[PATCH] xfs: introduce "metasync" api to sync metadata to fsblock

[Pingfan Liu]

On Mon, Oct 14, 2019 at 01:40:27AM -0700, Christoph Hellwig wrote:
> On Sun, Oct 13, 2019 at 10:37:00PM +0800, Pingfan Liu wrote:
> > When using fadump (fireware assist dump) mode on powerpc, a mismatch
> > between grub xfs driver and kernel xfs driver has been obsevered.  Note:
> > fadump boots up in the following sequence: fireware -> grub reads kernel
> > and initramfs -> kernel boots.
> 
> This isn't something new.  To fundamentally fix this you need to
> implement (in-memory) log recovery in grub.  That is the only really safe
> long-term solutioin.  But the equivalent of your patch you can already
Agree. For the consistency of the whole fs, we need grub to be aware of
log. While this patch just assumes that files accessed by grub are
known, and the consistency is forced only on these files.
> get by freezing and unfreezing the file system using the FIFREEZE and
> FITHAW ioctls.  And if my memory is serving me correctly Dave has been
freeze will block any further modification to the fs. That is different
from my patch, which does not have such limitation.
> preaching that to the bootloader folks for a long time, but apparently
> without visible results.
Yes, it is a pity. And maybe it is uneasy to do.

Thanks and regards,
	Pingfan