linux-kernel - Re: [PATCH 2/3] swsusp: Do not use page flags

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Message-Id: <200703160101.26384.rjw@sisk.pl>
Date:	Fri, 16 Mar 2007 01:01:25 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Jiri Kosina <jikos@...os.cz>, Pavel Machek <pavel@....cz>,
	a.p.zijlstra@...llo.nl, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] swsusp: Do not use page flags

On Thursday, 15 March 2007 23:23, Andrew Morton wrote:
> On Thu, 15 Mar 2007 23:19:02 +0100 (CET)
> Jiri Kosina <jikos@...os.cz> wrote:
> 
> > On Thu, 15 Mar 2007, Andrew Morton wrote:
> > 
> > > > > And why _does_ suspend use GFP_ATOMIC all over the place?
> > > > Generally, because it cannot sleep.
> > > Why not?
> > 
> > I guess it's simply beucase of kswapd being already frozen, so there is no 
> > chance that once GFP_KERNEL allocation goes to sleep, it is going to get 
> > any free pages eventually ... ?
> 
> No, things should run fine with a dead kswapd.
> 
> There are reasons why we can't call into filesystems from there, but
> GFP_NOIO will ensure that and it is heaps better than GFP_ATOMIC.

In fact the role of swsusp_shrink_memory() is to ensure that our subsequent
atomic allocations won't fail.

Still, the particular allocations in create_basic_memory_bitmaps() are made
before we call swsusp_shrink_memory(), so it's better to use GFP_NOIO in there.

I'll prepare a patch for that on top of the current series.
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