linux-kernel - Re: [PATCH] add __GFP_ZERO to GFP_LEVEL

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Date:	Tue, 24 Jul 2007 08:48:52 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Christoph Lameter <clameter@....com>
Cc:	Mel Gorman <mel@...net.ie>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Daniel Phillips <phillips@...gle.com>,
	linux-mm <linux-mm@...ck.org>
Subject: Re: [PATCH] add __GFP_ZERO to GFP_LEVEL_MASK

On Tue, 2007-07-24 at 08:01 +0200, Peter Zijlstra wrote:

> Then we can either fixup the slab allocators to mask out __GFP_ZERO, or
> do something like the below.
> 
> Personally I like the consistency of adding __GFP_ZERO here (removes
> this odd exception) and just masking it in the sl[aou]b thingies.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
---
 include/linux/gfp.h |    2 +-
 mm/slab.c           |    4 +++-
 mm/slob.c           |    2 ++
 mm/slub.c           |    4 +++-
 4 files changed, 9 insertions(+), 3 deletions(-)

Index: linux-2.6-2/include/linux/gfp.h
===================================================================
--- linux-2.6-2.orig/include/linux/gfp.h
+++ linux-2.6-2/include/linux/gfp.h
@@ -56,7 +56,7 @@ struct vm_area_struct;
 /* if you forget to add the bitmask here kernel will crash, period */
 #define GFP_LEVEL_MASK (__GFP_WAIT|__GFP_HIGH|__GFP_IO|__GFP_FS| \
 			__GFP_COLD|__GFP_NOWARN|__GFP_REPEAT| \
-			__GFP_NOFAIL|__GFP_NORETRY|__GFP_COMP| \
+			__GFP_NOFAIL|__GFP_NORETRY|__GFP_COMP|__GFP_ZERO| \
 			__GFP_NOMEMALLOC|__GFP_HARDWALL|__GFP_THISNODE| \
 			__GFP_MOVABLE)
 
Index: linux-2.6-2/mm/slab.c
===================================================================
--- linux-2.6-2.orig/mm/slab.c
+++ linux-2.6-2/mm/slab.c
@@ -2739,11 +2739,13 @@ static int cache_grow(struct kmem_cache 
 	gfp_t local_flags;
 	struct kmem_list3 *l3;
 
+	flags &= ~__GFP_ZERO; /* slab has its own object zeroing */
+
 	/*
 	 * Be lazy and only check for valid flags here,  keeping it out of the
 	 * critical path in kmem_cache_alloc().
 	 */
-	BUG_ON(flags & ~(GFP_DMA | __GFP_ZERO | GFP_LEVEL_MASK));
+	BUG_ON(flags & ~(GFP_DMA | GFP_LEVEL_MASK));
 
 	local_flags = (flags & GFP_LEVEL_MASK);
 	/* Take the l3 list lock to change the colour_next on this node */
Index: linux-2.6-2/mm/slob.c
===================================================================
--- linux-2.6-2.orig/mm/slob.c
+++ linux-2.6-2/mm/slob.c
@@ -223,6 +223,8 @@ static void *slob_new_page(gfp_t gfp, in
 {
 	void *page;
 
+	gfp &= ~__GFP_ZERO; /* slob has its own object zeroing */
+
 #ifdef CONFIG_NUMA
 	if (node != -1)
 		page = alloc_pages_node(node, gfp, order);
Index: linux-2.6-2/mm/slub.c
===================================================================
--- linux-2.6-2.orig/mm/slub.c
+++ linux-2.6-2/mm/slub.c
@@ -1078,7 +1078,9 @@ static struct page *new_slab(struct kmem
 	void *last;
 	void *p;
 
-	BUG_ON(flags & ~(GFP_DMA | __GFP_ZERO | GFP_LEVEL_MASK));
+	flags &= ~__GFP_ZERO; /* slab has its own object zeroing */
+
+	BUG_ON(flags & ~(GFP_DMA | GFP_LEVEL_MASK));
 
 	if (flags & __GFP_WAIT)
 		local_irq_enable();



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