Re: [LSF/MM/BPF TOPIC] Filesystem Suspend Resume

James Bottomley
2025-03-21T17:00:25Z

On Fri, 2025-03-21 at 08:34 -0400, James Bottomley wrote:
[...]
> Let me digest all that and see if we have more hope this time around.

OK, I think I've gone over it all. The biggest problem with
resurrecting the patch was bugs in ext3, which isn't a problem now.
Most of the suspend system has been rearchitected to separate
suspending user space processes from kernel ones. The sync it
currently does occurs before even user processes are frozen. I think
(as most of the original proposals did) that we just do freeze all
supers (using the reverse list) after user processes are frozen but
just before kernel threads are (this shouldn't perturb the image
allocation in hibernate, which was another source of bugs in xfs).

There's a final wrinkle in that if I plumb efivarfs into all this, it
needs to know whether it was a hibernate or suspend, but I can add that
as an extra freeze_holder flag.

This looked like such a tiny can of worms when I opened it; now it
seems to be a lot bigger on the inside than it was on the outside,
sigh.

Regards,

James