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

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Message-ID: <alpine.LFD.1.00.0803281116460.14670@woody.linux-foundation.org>
Date:	Fri, 28 Mar 2008 11:20:52 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Pekka Enberg <penberg@...helsinki.fi>
cc:	Christoph Lameter <clameter@....com>,
	"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 Fri, 28 Mar 2008, Pekka Enberg wrote:
> 
> On Fri, Mar 28, 2008 at 7:27 PM, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
> >  So the *last* thing we want to do is to clear GFP_ZERO in multiple subtle
> >  places based on new random code being added. We want to clear it at the
> >  top level, so that no other code never ever even has to _think_ about it!
> 
> We are clearing it in one place, just before calling alloc_pages.

BUT THAT IS TOTALLY IRRELEVANT.

We're not clearing it in kmalloc_large()!

What's so hard to understand?

> [Yes, it's hard to spot, it's in new_slab() where we call
> allocate_slab().] I'm okay with moving it to top level but I don't see
> how that fixes any of the bugs mentioned here.

That stupid clearing in new_slab() is totally and utterly irrelevant (in 
addition to the fact that it's hard to spot).

The point was never new_slab(). So why do you even mention it?

The code in question is __slab_alloc(). It did *not* clear it correctly 
before its uses (__slab_alloc -> kmalloc_large -> __get_free_pages).

			Linus
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