linux-kernel - Re: tipc_init(), WARNING: at arch/x86/mm/highmem_32.c:52, [2.6.24-rc4-git5: Reported regressions from 2.6.23]

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Date:	Sat, 8 Dec 2007 09:47:49 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Matt Mackall <mpm@...enic.com>
cc:	Ingo Molnar <mingo@...e.hu>, "Rafael J. Wysocki" <rjw@...k.pl>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <clameter@....com>
Subject: Re: tipc_init(), WARNING: at arch/x86/mm/highmem_32.c:52,
 [2.6.24-rc4-git5: Reported regressions from 2.6.23]



On Sat, 8 Dec 2007, Matt Mackall wrote:
> 
> Avoid calling page allocator with __GFP_ZERO, as we might be in atomic
> context and this will make thing unhappy on highmem systems. Instead,
> manually zero allocations from the page allocator.

I think this is fine, but didn't we fix the warning already? Calling page 
allocators with __GFP_ZERO should be fine, as long as __GFP_HIGHMEM isn't 
set, and slab/slub/slob/kmalloc cannot use GFP_HIGHMEM *anyway*. 

But I'll apply it anyway, because it looks "obviously correct" from the 
standpoint that the _other_��slob user already clears the end result 
explicitly later on, and we simply should never pass down __GFP_ZERO to 
the actual page allocator.

On that note, shouldn't we also do this for slub.c? Christoph?

			Linus

---
 mm/slub.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index b9f37cb..9c1d9f3 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1468,6 +1468,9 @@ static void *__slab_alloc(struct kmem_cache *s,
 	void **object;
 	struct page *new;
 
+	/* We handle __GFP_ZERO in the caller */
+	gfpflags &= ~__GFP_ZERO;
+
 	if (!c->page)
 		goto new_slab;
 
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