linux-kernel - Re: [PATCH 0/6] power: wire-up filesystem freeze/thaw with suspend/resume

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Message-ID: <89ee0561d668c0c10f118a73084c619ef385a040.camel@HansenPartnership.com>
Date: Tue, 08 Apr 2025 13:24:47 -0400
From: James Bottomley <James.Bottomley@...senPartnership.com>
To: Luis Chamberlain <mcgrof@...nel.org>
Cc: Christian Brauner <brauner@...nel.org>, linux-fsdevel@...r.kernel.org, 
 jack@...e.cz, rafael@...nel.org, Ard Biesheuvel <ardb@...nel.org>, 
 linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org, hch@...radead.org,
  david@...morbit.com, djwong@...nel.org, pavel@...nel.org,
 peterz@...radead.org,  mingo@...hat.com, will@...nel.org,
 boqun.feng@...il.com
Subject: Re: [PATCH 0/6] power: wire-up filesystem freeze/thaw with
 suspend/resume

On Tue, 2025-04-08 at 10:09 -0700, Luis Chamberlain wrote:
> On Tue, Apr 08, 2025 at 11:43:46AM -0400, James Bottomley wrote:
[...]
> > I've now done some extensive testing on loop nested filesystems
> > with fio load on the upper. I've tried xfs on ext4 and ext4 on
> > ext4. Hibernate/Resume has currently worked on these without a
> > hitch (and the fio load burps a bit but then starts running at full
> > speed within a few seconds). What I'm doing is a single round of
> > hibernate/resume followed by a reboot. I'm relying on the fschecks
> > to detect any filesystem corruption. I've also tried doing a couple
> > of fresh starts of the hibernated image to check that we did
> > correctly freeze the filesystems.
> > 
> > The problems I've noticed are:
> > 
> >    1. I'm using 9p to push host directories throught and that
> >       completely hangs after a resume. This is expected because the
> >       virtio server is out of sync, but it does indicate a need to
> >       address Jeff's question of what we should be doing for
> > network
> >       filesystems (and is also the reason I have to reboot after
> >       resuming).
> >    2. Top doesn't show any CPU activity after resume even though
> > fio is
> >       definitely running.  This seems to be a suspend issue and
> >       unrelated to filesystems, but I'll continue investigating.
> 
> To be clear, on the fio run -- are you running fio *while*
> suspend/resume cycle on XFS?

Yes, that's why I said "the fio load burps a bit" (as in after resume)
"but then starts running full speed after a few seconds".

>  That used to stall / break suspend resume. We may want to test dd
> against a drive too, that will use the block device cache, and I
> forget if we have a freeze/thaw for it.

fio is running a read/write test, but I think all my caches are write
through for safety (although I have verified that the device cache
flush is sent as the last sequence of hibernate).

Regards,

James