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

[Christoph Hellwig <hch@infradead.org>]

On Thu, Mar 20, 2025 at 11:36:17AM -0400, James Bottomley wrote:
> Part of the thought here is that other filesystems might possibly want
> suspend resume hooks as well, although not for the reasons efivarfs
> does:  Hibernate is a particularly risky operation and resume may not
> work leading to a full reboot and filesystem inconsistencies. In many
> ways, a failed resume is exactly like a system crash, for which
> filesystems already make specific guarantees.  However, it is a crash
> for which they could, if they had power management hooks, be forewarned
> and possibly make the filesystem cleaner for eventual full restore. 
> Things like guaranteeing that uncommitted data would be preserved even
> if a resume failed, which isn't something we guarantee across a crash
> today.

We finally got hibernate to freeze file system on suspend, which is the
right thing for the above reasons.

This might not work quite as well for virtual file systems tied to an
actualy resource like efivarsfs, so you might just register a fake
device to get the system suspend/resume notifications for it.  Or
whatever better way the PM and device model maintainers things that
suites, but definitively something that isn't a file system interface.