Re: [PATCH] fs / ext3: Always unlock updates in ext3_freeze()

Pavel Machek
2011-08-25T13:50:09Z

Hi!

> > > > The problem really isn't XFS specific, nor is it new - the fact is
> > > > that any filesystem that has registered a shrinker or can do async
> > > > work in the background post-sync is vulnerable to this problem. It's
> > >
> > > Should we avoid calling shrinkers while hibernating?
> >
> > If you like getting random OOM problems when hibernating, then go
> > for it. Besides, shrinkers are used for more than just filesystems,
> > so you might find you screw entire classes of users by doing this
> > (eg everyone using intel graphics and 3D).
> >
> > > Or put BUG_ON()s into filesystem shrinkers so that this can not
> > > happen?
> >
> > Definitely not. If your concern is filesystem shrinkers and you want
> > a large hammer to hit the problem with then do your hibernate
> > image allocation wih GFP_NOFS and the filesystem shrinkers will
> > abort without doing anything.
>
> I think we can do that, actually.

I believe we should, yes. Question is if it helps much, because
various drivers (and userspace in case uswsusp?) will still trigger
GFP_KERNEL allocations.

Something like this?

--- snapshot.c.ofic 2011-08-25 15:48:41.000000000 +0200
+++ snapshot.c 2011-08-25 15:49:07.000000000 +0200
@@ -1107,7 +1107,7 @@

/* Helper functions used for the shrinking of memory. */

-#define GFP_IMAGE (GFP_KERNEL | __GFP_NOWARN)
+#define GFP_IMAGE (GFP_NODS | __GFP_NOWARN)

/**
* preallocate_image_pages - Allocate a number of pages for hibernation image

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