re: [RFC 4/5] ext4: add fs freezing support on suspend/hibernation

[Theodore Ts'o]

On Wed, Oct 04, 2017 at 06:05:23PM +1100, Dave Chinner wrote:
> Basically, before thawing filesystems the rest of the kernel
> infrastructure needs to have been restarted. i.e. the order
> needs to be:
> 
> freeze userspace
> freeze filesystems
> freeze kernel threads
> freeze workqueues
> 
> thaw workqueues
> thaw kernel threads
> thaw filesystems
> thaw userspace
> 
> and it should end up that way.
> 
> > Or if we have a network block device, or
> > something else in the storage stack that needs to run a kernel thread
> > context (or a workqueue, etc.) --- is the fact that userspace is
> > frozen mean the scheduler is going to refuse to schedule()?
> 
> No.

Well, that's what the answer *should* be.  I was asking what this
patch series does, and given that Luis reported that with this patch
series ext4_commit_super(sb, 1) is hanging, I have my suspicions about
what the answer might be with this patch set.  (Especially since the
claimed goal of the patch set is, "kthread freezing with filesystem
freeze/thaw".

Cheers,

						- Ted