Re: [RFC][PATCH -mm] PM: Do not sync filesystems from within the freezer

Hi.

On Friday 06 July 2007 17:02:53 Rafael J. Wysocki wrote:

On Friday, 6 July 2007 00:00, Pavel Machek wrote:

quoted

Hi!

quoted

From: Rafael J. Wysocki <redacted>

The syncing of filesystems from within the freezer is generally not 

needed.

quoted

quoted

Change freeze_processes() so that it doesn't execute sys_sync() and make 

the

quoted

quoted

suspend and hibernation code path sync filesystems independently of the 

freezer.

quoted

Yes, we can do that, but ... why?

I think that sync and the freezer are different things and shouldn't be 

mixed in

such a way as they are now.

quoted

Does it actually fix FUSE?

It should prevent the freezer from deadlocking.

That's not the same thing. It's like saying "My footbrake grabs so I'll use 
the handbrake all the time. Take the stone out of the brake pad! :)

quoted

Miklos claims sync is nop on FUSE...? 

In that case there shouldn't be any deadlock, but a freezer failure. :-)

Isn't this scary? I'm agreeing with Pavel and the two of us seem to be 
disagreeing with everyone else!

To get more serious and practical though, I think the solution is to fuzz the 
userspace/kernelspace distinction. What we really want to do is freeze things 
that submit I/O, then sync, then freeze anything that processes I/O and needs 
to be frozen. In effect, redefine fuse processes as freezeable kernel 
threads.

Regards,

Nigel
-- 
See http://www.tuxonice.net for Howtos, FAQs, mailing
lists, wiki and bugzilla info.