Re: [PATCH] mm: call into direct reclaim without PF_MEMALLOC set

[Andrew Morton <akpm@osdl.org>]

On Wed, 15 Nov 2006 23:12:19 +0100
Arjan van de Ven <arjan@fenrus.demon.nl> wrote:

> On Wed, 2006-11-15 at 14:00 -0800, Andrew Morton wrote:
> > On Wed, 15 Nov 2006 22:32:58 +0100
> > Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
> > 
> > > +			current->flags |= PF_MEMALLOC;
> > >  			try_to_free_pages(zones, GFP_NOFS);
> > > +			current->flags &= ~PF_MEMALLOC;
> > 
> > Sometime, later, in a different patch, we might as well suck that into
> > try_to_free_pages() itself.   Along with nice comment explaining
> > what it means and WARN_ON(current->flags & PF_MEMALLOC).
> 
> also I've seen a few cases where this will break.
> If you already *have* PF_MEMALLOC you'd lose it here; it's generally a
> mistake to do so. It's a lot safer to save the old value and restore
> it...

it does:

+		if (*zones && !(current->flags & PF_MEMALLOC)) {
+			current->flags |= PF_MEMALLOC;
 			try_to_free_pages(zones, GFP_NOFS);
+			current->flags &= ~PF_MEMALLOC;
+		}

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