Re: [PATCH v2 22/50] convert efivarfs

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Wed, 2025-11-05 at 14:46 +0100, Christian Brauner wrote:
> On Wed, Nov 05, 2025 at 08:33:10AM -0500, James Bottomley wrote:
> > On Wed, 2025-11-05 at 14:16 +0100, Christian Brauner wrote:
> > > On Wed, Nov 05, 2025 at 08:09:03AM -0500, James Bottomley wrote:
> > > > On Wed, 2025-11-05 at 12:47 +0100, Christian Brauner wrote:
> > [...]
> > > > > And suspend/resume works just fine with freeze/thaw. See
> > > > > commit
> > > > > eacfbf74196f ("power: freeze filesystems during
> > > > > suspend/resume") which implements exactly that.
> > > > > 
> > > > > The reason this didn't work for you is very likely:
> > > > > 
> > > > > cat /sys/power/freeze_filesystems
> > > > > 0
> > > > > 
> > > > > which you must set to 1.
> > > > 
> > > > Actually, no, that's not correct.  The efivarfs freeze/thaw
> > > > logic must run unconditionally regardless of this setting to
> > > > fix the systemd bug, so all the variable resyncing is done in
> > > > the thaw call, which isn't conditioned on the above (or at
> > > > least it shouldn't be).
> > > 
> > > It is conditioned on the above currently but we can certainly fix
> > > it easily to not be.
> > 
> > It still seems to be unconditional in upstream 6.18-rc4
> > kernel/power/hibernate.c with only freeze being conditioned on the
> 
> I'm honestly not sure how efivarfs would be frozen if
> filesystems_freeze() isn't called... Maybe I missed that memo though.
> In any case I just sent you...

We don't need to be frozen: our freeze_fs method is empty, we just need
thaw_fs calling.

Is the trouble that there's now freeze/thaw accounting, so thaw won't
be called based on that if freeze wasn't?  In which case might it not
be better for us to implement thaw_super, which is called
unconditionally and leaves the accounting up to the filesystem?

> > setting of the filesystem_freeze variable but I haven't checked -
> > next.
> > 
> > However, if there's anything in the works to change that we would
> > need an exception for efivarfs, please ... we can't have a bug fix
> > conditioned on a user setting.
> 
> ... a patch in another mail.
> 
> Sorry in case I misunderstood that you _always_ wanted that sync
> regardless of userspace enabling it.

We need the thaw method called to get the variable resync to happen. 
That fixes a bug on hibernate with systemd (and also accounts for an
other efi variable changes the user may have made between hibernate and
resume), yes.  And we need that to happen unconditionally to fix the
systemd bug.

Regards,

James