Re: [PATCH v8 03/10] md: Neither resync nor reshape while the system is frozen

[Shaohua Li <shli@kernel.org>]

On Wed, Oct 11, 2017 at 05:17:56PM +0000, Bart Van Assche wrote:
> On Tue, 2017-10-10 at 18:48 -0700, Shaohua Li wrote:
> > The problem is __md_stop_writes set some bit like MD_RECOVERY_FROZEN, which
> > will prevent md_check_recovery restarting resync/reshape. I think we need
> > preserve mddev->recovery in suspend prepare and restore after resume
> 
> Hello Shaohua,
> 
> As far as I can see __md_stop_writes() sets MD_RECOVERY_FROZEN and can set
> MD_RECOVERY_INTR. Since md_check_recovery() clears MD_RECOVERY_INTR I think
> it should be sufficient to save and restore the state of the
> MD_RECOVERY_FROZEN flag. However, when I ran the following test:
> * echo frozen > /sys/block/md0/md/sync_action
> * cat /sys/block/md0/md/sync_action
> * systemctl hibernate
> * (power on system again)
> * cat /sys/block/md0/md/sync_action
> 
> the output that appeared was as follows:
> 
> frozen
> idle 
> Does that mean that a hibernate or suspend followed by a resume is sufficient
> to clear the MD_RECOVERY_FROZEN flag for the md drivers and hence that the
> patch at the start of this e-mail thread does not need any further
> modifications?

Have no idea why it shows 'idle'. From my understanding, after resume, previous
memory is stored and MD_RECOVERY_FROZEN bit should be set. Was trying to
understand what happens.

Thanks,
Shaohua