linux-kernel - Re: 2.6.25-rc7-git2: Reported regressions from 2.6.24

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Message-ID: <alpine.LFD.1.00.0803272050290.14670@woody.linux-foundation.org>
Date:	Thu, 27 Mar 2008 21:00:14 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Christoph Lameter <clameter@....com>
cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Pawel Staszewski <pstaszewski@...com.pl>,
	LKML <linux-kernel@...r.kernel.org>,
	Adrian Bunk <bunk@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Natalie Protasevich <protasnb@...il.com>
Subject: Re: 2.6.25-rc7-git2: Reported regressions from 2.6.24



On Thu, 27 Mar 2008, Christoph Lameter wrote:
> 
> Slab allocations can never use GFP_HIGHMEM.

Totally irrelevant.

The page allocation path does

        if (gfp_flags & __GFP_ZERO)
                prep_zero_page(page, order, gfp_flags);

and that will cause a warning REGARDLESS of whether the page is a HIGHMEM 
page or not.

And the fact is, passing in GFP_ZERO from the SLUB code is a bug 
regardless, because it unnecessarily does the dual memset().

So here's a damn big clue:
 - SLUB does its own GFP_ZERO handling
 - so passing GFP_ZERO down to the page allocator is a f*cking bug
 - and this has NOTHING what-so-ever to do with GFP_HIGHMEM or even 
   whether the warning is "valid" or not - it's a bug even if the warning 
   had never happened.

So stop blathering, and just admit that this was buggy. It was also 
fundamentally fragile to leave GFP_ZERO around when it was known to not be 
valid at that point (exactly because GFP_ZERO was handled by the caller).

		Linus
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