Re: [Bug #13319] Page allocation failures with b43 and p54usb

[Pekka Enberg]

On Wed, 2009-06-10 at 18:49 +0300, Pekka Enberg wrote:
> > On Wed, 2009-06-10 at 18:44 +0300, Pekka Enberg wrote:
> > 
> > > Aha, SLUB thinks the minimum order for 4096 is 1. I guess you have
> > > CONFIG_SLUB_DEBUG enabled? If yes, something like to following should
> > > help. Christoph, are you okay with this patch?

On Wed, 2009-06-10 at 17:52 +0200, Johannes Berg wrote:
> > +	if ((size + MAX_DEBUG_SIZE) >= PAGE_SIZE)
> 
> && size <= PAGE_SIZE
> 
> ? Or is this a path that only happens for small allocations?
> 
> > +		s->flags &= ~(SLAB_POISON|SLAB_RED_ZONE|SLAB_STORE_USER);
> > +
> >  	if (!calculate_sizes(s, -1))
> >  		goto error;

Although something like this would probably be even nicer.

			Pekka

diff --git a/mm/slub.c b/mm/slub.c
index 65ffda5..a4206ef 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2334,6 +2334,16 @@ static int calculate_sizes(struct kmem_cache *s, int forced_order)
 
 }
 
+#define MAX_DEBUG_SIZE (3 * sizeof(void *) + 2 * sizeof(struct track))
+
+static bool must_disable_debug(size_t size)
+{
+	/*
+	 * Disable debugging if it increases the minimum page order.
+	 */
+	return get_order(size + MAX_DEBUG_SIZE) > get_order(size);
+}
+
 static int kmem_cache_open(struct kmem_cache *s, gfp_t gfpflags,
 		const char *name, size_t size,
 		size_t align, unsigned long flags,
@@ -2346,6 +2356,9 @@ static int kmem_cache_open(struct kmem_cache *s, gfp_t gfpflags,
 	s->align = align;
 	s->flags = kmem_cache_flags(size, flags, name, ctor);
 
+	if (must_disable_debug(size))
+		s->flags &= ~(SLAB_POISON|SLAB_RED_ZONE|SLAB_STORE_USER);
+
 	if (!calculate_sizes(s, -1))
 		goto error;
 


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